The pulmonary circulation time was assessed by measuring the parameter "TP", which had been developed and reported elsewhere,l) for detecting the disturbances of pulmonary blood flow in patients with respiratory diseases. The materials were thirteen normal subjects, seven cases of slight COPD (group I), nine cases of severe COPD (group II), and three cases of old tuberculosis with restrictive ventilatory impairement (group III). The mean Tp value were 1.78±0.48 in normal subjects, 1.55±O.39 in

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... roup I, 2.0±1.13 in group II, and 1.60±0.46 in group III. The mean Tp value was increased in severe COPD patients compared with that in normal subjects or in slight COPD patients, but the difference between them was not significant. This is because the Tp values of some severe COPD cases were increased but others were not. Meanwhile the computer simulation showed that Tp values were the sensitive parameter to assess the circulatory disturbances in the lung, by detecting the uneven distribution of QIQ in adition to delay and stagnation of the blood flow. These findings showed that the circulatory impairement would not increase in parallel with the ventilatory impairement and would be brought about at the critical advanced emphysematous stage in this type of COPD patients.