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Detection of uneven distribution of inspired gas in the lung and its clinical applications by single and multiple breath nitrogen washouts



Detection of uneven distribution of inspired gas in the lung and its clinical applications by single and multiple breath nitrogen washouts



Journal of Kyoto Prefectural University of Medicine 94(6): 533-554



The factors concerning the amplitude of cardiogenic oscillation (CO) detectable on the alveolar plateau of simultaneous He and N single breath washout curves in healthy subjects were analyzed with the data obtained from model experiments, and the slope of phase III (.DELTA.N2) standardized by the height of phase III (.DELTA.N2/h) in multiple breath N washout curves with vital capacity maneuver was evaluated. The differences in the amplitude of CO and in .DELTA.N2/h between healthy subjects and the patients with chronic obstructive pulmonary disease (COPD) or atrial septal defect (ASD) were compared and the detailed informations concerning with uneven distribution of inspired gas in the lung were evaluated. In model experiments, the physical principles governing gas oscillations was studied by producing the gas oscillations with a pulsatile pump and 2 bag-in-box systems. The amplitude of oscillation was affected by total flow, magnitude of pulsatile flow, the difference of N concentration between the 2 bags, and volume and shape of the dead space. In healthy subjects, the amplitude of CO was affected by expiratory flow rate without relation to inspiratory flow. In He bolus method, the volume of bolus and the lung volume at which bolus was inhaled changed the amplitude of CO. These factors must be kept constant when the amplitude of oscillation was employed for the indicator of gas distribution in the lung. The amplitude of CO in multiple breath N washout curves in patients with COPD was smaller and .DELTA.N2 was larger than that of in healthy subjects, respectively. The discrepancy might result from large intraregional and small interregional concentration differences of nitrogen in COPD contrary to those in healthy subjects. The amplitude of CO in patients with ASD whose amplitude of CO was larger than that of healthy subjects was markedly decreased after closure of ASD. Amplitude of CO must be influenced by cardiovascular pulsations in the thoracic cage. In multiple N washout curves with vital capacity maneuvers, .DELTA.N2/h was apparently increased with increase of the number of washout times. However, it ceased to increase after several washouts, and concentrated to some value which was decided by the flow contribution of the most poorly ventilated compartment and was peculiar to each subject. Uneven, distribution of inspired gas in the lung would be evaluated by using the CO and .DELTA.N2 including .DELTA.N2/h in multiple breath nitrogen washout curves. CO amplitude might indicate interregional uneven distribution of inspired gas in the lung, while .DELTA.N2 and .DELTA.N2h represent intraregional unevenness of gas in the lung independent of the amplitude of CO. The combination of these parameters must be favorable to detect in details the uneveness of distribution of inspired gas in the lung.

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Accession: 005119535

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