Lecture 4 (Test 2) Flashcards
What happens to outside gas when it enters the body?
The body heats and humidifies the gas, displacing some incoming gases.
Humidification introduces a vapor pressure of about 47 mmHg.
What is the PO2 of inspired air after humidification?
150 mmHg for O2 and 0 mmHg for CO2.
These values reflect the gas composition after humidity is added.
What are the typical gas pressures in pulmonary arterial blood?
O2 = 40 mmHg, CO2 = 45 mmHg.
These values are the same as those in deoxygenated systemic venous blood.
What occurs during gas exchange in the lungs?
CO2 levels drop by about 5 mmHg, and O2 levels increase to about 100 mmHg.
The PO2 can be as high as 104 mmHg in healthy individuals.
What does PaO2 of 100 mmHg signify?
It represents systemic arterial blood.
Normal CO2 levels in systemic arterial blood should be about 40 mmHg.
How does aging affect arterial PO2?
Arterial PO2 decreases with age, dropping from about 100 mmHg at age 20 to closer to 80 mmHg by age 90.
Lung function begins to decline around age 20.
What is dead space ventilation?
It refers to the portion of each breath that is not used for gas exchange.
In a 500cc breath, typically 150cc is dead space.
What is anatomical dead space?
The conducting zones of the upper respiratory system.
This includes areas where no gas exchange occurs.
What is alveolar dead space?
Dead space that occurs when ventilated alveoli are not perfused.
An example is ventilation of a lung area affected by a pulmonary embolism.
What does physiologic dead space encompass?
It includes both anatomical and alveolar dead space.
Increased dead space may necessitate higher ventilation rates.
What is the tidal volume (VT) equation?
VT = VD + VA.
VD is dead space ventilation, and VA is alveolar ventilation.
What is minute ventilation?
The total amount of ventilation occurring over a minute.
Calculated as the product of tidal volume and respiratory rate.
What is the calculation for minute alveolar ventilation?
Minute alveolar ventilation = alveolar ventilation per breath x breaths per minute.
For example, 350cc x 12 breaths/min = 4.2 liters/min.
How is total ventilation per minute (VE) calculated?
VE = minute alveolar ventilation + minute dead space ventilation.
Example: 4.2 liters + 1.8 liters = 6 liters/min.
What does VE stand for?
Total minute ventilation, representing expired air.
It includes both dead space and alveolar air.
What is the significance of the first 150cc of an expired breath?
It consists of dead space gas.
The remaining 350cc is a mixture of lung air.
What is the expected alveolar PO2 with normal ventilation and blood flow?
About 104 mmHg.
This reflects the gas exchange efficiency in healthy lungs.
What is the normal minute alveolar ventilation?
4.2 liters per minute
If alveolar ventilation increases, what happens to alveolar PO2?
It should rise
True or False: You can have an alveolar PO2 of 150 mmHg breathing room air.
False
What happens to alveolar PO2 if alveolar ventilation decreases?
It probably goes down
What is the normal alveolar PCO2 with normal ventilation?
40 mmHg
What occurs to alveolar PCO2 with higher-than-normal alveolar ventilation?
It is expected to be lower
What happens to alveolar PCO2 with lower-than-normal alveolar ventilation?
It is expected to be higher