Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Inspiratory Capacity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed1994

Airway dysfunction in patients with Parkinson's disease.

To investigate pulmonary function abnormalities in Parkinson's disease (PD), we obtained maximal inspiratory and expiratory flow-volume curves in 63 patients (59 under treatment) with different stages of the disease, not filtered for respiratory symptoms. PD severity was evaluated by the Unified PD Rating Scale, the Webster's scale, and Hoehn and Yahr staging. Patients with more severe PD had lower percentage forced vital capacity (FVC%), and peak inspiratory and expiratory flows. Those with fluctuations and/or dyskinesias had lower FVC% and percentage forced expiratory flow volume in 1 sec (FEV1%). There were a number of weak but significant correlations between PD scales and spirographic parameters. Thirty one patients (49.2%) had pathological flow-volume curves. The clinical profile and the duration of the disease did not influence the pattern of the curve. Physiologic evidence of upper airway obstruction was observed in 3 cases. A spirometric restrictive ventilatory defect (FEV1/FVC higher than or equal to 80%) was observed in 54 patients (85%), while generalized airway obstruction was present only in one nonsmoker. We conclude that abnormal flow-volume loop contour is a frequent finding in PD. This probably reflects involvement of the upper airway musculature, that in some patients can produce upper airway obstruction. Generalized airflow limitation is not an important characteristic of PD. By contrast, a restrictive spirometric defect, probably due to incoordinated expiratory effort or abnormally low chest wall compliance, is the main spirometric finding in these patients.

Aged↗
PubMed2005

The effects of 1 year of specific inspiratory muscle training in patients with COPD.

AIM: We assessed the long-term benefits of inspiratory muscle training (IMT) on inspiratory muscle strength, exercise capacity, the perception of dyspnea, quality of life, primary care use, and hospitalizations in patients with significant COPD. PATIENTS: Forty-two consecutive COPD patients with FEV(1) < 50% of predicted were randomized into a group that received IMT for 1 year, and a control group that received training with a very low load. RESULTS: There was a statistically significant increase in inspiratory muscle strength (at the end of the third month of training) as assessed by maximal inspiratory pressure (from 71 +/- 4.9 to 90 +/- 5.1 cm H(2)O [+/- SEM], p < 0.005) and 6-min walk distance (at the end of the third month of training; from 256 +/- 41 to 312 +/- 54 m; p < 0.005), a decrease in the mean Borg score during breathing against resistance (at the end of the ninth month of training), improvement in the health-related quality-of-life scores (at the end of the sixth month of training) in the training group but not in the control group. At the end of the training year, these changes were maintained; in addition, a decrease in primary health-care use and hospitalization days was observed. CONCLUSIONS: Our study shows that during IMT in patients with significant COPD, there is an increase in exercise capacity, improvement in quality of life, and decrease in dyspnea. Our study also provides evidence that long-term IMT can decrease the use of health services and hospitalization days.

Aged↗
PubMedDate not supplied

Exercise training in COPD: how to distinguish responders from nonresponders.

PURPOSE: Pulmonary rehabilitation programs consistently have improved exercise capacity, quality of life, and symptoms over the past decade. Although training has been shown to be an essential component of the rehabilitation program, individual patients do not always benefit to the same extent. The present study was designed to investigate which patients were achieving significant benefit of exercise training. METHODS: Forty-nine stable outpatients with moderate to severe COPD (FEV1 37 (15)%pred) were evaluated before and after 12 weeks of exercise training (3 times per week). Responders in exercise capacity were defined as having 15% increase in maximal workload and/or 25% increase in walking distance, while responders in quality of life showed an improvement of at least 10 points on the chronic respiratory disease questionnaire. With multivariate discriminant analysis, responders were distinguished from nonresponders based upon their initial characteristics. RESULTS: Thirty-two patients were responders in terms of improved exercise capacity. Ventilatory reserve (VE/MVV), inspiratory muscle strength (Plmax), and peripheral muscle strength (handgrip force and quadriceps force) were significant predictors of the training response (P < 0.05) (accuracy 80% P < 0.001). Although the explained variance was modest, patients that were clearly ventilatory limited and had normal skeletal muscle strength were not likely to benefit from exercise training in terms of exercise capacity. No physiologic variables predicted whether a patient would increase quality of life after exercise training. CONCLUSION: Patients with reduced exercise capacity who experience less ventilatory limitation to exercise and more reduced respiratory and peripheral muscle strength are more likely to improve with exercise training. Improvements in quality of life after exercise training were significant but remained unpredictable with variables included in the present trial.

Aged↗
PubMed1987

Continuous positive airway pressure effect on functional residual capacity, vital capacity and its subdivisions.

Thirty-four otherwise healthy patients having to undergo elective upper abdominal surgery were randomly assigned to two equal groups. In the treatment group, constant positive airway pressure (CPAP) with an expiratory pressure of 12 cm H2O was applied at one hour following extubation, and at daily intervals for the first five days following surgery for a continuous period of three hours. The control group received no CPAP treatment. All patients were given postoperative physiotherapy. In patients who received postoperative CPAP with an end-expiratory pressure of 12 cm H2O, marked normalization of pulmonary function was noted.

Abdomen↗
PubMed1985

The effects of inspiratory resistive training on respiratory muscle function in patients with muscular dystrophy.

The effects of inspiratory resistive training on respiratory muscle function was evaluated in 11 patients with Duchenne, limb-girdle, and facio-scapulo-humeral (FSH) type muscular dystrophy. Muscle training consisted of breathing against an inspiratory resistance for two 15-minute sessions each day while at home. Following 6 weeks of training, there were significant increases in the maximum resistance that could be tolerated for at least 5 minutes (P < 0.01) and also in the maximum duration that ventilations equal to 30%, 50%, 70%, and 90% of the maximum voluntary ventilation could be sustained (P < 0.05). In six patients who trained for an additional 6-week period, respiratory muscle endurance increased even further. The degree of improvement in respiratory muscle endurance was positively correlated with baseline vital capacity (r = 0.84, P < 0.05) and maximal inspiratory pressure (r = 0.76, P < 0.05). Spirometry, functional residual capacity, and maximal inspiratory and expiratory pressures were not affected by training. We conclude that inspiratory resistive training improves respiratory muscle endurance in muscular dystrophy patients. Improvement in respiratory muscle function may serve to delay the onset of respiratory complications in patients with muscular dystrophy.

Adolescent↗
PubMed1992

[Dyspnea sensation during resistive loading].

To examine the relationship among the sensation of dyspnea, the respiratory muscle oxygen consumption (VO2 resp), minute ventilation and occlusion pressure, seven normal volunteers were studied during incremental dead space loading induced hyperventilation with and without inspiratory resistive load. Although the sensation of dyspnea and VO2 resp at the same level of minute ventilation increased with an increase in resistance, there appeared to be a unique relationship among the sensation of dyspnea, VO2 resp and occlusion pressure, which was not affected by inspiratory resistive loading from 0 to 20 cmH2O/l/sec. These results show that the ventilatory command signal is closely related to the dyspnea sensation. We also found that during incremental dead space loading the quality of the sensation changed relatively quickly at some point, where tidal volume was maximum with each resistive loading and the breathing pattern changed. In the other experiment, the functional residual capacity (FRC) decreased during inspiratory resistive and elastic loading. Because the decreased FRC was associated with the decrease in the dyspnea sensation, it was speculated that the subject decreased his FRC through a cortical response so that the sensation of dyspnea during loading decreased.

Airway Resistance↗
PubMed2000

Targeting aerosol deposition in patients with cystic fibrosis: effects of alterations in particle size and inspiratory flow rate.

STUDY OBJECTIVE: To determine if aerosolized medications can be targeted to deposit in the smaller, peripheral airways or the larger, central airways of adult cystic fibrosis (CF) patients by varying particle size and inspiratory flow rate. DESIGN: Randomized clinical trial. SETTING: Outpatient research laboratory. PATIENTS: Nine adult patients with CF. INTERVENTIONS: Patients inhaled an aerosol comprised of 3.68+/-0.04 microm saline solution droplets (two visits) or 1.01+/- 0.2 microm saline solution droplets (two visits) for 30 s, starting from functional residual capacity and breathing at a slow or faster inspiratory flow rate. On all visits, the saline solution was admixed with the radioisotope (99m)Tc. Immediately after inhalation, a gamma camera recorded the deposition pattern of the radioaerosol in the lungs. Deposition images were analyzed in terms of the inner:outer zone (I:O) ratio, a measure of deposition in an inner zone (large, central airways) vs. an outer zone (small airways and alveoli). MEASUREMENTS AND RESULTS: For the 3.68-microm aerosol, I:O ratios averaged 2.29+/-1.45 and 2.54+/-1.48 (p>0.05), indicating that aerosol distribution within the lungs was unchanged while breathing at 12+/-2 L/min vs. 31+/-5 L/min, respectively. For the 1.01-microm aerosol, I:O ratios averaged 2.09+/-0.96 and 3.19+/-1.95 (p<0.05), indicating that deposition was predominantly in the smaller airways while breathing at 18+/-5 L/min and in the larger airways while breathing at 38+/-8 L/min, respectively. CONCLUSIONS: These results suggest that the targeted delivery of an aerosol to the smaller, peripheral airways or the larger, central airways of adult CF patients may be achieved by generating an aerosol comprised of approximately 1.0-microm particles and inspiring from functional residual capacity at approximately 18 L/min and approximately 38 L/min, respectively.

Administration, Inhalation↗
PubMed1981

Pulmonary mechanisms and work of breathing at maximal ventilation and raised air pressure.

Pulmonary ventilation (V) and the interrelationships of airflow, transpulmonary pressure, and lung volume during inspiration and expiration were studied in eight healthy subjects who performed maximal exercise (MEx; 140% VO2 max), 15-s maximal voluntary ventilation (MVV), and forced inspiratory and expiratory vital capacity (FVC) maneuvers at 1, 3, and 6 ATA. Maximal exercise ventilation and MVV amounted to 149 +/- 7 (mean +/- SE) and 193 +/- 9 l . min-1, respectively, at 1 ATA and were both reduced by approximately 37% at 3 ATA and by 50% at 6 ATA. Expiratory peak flows during MEx and MVV were equal to the maximal flows obtained during FVC at comparable lung volumes, whereas inspiratory peak flows during MEx were 20% less than the FVC flows. Despite a sixfold increase in gas density, the rate of mechanical work of breathing decreased when the pressure was raised to 6 ATA, during MEx from 8 +/- 1 to 6 +/- 1 W, and during MVV from 28 +/- 5 to 18 +/- 3 W. With increasing gas density there was a shift of lung volumes in the inspiratory direction with consequent reductions of inspiratory-to-expiratory flow ratios. We conclude that depletion of energy stores in the inspiratory muscles contributed to limiting V during MEx at raised air pressure.

Adult↗
PubMed1991

Oxygen cost of inspiratory loading: resistive vs. elastic.

We measured the O2 cost of breathing (VO2resp) against external inspiratory elastic (E) and resistive loads (R) when end-expiratory lung volume, tidal volume, breathing frequency, work rate, and pressure-time product were matched in each of six pairs of runs in six subjects. During E, peak inspiratory mouth pressure was 65.7 +/- 1.8% (SD) of the maximum at functional residual capacity. However, during resistive runs, peak inspiratory mouth pressure was 41.1 +/- 2.8% of the maximum at functional residual capacity. In 36 paired runs, where both work rate and pressure-time product were within 10%, VO2resp for E was less than for R (81 and 96 ml/min, respectively; P less than 0.01). During loaded and unloaded breathing with the same tidal volume, we measured the changes in anteroposterior diameter of the lower rib cage in five subjects. In four subjects we also recorded the electromyograms of several fixator and stabilizing muscles. During E and R, the change in anteroposterior diameter of the lower rib cage was -116 +/- 5 and -45 +/- 4% (SE), respectively, of the unloaded value (P less than 0.01), indicating greater deformation during E. Although the peak electromyographic activity was 72 +/- 16% greater during E (P less than 0.01), there was no difference between the loads for area under the electromyogram time curve (P greater than 0.05). However, the time to 50% peak activity was less during R (P less than 0.02). We conclude that, even when work rate and pressure-time product are matched, VO2resp during R is greater than that during E. This difference may be due to preferential recruitment of faster and less efficient muscle fibers.

Adult↗
PubMed1995

Benefit of selective respiratory muscle training on exercise capacity in patients with chronic congestive heart failure.

BACKGROUND: Diminished respiratory muscle strength and endurance have been demonstrated in patients with heart failure. This may contribute to exertional dyspnea and reduced exercise capacity in these patients. The purpose of this study was to investigate whether selective respiratory muscle training could alleviate dyspnea and improve exercise performance in patients with chronic congestive heart failure. METHODS AND RESULTS: Fourteen patients with chronic heart failure (left ventricular ejection fraction, 22 +/- 9%) were enrolled in a supervised respiratory muscle training program. This consisted of three weekly sessions of isocapnic hyperpnea at maximal sustainable ventilatory capacity, resistive breathing, and strength training. Maximum sustainable ventilatory capacity, maximum voluntary ventilation, maximal inspiratory and expiratory pressures, peak VO2, and the 6-minute walk test were measured before (pre) and after (post) 3 months of training. Eight patients completed the training program. Respiratory muscle endurance was improved with training, as evidenced by increases in maximal sustainable ventilatory capacity (pre, 48.6 +/- 10.7 versus post, 76.9 +/- 14.5 L/min; P < .05) and in maximal voluntary ventilation (pre, 100 +/- 36 versus post, 115 +/- 39 L/min; P < .05). Respiratory muscle strength was also increased with training as maximal inspiratory (pre, 64 +/- 31 versus post, 78 +/- 33 cm, H2O; P < .01) and expiratory (pre, 94 +/- 30 versus post, 133 +/- 53 cm H2O; P < .001) pressures rose. Submaximal and maximal exercise capacity were significantly improved with selective respiratory muscle training as the 6-minute walk (pre, 1101 +/- 351 versus post, 1421 +/- 328 ft; P < .001) and peak exercise VO2 (pre, 11.4 +/- 3.3 versus post, 13.3 +/- 2.7 mL.kg-1.min-1; P < .05) both significantly increased. Dyspnea during activities of daily living was subjectively improved in the majority of trained patients. Dyspnea quantified by the Borg scale was significantly reduced during progressive isocapnic hypernea but not during bicycle exercise. No statistically significant improvement in maximal sustainable ventilatory capacity, maximum voluntary ventilation, maximal inspiratory or expiratory mouth pressures, 6-minute walk, or peak VO2 was observed in the 6 patients who did not complete the training program. CONCLUSIONS: Selective respiratory muscle training improves respiratory muscle endurance and strength, with an enhancement of submaximal and maximal exercise capacity in patients with heart failure. Dyspnea during activities of daily living was subjectively improved in the majority of trained patients.

Adult↗
PubMed1993

Detection of tracheal stenosis by frequency analysis of tracheal sounds.

To develop a simple noninvasive method for detecting tracheal stenosis, tracheal sounds were analyzed using fast-Fourier transform. The subjects were all female and included 5 normal volunteers and 13 patients with tracheal stenosis mostly secondary to thyroid cancer (11 extrathoracic and 2 intrathoracic lesions). Tracheal sounds were recorded during spontaneous breathing and were digitized with an analog-to-digital converter. Pulmonary functions, including forced expiratory volume in 1 s (FEV1) expressed as percentage of vital capacity, peak expiratory flow rate (PEFR), the ratio of FEV1 to PEFR (Empey's index), and the ratio of expiratory to inspiratory flow rates at 50% vital capacity, were measured. A computed tomography scan was used to obtain the tracheal minimum cross-sectional area. Whereas PEFR demonstrated a weak correlation with the stenotic area, FEV1%, Empey's index, and the ratio of expiratory to inspiratory flow rates at 50% vital capacity did not. The power of the fast-Fourier transform spectrum of normal tracheal sounds decreased as the frequency increased up to 500 Hz. A small spectral peak was observed at approximately 1 kHz. Patients with significant tracheal stenosis demonstrated an increase in the peak spectral power at approximately 1 kHz and in the mean spectral power from 600 to 1,300 Hz in their tracheal sounds. In patients with extrathoracic lesions, the peak and mean spectral powers correlated well with the area of the stenosis as defined by computed tomography scan. In patients with intrathoracic lesions, abnormalities in the pulmonary functions as well as tracheal sound spectra appeared more evident despite milder stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1999

Discharge properties and recruitment of human diaphragmatic motor units during voluntary inspiratory tasks.

1. The behaviour of inspiratory motoneurones is poorly understood in humans and even for limb muscles there are few studies of motoneurone behaviour under concentric conditions. The current study assessed the discharge properties of the human phrenic motoneurones during a range of non-isometric voluntary contractions. 2. We recorded activity from 60 motor units in the costal diaphragm of four subjects using an intramuscular electrode while subjects performed a set of voluntary inspiratory contractions. These included a range of inspiratory efforts above and below the usual tidal range: breaths of different sizes (5-40 % vital capacity, VC) at a constant inspiratory flow (5 % VC s-1) and breaths of a constant size (20 % VC) at different inspiratory flows (2.5-20 % VC s-1). 3. For all the voluntary tasks, motor units were recruited throughout inspiration. For the various tasks, half-way through inspiration, 61-87 % of the sampled motor units had been recruited. 4. When the inspiratory task was deliberately altered, most single motor units began their discharge at a particular volume even when the rate of contraction had altered. 5. The initial firing frequency (median, 6.5 Hz) was consistent for tasks with a constant flow regardless of the size of the breath. However, for breaths of a constant size the initial firing frequencies increased as the inspiratory flow increased (range across tasks, 4.8-9.3 Hz). The 'final' firing frequency at the end of inspiration increased significantly above the initial frequency for each task (by 0.8-5.2 Hz) and was higher for those tasks with higher final lung volumes and higher inspiratory flows (range across tasks, 7.8-11.0 Hz). 6. There was no correlation within a task between the time of recruitment and the initial or final firing frequency for each motor unit. However, for each inspiratory task, initial and final firing frequencies were positively correlated. 7. Because the discharge of three to four units could be recorded simultaneously in a range of tasks, a quantitative 'shuffle' index was developed to describe changes in their recruitment order. Recruitment order was invariant in the task with the slowest inspiratory flow, but varied slightly, but significantly, in tasks with higher inspiratory flows. 8. The discharge rates of single motor units were compared for targeted voluntary breaths and non-targeted involuntary breaths which were matched for size. There were no significant differences in the initial or final firing frequencies, but recruitment order was not always the same in the two types of breath.

Adult↗
PubMed1979

Lung expansion, tidal exchange, and formation of the functional residual capacity during resuscitation of asphyxiated neonates.

Ventilatory exchange and endotracheal and esophageal pressures were measured during resuscitation of asphyxiated neonates born by cesarean section. In contrast to spontaneously breathing, vaginally born babies, an opening pressure had to be exceeded before lung expansion occurred. Subsequently there was usually a gradual increase in gaseous exchange over the first few lung inflations. A further rise in lung compliance occurred with the baby's inspiratory efforts. The functional residual capacity was formed with or without active inspiratory efforts by the baby, although gaseous retention occurred more rapidly as a result of the infant's inspiration.

Asphyxia Neonatorum↗
PubMed2001

Relative contribution of resting haemodynamic profile and lung function to exercise tolerance in male patients with chronic heart failure.

OBJECTIVE: To clarify the relative contribution of resting haemodynamic profile and pulmonary function to exercise capacity in patients with heart failure. SETTING: Cardiology department and cardiac rehabilitation unit in a tertiary centre. DESIGN: 161 male patients (mean (SD) age 59 (9) years) with heart failure (New York Heart Association class II-IV, left ventricular ejection fraction 23 (7)%) underwent spirometry, alveolar capillary diffusing capacity (DLCO), and mouth inspiratory and expiratory pressures (MIP, MEP, respectively, in 100 patients). Right heart catheterisation and a symptom limited cardiopulmonary exercise test were performed in 137 patients within 3-4 days. RESULTS: Mean peak exercise oxygen consumption (VO(2)) was 13 (3.9) ml/kg/min. Among resting haemodynamic variables only cardiac index showed a significant correlation with peak VO(2). There were no differences in haemodynamic variables between patients with peak VO(2) </= or > 14 ml/kg/min. There was a moderate correlation (p < 0.05) between several pulmonary function variables and peak VO(2). Forced vital capacity (3.5 (0.9) v 3.2 (0.8) l, p < 0.05) and DLCO (21.6 (6.9) v 17.7 (5.5) ml/mm Hg/min, p < 0.05) were higher in patients with peak VO(2) > 14 ml/kg/min than in those with peak VO(2) </= 14 ml/kg/min. Using a stepwise regression analysis, the respiratory and haemodynamic variables which correlated significantly with peak VO(2) were DLCO, MEP, and cardiac index, with an overall R value of 0.63. CONCLUSIONS: The data confirm previous studies showing a poor correlation between resting indices of cardiac function and exercise capacity in heart failure. However, several pulmonary function variables were related to peak exercise VO(2). In particular, lung diffusing capacity and respiratory muscle function seem to affect exercise tolerance during heart failure.

Adult↗
PubMed2006

Inspiratory muscle training in patients with heart failure and inspiratory muscle weakness: a randomized trial.

OBJECTIVES: This study sought to evaluate the effects of inspiratory muscle training in inspiratory muscle strength, as well as in functional capacity, ventilatory responses to exercise, recovery oxygen uptake kinetics, and quality of life in patients with chronic heart failure (CHF) and inspiratory muscle weakness. BACKGROUND: Patients with CHF may have reduced strength and endurance in inspiratory muscles, which may contribute to exercise intolerance and is associated with a poor prognosis. METHODS: Thirty-two patients with CHF and weakness of inspiratory muscles (maximal inspiratory pressure [Pi(max)] <70% of predicted) were randomly assigned to a 12-week program of inspiratory muscle training (IMT, 16 patients) or to a placebo-inspiratory muscle training (P-IMT, 16 patients). The following measures were obtained before and after the program: Pi(max) at rest and 10 min after maximal exercise; peak oxygen uptake, circulatory power, ventilatory oscillations, and oxygen kinetics during early recovery (VO2/t-slope); 6-min walk test; and quality of life scores. RESULTS: The IMT resulted in a 115% increment Pi(max), 17% increase in peak oxygen uptake, and 19% increase in the 6-min walk distance. Likewise, circulatory power increased and ventilatory oscillations were reduced. The VO2/t-slope was improved during the recovery period, and quality of life scores improved. CONCLUSIONS: In patients with CHF and inspiratory muscle weakness, IMT results in marked improvement in inspiratory muscle strength, as well as improvement in functional capacity, ventilatory response to exercise, recovery oxygen uptake kinetics, and quality of life.

Breathing Exercises↗
PubMed1993

Pulmonary complications of asbestos exposure.

Except for benign pleural effusion, asbestos-related pulmonary complications, including asbestosis, malignant mesothelioma and bronchogenic carcinoma, usually occur more than 20 years after exposure. Pleural plaques and pleural thickening serve as markers for asbestos exposure, but they are not associated with an increased risk of malignancy. Clinical criteria for the diagnosis of asbestosis include a reliable history of asbestos exposure, an appropriate interval between exposure and disease detection, radiographic evidence of pulmonary fibrosis, decreased vital capacity and diffusing capacity, and bilateral posterior inspiratory crackles. A lung biopsy is indicated only to rule out other causes of interstitial lung disease. A history of dyspnea, pleuritic chest pain, fatigue, weight loss and pleural effusion in a former asbestos worker is suggestive of mesothelioma. Cigarette smoking greatly increases the risk of lung cancer in asbestos workers.

Asbestos↗
PubMed2001

Relevance of dyspnoea and respiratory function measurements in monitoring of asthma: a factor analysis.

Previous studies in patients with stable chronic obstructive pulmonary disease have demonstrated that objective measures (lung volumes and respiratory muscle force) and clinical or subjective measures (symptoms of breathlessness and exercise tolerance) are quantities that independently characterize the conditions of these patients. Such an evaluation has not been previously applied in patients with stable bronchial asthma. Sixty-nine patients with stable chronic asthma underwent evaluation of static (functional residual capacity, FRC) and dynamic [forced expiratory volume in 1 sec (FEV1) and forced vital capacity, FVC] lung volumes; respiratory muscle strength (RMS), by measuring maximal inspiratory and expiratory pressures, and exercise capacity by means of the 6-min walking distance (6MWD). Chronic exertional dyspnoea was assessed by the Baseline Dyspnoea Index (BDI) focal score and by the Medical Research Council (MRC) scale. Statistical evaluation was performed by applying factor analysis. Three factors accounted for 78% of the total variance in the data: FEV1, FVC loaded on a factor I; RMS, FRC and 6MWD loaded on a factor II; dyspnoea ratings loaded on a factor III. Post-hoc analysis by randomly dividing the patients into two subgroups gave the same results. In asthmatic patients, airway obstruction appeared as an independent dimension or factor. Dyspnoea independently characterized the condition of asthma. Submaximal exercise tolerance could not be associated with the symptom of breathlessness. Evidence of independent factors support the validity of routine, multi-factorial assessment and the primary goal of treatment to alleviate symptoms and improve functional capacity in stable asthmatics.

Adult↗
PubMed1996

Impaired reflex responses to airway occlusion in the inspiratory muscles of asthmatic subjects.

BACKGROUND: Asthmatic subjects have an impaired capacity to activate the diaphragm during attempted maximal inspiratory efforts. Limb muscles require reflex facilitation to achieve maximal force. The reflex responses of inspiratory muscles to airway occlusion in asthmatic subjects were measured and compared with those in non-asthmatic control subjects. METHODS: Nine healthy asthmatic subjects breathed at a constant inspiratory flow through a low resistance valve. Random inspirations were transiently occluded for 250 ms. Surface electromyographic activity (EMG) was recorded over the scalene muscles, parasternal intercostal muscles, and the lateral chest wall overlying the diaphragm. The asthmatic subjects were studied with and without bronchoconstriction. Responses were compared with data from a matched group of 12 control subjects. RESULTS: Compared with the reflex responses to airway occlusion in control subjects, the duration of the initial short latency inhibition of inspiratory muscles was prolonged by 50% in asthmatic subjects and the size of the subsequent excitation was reduced by 30%. Bronchoconstriction reduced the time to the peak of the excitatory response in asthmatic subjects, although the values remained longer than in the control subjects. CONCLUSIONS: This study reveals impaired reflex excitation of inspiratory motoneurones in asthmatic subjects which could contribute to the reduced ability of these subjects to drive the diaphragm during maximal volitional efforts.

Adolescent↗