Term
| What are the percentages of O2, N2 and CO2 in the air? |
|
Definition
O2 = 21%
N2 = 79%
CO2 = 0.04% |
|
|
Term
| Does total barometric pressure increase or decrease with elevation? |
|
Definition
decreases
sea level = 760 mmHg
10,000 ft = 522 mmHg
30,000 ft (Mt. Everest) = 226 mmHg |
|
|
Term
| What is the partial pressure of O2 in alveolar space (PAO2)? |
|
Definition
|
|
Term
| What is the partial pressure of O2 in arterial blood (PaO2)? |
|
Definition
|
|
Term
| What is the partial pressure of O2 in venous blood (PvO2)? |
|
Definition
|
|
Term
| What is the partial pressure of CO2 in alveolar space (PACO2)? |
|
Definition
|
|
Term
| What is the partial pressure of CO2 in arterial blood (PaCO2)? |
|
Definition
|
|
Term
| What is the partial pressure of CO2 in venous blood (PvCO2)? |
|
Definition
|
|
Term
| What is the pO2 of air in the trachea? |
|
Definition
|
|
Term
What is the "big A-little a gradient"?
what are the normal values for pO2 and pCO2? |
|
Definition
"big A-little a gradient" = the difference between alveolar and arterial partial pressures
normal values:
5 mmHg for pO2
no gradient for pCO2
|
|
|
Term
| What are the four causes of arterial hypoxemia? |
|
Definition
hypoventilation
diffusion impairment
shunt blood flow
ventilation-perfusion mismatching |
|
|
Term
| what is the most common cause of arterial hypoxemia? |
|
Definition
| ventilation-perfusion mismatching |
|
|
Term
| What is the best measure of alveolar ventilation? |
|
Definition
|
|
Term
| What is oxygen partial pressure in the alveoli is proportional to? |
|
Definition
the difference between the partial pressure of the air you are breathing and alveolar CO2 (PACO2)
(alveolar gas equation) |
|
|
Term
| According to the diffusion equation, how does emphysema affect diffusion of oxygen across the alveolocapillary membrane? |
|
Definition
| it decreases the area for surface exchange |
|
|
Term
| According to the diffusion equation, how does pulmonary fibrosis affect diffusion of oxygen across the alveolocapillary membrane? |
|
Definition
| it increases the thickness of the membrane |
|
|
Term
| If a patient has a septal defect in their heart, how high can their PaO2 be raised on 100% O2? |
|
Definition
150 mmHg
(normally, a person should be able to get a PaO2 of 500 mmHg on 100% O2) |
|
|
Term
| What is the VdotA/Q ratio in "shunt" alveoli? |
|
Definition
VdotA/Q ratio approaches 0
Example:
PAO2 = 40 mmHg
PACO2 = 46 mmHg |
|
|
Term
| What is the VdotA/Q ratio in "dead space" alveoli? |
|
Definition
VdotA/Q ratio approaches ∞
Example:
PAO2 = 150 mmHg
PACO2 = 0 mmHg |
|
|
Term
| Would a mucous plug cause dead-space or shunt alveoli? |
|
Definition
|
|
Term
| Would a pulmonary embolus cause dead-space or shunt alveoli? |
|
Definition
|
|
Term
| What are the normal PAO2 and PACO2 values for basal alveoli? |
|
Definition
PAO2 = 89 mmHg
PACO2= 42 mmHg |
|
|
Term
What are the normal PAO2 and PACO2 values for apical alveoli?
|
|
Definition
PAO2 = 132 mmHg
PACO2 = 28 mmHg |
|
|
Term
| What is the Va/Q at the apex of the lung? At the base? |
|
Definition
|
|
Term
| Which is worse: a high Va/Q or a low Va/Q? |
|
Definition
|
|
Term
| Do wide ventilation-perfusion inequalities exert a greater effect on PaO2 values or PaCO2 values? |
|
Definition
PaO2
PaO2 values fall while PaCO2 values are retained |
|
|
Term
| Why do CO2 levels remain near normal in Va/Q mismatching? |
|
Definition
| Alveoli with low Va/Q ratios will retain excess CO2 and alveoli with high Va/Qs will blow off excess CO2 |
|
|
Term
| What is the only cause of hypoxemia in which arterial PO2 does not rise to the expected level when a pt is given 100% O2? |
|
Definition
|
|
Term
| What is the alveolar gas equation? |
|
Definition
| The alveolar gas equation calculates the partial pressure of oxygen in the pulmonary alveoli (PAO2). It states that PAO2 is proportional to the difference between PiO2 and PACO2. The equation is necessary because it is not practical to take a sample of gas from the alveoli. It assumes that PACO2 = PaCO2 |
|
|
