Assessment of high altitude tolerance in healthy individuals.

The most reliable prediction of high altitude tolerance can be derived from the clinical history of previous comparable exposures. Unfortunately, there are no reliable tests for prediction prior to first-time ascents. Although susceptibility to AMS is usually associated with a low hypoxic ventilatory response (HVR), there is too much overlap with the range of normal values, which precludes measuring HVR or O(2) saturation during brief hypoxia for reliable identification of susceptibility to AMS.

Lung diffusing capacity and exercise in subjects with previous high altitude pulmonary oedema.

Subjects with a history of high-altitude pulmonary oedema (HAPE) have increased pulmonary artery pressure and more ventilation-perfusion (V'A/Q') inhomogeneity with hypoxia and exercise. We used noninvasive methods to determine whether there are differences in the pulmonary diffusing capacity for carbon monoxide (DL,CO) and cardiac output (Q') during exercise, indicative of a more restricted pulmonary vascular bed in subjects with a history of HAPE. Eight subjects with radiographically documented HAPE and five controls with good altitude tolerance had standard pulmonary function testing and were studied during exercise at 30 and 50% of normoxic maximal oxygen consumption (V'O2) at an inspiratory oxygen fraction of 0.

Ventilatory and pulmonary vascular response to hypoxia and susceptibility to high altitude pulmonary oedema.

Reduced tolerance to high altitude may be associated with a low ventilatory and an increased pulmonary vascular response to hypoxia. We therefore, examined whether individuals susceptible to acute mountain sickness (AMS) or high altitude pulmonary oedema (HAPE) could be identified by noninvasive measurements of these parameters at low altitude. Ventilatory response to hypoxia (HVR) and hypercapnia (HCVR) at rest and during exercise, as well as hypoxic pulmonary vascular response (HPVR) at rest, were examined in 30 mountaineers whose susceptibility was known from previous identical exposures to high altitude.

Endothelin-1 in pulmonary hypertension associated with high-altitude exposure.

Background: Endothelin-1 is involved in chronic pulmonary hypertension. Its role in acute pulmonary hypertension due to hypoxia in humans is not clear. We therefore studied the influence of hypoxia caused by exposure to high altitude on plasma endothelin-1 levels, arterial blood gases, and pulmonary arterial pressure in subjects taking nifedipine or placebo.

Nifedipine does not prevent acute mountain sickness.

Nifedipine has been shown effective for prevention and treatment of high altitude pulmonary edema (HAPE). Because acute mountain sickness (AMS) and HAPE may share common pathophysiologic mechanisms, we evaluate the prophylactic effect of nifedipine on the development of AMS in 27 mountaineers not susceptible to HAPE. They were randomly assigned to receive in a double-blind manner either nifedipine or placebo during rapid ascent to 4559 m and a subsequent three-day sojourn at this altitude.

Autogenously lined skeletal muscle ventricles in circulation. Up to nine months' experience.

Skeletal muscle ventricles were constructed in fifteen dogs. After a delay period of 4 weeks the skeletal muscle ventricles were connected to the descending thoracic aorta with a polytetrafluoroethylene bifurcation graft (Gore-Tex bifurcation graft, W.L.

Skeletal muscle ventricles: a promising treatment option for heart failure.

Our most recent work on cardiac assist with canine latissimus dorsi muscle in a skeletal muscle ventricle (SMV) configuration is reported here. One animal's SMV has been pumping blood effectively in the circulation for more than 16 months. To date there is no evidence of thromboembolism, and the dog has suffered no untoward effects.

Canine latissimus dorsi cardio-double myoplasty: acute feasibility study.

Cardio-double myoplasty was performed in eight mongrel dogs. Both latissimus dorsi muscles were dissected from the chest wall and wrapped around the heart. They were then stimulated using an R wave synchronous stimulator.

Skeletal muscle ventricles for total heart replacement.

Skeletal muscle ventricles (SMV) were constructed from canine left latissimus dorsi muscle. The animals were divided into three groups: group A (n = 5), SMVs rested 4 weeks without electrical conditioning; group B (n = 6), SMVs rested 4 weeks and then electrically conditioned for 6 weeks; group C (n = 5), SMVs rested 18 weeks without electrical conditioning. At the end of each protocol, the SMVs were acutely tested by connecting them to a mock-circulation device.

Skeletal muscle ventricles in circulation as aortic diastolic counterpulsators: twelve-month update.

In previous studies, we have shown that canine skeletal muscle ventricles (SMVs) of various designs could develop stroke work intermediate between that of the canine left and right ventricle. We have subsequently reported that SMVs could be used as aortic diastolic counterpulsators. In some animals the SMVs pumped blood effectively for several weeks.