A method to predict pulmonary blood flow by nitrous oxide washout curve
Nomoto, Y.; Ikegami, T.; Ohtsaka, Y.; Nagayama, N.
Masui. Japanese Journal of Anesthesiology 39(1): 19-26
1990
ISSN/ISBN: 0021-4892 PMID: 2304248 Document Number: 350375
The study was performed to obtain a relationship between the pulmonary blood flow and the .tau.b (time constant) calculated from multiple-breath nitrous oxide (N2O) washout curve. Elimination of N2O depends on pulmonary blood flow and alveolar ventilation. From the theoretical consideration, .tau.b can be calculated by the following formula; .tau.b=Vd[1/.ovrhdot.Qt-.ovrhdot.QS)+0.47/.ovrhdot.VA).........(1) Vd=N2O volume of distribution in the body .ovrhdot.Qt=cardiac output, .ovrhdot.Qs=shunt blood flow .ovrhdot.VA=alveolar ventilation. Relationship between observed .ovrhdot.Qt-.ovrhdot.Qs and observed .tau.b was admitted to the predicted formula. The method was compared with the thermodilution method in almost simultaneous measurement of the cardiac output. A good correlation was obtained between them (r=0.87). Washout curve of nitrous oxide can be used for a reliable measurement of pulmonary perfusion.