Three steps in the process of oxygenation
- Ventilation
- Perfusion
- Diffusion
Ventilation
moving gases in and out of the lungs.
Perfusion
the ability of the CV system to pump oxygenated blood to the tissues and return deoxygenated blood to the lungs
Diffusion
exchange of the respiratory gases in the alveoli and capillaries of the body tissues by concentration gradients.
Poor diffusion is present in patients with
- pulmonary edema (fluid CHF)
- pulmonary infiltrates (pneumonia infection)
- pleural effusion (fluid between the visceral and parietal pleura)
- lobectomy
- pneumothorax (lung collapse due to air in space around lung)
The amount of energy expended on breathing depends on what 3 factors?
- rate and depth of respirations
- lung compliance
- airway resistance
Inspiration
active process triggered by chemical receptors in the aorta
Expiration
passive process: depends on elastic recoil ability of the lungs
Lung Compliance
ease of which the lungs can expand.
Lung Compliance decreases in diseases such as:
- pulmonary edema
- interstitial and pleural fibrosis
- congenital or traumatic structural abnormalities (kyphosis or rib fracture)
Airway resistance includes
asthma, tracheal edema
Surfactant
chemical produced in the lungs to keep the alveoli from collapsing.
Diseases processes can alter the lung elasticity (ability to recoil) such as
COPD: Emphysema
COPD: Emphysema
-accessory muscles are used to increase lung volume but in the long term is not efficient and the patient will fatigue and decompensate.
In patients with emphysema, assess for
-elevation of the clavicles during inspiration -> leads to air hunger, ventilatory fatigue and decreased lung expansion.
Atelectasis
- collapse of the alveoli.
- prevents normal exchange of oxygen and CO2
decreased lung compliance =
increased airway resistance
increased airway resistance =
increased use of accessory muscles
increased use of accessory muscles =
increased work of breathing
increased work of breathing results in:
increased energy expenditure, metabolic rate, need for more oxygen, and need for elimination of CO2
Lung volumes include
- tidal volume
- residual volume
- forced vital capacity
tidal volume
normal amount of air exhaled after a normal inspiration (usually around 500 ml)
residual volume
amount of air left in the alveoli after expiration (necessary to keep alveoli expanded)
forced vital capacity
amount of air that can be removed from the lungs during forced expiration
Delivery of oxygen to the body depends on
- ventilation
- perfusion
- diffusion
- oxygen carrying capacity (Hgb available)
What are three factors that influence the capacity of the blood to carry O2?
- the amount of dissolved O2 in the plasma
- the amount of Hgb
- the tendency of Hgb to bind with O2
CO2
byproduct of cellular metabolism that diffuses into RBCs rapidly and combines with fluid to form carbonic acid (H2CO3)
H2CO3 dissociates to form
H+ and HCO3-
After Hgb loses its O2 to the tissues (deoxyhemoglobin), what happens next?
it combines with CO2 and is transported via venous blood back to the lungs to be exhaled.
Regulation of Respiration includes 2 types
- Neural Regulation
2. Chemical Regulation
Neural Regulation of Respirations
- includes the CNS.
- voluntary control of respiratory rate, depth and rhythm by the cerebral cortex.
Chemical Regulation of Respirations
- regulated by chemoreceptors located in the medulla, aortic body and carotid body to maintain normal blood gas levels.
- regulates respiratory rate based on changes in CO2, O2 and H+ ion (pH of blood)
Stroke volume
amount of blood ejected from the ventricles during systole (each beat)
Cardiac output
SV x HR
Starling’s Law: in a healthy heart
as the myocardium stretches, the strength of the contraction increases.
Starling’s Law: in a diseased heart
the increased stretch of the myocardium may be beyond its physiological limits resulting in decreased SV due to blood backing up in pulmonary circulation (left sided heart failure) or systemic circulation (right sided heart failure)
The coronary arteries fill during
ventricular diastole
During Ventricular Diastole
AV valves open as blood flows from the atria to the ventricles
During Ventricular Systole
AV valves close and the Semilunar valves open.
Conduction System of the Heart includes
- SA node (pacemaker)
- AV node
- Bundle of His
- Purkinje Fibers
AV node
via intratrial pathways.
impulse is delayed before reaching bundle of his to allow the atrium to empty
Factors that Affect Oxygenation
- Physiological
- Developmental
- Lifestyle
- Environmental
Any condition affecting cardiopulmonary functioning directly affects the ability of the body to meet O2 demands including
- Respiratory Disorders
- Cardiac Disorders
- Other processes
Respiratory disorders that affect oxygenation include
hyperventilation, hypoventilation, and hypoxia
Cardiac disorders that affect oxygenation include
- disturbances in conduction system
- impaired valvular function
- myocardial hypoxia
- cardiomyopathic conditions
- peripheral tissue hypoxia
Other processes that affect oxygenation include
- decreased O2 carrying capacity of blood (anemia, CO poisoning)
- decreased inspired O2 concentration (drug overdose, obstruction)
- increased metabolic demand of the body
- hypovolemia (dehydration/volume loss from trauma)
- alterations in chest wall movement (musculoskeletal or neuromuscular) pregnancy. obesity.
Hypovalemia
decreased circulating volume -> decreased O2 to body tissues -> increased PVR (to compensate) -> increased HR (to increase amount of blood returned to the heart) -> increases CO
Metabolic Rate
All increased metabolic activity increases metabolic demand. Ex) fever
Factors Affecting Oxygenation: Trauma
Ex) Rib fracture causing Flail Chest
Ex) Surgical incisions: increased pain -> decreased RR or shallow respirations to avoid pain
Factors Affecting Oxygenation: CNS alterations
- cervical trauma (ex. paralysis of phrenic nerve which operates the diaphragm)
- spinal cord injuries
- neuromuscular diseases
Factors Affecting Oxygenation: Chronic Diseases
ex) emphysema causes barrel chest due to overuse of accessory muscles and air trapping in the alveoli
Normal CO2 levels
35-45 mm Hg
Normal O2 levels
80-100 mm Hg
Normal SpO2 levels
> 95
Hypoventilation
when alveolar ventilation is inadequate to meet O2 demands of the body.
Causes of hypoventilation
- atelectasis (collapse of the alveoli prevents normal exchange)
- COPD: respiratory drive from decreased O2 instead of increased CO2.
Signs and Symptoms of Hypoventilation
- mental status changes
- dysrhythmias
- potential cardiac arrest-convulsions
- unconsciousness
- death
Hyperventilation
a state in which the lungs remove CO2 faster than it is produced by cellular metabolism
Causes of Hyperventilation
severe anxiety (fever), drugs (amphetamines), or acid-base imbalances
Signs and Symptoms of Hyperventilation
- rapid respirations
- sighing breaths
- numbness and tingling of extremities
- light-headedness
- loss of consciousness
Hypoxia
inadequate tissue oxygenation at the cellular level
Causes of Hypoxia
- decreased hemoglobin
- decreased inspired O2
- inability of tissues to extract O2 from the blood (CO poisoning)
- decreased diffusion (pneumonia)
- poor tissue perfusion (shock)
- impaired ventilation (chest trauma)
Signs and Symptoms of Hypoxia
- apprehension
- restlessness
- inability to concentrate
- decreased LOC
- dizziness
- behavioral changes
- VS changes (increased pulse and depth of respirations)
- fatigue
- respiratory arrest
What is a late sign of hypoxia?
cyanosis
Alterations in Cardiac Functioning
- Cardiac Rhythm
- Strength of Contraction
- Blood flow through the heart or to the heart muscle
- Decreased peripheral circulation
Cardiac Rhythm
conduction disturbances (dysrhythmias)
Causes of dysrhythmias
- ischemia
- valvular abnormality
- anxiety
- drug toxicity-caffeine, alcohol or tobacco
- complications of acid-base or electrolyte imbalances
Types of Dysrhythmias
- tachydysrhythmias
- bradydysrhythmias
- supraventricular dysrhythmias
- ventricular dysrhythmias
Tachydysrhythmias and Bradydysrhythmias
- decreased CO (tachycardia by decreasing filling time; bradycardia by decreasing heart rate)
- decreased BP
Supraventricular Dysrhythmias
- supra ventricular tachycardia (rate 150-250)
- atrial fibrillation/flutter
Ventricular Dysrhythmias
- Life threatening
- Ventricular Tachycardia
- Ventricular Fibrillation
Calculation of HR from an E
not sure if you need to know this? Slide 31
Failure of the heart to pump a sufficient volume of blood to the systemic and pulmonary circulation (pump failure) occurs in:
- HF
- CAD
- Cardiomyopathy
- Valvular Disorders
- Pulmonary Disease
Left Sided Heart Failure
decreased functioning of the left ventricle resulting in decreased CO
Sign and Symptoms of Left Sided Heart Failure
- fatigue
- SOB on exertion
- dizziness
- confusion (tissue hypoxia)
- rales
- cough
- dyspnea
Left Sided Heart Failure results in
blood pooling in the pulmonary circulation causing pulmonary congestion.
Right Sided Heart Failure
impaired function of the right ventricle is usually a result of pulmonary disease or long-term impaired left-sided heart failure
Primary Signs and Symptoms of Right Sided Heart Failure
- increased PVR
- increased O2 demand of the heart
- decreased blood ejected from right ventricle -> blood begins to back up in systemic circulation
Other Signs and Symptoms of Right Sided Heart Failure
- Weight gain
- Distended neck veins
- Hepatomegaly
- Splenomegaly
- dependent peripheral edema
Impaired Valvular Function
congenital or as a result of disease. Stenosis and regurgitation
Stenosis
flow of blood through the valves is obstructed causing the ventricle to hypertrophy leading to L or R sided heart failure
Regurgitation
valves do not close all the way causing back-flow of blood (causes a murmur)
Myocardial Ischemia: Angina
imbalance between myocardial O2 supply and demand.
Angina is precipitated by
activities that increase myocardial O2 demand (exercise, stress, eating a big meal).
usually lasts 3-5 minutes.
Myocardial Infarction
- sudden decrease in coronary blood flow or an increase in myocardial O2 demand with inadequate coronary perfusion.
- may occur at rest, lasts 20 minutes or more, unrelieved by any measures
How does age influence oxygenation?
heart disease, decrease in functional cilia (decreases the effectiveness of the cough mechanism)
How does lifestyle factors influence oxygenation?
- smoking
- low-cholesterol/low-Na = diet
- HTN
- Exercise
- Sedentary life-style
How does nutrition influence oxygenation?
- obesity (decreased lung expansion, increased body tissue demands)
- malnourished-muscle wasting (cough efficiency is reduced putting patients at risk for retention of pulmonary secretions)
How does exercise influence oxygenation?
people who exercise 30-60 min/day have decreased HR, BP and cholesterol; increased blood flow and O2 extraction by muscles
How does smoking influence oxygenation?
- COPD, lung cancer, increase peripheral vascular resistance, CAD.
- Nicotine causes vasoconstriction increase BP, decrease coronary perfusion.
How does substance abuse influence oxygenation?
impairs oxygenation in two ways:
- usually poorly nourished
- depresses the respiratory center (may cause permanent lung damage (inhalants))
How does stress influence oxygenation?
increases metabolic rate and O2 demand
How does environmental factors influence oxygenation?
-pollution, occupational hazards/pollutants (ex asbestos, dust and airborne spores)
