Background and Purpose Sleep disordered breathing (SDB) is frequent in acute stroke patients and is associated with early neurologic worsening and poor outcome. Although continuous positive airway pressure (CPAP) effectively treats SDB, compliance is low. The objective of the present study was to assess the tolerance and the efficacy of a continuous high-flow-rate air administered through an open nasal cannula (transnasal insufflation, TNI), a less-intrusive method, to treat SDB in acute stroke patients. Methods Ten patients (age, 56.8±10.7 years), with SDB ranging from moderate to severe (apnea-hypopnea index, AHI, >15/h of sleep) and on a standard sleep study at a mean of 4.8±3.7 days after ischemic stroke (range, 1-15 days), were selected. The night after, they underwent a second sleep study while receiving TNI (18 L/min).Results TNI was well tolerated by all patients. For the entire group, TNI decreased the AHI from 40.4±25.7 to 30.8± 25.7/h (p=0.001) and the oxygen desaturation index >3% from 40.7±28.4 to 31±22.5/h (p=0.02). All participants except one showed a decrease in AHI. The percentage of slow-wave sleep significantly increased with TNI from 16.7± 8.2% to 22.3±7.4% (p=0.01). There was also a trend toward a reduction in markers of sleep disruption (number of awakenings, arousal index). Conclusions TNI improves SDB indices, and possibly sleep parameters, in stroke patients. Although these changes are modest, our findings suggest that TNI is a viable treatment alternative to CPAP in patients with SDB in the acute phase of ischemic stroke.