[The relationship between respiratory function and the change in end-tidal nitrous oxide concentration].
The aim of the present study is to clarify the relationship between respiratory function and the rate of change in alveolar anesthetic concentration. We measured the concentration of end-tidal nitrous oxide (N2O) when 50% N2O was administered to 15 patients of ASA I possessing normal respiratory function during the course of propofol-100% oxygen anesthesia. All patients were ventilated at a rate of 8-10 ml.kg-1 x 8 times per minute using a conventional anesthetic ventilator with semi-closed circuit and 4 l.min-1 inflow of fresh gas. Arterial CO2 partial pressure was maintained at 36.2 +/- 1.8 mmHg and no significant circulatory change was observed while N2O was administered. The rate of increase of end-tidal N2O concentration in poor FEV1.0/FVC% group was significantly slower than that in high FEV1.0/FVC% group, while there was no relation between %VC and the end-tidal N2O concentration change. Since N2O is an inhaled anesthetic, it is well considered that the effect of FEV1.0/FVC% may be observed in other inhaled anesthetic although the magnitude of the effect may vary. The present result suggests that respiratory function, especially FEV1.0/FVC%, is an important factor affecting the rate of change in alveolar anesthetic concentration and, in lower FEV1.0/FVC% group, it takes more time to achieve the intended alveolar concentration.
Tsuchiya
M
M
Department of Anesthesia, and Emergency and Critical Care Medicine, National Hospital Tokyo Disaster Medical Center, Tachikawa.
Tokai
H
H
Kataoka
Y
Y
Manabe
M
M
D000368:Aged; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics*; D018686:Anesthetics, Intravenous; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D009609:Nitrous Oxide / Q000493:pharmacokinetics*; D015742:Propofol; D011650:Pulmonary Alveoli / Q000378:metabolism; D012119:Respiration; D012121:Respiration, Artificial; D013997:Time Factors
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D009609:Nitrous Oxide; D015742:Propofol