Force-length relationship of the normal human diaphragm

Braun, Norma M. T.; Arora, Narinder S.; Rochester, Dudley F.

doi:10.1152/jappl.1982.53.2.405

Cited by 164 publications

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“…Wait et al (16) used M-mode ultrasound to demonstrate inspiratory thickening of the diaphragm in the area of the ZOA; however, the degree of thickening and, therefore, the degree of shortening that they measured was greater than the degree of diaphragm shortening previously measured in animals (5,6,8,11,14) or estimated in humans (4,9,17). Discrepancies between the ultrasound measurements and the previous human and animal studies may be related to the narrow range of volume [from functional residual capacity (FRC) to one-half vital capacity (VC)] over which the thickness measurements were made or to limitations of M-mode ultrasound.…”

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confidence: 89%

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Diaphragm thickening during inspiration

Cohn

Benditt

Eveloff

et al. 1997

Journal of Applied Physiology

228

170

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.-Ultrasound has been used to measure diaphragm thickness (T di ) in the area where the diaphragm abuts the rib cage (zone of apposition). However, the degree of diaphragm thickening during inspiration reported as obtained by one-dimensional M-mode ultrasound was greater than that predicted by using other radiographic techniques. Because two-dimensional (2-D) ultrasound provides greater anatomic definition of the diaphragm and neighboring structures, we used this technique to reevaluate the relationship between lung volume and T di . We first established the accuracy and reproducibility of 2-D ultrasound by measuring T di with a 7.5-MHz transducer in 26 cadavers. We found that T di measured by ultrasound correlated significantly with that measured by ruler (R 2 5 0.89), with the slope of this relationship approximating a line of identity (y 5 0.89x 1 0.04 mm). The relationship between lung volume and T di was then studied in nine subjects by obtaining diaphragm images at the five target lung volumes [25% increments from residual volume (RV) to total lung capacity (TLC)]. Plots of T di vs. lung volume demonstrated that the diaphragm thickened as lung volume increased, with a more rapid rate of thickening at the higher lung volumes [T di 5 1.74 vital capacity (VC) 2 1 0.26 VC 1 2.7 mm] (R 2 5 0.99; P , 0.001) where lung volume is expressed as a fraction of VC. The mean increase in T di between RV and TLC for the group was 54% (range 42-78%). We conclude that 2-D ultrasound can accurately measure T di and that the average thickening of the diaphragm when a subject is inhaling from RV to TLC using this technique is in the range of what would be predicted from a 35% shortening of the diaphragm. ultrasonography; diaphragm length; diaphragm thickness; diaphragm mechanics THE RELATIONSHIP BETWEEN diaphragm length (L di ) and lung volume has been well described in animals. Using sonomicrometers, previous investigators have found that the canine diaphragm shortens by 20-42% as lung volume increases from residual volume (RV) to total lung capacity (TLC) (5,6,8,11,14). Changes in L di have not been directly measured in humans. Instead, diaphragm shortening has been indirectly assessed by using radiographic techniques. Between RV and TLC, diaphragm shortening is estimated to be in the range of 25-35% (4, 9, 10, 17). It is likely that the diaphragm maintains a constant volume and increases its circumference minimally as it shortens; thus the diaphragm must thicken as it shortens. Measurements of diaphragm thickening, then, may provide an alternate means of assessing the relationship between L di and lung volume.Measurements of diaphragm thickness (T di ) have been made with the use of ultrasound to visualize the diaphragm in the area where it abuts the rib cage [zone of apposition (ZOA)] (12, 16). Wait et al. (16) used M-mode ultrasound to demonstrate inspiratory thickening of the diaphragm in the area of the ZOA; however, the degree of thickening and, therefore, the degree of shortening that they measured was greater than th...

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confidence: 89%

“…Instead, diaphragm shortening has been indirectly assessed by using radiographic techniques. Between RV and TLC, diaphragm shortening is estimated to be in the range of 25-35% (4,9,10,17). It is likely that the diaphragm maintains a constant volume and increases its circumference minimally as it shortens; thus the diaphragm must thicken as it shortens.…”

mentioning

confidence: 99%

Diaphragm thickening during inspiration

Cohn

Benditt

Eveloff

et al. 1997

Journal of Applied Physiology

228

170

View full text Add to dashboard Cite

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“…In addition, pulmonary mechanics are altered with the increase in the earlier mentioned pressure difference between the outside of the chest and the alveolar air (static lung load) (61). The stress of increased static lung load strains the respiratory system, which may lead to changes in end-expiratory lung volume (61,99), placing the respiratory muscles at a less than optimal muscle length, and thus reducing their ability to generate and maintain adequate force (14,63) to cope with the increased work of breathing. There are increases in blood flow to the respiratory muscles, reflecting their increased metabolism (42).…”

Section: Respiratory Functionmentioning

confidence: 99%

The underwater environment: cardiopulmonary, thermal, and energetic demands

Pendergast¹,

Lundgren²

2009

Journal of Applied Physiology

134

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Pendergast DR, Lundgren CE. The underwater environment: cardiopulmonary, thermal, and energetic demands. J Appl Physiol 106: 276 -283, 2009. First published November 26, 2008 doi:10.1152/japplphysiol.90984.2008.-Water covers over 75% of the earth, has a wide variety of depths and temperatures, and holds a great deal of the earth's resources. The challenges of the underwater environment are underappreciated and more short term compared with those of space travel. Immersion in water alters the cardio-endocrine-renal axis as there is an immediate translocation of blood to the heart and a slower autotransfusion of fluid from the cells to the vascular compartment. Both of these changes result in an increase in stroke volume and cardiac output. The stretch of the atrium and transient increase in blood pressure cause both endocrine and autonomic changes, which in the short term return plasma volume to control levels and decrease total peripheral resistance and thus regulate blood pressure. The reduced sympathetic nerve activity has effects on arteriolar resistance, resulting in hyperperfusion of some tissues, which for specific tissues is time dependent. The increased central blood volume results in increased pulmonary artery pressure and a decline in vital capacity. The effect of increased hydrostatic pressure due to the depth of submersion does not affect stroke volume; however, a bradycardia results in decreased cardiac output, which is further reduced during breath holding. Hydrostatic compression, however, leads to elastic loading of the chest wall and negative pressure breathing. The depthdependent increased work of breathing leads to augmented respiratory muscle blood flow. The blood flow is increased to all lung zones with some improvement in the ventilation-perfusion relationship. The cardiac-renal responses are time dependent; however, the increased stroke volume and cardiac output are, during head-out immersion, sustained for at least hours. Changes in water temperature do not affect resting cardiac output; however, maximal cardiac output is reduced, as is peripheral blood flow, which results in reduced maximal exercise performance. In the cold, maximal cardiac output is reduced and skin and muscle are vasoconstricted, resulting in a further reduction in exercise capacity. respiratory; renal; immersion; exercise; aging; sex differences; submersion; pressure; energy cost THE UNDERWATER ENVIRONMENT is unique, and while it is a magical place with great history and beauty and plant and animal life and holds a wealth of resources, it also imposes pronounced physiological stresses on humans and animals. This brief review offers an overview of how the major environmental challenges, i.e., the pressure, temperature extremes, and the unbreathable ambient medium, of the "Silent World" affect circulation, renal system and water balance, breathing, exercise, and thermal balance and how it imposes some threats due to pharmacological or toxic effects of respired gases at high pressure, i.e., great depths. Adaptations to ...

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“…The diaphragm operates at a shorter resting length during tidal breathing, in an unfavorable position on its length-tension curve. This leads to decreased force of contraction for a given neural stimulus (9). Changes of in vivo diaphragm configuration also impair its effectiveness at lowering pleural pressure for a given tension.…”

Section: Effects Of Emphysema On Inspiratory Musclesmentioning

confidence: 99%

Physiologic Basis for Improved Pulmonary Function after Lung Volume Reduction

Fessler¹,

Scharf²,

Ingenito³

et al. 2008

Proceedings of the American Thoracic Society

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It is not readily apparent how pulmonary function could be improved by resecting portions of the lung in patients with emphysema. In emphysema, elevation in residual volume relative to total lung capacity reduces forced expiratory volumes, increases inspiratory effort, and impairs inspiratory muscle mechanics. Lung volume reduction surgery (LVRS) better matches the size of the lungs to the size of the thorax containing them. This restores forced expiratory volumes and the mechanical advantage of the inspiratory muscles. In patients with heterogeneous emphysema, LVRS may also allow space occupied by cysts to be reclaimed by more normal lung. Newer, bronchoscopic methods for lung volume reduction seek to achieve similar ends by causing localized atelectasis, but may be hindered by the low collateral resistance of emphysematous lung. Understanding of the mechanisms of improved function after LVRS can help select patients more likely to benefit from this approach.Keywords: lung mechanics; emphysema surgery; lung recoil; airflow limitation; respiratory muscles PHYSIOLOGIC BASIS FOR IMPAIRMENT WITH EMPHYSEMAInflammatory changes associated with chronic obstructive pulmonary disease (COPD) initiate the changes in lung mechanical properties that characterize emphysema. Inflammation leads to destruction of elastin, which contributes to lung elasticity, and collagen, which provides tensile strength. Although recent interest has focused on the cellular and molecular mechanisms contributing to emphysema, the study of lung mechanical stresses, one of the earliest postulated causes of emphysema (1), has received less attention. Weakened lung parenchyma is more likely to fracture during respiratory stress, and coalescence of a few alveoli can increase stress on adjacent units in a way that favors formation of large, localized cysts similar to the pattern seen in patients with advanced emphysema (2-4). Effects of Emphysema on Expiratory FlowThese sequelae of inflammation ultimately decrease lung elastic recoil and small airway caliber, contributing to characteristic airflow limitation. The three classic determinants of expiratory flow limitation are lung elastic recoil, the propensity for airways to close, and airway resistance (5). Loss of elastic recoil in emphysema decreases the upstream pressure that drives expiratory flow, thereby decreasing maximal flows at any lung volume. Loss of elastic recoil also increases the unstressed volume of the lung (the volume remaining when elastic recoil is zero). Loss of radial traction on airways from lung parenchyma contributes to airway closure at higher lung volumes (increased trapped volume) because a higher transmural pressure is required to maintain airway patency. In addition, airway caliber at any lung volume is decreased (6). Coexisting small airway inflammation and fibrosis further increase airway resistance (7,8). These changes collectively reduce the rate of lung emptying.The rate of lung emptying may be expressed as its time constant, the time necessary for approximately 63% o...

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Force-length relationship of the normal human diaphragm

Cited by 164 publications

References 0 publications

Diaphragm thickening during inspiration

Diaphragm thickening during inspiration

The underwater environment: cardiopulmonary, thermal, and energetic demands

Physiologic Basis for Improved Pulmonary Function after Lung Volume Reduction

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