gas exchange (midterm 3) Flashcards
what is partial pressure defined by
Henry’s law: concentration of dissolved gas divided by solubility coefficient
is CO2 or O2 more soluble and why
CO2 because O2 needs a bigger gradient
O2 = 0.024
CO2 = 0.570 (solubility coefficients)
what happens if the partial pressure is higher in the alveolar gas
the O2 molecule will tend to move towards the pulmonary blood (drive O2 into blood)
what happens if the partial pressure if higher in the pulmonary blood
the CO2 molecule will tend to move towards the alveolar gas (drive O2 out of blood)
what is the functional residual capacity of the lungs
2300 mL, though only 350 mL of new air is inspired with each breath - you never get all the air out of lungs per breath
what does increased O2 consumption require
significant increase in ventilation to maintain O2 partial pressure
what does higher ventilation lead to
higher oxygen pressure
what is the average respiratory membrane thickness
0.6 microns
what is the total respiratory membrane surface area
70 m^2
what is the total blood volume in the pulmonary capillaries
60-140 mL
what factors determine the rate of gas diffusion through the respiratory membrane
- Thickness of the respiratory membrane - increases
in thickness, due to edema or fibrosis, can reduce
transport of oxygen - Surface area of the respiratory membrane -
decreases in area, due to necrosis or emphysema
where alveoli coalesce, will dramatically reduce
transport of oxygen
what is the diffusing capacity of O2 and CO2
O2: 21 mL/min/mmHg (needs bigger gradient than CO2)
CO2: 400-450 mL/min/mmHg
what does the ventilation-perfusion ratio describe
the imbalance of respiratory units sometimes lacking adequate BF (Q) or alveolar air flow (Va)
what happens when Va/Q equals 0 versus if it equals infinity
0 = no alveolar ventilation = physiological shunt
infinity = no blood flow = physiological dead space
