Journal of applied physiology
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Pressure-volume curves were obtained from excised left lungs of goats at 4, 24, and 48 h after tracheal instillation of 2.5 ml/kg of 0.1 N HCl. Air total lung capacity (TLC) at transpulmonary pressure (PL) = 35 cmH2O was 38.8 ml/kg body weight before acid, and was reduced sharply to 21.1 at 4 h, then increased to 25.6 at 24 h and 32.1 at 48 h. Excess extravascular lung water (EVLW) could account for only part of the volume reductions. ⋯ Air volume at a PL = 10 cmH2O on deflation fell from 82.0 to 72.1% TLC at 4 h, but was near control at 24 and 48 h. The reduction in ventilated volume was not reflected in proportionately increased shunt; therefore, some compensatory vasoconstriction must have occurred. We suggest that in affected regions increased surface forces, increased EVLW, and airway obstruction caused reductions of lung volume.
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Alveolar liquid pressure (Pliq) was measured by micropipettes in conjunction with a servo-nulling pressure measuring system in isolated air-inflated edematous dog lungs. Pliq was measured in lungs either washed with a detergent (0.01% Triton X-100) or subjected to refrigeration for 2-3 days followed by ventilation for 3 h. At 55% of total lung capacity (TLC, the volume at a transpulmonary pressure (Ptp) of 25 cmH2O before treatment), in both the Triton-washed and the ventilated lung, Ptp increased from 5 to 11 cmH2O, whereas Pliq, decreased from -3 to -11 cmH2O relative to alveolar air pressure. ⋯ Alveolar surface tension (T) was estimated from the Laplace equation for a spherical air-liquid interface, assuming that the radius of curvature varies as (volume)n, for -1/3 less than n less than 1/3. For uniform expansion of alveoli (n = 1/3), estimated T was 6 and 18 dyn/cm at 55 and 85% TLC, respectively, before treatment and increased to 23 and 40 dyn/cm following either Triton washing or ventilation. If pericapillary interstitial fluid pressure (Pi) equaled Pliq in edematous lungs, increases in T might reduce Pi and increase extravascular fluid accumulation in lungs made stiff by either Triton washing or cooling and ventilation using large tidal volumes.