Effect of upper airway obstruction on blood pressure variability after stroke

Approx. 60% of acute stroke patients have periods of significant UAO (upper airway obstruction) and this is associated with a worse outcome. UAO is associated with repeated fluctuation in BP (blood pressure) and increased BP variability is also associated with a poor outcome in patients with acute stroke. UAO-induced changes in BP, at a time when regional cerebral perfusion is pressure-dependent in areas of critically ischaemic brain, could explain the detrimental effect of UAO on outcome in these patients. The aim of the present study was to examine the relationship between UAO and BP variability in patients with acute stroke. Twelve acute stroke patients and 12 age-, sex- and BMI (body mass index)-matched controls underwent a sleep study with non-invasive continuous monitoring of BP to assess the impact of UAO on BP control after stroke. Stroke patients had significantly more 15 mmHg dips in BP/h than the controls (51 compared with 6.7 respectively; P<0.004). Stroke patients also demonstrated significantly higher BP variability than the controls (26.8 compared with 14.4 mmHg; P<0.001). There were significantly more 15 mmHg dips in BP/h in stroke patients who had significant UAO than those who did not (85.7 compared with 29.5 respectively; P<0.032). Furthermore, stroke patients without UAO (RDI <10, where RDI is respiratory disturbance index) had significantly more 15 mmHg dips in BP/h than the controls (29.5 compared with 6.7 respectively; P<0.037). There was a positive correlation between the severity of UAO (RDI) and 15 mmHg dips in BP/h (r=0.574, P<0.005) in stroke patients. Our results suggest that UAO alone does not explain BP variation post-stroke, but it does play an important role, particularly in determining the severity of the BP fluctuation.