Sternomastoid muscle function and fatigue in normal subjects and in patients with chronic obstructive pulmonary disease

Four normal subjects and 5 patients with chronic obstructive pulmonary disease (COPD) (mean FEV1, 1.03 L) had frequency:force curves of their sternomastoid muscle measured before and 5 min after a 12-min walk on a flat treadmill, a progressive exercise test (normal subjects only), and a 10-min period of sustained maximal voluntary ventilation (SMVV). Before each test, all subjects had a normal frequency:force curve, and the ratio of the force response at 20 Hz to that at 50 Hz was normal. After SMVV, all the normal subjects and 4 of the 5 patients developed a greater than 15% fall in 20:50 ratio, and this was taken to indicate the presence of low frequency fatigue (LFF). During SMVV, all the subjects achieved minute ventilation greater than 70% of predicted maximal breathing capacity (MBC). During the 12-min walk, all the patients exceeded 70% MBC, and 4 developed LFF. The normal subjects performing progressive exercise also exceeded 70% MBC, and all showed LFF. The 12-min walk did not cause LFF in the normal subjects, but no subject reached 70% of MBC. Despite the presence of LFF in the sternomastoid muscle, the patients were all able to walk the same distance during a second 12-min walk. In both the normal and patient groups, the ventilatory response to CO2 was not changed by the presence of LFF. There were no changes in maximal inspiratory and expiratory mouth pressures or spirometry with LFF. High, sustained levels of minute ventilation cause sternomastoid LFF, but the clinical significance of this phenomenon is not yet certain.     

Lung function disturbances versus respiratory muscle fatigue in patients with systemic lupus erythematosus

In 23 consecutive patients (mean age, 38.6 years) with systemic lupus erythematosus (SLE) and in 17 healthy subjects (mean age, 37.5 years) fatigue of respiratory (diaphragm, musculi intercostales externi) and leg muscles (musculus gastrocnemius) was determined comparatively by electromyography. Additionally, routine lung function parameters, including maximum inspiratory (PImax) and expiratory (PEmax) mouth pressures, were measured. The SLE patients showed lower values of vital capacity (VC), total lung capacity (TLC), thoracic gas volume (TGV), FEV1, PImax and PEmax than the healthy controls, while FEV1/VC, residual volume and specific airway conductance were not significantly different in either group. Lung compliance, corrected for TGV, was normal in the SLE group. Breathing through stenoses with increasing resistances resulted in fatigue of the diaphragm in 73% of the SLE group and in 41% of the control group. The corresponding values of the external intercostal muscles were 74% (SLE group) and 29% (control group). Electromyographic signs of respiratory and leg muscle fatigue occurred at lower loads in the SLE group than in the healthy subjects. The pattern of lung function data in patients with SLE was characteristic neither of lung restriction nor of airway obstruction. Respiratory muscle weakness can explain the decrease in TLC, VC, TGV, FEV1, PImax and PEmax.     

Effects of intermittent negative pressure ventilation on respiratory muscle function in patients with severe chronic obstructive pulmonary disease

The reduced respiratory muscle strength and increased work of breathing in patients with severe chronic obstructive pulmonary disease (COPD) may predispose these patients to the development of respiratory muscle fatigue and consequent respiratory failure. To test the hypothesis that these patients may be experiencing chronic respiratory muscle fatigue, we studied the effects of resting the respiratory muscles in a group of patients with severe COPD. Fifteen stable patients with severe COPD were randomized into study and control groups. In 8 study group patients (Group B), breathing was assisted with a negative pressure ventilator 3 to 6 h daily for 3 consecutive days. The remaining 7 patients served as controls (Group A) and did not receive any intervention. Baseline lung function was evaluated by spirometry and arterial blood gas determinations. Respiratory muscle strength and endurance were evaluated by maximal inspiratory and expiratory pressures (MIP and MEP, respectively) and the maximal duration that isocapnic hyperventilation equal to 50 and 70% of the 12-s maximal voluntary ventilation could be sustained (DSV). Baseline DSV was determined as the best effort of several practice trials. All measurements were repeated on the final day of assisted ventilation approximately 2 to 3 h after its discontinuation. After assisted ventilation, the DSV at 50 and 70% of the maximal voluntary ventilation improved significantly (p less than 0.05). Maximal inspiratory pressure and MEP increased to 114% (p less than 0.05) and 112% (p = 0.05) of baseline values, respectively. Mean arterial PCO2 in the hypercapnic subgroup of Group B patients decreased from 60 mm Hg before to 52 mm Hg after assisted ventilation (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inspiratory muscle function in patients with severe kyphoscoliosis

In 9 patients with severe kyphoscoliosis we studied inspiratory muscle function by measuring transdiaphragmatic pressure (Pdi) and its components: gastric (Pga) and esophageal (Pes) pressures during quiet breathing. Maximal Pdi and maximal inspiratory mouth pressure (Pimax) were also measured. The results showed that Pimax and Pdimax were significantly lower in patients than in normal subjects. During quiet breathing, all patients had positive swings in Pga, indicating an active contraction of the diaphragm, but Pes was significantly more negative, suggesting the recruitment of intercostal and accessory inspiratory muscles. We did not find significant correlations between Pimax, Pdimax, delta Pga/delta Pes, FVC, PaO2, or PaCO2 and the degree of spinal deformity. The FVC tended to correlate with Pimax (r = 0.63) and with Pdimax (r = 0.53). The Pdi correlated with PaO2 (r = 0.66) and with PaCO2 (r = -0.76; p less than 0.05). A significant correlation was also observed between Pimax and PaO2 (r = 0.785; p less than 0.05) and between Pimax and PaCO2 (r = -0.86; p less than 0.01). We conclude that impairment of inspiratory muscle function is related to the development of ventilatory failure in kyphoscoliosis.     

SARS患者甲状腺功能检测分析

测定 8例严重急性呼吸综合征 (SARS)患者血浆甲状腺激素水平。结果显示这些患者的血浆TT3 、FT3 下降 ,rT3 升高 ,符合低T3 综合征诊断。     

Targeted inspiratory muscle training improves respiratory muscle function and reduces dyspnea in patients with chronic obstructive pulmonary disease

STUDY OBJECTIVE: To examine the effects of targeted inspiratory muscle training on respiratory muscle function, clinical ratings of dyspnea, and perception of resistive loads in symptomatic patients with chronic obstructive pulmonary disease. DESIGN: Randomized, placebo-controlled trial with an 8-week treatment period. SETTING: Outpatient pulmonary clinic and pulmonary function laboratory. PARTICIPANTS: We studied 19 patients with moderate to severe chronic obstructive pulmonary disease, assigning 10 patients to an experimental group and 9 to a control group. INTERVENTIONS: Patients in both groups trained for 15 minutes twice each day using a device that provided breath-to-breath visual feedback of training intensity. Patients in the experimental group trained at six increasing levels of inspiratory resistance, whereas the patients in the control group trained at a constant, nominal level of resistance. MEASUREMENTS AND RESULTS: Although there was no statistically discernible difference in the effects of targeted muscle training on the mean difference in maximal inspiratory pressures between the two groups (9.83 cm H2O; 95% CI, -7.37 to 27.03), patients in the experimental group did show a significant increase in inspiratory muscle strength (15.03 cm H2O; P = 0.01). Experimental subjects also had decreased dyspnea after 8 weeks of training compared with control subjects (P = 0.003). Improvements in physiologic values and in dyspnea ratings were correlated. The perception of added resistive loads was not affected by inspiratory muscle training. CONCLUSIONS: Targeted inspiratory muscle training may enhance respiratory muscle function and reduce dyspnea in symptomatic patients with moderate to severe chronic obstructive pulmonary disease.     

Tracheal occlusion pressure: a simple index to monitor respiratory muscle fatigue during acute respiratory failure in patients with chronic obstructive pulmonary disease

STUDY OBJECTIVE: To assess respiratory muscle fatigue in acute respiratory failure in patients with chronic obstructive pulmonary disease and evaluate its influence on weaning patients from mechanical ventilation. DESIGN AND PATIENTS: We studied the time course of tracheal occlusion pressure (P0.1) and high-to-low ratio of the diaphragmatic electromyogram in 16 patients in acute respiratory failure with chronic obstructive pulmonary disease. METHODS: All patients were intubated and studied during a 15-minute weaning period from ventilation. Minute ventilation (VE), arterial blood gases, P0.1 and high-to-low ratio of the diaphragm were measured every day from the onset to the end of acute failure (before extubation) at 5 and 15 minutes into the weaning period. The diaphragmatic electromyogram was recorded with an esophageal electrode and the high-to-low ratio of the electrical signal analyzed to assess diaphragmatic fatigue. MEASUREMENTS AND MAIN RESULTS: In all patients P0.1 was markedly increased (7.1 +/- 2.4 cm H2O, mean +/- SE) on the first day of acute failure and did not change during weaning. In 11 patients, P0.1 had decreased to 4.7 +/- 1.8 cm H2O (P less than or equal to 0.002) before extubation (which was done after 5 to 9 days). In these patients, the high-to-low ratio of the diaphragm decreased rapidly-during the first minutes of weaning on the first day of acute failure and remained low throughout weaning, whereas before extubation no decrease in high-to-low ratio was seen during weaning. In 5 patients, P0.1 did not change significantly from the onset of acute failure and the high-to-low ratio remained low before extubation. These 5 patients had to be reintubated within 2 to 6 days. In both groups of patients, VE did not change significantly from the first to last day of acute failure (10.3 +/- 3 compared with 10.7 +/- 2.1 min-1), whereas blood gases during room air breathing improved significantly from the first to last day of acute failure, respectively, in each group (arterial oxygen pressure [PaO2], 33.5 +/- 1.5 compared with 44 +/- 9 mm Hg (P less than or equal to 0.05) and PaO2 56 +/- 2.3 compared with 49 +/- 2 mm Hg (P less than 0.005). CONCLUSIONS: Extubation should not be done in patients with respiratory muscle fatigue despite improvement in arterial blood gases and clinical status; and P0.1 provides a valid and simple index to assess the likelihood of respiratory muscle fatigue.     

Oxidative stress and respiratory muscle dysfunction in severe chronic obstructive pulmonary disease

RATIONALE: Oxidative stress is involved in the skeletal muscle dysfunction observed in patients with severe chronic obstructive pulmonary disease (COPD). We hypothesized that the diaphragms of such patients might generate greater levels of oxidants than those neutralized by antioxidants. OBJECTIVES: To assess the levels of both oxidative and nitrosative stress and different antioxidants in the diaphragms of those patients, and to analyze potential relationships with lung and respiratory muscle dysfunctions. METHODS AND MEASUREMENTS: We conducted a case-control study in which reactive carbonyl groups, hydroxynonenal-protein adducts, antioxidant enzyme levels, nitric oxide synthases, and 3-nitrotyrosine formation were detected using immunoblotting and immunhistochemistry in diaphragm specimens (thoracotomy) obtained from six patients with severe COPD, six patients with moderate COPD, and seven control subjects. MAIN RESULTS: Diaphragms of patients with severe COPD showed both higher protein carbonyl groups and hydroxynonenal-protein adducts than control subjects. When only considering patients with COPD, negative correlations were found between carbonyl groups and airway obstruction, and between hydroxynonenal-protein adducts and respiratory muscle strength. Although diaphragmatic neuronal nitric oxide synthase did not differ among the three groups and no inducible nitric oxide synthase was detected in any muscle, muscle endothelial nitric oxide synthase was lower in patients with severe COPD than in control subjects. Muscle nitrotyrosine levels were similar in both patients with severe COPD and control subjects. CONCLUSIONS: This study shows that oxidative stress rather than nitric oxide is likely to be involved in the respiratory muscle dysfunction in severe COPD.     

Home respiratory muscle training in patients with chronic obstructive pulmonary disease

OBJECTIVE AND BACKGROUND: The benefits of inspiratory muscle strength training in decreasing symptoms, disability or handicap of patients affected by COPD are not well established. The objective of this study was to assess the efficacy of the constant use of a new flow-volumetric inspiratory exerciser, named Respivol, in improving respiratory functional parameters in COPD patients. METHODS: Twenty consecutive ambulatory patients affected by COPD were enrolled. Each patient was assessed, before and after 3 and 6 months inspiratory exercise with Respivol, for the following clinical parameters: maximal inspiratory pressure, maximal expiratory pressure, dyspnoea grade, quality of life by a self-administered St George questionnaire and a 6-min walking test. After a brief progressive ambulatory training programme, inspiratory exercise with Respivol was performed at home for 6 months. All patients used Respivol together with medical treatment. RESULTS: Maximal inspiratory pressure and maximal expiratory pressure values were significantly increased after 3 and 6 months of exercise. Dyspnoea grade was significantly reduced and the 6-min walking test showed an increase in effort tolerance, after 6 months of home training. Quality of life assessment showed an improvement, associated with a decrease of respiratory disease symptoms. CONCLUSIONS: Inspiratory muscle strength training with Respivol seems to be efficient in reducing symptoms and improving quality of life in adults with COPD.     

Exercise training increases respiratory muscle strength and exercise capacity in patients with chronic obstructive pulmonary disease and respiratory muscle weakness

BackgroundHow respiratory muscle strength influences the effectiveness of pulmonary rehabilitation (PR) in patients with chronic obstructive pulmonary disease (COPD) is unclear.ObjectiveTo investigate the benefits of PR in subjects with COPD according to respiratory muscle strength.MethodsNinety-seven subjects with COPD were evaluated using maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), pulmonary function tests, the cardiopulmonary exercise test (CPET), and the St. George's Respiratory Questionnaire (SGRQ). Subjects were divided into four groups: 1 (normal MIP and MEP); 2 (low MIP); 3 (low MEP); and 4 (low MIP and MEP). Subjects underwent PR for 3 months; MIP, MEP, SGRQ, and CPET were evaluated post-PR.ResultsSubjects with both poor MIP and MEP had the highest dyspnea score, lowest exercise capacity, and poorest health-related quality of life (HRQoL). PR improved exercise capacity and HRQoL in all groups, with more improvement in MIP, MEP, tidal volume (on exercise), and dyspnea (at rest) in subjects with both low MIP and MEP.ConclusionsPatients with respiratory muscle weakness had worse dyspnea, lower exercise capacity, and poorer HRQoL at baseline. Exercise training improved respiratory muscle strength with concurrent improvement of exercise capacity, HRQoL, and dyspnea score. Subjects with both poor baseline MIP and MEP showed greater benefits of PR.     

Abnormalities of the peripheral circulation and respiratory function in patients with severe heart failure

To investigate the peripheral circulatory and respiratory abnormalities which occur in patients with heart failure, forearm and calf blood flow were measured before and after upright exercise, and respiratory gas exchange was measured during exercise in 26 patients with severe heart failure. Compared with a group of normal subjects the patients had reduced limb blood flow at rest and the response of limb blood flow to upright exercise was also abnormal. The increase in calf blood flow after exercise and the reduction in blood flow in the non-exercising forearm were both smaller in patients than in controls. There was a significant correlation between the maximum exercise duration of the patients and calf blood flow both after exercise and at rest. Compared with another group of control subjects the patients had a higher minute ventilation during exercise and a reduced oxygen consumption. The respiratory exchange ratio during exercise was also higher in patients than in controls. This suggests that there is early onset of anaerobic metabolism during exercise in patients with severe heart failure.     

帕金森病患者躯体疲劳与运动功能的相关性分析

目的 观察帕金森病(PD)患者躯体疲劳症状与运动功能的相关性.方法 按照统一的入选和排除标准,选取36例诊断明确的老年PD患者,其中男性22例,女性14例;同时选取年龄、性别相匹配的健康人18名作为对照,分别进行PD疲劳量表评定(PFS)、起立行走时间、6min最大步行距离试验.对比两组评测结果,在PD组内对PFS得分与运动功能水平进行相关性分析.结果 PFS得分、起立行走时间和6 min最大步行距离在PD组与健康对照组之间差异有统计学意义(P＜0.05);PD患者PFS得分与起立行走时间存在正相关性(r=0.82,P＜0.01),和6 min最大行走距离呈负相关(r=-0.61,P＜0.01); 结论与年龄性别相匹配的健康人相比,PD患者存在明显的躯体疲劳症状;PD患者躯体疲劳症状与运动功能减退呈正相关.     

Changes in respiratory muscle function after neostigmine injection in patients with myasthenia gravis

In sixteen patients with myasthenia gravis, the weakness of respiratory muscles, especially of expiratory, caused some disturbances in lung function. Thirty minutes after injection of neostigmine, general improvement of muscle function was accompanied by an increase of strength and endurance of respiratory muscles. The mean value of maximal inspiratory mouth pressure (PImax) increased by 33%, maximal expiratory mouth pressure (PEmax) by 23.5% and maximal voluntary ventilation (MVV) by 21%. As a consequence of these changes amelioration of lung function indices was found, vital capacity increasing on average by 13% and residual volume decreasing by 12.5%. We concluded that patients with generalized myasthenia gravis have disturbances in lung function which may be partially improved by neostigmine injection or other anticholinesterase agents.