Cjb. Wallin et al., EFFECTS OF RAPID COLLOID VOLUME EXPANSION ON PULMONARY MICROVASCULAR PRESSURE AND LUNG WATER IN THE CONSCIOUS SHEEP, Respiration physiology, 108(3), 1997, pp. 225-231
Increased pulmonary microvascular pressure (P-mv), in combination with
other factors, may cause pulmonary interstitial oedema. Whether incre
ased P-mv alone induces alveolar oedema is questionable. In the presen
t study we used the heavy water-indocyanine green dilution method to m
easure lung water during a rapid intravascular volume expansion in the
sheep. Eight conscious sheep were given two 10-min intravenous infusi
ons of either 50 ml/kg (N = 2) or 35 ml/kg (N = 6) of dextran 60 with
an interval of 10 min between them. At a P-mv of 40 mmHg, respiratory
distress was observed in sheep no. 2 which had been given a total amou
nt of 100 ml/kg of dextran; this was immediately followed by a lethal
pulmonary haemorrhage. Mean P-mv in the remaining seven sheep increase
d to 31 (7) mmHg in response to the volume expansion without causing a
ny respiratory distress or increase in lung water. These results show
that in conscious sheep the lungs have strong protective mechanisms ag
ainst hydrostatic oedema. They do not support the hypothesis that incr
eased P-mv alone induces alveolar oedema, but suggest that an increase
in P-mv to 40 mmHg may cause stress failure of the pulmonary vasculat
ure. (C) 1997 Elsevier Science B.V.