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. Author manuscript; available in PMC: 2013 Jul 19.
Published in final edited form as: Pract Neurol (Fort Wash Pa). 2010 September/October;9(5):26–31.

Figure 2.

Figure 2

Portable overnight oximetry in a 69-year-old woman with amyotrophic lateral sclerosis and co-morbid obstructive sleep apnea. Numerous oscillatory desaturations are seen, especially near 11:00 PM, between 12:30 AM to 01:00 AM, following 02:00 AM, and between 03:30 AM and 04:00 AM, consistent with obstructive sleep disordered breathing. The oxygen desaturation index was only 7/hour. Note also the steep descent and oxyhemoglobin saturation nadir of 70%, due to likely superimposed REM-sleep related hypoventilation. Subsequent polysomnography confirmed moderately severe obstructive sleep apnea, with apnea-hypopnea index of 17/hour, with predominant obstructive apneic events occurring during supine and REM sleep. There was also prominent persisting oxyhemoglobin desaturation during CPAP trial during REM sleep due to hypoventilation, requiring conversion to bilevel positive airway pressure treatment with a timed back-up rate.