Determination of the alveolar dead space

Abstract

The author suggests a method of finding the alveolar dead space (AIDS), i.e. the part of the functional dead space (FDS) which presents the greatest difficulties for determination. A1DS determination is based on the difference in the CO2 concentration in the venous blood flowing to the lungs for oxygenation under conditions of respiration at rest, and of CO2 concentration in the alveolar portions of expriation following 10-sex breath withholding at the level of the usual inspiration. The mean A1DS volume (VDA1) in % to the alveolar part of the tidal volume for 20 healthy persons in sitting position and in 12 of them in lying position was found: VDA1 (in sitting position)= = 8.0 +/- 1.5% (P = 0.95), sigma = 3%; VDA1 (in lying position) = = 5.0 +/- 0.7% (P = 0.95), sigma = 2.6%. It is suggested that FDS determined by this method be used to judge the efficacy of using the inspired air in the lung ventilation, to determine AIDS in the diagnosis of lung embolism, to judge the pulmonary circulation shunt by the difference between the value found according to Bohr's formula for FDS and the FDS value established according to the suggested formula.