Unexpected nocturnal hypoxia in patients with acute stroke.
BACKGROUND AND PURPOSE
Patients who have had a stroke are at risk of hypoxia through alterations in the central regulation of respiration, through aspiration, and through respiratory muscle weakness. Sleep-related breathing disorders are common and may lead to episodes of nocturnal hypoxia even when daytime oxygenation is normal. The aim of this study was to assess the prevalence of unexpected nocturnal hypoxia in stroke patients.


METHODS
Consecutive adult patients with stroke were recruited within 72 hours of admission to hospital. Patients with indications for oxygen treatment were excluded. Older adults from the local community were recruited as control subjects. Oxygenation was assessed by pulse oximetry (Minolta 3i) for 5 minutes when awake before bedtime and continuously from 11 pm until 7 am.


RESULTS
Of the 238 potentially eligible stroke patients, 120 were excluded because they required oxygen, 118 were recruited, and 100 had adequate pulse oximetry data. The mean+/-SD age was 74+/-8 years for stroke patients and 72+/-8 years for control subjects (n=85). Mean awake oxygen saturation (So2) was 94.5+/-1.7% for the stroke group and 95.8+/-1.7% for the control group (P<0.001). Mean nocturnal So2 was 93.5+/-1.9% in stroke patients and 94.3+/-1.9% in control subjects (P<0.01). Stroke patients had a higher oxygen desaturation index (ODI 4%) (8.9 versus 2.1, P<0.001). In addition, 23% of stroke patients spent >30 minutes with So2 <90% during the night.


CONCLUSIONS
Oxygen saturation at night is approximately 1% lower than when awake. Almost a quarter of stroke patients who are normoxic at screening during the day spend >30 minutes with an oxygen saturation <90%.