Oxygen desaturation on swallowing as a potential marker of aspiration in acute stroke

We have assessed the measurement of oxygen saturation (SaO2) as a means of detecting aspiration in patients with stroke. For 10 weeks all acute stroke [AS] admissions were seen within 48 hours. Basal SaO2 was measured by pulse oximetry. Patients swallowed 10ml water while sitting up and SaO2 was noted for 2 minutes. Two control groups [young, fit (YF) and inpatient age- and sex-matched, non-neurological disease (IP)] underwent the same assessment. AS subjects underwent independent assessment of swallowing by a speech and language therapist (SLT). Exclusion criteria comprised impaired consciousness, other neurological disease and chest infection. Forty-nine AS subjects [20 men; aged 46-93 (mean 71) years], 55 YF [26 men; aged 18-55 (mean 32) years] and 65 IP [28 men; aged 53-96 (mean 71) years] were studied. Mean (SD) SaO2 fall in AS subjects [2.6 (2.9)%)] was significantly more than in YF [1.1 (0.8)%] or IP [1.1 (0.9)%]. The lower 95% confidence limit for variation in SaO2 did not differ between YF and IP (3.0% 'fall'); 19 (39%) AS subjects desaturated below this 95% lower confidence limit. Mean (SD) SaO2 fall was significantly more in SLT-graded 'aspirators' [4.6 (2.7)%] than 'nonaspirators' [1.4 (1.0)%]. We conclude that (1) a fall in SaO2 on swallowing fluid is common in patients with acute stroke; (2) the presence or absence of desaturation agrees statistically with SLT assessment of aspiration; (3) SaO2 measures may aid bedside assessment of swallowing.