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ITEM	NORMAL VALUE	COMMENTS
General Stuff
Pleural Pressure: Beginning of Inspiration (At Functional Residual Capacity)	-5 cm H2O	5 cm H2O less than atmospheric pressure
Pleural Pressure: End of Inspiration	-8 cm H2O	With normal inspiration, the change in pleural pressure is very small.
Total Alveolar Surface Area for Gas Exchange	75 m2
Normal alveolar diffusion barrier	1 micron
Airway Resistance and Flow
Overall Airway Resistance	0.5 - 1.5 cm H2O / mL / sec
Fraction of Vital Capacity in the First second of a forced maximal exhalation (FEV1 / FVC)	70% - 80%	The FVC test is used to measure airway resistance. Subnormal value indicates COPD.
Gas Exchange
Atmospheric PO2	21% of 760 mm Hg 160 mm Hg
Inspired PO2 PIO2	= (21%) x (747 - 47 mm Hg) = 147 mm Hg	Air becomes saturated with water which has partial pressure of 47 mm Hg. Thus we take the PO2 of dry air = (21%)(700)
Inspired PCO2 PICO2	Virtually 0	Atmospheric air contains virtually no CO2
Alveolar PO2 PAO2	100 mm Hg	O2 has gone down from 147 mm Hg because some O2 moves to the blood.
Alveolar PCO2 PACO2	40 mm Hg	This is the amount of CO2 that enters alveoli from blood in a healthy lung.
Mixed Venous PO2 PVO2	40 mm Hg	40 torr is the standard O2 concentration of mixed venous blood, as determined by how much O2 the tissues need.
Mixed Venous PCO2 PVCO2	46 mm Hg	The CO2 gradient for gas transport is only 6 mm Hg -- difference between 46 and 40.
Arterial PO2 PaO2	90 - 95 mm Hg	It is slightly less than PAO2 due to contribution of venous admixture.
Arterial PCO2 PaCO2	40 mm Hg	It is virtually the same as PACO2 but theoretically higher due to venous admixture.
Dead Space
Tidal Volume	450 - 500 mL	Volume of air during normal inspiration
Anatomical Dead Space	150 mL	The individual's weight in lbs = anatomical dead space in mL
VD / VE Ratio Ratio of dead space to expired air	0.2 to 0.3, i.e. 20% - 30% of expired air is dead space. When VD/VE ------> 0.6, patients are put on a ventilator.	High dead space occurs with pulmonary embolism, and with low VA/Q ratios.
Respiratory Quotient VCO2 / VO2	0.8 We exchange about 80% as much CO2 as O2 with each inspiration	The reciprocal is 1.2, the fudge-factor for the alveolar ventilation equation.
Gas Transport and Acid-Base Balance
Plasma Solubility Coefficient of O2 (SO2)	0.003 mL O2 / dL plasma, or 0.003 Vol-%
Plasma Solubility Coefficient of CO2 (SCO2)	0.03 mL CO2 / dL plasma, or 0.03 Vol-%	CO2(g) is thus 10x more soluble than O2(g)
O2 Carrying-Capacity of Hemoglobin	1.34 mL O2 / g Hb One gram of Hb holds 1.34 mL of O2.	Thus: Maximum HbO2 = (Hematocrit)(1.34)
Hematocrit	15 g Hb / dL blood
HbO2 Normal O2-Carrying Capacity of hemoglobin	20 vol-%	(Hematocrit)(1.34) = (15 g Hb / dL)(1.34) = 20 mL O2 / dL
Arterial Hb-Saturation Arterial PaO2 (Oxygen partial pressure) Arterial CaO2 (Oxygen Content)	100% saturation PaO2 = 100 mm Hg CaO2 = 20 mL / dL	Arterial: 100% saturation ------> 100 mm Hg ------> 20 mL / dL O2 content
Venous Hb-Saturation Venous PvO2 (Oxygen partial pressure) Venous CvO2 (Oxygen content)	75% saturation PVO2 = 40 mm Hg CvO2 = 15 mL / dL	Venous: 75% saturation ------> 40 mm Hg ------> 15 mL / dL O2 content
P50	50% saturation P50 = 26 mm Hg	P50 is the PO2 required to achieve 50% hemoglobin saturation
Normal plasma HCO3-	24 mM
Normal blood pH	7.4	A 0.1 decrease in pH corresponds to a 1 mM increase in HCO3-, in healthy, uncompensated hypoventilation.
Ventilation / Perfusion of the Lung
VA/Q Ratio, Lung Apex (Top)	3.0	Apex of lung gets less ventilation and less perfusion, but perfusion is substantially less than at base.
VA/Q Ratio, Lung Base (Bottom)	0.5 - 0.6	Base of lung gets greater perfusion and ventilation, but perfusion is substantially greater than at apex.
VA/Q Ratio, Overall	1.0	Overall ventilation / overal perfusion 1
Overall Perfusion of Lung	5.0 - 6.0 L / min	That is, overall lung perfusion = Cardiac Output
Overall Ventilation of Lung	5.0 - 6.0 L / min	This is equal to (respiratory rate) x (tidal volume)