Mu Huang1,2, R Matthew Brothers3, Matthew S Ganio4, Rebekah A I Lucas5, Matthew N Cramer1,6, Gilbert Moralez1,6, Victor A Convertino7, Craig G Crandall1,6. 1. Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA. 2. Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA. 3. Department of Kinesiology, University of Texas, Arlington, Arlington, TX, USA. 4. Department of Health, Human Performance and Recreation, University of Arkansas, Fayetteville, AR, USA. 5. School of Sport, Exercise & Rehabilitation Sciences, The University of Birmingham, Edgbaston, Birmingham, UK. 6. Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA. 7. US Army Institute of Surgical Research, Fort Sam Houston, TX, USA.
Abstract
NEW FINDINGS: What is the central question of this study? Does inspiratory resistance breathing improve tolerance to simulated haemorrhage in individuals with elevated internal temperatures? What is the main finding and its importance? The main finding of this study is that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress. These findings demonstrate a scenario in which exploitation of the respiratory pump can ameliorate serious conditions related to systemic hypotension. ABSTRACT: Heat exposure impairs human blood pressure control and markedly reduces tolerance to a simulated haemorrhagic challenge. Inspiratory resistance breathing enhances blood pressure control and improves tolerance during simulated haemorrhage in normothermic individuals. However, it is unknown whether similar improvements occur with this manoeuvre in heat stress conditions. In this study, we tested the hypothesis that inspiratory resistance breathing improves tolerance to simulated haemorrhage in individuals with elevated internal temperatures. On two separate days, eight subjects performed a simulated haemorrhage challenge [lower-body negative pressure (LBNP)] to presyncope after an increase in internal temperature of 1.3 ± 0.1°C. During one trial, subjects breathed through an inspiratory impedance device set at 0 cmH2 O of resistance (Sham), whereas on a subsequent day the device was set at -7 cmH2 O of resistance (ITD). Tolerance was quantified as the cumulative stress index. Subjects were more tolerant to the LBNP challenge during the ITD protocol, as indicated by a > 30% larger cumulative stress index (Sham, 520 ± 306 mmHg min; ITD, 682 ± 324 mmHg min; P < 0.01). These data indicate that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress.
NEW FINDINGS: What is the central question of this study? Does inspiratory resistance breathing improve tolerance to simulated haemorrhage in individuals with elevated internal temperatures? What is the main finding and its importance? The main finding of this study is that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress. These findings demonstrate a scenario in which exploitation of the respiratory pump can ameliorate serious conditions related to systemic hypotension. ABSTRACT: Heat exposure impairs human blood pressure control and markedly reduces tolerance to a simulated haemorrhagic challenge. Inspiratory resistance breathing enhances blood pressure control and improves tolerance during simulated haemorrhage in normothermic individuals. However, it is unknown whether similar improvements occur with this manoeuvre in heat stress conditions. In this study, we tested the hypothesis that inspiratory resistance breathing improves tolerance to simulated haemorrhage in individuals with elevated internal temperatures. On two separate days, eight subjects performed a simulated haemorrhage challenge [lower-body negative pressure (LBNP)] to presyncope after an increase in internal temperature of 1.3 ± 0.1°C. During one trial, subjects breathed through an inspiratory impedance device set at 0 cmH2 O of resistance (Sham), whereas on a subsequent day the device was set at -7 cmH2 O of resistance (ITD). Tolerance was quantified as the cumulative stress index. Subjects were more tolerant to the LBNP challenge during the ITD protocol, as indicated by a > 30% larger cumulative stress index (Sham, 520 ± 306 mmHg min; ITD, 682 ± 324 mmHg min; P < 0.01). These data indicate that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress.
Authors: C G Crandall; T E Wilson; J Marving; M Bundgaard-Nielsen; T Seifert; T L Klausen; F Andersen; N H Secher; B Hesse Journal: J Physiol Date: 2012-01-04 Impact factor: 5.182
Authors: Victor A Convertino; Kathy L Ryan; Caroline A Rickards; Steven L Glorsky; Ahamed H Idris; Demetris Yannopoulos; Anja Metzger; Keith G Lurie Journal: Respir Care Date: 2011-02-11 Impact factor: 2.258
Authors: Victor A Convertino; Kathy L Ryan; Caroline A Rickards; William H Cooke; Ahamed H Idris; Anja Metzger; John B Holcomb; Bruce D Adams; Keith G Lurie Journal: Crit Care Med Date: 2007-04 Impact factor: 7.598