Ventilatory response to hypoxia in elderly women

The respiratory system is subject to the ageing process, which could limit its responsiveness to stimuli. Attenuation of the ventilatory response to hypoxia in old age is, as yet, an unresolved issue. Such attenuation may be germane to the pathogenesis of hypoxic respiratory disorders developing more often in elderly subjects.

The study seeks to determine the potential adverse effects of age on the hypoxic ventilatory response by comparing this response in groups of elderly and young female subjects.

Nineteen healthy women of the mean age of 71+/-1.3 (SE) years and 16 women in their twenties were required to perform a progressive isocapnic hypoxic test, based on the rebreathing technique. The ventilatory response was evaluated from the slopes of minute ventilation and mouth occlusion pressure, an index of inspiratory neuromuscular drive, against arterial oxygen saturation. The breathing pattern components also were measured with the breath-by-breath routine.

Ventilatory response to hypoxia averaged 0.65+/-0.10 L/min/% SaO(2) and neuromuscular output was 0.012+/-0.002 kPa/% SaO(2) in the elderly women and these slopes were not reduced compared with those in the young. Nor did the ventilatory slopes relate to age in the older subjects. Baseline breathing pattern was modified in the elderly in that the mean inspiratory flow was significantly higher, but it reached the same stimulated level as that in the young.

Ventilatory response to hypoxia is independent of age in healthy women. Thus, functional sensitivity of the respiratory control mechanisms does not attenuate with age.