Change in pulse wave transit time measured using ear plethysmography is a useful substitute for finger...

Plethysmography using the finger is affected by various clinical conditions, including sympathetic tone. This study aimed to evaluate whether pulse wave transit time (PWTT) calculated using ear plethysmography could be used as a substitute for finger PWTT.

In this prospective observational study, 50 patients underwent elective hepatectomy between December 2021 and April 2022. PWTT was simultaneously measured using finger and ear plethysmography. The primary outcome was the global agreement of all PWTT measurements. The secondary outcome was trending ability during hemodynamic changes.

In total, 311 paired readings from 50 patients were collected. PWTT-ear was shorter than PWTT (68.1 ± 15.1 ms). For the percent change in PWTT from baseline (%ΔPWTT), linear regression analyses showed a strong correlation between %ΔPWTT-ear and %ΔPWTT (r = 0.85, P < 0.001). In Bland-Altman analyses, the bias between %ΔPWTT-ear and %ΔPWTT was - 0.04% and limits of agreement from - 0.17 to 0.17%, with a percentage error (2 standard deviation/mean %ΔPWTT) of 4.2%. The conductance rate of the two methods was 95.9% based on a four-quadrant plot analysis. The angular conductance rate was 98.9% with a radial limit of ± 25.3 based on a polar plot analysis.

PWTT-ear was shorter than PWTT, but the % change in PWTT-ear was similar to that in PWTT. PWTT measured using ear plethysmography can be used as a substitute for measuring changes in PWTT.

This study was registered in the UMIN-CTR Clinical Database (ID: UMIN000045950), https://center6.umin.ac.jp/cgi-open-bin/icdr_e/ctr_view.cgi?recptno=R000052326 on December 08, 2021.