Improvement in VA/Q distributions during inhalation of nitric oxide in pigs with methacholine-induced bronchoconstriction.

Effects of nitric oxide (NO) and aerosolized terbutaline inhalation on ventilation-perfusion (VA/Q) distributions were determined during methacholine-induced bronchoconstriction in nine mechanically ventilated pigs. Animals inhaled, in random order, zero, 20, and 80 parts per million (ppm) of NO or aerosolized terbutaline. Inhalation of either 20 ppm NO or terbutaline produced similar reduction in pulmonary resistance and increase in lung compliance. Bronchodilation was most pronounced during inhalation of 80 ppm NO. NO inhalation increased PaO2 from 65 +/- 4 to 90 +/- 5 (20 ppm NO) and 104 +/- 6 mm Hg (80 ppm NO) (p < 0.05), and oxygen delivery (DO2) from 484 +/- 49 to 565 +/- 25 (20 ppm NO) and 619 +/- 43 ml/kg/min (80 ppm NO) (p < 0.05) compared with control. Aerosolized terbutaline did not increase PaO2 and DO2. NO inhalation accounted for a decrease in blood flow to shunt units (20 ppm NO: 14 +/- 1%, 80 ppm NO: 19 +/- 2%; p < 0.05) and an increase in the perfusion of normal VA/Q units (20 ppm NO: 12 +/- 1%, 80 ppm NO: 18 +/- 1%; p < 0.05). Perfusion of shunt and normal VA/Q units was similar in the absence of NO inhalation with and without aerosolized terbutaline. Pulmonary vascular resistance decreased from 510 +/- 55 to 332 +/- 22 dyn.s/cm5 with 20 ppm NO (p < 0.05) and to 329 +/- 41 dyn.s/cm5 with 80 ppm NO (p < 0.05) but did not change with terbutaline.(ABSTRACT TRUNCATED AT 250 WORDS)