Journal of applied physiology
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We devised a new method for measuring esophageal pressure (Pes) with use of a flexible tube without a balloon at a constant rate of airflow through the tube into the esophagus (balloonless method). A study with 133Xe showed that the air that accumulated in the esophagus did not interfere with the measurement of Pes. We measured dynamic compliance (Cdyn) and pulmonary resistance (RL) with the balloonless method in 19 subjects and obtained a static deflation pressure-volume curve (P-V curve) in 10 other subjects. ⋯ K, the index of compliance in the exponential function V = V0(1-e-KP) where V0 is volume at infinite pressure, was 0.136 +/- 0.040 cmH2O-1 with the balloonless method and 0.153 +/- 0.023 cmH2O-1 with the balloon method. No statistically significant difference was found between these two values. In conclusion, Cdyn, RL, and the P-V curve can be obtained precisely with the balloonless method.
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In the present human study we evaluated a newly developed double-indicator-dilution densitometric system for the estimation of cardiac output (Q), central blood volume (CBV), and extravascular lung water (EVLW) by using indocyanine green and heavy water (2H2O) as indicators. Eighteen cardiopulmonary healthy patients scheduled for abdominal surgery were studied. ⋯ During the whole study EVLW (3.8 +/- 0.9 ml/kg) was stable in the presence of large fluctuations in Q (2.5-10.1 l/min) and CBV (0.8-2.4 l). We concluded that the method is versatile and of low invasiveness, allowing reliable on-line Q and EVLW data for repeated measurements in the clinical setting.
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A theoretical model (Hahn et al. J. Appl. ⋯ Close agreement was found between single-breath and sinusoid airway dead space measurements (mean difference 15 +/- 6%, 95% confidence limit), N2 washout and sinusoid alveolar volume (mean difference 4 +/- 6%, 95% confidence limit), and thermal dilution and sinusoid pulmonary blood flow (mean difference 12 +/- 11%, 95% confidence limit). The application of 1 kPa positive end-expiratory pressure increased airway dead space by 12% and alveolar volume from 0.8 to 1.1 liters but did not alter pulmonary blood flow, as measured by both the sinusoid and comparator techniques. Our findings show that the noninvasive sinusoid technique can be used to measure cardiorespiratory lung function and allows changes in function to be resolved in 2 min.