Background Pulse transit time (PTT) represents a noninvasive marker of sleep fragmentation in patients with obstructive sleep apnea–hypopnea syndrome (OSAHS). Little is known regarding changes in PTT in patients with excessive daytime sleepiness associated with nocturnal inspiratory flow limitation (IFL) without apneas or desaturation. Patients and methods A total of 20 patients with nocturnal IFL were age and sex matched with a group of patients with OSAHS and another without significant breathing disorders during sleep [nonflow limited (NFL)]. PTT arousal index (PTT Ar) is the number of PTT arousals per hour. Results Overall, 20 patients with IFL were age and sex matched with two groups: one with OSAHS and another without significant sleep-disordered breathing (SDB) (NFL). There was a significant increase in the median BMI of the IFL group compared with the NFL group (40 vs. 30; P0.05). The PTT Ar in the IFL group (36.5/h) was significantly higher than that in the NFL group (16.3/h) and lower than that observed in the OSAHS group (60/h; P