Respiratory Muscles and Dyspnea

[Evaluation of the Functional Reserve and Exercise Tolerance in Patients with CHF in Clinical Trials (Consent Document of the Editorial board of the Journal of Cardiology, the Board of the Society of Specialists in Heart Failure (SSHF) and Working Group "Non-drug treatment methods" of SSHF)]

Assessing the functional capacity and exercise tolerance is an important and widely used research tool in patients with heart failure. It is used not only in cardiac rehabilitation and physical therapy, but also for inclusion criteria and outcome measures in studies of drug interventions. This document outlines the scope, guidelines for the implementation and interpretation, and limitations of the methods for assessing the functional capacity and exercise tolerance in clinical trials in patients with heart failure.

The therapeutic role of inspiratory muscle training in the management of asthma: a narrative review

Asthma is a disorder of the airways characterized by chronic airway inflammation, hyperresponsiveness, and variable recurring airway obstruction. Treatment options for asthma include pharmacological strategies, whereas nonpharmacological strategies are limited. Established pharmacological approaches to treating asthma may cause unwanted side effects and do not always afford adequate protection against asthma, possibly because of an individual's variable response to medications. A potential nonpharmacological intervention that is most available and cost effective is inspiratory muscle training (IMT), which is a technique targeted at increasing the strength and endurance of the diaphragm and accessory muscles of inspiration. Studies examining the impact of IMT on asthma have reported increases in inspiratory muscle strength and a reduction in the perception of dyspnea and medication use. However, because of the limited number of studies and discordant methods between studies more evidence is required to elucidate in individuals with asthma the efficacy of IMT on inspiratory muscle endurance, exercise capacity, asthma control, symptoms, and quality of life as well as in adolescents with differing severities of asthma. Large randomized controlled trials would be a significant step forward in clarifying the effectiveness of IMT in individuals with asthma. Although IMT may have favorable effects on inspiratory muscle strength, dyspnea, and medication use, the current evidence that IMT is an effective treatment for asthma is inconclusive.

Clinical effect of aerobic exercise training in chronic obstructive pulmonary disease: A retrospective study

Aerobic exercise training is a kind of pulmonary rehabilitation for lung diseases. This was a retrospective study to assess the efficacy of aerobic exercise training in chronic obstructive pulmonary disease (COPD) at a stable stage. A total of one hundred and fifty-six stable COPD patients who had accepted self-education only or self-education combined with an aerobic exercise training between January 2017 to January 2019 were reviewed retrospectively. A total of 79 patients who had received self-education combined with an aerobic exercise training schedule comprised the aerobic exercise training group (AET group) and 77 patients who had received self-education only were regarded as the education group (EDU group). The acute incidence rate in AET group was 7.6% better than that in EDU group 20.7% (P < .05). The AET group patients expressed higher levels of 6 minutes walking distance (6MWD) (P < .05) and better evaluations of both lung function (P < .05) and T lymphocyte immune response (P < .05), as well as significantly decreased chronic obstructive pulmonary disease assessment test (CAT) scores and modified British medical research council (mMRC) grades (P < .05). Patients in EDU group did not report any changes in any of these characteristics. The aerobic exercise training intervention contributed to an increasing in 6MWD and decrease in CAT scores and mMRC grades, as well as improving the T lymphocyte immune response in stable COPD patients.

Effect of respiratory muscle training in asthma: A systematic review and meta-analysis

BACKGROUND

The last systematic review about respiratory muscle training (RMT) in people with asthma was published almost 10 years ago. Since then, several works have been published.

OBJECTIVE

To review the effect of RMT in people with asthma.

METHODS

We conducted a systematic review of research included up to September 2021 in PubMed/MEDLINE, PEDro, Scopus, Web of Science, CINAHL, LILACS, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov. We included randomized controlled trials and quasi-experimental studies assessing the effect of RMT on respiratory muscle function, rescue medication, asthma-related symptoms, lung function, exercise capacity, healthcare use, health-related quality of life (HRQoL) and adverse effects in people with asthma. Risk of bias and methodological quality were assessed with the Cochrane Risk of Bias assessment tool and the PEDro scale. Meta-analysis was performed whenever possible; otherwise a qualitative approach was followed.

RESULTS

Eleven studies (270 participants) were included, 10 with only adults and were included in the meta-analysis. Inspiratory muscle training (IMT) had beneficial effects on maximal inspiratory pressure (PImax: mean difference [MD] 21.95 cmH₂O [95% confidence interval [CI] 15.05; 28.85]), with no changes in maximal expiratory pressure (MD 14.97 cmH₂O [95%CI -5.65; 35.59]), lung function (forced expiratory volume in 1 sec: MD 0.06 [95%CI -0.14; 0.26] L; force vital capacity: MD 0.39 [95%CI -0.24; 1.02] L) and exercise capacity (standard mean difference [SMD] 1.73 [95%CI -0.61; 4.08]). Subgroup analysis revealed that IMT load >50% PImax and duration >6 weeks were beneficial for exercise capacity. The qualitative analysis suggested that IMT may have benefits on respiratory muscle endurance, rescue medication and exertional dyspnoea, with no adverse effects.

CONCLUSIONS

This systematic review and meta-analysis showed a significant increase in PImax after IMT in adults with asthma and reinforced the relevance of the dose-response principle of training. More evidence is needed to clarify the effect of IMT in respiratory muscle endurance, rescue medication, exercise capacity, healthcare use and HRQoL.

TRIAL REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews CRD42020221939; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=221939.

Inspiratory Muscle Rehabilitation Training in Pediatrics: What Is the Evidence?

Pulmonary rehabilitation is typically used for reducing respiratory symptoms and improving fitness and quality of life for patients with chronic lung disease. However, it is rarely prescribed and may be underused in pediatric conditions. Pulmonary rehabilitation can include inspiratory muscle training that improves the strength and endurance of the respiratory muscles. The purpose of this narrative review is to summarize the current literature related to inspiratory muscle rehabilitation training (IMRT) in healthy and diseased pediatric populations. This review highlights the different methods of IMRT and their effects on respiratory musculature in children. Available literature demonstrates that IMRT can improve respiratory muscle strength and endurance, perceived dyspnea and exertion, maximum voluntary ventilation, and exercise performance in the pediatric population. These mechanistic changes help explain improvements in symptomology and clinical outcomes with IMRT and highlight our evolving understanding of the role of IMRT in pediatric patients. There remains considerable heterogeneity in the literature related to the type of training utilized, training protocols, duration of the training, use of control versus placebo, and reported outcome measures. There is a need to test and refine different IMRT protocols, conduct larger randomized controlled trials, and include patient-centered clinical outcomes to help improve the evidence base and support the use of IMRT in patient care.

Physiological Predictors of Morbidity and Mortality in COPD: The Relative Importance of Reduced Inspiratory Capacity and Inspiratory Muscle Strength

Low resting inspiratory capacity (IC) and low maximal inspiratory pressure (MIP) have previously been linked to exertional dyspnea, exercise limitation and poor survival in chronic obstructive pulmonary disease (COPD). The interaction and relative contributions of these two related variables to important clinical outcomes are unknown. The objective of the current study was to examine the interaction between resting IC and MIP (both % predicted), exertional dyspnea, exercise capacity and long-term survival in patients with COPD. Two hundred and eighty-five patients with mild to advanced COPD completed standard lung function testing and a cycle cardiopulmonary exercise test. Multiple regression determined predictors of the exertional dyspnea-ventilation slope and peak oxygen uptake (V̇O_2peak). Cox regression determined predictors of 10-year mortality. IC was associated with the dyspnea-ventilation slope (standardized β=-0.44, p<0.001), while MIP was excluded from the regression model (p=0.713). IC and MIP were included in the final model to predict V̇O_2peak. However, the standardized β was greater for IC (0.49) than MIP (0.22). After adjusting for age, sex, body mass index, cardiovascular risk, airflow obstruction and diffusing capacity, resting IC was independently associated with 10-year all-cause mortality (hazard ratio=1.25, confidence interval_5-95%=1.16-1.34, p<0.001), while MIP was excluded from the final model (all p=0.829). Low resting IC was consistently linked to heightened dyspnea intensity, low V̇O_2peak and worse survival in COPD even after accounting for airway obstruction, inspiratory muscle strength, and diffusing capacity. These results support the use of resting IC as an important physiological biomarker closely linked to key clinical outcomes in COPD.

Inspiratory muscle weakness in cardiovascular diseases: Implications for cardiac rehabilitation

Exercise limitation is a cardinal manifestation of many cardiovascular diseases (CVD) and is associated with poor prognosis. It is increasingly well understood that exercise-based cardiac rehabilitation (CR) is an intervention that portends favorable clinical outcomes, including improvements in exercise capacity. The etiology of exercise limitation in CVD is multifactorial but is typically governed by terminal sensations of pain, fatigue, and/or breathlessness. A known but perhaps underestimated complication of CVD that contributes to breathlessness and exercise intolerance in such patients is inspiratory muscle dysfunction. For example, inspiratory muscle dysfunction, which encompasses a loss in muscle mass and/or pressure generating capacity, occurs in up to ~40% of patients with chronic heart failure and is associated with breathlessness, exertional intolerance, and worse survival in this patient population. In this review, we define inspiratory muscle weakness, detail its prevalence in a range of CVDs, and discuss how inspiratory weakness impacts physiological function and clinical outcomes in patients with CVD often referred to CR. We also evaluate the available evidence addressing the effects of exercise-based CR with and without concurrent specific inspiratory muscle training (IMT) on inspiratory muscle function, general physiological function, and clinical outcomes in patients with CVD. Finally, we consider whether the assessment of global respiratory muscle function should become standard as part of the patient intake assessment for phase II CR programs, giving practical guidance on the implementation of such measures as well as IMT as part of phase II CR.

Use of Cardiopulmonary Stress Testing for Patients With Unexplained Dyspnea Post-Coronavirus Disease

Objectives

The authors used cardiopulmonary exercise testing (CPET) to define unexplained dyspnea in patients with post-acute sequelae of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection (PASC). We assessed participants for criteria to diagnose myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).

Background

Approximately 20% of patients who recover from coronavirus disease (COVID) remain symptomatic. This syndrome is named PASC. Its etiology is unclear. Dyspnea is a frequent symptom.

Methods

The authors performed CPET and symptom assessment for ME/CFS in 41 patients with PASC 8.9 ± 3.3 months after COVID. All patients had normal pulmonary function tests, chest X-ray, and chest computed tomography scans. Peak oxygen consumption (peak VO₂), slope of minute ventilation to CO₂ production (VE/VCO₂ slope), and end tidal pressure of CO₂ (PetCO₂) were measured. Ventilatory patterns were reviewed with dysfunctional breathing defined as rapid erratic breathing.

Results

Eighteen men and 23 women (average age: 45 ± 13 years) were studied. Left ventricular ejection fraction was 59% ± 9%. Peak VO₂ averaged 20.3 ± 7 mL/kg/min (77% ± 21% predicted VO₂). VE/VCO₂ slope was 30 ± 7. PetCO₂ at rest was 33.5 ± 4.5 mm Hg. Twenty-four patients (58.5%) had a peak VO₂ <80% predicted. All patients with peak VO₂ <80% had a circulatory limitation to exercise. Fifteen of 17 patients with normal peak VO₂ had ventilatory abnormalities including peak respiratory rate >55 (n = 3) or dysfunctional breathing (n = 12). For the whole cohort, 88% of patients (n = 36) had ventilatory abnormalities with dysfunctional breathing (n = 26), increased VE/VCO₂ (n = 17), and/or hypocapnia PetCO₂ <35 (n = 25). Nineteen patients (46%) met criteria for ME/CFS.

Conclusions

Circulatory impairment, abnormal ventilatory pattern, and ME/CFS are common in patients with PASC. The dysfunctional breathing, resting hypocapnia, and ME/CFS may contribute to symptoms. CPET is a valuable tool to assess these patients.

Functionally relevant threshold of inspiratory muscle strength in patients with chronic obstructive pulmonary disease

OBJECTIVES

We aimed to identify the inspiratory muscle strength thresholds below which exercise capacity is compromised in men with chronic obstructive pulmonary disease (COPD).

METHODS

We measured the maximum static inspiratory mouth pressure (PImax) and the percentage of predicted values (%PImax) in 113 patients with COPD. Six-minute walk distance (6-MWD) was measured as an indicator of functional exercise capacity, and a 6-MWD of <350 m was defined as functional exercise intolerance. Thresholds were determined as values with high specificity (>0.90) and maximal sensitivity. Statistical significance was set at P < 0.01.

RESULTS

The data of 96 patients (74 ± 6 years old; forced expiratory volume in 1-s [FEV₁], 56.5 ± 26.2% predicted) were analyzed; three women and 14 participants with missing data were excluded. Multivariate logistic regression models identified significant associations of PImax (odds ratio at 99% confidence interval [CI]: 0.95 [0.92-0.98]) and %PImax (odds ratio at 99% CI: 0.97 [0.95-0.99]) with 6-MWD, after adjustments for height and FEV₁. C-statistics showed that the area under the curves (99% CI) of PImax and %PImax were comparable (0.87 [0.77-0.96] and 0.83 [0.72-0.94]). The thresholds of PImax and %PImax were 45.1 cmH₂O and 66%; PImax and %PImax also had moderate positive likelihood ratios of 4.44 and 5.00.

CONCLUSIONS

Thresholds of inspiratory muscle strength in men with COPD could help clinicians evaluate whether their patient's inspiratory muscle strength is inadequate to achieve a 6-MWD of ≥350 m, and identify patients who should be targeted for inspiratory muscle training.

ERS statement on respiratory muscle testing at rest and during exercise

Assessing respiratory mechanics and muscle function is critical for both clinical practice and research purposes. Several methodological developments over the past two decades have enhanced our understanding of respiratory muscle function and responses to interventions across the spectrum of health and disease. They are especially useful in diagnosing, phenotyping and assessing treatment efficacy in patients with respiratory symptoms and neuromuscular diseases. Considerable research has been undertaken over the past 17 years, since the publication of the previous American Thoracic Society (ATS)/European Respiratory Society (ERS) statement on respiratory muscle testing in 2002. Key advances have been made in the field of mechanics of breathing, respiratory muscle neurophysiology (electromyography, electroencephalography and transcranial magnetic stimulation) and on respiratory muscle imaging (ultrasound, optoelectronic plethysmography and structured light plethysmography). Accordingly, this ERS task force reviewed the field of respiratory muscle testing in health and disease, with particular reference to data obtained since the previous ATS/ERS statement. It summarises the most recent scientific and methodological developments regarding respiratory mechanics and respiratory muscle assessment by addressing the validity, precision, reproducibility, prognostic value and responsiveness to interventions of various methods. A particular emphasis is placed on assessment during exercise, which is a useful condition to stress the respiratory system.

Respiratory muscle testing in amyotrophic lateral sclerosis: a practical approach

In amyotrophic lateral sclerosis (ALS), respiratory muscle weakness leads to respiratory failure and death. Non-invasive positive pressure ventilation (NIPPV) appears to reduce lung function decline, thus improving survival and quality-of-life of patients affected by the disease. Unfortunately, clinical features and timing to start NIPPV are not well defined. Starting from recent findings, we examine established and novel tests of respiratory muscle function that could help clinicians decide whether and when to start NIPPV in ALS. Non-invasive tests estimate the function of inspiratory, expiratory, and bulbar muscles, whereas clinical examination allows to assess the overall neurologic and respiratory symptoms and general conditions. Most of the studies recommend that together with a thorough clinical evaluation of the patient according to current guidelines, vital capacity, maximal static and sniff nasal inspiratory pressures, maximal static expiratory pressures and peak cough expiratory flow, and nocturnal pulse oximetry be measured. A sound understanding of physiology can guide the physician also through the current armamentarium for additional supportive treatments for ALS, such as symptomatic drugs and new treatments to manage sialorrhea and thickened saliva, cough assistance, air stacking, and physiotherapy. In conclusion, careful clinical and functional evaluation of respiratory function and patient's preference are key determinants to decide "when" and "to whom" respiratory treatments can be provided.

Randomised controlled trial of adjunctive inspiratory muscle training for patients with COPD

BACKGROUND

This study aimed to investigate whether adjunctive inspiratory muscle training (IMT) can enhance the well-established benefits of pulmonary rehabilitation (PR) in patients with COPD.

METHODS

219 patients with COPD (FEV₁: 42%±16% predicted) with inspiratory muscle weakness (PImax: 51±15 cm H₂O) were randomised into an intervention group (IMT+PR; n=110) or a control group (Sham-IMT+PR; n=109) in this double-blind, multicentre randomised controlled trial between February 2012 and October 2016 (ClinicalTrials.gov NCT01397396). Improvement in 6 min walking distance (6MWD) was a priori defined as the primary outcome. Prespecified secondary outcomes included respiratory muscle function and endurance cycling time.

FINDINGS

No significant differences between the intervention group (n=89) and the control group (n=85) in improvements in 6MWD were observed (0.3 m, 95% CI -13 to 14, p=0.967). Patients who completed assessments in the intervention group achieved larger gains in inspiratory muscle strength (effect size: 1.07, p<0.001) and endurance (effect size: 0.79, p<0.001) than patients in the control group. 75 s additional improvement in endurance cycling time (95% CI 1 to 149, p=0.048) and significant reductions in Borg dyspnoea score at isotime during the cycling test (95% CI -1.5 to -0.01, p=0.049) were observed in the intervention group.

INTERPRETATION

Improvements in respiratory muscle function after adjunctive IMT did not translate into additional improvements in 6MWD (primary outcome). Additional gains in endurance time and reductions in symptoms of dyspnoea were observed during an endurance cycling test (secondary outcome) TRIAL REGISTRATION NUMBER: NCT01397396; Results.

Inspiratory muscle training reduces diaphragm activation and dyspnea during exercise in COPD

Among patients with chronic obstructive pulmonary disease (COPD), those with the lowest maximal inspiratory pressures experience greater breathing discomfort (dyspnea) during exercise. In such individuals, inspiratory muscle training (IMT) may be associated with improvement of dyspnea, but the mechanisms for this are poorly understood. Therefore, we aimed to identify physiological mechanisms of improvement in dyspnea and exercise endurance following inspiratory muscle training (IMT) in patients with COPD and low maximal inspiratory pressure (Pi_max). The effects of 8 wk of controlled IMT on respiratory muscle function, dyspnea, respiratory mechanics, and diaphragm electromyography (EMGdi) during constant work rate cycle exercise were evaluated in patients with activity-related dyspnea (baseline dyspnea index <9). Subjects were randomized to either IMT or a sham training control group ( n = 10 each). Twenty subjects (FEV₁ = 47 ± 19% predicted; Pi_max  = -59 ± 14 cmH₂O; cycle ergometer peak work rate = 47 ± 21% predicted) completed the study; groups had comparable baseline lung function, respiratory muscle strength, activity-related dyspnea, and exercise capacity. IMT, compared with control, was associated with greater increases in inspiratory muscle strength and endurance, with attendant improvements in exertional dyspnea and exercise endurance time (all P < 0.05). After IMT, EMGdi expressed relative to its maximum (EMGdi/EMGdi_max) decreased ( P < 0.05) with no significant change in ventilation, tidal inspiratory pressures, breathing pattern, or operating lung volumes during exercise. In conclusion, IMT improved inspiratory muscle strength and endurance in mechanically compromised patients with COPD and low Pi_max. The attendant reduction in EMGdi/EMGdi_max helped explain the decrease in perceived respiratory discomfort despite sustained high ventilation and intrinsic mechanical loading over a longer exercise duration. NEW & NOTEWORTHY In patients with COPD and low maximal inspiratory pressures, inspiratory muscle training (IMT) may be associated with improvement of dyspnea, but the mechanisms for this are poorly understood. This study showed that 8 wk of home-based, partially supervised IMT improved respiratory muscle strength and endurance, dyspnea, and exercise endurance. Dyspnea relief occurred in conjunction with a reduced activation of the diaphragm relative to maximum in the absence of significant changes in ventilation, breathing pattern, and operating lung volumes.

Exertional dyspnoea in COPD: the clinical utility of cardiopulmonary exercise testing

Activity-related dyspnoea is often the most distressing symptom experienced by patients with chronic obstructive pulmonary disease (COPD) and can persist despite comprehensive medical management. It is now clear that dyspnoea during physical activity occurs across the spectrum of disease severity, even in those with mild airway obstruction. Our understanding of the nature and source of dyspnoea is incomplete, but current aetiological concepts emphasise the importance of increased central neural drive to breathe in the setting of a reduced ability of the respiratory system to appropriately respond. Since dyspnoea is provoked or aggravated by physical activity, its concurrent measurement during standardised laboratory exercise testing is clearly important. Combining measurement of perceptual and physiological responses during exercise can provide valuable insights into symptom severity and its pathophysiological underpinnings. This review summarises the abnormal physiological responses to exercise in COPD, as these form the basis for modern constructs of the neurobiology of exertional dyspnoea. The main objectives are: 1) to examine the role of cardiopulmonary exercise testing (CPET) in uncovering the physiological mechanisms of exertional dyspnoea in patients with mild-to-moderate COPD; 2) to examine the escalating negative sensory consequences of progressive respiratory impairment with disease advancement; and 3) to build a physiological rationale for individualised treatment optimisation based on CPET.

Dysfunctional breathing: a review of the literature and proposal for classification

Dysfunctional breathing is a term describing breathing disorders where chronic changes in breathing pattern result in dyspnoea and other symptoms in the absence or in excess of the magnitude of physiological respiratory or cardiac disease. We reviewed the literature and propose a classification system for the common dysfunctional breathing patterns described. The literature was searched using the terms: dysfunctional breathing, hyperventilation, Nijmegen questionnaire and thoraco-abdominal asynchrony. We have summarised the presentation, assessment and treatment of dysfunctional breathing, and propose that the following system be used for classification. 1) Hyperventilation syndrome: associated with symptoms both related to respiratory alkalosis and independent of hypocapnia. 2) Periodic deep sighing: frequent sighing with an irregular breathing pattern. 3) Thoracic dominant breathing: can often manifest in somatic disease, if occurring without disease it may be considered dysfunctional and results in dyspnoea. 4) Forced abdominal expiration: these patients utilise inappropriate and excessive abdominal muscle contraction to aid expiration. 5) Thoraco-abdominal asynchrony: where there is delay between rib cage and abdominal contraction resulting in ineffective breathing mechanics.

This review highlights the common abnormalities, current diagnostic methods and therapeutic implications in dysfunctional breathing. Future work should aim to further investigate the prevalence, clinical associations and treatment of these presentations.

Pharmacological management of breathlessness in COPD: recent advances and hopes for the future

INTRODUCTION

Activity-related breathlessness is often the dominant symptom in patients with chronic obstructive pulmonary disease (COPD) and usually persists despite optimal medical therapy. Currently, our inability to meaningfully alter the pathophysiology of the underlying disease means that we must focus our attention on relieving this distressing symptom so as to improve exercise tolerance and quality of life.

AREAS COVERED

The current review examines the neurobiology of breathlessness and constructs a solid physiological rationale for amelioration of this distressing symptom. We will examine the efficacy of interventions which: 1) reduce the increased central drive to breathe (opioids); 2) improve the respiratory system's ability to appropriately respond to this increased demand (bronchodilators); and 3) address the important affective dimension of breathlessness (anxiolytics). Expert commentary: Advances in our understanding of the mechanisms of activity-related breathlessness in COPD, and its measurement in the clinical domain, now set the stage for the development of effective management strategies on an individual patient basis.

Treadmill walking in water induces greater respiratory muscle fatigue than treadmill walking on land in healthy young men

The purpose of the present study was to investigate the effect of walking in water on respiratory muscle fatigue compared with that of walking on land at the same exercise intensity. Ten healthy males participated in 40-min treadmill walking trials on land and in water at an intensity of 60% of peak oxygen consumption. Respiratory function and respiratory muscle strength were evaluated before and after walking trials. Inspiratory muscle strength and forced expiratory volume in 1 s were significantly decreased immediately after walking in water, and expiratory muscle strength was significantly decreased immediately and 5 min after walking in water compared with the baseline. The decreases of inspiratory and expiratory muscle strength were significantly greater compared with that after walking on land. In conclusion, greater inspiratory and expiratory muscle fatigue was induced by walking in water than by walking on land at the same exercise intensity in healthy young men.

Efficacy of a Novel Method for Inspiratory Muscle Training in People With Chronic Obstructive Pulmonary Disease

BACKGROUND

Most inspiratory muscle training (IMT) interventions in patients with chronic obstructive pulmonary disease (COPD) have been implemented as fully supervised daily training for 30 minutes with controlled training loads using mechanical threshold loading (MTL) devices. Recently, an electronic tapered flow resistive loading (TFRL) device was introduced that has a different loading profile and stores training data during IMT sessions.

OBJECTIVE

The aim of this study was to compare the efficacy of a brief, largely unsupervised IMT protocol conducted using either traditional MTL or TFRL on inspiratory muscle function in patients with COPD.

DESIGN

Twenty patients with inspiratory muscle weakness who were clinically stable and participating in a pulmonary rehabilitation program were randomly allocated to perform 8 weeks of either MTL IMT or TFRL IMT.

METHODS

Participants performed 2 daily home-based IMT sessions of 30 breaths (3-5 minutes per session) at the highest tolerable intensity, supported by twice-weekly supervised sessions. Adherence, progression of training intensity, increases in maximal inspiratory mouth pressure (Pimax), and endurance capacity of inspiratory muscles (Tlim) were evaluated.

RESULTS

More than 90% of IMT sessions were completed in both groups. The TFRL group tolerated higher loads during the final 3 weeks of the IMT program, with similar effort scores on the 10-Item Borg Category Ratio (CR-10) Scale, and achieved larger improvements in Pimax and Tlim than the MTL group.

LIMITATIONS

A limitation of the study was the absence of a study arm involving a sham IMT intervention.

CONCLUSIONS

The short and largely home-based IMT protocol significantly improved inspiratory muscle function in both groups and is an alternative to traditional IMT protocols in this population. Participants in the TFRL group tolerated higher training loads and achieved larger improvements in inspiratory muscle function than those in the MTL group.

An official American Thoracic Society/European Respiratory Society statement: key concepts and advances in pulmonary rehabilitation

BACKGROUND

Pulmonary rehabilitation is recognized as a core component of the management of individuals with chronic respiratory disease. Since the 2006 American Thoracic Society (ATS)/European Respiratory Society (ERS) Statement on Pulmonary Rehabilitation, there has been considerable growth in our knowledge of its efficacy and scope.

PURPOSE

The purpose of this Statement is to update the 2006 document, including a new definition of pulmonary rehabilitation and highlighting key concepts and major advances in the field.

METHODS

A multidisciplinary committee of experts representing the ATS Pulmonary Rehabilitation Assembly and the ERS Scientific Group 01.02, "Rehabilitation and Chronic Care," determined the overall scope of this update through group consensus. Focused literature reviews in key topic areas were conducted by committee members with relevant clinical and scientific expertise. The final content of this Statement was agreed on by all members.

RESULTS

An updated definition of pulmonary rehabilitation is proposed. New data are presented on the science and application of pulmonary rehabilitation, including its effectiveness in acutely ill individuals with chronic obstructive pulmonary disease, and in individuals with other chronic respiratory diseases. The important role of pulmonary rehabilitation in chronic disease management is highlighted. In addition, the role of health behavior change in optimizing and maintaining benefits is discussed.

CONCLUSIONS

The considerable growth in the science and application of pulmonary rehabilitation since 2006 adds further support for its efficacy in a wide range of individuals with chronic respiratory disease.

Diurnal variations in the parameters of pulmonary function and respiratory muscle strength in patients with COPD

OBJECTIVE

To evaluate the magnitude of diurnal changes in the parameters of pulmonary function and respiratory muscle strength/endurance in a sample of patients with COPD.

METHODS

A group of 7 patients underwent spirometry, together with determination of MIP and MEP, at two distinct times (between 8:00 and 8:30 a.m. and between 4:30 and 5:00 p.m.) on a single day. Between assessments, the patients remained at rest in the laboratory.

RESULTS

In accordance with the Global Initiative for Chronic Obstructive Pulmonary Disease staging system, COPD was classified as moderate, severe, and very severe in 1, 3, and 3 of the patients, respectively. From the first to the second assessment, there were significant decreases in FVC, FEV1, and MEP (of 13%, 15%, and 10%, respectively), as well as (less than significant) decreases in PEF, MIP, and maximal voluntary ventilation (of 9%, 3%, and 11%, respectively).

CONCLUSIONS

In this sample of COPD patients, there were diurnal variations in the parameters of pulmonary function and respiratory muscle strength. The values of FEV1, FVC, and MEP were significantly lower in the afternoon than in the morning.

Effect of supine posture on airway blood flow and pulmonary function in stable heart failure

BACKGROUND

The aim of this study was to determine the relationship between body position, pulmonary function (PF) and bronchial blood flow (Q(aw)) in a group of heart failure (HF) and control subjects.

METHODS

Thirty-six subjects were studied: 24 stable, ambulatory HF patients (HF: LVEF=27±6%, age=65±9 yr) and 12 age- and sex-matched controls (CTRL: LVEF=60±7%, age=62±8 yr). Measures of Q˙(aw) (soluble gas method) and PF were collected upright and following 30min in the supine position.

RESULTS

Q˙(aw) was similar between groups and remained unchanged with body position. Declines in forced vital capacity (FVC) and forced expiratory volume in 1s (FEV1) with the supine position were observed in both groups; declines in forced expiratory flow 25-75% (FEF(25-75)) and FEF 75% (FEF75) with the supine position were observed in the HF group only. Changes in Q˙(aw) were related to changes in PF only in the HF patient groups (ΔFVC, % predicted, r = -0.45, p<0.04, ΔFEV1 r = -0.61, p<0.01, ΔFEV1% predicted, r = -0.45, p<0.04).

CONCLUSION

These data demonstrate that relationships between postural changes in Q˙(aw) and PF exist only in the HF population and that the bronchial circulation may contribute to postural PF decline in HF.

Medically unexplained dyspnea: partly moderated by dysfunctional (thoracic dominant) breathing pattern

BACKGROUND

Dysfunctional breathing (DB) may contribute to disproportionate dyspnea and other medically unexplained symptoms. The extent of dysfunctional breathing is often evaluated using the Nijmegen Questionnaire (NQ) or by the presence of abnormal breathing patterns. The NQ was originally devised to evaluate one form of dysfunctional breathing - hyperventilation syndrome. However, the symptoms identified by the NQ are not primarily due to hypocapnia and may be due to other causes including breathing pattern dysfunction.

OBJECTIVES

The relationships between breathing pattern abnormalities and the various categories of NQ symptoms including respiratory or dyspnea symptoms have not been investigated. This study investigates these relationships.

METHOD

62 patients with medically unexplained complaints, that seemed to be associated with tension and breathing dysfunction, were referred, or self-referred, for breathing and relaxation therapy. Dysfunctional breathing symptoms and breathing patterns were assessed at the beginning and end of treatments using the NQ for assessment of DB symptoms, and the Manual Assessment of Respiratory Motion (MARM) to quantify the extent of thoracic dominant breathing. Subscales for the NQ were created in 4 categories, tension, central neurovascular, peripheral neurovascular and dyspnea. Relationships between the NQ (sum scores and subscales) and the MARM were explored.

RESULTS

Mean NQ scores were elevated and mean MARM values for thoracic breathing were also elevated. There was a small correlation pre-treatment between MARM and NQ (r=0.26, p<0.05), but classification of subjects as normal/abnormal on both measurements agreed in 74% (p < 0.001) of patients. From the sub scores of NQ only the respiratory or 'dyspnea' items correlated with the MARM values. Dyspnea was only elevated for subjects with abnormal MARM. After treatment, both MARM and NQ returned to normal values (p< 0.0001). Changes in NQ were largest for subjects with abnormal MARM pre-treatment. There was a large interaction between the change in the NQ sub score dyspnea and initial MARM values. (p<0.001).

Respiratory muscle strength in rheumatic mitral stenosis improves after balloon valvotomy

BACKGROUND

Dyspnea is a common symptom in a patient with valvular heart disease. The mechanism underlying this disease is still uncertain. Respiratory muscle weakness has been proposed to be one of the mechanisms underlying dyspnea in heart failure, but this has not been adequately studied in valvular heart disease.

METHODS

We prospectively studied 20 patients with rheumatic mitral valve stenosis who were candidates for percutaneous balloon mitral valvotomy. Respiratory muscle strength assessment by maximal static inspiratory mouth pressure and maximal static expiratory mouth pressure was done on all patients at baseline and at 1 week after the procedure. The severity of dyspnea in study participants was also studied by the 6-min walk test and visual analog scale.

RESULTS

Balloon valvotomy was followed by a significant improvement in the 6-min walking distance (from 219 +/- 30.15 to 237.55 +/- 32.25 m, P < 0.001), visual analog scale as a measure of dyspnea (from 60.95 +/- 12.16 to 44.4 +/- 13.71 mm, P < 0.001), inspiratory muscle strength (from 51.9 +/- 10.28 to 56.55 +/- 11.87 cmH2O, P < 0.001) and expiratory muscle strength (from 62.15 +/- 19.68 to 67.20 +/- 21.91 cmH2O, P < 0.001).

CONCLUSION

Improvement in dyspnea in mitral stenosis after balloon valvotomy is associated with significant improvement in respiratory muscle strength.

Dyspnea and Activity Limitation in COPD: Mechanical Factors

Dyspnea and activity limitation are the primary symptoms of chronic obstructive pulmonary disease and progress relentlessly as the disease advances. In COPD, dyspnea is multifactorial but abnormal dynamic ventilatory mechanics are believed to be important. Dynamic lung hyperinflation occurs during exercise in the majority of flow-limited patients with chronic obstructive pulmonary disease and may have serious sensory and mechanical consequences. This proposition is supported by several studies, which have shown a close correlation between indices of dynamic lung hyperinflation and measures of both exertional dyspnea and exercise performance. The strength of this association has been further confirmed by studies that have therapeutically manipulated this dependent variable. Relief of exertional dyspnea and improved exercise endurance following bronchodilator therapy correlate well with reduced lung hyperinflation. The mechanisms by which dynamic lung hyperinflation give rise to exertional dyspnea and exercise intolerance are complex. However, recent mechanistic studies suggest that dynamic lung hyperinflation-induced volume restriction and consequent neuromechanical uncoupling of the respiratory system are key mechanisms. This review examines, in some detail, the derangements of ventilatory mechanics that are peculiar to chronic obstructive pulmonary disease and attempts to provide a mechanistic rationale for the attendant respiratory discomfort and activity limitation.

Relation between inflammation and symptoms in asthma

Asthma symptoms are the main reason for healthcare utilization and are a fundamental parameter for the evaluation of asthma control. Currently, asthma is defined as a chronic inflammatory disease. A French expert group studied the association between inflammation and asthma symptoms by carrying out a critical review of the international literature. Uncontrolled asthmatics have an increased number of polynuclear eosinophils in the induced sputum and an increased production of exhaled NO. Control by anti-inflammatory treatment is accompanied by a reduction in bronchial eosinophilia and exhaled NO. Asthma symptoms are the result of complex mechanisms and many factors modify their perception. Experimental data suggest that there is a relationship between the perception of symptoms and eosinophilic inflammation and that inhaled corticoid therapy improves this perception. Although they are still not applicable in routine practice, follow-up strategies based on the evaluation of inflammation are thought to be more effective in reducing exacerbations than those usually recommended based on symptoms and sequential analysis of respiratory function. Inhaled corticosteroid therapy is the reference disease-modifying therapy for persistent asthma. Recent studies demonstrated that adjustment of anti-inflammatory treatment based on symptoms is an effective strategy to prevent exacerbations and reduce the total number of doses of inhaled corticosteroids.

[The relationship between inflammation and symptoms in asthma]

In asthma, symptoms are the main reason for recourse to healthcare and are a fundamental parameter for the evaluation of asthma control. Currently, asthma is defined as a chronic inflammatory disease. Uncontrolled asthmatics have an increased number of eosinophils in induced sputum and an increased production of exhaled NO. Control by anti-inflammatory treatment is accompanied by a reduction in bronchial eosinophilia and exhaled NO. Asthma symptoms are the result of complex mechanisms and many factors modify their perception. Experimental data suggests that there is a relationship between the perception of symptoms and eosinophilic inflammation, and that inhaled corticoid therapy improves this perception. Although they are still not applicable in routine practice, follow-up strategies based on the evaluation of inflammation are thought to be more effective in reducing exacerbations than those usually recommended based on retrospective evaluation of symptoms and sequential analysis of respiratory function. Inhaled corticosteroid therapy is the reference maintenance therapy for persistent asthma and adjustment of anti-inflammatory treatment based on symptoms is an effective strategy to prevent exacerbations and reduce the total dose of inhaled corticosteroids. A French expert group has undertaken a study of the association between inflammation and asthma symptoms by carrying out a critical review of the international literature.

Diaphragm adaptations in patients with COPD

Inspiratory muscle weakness in patients with COPD is of major clinical relevance. For instance, maximum inspiratory pressure generation is an independent determinant of survival in severe COPD. Traditionally, inspiratory muscle weakness has been ascribed to hyperinflation-induced diaphragm shortening. However, more recently, invasive evaluation of diaphragm contractile function, structure, and biochemistry demonstrated that cellular and molecular alterations occur, of which several can be considered pathologic of nature. Whereas the fiber type shift towards oxidative type I fibers in COPD diaphragm is regarded beneficial, rendering the overloaded diaphragm more resistant to fatigue, the reduction of diaphragm fiber force generation in vitro likely contributes to diaphragm weakness. The reduced diaphragm force generation at single fiber level is associated with loss of myosin content in these fibers. Moreover, the diaphragm in COPD is exposed to oxidative stress and sarcomeric injury. This review postulates that the oxidative stress and sarcomeric injury activate proteolytic machinery, leading to contractile protein wasting and, consequently, loss of force generating capacity of diaphragm fibers in patients with COPD. Interestingly, several of these presumed pathologic alterations are already present early in the course of the disease (GOLD I/II), although these patients appear not limited in their daily life activities. Treatment of diaphragm dysfunction in COPD is complex since its etiology is unclear, but recent findings indicate the ubiquitin-proteasome pathway as a prime target to attenuate diaphragm wasting in COPD.

Pulmonary rehabilitation in chronic obstructive pulmonary disease

Pulmonary rehabilitation, a multidisciplinary and structured intervention for patients with chronic pulmonary diseases, has been shown to improve exercise tolerance, reduce dyspnea and improve health-related quality of life. Pulmonary rehabilitation appears to be cost-effective, since it reduces health care utilization. Exercise training represents the cornerstone of every pulmonary rehabilitation program. To obtain clinically relevant effects, training should closely supervised, of high intensity, lasting 30-45 min for at least 3 days/week. Patients should undertake a minimum of 20 sessions, but longer programs result in larger and more long-lasting effects. Education and self-management programs have been shown to result in a substantial reduction in hospital admissions. Nutritional intervention should be considered for patients who are underweight or those with body composition abnormalities. Patients reporting fear and anxiety may benefit from psychosocial support, and the integration of occupational therapy in a pulmonary rehabilitation program can improve independence in activity. Multidisciplinary pulmonary rehabilitation is preferably implemented in an outpatient hospital- or community-based setting. Inpatient programs are suited for patients with limited transportation capabilities or severe deconditioning. The most convincing effects of home-based rehabilitation are in maintaining the improvements obtained in an outpatient setting.

Perception of airway obstruction and airway inflammation in asthma: a review

Dyspnea has a multifactorial nature and the exact mechanism that causes breathlessness in asthma is not fully understood. There is compelling evidence that factors other than merely mechanical ones take part in the pathophysiology of breathlessness. Some recent reports attribute airway inflammation, which may contribute to the unexplained variability in the perception of dyspnea associated with bronchoconstriction. Eosinophil airway inflammation has been proposed as a determinant of breathlessness via mechanisms affecting either the mechanical pathways that control breathlessness or the afferent nerves involved in perception of dyspnea. In this review, data on the interrelation between inflammation and dyspnea sensation and the impact of treatment on dyspnea sensation are discussed. We conclude that regardless of whether mechanical or chemical inflammatory factors are involved, much variability in dyspnea scores remains unexplained.

Comparison of 2 Methods for Inspiratory Muscle Training in Patients With Chronic Obstructive Pulmonary Disease

OBJECTIVE

The aim of this study was to compare the use of threshold and resistive load devices for inspiratory muscle training in patients with chronic obstructive pulmonary disease (COPD). A randomized prospective trial was designed to compare use of the 2 devices under training or control conditions.

PATIENTS AND METHODS

Thirty-three patients with moderate or severe COPD were randomly assigned to home treatment with a threshold device, a resistive load device, or a control situation in which either of those devices was maintained at a minimum load throughout the study. Training was performed daily in 2 sessions of 15 minutes each for 6 weeks. In the patients who underwent training with threshold (n=12) and resistive load (n=11) devices, the loads used were adjusted weekly until the maximum tolerated load was reached to ensure that the interventions were as equivalent as possible. Respiratory function, respiratory muscle function, and quality of life were assessed before and after training and the different inspiratory pressure profiles were compared between training groups.

RESULTS

Both peak inspiratory pressure and scores on the Chronic Respiratory Questionnaire (CRQ) improved in the groups that received inspiratory muscle training compared with control subjects: maximal static inspiratory pressure increased from 86 cmH2O to 104.25 cmH2O (P< .01) in the threshold device group and from 91.36 cm H2O to 105.7 cmH2O (P< .01) in the resistive load device group. The resistive load group showed the largest increase in CRQ quality-of-life scores. Differences between the dyspnea score on the CRQ at the beginning and end of the training period were as follows: 3 points in the resistive load group, 2.58 in the threshold group, and 2.5 in the control group. Significant differences in duty cycle measured during training sessions were observed between groups at the end of training (0.31 in the threshold group and 0.557 in the resistive load group), but the mean pressure-time index was similar (0.11) in both groups because of the greater peak and mean inspiratory pressures in the threshold device group.

CONCLUSIONS

Load readjustment allowed equivalent training intensities to be achieved with different inspiratory pressure profiles. Our study demonstrated the effectiveness of inspiratory muscle training without control of breathing pattern but showed no superiority of one training method over another.

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.

The Influence of the Self-Contained Breathing Apparatus (SCBA) on Ventilatory Function and Maximal Exercise

Our previous work showed that breathing low density gases during exercise with the self-contained breathing apparatus (SCBA) improves maximal ventilation (VE) and maximal oxygen consumption [Formula: see text] This suggests that the SCBA limits exercise by adding a resistive load to breathing. In this study we compared [Formula: see text] with and without the various components comprising the SCBA to determine their impact on [Formula: see text] Twelve males performed 4 randomly ordered incremental exercise tests to exhaustion on a treadmill: (1) low-resistance breathing valve only (CON); (2) full SCBA (SCBA); (3) SCBA regulator only (REG); and (4) carrying the cylinder and harness assembly but breathing through a low-resistance breathing valve (PACK). Compared to CON, [Formula: see text] was reduced to a similar extent in the SCBA and REG trials (14.9% and 13.1%, respectively). The PACK condition also reduced [Formula: see text] but to a lesser extent (4.8 ± 5.3%). At [Formula: see text][Formula: see text] was decreased and expiratory mouth pressure and external breathing resistance (BR) were increased in both the SCBA and REG trials. There was a significant correlation between the change in maximal [Formula: see text] and [Formula: see text] with the SCBA. The results show that the SCBA reduces [Formula: see text] by limiting [Formula: see text] secondary to the increased BR of the SCBA regulator. Key words: ventilation, breathing resistance, expiratory flow limitation, [Formula: see text]

Dyspnoea in health and obstructive pulmonary disease : the role of respiratory muscle function and training

A consistent finding of recent research on respiratory muscle training (RMT) in healthy humans has been an attenuation of respiratory discomfort (dyspnoea) during exercise. We argue that the neurophysiology of dyspnoea can be explained in terms of Cambell's paradigm of length-tension inappropriateness. In the context of this paradigm, changes in the contractile properties of the respiratory muscles modify the intensity of dyspnoea predominantly by changing the required level of motor outflow to these respiratory muscles. Thus, factors that impair the contractile properties of the respiratory muscles (e.g. the pattern of tension development, functional weakening and fatigue) have the potential to increase the intensity of dyspnoea, while factors that improve the contractile properties of these respiratory muscles (e.g. RMT) have the potential to reduce the intensity of dyspnoea. In patients with obstructive pulmonary disease, functional weakening of the inspiratory muscles in response to dynamic lung hyperinflation appears to be a central component of dyspnoea. A decrease in the intensity of respiratory effort sensation (during exercise and loaded breathing) has been observed in both healthy individuals and patients with obstructive pulmonary disease after RMT. We conclude that RMT has the potential to reduce the severity of dyspnoea in healthy individuals and in patients with obstructive pulmonary disease, and that this probably occurs via a reduction in the level of motor outflow. Further work is required to clarify the role of RMT in the management of other disease conditions in which the function of the respiratory muscles is impaired, or the loads that they must overcome are elevated (e.g. cardiorespiratory and neuromuscular disorders).

Chest wall kinematics and breathlessness during pursed-lip breathing in patients with COPD

BACKGROUND

Pursed-lip breathing (PLB) is a strategy often spontaneously employed by patients with COPD during distress situations. Whether and to what extent PLB affects operational lung volume is not known. Also, conflicting reports deal with PLB capability of decreasing breathlessness.

PARTICIPANTS AND MEASUREMENTS

Twenty-two patients with mild-to-severe COPD were studied. Volumes of chest wall (CW) compartments (rib cage [RC] and abdomen) were assessed using an optoelectronic plethysmograph. Dyspnea was assessed by a modified Borg scale.

RESULTS

Compared to spontaneous breathing, patients with PLB exhibited a significant reduction (mean +/- SD) in end-expiratory volume of the CW (VCW) [VCWee; - 0.33 +/- 0.24 L, p < 0.000004], and a significant increase in end-inspiratory VCW (VCWei; + 0.32 +/- 0.43 L, p < 0.003). The decrease in VCWee, mostly due to the decrease in end-expiratory volume of the abdomen (VAbee) [- 0.25 +/- 0.21 L, p < 0.00002], related to baseline FEV(1) (p < 0.02) and to the increase in expiratory time (TE) [r(2) = 0.49, p < 0.0003] and total time of the respiratory cycle (TTOT) [r(2) = 0.35, p < 0.004], but not to baseline functional residual capacity (FRC). Increase in tidal volume (VT) of the chest wall (+ 0.65 +/- 0.48 L, p < 0.000004) was shared between VT of the abdomen (0.31 +/- 0.23 L, p < 0.000004) and VT of the rib cage (+ 0.33 +/- 0.29 L, p < 0.00003). Borg score decreased with PLB (p < 0.04). In a stepwise multiple regression analysis, decrease in VCWee accounted for 27% of the variability in Borg score at 99% confidence level (p < 0.008).

CONCLUSIONS

Changes in VCWee related to baseline airway obstruction but not to hyperinflation (FRC). By lengthening of TE and TTOT, PLB decreases VCWee and reduces breathlessness.

Exercise training during rehabilitation of patients with COPD: a current perspective

Patients with chronic obstructive pulmonary disease (COPD) suffer frequently from physiologic and psychological impairments, such as dyspnea, peripheral muscle weakness, exercise intolerance, decreased health-related quality of life (HRQOL) and emotional distress. Rehabilitation programmes have shown to result in significant changes in perceived dyspnea and fatigue, utilisation of healthcare resources, exercise performance and HRQOL. Exercise training, which consists of whole-body exercise training and local resistance training, is the cornerstone of these programmes. Regrettably, the positive effects of respiratory rehabilitation deteriorate over time, especially after short programmes. Hence, attention should be given to the aftercare of these patients to prevent them to revert again to a sedentary lifestyle. On empirical basis three possibilities seem to be clinically feasible: (1) continuous outpatient exercise training; (2) exercise training in a home-based or community-based setting; or (3) exercise training sessions in a group of asthma and COPD patients.

Overall contribution of chest wall hyperinflation to breathlessness in asthma

BACKGROUND

Studies suggest that the increased volume of both abdominal and rib cage compartments of the chest wall contribute to dyspnea during methacholine-induced airway narrowing.

MATERIAL

Eight male patients with asthma aged 34 +/- 13 years (mean +/- SD) before and during methacholine challenge.

METHODS

The volume of the chest wall (Vcw), volume of the abdomen (Vab), and volume of the rib cage (Vrc) were measured by using a three-dimensional optoelectronic plethysmography.

RESULTS

During methacholine challenge, the increase in end-expiratory Vcw (Vcw,ee) [0.55 +/- 0.23 L, p < 0.001] was due to increased Vrc (0.37 +/- 0.20 L, p < 0.01) and, to a lesser extent, Vab (0.18 +/- 0.10 L, p < 0.005). Linear univariate regression analysis showed that changes in dyspnea (Borg scale) with the highest methacholine dose correlated with both DeltaFEV(1) and DeltaVcw,ee. Multiple regression analysis with the Borg score as dependent variable and all other ventilatory indexes as independent variables showed that DeltaVcw,ee and DeltaFEV(1) were the only significant contributors to the Borg score. Taken together Vcw,ee and FEV(1) explained 56% of variance in the Borg score (r(2) = 0.56), although Vcw,ee explained 48% of it.

CONCLUSIONS

During methacholine challenge in patients with asthma, the overall increase in Vcw,ee is a better predictor of dyspnea that the reduction in FEV(1).

Assessing respiratory drive and central motor pathway in humans: clinical implications

Feedback from sensory elements as well as projection from higher Central Nervous System structures modify the level and pattern of motor outflow to the respiratory muscles and hence ventilation. In this review we describe the different methods to evaluate the degree to which higher centers determine the level and pattern of ventilation and coordinate use of the respiratory muscles in healthy humans and in patients with a number of respiratory disorders.

Ventilatory limitations in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a heterogeneous disorder characterized by dysfunction of the small and large airways, as well as by destruction of the lung parenchyma and vasculature, in highly variable combinations. Breathlessness and exercise intolerance are the most common symptoms in COPD and progress relentlessly as the disease advances. Exercise intolerance is multifactorial, but in more severe disease, ventilatory limitation is often the proximate exercise-limiting event. Multiple factors determine ventilatory limitation and include integrated abnormalities in ventilatory mechanics and ventilatory muscle function as well as increased ventilatory demands (as a result of gas exchange abnormalities) and alterations in the neuroregulatory control of breathing. Despite its heterogeneity, the pathophysiological hallmark of COPD is expiratory flow limitation. When ventilation increases in flow-limited patients during exercise, air trapping is inevitable and causes further dynamic lung hyperinflation (DH) above the already increased resting volumes. DH causes elastic and inspiratory threshold loading of inspiratory muscles already burdened with increased resistive work. It seriously constrains tidal volume expansion during exercise. DH compromises the ability of the inspiratory muscles to generate pressure, and the positive intrathoracic pressures likely contribute to cardiac impairment during exercise. Progressive DH hastens the development of critical ventilatory constraints that limit exercise and, by causing serious neuromechanical uncoupling, contributes importantly to the quality and intensity of breathlessness. The corollary of this is that therapeutic interventions that reduce operational lung volumes during exercise, by improving lung emptying or by reducing ventilatory demand (which delays the rate of DH), result in clinically meaningful improvement of exercise endurance and symptoms in disabled COPD patients.

Respiratory muscle function and drive in chronic obstructive pulmonary disease

Respiratory, and particularly inspiratory, muscle function is altered in COPD. Many of these alterations are secondary to a mechanical disadvantage related to hyperinflation. Other factors, including corticosteroid therapy and nutritional depletion, are also deleterious to muscle function. In addition, the load imposed on the respiratory muscles is increased in COPD. Combined with the altered respiratory muscle function, this increase induces important changes in respiratory muscle drive and recruitment. Moreover, the imbalance between respiratory muscle function and load is an important determinant of dyspnea and hypercapnia. Because much of the lung and airway derangements are irreversible in COPD, the respiratory muscles appear to be an attractive target for therapeutic interventions.