Measurement Of Respiratory Muscle Strength Research Articles

The effect of fixed load incremental inspiratory muscle training in the elite athlete: a pilot study

This study sought to investigate whether a regime of high density inspiratory muscle training (IMT) would increase respiratory muscle strength (RMS) and respiratory muscle endurance (RME) in maximally trained subjects. Twelve endurance athletes (nine men) with a mean age of 25 years (±5·6 S.D.) were selected for a three times weekly training programme, performed over 8 weeks. Using a computerized system, subjects were required to perform three sustained maximal inspiratory efforts (SMIP) from residual volume to total lung capacity, and to subsequently attain repeated sub maximal pressure profiles at progressively reduced time intervals. With the use of biofeedback, subjects were required to match or exceed a pressure curve which was derived by reducing the best SMIP to 80% of peak at each training session. Maximal inspiratory pressure (MIP) values were recorded as measures of RMS. SMIP values were calculated in arbitrary pressure/time units (PTUs). RME was expressed as summated PTUs at programme completion. These results demonstrate a significant increase in RMS (P<0·001) and RME (P<0·0001) with a reported decrease in exertional dyspnoea. We conclude that this method of incremental IMT, which is set at a level consistent with high density training regimes, increases RMS and RME in highly trained subjects. These results also suggest that the application of this regime may result in greater pressure generation at higher lung volumes thereby affecting the length/tension relationship of the inspiratory muscles and hence ameliorate dyspnoea during periods of sustained aerobic performance.

Respiratory Muscle Strength and Endurance Following a CVA

Most adults diagnosed with cerebrovascular accidents (CVA) receive rehabilitation services to maximize their functional independence. However, few reports specifically address respiratory muscle strengthening following a CVA. The purpose of this pilot study was to compare the pulmonary function of adults following their first CVA with established normal adult standards to explore whether respiratory muscle strength and endurance are depressed following an initial CVA. Thirteen adults 40-60 years of age admitted to the rehabilitation unit within 3 weeks of having their first CVA participated in the pilot study. Pulmonary function was tested using negative inspiratory force (a measure of respiratory muscle strength), maximal voluntary ventilation (a measure of respiratory muscle endurance), and forced vital capacity (a measure of maximal voluntary output). Paired samples t-test analysis showed a significant difference (p<0.002) between predicted and actual pulmonary function test values. The results indicate that respiratory muscle strengthening should be included in the medical management of adults following a CVA.

Effect of lung volume reduction surgery on diaphragm strength.

Since lung volume reduction surgery (LVRS) reduces end-expiratory lung volume, we hypothesized that it may improve diaphragm strength. We evaluated 37 patients for pulmonary rehabilitation and LVRS. Before and 8 wk after pulmonary rehabilitation, 24 patients had spirometry, lung volumes, diffusion capacity, incremental symptom limited maximum exercise test, 6-min walk test, maximal static inspiratory and expiratory mouth pressures, and transdiaphragmatic pressures during maximum static inspiratory efforts and bilateral supramaximal electrophrenic twitch stimulation measured. Twenty patients (including 7 patients who crossed over after completing pulmonary rehabilitation) had baseline measurements postrehabilitation, and 3 mo post-LVRS. Patients were 58 +/- 8 yr of age, with severe COPD and hyperinflation (FEV1, 0.69 +/- 0.21 L; RV, 4.7 +/- 1.4 L). Nineteen patients had bilateral LVRS performed via median sternotomy and stapling, and 1 patient had unilateral LVRS via thorascopy with stapling. After rehabilitation, spirometry and DL(CO)/VA were not different, and lung volumes showed a slight worsening in hyperinflation. Gas exchange, 6-min walk distance, maximum oxygen uptake (VO2max), and breathing pattern during maximum exercise did not change after rehabilitation, but total exercise time was significantly longer. Inspiratory muscle strength (PImax, Pdi(max combined), Pdi(max sniff), Pdi(max), Pdi(twitch)), was unchanged after rehabilitation. In contrast, after LVRS, FVC increased 21%, FEV1 increased 34%, TLC decreased 13%, FRC decreased 23%, and FRC(trapped gas) and RV decreased by 57 and 28%, respectively. PCO2 was lower (44 +/- 6 versus 48 +/- 6 mm Hg, p < 0.003) and 6-min walk distance increased (343 +/- 79 versus 250 +/- 89 m, p < 0.001), as did total exercise time during maximum exercise (9.2 +/- 1.9 versus 6.9 +/- 2.7 min, p < 0.01). Minute ventilation (29 +/- 8 versus 21 +/- 6 L/min, p < 0.001) and tidal volume (1.0 +/- 0.33 versus 0.84 +/- 0.25 L, p < 0.001) during maximum exercise increased whereas respiratory rate was lower (28 +/- 6 versus 32 +/- 7 breaths/min, p < 0.02). Measurements of respiratory muscle strength (PImax, 74 +/- 28 versus 50 +/- 18 cm H2O, p < 0.002; Pdi(max combined), 80 +/- 25 versus 56 +/- 29 cm H2O, p < 0.01; Pdi(max sniff), 71 +/- 7 versus 46 +/- 27 cm H2O, p < 0.01; Pdi(twitch), 15 +/- 5 versus 7 +/- 5 cm H2O, p < 0.01) were all greater post-LVRS. Inspiratory muscle workload as measured by Pdi TTI was lower following LVRS (0.07 +/- 0.02 versus 0.09 +/- 0.03, p < 0.03). On multiple regression analysis, increases in PImax correlated significantly with decreases in RV and FRC(trapped gas) after LVRS (r = 0.67, p < 0.03). We conclude that LVRS significantly improves diaphragm strength that is associated with a reduction in lung volumes and an improvement in exercise performance. Future studies are needed to determine the relationship and stability of these changes over time.

Influence of Autonomic Neuropathy of Different Severities on the Hypercapnic Drive to Breathing in Diabetic Patients

To investigate the effects of the autonomic nervous system on control of breathing, the neuromuscular (mouth occlusion pressure at 0.1 s after onset of inspiration [P0.1]) and ventilatory (minute ventilation [VE]) response to progressive hyperoxic hypercapnia was assessed in diabetic patients with autonomic dysfunction of different severity. Eighteen diabetics with autonomic neuropathy, nine with parasympathetic damage (DANp), and nine with parasympathetic and sympathetic damage (DANp+s), as indicated by marked postural hypotension, low increment of diastolic BP during sustained handgrip, and lowest resting catecholamine plasma levels, were studied together with a group of 10 diabetic patients without autonomic neuropathy (D) and a group of 10 normal subjects (C). All subjects had pulmonary function tests, including maximal voluntary ventilation and diffusion of carbon monoxide, measurements of respiratory muscle strength as maximal inspiratory mouth pressure (MIP) and maximal expiratory mouth pressure (MEP), and a CO2 rebreathing test (Read's method). Although in the normal range, lung volumes and FEV1 and forced expiratory flows were lower in the DANp and DANp+s groups than in the D and C groups, MIP and MEP were similar among C and diabetic groups, as well as resting P0.1, VE, tidal volume (VT), and respiratory rate (RR). The slope of the linear relationship between P0.1 and end-tidal PCO2 (PETCO2) was higher in DANp+s (0.63+/-0.07 cm H2O/mm Hg) than in C (0.45+/-0.06 cm H2O/mm Hg; p<0.05) and three times greater in DANp+s than in D (0.26+/-0.03 cm H2O/mm Hg; p<0.001) and DANp (0.24+/-0.03 cm H2O/mm Hg; p<0.001), who in turn showed a lower deltaP0.1/deltaPETCO2 than C. The VE increase with increasing PETCO2 was greater in DANp+s (3.70+/-0.85 L/min/mm Hg) than in DANp (2.13+/-0.20 L/min/mm Hg; p<0.05) and D (2.37+/-0.40 L/min/mm Hg; p=0.07), but not significantly higher from that of C (3.17+/-0.36 L/min/mm Hg). No differences were found for deltaVT/deltaPETCO2 among the groups, whereas the deltaRR/deltaPETCO2 relationship was steeper in DANp+s than in DANp (p<0.05) and D (p=0.055). These data reflect a depressed CO2 response both in D and DANp. The presumable decrease of the sympathetic nerve traffic in DANp+s appears to reverse this abnormality. DANp+s, however, exhibit an enhanced CO2 neuromuscular response even in respect to C, suggesting that the sympathetic nervous system might modulate the output of the respiratory centers to hypercapnic stimulus.

Relationship between respiratory muscle function and quality of life in sarcoidosis.

In sarcoidosis, pulmonary and general symptoms often do not correlate with radiographic stage and routinely performed lung function tests. Asymptomatic muscle involvement in sarcoidosis is common, but little is known about respiratory muscle involvement. The aim of this study was to investigate any relationships between persistent complaints and/or quality of life and respiratory muscle strength and endurance, respectively. Measurements of maximal inspiratory and expiratory mouth pressures (PI,max and PE,max), respiratory muscle endurance and routine lung function were made in 18 patients with sarcoidosis. To assess health status and quality of life, patients completed the Sickness Impact Profile (SIP). Respiratory muscle strength and endurance time were lower in the patient group than in a group of healthy controls (p=0.05). Compared to a general population, the patients with sarcoidosis were found to be limited in physical and psychosocial functioning. The respiratory muscle endurance time correlated with the SIP subscales "mobility" (r=-0.56; p<0.01), and "body care and movement" (r=-0.79; p<0.001). The total lung capacity (TLC), inspiratory vital capacity (IVC) and forced expiratory volume in one second (FEV1) were normal in all subjects. In conclusion, patients with sarcoidosis and normal lung function showed reduced respiratory muscle strength and endurance time. Correlations were found between these indices and both symptoms and certain Sickness Impact Profile domains. Therefore, we suggest inclusion of measurements of respiratory muscle strength in the assessment and follow-up of patients with sarcoidosis.

Expiratory training in multiple sclerosis

Objective: To compare the effects of expiratory muscle training and sham training on respiratory muscle strength in patients with multiple sclerosis (MS). Design: A randomized control trial; subjects were randomly assigned to either expiratory muscle training or sham training. Setting: Training and measurement of respiratory muscle pressures were conducted in patients' homes. Weekly home visits were conducted to assure compliance with the training protocols and to obtain measurements. Patients: Twenty subjects with clinically definite MS and decreased expiratory muscle strength entered the study; 10 subjects completed 3 months of expiratory training using a threshold training device and 5 subjects completed 3 months of sham training using the same device but without an expiratory training threshold load. Measurement: Respiratory muscle strength was assessed at baseline and after 1, 2, and 3 months of training; maximal inspiratory and expiratory pressures were used as measures of respiratory muscle strength. results: There was a significant increase in expiratory muscle strength after 3 months of training when the expiratory training group was compared to the sham group ( p = .003); no significant change in inspiratory muscle strength was observed. Conclusions: The results of this pilot study suggest that the strength of the expiratory muscles of persons with MS can be increased through respiratory muscle training targeted to the expiratory muscles. Further research is indicated to determine if increasing the strength of the expiratory muscles in MS has an effect on clinical outcomes in this patient population.

Respiratory muscle training

This article describes the various forms of respiratory muscle training and discusses the advantages of each approach. Measurements of respiratory muscle strength and endurance are described, and the limitations of each approach outlined. Finally, published data are briefly examined and suggestions for future research and clinical interventions proposed.

Assessment of respiratory muscle strength in the intensive care unit

The measurement of respiratory muscle strength in the intensive care unit (ICU) is potentially useful for the prediction of weaning outcome. An easy and accurate measure would also allow investigation of respiratory muscle weakness in critically ill patients. At present, there is no satisfactory method of strength measurement in the intensive care unit. Vital capacity is a nonspecific, volitional and relatively insensitive measure of strength. True maximum respiratory pressures are difficult to achieve and, in stable patients, results vary greatly both over time and between observers. For these reasons, there are few good data of respiratory muscle strength in the intensive care unit. Of the new techniques being developed, magnetic stimulation of the phrenic nerves, combined with the measurement of transdiaphragmatic, oesophageal, or endotracheal tube pressure, offers the greatest promise.

Maternal respiratory function following normal vaginal delivery

Forced expiratory volume (FEV 1) forced vital capacity (FVC), peak expiratory flow (PEF) and maximum expiratory pressure (P Emax) were measured in 11 healthy women 2, 4, 8, 24, 48 and 72 hours after normal vaginal delivery and repeated after 6–8 weeks. There was a significant ( P<0.05) reduction in the P Emax up to 4 hours after delivery. In contrast, there was no significant reduction in FEV 1 or FVC at any of the time periods, and PEF showed a significant reduction only at 2 hours after delivery. This indicates that P Emax is a more sensitive measure of respiratory muscle strength and that this is reduced for at least 4 hours after delivery. Any anaesthetic given during this period should take into consideration that the ability to cough effectively may be impaired.

Pulmonary Function at Diagnosis of Amyotrophic Lateral Sclerosis: Rate of Deterioration

The purpose of this study was to determine the degree of respiratory muscle impairment in patients with newly diagnosed amyotrophic lateral sclerosis (ALS) and the subsequent rate of decline of respiratory function. Thirty-one of 36 patients had respiratory muscle weakness at presentation, although only 7 complained of any respiratory symptoms. Vital capacity (percent predicted) was significantly lower in the symptomatic group (55.9 +/- 20.3) compared with the asymptomatic group (76.4 +/- 21.0). Respiratory muscle impairment as measured by vital capacity (percent predicted) was related to stage of disease at presentation. Rate of decline of respiratory muscle strength as measured by VC (-3.5 percent/month), negative inspiratory pressure (NIF) (+2.9 cm H2O/month), and positive expiratory pressure (PEP) (-3.4 cm H2O/month) tended to be linear with a great deal of interpatient variability. It is concluded that early measurement of respiratory muscle strength in ALS with subsequent follow-up studies may be useful in determining overall prognosis and in decision making.

Hypoxia episodes during sleep in high tetraplegia.

To determine whether oxygen desaturation occurs during sleep in high tetraplegics, 10 neurologically stable male patients (aged 17 to 55 years) with complete motor lesions (C4 to C6) had continuous pulse oximetry recordings and sleep observations on two nights. The patients were studied during admissions for nonrespiratory problems (eg, pressure sores, urinary infection, respite). Lung function tests and daytime arterial blood gases were also measured. Mean forced vital capacity was 46% of predicted, but mean awake PaO2 and PaCO2 were normal (95.0 mmHg and 42.8 mmHg, respectively). Three subjects showed severe nocturnal oxygen desaturation spending greater than 10% of the time overnight with arterial oxyhaemoglobin saturation (SaO2) levels of less than 90%. For the group as a whole, the percentage of time spent under 90% SaO2 correlated with body mass index. Mean overnight SaO2 correlated inversely with body mass index and directly with maximal expiratory pressure, a measure of respiratory muscle strength. Low overnight SaO2 was also associated with higher levels of injury. The pattern of nocturnal oxygen desaturation observed was episodic and was suggestive of obstructive sleep apnoea during rapid eye movement (REM) sleep. Levels of nocturnal oxygen desaturation similar to those observed in the three most severely affected patients have been shown, in other disorders, to be associated with cognitive impairment, cardiovascular disease and increased mortality. Our results suggest up to a third of high tetraplegics may be at risk of potentially serious nocturnal hypoxic episodes.

Respiratory Function in Multiple Sclerosis: Utility of Clinical Assessment of Respiratory Muscle Function

The aim of this study was to assess the utility of clinical assessment of respiratory muscle weakness in MS. We studied 40 MS patients who performed pulmonary function tests using standard procedures and measures of respiratory muscle strength. Descriptive clinical indices included a history of detailed neurologic findings, including upper and lower extremity weakness, cerebellar signs, and evidence of cerebral lesions and other clinical signs including dependence in activities of daily living, shortness of breath, weak voice, dysarthria and dysphagia. We devised an index comprised of four clinical signs: the patient's report of difficulty in clearing pulmonary secretions and his report of a weakened cough, the examiner's observation of the patient's cough, and ability to count on a single exhalation. Mean values of TLC (95 percent +/- 14) VC (91 percent +/- 19), and RV (106 percent +/- 34) were normal. By contrast, MVV (68 percent +/- 20), PImax (74 percent +/- 27) and PEmax (51 percent +/- 22) were decreased. Stepwise multiple regression indicated that the best single predictor of expiratory muscle weakness was the index score; the combination of index score, upper extremity weakness, and maximal voluntary ventilation accounted for 60 percent of the variance in PEmax. We conclude that clinical assessment is a better predictor of respiratory muscle weakness than spirometry and that a systematic clinical assessment supplemented by respiratory muscle assessment and MVV can uncover subtle respiratory muscle weakness in patients with MS.

Pulmonary Function in Individuals with a History of Poliomyelitis

We examined the relationship between the lung function of 74 individuals with a history of poliomyelitis and reports of shortness of breath during activities of daily living, and the presence of post-polio sequelae risk factors. First, we studied the spirometry of 60 individuals (group 1) and second, we studied the relationship between the spirometry of an additional 14 individuals (group 2) and their respiratory muscle strength (Pimax and Pemax). In both groups, we examined the relationship between factors associated with post-polio sequelae including ventilation at polio-onset, having contracted polio after the age of 10, and having had polio for over 35 years; and lung function. In group 1, the FEV1 and FVC were lower for individuals with shortness of breath than individuals without (p less than 0.01). With respect to risk factors, FEV1 and FVC were lower in individuals who were ventilated at polio-onset, in individuals who contracted polio over 10 years of age, and in individuals who had had polio for less, rather than more than 35 years (p less than 0.05). The results for group 2 were comparable to group 1. In addition, the observed Pimax and Pemax were significantly lower than predicted values (p less than 0.05). Although FEV1 and FVC were positively correlated with both Pimax and Pemax (p less than 0.05), Pemax was disproportionately impaired compared to Pimax (40 +/- 12.1 and 82 +/- 38.8 percent predicted respectively). We conclude that individuals with a history of poliomyelitis can have compromised lung function irrespective of shortness of breath, that risk factors such as ventilation at polio-onset and polio-onset after 10 years of age can help predict those at risk of respiratory compromise, and that the measurement of respiratory muscle strength and of Pemax in particular, can augment the assessment of lung function of these individuals. Such assessment may avert respiratory complications in the post poliomyelitis population including those secondary to health care interventions.

Respiratory muscle function in myasthenia gravis.

Global respiratory muscle function and diaphragmatic strength were assessed and compared with quadriceps femoris muscle strength in 17 patients with generalized mild-to-moderate myasthenia gravis and breathlessness. Initial measurements, made 10 h after the last dose of oral anticholinesterase therapy, demonstrated reduced maximal static expiratory (52.4 +/- 26.8% predicted) and inspiratory (54.0 +/- 23.5% predicted) mouth pressures in 16 patients, and reduced quadriceps femoris muscle strength in all cases. Vital capacity (VC) (70.9 +/- 19.0% predicted) was abnormal in 12 patients. Transdiaphragmatic pressure recorded during maximal sniffs (sniff Pdl) was reduced in eight patients, whereas pressure recorded during bilateral phrenic nerve stimulation at 1 Hz (twitch Pdi) was reduced in only three. There was no relationship between the grade of myasthenia or the severity of dyspnea and any of the measurements of respiratory muscle strength. After the administration of edrophonium hydrochloride (Tensilon), there was a significant increase in maximal static expiratory and inspiratory mouth pressures in quadriceps muscle strength and in sniff Pdi. The small increase in VC was not significant, and twitch Pdi increased in only one patient. Phrenic nerve conduction time was normal before and after Tensilon. Two patients with severe long-standing myasthenia showed no improvement in any measurement after Tensilon. We conclude that expiratory and inspiratory muscle weakness was not uncommon in patients with myasthenia gravis. Respiratory muscle strength improved after Tensilon. Vital capacity was a less sensitive measure of respiratory muscle strength than were respiratory mouth pressures and sniff Pdi. Diaphragmatic involvement was not detected by twitch Pdi unless the weakness was severe.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary Supplementation and Respiratory Muscle Performance in Patients with COPD

We studied the effects of oral nutritional supplementation on respiratory muscle (RM) performance in 25 ambulatory patients with severe chronic obstructive pulmonary disease (COPD). There was a relationship between body weight and anthropometric parameters of nutritional status (triceps skinfold thickness [r = 0.67; p less than 0.005], midarm muscle circumference (r = 0.53; p less than 0.005), but body weight did not correlate with daily caloric intake, serum albumin, transferrin, or blood lymphocyte count. None of these measurements of nutritional status correlated with any measure of RM strength or endurance. In a randomized observer-blinded crossover trial, patients were allocated to one of two groups. In the first eight weeks of the study, group A received nutritional supplementation, and patients in group B were control subjects. In the second eight weeks, patients in group A were control subjects, and group B received supplement. Mean daily caloric intake and body weight increased in both groups while receiving supplement (both p less than 0.05). Calories provided by the supplement were frequently substituted for normal dietary calories. Any increases in RM performance in the group receiving supplement were matched by increases (due to learning) in controls. We conclude that oral dietary supplements have no important effects on RM performance in ambulatory patients with COPD.

Dyspnea: Diagnosis and Management

Multiple physiologic and psychologic factors contribute to the sensation of acute as well as chronic dyspnea. The causes of acute dyspnea frequently can be established by a brief history, physical examination, and chest radiograph. Appropriate therapy should be directed to reversing the specific etiology leading to the acute onset of breathlessness. Chronic dyspnea is probably the most common respiratory complaint of patients seeking medical care. Both aging and deconditioning may influence the development and severity of breathlessness in healthy and disease states. Pulmonary function testing, measurement of respiratory muscle strength, and cardiopulmonary exercise testing may be required to investigate the problem of chronic dyspnea. Once the diagnosis has been made, it is useful to measure or quantify breathlessness using clinical rating methods. This baseline assessment provides objective information for evaluating response to treatment. Initial therapy for improving chronic breathlessness should be directed at the specific cause of the problem. Additional strategies for reducing dyspnea include breathing techniques, exercise training, nutritional manipulations, psychologic interventions, respiratory muscle training, respiratory muscle rest, and sedative/hypnotic medications.