Work of breathing - resistance - - pressure that is required to overcome the resistance to gas flow through the airway during prespiration
Clinical conditions that increase airway resistance - - COPD
Mechanical obstruction
Infection
Asthma, bronchospasm
Work of breathing - compliance - ...
Causes for CO2 increase - ✔✔✔ - -CO2 is being produced but not being exhaled quickly enough
-increase in CO2 by increased metabolism like fever or exercise
-PaCO2 in ABG is increased therefore pH decreases
-as CO2 accumulates, peripheral and central chemoreceptors signal brain to increase RR
-PaCO2 is influenced by alveolar minute ventilation and CO2 production
-ventilation is influenced by alveolar minute ventilation and Co2 production
-O2 sat decreases because increased CO2 pressure keeps O2 away
Hypoxemia normal P (A-a) O2
(15-20) - ✔✔✔ - -lungs are working fine but there is problem above airways
-altitude
-nitrogen gas poisoning
-fire smoke (O2 displacement)
Alveolar hypoventilation increased P (A-a) O2
(>20) - ✔✔✔ - not getting enough ventilation into the alveoli, reducing oxygen
-ex. OD antidepressants slowing RR
Fixed with O2 and increased ventilation
,Causes of hypoxemia with increased P - ✔✔✔ - V/Q mismatch
Shunt
Diffusion Defect
V/Q mismatch - ✔✔✔ - areas of our lungs that are receiving ventilation are not matched with
perfused areas.
When there is high CO2, pulmonary vessels selectively vasoconstirct so blood goes where best work
is done
Low ventilation but normal perfusion because of airway secretions
Somewhat hypoxemic but not as severe as shunt
Shunt - ✔✔✔ - extreme VQ mismatch
Severe pneumonia
ARDS
When alveoli is filled with something that should not be there (fluid, blood, or infection) or alveoli is
collapsed (atelectasis) Very hypoxemic
Diffusion defect - ✔✔✔ - conditions where there is a problem in O2 diffusing into the bloodstream:
like with interstitial lung disease, some sort of irritation, body tries to restore damage, and fibroblasts
lines up on the alveolar walls. Other examples are pulmonary edema, hydrostatic pressure is too
great, leaking into interstitial space
Work of breathing - resistance - ✔✔✔ - pressure that is required to overcome the resistance to gas
flow through the airway during prespiration
Clinical conditions that increase airway resistance - ✔✔✔ - COPD
Mechanical obstruction
Infection
Asthma, bronchospasm
,Work of breathing - compliance - ✔✔✔ - the ability of the lungs to expand is measured as the lung
compliance. The volume change per unit of pressure
When more muscular effort for work of breathing is required? - ✔✔✔ - lung compliance is decreased
(ex. pulmonary edema)
Chest wall compliance is decreased (spinal cord deformity or obesity)
Airways are obstructed by bronchospasm of mucous plugging (asthma, bronchitis)
What 5 problems with oxygenation result in hypoxemia? - ✔✔✔ - -O2 concentration of FiO2
-ventilation of the alveoli (hypoventilation)
-V/Q mismatch
-Diffusion Defect
-Shunt
Examples of O2 content of FiO2 as a problem with O2 delivery to the alveoli - ✔✔✔ - high altitudes
or oxygen displacement scenarios
Examples of hypoventilation as a problem with O2 delivery to the alveoli - ✔✔✔ - unconsciousness
neurologic, muscular or bone diseases that restrict chest expansion
COPD
Examples of VQ mismatch as a problem with diffusion of O2 from the alveoli into the blood - ✔✔✔ -
atelectasis
asthma
chronic bronchitis
pneumonia
ARDS
PE
, Examples of diffusion defects as a problem with diffusion of O2 from the alveoli into the blood - ✔✔✔
- edema
fibrosis
emphysema
Examples of shunt as problem with perfusion of pulmonary capillaries - ✔✔✔ - blood flow bypassing
lungs
intracardiac defects
Intrapulmonary arteriovenous malformations
DLCO - ✔✔✔ - diffusion capacity of the lung for carbon monoxide
How is DLCO measured and preformed? - ✔✔✔ - inhale CO for 10 seconds and exhale
measure how deep of breath and how much CO is left over
diffusing capacity is a measure of the gas diffusion rate at the alveolocapillary membrane
Variables that affect DLCO - ✔✔✔ - Hb
CoHb
altitude
PAO2
body position
pulmonary capillary blood volume
asthma
obesity
When is DLCO reduced - ✔✔✔ - pulmonary fibrosis
pulmonary vascular disease
restrictive lung diseases (loss of lung volume, fibrotic lung diseases)
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