1
Q
What role does the heart play in the body?
A
Pumps blood to all parts of the body.
2
Q
What is the function of tissue fluids?
A
Exchange dissolved materials with the blood.
3
Q
What do the lungs do in the circulatory process?
A
Supply blood with oxygen and clear excess carbon dioxide.
4
Q
What is the central nervous system (CNS) comprised of?
A
The brain and spinal cord.
5
Q
What constitutes the peripheral nervous system (PNS)?
A
Nerves originating in the brain and spinal cord that travel to peripheral parts of the body.
6
Q
What are the main components of the circulatory system?
A
The heart, arteries, veins, and capillaries
7
Q
What does the circulatory system transport?
A
Oxygen, nutrients, and hormones to every cell of the body
carbon dioxide, waste chemicals, and heat away
8
Q
What type of system does blood circulate through?
A
A closed system of tubes including lung and tissue capillaries, heart, arteries, and veins
9
Q
What are capillaries?
A
Intricate networks of extremely small blood vessels
10
Q
What is the role of capillaries in the lungs?
A
They surround tiny air sacs (alveoli) for gas exchange
11
Q
What is the primary function of the heart?
A
To propel blood throughout the circulatory system
12
Q
Describe the size and composition of the heart.
A
About the size of a closed fist, hollow, made up almost entirely of muscle tissue
13
Q
Where is the heart located?
A
In the front and center of the chest cavity between the lungs, behind the breastbone
14
Q
What separates the two halves of the heart?
A
A wall of tissue called a septum
15
Q
What are the two main chambers of the heart?
A
Atrium (upper chamber) and ventricle (lower chamber)
Atrium
Ventricles
(The A points up and the V points down)
16
Q
Which chamber of the heart does most of the pumping?
A
The ventricles
17
Q
What is the function of arteries?
A
To carry blood from the heart to the capillaries
Arteries / away
18
Q
What is the function of veins?
A
To return blood from the capillaries to the heart
19
Q
What are the two circuits of the circulatory system?
A
Pulmonary circuit and systemic circuit
20
Q
What is the primary function of the pulmonary circuit?
A
To serve the lung capillaries
21
Q
What happens to blood as it leaves a muscle or organ capillary?
A
It loses most of its oxygen and is loaded with carbon dioxide
22
Q
What are the names of the main veins in the upper chest?
A
Superior vena cava and inferior vena cava
23
Q
What is the function of the superior vena cava?
A
To receive blood from the upper half of the body
24
Q
What is the function of the inferior vena cava?
A
To receive blood from areas of the body below the diaphragm
25
What is the pathway of blood after entering the right atrium?
It flows through the tricuspid valve into the right ventricle
26
Where does gas transfer take place in the circulatory system?
In the pulmonary capillaries
27
What happens to blood after it has exchanged gases in the lungs?
It returns to the heart via the pulmonary venous system and enters the left atrium
28
What is the function of the mitral valve?
To allow blood to flow from the left atrium into the left ventricle
29
What is the aortic valve's role in the circulatory system?
To pump blood through the main artery (aorta) of the systemic circuit
30
What happens to blood in the systemic circuit?
Oxygen is exchanged for carbon dioxide in the capillaries
31
What is the average volume of blood in the human body?
Approximately five liters
32
What is the primary function of the lung's gas exchange system?
To facilitate the exchange of oxygen and carbon dioxide between the air and blood
33
What is the role of the alveoli in the respiratory system?
They are the sacs where gas exchange occurs
34
What type of blood does the right ventricle of the heart pump into the pulmonary capillaries?
Blood that is low in oxygen and high in carbon dioxide
35
How does hemoglobin function in the blood?
It carries oxygen and forms a loose chemical combination with it
36
What is the relationship between partial pressure of oxygen and hemoglobin's ability to release oxygen?
Hemoglobin gives up oxygen in tissues where the partial pressure of oxygen is lower
37
What forms as carbon dioxide dissolves in the blood?
Acids
38
What role do buffers in the blood play?
They neutralize acids and help carry away carbon dioxide
39
What is plasma?
The colorless, watery portion of blood containing dissolved materials essential to life
40
What is respiration?
The process of exchanging oxygen and carbon dioxide during oxidation
41
Where does gas exchange primarily occur in the body?
Via circulating blood in the lungs and tissues
42
What is the process of moving air in and out of the lungs called?
Ventilation
43
What are the six important phases of respiration?
* Ventilation of the lungs with fresh air
* Exchange of gases between blood and air in lungs
* Transport of gases by blood
* Exchange of gases between blood and tissue fluids
* Exchange of gases between tissue fluids and cells
* Use and production of gases by cells
44
What is the significance of the lung membrane surface area?
It is much larger than skin area, facilitating gas exchange
45
What is the primary function of the respiratory system?
Performs pulmonary ventilation and exchanges oxygen and carbon dioxide
## Footnote
It also warms air and assists in speech production.
46
What structures are included in the upper respiratory tract?
* Nose
* Nasal cavity
* Frontal sinuses
* Maxillary sinuses
* Larynx
* Trachea
## Footnote
The upper respiratory tract filters, moistens, and warms air.
47
What structures are included in the lower respiratory tract?
* Left and right bronchi
* Lungs
## Footnote
The lower respiratory tract is where gas exchange occurs.
48
What is the role of alveoli in the respiratory system?
Site for the exchange of oxygen and carbon dioxide
## Footnote
Alveoli provide about 850 square feet of surface area for gas exchange.
49
How does inspiration occur in the respiratory system?
By elevating the ribs and lowering the diaphragm
## Footnote
This increases lung volume and lowers pressure, allowing air to rush in.
50
What happens during expiration in the respiratory system?
Ribs lower and diaphragm rises, increasing pressure in the lungs
## Footnote
This expels used air from the lungs.
51
What is Boyle's Law in the context of respiration?
Lower pressure in lungs allows fresh air to rush in
## Footnote
It relates to the mechanics of inhalation and exhalation.
52
What are the lungs primarily composed of?
Lobes and millions of alveoli
## Footnote
Alveoli are small expandable air sacs for gas exchange.
53
True or False: The lungs are spongy organs responsible for gas exchange.
True
## Footnote
They are the main components of the respiratory system.
54
What is inspiratory volume?
The volume of air that can be inhaled into the lungs.
55
Define vital capacity.
The volume of air that can be expelled from the lungs after a full inspiration.
56
What is total lung capacity?
The total volume of air that the lungs can hold when filled to capacity.
57
What is expiratory reserve volume?
The volume of air that can be exhaled after a normal exhalation.
58
What is tidal volume?
The volume of air moved in or out of the lungs during a single normal respiratory cycle.
59
What is residual volume?
The amount of air remaining in the lung after the most forceful expiration.
60
What is the average tidal volume for an adult at rest?
About one-half liter.
61
What is the respiratory cycle?
One complete breath consisting of an inspiration and exhalation, including any pause.
62
What is the normal respiratory rate for an adult at rest?
Approximately 12 to 16 breaths per minute.
63
What is the normal range for total lung capacity (TLC)?
Between five and six liters.
64
What is the average vital capacity?
Between four and five liters.
65
How is respiratory minute volume (RMV) calculated?
By multiplying the tidal volume by the respiratory rate.
66
What is the typical RMV at complete rest?
About 6 to 10 liters per minute.
67
Define maximum inspiratory flow rate and maximum expiratory flow rate
The fastest rates at which the body can move gases in and out of the lungs.
68
What is the respiratory quotient (RQ)?
The ratio of carbon dioxide produced to oxygen consumed during cellular processes.
69
What does respiratory dead space refer to?
The part of the respiratory system that has no alveoli, with little or no gas exchange.
70
How much volume does respiratory dead space normally amount to?
Less than 0.2 liter.
71
What happens to air occupying the dead space at the end of expiration?
It is rebreathed in the following inspiration.
72
What is alveolar/capillary gas exchange?
The process of oxygen absorption by blood and carbon dioxide elimination from blood in the alveoli.
73
Fill in the blank: The tidal volume can never exceed the _______.
vital capacity.
74
What is the primary function of the capillary bed in the lungs?
To expose blood to the gas pressures of alveolar air for gas exchange
## Footnote
This process occurs through thin membranes of the air sacs and capillary walls.
75
What happens to the gas pressure of blood when it leaves the lungs?
It is approximately equal to that present in alveolar air.
76
What occurs when arterial blood passes through the capillary network in body tissues?
It equalizes with the gas pressure of the tissues, absorbing oxygen and picking up carbon dioxide.
77
What is the effect of carbon dioxide diffusion from blood into alveolar air?
It lowers the partial pressure of carbon dioxide in alveolar air.
78
What is the typical duration of one complete circulation cycle?
Approximately 20 seconds.
79
How does a diver's activity affect oxygen consumption and carbon dioxide production?
Both increase markedly when a diver is working.
80
What must change to maintain proper blood levels of gases during increased activity?
The respiratory minute volume must change in proportion to oxygen consumption and carbon dioxide output.
81
What activates the central and peripheral chemoreceptors in the body?
Changes in the partial pressure of oxygen (ppO2) and carbon dioxide (ppCO2) in arterial circulation.
82
Where are the most important chemoreceptors located?
In the carotid bodies in the neck and aortic bodies near the heart.
83
What does the chemoreceptor in the carotid artery respond to?
ppCO2 in the blood.
84
What reflex is initiated by the chemoreceptor in the aorta?
The aortic body reflex.
85
What determines the amount of work a person can do?
The maximum pumping capacity of the heart and respiratory system.
86
How is oxygen consumption defined?
As a measure of energy expenditure linked to ventilation and carbon dioxide production.
87
What is the relationship between oxygen consumption rate and depth?
Oxygen consumption rates are not depth dependent.
88
Fill in the blank: Surface RMV can be approximated by multiplying the oxygen consumption rate by _______.
25.
89
What happens to the inhalation rate of gas as depth increases?
It increases due to increased gas density.
90
At 33 fsw, how does inhalation change compared to the surface?
Inhalation rate remains 20 l/min, but gas density increases inhalation to approximately 40 standard l/min.
91
What is the effect of exertion on carbon dioxide production?
It depends only on the level of exertion and is independent of depth.
92
What are common physiological problems for divers related to respiratory processes?
Inadequate supply of oxygen or inadequate removal of carbon dioxide.
93
How does depth affect the diver's awareness of physiological changes?
Divers are only marginally aware of small changes due to physiological reserves.
94
What is the impact of the extra work of breathing at depth?
It reduces the diver's ability to do heavy work.
95
What is hypoxia?
An abnormal deficiency of oxygen in the arterial blood
## Footnote
Severe hypoxia can impede normal cell function and result in cell death, with the brain being the most vulnerable organ.
96
What determines if the amount of oxygen in a breathing medium is adequate?
The partial pressure of oxygen (ppO,)
## Footnote
Air contains approximately 21 percent oxygen, providing a ppO, of about 0.21 ata at the surface.
97
At what partial pressure of oxygen does hypoxic symptoms begin?
Below 0.16 ata
98
At what ppO, do most individuals become helpless due to hypoxia?
0.11 ata
99
What can cause permanent brain damage and death in relation to hypoxia?
Levels below 0.10 ata of ppO,
100
What are some causes of hypoxia for divers?
Causes include:
* Improper line up of breathing gases
* Blockage of fresh gas injection orifice
* Failure of oxygen addition valve
* Inadequate purging of breathing bags
* Blockage of air passages
* Collapse of the lung due to pneumothorax
* Paralysis of respiratory muscles
* Pulmonary edema
* Carbon monoxide poisoning
* Breathholding
101
What is pulmonary edema?
Accumulation of fluid in the lung tissues
## Footnote
It can occur due to various factors including diving in cold water while overhydrated.
102
What is the effect of carbon monoxide on oxygen transport?
It interferes with oxygen transport by hemoglobin and blocks oxygen utilization at the cellular level.
103
What happens during a breathhold?
The partial pressure of oxygen in the lung falls progressively as the body consumes oxygen.
104
What are some symptoms of hypoxia?
Symptoms include:
* Loss of judgment
* Lack of concentration
* Lack of muscle control
105
What is hypoxia?
A condition where there is insufficient oxygen reaching the tissues
## Footnote
Brain tissue is the most susceptible to hypoxia effects
106
What are some symptoms of hypoxia?
Symptoms include:
* Inability to perform delicate tasks
* Drowsiness
* Weakness
* Agitation
* Euphoria
* Loss of consciousness
107
Why is hypoxia considered a serious hazard for divers?
It can occur unexpectedly without reliable warning signs
108
What happens to pulse rate and blood pressure during hypoxia?
Both pulse rate and blood pressure increase as the body attempts to circulate more blood
109
What is cyanosis?
A general blueness of the lips, nail beds, and skin that may occur with hypoxia
110
How can a diver recognize the onset of hypoxia?
Very few people can recognize the mental effects of hypoxia in time to take corrective action
111
What is the treatment for severe hypoxia in divers?
Basic first aid and 100% oxygen must be administered promptly
112
What should be done if a diver suffering from hypoxia is breathing?
He should be given gas with adequate oxygen content before breathing stops
113
What are the prevention strategies for hypoxia?
Strategies include:
* Ensuring proper gas content in supplies
* Strict gas analysis
* Monitoring oxygen sensors closely
114
What is hypercapnia?
An abnormally high level of carbon dioxide in the blood and body tissues
115
What causes hypercapnia in diving operations?
Causes include:
* Excess carbon dioxide in air supplies
* Inadequate ventilation
* Failure of absorbent canisters
* Inadequate lung ventilation
116
What is flow resistance in the context of hypercapnia?
Resistance arising from the flow of dense gas through equipment and the diver's airways
117
At what depths do symptoms of hypercapnia usually become apparent?
Symptoms usually appear at depths deeper than 120 FSW on air or deeper than 850 FSW on helium-oxygen
118
What is static lung load?
Static lung load is the result of breathing gas being supplied at a different pressure than the hydrostatic pressure surrounding the lungs.
119
How does the position of the diver affect static lung load?
When swimming horizontally, the regulator diaphragm is lower than the mouth, causing a slight positive pressure. When flipped onto the back, the diaphragm is shallower than the lungs, leading to a slightly negative pressure.
120
What is the effect of static lung loading in closed and semi-closed circuit underwater breathing apparatus?
In closed and semi-closed circuits, exhalation is easier than inhalation when the diaphragm is shallower than the lungs, and vice versa when the diaphragm is below the lungs.
121
What condition can static lung load contribute to?
Static lung load is an important contributor to hypercapnia.
122
What symptoms may excessive breathing resistance cause?
Shortness of breath, sensation of labored breathing (dyspnea) without an increase in blood carbon dioxide level.
123
What activates when there is excessive breathing resistance?
Activation of pressure and stretch receptors in the airways, lungs, and chest wall.
124
What are the symptoms of hypercapnia?
* Increased breathing rate
* Shortness of breath (dyspnea)
* Confusion or feeling of euphoria
* Inability to concentrate
* Increased sweating
* Drowsiness
* Headache
* Loss of consciousness
* Convulsions
125
What physiological response occurs due to an increasing level of carbon dioxide in the blood?
The respiratory center increases the breathing rate and volume.
126
What factors may mask changes caused by excess carbon dioxide during diving?
* Water temperature
* Work rate
* Increased breathing resistance
* Elevated ppO2 in the breathing mixture
127
What may occur if the ppO2 is above 0.5 ata?
Shortness of breath associated with excess carbon dioxide may not be prominent and may go unnoticed.
128
What can happen to a diver who loses consciousness due to excess carbon dioxide?
They generally revives rapidly when given fresh air and usually feels normal within 15 minutes.
129
What are some common after effects of hypercapnia?
* Headache
* Nausea
* Dizziness
130
How does excess carbon dioxide affect brain arteries?
Excess carbon dioxide dilates the arteries of the brain, which may explain headaches associated with carbon dioxide intoxication.
131
What is believed to increase the likelihood of decompression sickness during a dive?
Excess carbon dioxide.
132
What is the relationship between nitrogen narcosis and hypercapnia?
The effects of nitrogen narcosis and hypercapnia are additive, and narcosis may mask the warning signs of carbon dioxide intoxication.
133
How is hypercapnia treated?
* Decreasing the level of exertion
* Increasing helmet and lung ventilation
* Shifting to an alternate breathing source or aborting the dive
134
What is the first sign of hypercapnia?
Unconsciousness
## Footnote
Hypercapnia may cause unconsciousness, but by itself will not injure the brain permanently.
135
Why is it important to rule out hypoxia before hypercapnia?
Significant potential for brain damage in hypoxia
136
How is hypercapnia prevented in surface-supplied diving?
By ensuring gas supplies do not contain excess carbon dioxide and ventilating the helmet frequently with fresh gas
## Footnote
Maintaining proper manifold pressure is also crucial.
137
What gas mixtures should be used for dives deeper than 150 fsw?
Helium-oxygen mixtures
## Footnote
These mixtures help reduce breathing resistance.
138
Define asphyxia.
A condition where breathing stops and both hypoxia and hypercapnia occur simultaneously.
139
What are common causes of asphyxia in SCUBA diving?
Running out of air, equipment failure, airway obstruction, paralysis of respiratory muscles, respiratory center failure
140
What is the difference between drowning and near drowning?
Drowning is fluid-induced asphyxia; near drowning is when a victim is successfully resuscitated after drowning.
141
List causes of drowning.
* Overexertion
* Panic
* Inability to cope with rough water
* Exhaustion
* Effects of cold water or heat loss
142
What can cause drowning in a hard-hat diving rig?
Helmet not properly secured or being trapped in a head-down position with a water leak
143
What are signs and symptoms of near drowning?
* Unconsciousness
* Increased respiratory rate
* Shortness of breath
* Coughing with frothy or blood-tinged sputum
* Cyanosis
* Distress
144
What is the first step in treating unconscious drowning victims in water?
Open/maintain an airway
145
Fill in the blank: If the victim is not breathing, provide _______.
5 rescue breaths
146
What should be done if there is no response to rescue breaths in a drowning victim?
Assume the victim is in cardiac arrest
147
What is the ABC method of resuscitation?
* Airway = Maintain an open airway
* Breathing = Check for breathing; if not breathing, give 2 rescue breaths
* Circulation = Check pulse; if absent, initiate chest compressions
148
What should be done after a drowning victim is moved to a stable platform?
Place the patient in the supine position and utilize the ABC method of resuscitation
149
What should be done if a patient vomits after resuscitation?
Be prepared to turn the patient on their side and suction their airway
150
What should a patient be placed on after resuscitation?
100% oxygen and an AED should be placed on the chest
151
What is the mildest case of drowning likely to require?
Post rescue hospitalization and possibly intensive care.
152
How can drowning be best prevented?
By thoroughly training divers in safe diving practices and carefully selecting diving personnel.
153
What can overconfidence in divers lead to?
A feeling of false security that might lead to dangerous risks.
154
How long can most people hold their breath without training?
Approximately 1 minute.
155
What physiological change signals the desire to breathe during a breathhold?
Increasing levels of carbon dioxide in the arterial blood.
156
What is a common cause of breathholding accidents in swimming pools?
The oxygen partial pressure falling below the level necessary to maintain consciousness.
157
True or False: Extended breathholding after hyperventilation is safe.
False.
158
What happens to air in the lungs during descent?
It is compressed, raising the oxygen partial pressure.
159
What can occur if the oxygen partial pressure falls below 0.10 ata during ascent?
Unconsciousness may result.
160
What is hyperventilation?
Breathing more than is necessary to keep the body's carbon dioxide tensions at proper level.
161
What can trigger involuntary hyperventilation?
Fear during stressful situations or equipment changes.
162
List symptoms of involuntary hyperventilation.
* Dizziness
* Tingling of the extremities
* Spasm of small muscles in hands and feet
* Weakness
* Headaches
* Numbness
* Faintness
* Blurring of vision.
163
What should be encouraged for victims of hyperventilation?
Relaxation and slowing of breathing rates.
164
What does 'overbreathing the rig' refer to?
An episode of acute hypercapnia when a diver works beyond what their UBA can support.
165
What can happen when a diver experiences acute hypercapnia?
Severe shortness of breath and uncontrollable hyperventilation may occur.
166
What is laryngospasm?
A spasm of the muscles of the larynx that can occur if water is inhaled.
167
What must divers recognize about their UBA?
That all UBA have limitations.
168
What should divers do if they encounter excessive breathing resistance?
Slow or stop the pace of work until respiratory comfort is achieved.
169
What does carbon monoxide poisoning involve?
The presence of carbon monoxide in the blood and tissues due to normal metabolism.
170
What occurs when levels of carbon monoxide in the blood and tissues rise above normal values?
Carbon monoxide poisoning
## Footnote
This condition is due to the presence of carbon monoxide in the diver's gas supply.
171
What are the effects of carbon monoxide on hemoglobin?
Blocks hemoglobin's ability to deliver oxygen and poisons cellular metabolism directly
172
What is a common cause of carbon monoxide poisoning in divers?
Compressor's intake being too close to the exhaust of an internal combustion engine or malfunction of an oil lubricated compressor
173
What concentration of carbon monoxide can prove fatal?
0.002 ata (2,000 ppm, or 0.2%)
174
List the symptoms of carbon monoxide poisoning when toxicity develops gradually.
* Headache
* Dizziness
* Confusion
* Nausea
* Vomiting
* Tightness across the forehead
175
True or False: Victims of carbon monoxide poisoning may not be aware of symptoms before losing consciousness.
True
176
What happens to the symptoms of carbon monoxide poisoning during ascent?
The full effect of carbon monoxide poisoning is felt as the partial pressure of oxygen diminishes
177
What is the immediate treatment for carbon monoxide poisoning?
Getting the diver to fresh air and seeking medical attention
178
What is the definitive treatment of choice for carbon monoxide poisoning?
Hyperbaric oxygen therapy
179
What should be done when carbon monoxide poisoning is suspected?
Isolate the suspect breathing gas source and forward gas samples for analysis
180
What is barotrauma?
Damage to body tissues from the mechanical effects of pressure
181
When does barotrauma most frequently occur?
During descent
182
What is barotrauma during ascent called?
Reverse squeeze
183
List the five prerequisites for squeeze to occur during descent.
* There must be a gas-filled space
* The gas-filled space must have rigid walls
184
What must be enclosed to prevent damage during pressure changes?
The gas-filled space must be enclosed
## Footnote
If gas or liquid can freely enter the space as the gas volume changes, no damage will occur.
185
What type of membrane is required in the space for pressure compensation?
Lining membrane with an arterial blood supply and venous drainage
## Footnote
This allows blood to be forced into the space to compensate for the change in pressure.
186
What is the most common type of barotrauma?
Middle ear squeeze
187
What seals off the outer ear canal from the middle ear space?
The eardrum
188
How does air pressure reach the inner surface of the eardrum?
Through the passage of air via the eustachian tube
189
What happens when the eustachian tube is blocked by mucus?
The middle ear meets the requirements for barotrauma
## Footnote
This includes gas-filled space, rigid walls, enclosed space, and penetrating blood vessels.
190
What occurs as a diver descends and water pressure increases?
The eardrum bows inward and compresses the middle ear gas
191
What creates a relative vacuum in the middle ear space?
Middle ear pressure becomes lower than external water pressure
192
What is the hallmark symptom of middle ear squeeze?
Sharp pain caused by stretching of the eardrum
193
What should a diver do to relieve pain from middle ear squeeze?
Stop descending and ascend a few feet
194
What happens if descent continues despite pain from middle ear squeeze?
The eardrum may rupture
195
What is caloric vertigo?
A sensation of spinning caused by cold water stimulating the balance mechanism of the inner ear
196
What can cause caloric vertigo aside from eardrum rupture?
Cold or warm water entering one ear and not the other
197
What increases the likelihood of middle ear squeeze while diving?
Diving with a partially blocked eustachian tube
198
What can happen if a diver performs a forceful Valsalva maneuver during descent?
It can result in alternobaric vertigo or barotrauma to the inner ear
199
What symptoms may a diver experience upon surfacing after a middle ear squeeze?
Pain, fullness in the ear, hearing loss, or mild vertigo
200
What is the treatment for middle ear squeeze?
Decongestants, pain medication, and cessation of diving until healed
201
What are sinuses lined with?
Mucous membrane
202
What is the Frontal Sinus?
A cavity located in the frontal bone of the skull, above the nasal cavity
## Footnote
It is one of the paranasal sinuses.
203
What is the Orbit?
The bony cavity that houses the eye
## Footnote
It provides protection and structural support for the eye.
204
What is the function of the Nasal Cavity?
It filters, warms, and humidifies the air we breathe
## Footnote
It also plays a role in olfaction (sense of smell).
205
What is the Nasal Septum?
The structure that divides the nasal cavity into two nostrils
## Footnote
It is composed of bone and cartilage.
206
What is the Maxillary Sinus?
The largest of the paranasal sinuses located in the maxilla (upper jaw)
## Footnote
It is involved in reducing the weight of the skull and providing resonance to the voice.
207
What is Sinus Squeeze?
A condition where negative air pressure develops in the sinuses, causing pain
## Footnote
This can happen during diving when external pressure exceeds internal pressure.
208
How can divers prevent Sinus Squeeze?
By avoiding dives with nasal congestion and equalizing pressure during descent
## Footnote
Techniques include swallowing or blowing against a pinched nose.
209
What is Tooth Squeeze (Barodontalgia)?
Pain caused by gas pockets in teeth during pressure changes
## Footnote
It can occur with poorly fitted fillings or dental decay.
210
What can lead to External Ear Squeeze?
Wearing ear plugs, having an infected ear, or wearing a tight-fitting hood
## Footnote
This condition arises due to pressure differences in the ear canal.
211
What happens during Thoracic (Lung) Squeeze?
Lungs become compressed, leading to negative pressure and potential injury
## Footnote
This can result in fluid entering the lung alveoli.
212
What should be avoided to prevent lung squeeze during diving?
Breath-hold diving beyond controlled limits
## Footnote
Controlled training and shallow depths are recommended.
213
What is Face or Body Squeeze?
Pressure imbalance caused by SCUBA masks or exposure suits
## Footnote
It can lead to discomfort or hemorrhage in the skin.
214
What is Inner Ear Barotrauma?
Damage to the inner ear due to pressure imbalances affecting the middle ear
## Footnote
The inner ear itself does not contain gas and cannot be squeezed.
215
What are the three bones in the middle ear?
Malleus, incus, stapes
## Footnote
Commonly referred to as hammer, anvil, and stirrup respectively.
216
What is the function of the cochlea?
Hearing sense organ
## Footnote
Damage to the cochlea results in hearing loss and tinnitus.
217
What does the vestibular apparatus do?
Balance organ
## Footnote
Damage leads to vertigo and unsteadiness.
218
How does the malleus transmit sound vibrations?
Connects to the eardrum and transmits vibrations to the incus.
219
What is the role of the stapes?
Relays sound vibrations to the inner ear through the oval window.
220
What is the function of the round window?
Relieves pressure waves in the inner ear.
221
What can happen if middle ear pressure is not equalized during descent?
Inward bulge of the eardrum transmitted to the oval window, potentially causing round window rupture.
222
What is inner ear barotrauma?
Condition caused by rupture of the round or oval windows leading to inner ear fluid spilling into the middle ear.
223
What are the primary symptoms of inner ear barotrauma?
Persistent vertigo and hearing loss.
224
Define vertigo.
False sensation of motion.
225
What sensations may accompany vertigo in inner ear barotrauma?
Nausea, vomiting, loss of balance, incoordination, nystagmus.
226
How may hearing loss present in inner ear barotrauma?
Fluctuating intensity, distorted sounds, and ringing or roaring.
227
When do symptoms of inner ear barotrauma typically appear?
Abruptly during descent or after surfacing.
228
What activities can increase cerebrospinal fluid pressure post-dive?
Lifting heavy weights or having a bowel movement.
229
What should be done for suspected inner ear barotrauma?
Refer to an ear, nose and throat (ENT) physician.
230
What treatments are available for inner ear barotrauma?
Bed rest with head elevation to exploratory surgery.
231
True or False: The oval window is more commonly ruptured than the round window.
False.
232
Fill in the blank: The fluid in the inner ear is called _______.
perilymph.
233
What may occur if pressure waves induced in the inner ear lead to disruption?
Inner ear barotrauma without perilymph fistula.
234
What is the condition that requires recompression treatment after diving?
Decompression sickness or arterial gas embolism
235
What position should a diver be placed in during recompression treatment?
Head up position
236
What should be avoided when the diver is breathing oxygen on the built-in breathing system mask?
Excessive positive or negative pressure
237
What is the condition called when frequent oscillations in middle ear pressure cause transient vertigo?
Alternobaric vertigo of descent
238
What maneuver often precedes the onset of alternobaric vertigo?
Valsalva maneuver
239
What happens to the eardrum during middle ear overpressure?
It bows outward causing pain
240
What is the result of a significant overpressure in the middle ear?
Eardrum rupture
241
What condition occurs when one side of the middle ear is overpressurized during ascent?
Alternobaric vertigo of ascent
242
What can increased pressure in the middle ear lead to in terms of facial muscle function?
Facial baroparesis
243
How long is overpressure generally necessary for facial baroparesis symptoms to occur?
10 to 30 minutes
244
What condition is characterized by structural damage to the inner ear during ascent?
Inner ear barotrauma of ascent
245
What should divers with a cold or inability to equalize their ears be cautious of during ascent?
Increased likelihood of reverse middle ear squeeze
246
What should not be performed during ascent to avoid increasing middle ear pressure?
Valsalva maneuver
247
What should a diver do if they experience pain in the ear or vertigo during ascent?
Halt the ascent and descend a few feet
248
What condition results from gas trapped within the sinus cavity during ascent?
Reverse sinus squeeze
249
What is a potential effect of overpressure in the maxillary sinus?
Numbness of the lower eyelid, upper lip, side of the nose, and cheek
250
What can cause gastrointestinal distention in divers during ascent?
Gas expansion in the stomach or intestines
251
What is aerophagia?
Swallowing air, which can lead to gas pockets in the system.
## Footnote
Gas pockets usually exit through the mouth or anus, and if not, distention may occur.
252
What are the recommendations to avoid intestinal gas expansion during diving?
* Do not dive with an upset stomach or bowel.
* Avoid eating gas-producing foods.
* Avoid steep, head-down angles during descent.
## Footnote
These practices minimize air swallowing.
253
What are the consequences of pulmonary overinflation?
Rupture of the alveolar lining, pulmonary interstitial emphysema, arterial gas embolism, mediastinal emphysema, pneumothorax, and subcutaneous emphysema.
## Footnote
These conditions arise from leaking gas into pulmonary tissues.
254
What causes arterial gas embolism?
Gas entering the arterial circulation, potentially leading to fatal outcomes.
## Footnote
This can occur due to excessive pressure in the lungs.
255
What is tension pneumothorax?
Accumulation of gas between the lung and chest wall that continues without venting.
## Footnote
It can be a serious condition resulting from pulmonary overinflation.
256
What can cause pulmonary overinflation during ascent?
* Voluntary or involuntary breath-holding.
* Localized pulmonary obstructions (e.g., asthma).
## Footnote
Thick secretions from pneumonia or severe colds can also cause air trapping.
257
What is interstitial emphysema?
A condition where air collects in lung tissues after alveolus rupture, usually asymptomatic unless further air distribution occurs.
## Footnote
It is the first step in pulmonary overinflation syndromes.
258
What are the main causes of alveolar rupture during diving?
* Expansion of trapped gas during ascent.
* Pressing the purge button on a single-hose regulator while breathing.
## Footnote
These actions can lead to excessive pressure inside the lung.
259
True or False: Pulmonary overinflation syndromes are unrelated to barotrauma.
False.
## Footnote
They are caused by barotrauma related to gas expansion in the lungs.
260
What is arterial gas embolism (AGE)?
Obstruction of blood flow caused by gas bubbles entering the arterial circulation
## Footnote
Can lead to death if not promptly relieved
261
What causes arterial gas embolism (AGE)?
Expansion of gas taken into the lungs while breathing under pressure and held in the lungs during ascent
## Footnote
Can occur due to voluntary breath-holding, blocked air passages, or over pressurization of breathing gas
262
What is the most common cause of arterial gas embolism?
Exhaustion of air supply and the need for an emergency ascent
263
List three symptoms of arterial gas embolism (AGE).
* Unconsciousness
* Paralysis
* Numbness
## Footnote
Other symptoms include weakness, dizziness, and vision abnormalities
264
What treatment is recommended for arterial gas embolism?
* Basic first aid (ABC)
* 100 percent oxygen
* Immediate recompression
## Footnote
See Volume 5 for more specific information regarding treatment
265
How can the risk of arterial gas embolism be reduced?
* Intensive training in diving physics and physiology
* Never interrupt breathing during ascent
* Exhale continuously during emergency ascent
## Footnote
Particular attention must be given to SCUBA divers
266
Fill in the blank: A diver must exhale continuously while making an _______.
[emergency ascent]
267
True or False: A diver should report any illness to the Diving Supervisor before a dive.
True
268
What symptoms may accompany arterial gas embolism?
* Bloody sputum
* Hearing abnormalities
* Tremors
## Footnote
Symptoms of subcutaneous/mediastinal emphysema, pneumothorax, and/or pneumopericardium may also be present
269
What is a key factor in executing an emergency ascent properly?
The rate of exhalation must match the rate of ascent
270
What is mediastinal emphysema also known as?
Pneumomediastinum
## Footnote
Mediastinal emphysema occurs when gas is forced through torn lung tissue into the mediastinal tissues.
271
What is subcutaneous emphysema?
Condition when gas migrates into subcutaneous tissues of the neck
## Footnote
It follows mediastinal emphysema.
272
What are the causes of mediastinal and subcutaneous emphysema?
* Over inflation of the lung
* Breath holding during ascent
* Positive pressure breathing
* Drown proofing exercises
* Cough during surface swimming
## Footnote
These activities can lead to gas being forced into the mediastinum.
273
What are the mild symptoms of mediastinal and subcutaneous emphysema?
Often unnoticed by the diver
## Footnote
Mild cases may not present any noticeable symptoms.
274
What are some severe symptoms of mediastinal and subcutaneous emphysema?
* Mild to moderate pain under the breastbone
* Pain radiating to the shoulder or back
* Feeling of fullness around the neck
* Difficulty swallowing
* Change in voice pitch
* Swelling of the neck
* Crepitation near the windpipe
## Footnote
Severe cases can significantly impact the diver's experience.
275
What should be done if mediastinal or subcutaneous emphysema is suspected?
Prompt referral to medical personnel
## Footnote
This is necessary to rule out arterial gas embolism or pneumothorax, which require more aggressive treatment.
276
What is the initial treatment for mild symptoms of mediastinal or subcutaneous emphysema?
Breathing 100 percent oxygen at the surface
## Footnote
This treatment helps in managing mild cases effectively.
277
What may be beneficial for severe symptoms of mediastinal or subcutaneous emphysema?
Shallow recompression
## Footnote
This should only be done under the recommendation of an Undersea Medical Officer.
278
True or False: Mediastinal emphysema is a prerequisite for subcutaneous emphysema.
True
## Footnote
Mediastinal emphysema must occur before subcutaneous emphysema can develop.
279
What is a pneumothorax?
Air trapped in the pleural space between the lung and the chest wall.
## Footnote
Visual representation can be found in Figure 3-14.
280
What causes a pneumothorax?
Occurs when the lung surface ruptures, allowing air to spill into the pleural space.
## Footnote
Can result from severe chest trauma or overpressurization of the lung.
281
What is a simple pneumothorax?
A one-time leakage of air from the lung into the chest that partially collapses the lung.
## Footnote
Typically improves over time as the air is reabsorbed.
282
What is a tension pneumothorax?
A condition where air enters but does not exit the pleural space, leading to increased pressure that can collapse the lung.
## Footnote
Visual representation can be found in Figure 3-15.
283
What happens during a tension pneumothorax?
The expanding gas exerts pressure on the lung and heart, leading to potential complete lung collapse.
## Footnote
If uncorrected, it impairs respiration and circulation.
284
How can a simple pneumothorax become a tension pneumothorax?
By the expansion of the gas pocket during ascent, causing mounting tension and lung collapse.
## Footnote
No ball valve mechanism is present, but the outcome is similar.
285
What are the symptoms of a pneumothorax?
Sudden sharp chest pain, shortness of breath, labored breathing, rapid heart rate, weak pulse, and anxiety.
## Footnote
Normal chest movements are affected.
286
What are the strategies for preventing mediastinal and subcutaneous emphysema?
Breathe normally during ascent and exhale continuously if emergency ascent is required.
## Footnote
These strategies are identical to those for preventing arterial gas embolism.
287
What should be done if decompression is required after a pneumothorax?
Use the appropriate air table and do not exceed an ascent rate of 1 foot per minute.
## Footnote
Delay in ascent should be included in bottom time when choosing the proper decompression table.
288
Fill in the blank: A pneumothorax can lead to respiratory distress due to _______.
partially collapsed lung.
289
What happens to respiration on the affected side in tension pneumothorax?
Respiration may be reduced on the affected side and breath sounds may be difficult to hear with a stethoscope.
290
How do the symptoms of tension pneumothorax compare to simple pneumothorax?
Symptoms are similar but become progressively more intense over time.
291
What happens to blood pressure and arterial oxygen partial pressure in tension pneumothorax?
Blood pressure falls along with the arterial oxygen partial pressure.
292
What is a visible symptom of tension pneumothorax?
Cyanosis (a bluish discoloration) of the skin appears.
293
What can occur if tension pneumothorax is left untreated?
Shock and death will ensue.
294
What must a diver believed to be suffering from pneumothorax be examined for?
Possible co-existence of arterial gas embolism.
295
What is the typical outcome for a small pneumothorax (less than 15%)?
It normally will improve with time as air is reabsorbed spontaneously.
296
What treatment is recommended for a mild pneumothorax?
Breathing 100 percent oxygen.
297
What may require active treatment in cases of pneumothorax?
A larger pneumothorax.
298
What procedures may be necessary for cases of pneumothorax that demonstrate cardio-respiratory compromise?
Insertion of a chest tube, largebore intravenous (IV) catheter, or other device designed to remove intrathoracic gas.
299
Who should insert devices for decompressing the thoracic cavity?
Only personnel trained in their use.
300
What should be suspected if a diver's condition deteriorates rapidly during ascent?
A tension pneumothorax.
301
What is the procedure for treating a tension pneumothorax found during ascent?
Recompress to depth of relief until the thoracic cavity can be properly vented.
302
Should a pneumothorax prevent immediate recompression therapy?
No, it should not prevent immediate recompression therapy.
303
What strategies are recommended to prevent pneumothorax?
Breathe normally during ascent and exhale continuously if performing an emergency ascent.
304
What are the indirect effects of pressure on the human body caused by?
Changes in the partial pressure of individual gases in the diver's breathing medium.
305
What is nitrogen narcosis?
A state of euphoria and exhilaration that occurs at a nitrogen partial pressure greater than approximately 4 ata.
306
What causes nitrogen narcosis?
Breathing nitrogen at high partial pressures has a narcotic effect on the central nervous system.
307
At what nitrogen partial pressure does narcosis begin?
Approximately 4 ata.
308
What are symptoms of nitrogen narcosis?
* Loss of judgment or skill
* A false feeling of well-being
* Lack of concern for job or safety
* Apparent stupidity
* Inappropriate laughter
* Tingling and vague numbness of the lips, gums, and legs.
309
What is the greatest hazard of nitrogen narcosis?
Disregard for personal safety.
310
What is the treatment for nitrogen narcosis?
Bring the diver to a shallower depth where effects are not felt.
311
Is there a hangover associated with nitrogen narcosis?
No, there is no hangover.
312
How can experienced divers prevent nitrogen narcosis?
By being familiar with its effects and maintaining a strong conscious effort during the dive.
313
What depth may experienced divers perform air dives without serious difficulty?
As deep as 200 fsw.
314
What can occur as nitrogen partial pressure increases beyond 4 ata?
Narcotic effects increase in severity.
315
What gas is widely used in mixed-gas diving to prevent narcosis?
Helium
## Footnote
Helium has not demonstrated narcotic effects at any depth tested by the U.S. Navy.
316
At what depth should helium-oxygen mixtures be considered for diving?
Excess of 150 fsw
317
What is oxygen toxicity?
Toxicity to the body caused by exposure to a partial pressure of oxygen above normal levels
318
What are the two types of oxygen toxicity experienced by divers?
* Pulmonary oxygen toxicity
* Central nervous system (CNS) oxygen toxicity
319
What partial pressure can lead to pulmonary oxygen toxicity?
Exceeds 0.5 ata
320
What are the symptoms of pulmonary oxygen toxicity?
* Burning sensation on inspiration
* Pain on inspiration
321
What can happen to unconscious patients receiving oxygen treatments?
They may experience permanent lung damage or pneumonia
322
How can tolerance to pulmonary oxygen toxicity be extended?
By periodically interrupting oxygen exposure with low oxygen partial pressure
323
What is the threshold for CNS oxygen toxicity in wet divers?
Exceeds 1.3 ata
324
What is the threshold for CNS oxygen toxicity in dry divers?
Exceeds 2.4 ata
325
What factors influence the risk of CNS oxygen toxicity?
* Individual susceptibility
* CO2 retention
* Exercise
* Immersion in water
* Depth
* Intermittent exposure
326
How does hypercapnia affect the risk of CNS toxicity?
It increases brain blood flow and consequently brain oxygen levels
327
Why must exposure limits be more conservative for exercising divers?
Because exercise increases the risk of CNS toxicity
328
What effect does immersion in water have on the risk of CNS toxicity?
It greatly increases the risk
329
What is the effect of increasing depth on CNS toxicity risk?
Increased risk, even with unchanged ppO2
330
What is one technique to reduce the risk of CNS toxicity during high ppO2 exposure?
Periodic interruption with low ppO2 exposure
331
What diving systems generally require the lowest oxygen exposure limits?
Closed and semi-closed circuit rebreathing systems
332
What is the most serious direct consequence of oxygen toxicity?
Convulsions
## Footnote
Convulsions are the most alarming symptom and indicate severe CNS oxygen toxicity.
333
What mnemonic can help remember the early symptoms of CNS oxygen toxicity?
VENTIDC
## Footnote
Each letter stands for a specific symptom associated with oxygen toxicity.
334
What are the visual symptoms of CNS oxygen toxicity?
* Tunnel vision
* Decrease in peripheral vision
* Blurred vision
335
What does tinnitus refer to in the context of CNS oxygen toxicity?
Any sound perceived by the ears not resulting from an external stimulus
336
List some gastrointestinal symptoms associated with CNS oxygen toxicity.
* Nausea
* Spasmodic vomiting
337
What are the common muscle-related symptoms of CNS oxygen toxicity?
* Twitching
* Tingling in facial muscles, lips, or extremities
338
What type of mental changes can indicate CNS oxygen toxicity?
* Confusion
* Agitation
* Anxiety
339
What symptoms might indicate dizziness due to CNS oxygen toxicity?
* Clumsiness
* Incoordination
* Unusual fatigue
340
What is the tonic phase of a convulsion?
The state where all muscles are stimulated and the body becomes rigid
341
What occurs during the clonic phase of a convulsion?
Random impulses cause violent thrashing and jerking
342
What is the postictal phase following a convulsion?
A period of unconsciousness, followed by semiconsciousness and restlessness
343
What actions should a diver take upon experiencing warning symptoms of oxygen toxicity?
* Inform the Diving Supervisor
* Ascend
* Shift to a breathing mixture with lower oxygen percentage
* Remove the mask in a recompression chamber
344
True or False: Reducing the oxygen partial pressure instantly reverses biochemical changes in the CNS.
False
## Footnote
It may take time for the CNS to recover even after lowering the oxygen levels.
345
What should be done to a diver convulsing underwater?
* Ventilate the UBA with a gas of lower oxygen content
* Keep at depth until convulsion subsides
346
What is the risk associated with ascent during a convulsion?
Risk of an arterial gas embolism (AGE)
347
How should a convulsing diver be managed in a recompression chamber?
* Prevent thrashing against hard objects
* Remove the oxygen mask
* Maintain a clear airway
348
What is the expected recovery time for a diver after an oxygen convulsion?
Full recovery within 24 hours with no lasting effects
349
What is the most serious direct consequence of oxygen toxicity?
Convulsions
## Footnote
Convulsions are the most alarming symptom and indicate severe CNS oxygen toxicity.
350
What mnemonic can help remember the early symptoms of CNS oxygen toxicity?
VENTIDC
## Footnote
Each letter stands for a specific symptom associated with oxygen toxicity.
351
What are the visual symptoms of CNS oxygen toxicity?
* Tunnel vision
* Decrease in peripheral vision
* Blurred vision
352
What does tinnitus refer to in the context of CNS oxygen toxicity?
Any sound perceived by the ears not resulting from an external stimulus
353
List some gastrointestinal symptoms associated with CNS oxygen toxicity.
* Nausea
* Spasmodic vomiting
354
What are the common muscle-related symptoms of CNS oxygen toxicity?
* Twitching
* Tingling in facial muscles, lips, or extremities
355
What type of mental changes can indicate CNS oxygen toxicity?
* Confusion
* Agitation
* Anxiety
356
What symptoms might indicate dizziness due to CNS oxygen toxicity?
* Clumsiness
* Incoordination
* Unusual fatigue
357
What is the tonic phase of a convulsion?
The state where all muscles are stimulated and the body becomes rigid
358
What occurs during the clonic phase of a convulsion?
Random impulses cause violent thrashing and jerking
359
What is the postictal phase following a convulsion?
A period of unconsciousness, followed by semiconsciousness and restlessness
360
What actions should a diver take upon experiencing warning symptoms of oxygen toxicity?
* Inform the Diving Supervisor
* Ascend
* Shift to a breathing mixture with lower oxygen percentage
* Remove the mask in a recompression chamber
361
True or False: Reducing the oxygen partial pressure instantly reverses biochemical changes in the CNS.
False
## Footnote
It may take time for the CNS to recover even after lowering the oxygen levels.
362
What should be done to a diver convulsing underwater?
* Ventilate the UBA with a gas of lower oxygen content
* Keep at depth until convulsion subsides
363
What is the risk associated with ascent during a convulsion?
Risk of an arterial gas embolism (AGE)
364
How should a convulsing diver be managed in a recompression chamber?
* Prevent thrashing against hard objects
* Remove the oxygen mask
* Maintain a clear airway
365
What is the expected recovery time for a diver after an oxygen convulsion?
Full recovery within 24 hours with no lasting effects
366
What does CNS oxygen toxicity not increase due to?
Convulsion
## Footnote
Divers may notice warning symptoms during subsequent exposures to oxygen.
367
What is important for preventing CNS oxygen toxicity?
Sensible precautions
## Footnote
Precautions include ensuring breathing apparatus is in good order, observing depth-time limits, avoiding excessive exertion, and heeding abnormal symptoms.
368
What can extend exposure time to high oxygen partial pressures significantly?
Periodic air breaks
## Footnote
Air breaks are routinely incorporated into recompression treatment tables and some decompression tables.
369
What happens if a diver ascends too fast?
Excess gas forms bubbles
## Footnote
These bubbles produce mechanical and biochemical effects leading to decompression sickness.
370
What gas does the human body absorb at depth?
Nitrogen or helium
## Footnote
The absorbed gas can separate from solution upon rapid ascent.
371
According to Henry's Law, what is the relationship between gas solubility and partial pressure?
Almost directly proportional
## Footnote
If one liter of inert gas is absorbed at one atmosphere, then two liters are absorbed at two atmospheres, etc.
372
What is the process of taking up more inert gas called?
Absorption or saturation
373
What is the process of giving up inert gas called?
Elimination or desaturation
374
What occurs when a diver ascends abruptly from depth?
Bubbles may form in arterial blood or in fast tissue
## Footnote
This can happen even though the body as a whole is far from saturation.
375
What is the alveolar nitrogen pressure in the lungs at 100 fsw?
About 3.2 ata
## Footnote
This is calculated as 0.8 × 4 ata.
376
What is the driving force for nitrogen molecules to move by diffusion?
Partial pressure gradient
## Footnote
The gradient at 100 fsw is 2.4 ata (3.2 minus 0.8).
377
What happens to nitrogen molecules as blood passes through the alveolar capillaries?
They move from the alveolar air into the blood.
378
What happens by the time the blood leaves the lungs at 100 fsw?
It reaches equilibrium with the new alveolar nitrogen pressure.
379
What is the partial pressure of nitrogen at 100 fsw?
3.2 ata
380
How much nitrogen does the blood carry compared to the tissue volume?
The volume of blood in a tissue is relatively small compared to the volume of the tissue
381
What happens to nitrogen molecules when blood reaches the tissues?
Nitrogen molecules move from the blood into the tissues until equilibrium is reached
382
When the blood leaves the tissue, what is the nitrogen pressure in the venous blood?
Equal to the new tissue nitrogen pressure
383
What occurs when blood goes through the lungs after leaving the tissue?
It reaches equilibrium at 3.2 ata
384
What happens to nitrogen exchange as tissue nitrogen pressure rises?
The blood-tissue gradient decreases, slowing the rate of nitrogen exchange
385
What is the effect of blood supply on nitrogen saturation in tissues?
Tissues with a large blood supply approach complete saturation more rapidly than those with a poor blood supply
386
How does the solubility of nitrogen in fat compare to water?
Nitrogen is about five times as soluble in fat as in water
387
Which type of tissue requires more nitrogen and time to saturate?
Fatty tissues
388
At what pressure do all tissues reach saturation when a diver is at 100 fsw?
3.2 ata of nitrogen
389
What is the nitrogen content of a diver's body at the surface compared to 100 fsw?
About one liter at the surface and about four liters at 100 fsw
390
True or False: The process of nitrogen saturation requires different lengths of time depending on nitrogen pressure.
False
391
If a diver is taken to 33 fsw instead of 100 fsw, how does the saturation time compare?
It would take just as long to saturate completely
392
What happens to nitrogen delivery to tissues at a lower depth?
The amount of nitrogen delivered by each round of blood circulation would be smaller
393
What is the process of desaturation?
The reverse of saturation where nitrogen diffuses from tissues to blood and then to lungs
394
Fill in the blank: Tissues with poor blood supply or large gas capacity will lag behind and may remain partially _______ after others have cleared.
saturated
395
What determines the rate at which tissues desaturate?
The amount of blood that flows through them each minute
396
What occurs when the spinal cord is involved in decompression sickness?
Paralysis and/or loss of feeling
397
What symptoms can bubbles in the inner ear cause?
Hearing loss and vertigo
398
What symptoms can bubbles in the lungs cause?
Coughing, shortness of breath, and hypoxia
399
What is a symptom of decompression sickness that is not attributable to a specific organ system?
Unusual fatigue
400
What factors can lead to decompression sickness before reaching the surface?
Arduous dives or omitted decompression
401
What type of dives are generally associated with longer latencies for decompression sickness?
Long, shallow dives
402
What is the primary treatment for decompression sickness?
Recompression
403
What is the purpose of recompression in treating decompression sickness?
Reduce the size of bubbles and supply extra oxygen to hypoxic tissues
404
What is the recommended environment for treatment of decompression sickness?
Recompression chamber
405
What can be done if a recompression chamber cannot be reached in time?
Recompression in water following specified procedures
406
What may cause some cases of decompression sickness even when proper procedures are followed?
Individual susceptibility or unusual conditions
407
What is the average core temperature of the human body?
98.6°F (37°C)
408
What major consideration arises from exposure to various water temperatures during dives?
Thermal problems
409
What may limit bottom time more than exposure to increased oxygen partial pressures?
Diver's intolerance to heat or cold
410
What is the effect of a diver's thermal status on inert gas uptake?
Affects the rate of uptake and elimination
411
What is hypothermia?
A lowering of the core temperature of the body
412
What water temperature is required to keep an unprotected, resting man at a stable temperature?
Approximately 91°F (33°C)
413
What can increase the risk of hypothermia during diving?
Movement in cold water creating turbulence
414
What causes the core temperature to be maintained or increased in warm water?
Increased blood flow into the limbs during exercise and continual movement
## Footnote
The limbs resemble the internal body core rather than the insulating superficial layer.
415
What are symptoms of mild hypothermia?
Uncontrolled shivering, slurred speech, imbalance, poor judgment
## Footnote
Mild symptoms indicate the body's initial response to cold.
416
What are symptoms of severe hypothermia?
Loss of shivering, impaired mental status, irregular heartbeat, very shallow pulse or respirations
## Footnote
Severe cases represent a medical emergency.
417
What happens at extremely low temperatures or with prolonged immersion?
Body heat loss reaches a point at which death occurs.
418
List the corresponding symptoms for a core temperature temperature of 95°F.
* Sporadic shivering suppressed by voluntary movements
* Gross shivering in bouts
* Further increase in oxygen consumption
* Uncontrollable shivering
419
What are the treatment measures for mild hypothermia?
Passive and active rewarming measures until the victim is sweating
## Footnote
Passive measures include removing wet clothing and wrapping in a blanket.
420
What is the correct action to take for severe hypothermia?
Avoid exercise, keep the victim lying down, initiate only passive rewarming, transport to medical facility
## Footnote
Active rewarming should not be instituted.
421
True or False: CPR should be initiated on a severely hypothermic diver immediately.
False
## Footnote
CPR should only be initiated if it is determined that the heart has stopped or is in ventricular fibrillation.
422
What is the body's natural ability to tolerate cold environments dependent on?
Natural insulation and heat regulation
## Footnote
Temperature is not uniform throughout the body.
423
What happens to blood flow in the extremities when initially put into very cold water?
Vasoconstriction occurs and blood flow is reduced to preserve body heat.
424
Fill in the blank: Much of the heat loss in the trunk area is transferred by _______.
[physical conduction].
425
What is a key factor in the heat loss from the body in moderately cold water?
Most of the heat lost is from the trunk, not the limbs.
426
How can hypothermia be insidious during diving?
It can cause problems without the diver being aware of it.
427
What should a diver wear based on water temperature and expected bottom time?
Appropriate thermal protection.
428
What is the primary role of acclimatization in diving?
To prevent hypothermia
429
What factors contribute to preventing hypothermia in divers?
* Acclimatization
* Adequate hydration
* Experience
* Common sense
430
What is significant about heat loss through the respiratory tract during deep diving?
Inhaled gases require more energy to heat due to increased density at depths
431
What can cause caloric vertigo in divers?
* Water entering one ear canal
* Tight fitting wet suit hood
* Obstruction by wax
432
How does caloric vertigo manifest?
Causes disorientation and nausea
433
What physiological response occurs due to the diving reflex?
* Bradycardia
* Constriction of peripheral blood vessels
434
What is uncontrolled hyperventilation?
Rapid and uncontrolled breathing that impairs coordination
435
What is hyperthermia?
A rise in the core temperature of the body
436
At what air or water temperature should hyperthermia be considered a risk?
* Air temperature exceeds 90°F
* Water temperature above 82°F
437
What temperature indicates a diver has developed hyperthermia?
Core temperature rises 1.8°F (1°C) above normal (98.6°F, 37°C)
438
What are the core temperature limits for divers?
Should not exceed 102.2°F (39°C)
439
What factors contribute to the risk of hyperthermia in divers?
* High water temperatures
* Protective garments
* Rate of work
* Duration of the dive
440
What are some signs of hyperthermia?
* High breathing rate
* Feeling hot and uncomfortable
* Low urine output
* Fatigue
* Nausea
441
What are severe symptoms of hyperthermia?
* Disorientation
* Loss of consciousness
* Seizures
442
What is the first step in treating hyperthermia?
Cooling the victim to reduce core temperature
443
What method is recommended for cooling a victim of mild to moderate hyperthermia?
* Remove clothing
* Spray with lukewarm-to-cool water
* Fan the victim
444
What should be avoided when treating hyperthermia?
Whole body immersion in cold water or packing in ice
445
What is the purpose of oral fluid replacement in hyperthermia treatment?
To ensure the victim can urinate pale to clear urine
446
What should be done if the symptoms of hyperthermia do not improve?
Transport the victim to a medical treatment facility
447
What is severe hyperthermia?
A medical emergency requiring immediate cooling measures and transport to a medical facility.
## Footnote
Intravenous fluids should be administered during transport.
448
What factors play a role in preventing hyperthermia?
Acclimatization, adequate hydration, experience, and common sense.
## Footnote
Shelter from the sun and minimal clothing are also important.
449
What is acclimatization?
The process where repeated exposures to heat reduce the rise in core temperature.
## Footnote
At least 5 consecutive days are needed for increased tolerance to heat.
450
How long do the benefits of acclimatization last after stopping exposure to warm water?
3 to 5 days.
## Footnote
Fully acclimatized divers can still develop hyperthermia.
451
What is High Pressure Nervous Syndrome (HPNS)?
A derangement of central nervous system function during deep helium-oxygen dives.
## Footnote
Symptoms include nausea, fine tremor, imbalance, and confusion.
452
What depths are associated with the onset of HPNS?
First noted between 400 and 500 fsw.
## Footnote
Severity is depth and compression rate dependent.
453
What is compression arthralgia?
Pain in the joints experienced during compression on deep dives.
## Footnote
Commonly affects shoulders, knees, wrists, and hips.
454
How can compression pain be distinguished from decompression sickness pain?
Compression pain is present before decompression starts and does not increase with decreasing depth.
## Footnote
Improvement is noted during saturation depth.
455
What is dehydration?
An excessive loss of water from body tissues, disrupting electrolyte balance.
## Footnote
Particularly concerning for divers in tropical zones.
456
What causes dehydration in divers?
Inadequate fluid intake and/or excessive perspiration in hot climates.
## Footnote
Immersion diuresis also contributes by increasing urination.
457
What is immersion diuresis?
A condition where increased central blood volume during immersion leads to increased urination.
## Footnote
This results in steady loss of water from the body.
458
What symptoms may a diver experience after immersion due to dehydration?
Lightheadedness, fatigue, reduced alertness, and decreased exercise tolerance.
## Footnote
These are caused by drops in blood pressure and blood volume shifts.
459
What is the effect of immersion on blood volume distribution?
Blood is translocated from the legs to the chest, increasing central blood volume.
## Footnote
This can lead to a reflex triggering increased urination.
460
What increases the risk of decompression sickness in divers?
Dehydration
## Footnote
Divers should monitor fluid intake and urine output to stay hydrated.
461
What are the primary symptoms of immersion pulmonary edema?
* Cough
* Shortness of breath
* Blood-tinged mucus
462
What should be done for a diver with immersion pulmonary edema?
Place on surface oxygen and transport to a medical facility
## Footnote
Symptoms usually resolve with bed rest and 100% oxygen.
463
What is the carotid sinus reflex?
A decrease in heart rate and possible loss of consciousness due to external pressure on the carotid artery
## Footnote
Tight-fitting suits can activate this reflex.
464
What is middle ear oxygen absorption syndrome?
Negative pressure in the middle ear following a long oxygen dive
## Footnote
Caused by absorption of high percentage oxygen by middle ear tissues.
465
What symptoms indicate middle ear oxygen absorption syndrome?
* Mild discomfort
* Hearing loss
* Sense of pressure
* Moist, cracking sensation
466
How can one treat middle ear oxygen absorption syndrome?
Equalizing the pressure using a Valsalva maneuver or other techniques
## Footnote
Consult a Diving Medical Technician if symptoms persist.
467
What factors influence the amount of damage from an underwater explosion?
* Size of the explosion
* Distance from the site
* Type of explosive
* Depth of water
* Type of bottom
468
What is immersion pulmonary edema?
A condition where fluid leaks out of the circulation system and accumulates in the lungs' interstitial tissues and alveoli.
## Footnote
The exact mechanism is not known but is related to an increase in central blood volume during immersion.
469
What factors contribute to immersion pulmonary edema?
* Immersion in cold water
* Negative pressure breathing
* Overhydration pre-dive
* Heavy exercise
## Footnote
These factors enhance the increase in central blood volume with immersion.
470
What are the primary symptoms of immersion pulmonary edema?
* Cough
* Shortness of breath
* Blood-tinged mucus
## Footnote
Chest pain is notably absent.
471
How should a diver with immersion pulmonary edema be treated?
They should be placed on surface oxygen and transported to a medical treatment facility.
## Footnote
Symptoms usually resolve spontaneously with bed rest and 100% oxygen within 24 hours.
472
What activates the carotid sinus reflex?
External pressure on the carotid artery from a tight-fitting neck dam, wet suit, or dry suit.
## Footnote
This can cause a decrease in heart rate and possible loss of consciousness.
473
What happens if the eustachian tube does not open during middle ear oxygen absorption syndrome?
A negative pressure relative to ambient may result in the middle ear cavity.
## Footnote
This condition is usually minor and easily eliminated.
474
What additional condition can be present in the middle ear due to differential pressure?
Serous otitis media.
## Footnote
This may occur alongside middle ear oxygen absorption syndrome.
475
What is the Valsalva maneuver used for?
Equalizing the pressure in the middle ear
## Footnote
The Valsalva maneuver is a technique that can help relieve symptoms of Middle Ear Oxygen Absorption Syndrome.
476
What should be done if symptoms of Middle Ear Oxygen Absorption Syndrome persist?
Consult a Diving Medical Technician or Diving Medical Officer
## Footnote
Persistent symptoms may require professional medical evaluation and treatment.
477
What complication differentiates underwater trauma from surface trauma?
Loss of the diver's gas supply and decompression obligation
## Footnote
Underwater trauma can complicate the management of injuries due to these unique factors.
478
What is the first priority when treating an injured diver who is trapped?
Ensure sufficient breathing gas is available
## Footnote
Stabilizing the injury comes after securing breathing gas.
479
What needs to be considered if an injured diver has a great decompression obligation?
Stabilize the injury until sufficient decompression can be accomplished
## Footnote
Managing decompression obligations is critical to prevent further complications.
480
What parts of the human body are most affected by underwater shock waves?
Air spaces within the body
## Footnote
Tissues lining air spaces can experience violent forces due to shock waves.
481
What is otitis externa commonly known as?
Swimmer's ear.
482
What is the first symptom of otitis externa?
Itching and/or wet feeling in the affected ear.
483
What may occur in severe cases of otitis externa?
Fever.
484
What should a diver do if otitis externa develops?
Discontinue diving and seek treatment from Diving Medical Personnel.
485
What should be done if the eardrum cannot be seen during examination?
Flush the ear canal gently with water, dilute hydrogen peroxide, or sodium bicarbonate solutions.
486
What should never be used to remove cerumen?
Swabs or other instruments.
487
What happens to local lymph nodes during otitis externa?
They may enlarge, causing painful jaw movement.
488
What is hypoglycemia?
Hypoglycemia is an abnormally low blood sugar (glucose) level.
489
Who commonly experiences episodes of hypoglycemia?
Episodes of hypoglycemia are common in diabetics and pre-diabetics, but may also occur in normal individuals.
490
What can cause a reduction in blood sugar levels?
Simply missing a meal tends to reduce blood sugar levels.
491
What dietary behavior may lead to hypoglycemia in healthy individuals?
Not eating frequently can lead to some degree of hypoglycemia in otherwise healthy individuals.
492
What effect does severe exercise on an empty stomach have?
Severe exercise on an empty stomach may bring on symptoms of hypoglycemia even in healthy individuals.
493
List some symptoms of hypoglycemia.
* Unusual hunger
* Excessive sweating
* Numbness
* Chills
* Headache
* Trembling
* Dizziness
* Confusion
* Incoordination
* Anxiety
* Loss of consciousness (in severe cases)
494
How can hypoglycemia be diagnosed?
Giving sugar by mouth relieves the symptoms promptly and proves the diagnosis.
495
What should be done if a victim of hypoglycemia is unconscious?
Glucose should be given intravenously.
496
What increases the possibility of hypoglycemia during diving operations?
Personnel have a tendency to skip meals or eat haphazardly during long, drawn out diving operations.
497
What dietary advice is given to divers prior to long, cold dives?
Divers should be encouraged to load up on carbohydrates.
498
What is the general guideline for medications and diving?
There are no hard and fast rules; medications should be evaluated on a case-by-case basis.
499
Which types of medications generally do not restrict diving?
* Topical medications
* Antibiotics
* Birth control medication
* Decongestants that do not cause drowsiness
500
Who should be consulted regarding medications that may preclude diving?
Diving medical personnel should be consulted.
Dive Rev 7a
flashcards
Decks in class (4)
# Cards
