The study reported here is composed of two parts.
The first part is concerned with the investigation of the relationships among vascular volume, vascular pressure, and the degree of inflation of the lung. The technique used here do not differ substantially from those by Riley et al. In isolated left lower lobes, a change from resting lung volume to full inflation was associated with an overall increase in the vascular volume at the low vascular pressure below 0cmH₂O. The opposite results were obtained at the high vascular pressure above 0cmH₂O. From these results, it was possible to separate the pulmonary vascular bed into two compartments that responded oppositely to inflation of the lung when vascular pressure was held constant. One compartment, consisting of relatively large vessels, always increased in volume, the other compartment, consiting of small vessels, always decreased in volume.
These results can be explained as follows, the decrease in volume of the smaller vessels might be due to decrease in their transmural pressure and an increase in volume of the relatively large vessels due to radial traction. The second is concerned with pulmonary vascular resistance as a function of both transpulmonary pressure and lung volume using isolated dog lungs by lowering the box pressure and perfused with 6% dextran in saline. The experiment is so arranged that intravascular pressure remains fixed with respect to pleular pressure (we refer to this as condition 1) and maintained in fixed relation to alveolar pressure (reffered to as condition 2).
Comparison of results obtained in these two situations affords a means of separating the contribution of alveolar vessels and extraalveolar vessels to the changes in vascular resistance accompanying changes in the inflation state of lungs. In both condition 1 and 2, vascular resistance fell about an average of 20.6% between collapsed and moderately inflated lung i. e. the curve of resistance vs. inflation pressure is U-shaped with a minimum for pressure of 5cmH₂O. This suggests that the unfurling of gnarly vessels may contribute to this resistance fall during inflation from small lung volume. I think that at the low lung volume purely volumedependent factors are primarily responsible. (With the rapid freezing method by liq. propane, some evidence of folding of alveolar vessels was found histologic-ally.)
Further inflation was followed by an increase in resistance independent of the changes of extraalveolar vessels. This increase in vascular resistance is mainley due to decrease in transmural pressure and stretching of alveolar vessels as lung inflated.

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Patients with obstructive lung diseases have uneven distributions of ventilation and perfusion expanded overall the lungs, therefore pulmonary diffusing capacity for carbon monoxide overall the lungs is considered to be diminished. According to previous literatures, however, as for single breath method, pulmonary diffusing capacity did not decrease in bronchial asthma, bronchitis and in chronic pulmonary emphysema with % FEV _1.0 above 40per cent, in comparison with the same aged healthy.
We intended to solve this inconsistency and to investigate how does the observed value of D_LCO measured by single breath method play a role on clinical diagnosis of obstructive lung diseases. In order to perform the present investigation, at first, obstructive lung diseases were differentiated according to structural alterations in alveolo-bronchial system which provided for the worse ventilation-perfusion ratio in the lungs.
Following three problems were discussed.
1) To compare the observed values with each other according to the graded severities of chronic bronchitis, bronchial asthma and chronic pulmonary emphysema, respectively.
2) To reveal the cause of the unequality between the observed value of D_LCO measured by single breath method and the theoretical value calculated using digital computer. The latter reduces remarkably, at least on steady state, if the lungs have uneven distributions of ventilation-perfusion ratio.
3) Whether the observed value of pulmonary capillary blood volume (V_C) and membrane diffusing capacity (D_M) measured by the single breath method can coincide with the actual value in obstructive ventilatory impairments or not.
Cases investigated and their classifications
Among patients with diffuse obstructive lung diseases diagnosed making use of the selective alveolobronchography, routine bronchography, tests for airway hypersensitivity and allergen intradermal tests, in addition to their early history, symptomes, findings of chest roentgenogram and spirography etc., were 88 cases divided into following three groups of diseases according to the structural changes in alveoli and airway system.
1) group of chronic bronchitis: chronic bronchitis without emphysema but with or without minimal asthma…28 cases.
2) group of bronchial asthma: bronchial asthma without emphysema but with or without minimal bronchitis…34 cases.
3) group of chronic pulmonary emphysema: chronic pulmonary emphysema with bronchitis and with or without asthma…26 cases.
Each group was divided into three grades according to severities of diseases from the first grade to the third.
Methods of measurements and calculations
The single breath method was admitted as usual.
Results
1) Pulmonary diffusing capacity for carbon monoxide in per cent (% D_LCO)
The mean % D_LCO corrected by ages, body surface area and so on, showed the value over 100% in chronic bronchitis, bronchial asthma and chronic pulmonary emphysema respectively. The mean values of each three graded severities were not significantly different from each other in every group. In comparison with the standard of 22 years old healthy, however, the second and the third grade of chronic pulmonary emphysema showed the decrease in % D_LCO by over 30 per cents, and in cases with the first grade chronic pulmonary emphysema was % D_LCO significantly differents with the level of significance under one per cent.
The averaged age of patients were 66±6 for the second grade and 64±10 for the third grade respectively. They were considerably high aged compared with 53±8 years for the first grade, 46±11 to 47±12 for chronic bronchitis and 30±14 to 32±14 for bronchial asthma.
2) Pulmonary diffusing capacity for car

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