Changes in Pulse Transit Time and Pulse Rate as Markers of Arousal from Sleep in Normal Subjects

Abstract

1. Obstructive sleep apnoea and its variants often provoke hundreds of short arousals that lead to the most important symptom, disabling hypersomnolence. The measurement of sleep in these conditions requires the documentation of these short arousals and this is conventionally done by manual inspection of the sleeping EEG, a laborious procedure. 2. Other markers of 'arousal', that are easier to measure and document, include several cardiovascular signals that change as part of the orienting reflex: pulse rate rise, blood pressure rise, skin vasoconstriction, for example. 3. Pulse transit time (measured as the interval from the ECG R-wave until the arrival of the pulse pressure wave at the periphery, about 250 ms) varies inversely with blood pressure and provides a beat-to-beat estimation of blood pressure changes. 4. In eight normal subjects we have assessed the relationship between transient EEG arousals of different length (provoked by external stimuli) and changes in both pulse transit time and heart rate. 5. Significant falls in pulse transit time occurred in response to external stimuli [15.1 (SEM 1.4) ms], indicating a rise in blood pressure, and were significant even when there was no discernible change in the EEG [9.9 (SEM 2.6) ms]. Significant changes in heart rate also occurred [10.3 (SEM 1.2) beats/min], but were slightly less sensitive than changes in pulse transit time. 6. Changes in pulse transit time (and to a lesser extent pulse rate) are sensitive markers of EEG arousal. As such they should be useful to include when monitoring sleep and its disorders, particularly since pulse transit time recorders can easily be made portable for home use.

Obstructive sleep apnea syndrome: effect of respiratory events and arousal on pulse wave amplitude measured by photoplethysmography in NREM sleep

“…However, the pattern of cardiovascular response was different depending on the level of arousal associated with the respiratory event, with longer arousals provoking higher PWA and HR changes. These findings are in accordance with others reports regarding the magnitude of the cardiovascular response related to changes in EEG [6,10,13,14,19,20].…”

“…EEG changes were assessed on the central EEG leads (C3-A2, C4-A1) and subdivided into three categories based on the duration of changes in EEG frequency: grade 2, shift in EEG frequency lasting >10 s and including alpha activity and/or frequencies >16 Hz, according to the standard criteria of awakening [18]; grade 1, shift in EEG frequency lasting from 3 to 10 s and including alpha activity and/or frequencies >16 Hz, except spindles, according to standard criteria of microarousal [12]; grade 0, no EEG changes or minor EEG changes, usually not classified as arousals in the ASDA criteria (i.e., shifts in EEG frequency lasting <3 s, K complexes or delta wave bursts). Similar arousal categories have been used previously for the assessment of cardiovascular responses to arousal [10,[19][20][21]. Concordance in arousal classification between the scorer and an experienced sleep technician who scored a randomly chosen subsample of 400 events was 86%.…”

“…Previous works have suggested that there could be other markers of arousal which are much easier to measure than EEG and which could assess the true extent of sleep fragmentation. This is the case for the pulse transit time, a non-invasive measure of blood pressure, a semiquantitative measure of respiratory effort [25][26][27] and a sensitive marker of autonomic arousals [20]. The recently developed peripheral arterial tonometry, based on detection of peripheral vasoconstriction, has been shown to be a sensitive marker of sympathetic arousal [28] and apneas [9,29].…”

Pulse transit time as a derived noninvasive mean to monitor arterial distensibility changes in children

“…12 PTT is generally used as an indirect measure associated with changes in the arterial wall stiffness that is in turn affected by changes in BP. [10][11][12] Documented evidences have also affirmed the potential use of PTT by demonstrating its significant correlation with oesophageal pressure in their observed variations. 12,13 From the present literature, PTT can be defined as the time taken for the arterial pulse pressure wave to travel from the left ventricle to a peripheral site, usually a finger or toe.…”

“…6,7 Pulse transit time (PTT) is a simple and noninvasive technique derived from the principle of PWV. It has shown the abilities to estimate the degree of breathing efforts in response to involuntary physiological changes in the upper airway of adults 10,11 and recently in children. 12 PTT is generally used as an indirect measure associated with changes in the arterial wall stiffness that is in turn affected by changes in BP.…”