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FHB Exam 2 > Respiratory > Flashcards

Respiratory Flashcards

1
Q

What are the main functions of the respiratory system?

A

1) Gas Exchange
2) Barrier function
3) Metabolic Function
4) Host defense

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2
Q

What are the components of the upper airways?

A

Nose, pharynx, glottis and vocal cords

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3
Q

What are the components of the lower airways?

A

Trachea, broncheal tree, alveoli

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4
Q

What major event takes place in the upper airways?

A

Inspired air is humidified and warmed to body temperature

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5
Q

How much does the nose contribute to total air flow resistance?

A

50%

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6
Q

What role do the epiglottis and arytenoids play in the respiratory system?

A

They prevent food and liquid from entering the lower respiratory tract

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7
Q

Describe the process of a cricothyroidotomy

A

An emergency procedure used to establish an open airway. An incision is made on the cricothyroid membrane in order to allow air to pass into the trachea

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8
Q

Describe the pleural surfaces

A

The visceral pleura lies against the lung surface and the parietal pleura lies against the chest wall.
Fluid between the pleura allows the lung to slide smoothly during expansion and contraction

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9
Q

What is a pneumothorax?

A

Air in the pleural space

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10
Q

What is a pleural effusion?

A

Fluid in the pleural space

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11
Q

What is the carina?

A

The division at the end of the trachea into two main stem bronchi

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12
Q

What defines functional anatomic units of the lung?

A

Bronchopulmonary segments are sections of the lung the function independently from the other sections. Segments can be removed in order to prevent the spread of pathologies

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13
Q

Describe the changes in the composition of the airway wall as the airways decrease in size?

A

Large conducting airways contain cartilage and mucous glands, but no alveoli. Small conducting airways have smooth muscle and no alveoli or mucous glands. Alveoli have very thin walls with capillaries.

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14
Q

How many generations of conducting airways are there?

A

About 16 generations of airways do not partake in gas exchange. These conducting airways contain 150mL “anatomical dead space”

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15
Q

What are the respiratory units made up of?

A

Respiratory bronchioles, alveolar ducts and alveoli

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16
Q

Describe the size of the lower airways in terms of length, volume and surface area.

A

The lower airways are only about 5 mm long, but make up 2500mL of air and have a surface area of 70 m^2

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17
Q

What types of cells make up alveoli?

A

Type I cells: the primary site for gas exchange, 95-98% of the surface area
Type II cells: Produce surfactant, 2-4% of the surface area

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18
Q

True or false: Alveoli share basement membranes with capillary endothelia

A

True. Enhances gas transport by holding the membranes 1-2 micrometers from each other

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19
Q

What is surface tension?

A

Large attractive forces between water molecules prevent other molecules from coming between them. Objects heavier than water are able to float.

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20
Q

What role does surface tension play in the alveoli?

A

The attractive forces between the water molecules is greater than the attractive forces between water and air
Surface tension resists stretching of the alveoli, and creates the tendency for recoil after expansion

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21
Q

Without surfactant, what would happen to the alveoli?

A

They would collapse because surface tension is so high

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22
Q

What is Laplace’s law?

A

The pressure in an alveoli is directly proportional to 2*surface tension, and inversely proportional to the radius of the bubble.

Small bubbles will generate larger pressures, and thus collapse.
Large bubbles will become over distended

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23
Q

What s surfactant?

A

A lipoprotein produced by type II alveolar cells that reduces alveolar surface tension, and stabilizes alveoli.

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24
Q

Is surface tension more or less reduced by surfactant in small alveoli compared to large alveoli?

A

Surfactant reduces surface tension more in small alveoli because there s more surfactant per area

This allows for pressure to be equal in differently sized alveoli

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25
Q

How does surface tension affect compliance and work of the lung?

A

Decreasing surface tension increases compliance and reduces the work required to expand the lung

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26
Q

What is interdependence?

A

Alveoli do not collapse because they are mechanically tethered together. The tendency for one alveoli to collapse is opposed by the traction exerted by the surrounding alveoli

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27
Q

What is collateral ventilation?

A

Connections between alveoli (pores of Kohn, channels of lambert, and channels of martin) allow for constricted/collapsed alveoli to be filled from neighboring alveoli

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28
Q

What are the two vascular systems of the lung?

A

Bronchial circulation and pulmonary circulation

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29
Q

Where does the blood from the bronchial circulation end up?

A

1/3 returns to the right atrium

2/3 drains into the pulmonary circulation (mixes with oxygenated blood)

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30
Q

How does the capillary volume of the pulmonary circulation change between rest and exercise?

A

Increases from 70 mL to 200 mL

recruitment and distension

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31
Q

Describe the deposition of inhaled material in the respiratory system

A

Large particles impact in the nasopharynx
Medium particles “sediment” in the small airways
Small particles can diffuse into the alveoli

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32
Q

What are the components of the mucociliary clearance system?

A

Mucus layer, periciliary fluid and cilia

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33
Q

What is the function of the mucociliary clearance system?

A

Transport particles inhaled and deposited onto the bronchi/small airways back out of the system

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34
Q

What is the primary reason that air flows in/out of alveoli?

A

Pressure gradients between the alveolar pressure and the atmospheric pressure

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35
Q

What is Boyle’s law?

A

The volume of a gas is inversely proportional to the pressure exerted by the gas
P1V1 = P2V2

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36
Q

What are the muscles involved with inspiration?

A

Primary: Diaphragm and External Intercostals
Accessory: sternocleidomastoid, scalenes

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37
Q

Describe the motion of the rib cage in response to stimulated external intercostal muscles

A

The ribs move up and out to enlarge the thoracic cavity.

Bucket handle analogy

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38
Q

What type of breathing requires the use of the accessory inspiratory muscles?

A

Forceful inspiration (i.e. during exercise) requires the neck muscles to raise the sternum and elevate the top two ribs

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39
Q

True or false: Expiration is an active process

A

False: Expiration is mostly passive. Active expiration occurs during exercise and utilizes the abdominal muscles and the internal intercostal muscles.

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40
Q

Tidal Volume

A

Volume breathed during quiet breathing

500 mL

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41
Q

Inspiratory reserve volume

A

Volume that you can inspire in addition to the tidal volume; maximal inhalation
3000 mL

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42
Q

Expiratory reserve volume

A

Volume you can force out during exhalation

1200 mL

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43
Q

Residual volume

A

Volume that you cannot breath out; air left in lung after forced exhalation
1200 mL

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44
Q

What is the difference between a lung volume and a lung capacity?

A

Capacities are calculated from volumes measured with a spirometer

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45
Q

Inspiratory Capacity

A

The total possible air inhaled (TV + IRV)

3500 mL

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46
Q

Functional residual capacity

A

The “resting volume” of the lung, air in lung after exhalation during quiet breathing
2400 mL

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47
Q

Vital Capacity

A

The volume of air exhaled from max inhalation to max exhalation
4600 mL

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48
Q

Total Lung Capacity

A

Total volume of air that can be in the lung
TLC = IRV + TV + ERV + RV = VC + RV
5800 mL

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49
Q

Which lung volumes/capacities cannot be measured with a spirometer?

A

Residual volume, functional residual capacity and total lung capacity
* RV cannot be measured, and FRC and TLC include RV, and thus cannot be calculated

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50
Q

Describe the two methods for measuring RV, FRC and TLC

A

1) Helium dilution: calculates TLC by allowing lungs to equilibrate with a helium mixture
2) Body plethysmograph: calculate FRC by placing subject in sealed container and having them breath into device

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51
Q

What is lung compliance?

A

The change in lung volume per 1 cm H20 change in the distending pressure

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52
Q

What is hysteresis?

A

Dissipating energy (different PV paths) between inspiration and expiration. There is different compliance for expiration than inspiration

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53
Q

How does compliance change with volume?

A

Compliance decreases at high volumes because the elastic maximum of the lungs is met

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54
Q

Does surface tension affect the elastic properties of the lung?

A

Yes. Compliance is lower in air filled lungs than in saline filled lungs

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55
Q

What is specific compliance?

A

Compliance normalized for size of lung. This is indicative of the intrinsic elastic properties of the lung

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56
Q

How does compliance change in emphysema and in fibrosis?

A

In emphysema, compliance is increased

In fibrosis, compliance is decreased

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57
Q

In the absence of external forces, what would happen to the volume of the lungs?

A

The lungs would collapse to about 10% of TLC due to elastic recoil. The chest wall prevents this from happening by opposing the lungs

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58
Q

At FRC, what pressures are felt by the respiratory system (chest wall and lung)?

A

Overall, the respiratory system is at zero P
The chest wall experiences a negative relaxation P (wants to expand) and the lungs experience a positive relaxation P (want to collapse)

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59
Q

What is atmospheric pressure in mmHg?

A

Patm = 760 mmHg

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60
Q

What is transpulmonary pressure?

A

The difference between alveolar and pleural pressure

If positive, airways will be held open

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61
Q

What is transmural pressure?

A

Pressure acting across the chest wall

The difference between pleural pressure and the environmental pressure

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62
Q

How is the pressure across the respiratory system calculated?

A

The sum of the transpulmonary and transmural pressures

At rest: zero

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63
Q

What happens if the chest wall is punctured?

A

The pleural pressure equalizes with the atmospheric pressure and the lungs collapse.

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64
Q

What number is used to calculate propensity for laminar/turbulent flow?

A

Reynolds number
R>2000 = turbulent flow
R<2000 = laminar flow

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65
Q

What is the most important determinant of airway resistance?

A

Radius (r^4)

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66
Q

Where does turbulent air flow occur in the normal respiratory system?

A

In the large conducting airways. As cross sectional area increases, laminar flow begins and in the alveoli, air moves via diffusion.

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67
Q

Where is resistance the highest in the respiratory system?

A

In the first 8 airway generations.

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68
Q

What is the definition of conductance?

A

Conductance = 1/R

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69
Q

What factors determine air way resistance?

A

Lung volume and sympathetic stimulation decrease airway resistance

Vagal stimulation, mucus, edema, and smooth muscle contraction increase airway resistance

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70
Q

What is forced vital capacity?

A

The volume of air between a full inspiration and a full expiration

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71
Q

What is FEV1?

A

The volume of air expired in 1s

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72
Q

What does the ratio between FEV1 and FVC represent?

A

FEV1/FVC s a key parameter of lung function

Normally, this ratio is over 75%

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73
Q

Describe the difference in timing between peak expiratory flow rate and peak inspiratory flow rate.

A

PEFR occurs very early in the expiration

PIFR occurs about half way between RV and TLC

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74
Q

What is the difference between the magnitudes of PIFR and PEFR?

A

PIFR is equal to or greater than PEFR

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75
Q

What are the 3 factors determining PIFR?

A

As lung volume increases:
Force of inspiratory muscles decreases
Lung recoil pressure increases
Airway resistance decreases

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76
Q

How does effort impact the expiratory flow rate?

A

The first 20% of flow is effort dependent, therefore increased effort will cause more flow.
The flow rates all converge independent of effort in the effort-independent region at lower lung volumes

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77
Q

Describe the mechanism for flow limitation

A

During exhalation, the pressure in the airway can equal the pressure in the pleura (Equal pressure point).
If the transmural pressure is negative then the airway can be compressed and thus restrict airflow out of the alveoli.

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78
Q

How does a positive transairway (transmural) pressure affect airflow?

A

Positive transairway pressures hold airways open. They are compressed when the transairway pressure in negative.

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79
Q

In a normal lung, why doesnt flow limitation occur?

A

The equal pressure point occurs high enough that the airway has cartilage to hold it open. If lung volume decreases, the equal pressure point moves down and can cause air trapping

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80
Q

Describe the changes in FEV1 and FVC in obstructive and restrictive lung diseases

A

FEV1 is reduced in obstructive lung diseases

FVC is reduced in restrictive lung diseases

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81
Q

What are the two main components of respiratory work?

A

Elastic Work: work to overcome elastic recoil and expand the thoracic cage
Non-elastic work (flow-resistive): work to overcome airflow resistance

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82
Q

How do elastic and nonelastic work change with respiratory rate?

A

Elastic work decreases with increasing respiratory rates

Non elastic work increases with increasing respiratory rates

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83
Q

How does disease affect respiratory work?

A

Fibrosis increases elastic work

COPD increases flow-resistive work

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84
Q

What factors lead to increased work?

A

Reduced compliance
Increased resistance
Decreased elastic recoil

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85
Q

What is Charles’ law?

A

Volume is directly proportional to temperature (Kelvin) at a constant pressure.

86
Q

What is Gay-Lussac’s law

A

Pressure is directly proportional to temperature (Kelvin) at a constant volume

87
Q

What is the combined gas law?

A

P1V1/T1 = P2V2/T2

88
Q

What is the ideal gas law?

A

PV = nRT

89
Q

What is Dalton’s law?

A

The total pressure of a mixture of non-reacting gases is the sum of their individual partial pressures
Ptotal = P1 + P2 + P3 +…..

90
Q

What is Henry’s law?

A

The concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution

91
Q

What is ventilation?

A

The volume of air entering/leaving the respiratory system per minute
V = f x Vt
f= frequency, Vt=tidal volume

92
Q

What are the main components of ambient air?

A

79% N2 (600 mmHg) and 21%O2 (160 mmHg)

93
Q

Why do partial pressures of O2 and N2 change during inspiration?

A

The inspired air is humidified by water vapor with a pressure of 47 mmHg
PiO2 = (Patm - PH2O) x FO2
PH2O = 47mmHg, FO2 = fraction of oxygen = .21

94
Q

What is the alveolar gas equation?

A

P_AO2 = P_IO2 - P_ACO2/R
Alveolar oxygen pressure is equal to the difference between the inspired oxygen pressure and the alveolar CO2 pressure, divided by the respiratory quotient (normally R=0.8)

95
Q

After humidification, what is the total pressure in the trachea?

A

The total pressure remains 760 mmHg

PO2 + PN2 + PH20 = 150 + 563 + 47 = 760 mmHg

96
Q

What factors determine alveolar CO2?

A

Metabolism and rate of elimination

97
Q

Describe the relationship between alveolar CO2 and ventilation and metabolic production

A

Alveolar PCO2 is directly related to metabolism and indirectly related to ventilation (Vx2 –> PCO2/2)

98
Q

Is ventilation evenly distributed throughout the lung in healthy individuals?

A

No. More ventilation occurs at the bottom of the lung

99
Q

How do regional differences in ventilation change with lung volume?

A

At very low lung volumes (RV), the top of the lung has higher ventilation than the bottom because the pressure is too high at the bottom and airways collapse.

100
Q

How is the time constant calculated?

A

t = R * C
R is resistance, C is compliance
If t is large, slow emptying/filling occurs

101
Q

What does a single breath nitrogen test assess?

A

The uniformity of ventilation. This test uses exhaled nitrogen following inhalation of pure oxygen to demonstrate differences in ventilation throughout the lung. Differing time constants are apparent on a plot of volume versus N2 %

102
Q

What is anatomic dead space?

A

The volume of gas filling the conducting airways.

Tidal volume is the sum of the dead space and the alveolar volume

103
Q

What is physiological dead space?

A

Alveoli that are perfused but not ventilated. The gas in these alveoli do not participate in gas exchange.

104
Q

How does the physiological dead space differ in size from the anatomical dead space?

A

Physiological dead space includes the anatomic dead space, so it must be at least as large if not larger

105
Q

What is the most effective way to increase alveolar ventilation?

A

Increasing tidal volume is more effective than increasing respiratory rate

106
Q

What is the average transit time of an erythrocyte through the capillaries?

A

1 second

Very fast, but long enough for full diffusion of O2 to load up RBCs

107
Q

What is Fick’s law?

A

The amount of gas transferred is directly proportional to the area, a diffusion constant, and pressure gradient and indirectly proportional to the thickness of the membrane.

108
Q

What is Graham’s law?

A

The rate of diffusion is directly proportional to the solubility coefficient of the gas and indirectly proportional to the square root of the molecular weight

109
Q

How do the solubility coefficients of O2 and CO2 differ and what does this signify?

A

O2 = 1, CO2 = 22
This means that CO2 diffuses 20x better than O2
This is required for CO2 to diffuse as well as O2 because the pressure gradient for CO2 is much smaller than that of O2

110
Q

Are insoluble gases diffusion or perfusion limited?

A

Insoluble gases are perfusion limited

They rapidly equilibrate, and thus their transfer is limited by the rate of perfusion.

111
Q

Are soluble gases diffusion or perfusion limited?

A

Soluble gases are diffusion limited

Ex: CO, which rapidly binds to Hb and thus does not back up as a pCO to reach an equilibrium

112
Q

Are Oxygen and CO2 diffusion or perfusion limited?

A

Although they are soluble gases, they both bind to Hb with less affinity than CO, so they are normally perfusion limited. In some pathologies, O2 becomes diffusion limited.

113
Q

What is the normal diffusion reserve of the pulmonary capillaries?

A

It is normally over 0.5 seconds

RBCs spend about .75 seconds in the lung and are saturated with O2 in about 0.25 seconds

114
Q

How does exercise affect transit time of RBCs?

A

RBCs move faster and transit time is reduced by 1/3

There is still enough time for O2 saturation in normal individuals

115
Q

At high altitude, why is oxygen uptake impaired?

A

The gradient between alveoli and venous blood is smaller, so diffusion proceeds at a slower rate.
Blood still moves same speed, so the diffusion reserve is decreased.

116
Q

What is the equation for the diffusion capacity of the lung?

A

D_L = V/Palveolar

Normal value: 25 mL/min/mmHg

117
Q

How does the volume of blood in the alveolar capillary network change with exercise?

A

Increases from 70 mL at rest to 150-200 mL during exercise

118
Q

What factors influence lung perfusion?

A

Pulmonary vascular resistance
Gravity
Alveolar pressure
Arterial-venous pressure gradient

119
Q

How does the vascular resistance differ between the pulmonary and systemic circulations?

A

Pulmonary resistance is 10x lower than systemic

120
Q

What are the two mechanisms for PVR decreasing with increased arterial/venous pressures?

A

Recruitment: more routes open up at higher pressure
Distension: vessels expand to accomodate more blood

121
Q

What determines the size of extra-alveolar vessels?

A

The lung volume. Extra-alveolar vessels are pulled open by radial forces of surrounding parenchyma

122
Q

What determines the size of the alveolar vessels?

A

The pressure difference between alveolar pressure ant the pressure within the vessel

123
Q

Explain how PVR changes with changes in lung volume

A

PVR is lowest at FRC
PVR is increased at low volumes (RV) due to narrowed extra-alveolar vessles
PVR is increased at high volumes (TLC) due to stretched capllares

124
Q

How does blood flow distribution through the lung change between rest and exercise?

A

At rest, there is a nearly linear decrease in blood flow from the bottom to the top
During exercise, the difference between the top and bottom becomes less (although both increase)

125
Q

How does hydrostatic pressure affect the distribution of pulmonary blood flow?

A

3 Zones
Zone 1: alveolar pressure is highest, vessels collapsed, not normally present
Zone 2: alveolar pressure is between arterial and venous pressure, vessels are partially collapsed, normally upper 1/3 of the lung
Zone 3: alveolar pressure is lowest ,blood flows continuously

126
Q

What is hypoxic vasoconstriction?

A

The local response to shift blood from hypoxic areas to well ventilated areas

127
Q

What is the Starling equation?

A

Describes fluid balance in the alveolar capillary network

Flux = K[(Piv - Pis) - od(πiv - πis)]
P is hydrostatic pressure
π is osmotic pressure

128
Q

How does pulmonary edema form?

A

The drainage rate through the interstitial space is exceeded which leads to interstitial edema and eventually alveolar lung edema

129
Q

Are volumes of gas and blood in the lungs well matched?

A

No, there is about 43x more gas than blood

130
Q

Are flows of gas and blood in the lungs normally well matched?

A

Yes. Gas flow (alveolar ventilation) and blood flow (pulmonary perfusion) are both around 5000 mL/min

131
Q

What are the two levels that the V/Q ratio can be calculated from?

A

The alveolar level: alveolar ventilation / capillary flow

The whole lung: total alveolar ventilation / cardiac output

132
Q

What is the normal V/Q ratio and what does this mean?

A

V/Q = 0.8

This means perfusion slightly exceeds ventilation normally

133
Q

What does the V/Q ratio tell us about arterial blood?

A

The V/Q ratio tells us the concentration of oxygen in the arterial blood

134
Q

Describe the ventilation and flow in a shunt alveolus

A

The airway is blocked (no ventilation) but blood flow is normal (perfusion unchanged)
The alveolar pO2 and pCO2 will equilibrate with the mixed venous blood.
pO2 = 40 mmHg, pCO2 = 45 mmHg
Decreased V/Q

135
Q

Describe the ventilation and flow in a dead space alveolus

A

Blood flow is blocked, but ventilation is normal
The alveolar gases are in the same concentrations as the inspired air.
pO2 = 150 mmHg, pCO2= 0 mmHg
Increased V/Q

136
Q

If the pCO2 in mixed venous blood is 45 mmHg, what is the maximum alveolar pCO2?

A

45 mmHg

It is impossible to have a higher alveolar pCO2 than the pCO2 in the venous blood

137
Q

True or false: Ventilation is highest and perfusion is lowest at the bottom of the lung

A

False. Both ventilation and perfusion are highest at the bottom of the lung.

138
Q

Moving toward the bottom of the lung, which increases more: flow, or ventilation?

A

Flow increases more than ventilation

Near the top of the lung, V/Q becomes very large

139
Q

Moving from top to bottom of the lung, how do pO2 and pCO2 change?

A

PO2 decreases markedly as you move down the lung

PCO2 increases as you move down the lung

140
Q

Why is alveolar pO2 different than arterial pO2?

A

The arterial pO2 is always lower than the alveolar pO2 because pO2 of the alveoli is highest at the apex of the lung, but the flow is lowest. Most of the blood comes from the relatively poorly oxygenated base of the lung.

141
Q

What is the normal difference between alveolar and arterial pO2?

A

AaDO2 = 15 mmHg

142
Q

How is AaDO2 calculated?

A

Using the alveolar gas equation, ideal alveolar pO2 is calculated, and then the arterial pO2 is subtracted from it

143
Q

What is the definition of hypoxemia?

A

Arterial PO2 < 80 mmHg

144
Q

How does hypoventilation change AaDO2?

A

AaDO2 is not affected by hypoventilation

Gas exchange is still normal

145
Q

What 2 factors determine alveolar PO2?

A

Metabolic demand: The rate of removal of oxygen from the blood
Alveolar ventilation: The rate of replenishment of O2

146
Q

What happens to alveolar pO2 and pCO2 due to hypoventilation?

A

pO2 decreases and pCO2 increases

147
Q

Will administration of additional O2 change arterial pO2 during hypoventilation?

A

Yes. Gas transfer is normal, so a larger gradient will improve O2 supply

148
Q

How is AaDO2 affected by diffusion limitation?

A

AaDO2 increases because arterial pO2 decreases, but alveolar pO2 stays normal

149
Q

What parameters change to cause diffusion limitation?

A

Decreased surface area or increased alveolar thickness

Fick’s law

150
Q

Will administration of additional O2 change arterial pO2 during diffusion limitation?

A

Yes as long as some diffusion is still occuring

151
Q

How is AaDO2 affected by a shunt?

A

AaDO2 is increased, arterial is decreased because some blood bypasses alveoli

152
Q

Will additional O2 increase PaO2 with a shunt?

A

No. Blood will still not reach alveoli due to the shunt, so additional O2 will not help

153
Q

What is the main cause of hypoxemia in patients with lung disease?

A

Ventilation-perfuson inequality

Low V/Q ratie

154
Q

What are the two forms of O2 transport in the blood?

A

Dissolved and bound to hemoglobin

155
Q

True or false: Dissolved oxygen is crucial for O2 supply

A

False. The contribution of dissolved O2 is negligible compared to the O2 bound to hemoglobin

156
Q

Describe the structure of hemoglobin

A

Hemoglobin is made up of 4 subunits (2 a and 2 b) each with an iron to which O2 can bind

157
Q

Describe the color difference between oxygenated and deoxygenated hemoglobin

A

Oxygenated Hb is bright red and deoxygenated Hb is bluish

158
Q

If PO2 is above 60, how does Hb saturation change with changes in PO2?

A

Not very much. The Hb saturation curve is relatively flat above 60

159
Q

What is the pO2 in tissues, and how does this facilitate O2 release?

A

pO2 of tissues is around 40

Hb releases O2 rapidly at pO2 under 60 mmHg

160
Q

What is the normal saturation of hemoglobin?

A

More than 90%

161
Q

What factors decrease Hb affiinity for O2

A 
Increased Temp
Increased 2,3 BPG
Increased CO2
Increased [H+] (decreased pH)
ALL RIGHT SHIFT CURVE
162
Q

What is the affinity of Hb for CO compared to O2?

A

The affinity for CO is more than 200x higher

163
Q

In 1 mmHg of CO, what percentage of Hb is saturated?

A

All binding sites, 100 %

164
Q

If Hb saturation drops from 97.5% to 90%, what happens to PaO2?

A

PaO2 will fall from 100 mmHg to 60 mmHg

165
Q

What is the oxygen capacity of normal blood?

A

If Hb is 100% saturated, the O2 capacity is 20.1 mL O2/100 mL blood

166
Q

What happens to the Hb saturation curve when concentration of Hb changes (polycythemia, anemia)

A

The scale of the curve changes making 100% saturation at a different O2 concentration. In polycythemia, more Hb, and more O2 can bind, so the curve is higher. Anemia is lower.

167
Q

What are the three forms of CO2 in the blood and what percentage of each is used?

A

Dissolved (10%)
Bicarbonate (60-70%)
Carbamino compounds (20-30%)

168
Q

Does CO2 bind to the heme group in carbamino compounds?

A

No. CO2 binds to the N-terminus of the hemoglobin subunits.

This is a different site than the O2 binding site on the heme group.

169
Q

What happens when intracellular [H+] and [HCO3-] increase?

A

The anion exchanger moves HCO3- out in exchange for Cl- keeping the electrical charge balanced
“Chloride shift”

170
Q

What is the Haldane effect?

A

The lower the O2 saturation, the higher the CO2 concentration
As Hb release O2, they are increasingly likely to pick up CO2

171
Q

Which gas concentration changes more in response to changes in its own partial pressure: O2 or CO2?

A

CO2 changes more in response to changes in partial pressure (has a steeper dissociation curve)

172
Q

What is tissue hypoxia?

A

Insufficient oxygen supply to maintain aerobic metabolism

173
Q

What are the four major types of tissue hypoxia?

A

Hypoxic hypoxia
Circulatory hypoxia
Anemic hypoxia
Histotoxic hypoxia

174
Q

What is hypoxic hypoxia?

A

Decreased arterial PO2 leading to insufficient O2 supply

Can cause cyanosis if Hb falls below 6 g/dL

175
Q

What is circulatory hypoxia?

A

Inadequate blood flow to tissues (aka stagnate hypoxia)

176
Q

What is histotoxic hypoxia?

A

Inability of the cell to use O2 due to poisoning

177
Q

Describe the general components of respiratory control

A

Sensors provide input to the control center in the brainstem which provides output to effector muscles that provide negative feedback opposing the firing of the sensors

178
Q

What are the major sites of automatic respiratory control?

A

The respiratory control center
Central chemoreceptors
Peripheral chemoreceptors
Pulmonary mechanoreceptors/sensory nerves

179
Q

What are the two groups of cells in the medulla that control respiration?

A

The dorsal respiratory group controls inspiration

The ventral respiratory group controls expiration

180
Q

What are the two centers within the pontine respiratory group?

A

The apneustic center, which has an excitatory effect on the DRG to stimulate inspiration
The pneumotaxic center, which inhibits the DRG and thus inhibits inspiration

181
Q

Where are the central chemoreceptors found?

A

On the ventrolateral surface of the medulla oblongata near CN IX and X

182
Q

Changes in what trigger activity of the central chemoreceptors?

A

Changes in pH

pH changes due to changes in pCO2

183
Q

If the concentration of H+ goes up, what happens to ventilation?

A

Increased [H+] (decreased pH) stimulates increased ventilation

184
Q

What are the only chemoreceptors that respond to changes in PO2?

A

The peripheral chemoreceptors of the carotid bodies and the aortic bodies

185
Q

Do the aortic bodies respond to changes in pH?

A

No. Only the carotid bodies respond to changes in pH

186
Q

What is the cutoff value for arterial pO2 that stimulates a large response from peripheral chemoreceptors?

A

When PaO2 falls below 70-80 mmHg, the peripheral chemoreceptors are very active

187
Q

What is the Hering-Breuer reflex?

A

Inflation of the lung inhibits inspiratory muscle activity

Deflation of the lung initiates inspiratory activity

188
Q

What are the 5 types of receptors involved with control of regulation?

A
  1. Pulmonary stretch receptors
  2. Irritant receptors
  3. J receptors and C fibers
  4. Nose/upper airway receptros
  5. Joint/muscle, pain/temperature and arterial baroreceptors
189
Q

How does PaO2 affect ventilatory response to CO2 levels?

A

At lower PaO2, ventilation at a given PaCO2 is higher. With less O2, the body is more sensitive to CO2

190
Q

What factors can decreases the ventilatory response to CO2?

A

Sleep, aging, athletic training, Drugs (morphine, anesthetics), increased work for breathing (COPD)

191
Q

If PaCO2 is increased, how does the ventilatory response to low O2 changes?

A

Ventilation increases when O2 falls below 100 mmHg is the PaCO2 is high (compared to 50-70 mmHg for normal PaCO2 concentrations)

192
Q

How does metabolic acidosis affect ventilation?

A

The decrease in pH stimulates ventilation, despite the low PaCO2

193
Q

How doe PaO2, PCO2 and pH change during moderate exercise?

A

They all stay relatively constant.

194
Q

What is Kussmaul breathing?

A

Deep breathing with normal or reduced frequency

Typical in severe acidosis like diabetic ketoacidosis

195
Q

What is apneustic respiration?

A

Prolonged inspiration followed by quick exhalation

Due to loss of vagal nerve input from pneumotaxic center

196
Q

What is Cheyne-Stokes ventilation?

A

10-20 seconds of apnea followed by hyperventilation with waxing/waning tidal volumes

197
Q

What s Biot’s ventilation?

A

Groups of quick, shallow inspirations followed by regular or irregular periods of apnea

198
Q

How is barometric pressure affected by altitude?

A

Barometric pressure decreases exponentially with altitude

199
Q

What is the major mechanism for acclimatization to high altitudes?

A

Hyperventilation

By hyperventilating, your PCO2 falls which in turn increases alveolar PO2

200
Q

Describe the changes that occur to your ventilation when you get to high altitudes.

A

First, respiratory alkalosis (low PaCO2 and high pH) occur which prevent increases in ventilation
After 2-3 days, compensations return pH to normal and ventilation increases to decrease alveolar CO2

201
Q

How does RBC concentration change at high altitudes?

A

Polycythemia (increased # RBCs) increases the Hb concentration and thus the capacity for O2 increases

202
Q

How do % saturation and O2 concentration change in polycythemia?

A

%Saturation is decreased but the overall O2 content is normal or increased due to more RBCs being present

203
Q

How does the Hb-O2 binding curve change at high altitudes?

A

Right shift due to 2,3 DPG which results in better release of O2 to tissues

204
Q

How does pressure change with depth of water?

A

Pressure increases 1 atm for every 10m of depth

205
Q

What is the diving response?

A

Optimized respiration to allow staying underwater for extended periods of time

206
Q

What changes occur during the diving response?

A

peripheral vasoconstrction, initial hypertension, bradycardia, and enhanced Hb concentration due to splenic contraction

207
Q

Does hyperventilating before diving help breath holding ability?

A

No. It is very dangerous.

Hyperventilating reduces the CO2 drive to breath which can cause loss of consciousness without any forewarning

208
Q

What is ascent blackout?

A

Rapid loss of consciousness during ascent from a dive. The barometric pressure decreases and so does the partial pressure of O2. When the lung expands, it is starved for O2 and pulls O2 out of the blood, leading to LOC

209
Q

Describe barotrauma of descent

A

If a diver inhales to TLC and then dives, the vital capacity gets compressed as they go deeper. At normal pressures, most of blood is found outside of the thorax, but as the pressure increases, more is pushed into the thorax.
VC is compressed to zero, and the thoracic cavity begins to fill with blood.
Can lead to atelectasis, edema and ruptured vessels

210
Q

What is decompression sickness?

A

Nitrogen is forced into tissues at high pressures (during a dive) and then during ascent the N2 leaves the tissues. If the diver ascends too fast, N2 bubbles can form that can block blood flow

211
Q

How is CO poisoning treated?

A

Hyperbaric oxygen therapy
If most of Hb is bound to CO, increasing P will dissolve more O2 into solution, thus increasing the plasma’s O2 carrying capacity.
More O2 in the plasma also competes with CO for binding sites

FHB Exam 2 (3 decks)

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