Sleep apnoea in patients with quadriplegia

Background - This study was undertaken to establish the prevalence of, and the factors contributing towards, sleep disordered breathing in patients with quadriplegia. Methods - Forty representative quadriplegic patients (time since injury >6 months, injury level C8 and above, Frankel category A, B, or C; mean (SE) age 35 0 (1.7) years) had home sleep studies in which EEG, EOG, submental EMG, body movement, nasal airflow, respiratory effort, and pulse oximetry (Spo₂) were measured. Patients reporting post traumatic amnesia of >24 hours, drug or alcohol abuse or other major medical illness were excluded from the study. A questionnaire on medications and sleep was administered and supine blood pressure, awake SPO2, spirometric values, height, and neck circumference were measured. Results - A pattern of sustained hypoventilation was not observed in any of the patients. Sleep apnoeas and hypopnoeas were, however, common. Eleven patients (27.5%) had a respiratory disturbance index (RDI, apnoeas plus hypopnoeas per hour of sleep) of ≥ 15, with nadir SPO₂ ranging from 49% to 95%. Twelve of the 40 (30%) had an apnoea index (Al) of ≥ 5 and, of these, nine (75%) had predominantly obstructive apnoeas - that is, >80% of apnoeas were obstructive or mixed. This represents a prevalence of sleep disordered breathing more than twice that observed in normal populations. For the study population RDI correlated with systolic and diastolic blood pressure and neck circumference. RDI was higher in patients who slept supine compared with those in other postures. Daytime sleepiness was a common complaint in the study population and sleep architecture was considerably disturbed with decreased REM sleep and increased stage 1 non-REM sleep. Conclusions-Sleep disordered breathing is common in quadriplegic patients and sleep disturbance is significant. The predominant type ofapnoea is obstructive. As with non-quadriplegic patients with sleep apnoea, sleep disordered breathing in quadriplegics is associated with increased neck circumference and the supine sleep posture.