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Respiratory muscle work limits high-intensity exercise tolerance in healthy human beings. Emerging evidence suggests similar limitations exist during submaximal work in some physically demanding occupations. In an occupational setting, heavy loads are routinely carried upon the trunk in the form of body armor, backpacks, and/or compressed air cylinders by military, emergency service, and mountain rescue personnel. This personal and respiratory protective equipment impairs respiratory muscle function and increases respiratory muscle work. More specifically, thoracic load carriage induces a restrictive ventilatory limitation which increases the elastic work of breathing, rendering the respiratory muscles vulnerable to fatigue and inducing a concomitant reduction in exercise tolerance. Similarly, breathing apparatus worn by occupational personnel, including fire fighters and military and commercial divers, increases the inspiratory elastic and expiratory resistive work of breathing, precipitating significant inspiratory and expiratory muscle fatigue and a reduction in exercise tolerance. An argument is presented that the unique respiratory challenges encountered in some occupational settings require further research, since these may affect the operational effectiveness and the health and safety of personnel working in physically demanding occupations. [ABSTRACT FROM AUTHOR]

Background: Positive pressure breathing (PPB) is commonly used in modern fighter aircraft as part of the anti-G ensemble. PPB is combined with a chest counterpressure bladder which is pressurized to the same magnitude as the breathing mask (balanced PPB). The chest counterpressure is expected to reduce the expiratory work of breathing, reduce the risk for lung rupture, and increase G tolerance. In a previous study we did not find any effect from chest counterpressure on G tolerance or G endurance. The aim of this study was to investigate the effects of chest counterpressure on the work of breathing and the risk for lung rupture. Methods: Eight male test subjects were exposed to 20-s periods of PPB at +1.0, 5.0, 6.0, 7.0, and 8.0 Gz. Each Gz level was accomplished twice, with and without pressurization of the chest bladder. Inspiratory and expiratory flows were measured and esophageal pressures were measured in the lower and upper third of the thorax. Subsequently, work and power of breathing and apical transpulmonary pressure were estimated. Results: The apical transpulmonary pressure was slightly larger without than with chest counterpressure at 1.0 Gz, while chest counter- pressure did not affect apical transpulmonary pressure at increased Gz load. Nor did the chest counterpressure affect work or power of breathing at any Gz load. Conclusion: Inflation of the chest bladder does not seem to have any effects on work or power of breathing or risk for lung rupture during PPB at high Gz loads. [ABSTRACT FROM AUTHOR]

Introduction: Prolonged +Gz-exposure eventually decreases a pilot's ability to maintain an effective anti-G straining maneuver (AGSM). Previous studies have implicated the respiratory muscles (RMs) as main contributors to this AGSM-induced fatigue. Thus, this study aimed to investigate if respiratory muscle training (RMT) may be of benefit to improve RM strength, endurance, and performance of the AGSM. Methods: Subjects (N = 14; 27 ± 5.3 yrs) trained with a commercially available RM trainer for 6 wk, 4 times/wk 20 min per session. Data collection consisted of pulmonary function tests (PETs) and a RM testing protocol simulating the AGSM. Testing occurred every 2 wk for the duration of RMT, and similarly during the 6-wk control (CON) phase where subjects did not train. The simulated AGSM performance was evaluated through measures of peak respiratory pressures, peak systolic arterial pressure (SAP), mean arterial pressure (MAP), and tidal volumes. Results: Training significantly improved (P < 0.05) RM strength after 6 wk of RMT measured in maximal expiratory pressures (RMT = 207.8 ± 15.8 cmH2O; CON = 181.3 ± 13.7 cmH2O) and maximal inspiratory pressures (RMT = -154.7 ± 8.9 cmH2O; CON = -141.9 ± 8.5 cmH2O). All other PETs were unchanged. During performance of the AGSM, only peak expiratory pressure demonstrated an increased performance benefit (RMT = 91.5 ± 5.9 cmH2O; CON = 82.8 ± 4.3 cmH2O). Peak inspiratory pressure, SAP, MAP, and tidal volumes remained unchanged. Conclusion: Without evident translation of the increased RM strength to performance of the AGSM at + 1 Gz, the benefits of RMT for ameliorating AGSM-induced fatigue within the high +Gz environment are limited. [ABSTRACT FROM AUTHOR]