Objective: Investigation of the role of sleep states on the respiratory effort of controls and subjects with upper airway resistance syndrome (UARS) using nasal cannula/pressure transducer system and esophageal manometry.
Patients and methods: One night's monitoring of sleep and breathing, including the determination of peak end inspiratory esophageal pressure (respiratory effort) with esophageal manometry and flow limitation with nasal cannula. Analysis of the data, breath-by-breath, using visual inspection and a computerized program. Setting - a university sleep laboratory. Patients were nine men with UARS and nine control men matched for age, ethnicity, and body mass index.
Results: A modulation of respiratory effort by sleep state and stages is seen in all subjects, the lowest noted during REM sleep and the highest associated with Slow Wave Sleep. When total nocturnal breaths are investigated, a significant difference between peak end inspiratory esophageal pressure [(Pes)-considered as an index of respiratory effort] is noted between normal subjects and UARS. Two specific breathing patterns, seen primarily in UARS patients, are NREM sleep stage dependent. Crescendos (defined as more negative peak end inspiratory Pes with each successive abnormal breath) occur mostly during stages 1-2 NREM sleep, while segments consisting of regular and continuous, breath-after-breath, high respiratory efforts are associated with Slow Wave Sleep. Depending on sleep stage, visually scored arousal response displays differences in Pes negativity. The termination of the abnormal breathing pattern, always well defined with Pes, is not necessarily associated with a pattern of 'flow limitation' at the nasal cannula tracing, even when a visually scored EEG arousal is present.
Conclusions: UARS patients have significantly more breaths, with more negative peak end inspiratory Pes, than do control subjects. The modulation of peak end inspiratory Pes (an index of respiratory effort) by sleep stage and state differs in UARS patients and control subjects. The nasal cannula/pressure transducer system may not detect all abnormal breathing pattern during sleep. As indicated by the visual sleep scoring, repetitive arousals may lead to more or less severe sleep fragmentation.