Mechanical and Electrical Properties of Respiratory Muscles

Sharp, John T.; Hyatt, Robert E.

doi:10.1002/cphy.cp030323

Cited by 17 publications

(18 citation statements)

References 186 publications

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“…Our findings agree with this postulate: 4 weeks of normobaric hypoxia did not change endurance of the mouse diaphragm in vitro , whereas the soleus fatigues more rapidly. While this result could be explained at least in part by inherent differences in oxidative capacity between the two muscles [46;51], we found evidence of further adaptation of the mouse diaphragm to chronic hypoxia. One such example is the reduction in fiber cross sectional area in the Hypoxia diaphragm, but not in triceps surae.…”

Section: Discussionmentioning

confidence: 60%

Muscle endurance and mitochondrial function after chronic normobaric hypoxia: contrast of respiratory and limb muscles

Gamboa

Andrade

2011

Pflugers Arch - Eur J Physiol

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Skeletal muscle adaptation to chronic hypoxia includes loss of oxidative capacity and decrease in fiber size. However, the diaphragm may adapt differently since its activity increases in response to hypoxia. Thus, we hypothesized that chronic hypoxia would not affect endurance, mitochondrial function or fiber size in the mouse diaphragm. Adult male mice were kept in normoxia (Control) or hypoxia (Hypoxia, FIO2= 10%) for 4 weeks. After that time, muscles were collected for histological, biochemical and functional analyses. Hypoxia soleus muscles fatigued faster (fatigue index higher in Control, 21.5±2.6% vs. 13.4±2.4%, p<0.05), but there was no difference between Control and Hypoxia diaphragm bundles. Mean fiber cross sectional area was unchanged in Hypoxia limb muscles, but it was 25% smaller in diaphragm (p<0.001). Ratio of capillary length contact to fiber perimeter was significantly higher in Hypoxia diaphragm (28.6±1.2 vs. 49.3±1.4, Control and Hypoxia, p<0.001). Mitochondrial respiration rates in Hypoxia limb muscles were lower: state 2 decreased 19%, state 3 31% and state 4 18% vs. Control, p<0.05 for all comparisons. There were similar changes in Hypoxia diaphragm: state 3 decreased 29% and state 4 17%, p<0.05. After 4 weeks of hypoxia limb muscle mitochondria had lower content of complex IV (cytochrome c oxidase), while diaphragm mitochondria had higher content of complexes IV and V (F1/F0 ATP synthase) and less uncoupling protein 3 (UCP-3). These data demonstrate that diaphragm retains its endurance during chronic hypoxia, apparently due to a combination of morphometric changes and optimization of mitochondrial energy production.

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Section: Discussionmentioning

confidence: 60%

Muscle endurance and mitochondrial function after chronic normobaric hypoxia: contrast of respiratory and limb muscles

Gamboa

Andrade

2011

Pflugers Arch - Eur J Physiol

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“…Baken and colleagues also found that the form of prephonatory movements of the rib cage and abdomen was not influenced by respiratory phase or volume, although movement times were longer if the subjects were at low lung volumes at the time the stimulus was received (Baken et al, 1979). The finding that the form of prephonatory movements was not influenced by respiratory phase or volume is surprising because the pressures generated by active muscle forces and the passive mechanical properties of the chest wall change significantly throughout the quiet breathing cycle (Sharp & Hyatt, 1986;Smith & Loring, 1986). One might predict, therefore, that the form of prephonatory movements would be influenced, at least in part, by the respiratory phase at the time of voice initiation.…”

mentioning

confidence: 78%

Effects of Vocal Task and Respiratory Phase on Prephonatory Chest Wall Movements

McFarland

Smith

1992

J Speech Lang Hear Res

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Anne SmithA vocal reaction time paradigm was used to explore prephonatory respiratory kinematics. Department of Audiology andMovements of the rib cage and abdomen were recorded prior to production of utterances Speech Sciences differing in length and intensity, and vocal responses were elicited in different phases and Purdue University volumes of the quiet breathing cycle. A velocity threshold was used to distinguish prephonatory West Lafayette, IN adjustments from the cyclical movements of the chest wall that are characteristic of quiet breathing. The results suggest that a variety of prephonatory kinematic events can occur prior to initiation of vocalization in response to a stimulus. Further, prephonatory movements appear to be adaptive in that they are influenced by the length of the utterance to be spoken and the respiratory volume at the time of voice initiation.

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“…The force developed by contracting muscles is proportional to their IEMG activity under both isometric and isotonic conditions (18,21,25). The rate of rise or slope of the IEMG activity reflects the rate of recruitment of motor units, as well as the increase in their firing frequency, while IEMG P is an expression of the total number of units recruited and of their maximal firing frequency (26).…”

Section: Discussionmentioning

confidence: 99%

Defective Motor Control of Coughing in Parkinson's Disease

Fontana

Pantaleo

Lavorini

et al. 1998

Am J Respir Crit Care Med

130

119

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The high incidence of serious chest infections in patients with Parkinson's disease is unexplained, but an impairment in cough reflex may have a role. Maximal voluntary cough (MVC) and reflex cough (RC) to inhalation of ultrasonically nebulized distilled water were analyzed in patients with Parkinson's disease and age-matched control subjects by monitoring the integrated electromyographic activity (IEMG) of abdominal muscles. The peak amplitude of IEMG activity (IEMGP) was expressed as a fraction of the highest IEMGP value observed during MVC corrected to account for possible losses in abdominal muscle force due to reduced central muscle activation. Cough intensity was indexed in terms of both the IEMGP and the ratio of IEMGP to the duration of the expiratory ramp (TEC), i.e., the rate of rise of IEMG activity. Cough threshold was slightly higher in patients than in control subjects, but the difference failed to reach statistical significance. Compared with control subjects, patients displayed a lower IEMGP during maximal expiratory pressure maneuvers (PEmax), MVC, and RC (p always < 0.01); TEC during RC was longer (p < 0.01) than in controls. Consequently, the rate of rise of IEMG activity during cough was always lower in patients (p < 0. 01), especially during RC. Finally, PEmax, and both the peak and rate of rise of IEMG activity during RC were inversely related to the level of clinical disability (Spearman rank correlation coefficient, rs = -0.88, -0.86, and -0.85, respectively, p always < 0.01). The results indicate that the central neural mechanisms subserving the recruitment of motor units and/or the increase in their frequency of discharge during voluntary and, even more markedly, RC are impaired in patients with Parkinson's disease.

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Mechanical and Electrical Properties of Respiratory Muscles

Cited by 17 publications

References 186 publications

Muscle endurance and mitochondrial function after chronic normobaric hypoxia: contrast of respiratory and limb muscles

Muscle endurance and mitochondrial function after chronic normobaric hypoxia: contrast of respiratory and limb muscles

Effects of Vocal Task and Respiratory Phase on Prephonatory Chest Wall Movements

Defective Motor Control of Coughing in Parkinson's Disease

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