Sr. Hopkins et al., EFFECTS OF INHALED NITRIC-OXIDE ON GAS-EXCHANGE IN LUNGS WITH SHUNT OR POORLY VENTILATED AREAS, American journal of respiratory and critical care medicine, 156(2), 1997, pp. 484-491
Citations number
24
Categorie Soggetti
Emergency Medicine & Critical Care","Respiratory System
Inhaled nitric oxide (NO) is a selective pulmonary vasodilator with be
neficial effects on some lung diseases, yet conflicting results, parti
cularly in chronic obstructive pulmonary disease, have been reported.
We hypothesized that although inhaled NO would improve gas exchange in
the presence of shunt (by increasing blood flow to normal areas), it
could worsen gas exchange when areas of low ventilation-perfusion ((V)
over dot A/(Q) over dot) ratio were present since these areas could b
e preferentially vasodilated by NO. We examined how similar to 80 ppm
inhaled NO altered pulmonary gas exchange in anesthetized ventilated d
ogs with the following: (1) normal lungs (n = 8), (2) shunt (n = 9, 24
.7% shunt) produced by complete obstruction of one lobar bronchus, and
(3) (V) over dot A/(Q) over dot inequality (n = 8) created by partial
obstruction of one lobar bronchus resulting in a bimodal (V) over dot
A/(Q) over dot distribution with 13% perfusion of low (V) over dot A/
(Q) over dot areas (0.005 < (V) over to A/(Q) over dot < 0.1) without
shunt. Inhaled No significantly reduced pulmonary arterial (p < 0.001)
and wedge pressures (p < 0.01) and pulmonary vascular resistance (p <
0.01) without changing cardiac output in each group. In normal lungs,
NO did not alter Pa-O2 or (V) over dot A/(Q) over dot inequality. How
ever, with complete obstruction, shunt fell slightly (p < 0.001) with
NO. In lungs with (V) over dot A(Q) over dot inequality, NO variably a
ffected (V) over dot A/(Q) over dot matching, which was improved in so
me dogs and worsened in others. In these lungs, changes in pulmonary v
ascular resistance of the abnormal area of the lung were negatively co
rrelated with changes in (V) over dot A/(Q) over dot dispersion (logSD
(Q) over dot) (R = -0.85, p < 0.01) and positively correlated with Pa-
O2 (R = 0.79, p < 0.05). We conclude that NO has net effects on pulmon
ary gas exchange, depending on the underlying lung pathology consisten
t with competing vasodilatory effects on the normal and abnormal areas
that receive the gas.