Development of ventilatory responsiveness to progressive hypoxia and hypercapnia in low-birth-weight lambs |
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Authors: | Moss, T. J. Davey, M. G. McCrabb, G. J. Harding, R. |
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Abstract: | Moss, T. J., M. G. Davey, G. J. McCrabb, and R. Harding.Development of ventilatory responsiveness to progressive hypoxia and hypercapnia in low-birth-weight lambs. J. Appl.Physiol. 81(4): 1555-1561, 1996.Our aim was todetermine the effects of low birth weight on ventilatory responses toprogressive hypoxia and hypercapnia during early postnatal life. Sevenlow-birth-weight (2.7 ± 0.3 kg) and five normal-birth-weight (4.8 ± 0.2 kg) lambs, all born at term, underwent weekly rebreathingtests during wakefulness while arterialPO2,PCO2, and pH were measured. Hypoxicventilatory responsiveness (HOVR; percent increase in ventilation whenarterial PO2 fell to 60% of resting values) increased in normal lambs from 86.6 ± 7.1% atweek 1 to 227.4 ± 24.9% atweek 6. In low-birth-weight lambs,HOVR was not significantly different at week1 (60.1 ± 18.7%) from that of normal lambs but didnot increase with postnatal age (56.6 ± 19.3% atweek 6). HOVR of all lambs at 6 wkwas significantly correlated with birth weight(r2 = 0.8).Hypercapnic ventilatory responsiveness (gradient of ventilation vs.arterial PCO2) did not change withage and was not significantly different between groups [84.7 ± 7.5 (low-birth-weight lambs) vs. 89.4 ± 6.6 ml · min1 · kg1 · mmHg1(normal lambs)]. We conclude that intrauterine conditions that impair fetal growth lead to the failure of HOVR to increase with age. |
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