# Pulse Waveform Changes During Vasopressor Therapy Assessed Using Remote Photoplethysmography: A Case Series

## TL;DR

This study shows that remote photoplethysmography can detect changes in pulse waveforms during vasopressor treatment in septic shock patients.

## Contribution

The study demonstrates the feasibility of using rPPG to monitor vascular tone and microcirculation during norepinephrine therapy.

## Key findings

- Higher norepinephrine doses correlated with increased MAP and perfusion index.
- Dicrotic notch and diastolic wave amplitudes decreased consistently with vasopressor use.
- rPPG changes aligned with macrocirculatory stabilization and altered arterial compliance.

## Abstract

Background/Objectives: Septic shock involves severe circulatory and microcirculatory dysfunction and often requires vasopressors to maintain adequate mean arterial pressure (MAP). Conventional monitoring mainly reflects macrocirculation and may not capture changes in vascular tone or microcirculation. Remote photoplethysmography (rPPG) is a contactless optical method that analyzes peripheral pulse waveforms and may offer additional physiological insight during vasopressor therapy. The aim of this study was to assess the feasibility of rPPG for detecting pulse waveform changes associated with norepinephrine administration in septic shock. Methods: Prospective case series included three adult patients (n = 3) with septic shock admitted to the intensive care unit at Pauls Stradins Clinical University Hospital, Riga, Latvia. All patients received standard sepsis treatment, including fluid resuscitation and titrated norepinephrine to maintain MAP ≥ 65 mmHg. Continuous invasive arterial pressure monitoring was performed alongside rPPG signal acquisition from the palmar skin surface under controlled lighting. From averaged rPPG waveforms, perfusion index (PI), dicrotic notch amplitude (c-wave), and diastolic wave amplitude (d-wave) were extracted. Correlations between norepinephrine dose, MAP, and rPPG parameters were explored. Results: Increasing norepinephrine doses were associated with higher MAP and PI in all patients. Dicrotic notch and diastolic wave amplitude decreased consistently. These changes occurred alongside macrocirculatory stabilization and are consistent with increased vascular tone and altered arterial compliance. Conclusions: rPPG demonstrated feasibility for detecting pulse waveform changes during norepinephrine therapy in septic shock; however, larger controlled studies are required for validation.