Lung injury after heavy exercise at altitude

Lung oxidative damage by hypoxia

One of the most important functions of lungs is to maintain an adequate oxygenation in the organism. This organ can be affected by hypoxia facing both physiological and pathological situations. Exposure to this condition favors the increase of reactive oxygen species from mitochondria, as from NADPH oxidase, xanthine oxidase/reductase, and nitric oxide synthase enzymes, as well as establishing an inflammatory process. In lungs, hypoxia also modifies the levels of antioxidant substances causing pulmonary oxidative damage. Imbalance of redox state in lungs induced by hypoxia has been suggested as a participant in the changes observed in lung function in the hypoxic context, such as hypoxic vasoconstriction and pulmonary edema, in addition to vascular remodeling and chronic pulmonary hypertension. In this work, experimental evidence that shows the implied mechanisms in pulmonary redox state by hypoxia is reviewed. Herein, studies of cultures of different lung cells and complete isolated lung and tests conducted in vivo in the different forms of hypoxia, conducted in both animal models and humans, are described.

Intense hypoxic cycle exercise does not alter lung density in competitive male cyclists

We tested the hypothesis that intense short duration hypoxic exercise would result in an increase in extravascular lung water (EVLW), as evidenced by an increase in lung density. Using computed tomography (CT), baseline lung density was obtained in eight highly trained male cyclists (mean +/- SD: age = 28 +/- 8 years; height = 180 +/- 9 cm; mass = 71.6 +/- 8.2 kg; VO2max= 65.0 +/- 5.2 ml kg min(-1)). Subjects then completed an intense hypoxic exercise challenge on a cycle ergometer and metabolic data, HR and %S(p)O2 were recorded throughout. While breathing 15% O2, subjects performed five 3 km cycling intervals (mean power, 286 +/- 20 W; HR = 91 +/- 4% HRmax) separated by 5 min of recovery. From a resting hypoxic S(p)O2 of 92 +/- 4%, subjects further desaturated during exercise to 76 +/- 3%. CT scans were repeated 76 +/- 10 min (range 63-88 min) following the completion of exercise. There was no change in lung density from pre (0.18 +/- 0.02 g ml(-1)) to post-exercise (0.18 +/- 0.04 g ml(-1)). The substantial reduction in S(p)O2 may be explained by a number of potential mechanisms, including decreased pulmonary diffusion capacity, alveolar hypoventilation, reduced red cell transit time, ventilation/perfusion inequality or a temperature and pH induced rightward-shift in the oxyhaemoglobin dissociation curve. Alternatively, the integrity of the blood gas barrier may have been disrupted without any measurable increase in lung density.

Lung oxidative stress as related to exercise and altitude. Lipid peroxidation evidence in exhaled breath condensate: a possible predictor of acute mountain sickness

Lung oxidative stress (OS) was explored in resting and in exercising subjects exposed to moderate and high altitude. Exhaled breath condensate (EBC) was collected under field conditions in male high-competition mountain bikers performing a maximal cycloergometric exercise at 670 m and at 2,160 m, as well as, in male soldiers climbing up to 6,125 m in Northern Chile. Malondialdehyde concentration [MDA] was measured by high-performance liquid chromatography in EBC and in serum samples. Hydrogen peroxide concentration [H(2)O(2)] was analysed in EBC according to the spectrophotometric FOX(2) assay. [MDA] in EBC of bikers did not change while exercising at 670 m, but increased from 30.0+/-8.0 to 50.0+/-11.0 nmol l(-1) (P<0.05) at 2,160 m. Concomitantly, [MDA] in serum and [H(2)O(2)] in EBC remained constant. On the other hand, in mountaineering soldiers, [H(2)O(2)] in EBC under resting conditions increased from 0.30+/-0.12 mumol l(-1) at 670 m to 1.14+/-0.29 mumol l(-1) immediately on return from the mountain. Three days later, [H(2)O(2)] in EBC (0.93 +/-0.23 mumol l(-1)) continued to be elevated (P<0.05). [MDA] in EBC increased from 71+/-16 nmol l(-1) at 670 m to 128+/-26 nmol l(-1) at 3,000 m (P<0.05). Changes of [H(2)O(2)] in EBC while ascending from 670 m up to 3,000 m inversely correlated with concomitant variations in HbO2 saturation (r=-0.48, P<0.05). AMS score evaluated at 5,000 m directly correlated with changes of [MDA] in EBC occurring while the subjects moved from 670 to 3,000 m (r=0.51, P<0.05). Lung OS may constitute a pathogenic factor in AMS.