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PubMed1986

Reversible respiratory muscle weakness in hypothyroidism.

Physiological studies performed 1 week after initiation of thyroid replacement showed persistence of significant respiratory muscle weakness in a patient presenting with hypothyroidism and hypercapnia. Repeat studies 12 months later demonstrated return of respiratory muscle strength to normal. Earlier reports on respiratory failure in hypothyroidism had postulated a critical role for respiratory muscle weakness in the genesis of hypercapnia. Since hypercapnia was rapidly reversed despite the persistence of severe respiratory muscle weakness, this explanation may not be always correct. It appears than in our patient thyroid replacement had its primary effect on the respiratory control system.

Aged↗
PubMed1995

Respiratory muscle training for patients with chronic obstructive pulmonary disease.

The purpose of this article is to describe respiratory muscle training techniques and the effectiveness of this training in patients with chronic obstructive pulmonary disease (COPD). The respiratory muscles can be strengthened, but the benefit of stronger respiratory muscles in patients with COPD is not clear. Maximal sustained voluntary ventilation, inspiratory resistive breathing, and threshold loading are the three most commonly used techniques for improving the endurance of the inspiratory muscles in patients with COPD. Recent studies using inspiratory resistive breathing with targeted devices or threshold trainers have shown more consistent increases in inspiratory muscle function and exercise tolerance than studies using other techniques. Endurance exercise involving the extremities improves inspiratory muscle endurance in younger individuals with cystic fibrosis but not in older persons with COPD. Recommendations are outlined regarding the techniques to use for respiratory muscle training and which patient populations may benefit from these techniques.

Breathing Exercises↗
PubMed2002

Respiratory muscle training in healthy individuals: physiological rationale and implications for exercise performance.

The respiratory system has traditionally been viewed to be capable of meeting the substantial demands for ventilation and gas exchange and the cardiopulmonary interactions imposed by short-term maximum exercise or long-term endurance exercise. Recent studies suggest that specific respiratory muscle (RM) training can improve the endurance and strength of the respiratory muscles in healthy humans. The effects of RM training on exercise performance remains controversial. When whole-body exercise performance is evaluated using submaximal fixed work-rate tests, significant improvements are seen and smaller, but significant improvements have also been reported in placebo-trained individuals. When performance is measured using time-trial type performance measures versus fixed workload tests, performance is increased to a much lesser extent with RM training. It appears that RM training influences relevant measures of physical performance to a limited extent at most. Interpretation of the collective literature is difficult because most studies have utilised relatively small sample sizes and very few studies have used appropriate control or placebo groups. Mechanisms to explain the purported improvements in exercise performance remain largely unknown. However, possible candidates include improved ratings of breathing perception, delay of respiratory muscle fatigue, ventilatory efficiency, or blood-flow competition between respiratory and locomotor muscles. This review summarises the current literature on the physiology of RM training in healthy individuals and critically evaluates the possible implications for exercise performance.

Breathing Exercises↗
PubMed2006

Respiratory muscle training in persons with spinal cord injury: a systematic review.

The purpose of this paper was to review the effectiveness of respiratory muscle training (RMT) on respiratory muscle strength and endurance, pulmonary function, quality of life, respiratory complications and exercise performance in persons with spinal cord injury. A MEDLINE (National Library of Medicine, Bethesda, MD, USA) database was used for selection of the literature (from 1980 to November 2004), and relevant references from peer-reviewed articles were retrieved as well. Studies investigating the effects of RMT (i.e. resistive breathing weight lifting or normocapnic hyperpnea) in persons with spinal cord injury were selected. Two independent reviewers investigated controlled studies for methodological quality by using a modification of the framework for methodological quality. Methodological quality ranged between 15 and 29 (maximal feasible score=40). Twenty-three papers were retrieved and six controlled trials were kept for further analysis. A meta-analysis and calculation of effect-size of each individual study and weighted summary effect-size was intended. However, unreported data and heterogeneity in outcome variables did not allow performing a meta-analysis. From the systematic review it is concluded that RMT tended to improve expiratory muscle strength, vital capacity and residual volume. Insufficient data was available to make conclusions concerning the effects on inspiratory muscle strength, respiratory muscle endurance, quality of life, exercise performance and respiratory complications.

Exercise Therapy↗
PubMed1994

Respiratory muscle strength and hemodynamics in chronic heart failure.

To examine whether respiratory muscle weakness is associated with cardiac function and/or exercise capacity in chronic heart failure (CHF), 23 patients with CHF were evaluated with respiratory muscle strength, pulmonary function tests, cardiac catheterization, and exercise test. The subjects were divided into three groups on their New York Heart Association (NYHA) functional class. Group A consisted of 13 patients with NYHA functional classification class 3 or 4, group B consisted of 10 patients with NYHA classification class 2, and group C consisted of 15 age-matched normal controls. Respiratory muscle strength was assessed with maximal static inspiratory mouth pressure at residual volume level and expiratory mouth pressure at total lung capacity level (PImax, PEmax, respectively). Pulmonary functions in patients with CHF showed almost normal. PImax in group A was significantly less than that in group B or C, although PImax in group B was not significantly different from that in group C. In the patients with CHF, PImax correlated positively with cardiac index and maximal oxygen consumption (r = 0.460 and r = 0.503, p < 0.05, respectively). These findings suggest that inspiratory muscle strength, which was impaired in patients with severe CHF, may be dependent on cardiac function and may be one of the limiting factors on impaired exercise capacity in the patients with CHF.

Aged↗
PubMed2007

Related trends in locomotor and respiratory muscle oxygenation during exercise.

PURPOSE: We investigated the potential effect of respiratory muscle work on leg muscle oxygenation without artificial intervention in non-endurance-trained young subjects and searched for the range of intensity when this effect could occur. METHODS: We simultaneously monitored accessory respiratory and leg muscle oxygenation patterns with near-infrared spectroscopy (NIRS) in 15 healthy young men performing maximal incremental exercise on a cycle ergometer. Pulmonary gas exchange was measured. The respiratory compensation point (RCP) was determined. Oxygenation (RMO2) and blood volume (RMBV) of the serratus anterior (accessory respiratory muscle) and of the vastus lateralis (LegO2 and LegBV) were monitored with NIRS. The breakdown point of accessory respiratory muscle oxygenation (BPRMO2) and the accelerated (BP1LegO2) and attenuated fall (BP2LegO2) in leg muscle oxygenation were detected. RESULTS: BPRMO2 occurred at approximately 85% .VO2max and was related to RCP (r = 0.88, P < 0.001). BP2LegO2 appeared at approximately 83% .VO2max and was related to RCP (r = 0.57, P < 0.05) and with BPRMO2 (r = 0.64, P = 0.01). From BP2LegO2 to maximal exercise, LegBV was significantly reduced (P < 0.05). CONCLUSION: In active subjects exercising at heavy exercise intensities, we observed that the appearance of the accelerated drop in accessory respiratory muscle oxygenation-associated with high ventilatory level-was related with the attenuated fall in leg muscle oxygenation detected with near-infrared spectroscopy. This suggests that the high oxygen requirement of respiratory muscle leads to limited oxygen use by locomotor muscles as demonstrated in endurance-trained subjects. The phenomenon observed was associated with reduced leg blood volume, supporting the occurrence of leg vasoconstriction. These events appeared not only at maximal exercise but onward above the respiratory compensation point.

Adolescent↗
PubMed1976

[Tonus of respiratory muscles in acetycholine hypotonia (author's transl)].

The importance of respiratory muscles in relation to circulation and ventilation was investigated in acute hypotonia after acetylcholin injection. The tonus of respiratory muscles was assessed by measuring the circumference of chest and abdomen. Changes of volume of the body cavities were examined by body plethysmography. A significant relation between the increase of circumferences of the chest and abdomen and increase of lung volume was registered. The authors conclude, that the tonus of the respiratory muscles determines the volume of chest and abdomen and influences the distribution of blood.

Acetylcholine↗
PubMed2006

Mechanics of respiratory muscles in single-lung transplant recipients.

BACKGROUND: Emphysema and pulmonary fibrosis force the patients to breathe at an abnormal lung volume, which alters the lengths of the respiratory muscles and thereby their work capability is reduced. After single-lung transplantation, muscle function is restored on the side of the transplant but it may be asymmetric to that on the side of the native diseased lung. OBJECTIVE: Investigating the hypothesis that single-lung transplantation induces mechanical asymmetry of the respiratory muscles on the two sides. METHODS: Simultaneously noninvasive measurements of inspiratory and expiratory mouth pressure, airflow rate and electromyography signals from the sternomastoid, external intercostal, rectus abdominis and external oblique muscles were acquired during different breathing maneuvers. The study group included 10 single-lung transplant recipients (5 with pulmonary fibrosis and 5 with emphysema) and 10 healthy controls. RESULTS: Analysis of the finding shows a significant lower global strength of the respiratory muscles of single-lung transplant recipients compared to that of healthy subjects. No significant difference in the EMG signals of respiratory muscles was found either between the different groups or between the sides of the transplant and the native lung in the patient groups. Both single-lung transplant recipients and healthy subjects demonstrated high EMG activity of the inspiratory muscles during inspiration at different breathing efforts. CONCLUSION: Patients after single-lung transplantation have lower respiratory muscle strength than healthy subjects, but apparently normal electrical activity. The lower global respiratory muscle strength emphasizes the importance of their rehabilitation before and after single-lung transplantation.

Adult↗
PubMed1998

Free radical induced respiratory muscle dysfunction.

It is now recognized that respiratory muscle fatigue contributes to the development of respiratory failure in some patients with lung disease. This observation has prompted an examination into the mechanisms of development of muscle fatigue, with the understanding that an elucidation of these processes may lead to new therapeutic approaches to the treatment of these patients. A series of recent studies examining this issue have, moreover, discovered that oxygen-derived free radicals generated during strenuous contraction may modulate respiratory muscle contractile function and contribute to the development of muscle fatigue. The data supporting this concept include: (a) direct (e.g. EPR, ESR studies) and indirect (evidence of lipid peroxidation, protein carbonyl formation, glutathione oxidation) evidence that there is heightened free radical production in contracting muscle, (b) evidence that pharmacologic depletion of muscle antioxidant stores increases degree of muscle fatigue present after a period of exercise, and (c) evidence that administration of agents that act as free radical scavengers retard the development muscle fatigue. Free radicals may produce these changes in muscle force generating capacity by interacting with and altering the function of a number of intracellular-biophysical processes (i.e. sarcolemmal action potential propagation, sarcoplasmic reticulum calcium handling, mitochondrial function, contractile protein interactions).

Acetylcysteine↗
PubMed1989

Respiratory muscle weakness in the Lambert-Eaton myasthenic syndrome.

Respiratory muscle function was assessed in six patients with the Lambert-Eaton myasthenic syndrome. Five had histologically proved small cell carcinoma of the lung; the sixth later developed metastases from an unknown primary site. Two patients had ventilatory failure, one without respiratory symptoms; another, who had emphysema, had dyspnoea and orthopnoea. The remaining three patients had no respiratory symptoms. Four patients had limb muscle weakness as judged by the maximal voluntary contraction of the quadriceps muscle (range for all subjects 32-100% predicted). Transdiaphragmatic pressure (Pdi) was measured during a maximal unoccluded sniff (Pdi: sniff), a maximal sustained inspiratory effort against a closed airway (Pdi: Pimax), and phrenic nerve stimulation (Pdi: twitch). Mild to moderate diaphragmatic weakness was present in all six patients in proportion to the degree of leg weakness (Pdi: sniff 30-64% predicted; r = 0.6; Pdi:Pimax 6-69% predicted, r = 0.8); this was associated with very low or absent Pdi:twitch during phrenic nerve stimulation. Four patients had weakness of the expiratory muscles. Improvement in muscle strength was documented in two patients after tumour chemotherapy and specific treatment with 3,4-diaminopyridine and prednisolone; one patient was still alive five years from first diagnosis. It is concluded that the respiratory muscles may be implicated in this condition more often than has previously been recognised. As the lack of mobility may cause respiratory symptoms to be minimised, the presence of respiratory muscle weakness may remain undiagnosed unless formal measurement of respiratory muscle function is made.

Autoimmune Diseases↗
PubMed1987

Fiber types and fiber diameters in canine respiratory muscles.

In the present study, we measured fiber types and fiber diameters in canine respiratory muscles and examined regional variation within the diaphragm. Samples of eight diaphragm regions, internal intercostals, external intercostals, transversus abdominis, and triceps brachii were removed from eight adult mongrel dogs, frozen, and histochemically processed for standard fiber type and fiber diameter determinations. The respiratory muscles were composed of types I and IIa fibers; no IIb fibers were identified. Fiber composition differed between muscles (P less than 0.0001). Normal type I percent (+/- SE) were: diaphragm 46 +/- 2, external intercostal 85 +/- 6, internal intercostals 48 +/- 3, transversus abdominis 53 +/- 1, and triceps 33 +/- 7. The diaphragm also contained a type I subtype [6 +/- 1% (SE)] previously thought only to occur in developing muscle. Fiber composition varied between diaphragm regions (P less than 0.01). Most notably, left medial crus contained 64% type I fibers. Fiber size also varied systematically among muscles (P less than 0.025) and diaphragm regions (P less than 0.0005). External intercostal fiber diameter was largest (47-50 microns) and diaphragm was smallest (34 microns). Within diaphragm, crural fibers were larger than costal (P less than 0.05). We conclude that there are systematic differences in fiber composition and fiber diameter of the canine respiratory muscles.

Analysis of Variance↗
PubMed1987

Muscle respiratory capacity and VO2 max in identically trained young and old rats.

Old rats have a decreased hindlimb muscle respiratory capacity and whole-body maximal O2 consumption (VO2 max). The decline in spontaneous physical activity in old rats might contribute to these age-related changes. The magnitude of the age-related decline is not uniform in all skeletal muscle respiratory enzymes, and the decrease in palmitate oxidation is particularly great. This study was designed to determine if young and old rats subjected to the same exercise-training protocol would attain similar values for VO2 max and several markers of muscle respiratory capacity. Four- and 18-mo-old Fischer 344 rats underwent an identical 6-mo program of treadmill running. After training, both age groups had increased VO2 max above sedentary age-matched controls. However, the old trained rats had a lower VO2 max than identically trained young rats. In contrast to VO2 max, the two trained groups attained similar values for gastrocnemius citrate synthase, cytochrome oxidase, 3-hydroxyacyl-CoA dehydrogenase, palmitate oxidation, and total carnitine concentration. Thus, when the young and old rats performed an identical exercise protocol within the capacity of the old animals, differences in skeletal muscle respiratory capacity were eliminated. The dissimilarity in VO2 max between the identically trained groups was apparently caused by age-related differences in factors other than muscle respiratory capacity.

Aging↗
PubMed1987

Flow-volume loop changes reflecting respiratory muscle weakness in chronic neuromuscular disorders.

In order to identify the changes in pulmonary function and in the flow-volume loop due to respiratory muscle weakness, two groups of 10 nonsmokers with stable, chronic neuromuscular disease but without respiratory symptoms were studied: one without (Group 1) and one with (Group 2) respiratory muscle weakness as assessed by measurement of maximal static inspiratory and expiratory pressures. In Group 1, pulmonary function was normal except for increased ratio of one-second forced expiratory volume to forced vital capacity and forced expiratory flow at 25 to 75 percent forced vital capacity, which may reflect increased elastic lung recoil. Group 2 had mild volume restriction, appropriate for the degree of respiratory muscle weakness, and reduced inspiratory and expiratory flow rates. Pulmonary function was significantly more disturbed in Group 2 than in Group 1, and correlated well with maximal static inspiratory and expiratory pressures. Analysis of the flow-volume loop configuration revealed that four parameters describing effort-dependent portions were significantly related to maximal static inspiratory pressure and maximal static expiratory pressure. These parameters were peak expiratory flow, the slope of the ascending limb of the maximal expiratory curve, a drop of forced expiratory flow near residual volume, and forced inspiratory flow at 50 percent of vital capacity. A flow-volume loop score obtained from these four parameters was significantly higher in Group 2 than in Group 1 (2.8 +/- 1.03 versus 1.1 +/- 1.37; p less than 0.01). A flow-volume loop score of 2 or more had 80 percent specificity and 90 percent sensitivity in predicting respiratory muscle weakness in these patients with chronic neuromuscular disease. These data suggest that sensitive assessment of the flow-volume loop configuration as part of routine pulmonary function testing may help to suspect and identify respiratory muscle weakness.

Chronic Disease↗
PubMed1996

Respiratory muscle strength after lung resection with special reference to age and procedures of thoracotomy.

Changes in respiratory muscle strength after lung resection were examined concerning age and procedures of thoracotomy. Maximum inspiratory (MIP) and expiratory (MEP) mouth pressure were measured before operation and 1, 2, 4, and 12 weeks after operation in 81 patients undergoing lung resection. In 48 patients undergoing pneumonectomy, lobectomy, or segmentectomy, patients older than 70 showed a significantly lower MIP and MEP before operation and throughout the postoperative period compared to younger ones (P < 0.01). Furthermore, the older patients showed a significantly lower percentage of postoperative MIP and MEP 4 weeks after operation than the younger ones (P < 0.01). In 31 patients undergoing lung wedge resection, patients undergoing limited thoracotomy (LT) and video-assisted thoracic surgery (VATS) showed significantly higher percentages of postoperative MIP and MEP than those undergoing posterolateral thoracotomy (PLT) 1 and 2 weeks after operation (P < 0.01 or 0.05). But there was no significant difference in the values between LT and VATS. We concluded that (1) elderly patients suffered respiratory muscle weakness before and after operation and their postoperative recovery of respiratory muscle strength was slower than in younger patients, and (2) VATS and LT resulted in more rapid recovery of respiratory muscle strength than PLT, but the difference between VATS and LT was not significant.

Adult↗
PubMed1998

Eliminating ultrasonic interference from respiratory muscle EMG.

Fine wire recordings of the respiratory muscle electromyogram are often employed to represent muscle activity, and recently ultrasound-sonomicrometry has become a common method of measuring length of respiratory muscles in both acute and chronic preparations. Although recording both EMG and sonomicrometry simultaneously has become standard practice, there has not been any consideration of the potential confounding influence of ultrasound noise upon the recorded EMG spectrum. Activation of the sonomicrometry-ultrasound tranducer introduces a high frequency, high amplitude voltage pulse plus harmonics, which can contaminate the EMG spectrum directly, as well as through aliasing when EMG is sampled directly digitally. We describe the use of a new, combined, wing stabilized sonomicrometry- and EMG measurement transducer to characterize exactly the influence of ultrasound upon the crural diaphragm EMG spectrum, and the development of digital filtering techniques which effectively eliminate the ultrasound interference. Two alternative methods of avoiding ultrasound-EMG interference are also considered. The isolation and elimination of ultrasound-sonomicrometry signal interference may be important in studies where EMG and length are measured together.

Animals↗
PubMed1998

Calcium ATPase and respiratory muscle function.

The sarcoplasmic reticulum (SR) of striated muscle is a highly specialized intracellular membrane system that plays a key role in the contraction-relaxation cycle of muscle. Its primary function is the regulation of cytoplasmic Ca2+ concentration. A key element in this regulation is the Sarco(endo)plasmic reticulum Ca2+-adenosine triphosphatase (SERCA), which by sequestering Ca2+ into the SR, induces and maintains relaxation. It has been extensively studied with respect to structure and mechanism of action, and more recently to gene expression. Three separate genes encode five SERCA isoforms, two of which, SERCA 1 and SERCA 2, are expressed in skeletal muscle. In the first part of this review we focus on the general properties of the Ca2+ pump (structure and function and regulation of activity). In the second part we describe variations in SERCA expression in various physiological and pathological situations. These have essentially been studied in the heart and skeletal muscles, with data in respiratory muscles being very limited.

Animals↗
PubMed2004

Effects of respiratory muscle weakness on daily living function, quality of life, activity levels, and exercise capacity in mild to moderate Parkinson's disease.

OBJECTIVE: To investigate respiratory muscle strength in mild to moderate Parkinson's disease in comparison with prediction equations and age-matched controls. To identify correlations between respiratory muscle strength and daily living function, activity levels, quality of life, and exercise capacity. DESIGN: A total of 66 participants with Parkinson's disease and 32 age-matched, healthy controls participated. Respiratory mouth pressures (representing respiratory muscle strength) were compared with predicted values. A comparison was also made between participants with Parkinson's disease and age-matched controls. Respiratory mouth pressures were correlated with results of the Barthel index (daily living function), a modified Baecke activity questionnaire (activity levels), the Parkinson's disease questionnaire (quality of life in Parkinson's disease), peak heart rate, peak oxygen consumption, blood lactate thresholds, and the number of stages completed during an incremental cycle ergometer test (representing exercise capacity). RESULTS: Respiratory mouth pressures were significantly lower (P < 0.05) in the Parkinson's disease group, but this did not influence the measures of daily living function, activity levels, and quality of life. Respiratory mouth pressures correlated with lactate thresholds (r = 0.308, P < 0.01) and the number of completed stages of the cycle ergometer test (r = 0.490, P < 0.01). CONCLUSIONS: In mild to moderate Parkinson's disease, there is a significant weakness of the respiratory muscles. This can affect the individual during exercise but has no apparent effect on activities that do not require a large effort of the respiratory muscles.

Activities of Daily Living↗