# Sacral Microvascular Response in Older Adults Following Mechanical Loading Assessed by Photoplethysmography and Infrared Thermometry

## TL;DR

This study examines how blood flow and tissue temperature in the sacral region of older adults recover after mechanical loading, revealing individual variability influenced by factors like BMI and cardiovascular disease.

## Contribution

The study introduces a method using photoplethysmography and infrared thermometry to assess microvascular recovery and its association with individual health factors.

## Key findings

- Perfusion index is a useful indicator of microvascular recovery but shows individual variability.
- Return of blood flow is associated with BMI and cardiovascular disease diagnosis.
- Temperature recovery is linked to body temperature and baseline perfusion index.

## Abstract

Pressure injuries in institutionalized older adults with reduced mobility represent a relevant clinical problem due to their impact on quality of life and health costs. Purpose: This study aimed to describe the behavior of blood flow and tissue temperature in the sacral region and the significance of interindividual conditions in the post-load recovery of tissue in the context of pressure injuries. Methods: An observational study was conducted in 55 older adults living in a geriatric institution. Photoplethysmography and temperature signals were recorded at four times: at baseline (preload) and 15 s, 5 min, and 10 min post-load. The perfusion index was calculated, and two dichotomous variables were defined, Return b (flow) and Return t (temperature), to evaluate the physiological capacity to return to baseline conditions. Associations with clinical, functional, and diagnostic variables were explored. Results: The perfusion index showed usefulness as an indicator of microvascular recovery, but with variability between individuals. Return b was significantly associated with BMI and diagnosis of cardiovascular disease, while t-return was associated with body temperature and basal perfusion index. No significant associations were observed with sex, age or functional scales, state of consciousness, or risk of pressure injury. Conclusions: The study shows heterogeneous physiological responses to external load influenced by individual characteristics. Flow and temperature monitoring allows a functional approximation of injury risk, although more complex models are required to understand the nonlinear dynamics of tissue responses.