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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the effects of resistive breathing in 10 patients with long-standing, severe disabling COPD. Small increases in inspiratory resistive load resulted in diaphragmatic fatigue and failure in all patients. Fatigue was detected using the frequency spectrum analysis of an EMG signal obtained with surface electrodes. Failure was defined as an inward displacement of the abdomen during inspiration, i.e. incoordination of thoracoabdominal motion. The patients trained for one half hour daily for 4 weeks, breathing into a simple device, where they inspired against a resistive load that produced some incoordinated breaths. After 4 weeks this load was increased, if possible, and another 4-week training period started. All patients improved with training, i.e. higher resistances could be tolerated without signs of fatigue and failure. In addition most patients claimed that training had helped them in their daily living; they were able to do more without getting short of breath. The device helped expectoration, possibly owing to the effect of the small expiratory resistance.
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PMID:Resistive breathing training in severe chronic obstructive pulmonary disease. A pilot study. 49 5

Eight patients with mild-to-moderate chronic obstructive pulmonary disease (COPD) and average resting Pao2 of 66 mm Hg were studied clinically and physiologically at sea level and after ascent to 1,920 m. At sea level the patients were symptomatic but not disabled. After ascent the patients had only mild symptoms of fatigue and insomnia, and one had severe headache during exercise on the first day. Funduscopic changes were not observed, nor did cardiac or pulmonary findings change. Resting sea level Pao2 dropped to 51.5 mm Hg within three hours of ascent, and the Paco2 fell from 37.8 to 33.9 mm Hg. Over the next three days, the Pao2 increased to 54.5 mm Hg as hyperventilation continued. At exercise, sea level Pao2 dropped from a mean value of 63 to 46.8 mm Hg at altitude. Pulse rates at rest or exercise did not change. Normal values for 2,3-diphosphoglycerate (2,3-DPG) did not change after ascent at 16 and 42 hours. We believe aircraft flight or travel to moderate altitudes for this type of COPD patient is safe. Preexisting hypoxemia resulting from disease may facilitate the adaptation of patients to severe hypoxia and may prevent symptoms similar to acute mountain sickness.
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PMID:Short-term adaptation to moderate altitude. Patients with chronic obstructive pulmonary disease. 68 52

Chronic obstructive pulmonary disease continues to manifest an increasing prevalence in male Americans. A recent study of commercial airline pilots revealed a 12% prevalence of more-than-minor spirometric impairment. Because commensurate data were not available for general aviation pilots, in whom such impairment could also compromise flight safety, a parallel study was made. The BMRC and smoking questionnaires, chest expansion, and spirometric measurements of FEV1, FVC, FEV1%, MVV, and FFF 25-75% were assessed in 181 male general aviation pilots. All showed a general relationship to increasing age and smoking amount. Based on FEV1% and FEF 25-75% combined, minor or more-than-minor degrees of spirometric impairment were manifested by 25.4% of the pilots and moderate degrees by 12.7%. Very little impairment was reflected in the remaining spirometric parameters. Subsequent testing of such spirometrically impaired pilots for altitude, fatigue, and orthostatic tolerances related to general aviation flight safety is planned.
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PMID:Spirometric assessment of potential respiratory impairment in general aviation airmen. 86 36

In normal subjects the sensation of general fatigue subjectively limits the physical performance, whereas in patients with reduced respiratory function the sensation of breathlessness is the common limiting symptom. Patients with chronic obstructive lung disease may adopt an intermittent exercise pattern (e.g. when climibing stairs), in which the work periods are brief in duration but relatively high in intensity. The immediate ventilatory demand can in that way be reduced. The local metabolism of the working muscles can meet the increased demand, which demonstrates that peripheral factors are unlikely to limit the physical performance in these patients. For evaluating the importance of peripheral factors limiting the exercise tolerance of daily activities, such as stair-climbing or walking uphill, such activities should specifically be studied considerating also the exercise pattern shown by the patient. Even in bronchitic patients with reduced arterial oxygen tension there are no evidence that the skeletal muscles are working under more anaerobic conditions than in normal persons at the same relative work load. The blood lactate as related to the heart rate usually lies within normal limits. In patients with respiratory failure, however, lack of energy supply from the energy rich compounds may develop. Thus, only in extreme situations can the exercise performance of the respiratory patients be expected to be specifically limited by peripheral factors. Physical inactivity leads to changes in the muscle metabolism as in normal persons with reduced aerobic capacity in the muscles. The specific effects of steroid treatment on the muscle function in patients with chronic obstructive disease have not been studied, but may be an important factor limiting muscular performance at certain types of exercises.
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PMID:Peripheral limiting factors during exercise in chronic lung diseases. 88 Mar 99

Ventilatory muscles can become fatigued, and this can contribute to respiratory failure. Patients with chronic obstructive lung disease may benefit from improving their ventilatory muscle endurance to improve resistance to fatigue. Ventilatory muscle endurance was measured in 30 normal subjects and 55 patients with cystic fibrosis by finding the highest level of normocapnic hyperpnea that could be sustained for 15 min. Subjects with cystic fibrosis had 36 per cent higher ventilatory muscle endurance than normal subjects, reflecting the chronic training stress of breathing against increased respiratory loads. Four normal subjects and 4 subjects with cystic fibrosis participated in a specific ventilatory muscle endurance training program consisting of 25 min per day of maximal normocapnic hyperpnea 5 days per week for 4 weeks. The cystic fibrosis patients who trained improved their ventilatory muscle endurance by 51.6 per cent, whereas the normal subjects who trained showed a 22.1 per cent increase in ventilatory muscle endurance. Seven subjects with cystic fibrosis participated in a 4-week physical activity training program consisting of at least 1.5 hours per day of intensive swimming and canoeing at summer camp. They increased their ventilatory muscle endurance by 56.7 per cent. There were no other pulmonary function changes. Ventilatory muscle endurance can be readily improved in cystic fibrosis equally well by specific ventilatory muscle endurance exercise.
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PMID:Ventilatory muscle endurance training in normal subjects and patients with cystic fibrosis. 92 Oct 61

The hypothesis that patients with chronic obstructive pulmonary disease (COPD) have chronic inspiratory muscle fatigue was tested in an effectiveness trial in which negative pressure ventilation (NPV) was used to produce inspiratory muscle rest. In a double-blind study 184 patients with severe COPD were randomly allocated active or sham NPV treatment for a 12-week period of home use. The distance walked in a 6 min walk test was the primary outcome variable. Secondary outcome measures were cycle exercise endurance time, severity of dyspnoea, quality of life, arterial blood gas tensions, and respiratory muscle strength. The percentage reduction in amplitude of the diaphragmatic electromyographic signal multiplied by hours of NPV was used to reflect the dose of NPV so we could examine dose-response relations. Analysis was based on intention to treat. We found no evidence of a clinically or statistically significant difference in any outcome measure between active and sham groups. No dose-response relation was observed. Moreover, the intervention was poorly accepted despite substantial clinical support. We conclude that NPV as used in this study is difficult to apply and ineffective when used with the aim of resting the respiratory muscles in patients with stable COPD.
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PMID:Effect of negative pressure ventilation in severe chronic obstructive pulmonary disease. 136 May 64

Role of inspiratory muscle function in the genesis of dyspnea in COPD patients has yet to be fully studied. The present study investigated the possible relationship between respiratory muscle function and the sensation of dyspnea (modified Borg Scale) during exercise in eight patients with severe COPD (FEV1 0.61L +/- 0.15L). The electrical activity of the diaphragm (EMGdi) was recorded with esophageal electrodes, and that of sternomastoid muscle (EMGsm) was recorded from the surface electrodes. The ratio of high frequency (150 to 350 Hz) to low frequency (20 to 47 Hz) power (H/L) of EMGdi and EMGsm was analyzed to assess inspiratory muscle fatigue, which was determined by a 20% fall of H/L ratio from the control value. Flow, volume, esophageal (Pes) and transdiaphragmatic pressure (Pdi) were measured. Tension time index (TTdi) was calculated from Pdi and the ratio of inspiratory time to total time for one cycle (T1/TTOT). At rest, we measured maximal esophageal pressure (Pesmax), maximal transdiaphragmatic pressure (Pdimax), maximal EMGdi (EMGdimax) and EMGsm (EMGsmmax). Progressive treadmill exercise test was performed, stating with 3 minutes' walk at a speed of 0.75 mph at 0% grade, subsequently increasing the velocity at a rate of 0.25 mph and the elevation at a rate of 4% per stage. Exercise was discontinued at maximum respiratory effort sensation. Six of the eight patients showed diaphragmatic fatigue at their maximal exercise. With diaphragmatic fatigue, these patients were extremely dyspneic (Borg scale 9 or 10), and terminated the exercise. There were high correlations between the Borg scale and VE/MVV, and Pes/Pesmax and EMGsm/EMGsmmax, however, TTdi and EMGdi/EMGdimax showed less correlation with the Borg scale.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Dyspnea and inspiratory muscle function during exercise in severe chronic obstructive pulmonary disease (COPD)]. 140 99

Acute diaphragmatic fatigue has been experimentally shown to occur in normal healthy subjects and in patients with chronic obstructive pulmonary disease by asking them to modify their pattern of breathing or to breathe against high inspiratory resistances. During the expulsive period of labor women are asked periodically to make strong expulsive efforts and to sustain them isometrically for many seconds; this is likely to produce "natural" diaphragmatic fatigue. To investigate whether this was the case, six women were studied in the delivery room from the moment of the rupture of the amnion until delivery of the infant occurred. The development of diaphragmatic fatigue was assessed both by measuring the static maximal inspiratory pressure (MIP) and by analyzing the electromyographic power spectrum of the diaphragm (H/L ratio). The majority of contractions were concentrated in the expulsive period of labor. MIP, recorded in the supine position, significantly decreased from 103.2 +/- 17.2 cm H2O (at the beginning of the expulsive period) to 73.8 +/- 10.1 cm H2O (after the delivery). The H/L ratio fell progressively during the expulsive period; after the delivery, it was 59.2 +/- 15.7% of the value recorded at the beginning of the expulsive period. This study demonstrates that (1) the diaphragm is active in the expulsive efforts during labor and (2) the tension developed and the time each contraction is maintained may lead to the development of diaphragmatic fatigue. Therefore, we provide evidence of acute diaphragmatic fatigue in a natural condition.
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PMID:Evidence of acute diaphragmatic fatigue in a "natural" condition. The diaphragm during labor. 144 75

With the objective to test the effect of intermittent and short term rest in respiratory muscles in patients with COPD and maintained hypercapnia we have studied 34 patients in a stable condition: 23 were part of the study group (Group I) and 11 were the control group (Group II). After a complete functional basal study, patients in Group I were treated with intermittent rest of their respiratory muscles, through a negative pressure external respirator--shield type--during three consecutive days. We got, in this study group, a significative improvement in the maximum inspiratory pressure measured at residual volume (PI max RV), which went from 66.6 +/- 15.9 to 71.2 +/- 15.2 (p < 0.005), as well as a lowering, also significative, of partial pressure of CO2 in arterial blood (PaCO2) and in expired air (EFCO2), which went from 55.2 +/- 7.2 to 52.3 +/- 3 (p < 0.0002) and 3.3 +/- 0.5 to 3.1 +/- 0.5 (p < 0.01), respectively. Maximum inspiratory pressure measured to functional residual capacity (PI max FRC) experienced an increase in the limit of statistical signification. Rest of the parameters did not significantly change. These results back the hypothesis that in stabilized COPD with CO2 retention, a chronic fatigue of respiratory muscles could exist, and that intermittent rest of these muscles could mean an hypercapnia diminution, due to the improvement in the function of respiratory muscles.
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PMID:[Short-term effects of respiration with external negative ventilation --shield-type respirator-- on the pulmonary function in COPD]. 833 62

Exercise performance and dyspnea in COPD patients have been shown to be improved with supplemental oxygen, although the exact mechanisms resulting in the improvement are still unclear. The purpose of the present study was to investigate a possible relationship between ventilatory muscle function and sensation of dyspnea (modified Borg Scale) during exercise on 20% O2 and 30% O2. Eight patients with COPD (FEV1 1.06 L +/- 0.30 L) exercised on a treadmill two times breathing compressed air or 30% oxygen with a one hour rest in between. The electrical activity of the diaphragm (EMGdi) was recorded with esophageal electrodes, and that of the sternomastoid muscle (EMGsm) was recorded from the fine wire electrodes. The ratio of high frequency (150 to 350 Hz) to low frequency (20 to 47 Hz) power (H/L) of EMGdi was analyzed to assess diaphragmatic fatigue, which was defined as a 20% fall of H/L ratio from the control value. Flow, volume, O2 Saturation (SaO2), esophageal pressure (Pes) and transdiaphragmatic pressure (Pdi) were measured. Tension time index (TTdi) was calculated from Pdi and the ratio of inspiratory time to total time for one cycle (Ti/Ttot). At rest, we measured maximal esophageal pressure (Pesmax), maximal transdiaphragmatic pressure (Pdimax), maximal integrated EMGdi (EMGdimax) and EMGsm (EMGsmmax). Incremental exercise was discontinued by dyspnea. The walking distance achieved was increased in all patients on 30% O2. Dyspnea and desaturation were significantly improved on 30% O2 breathing, and the onset of diaphragmatic fatigue was delayed.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Dyspnea and ventilatory muscle function during exercise on air and oxygen breathing in patients with chronic obstructive pulmonary disease (COPD)]. 150 86


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