Lung fluid balance, vascular permeability, and gas exchange after acid aspiration in awake goats

Lung injuries were produced by instilling 2.5 ml/kg of 0.1 N Hcl into the trachea of lightly anesthetized goats with previously implanted lung lymph fistulas. Lymph flow (Q(L)), lymph-to-plasma protein concentration ratio (L/P), pulmonary arterial and wedge pressures (Ppa, Pw), percent shunt (Qs/QT), and postmortem extravascular lung water (EVLW) were then measured for up to 48 h. Q(L) began to increase within 15 min of injury from a baseline value of 7.2 ml/h to reach a peak of 231% of base line by 1.5 h, then decreased to 160% at 24 h and returned to base line by 48 h. Average L/P increased from 0.66 to a peak of 0.73 at 2 h. Ppa increased from 17.0 cmH₂O to a first peak of 25.3 cmH₂O at 15 min, then decreased to base line by 75 min. There was a second rise that peaked at 3 h before returning to base line at 24-48 h; Pw was unchanged throughout. Qs/QT increased from 8.5 to a peak of 34% at 1 h, then decreased to 15% at 4 h, and stabilized at 17-20% at 48 h. EVLW was 237% of base line at 4 h and declined somewhat but remained elevated at 194% of base line at 24 and 48 h. Qs/QT was less than expected based on the reduction in lung volume after aspiration. We conclude that microvascular permeability was increased after acid and that a protective vasoconstriction, probably due to local hypoxia, directed blood away from nonventilated alveoli.