Variation of inspiratory effort in sleep disordered breathing induces the oscillation in blood pressure, which corresponds inversely to pulse transit time (PTT). This study evaluated the feasibility of PTT as a visual parameter for differentiating respiratory events in patients with a sleep breathing disorder. Sixteen patients who complained of snoring and sleep apnea were booked into the study. Polysomnographic data of Zopiclone induced daytime sleep were analyzed, PTT and intraesophageal pressure (Peso) were assessed for each respiratory event. With respect to Peso, the total accuracy of PTT was 51.8% for 1266 events. The relatively high coincidence rate could be observed in obstructive events (57.1%), with crescendo Peso pattern (71.5%), in lateral position (82.2%). Pulse transit time oscillation could only partly reflect respiratory rhythm to some degree (56.5%). Absolute PTT value presented a poor relationship with respiratory effort. Pulse transit time coincided well with crescendo Peso in lateral position for obstructive events. Swings in PTT could only partly fit respiratory wave data. Absolute PTT value and its change could not reflect respiratory effort. Although PTT is a non-invasive and convenient way for assessing inspiratory effort, its variable sensitivity to different events, respiratory patterns, positions, different patients and other situations, limit its feasibility. Further work is required.