Work of breathing is increased during exercise with the self-contained breathing apparatus regulator

Scott J. Butcher; Richard L. Jones; Neil D. Eves; Stewart R. Petersen

doi:10.1139/h06-073

Work of breathing is increased during exercise with the self-contained breathing apparatus regulator

Applied Physiology Nutrition and Metabolism ◽

10.1139/h06-073 ◽

2006 ◽

Vol 31 (6) ◽

pp. 693-701 ◽

Cited By ~ 23

Author(s):

Scott J. Butcher ◽

Richard L. Jones ◽

Neil D. Eves ◽

Stewart R. Petersen

Keyword(s):

Work Of Breathing ◽

The Self ◽

Healthy Male ◽

Lung Volumes ◽

Low Resistance ◽

Breathing Apparatus ◽

Esophageal Balloon ◽

Ventilation Rates ◽

Male Subjects ◽

Body Plethysmograph

The self-contained breathing apparatus (SCBA) increases the expiratory pressure required to maintain high rates of ventilation, suggesting that the expiratory work of breathing (WOB) is increased; however, this has never been reported. The objective of this study, therefore, was to determine if the WOB is increased with the SCBA regulator (BA condition) compared with a low-resistance breathing valve (RV condition) during exercise. Twelve healthy male subjects underwent two randomized exercise trials, consisting of cycling at 150, 180, 210, and 240 W. Inspired and expired tidal volumes were measured using a body plethysmograph, whereas esophageal pressures were measured with an esophageal balloon. Modified Campbell diagrams were created to calculate the resistive and elastic components of WOB during inspiration and expiration. There were no differences in WOB between BA and RV conditions at 150 W. End-inspiratory and -expiratory lung volumes were elevated (p < 0.05) in the BA condition at higher ventilation rates, which increased inspiratory elastic work and decreased expiratory elastic work at 180 and 210 W (p < 0.05). At 240 W (VE = 112 ± 17 L·min–1 in the BA condition), active expiratory resistive work increased by 59% ± 51%, inspiratory elastic work increased by 26% ± 24%, and total WOB increased by 13% ± 12% in the BA condition (p < 0.05). The SCBA regulator causes an increase in the active expiratory resistive work to maintain high ventilatory rates and an increase inspiratory elastic work through an elevation in lung volumes.

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Changes in airway resistance during sleep onset

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.4.1600 ◽

1994 ◽

Vol 76 (4) ◽

pp. 1600-1607 ◽

Cited By ~ 44

Author(s):

A. Kay ◽

J. Trinder ◽

G. Bowes ◽

Y. Kim

Keyword(s):

Airway Resistance ◽

Sleep Onset ◽

Critical Factor ◽

The State ◽

Healthy Male ◽

Arousal State ◽

Esophageal Balloon ◽

Male Subjects

Ventilation is lower during sleep than wakefulness. An increase in airway resistance has been proposed as the critical factor. As the change in ventilation has been shown to occur abruptly at transitions between alpha and theta electroencephalogram activity, it was of interest to determine whether the increase in airway resistance between wakefulness and sleep also occurs at these transitions. Three young healthy male subjects were run for an average of 15 sleep onsets in each of three conditions. The three conditions were 1) an esophageal balloon was put in place to allow the measurement of airway resistance, 2) in addition to an esophageal balloon the nose was occluded, and 3) there was no esophageal balloon and the nose was not occluded. Ventilation and airway resistance were measured during sleep onset and analyzed as a function of arousal state. In those conditions of the experiment in which airway resistance was affected by state, the changes, like those in ventilation, occurred at transitions between alpha and theta electroencephalogram activity. However, in the three subjects studied, the magnitude of ventilatory changes at alpha-theta transitions and the extent to which changes in ventilation were associated with changes in airway resistance differed between subjects. It was concluded that although inspiratory airway resistance is a major component affecting the state-related changes in ventilation at sleep onset, the degree of its contribution may vary over individuals.

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The Influence of the Self-Contained Breathing Apparatus (SCBA) on Ventilatory Function and Maximal Exercise

Canadian Journal of Applied Physiology ◽

10.1139/h05-137 ◽

2005 ◽

Vol 30 (5) ◽

pp. 507-519 ◽

Cited By ~ 29

Author(s):

Neil D. Eves ◽

Richard L. Jones ◽

Stewart R. Petersen

Keyword(s):

Maximal Oxygen Consumption ◽

The Self ◽

Resistive Load ◽

Expiratory Flow Limitation ◽

Exercise Tests ◽

Low Resistance ◽

Breathing Resistance ◽

Breathing Apparatus ◽

Mouth Pressure ◽

Key Words Ventilation

Our previous work showed that breathing low density gases during exercise with the self-contained breathing apparatus (SCBA) improves maximal ventilation (VE) and maximal oxygen consumption [Formula: see text] This suggests that the SCBA limits exercise by adding a resistive load to breathing. In this study we compared [Formula: see text] with and without the various components comprising the SCBA to determine their impact on [Formula: see text] Twelve males performed 4 randomly ordered incremental exercise tests to exhaustion on a treadmill: (1) low-resistance breathing valve only (CON); (2) full SCBA (SCBA); (3) SCBA regulator only (REG); and (4) carrying the cylinder and harness assembly but breathing through a low-resistance breathing valve (PACK). Compared to CON, [Formula: see text] was reduced to a similar extent in the SCBA and REG trials (14.9% and 13.1%, respectively). The PACK condition also reduced [Formula: see text] but to a lesser extent (4.8 ± 5.3%). At [Formula: see text][Formula: see text] was decreased and expiratory mouth pressure and external breathing resistance (BR) were increased in both the SCBA and REG trials. There was a significant correlation between the change in maximal [Formula: see text] and [Formula: see text] with the SCBA. The results show that the SCBA reduces [Formula: see text] by limiting [Formula: see text] secondary to the increased BR of the SCBA regulator. Key words: ventilation, breathing resistance, expiratory flow limitation, [Formula: see text]

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