Journal of applied physiology
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Increased intracranial pressure is suspected in the pathogenesis of acute mountain sickness (AMS), but no studies have correlated it with the presence or severity of AMS. We sought to determine whether increased optic nerve sheath diameter, a surrogate measure of intracranial pressure, is associated with the presence and severity of AMS. We performed a cross-sectional study of travelers ascending through Pheriche, Nepal (4,240 m), from March 3 to May 14, 2006. ⋯ In a multivariate logistic regression model of factors associated with AMS, optic nerve sheath diameter was strongly associated with AMS (odds ratio 6.3; 95% CI, 3.7-10.8; P < 0.001). In 10 subjects with repeat examinations, change in Lake Louise score had a strong positive correlation with change in optic nerve sheath diameter (R(2) = 0.84, P < 0.001). Optic nerve sheath diameter, a proxy for intracranial pressure, is associated with the presence and severity of AMS.
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The objective was to determine if strength training the free limb during a 3-wk period of unilateral immobilization attenuates strength loss in the immobilized limb through cross-education. Thirty right-handed participants were assigned to three groups. One group (n = 10) wore a cast and trained the free arm (Cast-Train). ⋯ Agonist muscle activation remained unchanged after the intervention for both arms [right: 302 (SD 188) to 314 (SD 176) microV; left: 261 (SD 139) to 288 (SD 151) microV] with no group differences. Strength training of the free limb attenuated strength loss in the immobilized limb during unilateral immobilization. Strength training may have prevented muscle atrophy in the immobilized limb.
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Inappropriate mechanical ventilation in patients with acute respiratory distress syndrome can lead to ventilator-induced lung injury (VILI) and increase the morbidity and mortality. Reopening collapsed lung units may significantly reduce VILI, but the mechanisms governing lung recruitment are unclear. We thus investigated the dynamics of lung recruitment at the alveolar level. ⋯ The data were accurately predicted by a mathematical model incorporating the effects of both pressure and time. Alveolar recruitment is determined by the magnitude of recruiting pressure and length of time pressure is applied, a concept supported by our mathematical model. Such a temporal dependence of alveolar recruitment needs to be considered when recruitment maneuvers for clinical application are designed.