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 airway caliber, we hypothesized that oscillations in upper airway caliber contribute to the increased prevalence of sleep-related periodic breathing in the elderly. We tested this hypothesis by measuring upper airway resistance, ventilatory variables, and the pattern of variation of these variables in groups of body size-matched young and elderly healthy individuals during wakefulness and stage 2 non-rapid-eye-movement sleep. No major differences existed between the two groups during either wakefulness or sleep in mean upper airway resistance or ventilation values. However, ventilation was more variable during sleep in the elderly; this variability was oscillatory in the majority of elderly subjects at an average rate of 0.04 breaths/cycle or one cycle approximately every 24 s. Oscillations in upper airway resistance during sleep were associated with reciprocal oscillations in tidal volume and/or minute ventilation at the same frequency. Those subjects who had significant oscillations in upper airway resistance had more apneas and hypopneas than those subjects without such oscillations. Oscillations in resistance 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 produce a fluctuating mechanical limitation of ventilation, which may contribute to periodic breathing.