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Tolerance to a haemorrhagic challenge during heat stress is improved with inspiratory resistance breathing
Author(s) -
Huang Mu,
Brothers R. Matthew,
Ganio Matthew S.,
Lucas Rebekah A. I.,
Cramer Matthew N.,
Moralez Gilbert,
Convertino Victor A.,
Crandall Craig G.
Publication year - 2018
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep087102
Subject(s) - medicine , presyncope , anesthesia , breathing , cardiology , ventilation (architecture) , airway resistance , blood pressure , respiratory system , heart rate , mechanical engineering , engineering
New FindingsWhat 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 cmH 2 O of resistance (Sham), whereas on a subsequent day the device was set at −7 cmH 2 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.