[The FEV1/VC ratio to define bronchial obstruction: Should we use a fixed ratio or the lower limit of normal?] / La définition de l'obstruction bronchique par le rapport VEMS/CV : seuil fixe ou limite inférieure de la normale ?

INTRODUCTION: While the screening of chronic obstructive lung diseases (COPD, asthma, etc.) constitutes a major public health issue in France and worldwide, simple spirometry appears currently as the key to meeting the challenge. Since description of the forced expiratory maneuver by Robert Tiffeneau in 1947, it has been admitted that the FEV1/VC ratio permits diagnosis obstructive pulmonary diseases. However, the diagnostic criteria for this ratio remain uncertain. The long-lasting debate between advocates of a 0.7 "fixed ratio" (FR) of 0.7 and advocates of the "lower limit of normal" (LLN) remains relevant. STATE OF THE ARTS: In this general review, we describe the respective advantages of the FR and LLN criteria according to the most recently published studies, and characterize the conditions associated with discrepancies between these criteria. PERSPECTIVES AND CONCLUSIONS: FR and LLN appear not to share similar diagnosis values and the use of both criteria facilitates proposal of an up-to-date interpretation and diagnosis strategy in the context of first-line spirometry, particularly for patients with FEV1/VC ratio in the "grey zone".

Feasibility of a nasal breathing training during pulmonary rehabilitation. A pilot randomized controlled study.

Hyperventilation syndrome (HVS) is a common source of dyspnea and disability. While pulmonary rehabilitation (PR) including breathing exercises is indicated, randomized controlled trial are warranted to recommend one type of breathing exercise than another. We aimed to compare during PR, the effect of 5 sessions of nasal ventilation exercise (NV+PR) versus voluntary hypoventilation (vHV+PR) on exercise dyspnea (primary outcome) and capacity and health-related quality of life in patients. In this open label randomized controlled trial, 19 HVS patients (age=48.3 ± 15.2 y.o, female/male=18/1, Nijmegen score=33 ± 7.7) were randomized in a NV+PR (n = 9) or vHV+PR (n = 10) group. Modified Medical Research Council (mMRC) dyspnea, 6-minute walking distance (6MWD) with nasal/oral ventilation were assessed before and after 3 months of PR, and questionnaires (Nijmegen, VQ-11). There was a significant effect of PR of but no significant difference between groups in the improvements of dyspnea@max exercise (time effect (T): p < 0.01; group (G): p = 0.63; group*time interaction (G*T): p = 0.49), mMRC dyspnea (T: p < 0.01; G: p = 0.45; G*T: p = 0.62), 6MWD (T: p < 0.05; G: p = 0.36; G*T: p = 0.31), VQ-11 (T: p < 0.001; G: p = 0.16; G*T: p = 0.09) and plasma HCO3- (T: p < 0.05; G: p = 0.93; G*T; p = 0.36), Yet, Nijmegen score (T: p < 0.01; G: p = 0.32; G*T: p < 0.05) improvement was larger in NV+PR group. The exercise oronasal breathing shift during the 6MWT was significantly delayed in all patients (T: p < 0.05; G: p = 0.30; G*T: p = 0.32) and positively correlated with plasma HCO3-(r = 0.42; p < 0.05). Nasal exercise was not superior versus voluntary hypoventilation during PR in HVS patients. Yet, nasal exercise appeared feasible, leading to acquisition of a nasal breathing pattern during walking, improvement of PR outcomes and ventilatory alkalosis. The link between nasal breathing and hyperventilation is discussed in the light of the nasal ventilation rhythm in the limbic system and its role on the limbic emotional and ventilatory functions.

Impact of a telerehabilitation programme combined with continuous positive airway pressure on symptoms and cardiometabolic risk factors in obstructive sleep apnea patients.

Background: Obstructive sleep apnea syndrome is a common sleep-breathing disorder associated with adverse health outcomes including excessive daytime sleepiness, impaired quality of life and is well-established as a cardiovascular risk factor. Continuous positive airway pressure is the reference treatment, but its cardiovascular and metabolic benefits are still debated. Combined interventions aiming at improving patient's lifestyle behaviours are recommended in guidelines management of obstructive sleep apnea syndrome but adherence decreases over time and access to rehabilitation programmes is limited. Telerehabilitation is a promising approach to address these issues, but data are scarce on obstructive sleep apnea syndrome. Methods: The aim of this study is to assess the potential benefits of a telerehabilitation programme implemented at continuous positive airway pressure initiation, compared to continuous positive airway pressure alone and usual care, on symptoms and cardiometabolic risk factors of obstructive sleep apnea syndrome. This study is a 6-months multicentre randomized, parallel controlled trial during which 180 obese patients with severe obstructive sleep apnea syndrome will be included. We will use a sequential hierarchical criterion for major endpoints including sleepiness, quality of life, nocturnal systolic blood pressure and inflammation biological parameters. Discussion: m-Rehab obstructive sleep apnea syndrome is the first multicentre randomized controlled trial to examine the effectiveness of a telerehabilitation lifestyle programme in obstructive sleep apnea syndrome. We hypothesize that a telerehabilitation lifestyle intervention associated with continuous positive airway pressure for 6 months will be more efficient than continuous positive airway pressure alone on symptoms, quality of life and cardiometabolic risk profile. Main secondary outcomes include continuous positive airway pressure adherence, usability and satisfaction with the telerehabilitation platform and medico-economic evaluation. Trial registration: Clinicaltrials.gov Identifier: NCT05049928. Registration data: 20 September 2021.

[Respiratory telerehabilitation in cases of COPD]. / Mise au point sur la téléréadaptation respiratoire dans la BPCO.

Telerehabilitation brings together a set of rehabilitation practices applied remotely by means of information and communication technologies. Even though it has been taking on increasing importance in many health fields over 10 years, telerehabilitation had yet to find its place in pulmonary rehabilitation before 2020, when the pandemic situation impelled numerous teams to put it to work. Pilot studies on respiratory diseases, primarily COPD, along with recent data from randomized or non-randomized studies, have enhanced our understanding of "remote" practice. In this review of the literature, we will show that pulmonary telerehabilitation is feasible, safe and likely to yield short-term (and possibly longer term) effects generally similar to those achieved in the pulmonary rehabilitation programs of specialized centers, especially as regards some indicators of exercise tolerance, dyspnea or patient quality of life. However, the number of studies and patients included in these programs remains too limited in terms of modalities, duration, long-term effects, or adaptations in case of exacerbation to be the subject of recommendations. The potential of respiratory telerehabilitation justifies continuing clinical trials and experiments, which need to be coordinated with the interventions characterizing a conventional program.

Skeletal muscle effects of electrostimulation after COPD exacerbation: a pilot study.

Muscle dysfunction is a major problem in chronic obstructive pulmonary disease (COPD), particularly after exacerbations. We thus asked whether neuromuscular electrostimulation (NMES) might be directly useful following an acute exacerbation and if such a therapy decreases muscular oxidative stress and/or alters muscle fibre distribution. A pilot randomised controlled study of NMES lasting 6 weeks was carried out in 15 in-patients (n=9 NMES; n=6 sham) following a COPD exacerbation. Stimulation was delivered to the quadriceps and hamstring muscles (35 Hz). Primary outcomes were quadriceps force and muscle oxidative stress. At the end of the study, quadriceps force improvement was statistically different between groups (p=0.02), with a significant increase only in the NMES group (median (interquartile range) 10 (4.7-11.5) kg; p=0.01). Changes in the 6-min walking distance were statistically different between groups (p=0.008), with a significant increase in the NMES group (165 (125-203) m; p=0.003). NMES did not lead to higher muscle oxidative stress, as indicated by the decrease in total protein carbonylation (p=0.02) and myosin heavy chain carbonylation (p=0.01) levels. Finally, we observed a significant increase in type I fibre proportion in the NMES group. Our study shows that following COPD exacerbation, NMES is effective in counteracting muscle dysfunction and decreases muscle oxidative stress.

Carnosine, oxidative and carbonyl stress, antioxidants, and muscle fiber characteristics of quadriceps muscle of patients with COPD.

Oxidative/carbonyl stress is elevated in lower-limb muscles of patients with chronic obstructive pulmonary disease (COPD). Carnosine is a skeletal muscle antioxidant particularly present in fast-twitch fibers. The aims of the present study were to compare muscle carnosine, oxidative/carbonyl stress, antioxidants, and fiber characteristics between patients with COPD and healthy controls (HCs) and between patients after stratification for airflow limitation (mild/moderate vs. severe/very severe), as well as to investigate correlates of carnosine in patients with COPD. A vastus lateralis muscle biopsy was obtained from 40 patients with stable COPD and 20 age- and sex-matched HCs. Carnosine, oxidative/carbonyl stress, antioxidants, fiber characteristics, quadriceps strength and endurance (QE), V̇o2peak (incremental cycle test), and physical activity (PA) were determined. Patients with COPD had a similar carnosine concentration [4.16 mmol/kg wet weight (WW; SD = 1.93)] to HCs [4.64 mmol/kg WW (SD = 1.71)] and significantly higher percentage of fast-twitch fibers and lower QE, V̇o2peak, and PA versus HCs. Patients with severe/very severe COPD had a 31% lower carnosine concentration [3.24 mmol/kg WW (SD = 1.79); n = 15] versus patients with mild/moderate COPD [4.71 mmol/kg WW (SD = 1.83); n = 25; P = 0.02] and significantly lower V̇o2peak and PA versus patients with mild/moderate COPD. Carnosine correlated significantly with QE (rs = 0.427), V̇o2peak (rs = 0.334), PA (rs = 0.379), and lung function parameters in patients with COPD. In conclusion, despite having the highest proportion of fast-twitch fibers, patients with severe/very severe COPD displayed a 31% lower muscle carnosine concentration compared with patients with mild/moderate COPD. As no other markers of oxidative/carbonyl stress or antioxidants were affected, the observed carnosine deficiency is thought to be a possible first sign of muscle redox balance abnormalities.NEW & NOTEWORTHY Carnosine, particularly present in fast-twitch fibers, was investigated in the quadriceps of patients with chronic obstructive pulmonary disease (COPD). Carnosine concentration was similar between patients with COPD and healthy controls but was 31% lower in patients with severe/very severe COPD, despite their high proportion of fast-twitch fibers, versus patients with mild/moderate COPD. As no other markers of oxidative/carbonyl stress or antioxidants were affected, the observed carnosine deficiency is thought to be a possible first sign of muscle redox balance abnormalities.

[Practical methods for controlled diaphragmatic breathing in 2009: proposals for a consensus]. / Modalités pratiques de réalisation de la ventilation dirigée abdomino-diaphragmatique en 2009: propositions pour un consensus.

BACKGROUND: This work has been completed at the request of the French Language Society of Pneumology. It is the result of collaboration between the 'Muscles and Respiration Group' and the 'Working Group in Physiotherapy', arriving at a consensus on diaphragmatic breathing. RESULTS: From the literature followed by a formalized consensus methodology, the authors specify the terminology and define the appropriate methods of this technique that should be used. CONCLUSION: Analysis of the literature to date does not allow assessment of the efficacy of this technique. The precise definition of the methods of diaphragmatic breathing as proposed in the present study will be used as a basis for forthcoming studies on this technique.

An innovative maintenance follow-up program after a first inpatient pulmonary rehabilitation.

Although the benefits of pulmonary rehabilitation (PR) have been demonstrated in patients with COPD, most studies suggest that short-term programs are insufficient to maintain the benefits beyond a post-discharge period of 6 months to 1 year. We were interested to evaluate the effects of an innovative maintenance intervention compared with a usual after-care. Forty moderate to severe COPD patients, who had just completed their first inpatient PR, were consecutively included in either a maintenance group (MG) or a standard after-care group. The maintenance program was coordinated within a health-care network including self-help associations, and offered weekly activities. We measured the 6-min walk distance (6MWD), the quality of life using the St George Respiratory Questionnaire (SGRQ), the dyspnea, the maximal workload and the health-care utilization. Data were collected at respiratory clinic admission and discharge, and at 6- and 12-month visits after the PR. After 12 months, we found statistically and clinically significant differences in favor of the MG in 6MWD (74 m; p < or = 0.01) and in the three domains of SGRQ: symptom (19%; p < or = 0.01), activity (27%; p < or = 0.01) and impact (32%; p < or = 0.01). The results showed no difference between groups in dyspnea and maximal workload. We also found that the number of days spent in hospital for respiratory disorders was significantly lower in the MG after 12 months (p < or = 0.03). The multidisciplinary management of COPD patients in the post-rehabilitation period within a health-care network including self-help associations seems to be an effective strategy for maintaining, and even improving, the benefits of a first initial structured program.

[Which definition to use when defining airflow obstruction?]. / Quelle définition faut-il choisir pour le déficit ventilatoire obstructif?

INTRODUCTION: There is no clear consensus as to what constitutes an obstructive ventilatory defect (OVD). According to the American Thoracic Society and European Respiratory Society, it is defined as being when the ratio of the forced expiratory volume (FEV1) and the slow expiratory vital capacity (VC) is below the lower limit of normal (LLN). According to the Global initiative for chronic Obstructive Lung Disease and the British Thoracic Society, it is an FEV1/forced expiratory vital capacity (FVC)<0.70 and an FEV1<80%. In addition, in daily practice, the OVD is diagnosed by a "Fixed ratio" FEV1/FVC<0.70 or

[Factors influencing pulmonary function in Tunisian women aged 45 years and more]. / Facteurs influençant les variables ventilatoires des Tunisiennes âgées de 45 ans et plus.

INTRODUCTION: The aim of this study was to analyse the factors influencing pulmonary function and inspiratory muscle strength in healthy Tunisian women aged >or=45 years and in particular to determine the effect of parity. METHODS: A medical questionnaire together with an evaluation of sporting activity score and 2 levels for schooling and socio-economic status was administered. Parity was introduced as numeric, as dichotomous (G1:or=4) and in 3 classes (C1:<2; C2:=3-4; C3: > 4). Plethysmography with measurement of airway conductance and maximal inspiratory pressure was performed. RESULTS: 108 women were included. According to the ascending multiple linear regression, and in decreasing order, the following influencing factors are noted: Age and height, parity, weight and daily activity, schooling level, and finally leisure activity, body mass index, and physical activity. With high parity, and especially in women aged >or=60 years, there was a decrease in inspiratory muscle strength and an obstructive tendency, without associated restrictive component. Parity effects are age independent. CONCLUSIONS: Factors influencing the pulmonary function of healthy Tunisian women aged >or=45 years are multiple. Lung function declines with increasing parity.

[Evaluation of pulmonary function in the elderly. Intergroupe Pneumo Gériatrie SPLF-SFGG]. / Evaluation de la fonction respiratoire chez le sujet âgé. Intergroupe Pneumo Gériatrie SPLF-SFGG.

Aging is associated with a progressive decrease in lung function. As a consequence of aging, individual's reserve is diminished, but this decrease is heterogeneous between individual subjects. Many factors are involved in the overall decline in lung function. The prevalence of asthma in the elderly is estimated between 6 and 10%. Mortality due to COPD is increasing, especially among older subjects. Older subjects are at an increased risk of developing chronic diseases such as Parkinson's disease, which can have consequences for lung function. Under-nutrition is also common in the elderly and can produce sarcopenia and skeletal muscle dysfunction. The presentation of respiratory disorders may differ in the elderly, especially because of a lack of perception of symptoms such as dyspnea. The impact of bronchodilatators or corticosteroids on respiratory function has not been studied in the elderly. Drugs usually used for the treatment of hypertension or arrhythmias, which are often observed with aging, can have pulmonary toxicity. There is no difference between functional evaluation in younger and older subjects but it is more difficult to find predicted values for older patients. Performing pulmonary function tests in older patients is often difficult because of a higher prevalence of cognitive impairment and/or poor coordination. When assessing pulmonary function in the elderly, the choice of tests will be depend on the circumstances, with the use of voluntary manoeuvres dependent on the condition of the patient.

Postoperative exercise tolerance after aortic valve replacement by small-size prosthesis: functional consequence of small-size aortic prosthesis.

OBJECTIVES: The objective of this study was to determine whether a small-size valve prosthesis contributes to exercise intolerance, as assessed by VO2 measurement during an exhaustive cycle ergometer exercise. BACKGROUND: The determinants of exercise capacity after mechanical aortic replacement are not well known. The selection of small valve sizes has, however, been described as an independent predictor of exercise intolerance as assessed by exercise duration. Maximal oxygen uptake (VO2max) is a good index of exercise tolerance. METHODS: Fourteen patients were eligible, with a mean age of 62 +/- 6 years. Before surgery, the mean left ventricular ejection fraction (LVEF) was 73 +/- 8%. Two valve types with small diameter (19 to 21 mm) were used: Medtronic Hall and St Jude Medical. A healthy sedentary control group (n = 14) paired for age, weight and size was constituted. After one year of follow-up, cardiorespiratory tests were performed. In addition, the gradients through the prostheses were determined by continuous pulse Doppler at rest and immediately after the cardiorespiratory test. RESULTS The exercise tolerance was not significantly different between the control group and patient group: VO2 peak (21.7 vs. 20.4 ml/kg/min; p = 0.42), workloads (115 vs. 93 W; p = 0.13) and ventilatory parameters were similar. The mean and peak gradients at rest and during exercise were not correlated with VO2max. CONCLUSIONS: Valve replacement by small aortic prosthesis does not seem to be a factor of exercise intolerance as assessed by VO2max in patients without LVEF dysfunction before surgery.

A standardized method for the evaluation of respiratory muscle endurance in patients with Duchenne muscular dystrophy.

The aim of the study was to develop a standardized method using controlled breathing to quantify respiratory muscle endurance in children with Duchenne muscular dystrophy (DMD) and to test its reproducibility. In 10 DMD patients, all between 10 and 14 years (mean age, 11.5 +/- 1.5 years), except for two patients of 20 and 22 years, and 10 healthy children (mean age, 12 +/- 1 years), we measured the maximal time (Tlim) that a threshold load fixed at 35% of the individual maximal inspiratory pressure (Pimax) could be tolerated. We asked the children to maintain their rest breathing pattern until exhaustion using visual feedback and an auditory signal. The mean Tlim in the DMD children was 4.45 +/- 1.45 min and values were reproducible. All healthy children were able to obtain Tlim values greater than 30 min. The respiratory muscles of DMD children are more susceptible to fatigue than those of healthy subjects. This method should be satisfactory for estimating the effect of treatment and for the specific training of respiratory muscles in DMD patients without significant learning disability.

Long-term results of neoadjuvant ifosfamide, cisplatin, and etoposide combination in locally advanced non-small-cell lung cancer.

Thirty-three patients with T3,N2,M0 or T4,N2,M0, non-small-cell lung cancer (NSCLC) took part in a phase 2 study in an attempt to evaluate the feasability of neoadjuvant chemotherapy followed by surgery and thoracic radiotherapy. Chemotherapy consisted of daily administration of the following treatment: etoposide, 100 mg/m2; cisplatin, 25 mg/m2; ifosfamide, 1.5 g/m2; and mesna, 1.8 g/m2 for 4 days. Three cycles were planned starting every 21 days. Responding patients underwent a thoracotomy in order to attempt a resection and then received a 45 Gy of thoracic radiotherapy. The results of response and resection rates have been published and the present final report deals with the long-term results. Chemotherapy induced a 55 percent partial response rate and a 15 percent complete response rate allowing a complete resection in 55 percent of the patients. Complete remission was histologically confirmed for the five complete responders. Although the median survival was short (10 months), six patients were long-term survivors (3-year survival rate: 19 percent). Survival was significantly influenced by the type of resection: patients for whom a complete resection was possible survived the longest with a median survival three times that of the other patients. Modalities of relapses differed according to the results of surgery: 8 of the 15 patients who did not undergo a complete surgical resection experienced a local relapse during the first 18 months of follow-up whereas in the complete resection group, central nervous system metastasis was the main site of relapse. We conclude that the neoadjuvants ifosfamide, cisplatin, and etoposide in patients with locally advanced NSCLC are feasible to use and allow a 19 percent 3-year survival rate. These results are the rationale of an ongoing randomized study comparing neoadjuvant chemotherapy followed by surgery and surgery alone. This study is designed to test whether neoadjuvant chemotherapy improves survival of patients with locally advanced NSCLC.

Morphological and functional recovery from diaphragm injury: an in vivo rat diaphragm injury model.

Our objective was to develop an in vivo model to study the timing and mechanisms underlying diaphragm injury and repair. Diaphragm injury was induced in anesthetized rats by the application of a 100 mM caffeine solution for a 10-min period to the right abdominal diaphragm surface. Diaphragms were removed 1, 4, 6, 12, 24, 48, 72, and 96 h and 10 days after the injury, with contractile function being assessed in strips in vitro by force-frequency curves. The extent of caffeine-induced membrane injury was indicated by the percentage of fibers with a fluorescent cytoplasm revealed by inward leakage of the procion orange dye. One hour after caffeine exposure, 32.9 +/- 3.1 (SE) % of fibers showed membrane injury that resulted in 70% loss of muscle force. Within 72-96 h, the percentage of fluorescent cells decreased to control values. Muscle force, however, was still reduced by 30%. Complete muscle strength recovery was observed 10 days after the injury. Whereas diaphragmatic fiber repair occurred within 4 days after injury induction, force recovery took up to 10 days. We suggest that the caffeine-damaged rat diaphragm is a useful model to study the timing and mechanisms of muscle injury and repair.

Determinants of the tension-time index of inspiratory muscles in children with cystic fibrosis.

Nutritional status and chronic pulmonary hyperinflation can alter respiratory muscle function in cystic fibrosis (CF). This study investigated: 1) whether inspiratory muscle function is reduced in children with stable CF in comparison with healthy controls; and 2) the mechanisms leading to inspiratory muscle weakness, which probably predispose to respiratory muscle fatigue. We determined the tension-time index of the inspiratory muscles (TTMUS) noninvasively at rest in 16 children with mild to moderate CF (mean age, 11 +/- 2 years) and 10 healthy controls (mean age, 11 +/- 2 years). The TTMUS was determined as follows: TTMUS = TI/TTOT.PI/PIMAX, where PI is the mean inspiratory pressure estimated from the measure of mouth occlusion pressure (P0.1), PIMAX is the maximal inspiratory pressure, and TI/TOT is the duty cycle. The results showed similar nutritional status in both groups, as well as mild to moderate airway obstruction, hyperinflation, and trapped gas in the CF group. In this group only, a significant inverse relationship was found between TI/TOT and PI/PIMAX[TITTOT = 0.482 - (0.388PI/PIMAX), r = -0.53; p < 0.05]. These patients also had greater TTMUS (TTMUS = 0.087 +/- 0.030 in CF vs. 0.056 +/- 0.014 in controls, P < 0.01) that increased with decreasing lean body mass (r = -0.70, P < 0.005), with increasing percent predicted functional residual capacity (r = 0.70, P < 0.05), and increasing volumes of trapped gas (r = 0.77, P < 0.01). The multiple linear regression analysis for these factors was significant (R2 = 0.84, P < 0.01); however, the partial regression coefficient was significant only for lean body mass (r2 = 0.60, P < 0.05). Therefore, muscle mass appeared as the strongest determinant of TTMUS in CF. This study used a noninvasive method to assess the inspiratory muscle performance in children with CF. The results suggest impairment in inspiratory muscle function in these children despite good nutritional status and only mild to moderate alteration in pulmonary function tests. In addition, we were able to investigate some of the determinants of inspiratory muscle weakness, namely, muscle mass, hyperinflation, and trapped gas, and found that muscle mass played a predominant role.

Tension-time index of inspiratory muscles in COPD patients: role of airway obstruction.

Inspiratory muscle function has been shown to be related to general muscle weakness, weight loss, blood gas tensions, airway obstruction and hyperinflation. The aim of this study was to define (1) the factor that is the main determinant of the tension-time index of the inspiratory muscles (TTmus), and which this increases the risk of inspiratory muscle fatigue; and (2) whether a breathing strategy is adopted to avoid inspiratory muscle fatigue. Twenty-seven normal volunteers and 35 stable COPD outpatients (FEV1% predicted, range: 21-89%; and FRC/TLC, range: 49-77%) were studied. The TTmus was determined as follows: TTmus = PI/PImax.TI/Ttot, where Pi is the mean inspiratory pressure calculated from the mouth occlusion pressure (P0.1), PImax is the maximal inspiratory pressure, TI is the inspiratory time, and Ttot is the total time of the breathing cycle. COPD patients showed significantly lower PImax and higher P0.1, PI, PI/PImax, and TTmus than normal subjects. No patient had a TTmus value higher than the inspiratory muscle fatigue threshold of 0.33. The FEV1 was significantly correlated with TTmus and all its components in the patients. The FRC/TLC was also correlated with all components except PI. Body weight was only correlated with PImax. In a forward and backward stepwise regression analysis, FEV1 appeared to be the only significant factor explaining the variance of log (PI/PImax) and log (TTmus), whereas FRC/TLC was the principal determinant of PImax. In COPD patients, a non-linear relationship was found between TI and P0.1. A negative linear relationship was found between TI/Ttot and PI/PImax. In conclusion, although hyperinflation predominantly affected inspiratory muscle strength in a group of stable COPD patients with a wide range of severity, airway obstruction was the principal factor determining the magnitude of TTmus. In addition, in order to remain below the inspiratory muscle fatigue threshold, as the severity of airway obstruction increased, patients adopted a breathing strategy characterized by decreased TI/Ttot as inspiratory pressure demand increased.

Skeletal muscle abnormalities in patients with COPD: contribution to exercise intolerance.

Exercise intolerance in COPD patients appears to be in part because of skeletal muscle dysfunction. Studies using biopsy techniques and magnetic resonance spectroscopy have demonstrated changes in enzyme activities and metabolism that indicate reduced oxidative capacity in the peripheral muscles of these patients. Regarding the respiratory muscles, the biochemical characteristics have been studied in only a few works and the results seem to depend on the specific muscle group studied. Several factors, such as hypoxemia, nutritional status, pharmacological treatment, and deconditioning, may be responsible for these skeletal muscle abnormalities. This brief review describes the changes in peripheral and respiratory muscles in COPD patients based on data from the literature. The causes of these muscle abnormalities, their contribution to exercise intolerance, and the effects of training are then discussed. We conclude with suggested directions for future investigation using contemporary noninvasive technologies.

Wingate test performance in children with asthma: aerobic or anaerobic limitation?

To investigate the anaerobic capacity in children with bronchial asthma, eight male children with atopic asthma (age: 12 +/- 1.7 yr) and seven healthy control subjects (age: 12 +/- 1 yr) performed a 30-s all-out exercise test: the Wingate anaerobic test (WanT). Post-exercise plasma epinephrine (E), norepinephrine (NE), venous blood lactate (La), and blood pH levels were determined. Peak power (Ppeak), mean power (Pm), and total energy expenditure (Wtot) during the WanT were assessed. The relative importance of aerobic (WO2) and anaerobic (Wana) energy release during the WanT was also evaluated. In comparison with control subjects, the children with asthma exhibited lower Ppeak (W.kg-1): 6 +/- 1.14 vs 7.3 +/- 0.5, P < 0.05; lower Pm (W.kg-1): 4.7 +/- 0.8 vs 5.9 +/- 0.5, P < 0.05; and lower Wtot (Jg-1): 140.3 +/- 25 vs 176.9 +/- 19, P < 0.05. The relative contribution of WO2 (26%) and Wana (74%) to the Wtot was identical in both groups. Blood lactate and pH kinetics revealed significantly lower La values and less acidosis in the asthmatic group (P < 0.001). Lastly, E (pg.ml-1) concentrations were lower in the asthmatic group: 274.96 +/- 84.58 vs 901.28 +/- 604.76, P < 0.05. These results suggest a reduced anaerobic capacity in children with asthma. A diminished adrenergic response to exhausting exercise, leading to a decreased anaerobic glycolysis, could partly account for this phenomenon.

Reliability of a new device to assess the oxygen consumption of human respiratory muscles.

PURPOSE: This study tests the reliability of a new device for assessing the oxygen consumption of the respiratory muscles (VO2 resp.). METHODS: Fourteen healthy male volunteers participated in the study. The device consists of an expandable external ventilatory dead space created with pieces of plastic tubing and a spirometer filled with 100% oxygen. It also incorporates a carbon dioxide absorber. Total VO2 (VO2 tot.) was recorded from the spirometric closed circuit and ventilation (V(E)), from the spirometer tracing. For each subject the test procedure was carried out in duplicate (T1 and T2) after an overnight fast. The dead space was increased at a constant rate of 260 mL every 90 s, and VO2 tot. and V(E) increased progressively. Because log VO2 tot. was linearly related to V(E), we calculated the slope value (log VO2-V(E)) and the Y-intercept (VE = 0) of the semilog regression representing, respectively, VO2 resp. and metabolic VO2 (VO2 met.). RESULTS: When compared with values in the literature, these values did not differ from those recorded in subjects of a similar age group. The VO2 resp. and VO2 met. calculated in T1 and T2 were not different (VO2 resp. = 0.0066 +/- 0.0005 for T1 vs 0.0067 +/- 0.0005 log mL x min(-1)/L x min(-1) for T2 and VO2 met. = 269.3 +/- 28.6 for T1 vs 281.9 +/- 24.1 mL x min(-1) for T2). The coefficients of variation were: 25% at T1 and 23% at T2 for VO2 resp. and 34% at T1 and 29% at T2 for VO2 met. Moreover, significant correlations (r = 0.96, P < 0.001 for VO2 resp., r = 0.95, P < 0.001 for VO2 met.), high coefficients of determination (r2 = 0.92 for VO2 resp., r2 = 0.90 for VO2 met.) and negligible SEE (0.0005 for VO2 resp., 0.2 mL x min(-1) for VO2 met.) were found between the two tests. When we plotted the mean values of VO2 resp. and VO2 met. measured at T1 and T2 against their respective differences, more than 95% of the slight differences ranged between the limits defined by mean value +/- 2 SD, reflecting the small discrepancy between duplicate measurements. CONCLUSION: The results confirm that the test performed with this device is useful and reliable for assessing the VO2 resp. in healthy subjects.