Can Pulse Transit Time Be Useful for Detecting Hypertension in Patients in a Sleep Unit

Abstract Introduction Pulse transit time (PTT) is the time that a pulse wave takes to travel between two different arterial points, and may be useful in estimating blood pressure. This noninvasive technique, which does not add any cost to the procedure, offers the advantage of avoiding ‘arousals’ during sleep measurement as it occurs with ambulatory blood pressure monitoring (ABPM). We aim to confirm the usefulness of PTT for the detection of hypertension, and to study the correlation between both the measurements. Methods Prospective observational study in a multidisciplinary sleep unit. We recruited 30 consecutive patients attending a sleep clinic and ran a baseline polysomnography followed by an ABPM the following day. Average systolic and diastolic blood pressure (SBP, DBP) by PTT were calculated and compared with ABMP results. In accordance with international guidelines, patients with mean nocturnal ABMP≥120/70 mmHg were diagnosed as having arterial hypertension. Results Mean age was of 60 years; 66% were male, of whom 80% suffered from sleep apnoea (OSAS). Taking the ABPM as the reference technique, we found that the diagnostic sensitivity of PTT is 85% with a specificity of 88% in the case of SBP, with a positive predictive value of 85% and negative predictive value of 88%. By studying the relationship between mean SBP measured by ABPM and PTT, we found a linear correlation coefficient ( R ) of 0.88, showing a distribution of all subjects with a difference of ±15 mmHg between the tests. There is also a positive correlation between mean DBP measured for the two tests and with a weaker linear correlation. Conclusions Pulse transit time shows a strong correlation with blood pressure (measured by ABPM). PTT provides continuous, non-invasive, cuffless blood pressure monitoring free of additional cost and could be an alternative for screening hypertension.