Influence Of Immersion In Water On Respiratory Impedance Measured By Forced Oscillation Technique

Abstract

Immersion in water decreases lung volume and maximal inspiratory muscle pressure. Previous studies have showed that hydrostatic pressure causes increased venous return from lower limbs and cranial displacement of the diaphragm, which leads to a decrease in lung compliance and increased closing volume. However, there is no research to investigate respiratory impedance during immersion in water. PURPOSE: Accordingly, the aim of this study was to evaluate respiratory impedance measured by forced oscillation technique during immersion in water in healthy adults. METHODS: Eleven healthy males participated in this cross-sectional study. We measured respiratory impedance and respiratory function before and during immersion. To compare the influence of water depths, we carried out one dry land (DL) trial and two water level trials: clavicle level (CL) and xiphoid appendix level (XA). The order of trials between DL, CL and XA was randomized and performed with at least three days rest between trials. RESULTS: Respiratory impedance: during immersion, CL (2.8 ± 0.9) and XA (2.5 ± 0.7) showed a significantly higher R5 compared to DL (1.9 ± 0.6)(p=0.005, p=0.024). CL (2.8 ± 0.7) also showed a significantly higher R20 compared to DL (2.1 ± 0.5) (p=0.003). CL (-0.5 ± 0.4) and XA (-0.3 ± 0.2) showed a significantly lower X5 than DL (-0.1 ± 0.2)(p=0.015, p=0.021). CL (9.7 ± 3.6) and XA (8.2 ± 2.4) showed a significantly higher Frequency of resonance compared to DL (5.3 ± 2.9) (p=0.007, p=0.001). Respiratory function: during immersion, Forced vital capacity (FVC) showed significantly lower values at CL (4.1 ± 0.4) compared to DL (4.4 ± 0.4) (p=0.029) and also forced expiratory volume in the first second (FEV1.0) showed a significantly lower value at CL (3.5 ± 0.5) compared to DL (3.8 ± 0.1) (p=0.01). CONCLUSIONS: Our results suggested that immersion in water, especially at the clavicle level, influences respiratory impedance and respiratory function.