Ten healthy subjects were tested for their peripheral respiratory chemosensitivities by the withdrawal technique two times on separate days. Hypoxic hypercapnia of PET, O2 75, 65 and 55 mmHg with PET, CO2, 5mmHg higher than the control level was replaced by 100% O2 two times with spontaneous respiration. Then, breath-by-breath depression calculated in minute ventilation (ΔV) was observed during the period 5-20 sec after the first O2 inhalation. The results were analyzed by the linear relationship betweenPET, O2 and In ΔV, and Pa O2 and inΔV.ΔV at P02 50 mmHg, ΔV50, was 9.09±6.81 liters/min (mean±SD) in PET, O2-ln ΔVanalysis and 9.22±7.46 liters/min in PaO2-ln ΔV analysis, respectively. The averaged day to day variation of ΔV50 expressed by SE in % was 5.3% in PET, O2-In ΔV analysis and 11.5% in PaO2-1n ΔV analysis, respectively.
