Inhaled nitric oxide for high-altitude pulmonary edema.
BACKGROUND
Pulmonary hypertension is a hallmark of high-altitude pulmonary edema and may contribute to its pathogenesis. When administered by inhalation, nitric oxide, an endothelium-derived relaxing factor, attenuates the pulmonary vasoconstriction produced by short-term hypoxia.


METHODS
We studied the effects of inhaled nitric oxide on pulmonary-artery pressure and arterial oxygenation in 18 mountaineers prone to high-altitude pulmonary edema and 18 mountaineers resistant to this condition in a high altitude laboratory (altitude, 4559 m). We also obtained lung-perfusion scans before and during nitric oxide inhalation to gain further insight into the mechanism of action of nitric oxide.


RESULTS
In the high-altitude laboratory, subjects prone to high-altitude pulmonary edema had more pronounced pulmonary hypertension and hypoxemia than subjects resistant to high-altitude pulmonary edema. Arterial oxygen saturation was inversely related to the severity of pulmonary hypertension (r=-0.50, P=0.002). In subjects prone to high-altitude pulmonary edema, the inhalation of nitric oxide (40 ppm for 15 minutes) produced a decrease in mean (+/-SD) systolic pulmonary-artery pressure that was three times larger than the decrease in subjects resistant to such edema (25.9+/-8.9 vs. 8.7+/-4.8 mm Hg, P<0.001). Inhaled nitric oxide improved arterial oxygenation in the 10 subjects who had radiographic evidence of pulmonary edema (arterial oxygen saturation increased from 67+/-10 to 73+/-12 percent, P=0.047), whereas it worsened oxygenation in subjects resistant to high-altitude pulmonary edema. The nitric oxide-induced improvement in arterial oxygenation in subjects with high-altitude pulmonary edema was accompanied by a shift in blood flow in the lung away from edematous segments and toward nonedematous segments.


CONCLUSIONS
The inhalation of nitric oxide improves arterial oxygenation in high-altitude pulmonary edema, and this beneficial effect may be related to its favorable action on the distribution of blood flow in the lungs. A defect in nitric nitric oxide synthesis may contribute to high-altitude pulmonary edema.
Scherrer
U
U
Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
Vollenweider
L
L
Delabays
A
A
Savcic
M
M
Eichenberger
U
U
Kleger
G R
GR
Fikrle
A
A
Ballmer
P E
PE
Nicod
P
P
Bärtsch
P
P
D000280:Administration, Inhalation; D000328:Adult; D000532:Altitude Sickness / Q000150:complications; D002245:Carbon Dioxide / Q000032:analysis; D015150:Echocardiography, Doppler; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications / Q000000981:diagnostic imaging / Q000188:drug therapy; D008168:Lung / Q000098:blood supply / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000627:therapeutic use*; D010100:Oxygen / Q000097:blood; D011654:Pulmonary Edema / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D011859:Radiography; D011877:Radionuclide Imaging
D002245:Carbon Dioxide; D009569:Nitric Oxide; D010100:Oxygen