PATTERN OF BREATHING AND UPPER AIRWAY MECHANICS DURING WAKEFULNESS AND SLEEP IN HEALTHY ELDERLY HUMANS

Elderly subjects are known to be prone to periodic breathing in sleep. Because periodic breathing may be associated with changes in upper ai rway caliber, we hypothesized that oscillations in upper airway calibe r contribute to the increased prevalence of sleep-related periodic bre athing in the elderly. We tested this hypothesis by measuring upper ai rway resistance, ventilatory variables, and the pattern of variation o f these variables in groups of body size-matched young and elderly hea lthy individuals during wakefulness and stage 2 non-rapid-eye-movement sleep. No major differences existed between the two groups during eit her wakefulness or sleep in mean upper airway resistance or ventilatio n values. However, ventilation was more variable during sleep in the e lderly; this variability was oscillatory in the majority of elderly su bjects at an average rate of 0.04 breaths/cycle or one cycle approxima tely every 24 s. Oscillations in upper airway resistance during sleep were associated with reciprocal oscillations in tidal volume and/or mi nute ventilation at the same frequency. Those subjects who had signifi cant oscillations in upper airway resistance had more apneas and hypop neas than those subjects without such oscillations. Oscillations in re sistance and ventilation occurred in the supine but not in the lateral body position. We conclude that the wide oscillations in upper airway resistance present during sleep in supine healthy elderly subjects pr oduce a fluctuating mechanical limitation of ventilation, which may co ntribute to periodic breathing.