The Pressure-Volume Diagram of the Thorax and Lung

Rahn, Hermann; Otis, Arthur B.; Chadwick, L. E.; Fenn, Wallace O.

doi:10.1152/ajplegacy.1946.146.2.161

Cited by 467 publications

(206 citation statements)

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“…It is well known that PI,max decreases as lung volume increases [1, 3,4,23,24]. In the present study, all PI,max obtained at RV were significantly higher than those obtained at FRC, and this is probably attributable to the additional elastic recoil of the lungs and chest wall.…”

Section: Resultssupporting

confidence: 39%

Peak or plateau maximal inspiratory mouth pressure: which is best?

Windisch¹,

Hennings²,

Sorichter³

et al. 2004

Eur Respir J

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There is no clear evidence as to how maximal inspiratory mouth pressure (PI,max) should be measured, although plateau pressures sustained for 1 s and measured at residual volume (RV) are usually recommended.Peak and plateau PI,max were measured at RV and at functional residual capacity (FRC) in 533 healthy subjects (aged 10-90 yrs) in order to comparably test all PI,max measurements for their predictors, reproducibility and normal values.Plateau pressures accounted for 82.0-86.3% of peak pressures. Peak and plateau pressures measured at FRC accounted for 84.3-90.5% of pressures at RV, and were highly correlated. Age was negatively predictive and weight and body mass index positively predictive of PI,max, but regression parameters were low. All PI,max measurements were comparable when calculating regression parameters, between-subject variability and reproducibility.In conclusion, peak and plateau maximal inspiratory mouth pressure are comparably useful for the assessment of inspiratory muscle strength and can be reliably measured at functional residual capacity and at residual volume. Regression equations are of low impact in predicting normal values due to the weak influence of demographic and anthropometric factors and to the high unexplained between-subject-variability. Agerelated 5th percentiles can indicate the lower limit of the normal range. Eur Respir J 2004; 23: 708-713.

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Section: Resultssupporting

confidence: 39%

Peak or plateau maximal inspiratory mouth pressure: which is best?

Windisch¹,

Hennings²,

Sorichter³

et al. 2004

Eur Respir J

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“…Furthermore, with progressively increasing exercise, activation of expiratory muscles, in the absence of expiratory flow limitation, reduces end-expiratory lung volume (EELV) below resting levels (44), helping to assist the inspiratory muscles in three ways. First, the reduced EELV enables increases in tidal volume to occur over the most linear portion of the respiratory system pressurevolume relationship such that respiratory system compliance remains high (99,123). Second, the reduced EELV means that the diaphragm is lengthened, enabling this muscle to operate near its optimal length for force generation (101,114).…”

Section: Exercise Demands On the Respiratory Musclesmentioning

confidence: 99%

Exercise-induced respiratory muscle fatigue: implications for performance

Romer

Polkey²

2008

Journal of Applied Physiology

261

212

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Romer LM, Polkey MI. Exercise-induced respiratory muscle fatigue: implications for performance. J Appl Physiol 104: 879 -888, 2008. First published December 20, 2007 doi:10.1152/japplphysiol.01157.2007.-It is commonly held that the respiratory system has ample capacity relative to the demand for maximal O 2 and CO2 transport in healthy humans exercising near sea level. However, this situation may not apply during heavy-intensity, sustained exercise where exercise may encroach on the capacity of the respiratory system. Nerve stimulation techniques have provided objective evidence that the diaphragm and abdominal muscles are susceptible to fatigue with heavy, sustained exercise. The fatigue appears to be due to elevated levels of respiratory muscle work combined with an increased competition for blood flow with limb locomotor muscles. When respiratory muscles are prefatigued using voluntary respiratory maneuvers, time to exhaustion during subsequent exercise is decreased. Partially unloading the respiratory muscles during heavy exercise using low-density gas mixtures or mechanical ventilation can prevent exercise-induced diaphragm fatigue and increase exercise time to exhaustion. Collectively, these findings suggest that respiratory muscle fatigue may be involved in limiting exercise tolerance or that other factors, including alterations in the sensation of dyspnea or mechanical load, may be important. The major consequence of respiratory muscle fatigue is an increased sympathetic vasoconstrictor outflow to working skeletal muscle through a respiratory muscle metaboreflex, thereby reducing limb blood flow and increasing the severity of exerciseinduced locomotor muscle fatigue. An increase in limb locomotor muscle fatigue may play a pivotal role in determining exercise tolerance through a direct effect on muscle force output and a feedback effect on effort perception, causing reduced motor output to the working limb muscles. respiratory muscles; exercise; diaphragm; abdominals; magnetic stimulation; metaboreflex THE PURPOSE OF THIS MINIREVIEW is to address the question of whether the respiratory demands of exercise contribute significantly toward exercise limitation, either directly through limitations of the respiratory muscle pump or indirectly through effects on limb blood flow and locomotor muscle fatigue. We describe the mechanical and metabolic costs of meeting the ventilatory requirements of exercise. We then ask whether the respiratory muscles fatigue with exercise, what factors contribute to any such fatigue, and what the implications of these factors are for exercise tolerance. Finally, we deal with the potential mechanisms by which respiratory muscle fatigue could compromise exercise tolerance and whether it is possible to overcome this potential respiratory limitation. Our review focuses on the healthy young adult exercising near sea level. However, we also consider special circumstances that determine the balance between metabolic demand and respiratory system capacity in the highly trained endurance ...

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“…The obvious candidate for this is progressive dynamic hyperinflation. Dynamic hyperinflation would, despite increased neural drive [21], give the appearance of a levelling off of inspiratory muscle pressure generation by virtue of the length/tension relationship [25]. Since the maximum expiratory flow/volume curve is not changed during exercise in COPD [26], increased minute ventilation requires movement of the end-expiratory lung volume closer to the total lung capacity.…”

Section: Significance Of the Findingsmentioning

confidence: 99%

Respiratory muscle activity in patients with COPD walking to exhaustion with and without pressure support

Kyroussis¹,

Polkey²,

Hamnegärd³

et al. 2000

Eur Respir J

117

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The function of the diaphragm and other respiratory muscles during exercise in chronic obstructive pulmonary disease (COPD) remains controversial and few data exist regarding respiratory muscle pressure generation in this situation.The inspiratory pressure/time products of the oesophageal and transdiaphragmatic pressure, and the expiratory gastric pressure/time product during exhaustive treadmill walking in 12 patients with severe COPD are reported. The effect of noninvasive positive pressure ventilation during treadmill exercise was also examined in a subgroup of patients (n=6).During free walking, the inspiratory pressure/time products rose early in the walk and then remained level until the patients were forced to stop because of intolerable dyspnoea. In contrast, the expiratory gastric pressure/time product increased progressively throughout the walk. When patients walked the same distance assisted by noninvasive positive pressure ventilation, a substantial reduction was observed in the inspiratory and expiratory pressure/time products throughout the walk. When patients walked with positive pressure ventilation for as long as they could, the pressure/time products observed at exercise cessation were lower than those observed during exercise cessation after free walking.It is concluded that, in severe chronic obstructive pulmonary disease, inspiratory muscle pressure generation does not increase to meet the demands imposed by exhaustive exercise, whereas expiratory muscle pressure generation rises progressively. Inspiratory pressure support was shown to substantially unload all components of the respiratory muscle pump. Eur Respir J 2000; 15: 649±655.

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The Pressure-Volume Diagram of the Thorax and Lung

Cited by 467 publications

References 0 publications

Peak or plateau maximal inspiratory mouth pressure: which is best?

Peak or plateau maximal inspiratory mouth pressure: which is best?

Exercise-induced respiratory muscle fatigue: implications for performance

Respiratory muscle activity in patients with COPD walking to exhaustion with and without pressure support

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