Changes in lung mechanics induced by acute isocapnic hypoxia

Abstract

We measured lung mechanics in seven healthy males during acute isocapnic hypoxia (PAO2 = 40-50 Torr; PACO2 = 38-42 Torr). Hypoxia was accompanied by increases in total lung capacity (mean increase +/- SD; 0.40 +/- 0.24 liters; P less than 0.005) functional residual capacity (0.34 +/- 0.25 liters; P less than 0.01) and residual volume (0.56 +/- 0.44 liters; P less than 0.02) in all subjects. Specific conductance of the lung decreased during hypoxia (P less than 0.02). The static deflation pressure-volume curve of the lung was shifted upward during hypoxia in all subjects. Resting end-expiratory recoil pressure of the lung was slightly, but not significantly lower during hypoxtic expiratory lung compliance was greater during hypoxia (0.39 +/- 0.04 l/cmH2O) than control measurements (0.31 +/- 0.05 l/cmH2O; P less than 0.005). No change was noted in dynamic lung compliance. All changes in lung mechanics were reversed within three minutes of reoxygenation. We conclude that acute isocapnic hypoxia increases total lung capacity in man and suggest that this may be due to the effect of hypoxia on the airways and pulmonary circulation.

Respiratory function and blood gas variables in cystic fibrosis patients during reduced environmental pressure

“…In animals inspiratory hypoxia has a direct impact on the tone of bronchial smooth muscles resulting in an increase in airway resistance (D'Brot and Ahmed 1991;Dewachter et al 1992), whereas inspiratory hyperoxia induced slight bronchodilation (D'Brot and Ahmed 1991;Libby et al 1981;Murchie et al 1993). In healthy subjects, a slight hypoxia-induced increase in airway resistance was observed whereby pronounced inter-individual differences were found (Dillard et al 1998;Saunders et al 1977;Teague et al 1988). In the present study, a very slight reduction in airway resistance was found in healthy control subjects with reduced environmental pressure (Fig.…”

“…Inspiratory hypoxia has impact on the tone of the bronchial smooth muscles resulting in hypoxia-induced bronchoconstriction accompanied by an increase in airway resistance (D'Brot and Ahmed 1991;Dewachter et al 1992;Saunders et al 1977;Teague et al 1988) and, conversely, inspiratory hyperoxia reduces the hypoxiainduced increase in pulmonary resistance (D'Brot and Ahmed 1991;Murchie et al 1993). This study followed changes in blood gases in arterialized capillary blood and lung function in CF patients under moderate inspiratory isocapnic hypoxia by hypobaric conditions.…”

Thoracoabdominal motion during progressive isocapnic hypoxia in conscious man.

“…Therefore, qualitative or quantitative differences between hypoxia and hypercapnic-induced alterations in lung mechanics could explain, in part, the contrasts observed in these studies. Early investigations indicated that hypoxia causes bronchoconstriction and increases in lung volume, in particular residual volume and functional residual capacity (Nadel & Widdicombe, 1962;Green & Widdicombe, 1966;Sterling, 1968a;Garfinkel & Fitzgerald, 1975;Saunders, Betts, Pengelly & Rebuck, 1977 (Kellogg & Mines, 1975;Goldstein, Zamel & Rebuck, 1979). It is more generally accepted that hypercapnia can decrease airway resistance (Sterling, 1968a) although its effect on lung volume is less clear.…”

Effects of nutrition, growth hormone disturbances, training, altitude and sleep on lung volumes

“…A reasonable summary is that, on average, VC decreases (about 200 mL in adults) and TLC and RV increase with the initial exposure to altitude but return to baseline values within a month [63,75,76].…”