A small amount of inhaled nitric oxide does not increase lung diffusing capacity

¹ Dept of Anesthesia, McGill University Health Center

^* To whom correspondence should be addressed. E-mail: gerald.zavorsky{at}mcgill.ca.

	Abstract

To determine (a) whether 40-50 ppm nitric oxide increases lung diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO), membrane diffusing capacity for CO (DmCO) and pulmonary capillary blood volume (Vc); (b) the actual number of tests required to provide a reasonable estimate of DLNO, DLCO, DmCO, and Vc; (c) repeatability of these parameters using the single-breath DLNO-DLCO method.

31 healthy subjects performed 5 single-breath hold maneuvers at rest inhaling 43±3 ppm NO and a standard diffusion mixture.

DLNO (DmCO) remained unchanged from the first to fifth trial. However, compared to the first trial, DLCO and Vc decreased by the fourth (-4±5%; 95% CI= -5 to -2%; P<0.05) and third trial (-5±7%; 95% CI= -7 to -2%; P<0.05), respectively. Repeatability over 5 trials was 17, 3 and 7 mL·min^-1·mmHg^-1 for DLNO, DLCO and DmCO, respectively, and 13 mL for Vc when DmCO=DLNO/2.42

Nitric oxide inhaled during sequential single-breath maneuvers has no effect on DLNO and thus DmCO. Since more than two and three trials will lower Vc and DLCO, respectively, the average value of only two trials are suggested.

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