RESEARCH ARTICLE Influence of Different Levels of Immersion in Water on the Pulmonary Function and Respiratory Muscle Pressure in Healthy Individuals: Observational Study Armèle Dornelas de Andrade 1, * , Jader Carneiro Júnior 2,† , Talita Lourdes Lins de Barros Melo 1 , Catarina Souza Ferreira Rattes Lima 1 , Daniella Cunha Brandão 1 & Jacqueline de Melo Barcelar 1 1 Department of Physical Therapy, Universidade Federal de Pernambuco, Recife, Pernambuco Brazil 2 Department of Physical Therapy, Universidade Católica de Pernambuco, Recife, Pernambuco Brazil Abstract Background and Purpose. Immersion in water, with the head above the water line, causes acute physiological changes in the pulmonary and cardiovascular systems. The aim of this study was to evaluate the acute physiological responses to immersion on lung volumes and respiratory muscle strength at different depths. Methods. A cross- sectional study was conducted in 28 healthy individuals (21.75 ± 1.99 years; 13 men and 15 women). Anthropometric and spirometric data as well as respiratory muscle strength were evaluated. Evaluations were carried out on dry land (DL) and in a pool at three different levels of immersion: iliac crests (IC), xiphoid appendix of the sternum (XA) and clavicles (CL). The order of evaluation for spirometry and maximal inspiratory and expiratory pressures between DL and the different levels of immersion was randomized. The ANOVA test for repeated measures with post hoc Tukey was applied to compare the variables. Results. Vital capacity exhibited lower values at the CL level compared with DL, XA and IC (p < 0.01). The most significant change in forced expiratory volume in the first second (FEV 1 ) occurred under immersion at CL and XA levels. No differences in maximal expiratory pressure were found in the comparisons between the different levels of immersion and DL (p = 0.19). There was nevertheless a decrease in maximum inspiratory pressure with immersion at the CL level (91 ± 23 cmH 2 O) compared with DL (105 ± 29 cmH 2 O), XA (99 ± 24 cmH 2 O) and IC (101 ± 25 cmH 2 O) values (p < 0.01). Conclusion. The results suggest that immersion at the level of the clavicles and xiphoid appendix alters lung function and respiratory muscle strength when compared with the values measured out of the water and immersed at the IC level in healthy individuals, demonstrating the influence of hydrostatic pressure on the respiratory system. Copyright © 2013 John Wiley & Sons, Ltd. Received 22 July 2012; Revised 12 August 2013; Accepted 4 November 2013 Keywords immersion; pulmonary function test; respiratory muscle *Correspondence Armèle Dornelas de Andrade, PhD, PT, Departamento de Fisioterapia, Universidade Federal de Pernambuco. Av. Prof. Moraes Rego, 1235, Cidade Universitária, CEP: 50670–901. Recife- PE, Brazil. E-mail: armeledornelas@hotmail.com † In memoriam. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/pri.1574 Introduction Immersion in water causes acute physiological alter- ations in the cardiovascular and pulmonary systems, resulting from the action of the physical properties of water under the body surface (Pendergast and Lundgren, 2009). Such alterations can be caused by fac- tors such as water temperature, depth of immersion Physiother. Res. Int. (2013) © 2013 John Wiley & Sons, Ltd.