RESPIRATION PHYSIOLOGY: ALVEOLAR GAS EXCHANGE |
NOTATION |
| SYMBOLS
V = volume V' = rate or flow P = pressure F = fraction (percent) C = content (concentration) S = percent saturation (of Hb) R = V'CO2 / V'O2 f = respiration frequency (breaths/min) |
SITE
I = inhaled (inspired) E = exhaled (expired) A = alveolar B = barometric a = systemic arterial blood v = systemic venous blood c = capillary blood |
GAS
O2 = oxygen CO2 = carbon dioxide N2 = nitrogen H2O = water vapor CO = carbon monoxide |
Examples:
PA-CO2 = alveolar partial pressure of carbon dioxide
Ca-O2 = content (concentration) of oxygen in systemic arterial blood
V'O2 = oxygen consumption rate
PRESSURE UNITS
The traditional units for pressure measurement in medicine are based on the height of a column of liquid: mmHg (which is the same as torr) and cmH2O. The official metric system unit for pressure measurement is the pascal. The metric unit is slowly making its way into the clinical literature. To convert between units, note that (approximately)
1 kPa (kiloPascal) = 7.5 mmHg = 10 cmH2O
| RsAlvlNttn.htm -- A5B15 | © AC Brown 2005 |