# Changes of pulse wave transit time after haemodynamic manoeuvres in healthy adults: a prospective randomised observational trial (PWTT volunteer study)

## TL;DR

This study explores how pulse wave transit time changes with different body maneuvers in healthy adults, suggesting it could help monitor fluid status during surgery.

## Contribution

The study demonstrates that pulse wave transit time (PWTT) can detect immediate preload changes in healthy adults through specific maneuvers.

## Key findings

- PWTT increased significantly during 'Stand-up' and decreased during passive leg raise, correlating with changes in stroke volume.
- The 'step-test' initially showed no significant PWTT change but increased arterial pressure and heart rate.
- PWTT changes after Valsalva manoeuvre were inconsistent, indicating variability in response to increased intrathoracic pressure.

## Abstract

Pulse wave transit time (PWTT) shows promise for monitoring intravascular fluid status intraoperatively. Presently, it is unknown how PWTT mirrors haemodynamic variables representing preload, inotropy, or afterload.

PWTT was measured continuously in 24 adult volunteers. Stroke volume was assessed by transthoracic echocardiography. Volunteers underwent four randomly assigned manoeuvres: ‘Stand-up’ (decrease in preload), passive leg raise (increase in preload), a ‘step-test’ (adrenergic stimulation), and a ‘Valsalva manoeuvre’ (increase in intrathoracic pressure). Haemodynamic measurements were performed before and 1 and 5 min after completion of each manoeuvre. Correlations between PWTT and stroke volume were analysed using the Pearson correlation coefficient.

‘Stand-up’ caused an immediate increase in PWTT (mean change +55.9 ms, P-value <0.0001, 95% confidence interval 46.0–65.7) along with an increase in mean arterial pressure and heart rate and a drop in stroke volume (P-values <0.0001). Passive leg raise caused an immediate drop in PWTT (mean change −15.4 ms, P-value=0.0024, 95% confidence interval −25.2 to −5.5) along with a decrease in mean arterial pressure (P-value=0.0052) and an increase in stroke volume (P-value=0.001). After 1 min, a ‘step-test’ caused no significant change in PWTT measurements (P-value=0.5716) but an increase in mean arterial pressure and heart rate (P-values <0.0001), without changes in stroke volume (P-value=0.1770). After 5 min, however, PWTT had increased significantly (P-value <0.0001). Measurements after the Valsalva manoeuvre caused heterogeneous results.

Noninvasive assessment of PWTT shows promise to register immediate preload changes in healthy adults. The clinical usefulness of PWTT may be hampered by late changes because of reasons different from fluid shifts.

German clinical trial register (DRKS, ID: DRKS00031978, https://www.drks.de/DRKS00031978).