Mechanisms of nocturnal oxyhemoglobin desaturation in children and adolescents with sickle cell disease.

Oxyhemoglobin desaturation in patients with sickle cell disease has been proposed as a possible mechanism in the initiaton of vasco-occlusive pain crises. Nocturnal oxyhemoglobin desaturation (NOD) has been described with a prevalence of up to 40% in children and adolescents with sickle cell disease. The objective of this study was to evaluate the mechanisms of nocturnal oxyhemoglobin desaturation in sickle cell disease and determine the role of obstructive sleep apnea. We performed 16-channel polysomnograms and pulmonary function testing in 20 patients with sickle cell disease (ages 7-21 years) who had documented desaturation on home oximetry studies. The median saturation awake was 94% (quartile range, 88-95). Median saturation during REM sleep was 93.5% (88-95) and during non-REM sleep 93.5% (87.5-95). The median respiratory disturbance index was low (1.35 quartile range, 0.25-2.85). Twelve patients had no obstructive apnea recorded, while 3 patients had a total of 9 or 10 episodes during the entire study. The median snoring time was 5. 65% of total sleep time (quartile range, 1.35-22.65). There was no correlation between number of obstructive apneas and mean sleeping saturation (r = 0.012, p = 0.95). There was no correlation between pulmonary function data and prevalence of NOD. There was a strong, positive correlation between sleeping and awake saturation (r = 0.96, p < 0.001). We conclude that while nocturnal oxyhemoglobin desaturation may be common in children and adolescents with sickle cell disease, upper airway obstruction does not appear to play an important role in its genesis.