Role of hypoxemia and pulmonary mechanics in exercise limitation in interstitial lung disease

Supplemental Oxygen Therapy in Interstitial Lung Disease: A Narrative Review

Patients with interstitial lung diseases (ILD) often have hypoxemia at rest and/or with exertion, for which supplemental oxygen is commonly prescribed. The number of patients with ILD who require supplemental oxygen is unknown, although estimates suggest it could be as much as 40%; many of these patients may require high-flow support (>4 L/min). Despite its frequent use, there is limited evidence for the impact of supplemental oxygen on clinical outcomes in ILD, with recommendations for its use primarily based on older studies in patients with chronic obstructive pulmonary disease. Oxygen use in ILD is rarely included as an outcome in clinical trials. Available evidence suggests that supplemental oxygen in ILD may improve quality of life and some exercise parameters in patients whose hypoxemia is a limiting factor; however, oxygen therapy also places new burdens and barriers on some patients that may counter its beneficial effects. The cost of supplemental oxygen in ILD is also unknown but likely represents a significant portion of overall healthcare costs in these patients. Current Centers for Medicare and Medicaid reimbursement policies provide only a modest increase in payment for high oxygen flows, which may negatively impact access to oxygen services and equipment for some patients with ILD. Future studies should examine clinical and quality-of-life outcomes for oxygen use in ILD. In the meantime, given the current limited evidence for supplemental oxygen and considering cost factors and other barriers, providers should take a patient-focused approach when considering supplemental oxygen prescriptions in patients with ILD.

Cardiopulmonary exercise testing in interstitial lung diseases and the value of ventilatory efficiency

Interstitial lung diseases (ILDs) are diverse parenchymal pulmonary disorders, primarily characterised by alveolar and interstitial inflammation and/or fibrosis, and sharing pathophysiological similarities. Thus, patients generally harbour common respiratory symptoms, lung function abnormalities and modified exercise adaptation. The most usual and disabling complaint is exertional dyspnoea, frequently responsible for premature exercise interruption. Cardiopulmonary exercise testing (CPET) is increasingly used for the clinical assessment of patients with ILD. This is because exercise performance or dyspnoea on exertion cannot reliably be predicted by resting pulmonary function tests. CPET, therefore, provides an accurate evaluation of functional capacity on an individual basis. CPET can unmask anomalies in the integrated functions of the respiratory, cardiovascular, metabolic, peripheral muscle and neurosensory systems in ILDs. CPET uniquely provides an evaluation of all above aspects and can help clinicians shape ILD patient management. Preliminary evidence suggests that CPET may also generate valuable prognostic information in ILDs and can be used to shed light on the presence of associated pulmonary hypertension. This review aims to provide comprehensive and updated evidence concerning the clinical utility of CPET in ILD patients, with particular focus on the physiological and clinical value of ventilatory efficiency (V˙_E/V˙_CO2 ).

Pulmonary rehabilitation for interstitial lung disease

BACKGROUND

Interstitial lung disease (ILD) is characterised by reduced functional capacity, dyspnoea and exercise-induced hypoxia. Pulmonary rehabilitation is often used to improve symptoms, health-related quality of life and functional status in other chronic lung conditions. There is accumulating evidence for comparable effects of pulmonary rehabilitation in people with ILD. However, further information is needed to clarify the long-term benefit and to strengthen the rationale for pulmonary rehabilitation to be incorporated into standard clinical management of people with ILD. This review updates the results reported in 2014.

OBJECTIVES

To determine whether pulmonary rehabilitation in people with ILD has beneficial effects on exercise capacity, symptoms, quality of life and survival compared with no pulmonary rehabilitation in people with ILD. To assess the safety of pulmonary rehabilitation in people with ILD.

SEARCH METHODS

We searched CENTRAL, MEDLINE (Ovid), Embase (Ovid), CINAHL (EBSCO) and PEDro from inception to April 2020. We searched the reference lists of relevant studies, international clinical trial registries and respiratory conference abstracts to look for qualifying studies.

SELECTION CRITERIA

We included randomised controlled trials and quasi-randomised controlled trials in which pulmonary rehabilitation was compared with no pulmonary rehabilitation or with other therapy in people with ILD of any origin.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data and assessed risk of bias. We contacted study authors to request missing data and information regarding adverse effects. We specified a priori subgroup analyses for participants with idiopathic pulmonary fibrosis (IPF) and participants with severe lung disease (low diffusing capacity or desaturation during exercise). There were insufficient data to perform the prespecified subgroup analysis for type of exercise training modality.

MAIN RESULTS

For this update, we included an additional 12 studies resulting in a total of 21 studies. We included 16 studies in the meta-analysis (356 participants undertook pulmonary rehabilitation and 319 were control participants). The mean age of participants ranged from 36 to 72 years and included people with ILD of varying aetiology, sarcoidosis or IPF (with mean transfer factor of carbon dioxide (TLCO) % predicted ranging from 37% to 63%). Most pulmonary rehabilitation programmes were conducted in an outpatient setting, with a small number conducted in home-based, inpatient or tele-rehabilitation settings. The duration of pulmonary rehabilitation ranged from three to 48 weeks. There was a moderate risk of bias due to the absence of outcome assessor blinding and intention-to-treat analyses and the inadequate reporting of randomisation and allocation procedures in 60% of the studies. Pulmonary rehabilitation probably improves the six-minute walk distance (6MWD) with mean difference (MD) of 40.07 metres, 95% confidence interval (CI) 32.70 to 47.44; 585 participants; moderate-certainty evidence). There may be improvements in peak workload (MD 9.04 watts, 95% CI 6.07 to 12.0; 159 participants; low-certainty evidence), peak oxygen consumption (MD 1.28 mL/kg/minute, 95% CI 0.51 to 2.05; 94 participants; low-certainty evidence) and maximum ventilation (MD 7.21 L/minute, 95% CI 4.10 to 10.32; 94 participants; low-certainty evidence). In the subgroup of participants with IPF, there were comparable improvements in 6MWD (MD 37.25 metres, 95% CI 26.16 to 48.33; 278 participants; moderate-certainty evidence), peak workload (MD 9.94 watts, 95% CI 6.39 to 13.49; low-certainty evidence), VO₂ (oxygen uptake) peak (MD 1.45 mL/kg/minute, 95% CI 0.51 to 2.40; low-certainty evidence) and maximum ventilation (MD 9.80 L/minute, 95% CI 6.06 to 13.53; 62 participants; low-certainty evidence). The effect of pulmonary rehabilitation on maximum heart rate was uncertain. Pulmonary rehabilitation may reduce dyspnoea in participants with ILD (standardised mean difference (SMD) -0.36, 95% CI -0.58 to -0.14; 348 participants; low-certainty evidence) and in the IPF subgroup (SMD -0.41, 95% CI -0.74 to -0.09; 155 participants; low-certainty evidence). Pulmonary rehabilitation probably improves health-related quality of life: there were improvements in all four domains of the Chronic Respiratory Disease Questionnaire (CRQ) and the St George's Respiratory Questionnaire (SGRQ) for participants with ILD and for the subgroup of people with IPF. The improvement in SGRQ Total score was -9.29 for participants with ILD (95% CI -11.06 to -7.52; 478 participants; moderate-certainty evidence) and -7.91 for participants with IPF (95% CI -10.55 to -5.26; 194 participants; moderate-certainty evidence). Five studies reported longer-term outcomes, with improvements in exercise capacity, dyspnoea and health-related quality of life still evident six to 12 months following the intervention period (6MWD: MD 32.43, 95% CI 15.58 to 49.28; 297 participants; moderate-certainty evidence; dyspnoea: MD -0.29, 95% CI -0.49 to -0.10; 335 participants; SGRQ Total score: MD -4.93, 95% CI -7.81 to -2.06; 240 participants; low-certainty evidence). In the subgroup of participants with IPF, there were improvements at six to 12 months following the intervention for dyspnoea and SGRQ Impact score. The effect of pulmonary rehabilitation on survival at long-term follow-up is uncertain. There were insufficient data to allow examination of the impact of disease severity or exercise training modality. Ten studies provided information on adverse events; however, there were no adverse events reported during rehabilitation. Four studies reported the death of one pulmonary rehabilitation participant; however, all four studies indicated this death was unrelated to the intervention received.

AUTHORS' CONCLUSIONS

Pulmonary rehabilitation can be performed safely in people with ILD. Pulmonary rehabilitation probably improves functional exercise capacity, dyspnoea and quality of life in the short term, with benefits also probable in IPF. Improvements in functional exercise capacity, dyspnoea and quality of life were sustained longer term. Dyspnoea and quality of life may be sustained in people with IPF. The certainty of evidence was low to moderate, due to inadequate reporting of methods, the lack of outcome assessment blinding and heterogeneity in some results. Further well-designed randomised trials are needed to determine the optimal exercise prescription, and to investigate ways to promote longer-lasting improvements, particularly for people with IPF.

Home Oxygen Therapy for Adults with Chronic Lung Disease. An Official American Thoracic Society Clinical Practice Guideline

Background: Evidence-based guidelines are needed for effective delivery of home oxygen therapy to appropriate patients with chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD).Methods: The multidisciplinary panel created six research questions using a modified Delphi approach. A systematic review of the literature was completed, and the Grading of Recommendations Assessment, Development and Evaluation approach was used to formulate clinical recommendations.Recommendations: The panel found varying quality and availability of evidence and made the following judgments: 1) strong recommendations for long-term oxygen use in patients with COPD (moderate-quality evidence) or ILD (low-quality evidence) with severe chronic resting hypoxemia, 2) a conditional recommendation against long-term oxygen use in patients with COPD with moderate chronic resting hypoxemia, 3) conditional recommendations for ambulatory oxygen use in patients with COPD (moderate-quality evidence) or ILD (low-quality evidence) with severe exertional hypoxemia, 4) a conditional recommendation for ambulatory liquid-oxygen use in patients who are mobile outside the home and require >3 L/min of continuous-flow oxygen during exertion (very-low-quality evidence), and 5) a recommendation that patients and their caregivers receive education on oxygen equipment and safety (best-practice statement).Conclusions: These guidelines provide the basis for evidence-based use of home oxygen therapy in adults with COPD or ILD but also highlight the need for additional research to guide clinical practice.

Supplemental oxygen for the management of dyspnea in interstitial lung disease

PURPOSE OF REVIEW

This article presents a summary of the evidence relating to supplemental oxygen use for the management of dyspnea in patients with interstitial lung disease (ILD).

RECENT FINDINGS

In contrast to the majority of the available literature, recent findings suggest that supplemental oxygen can significantly reduce exertional dyspnea in ILD. ILD patients' need for supplemental oxygen often surpasses the levels that the most commonly used oxygen delivery systems provide. More effective delivery of supplemental oxygen has the potential for greater relief of dyspnea. There is also evidence suggesting that indications for supplemental oxygen may differ in ILD compared with other chronic lung diseases.

SUMMARY

Large clinical trials are needed to determine if the reductions in dyspnea with supplemental oxygen observed in the laboratory setting can translate into meaningful benefits in everyday life for patients with ILD. More effective and practical oxygen delivery systems are needed. Future guidelines should consider including recommendations addressing the potential role of supplemental oxygen for mildly hypoxemic patients with ILD as well as recommendations specific to supplemental oxygen use for exercise training in ILD.

Exercise Pathophysiology in Interstitial Lung Disease

Interstitial lung disease (ILD) is a heterogeneous group of disorders that primarily affect the lung parenchyma. Patients with ILD have reduced lung volumes, impaired pulmonary gas exchange, and decreased cardiovascular function. These pathologic features of ILD become exacerbated during physical exertion, leading to exercise intolerance and abnormally high levels of exertional dyspnea. In this review, the authors summarize the primary pathophysiologic features of patients with ILD and their effect on the integrative response to exercise.

Uncovering the mechanisms of exertional dyspnoea in combined pulmonary fibrosis and emphysema

The prevailing view is that exertional dyspnoea in patients with combined idiopathic pulmonary fibrosis (IPF) and emphysema (CPFE) can be largely explained by severe hypoxaemia. However, there is little evidence to support these assumptions.We prospectively contrasted the sensory and physiological responses to exercise in 42 CPFE and 16 IPF patients matched by the severity of exertional hypoxaemia. Emphysema and pulmonary fibrosis were quantified using computed tomography. Inspiratory constraints were assessed in a constant work rate test: capillary blood gases were obtained in a subset of patients.CPFE patients had lower exercise capacity despite less extensive fibrosis compared to IPF (p=0.004 and 0.02, respectively). Exertional dyspnoea was the key limiting symptom in 24 CPFE patients who showed significantly lower transfer factor, arterial carbon dioxide tension and ventilatory efficiency (higher minute ventilation (V'_E)/carbon dioxide output (V'_CO2 ) ratio) compared to those with less dyspnoea. However, there were no between-group differences in the likelihood of pulmonary hypertension by echocardiography (p=0.44). High dead space/tidal volume ratio, low capillary carbon dioxide tension emphysema severity (including admixed emphysema) and traction bronchiectasis were related to a high V'_E/V'_CO2 ratio in the more dyspnoeic group. V'_E/V'_CO2 nadir >50 (OR 9.43, 95% CI 5.28-13.6; p=0.0001) and total emphysema extent >15% (2.25, 1.28-3.54; p=0.01) predicted a high dyspnoea burden associated with severely reduced exercise capacity in CPFEContrary to current understanding, hypoxaemia per se is not the main determinant of exertional dyspnoea in CPFE. Poor ventilatory efficiency due to increased "wasted" ventilation in emphysematous areas and hyperventilation holds a key mechanistic role that deserves therapeutic attention.

Qualitative dimensions of exertional dyspnea in fibrotic interstitial lung disease

Unsatisfied inspiration is commonly reported during exercise by patients with interstitial lung disease (ILD). However, the physiological basis of perceived dyspnea quality in this population has not been evaluated. We examined the relationship between dyspnea quality and indices of ventilatory-mechanical limitations during exercise in patients with fibrotic ILD. Sixteen fibrotic ILD patients (12 male) with a median age of 64 years (range 49-81), FVC 71%-predicted (51-100), and DL_CO 47%-predicted (27-77) performed incremental and constant work-rate cycle exercise tests to exhaustion. Ventilatory responses were recorded at rest, throughout exercise, and at peak exercise. Dyspnea quality was serially assessed using a 4-item list from which participants selected the phrase that best described their breathing compared to rest. Increased work/effort was the dominant descriptor of dyspnea throughout exercise, but with increased selection of unsatisfied inspiration following the inflection point of tidal volume relative to ventilation. Delaying or preventing ILD patients from reaching a critically reduced IRV may have implications for symptom management.

Differential Pulmonary Rehabilitation Outcomes in Patients With and Without COPD: ROLE OF GENDER

PURPOSE

Individuals with all forms of pulmonary disease are referred for pulmonary rehabilitation. This study examines pulmonary rehabilitation outcomes between individuals with chronic obstructive lung disease (COPD) and non-COPD disease and the impact of gender.

METHODS

This is a retrospective study at a tertiary center. The primary endpoint was the difference in 6-min walk test distance. Secondary measurements included treadmill and NuStep minutes; biceps curls and front arm raises load; quality of life measured by the St George's Respiratory Questionnaire; and University of California San Diego-Shortness of Breath Questionnaire (UCSD-SOBQ) scores.

RESULTS

Eighty patients were included: 38 men (23 COPD, 15 non-COPD) and 42 women (31 COPD, 11 non-COPD). There was a statistically significant improvement in 6-min walk test distances pre- to post-pulmonary rehabilitation for all participants, P = .0003. Although both the COPD and non-COPD groups demonstrated overall improvement (P < .0004 and P = .02, respectively), subgroup analysis showed no statistically significant change in the non-COPD group when divided by gender. There was a significant statistical improvement in lower and upper extremity strength in all participants. Only women with COPD showed a statistically significant improvement with respect to overall quality of life as measured by St. George's Respiratory Questionnaire (P = .01). Women showed significant improvement in their depression score, as well as a trend toward improvement in the University of California San Diego-Shortness of Breath Questionnaire, while only men with COPD showed any improvement in their sleep quality measured by the Pittsburgh Sleep Quality Index.

CONCLUSIONS

Pulmonary rehabilitation results in different but improved outcomes regardless of gender or disease state.

Use of cardiopulmonary exercise testing to assess early ventilatory changes related to occupational particulate matter

Spirometry has been used as the main strategy for assessing ventilatory changes related to occupational exposure to particulate matter (OEPM). However, in some cases, as one of its limitations, it may not be sensitive enough to show abnormalities before extensive damage, as seen in restrictive lung diseases. Therefore, we hypothesized that cardiopulmonary exercise testing (CPET) may be better than spirometry to detect early ventilatory impairment caused by OEPM. We selected 135 male workers with at least one year of exposure. After collection of self-reported socioeconomic status, educational level, and cardiovascular risk data, participants underwent spirometry, CPET, body composition assessment (bioelectrical impedance), and triaxial accelerometry (for level of physical activity in daily life). CPET was performed using a ramp protocol on a treadmill. Metabolic, cardiovascular, ventilatory, and submaximal relationships were measured. We compared 52 exposed to 83 non-exposed workers. Multiple linear regressions were developed using spirometry and CPET variables as outcomes and OEPM as the main predictor, and adjusted by the main covariates. Our results showed that OEPM was associated with significant reductions in peak minute ventilation, peak tidal volume, and breathing reserve index. Exposed participants presented shallower slope of ΔVT/ΔlnV̇E (breathing pattern), i.e., increased tachypneic breathing pattern. The OEPM explained 7.4% of the ΔVT/ΔlnV̇E variability. We found no significant influence of spirometric indices after multiple linear regressions. We conclude that CPET might be a more sensitive feature of assessing early pulmonary impairment related to OEPM. Our cross-sectional results suggested that CPET is a promising tool for the screening of asymptomatic male workers.

High Oxygen Delivery to Preserve Exercise Capacity in Patients with Idiopathic Pulmonary Fibrosis Treated with Nintedanib. Methodology of the HOPE-IPF Study

RATIONALE

Pulmonary rehabilitation improves dyspnea and exercise capacity in idiopathic pulmonary fibrosis (IPF); however, it is unknown whether breathing high amounts of oxygen during exercise training leads to further benefits.

OBJECTIVES

Herein, we describe the design of the High Oxygen Delivery to Preserve Exercise Capacity in IPF Patients Treated with Nintedanib study (the HOPE-IPF study). The primary objective of this study is to determine the physiological and perceptual impact of breathing high levels of oxygen during exercise training in patients with IPF who are receiving antifibrotic therapy.

METHODS

HOPE-IPF is a two-arm double-blind multicenter randomized placebo-controlled trial of 88 patients with IPF treated with nintedanib. Patients will undergo 8 weeks of three times weekly aerobic cycle exercise training, breathing a hyperoxic gas mixture with a constant fraction of 60% inhaled oxygen, or breathing up to 40% oxygen as required to maintain an oxygen saturation level of at least 88%.

MEASUREMENTS AND MAIN RESULTS

End points will be assessed at baseline, postintervention (Week 8), and follow-up (Week 26). The primary analysis will compare the between-group baseline with post-training change in endurance time during constant work rate cycle exercise tests. Additional analyses will evaluate the impact of training with high oxygen delivery on 6-minute walk distance, dyspnea, physical activity, and quality of life.

CONCLUSIONS

The HOPE-IPF study will lead to a comprehensive understanding of IPF exercise physiology, with the potential to change clinical practice by indicating the need for increased delivery of supplemental oxygen during pulmonary rehabilitation in patients with IPF. Clinical trial registered with www.clinicaltrials.gov (NCT02551068).

Exertional dyspnoea in interstitial lung diseases: the clinical utility of cardiopulmonary exercise testing

Interstitial lung diseases (ILDs) represent a heterogeneous group of pathologies characterised by alveolar and interstitial damage, pulmonary inflammation (usually associated with fibrosis), decreased lung function and impaired gas exchange, which can be attributed to either a known or an unknown aetiology. Dyspnoea is one of the most common and disabling symptoms in patients with ILD, significantly impacting quality of life. The mechanisms causing dyspnoea are complex and not yet fully understood. However, it is recognised that dyspnoea occurs when there is an imbalance between the central respiratory efferent drive and the response of the respiratory musculature. The respiratory derangement observed in ILD patients at rest is even more evident during exercise. Pathophysiological mechanisms responsible for exertional dyspnoea and reduced exercise tolerance include altered respiratory mechanics, impaired gas exchange, cardiovascular abnormalities and peripheral muscle dysfunction.

This review describes the respiratory physiology of ILD, both at rest and during exercise, and aims to provide comprehensive and updated evidence on the clinical utility of the cardiopulmonary exercise test in the assessment and management of these pathological entities. In addition, the role of exercise training and pulmonary rehabilitation programmes in the ILD population is addressed.

Current best practice in rehabilitation in interstitial lung disease

Interstitial lung disease (ILD) is a group of chronic respiratory diseases characterized by dyspnoea on exertion and decline in health-related quality of life (HRQL). People with ILD experience significant exercise limitation with contributors that include ventilatory limitation, impaired gas exchange, decreased cardiac function and skeletal muscle dysfunction. Pulmonary rehabilitation (PR) is well established in patients with chronic obstructive pulmonary disease (COPD) as a means to overcome exercise limitation and improve activity-related dyspnoea. There is increasing evidence for similar effects of PR in people with ILD. This review discusses the evidence for PR in ILD, outlines the essential components of PR in this population, and highlights special considerations for exercise training in people with ILD. Possible future directions for PR research in people with ILD are explored.

Exercise-induced bronchoconstriction update-2016

The first practice parameter on exercise-induced bronchoconstriction (EIB) was published in 2010. This updated practice parameter was prepared 5 years later. In the ensuing years, there has been increased understanding of the pathogenesis of EIB and improved diagnosis of this disorder by using objective testing. At the time of this publication, observations included the following: dry powder mannitol for inhalation as a bronchial provocation test is FDA approved however not currently available in the United States; if baseline pulmonary function test results are normal to near normal (before and after bronchodilator) in a person with suspected EIB, then further testing should be performed by using standardized exercise challenge or eucapnic voluntary hyperpnea (EVH); and the efficacy of nonpharmaceutical interventions (omega-3 fatty acids) has been challenged. The workgroup preparing this practice parameter updated contemporary practice guidelines based on a current systematic literature review. The group obtained supplementary literature and consensus expert opinions when the published literature was insufficient. A search of the medical literature on PubMed was conducted, and search terms included pathogenesis, diagnosis, differential diagnosis, and therapy (both pharmaceutical and nonpharmaceutical) of exercise-induced bronchoconstriction or exercise-induced asthma (which is no longer a preferred term); asthma; and exercise and asthma. References assessed as relevant to the topic were evaluated to search for additional relevant references. Published clinical studies were appraised by category of evidence and used to document the strength of the recommendation. The parameter was then evaluated by Joint Task Force reviewers and then by reviewers assigned by the parent organizations, as well as the general membership. Based on this process, the parameter can be characterized as an evidence- and consensus-based document.

Combined pulmonary fibrosis and emphysema: effect of pulmonary rehabilitation in comparison with chronic obstructive pulmonary disease

OBJECTIVE

To evaluate the effectiveness of short-term comprehensive inpatient pulmonary rehabilitation for patients with combined pulmonary fibrosis and emphysema (CPFE), and to compare responses with those of patients with chronic obstructive pulmonary disease (COPD) who underwent an identical programme.

DESIGN

Retrospective analysis of several outcome measures.

SETTING

Pulmonary ward at a 358-bed community teaching hospital.

METHODS

3-week inpatient pulmonary rehabilitation programme assessed by pulmonary function tests, 6 min walk test and health-related quality of life (HRQL) using the Short Form-36 (SF-36).

RESULTS

17 patients with CPFE and 49 patients with COPD were referred to and completed the programme between March 2007 and February 2015. Age, sex, smoking status, body mass index and the Medical Research Council dyspnoea grade were comparable between groups. In the CPFE group, improvement from the start of the programme to the programme end was observed in forced expiratory volume in 1 s (FEV1) (from 1.7±0.4 to 1.8±0.4, p=0.034); however, there was no significant improvement in the 6 min walk test (distance, SpO2 nadir and Borg scale on exercise). With regard to HRQL, improvement was observed in physical function (p=0.015) whereas deterioration was observed in social functioning (p=0.044). In the COPD group, significant improvement was observed after the programme in the FEV1, 6 min walk test and 4 of the 8 SF-36 subscales. There was a significant difference in changes in the 6 min walk distance: -16.6±58.4 in CPFE versus 30.2±55.6 in COPD (p=0.009). In 2 domains, there was a significant difference in SF-36 scores between groups: Δvitality, -6.3±22.4 in CPFE versus 11.3±21.1 in COPD, p=0.009; and Δsocial functioning, -18.8±34.2 in CPFE versus 5.3±35.9 in COPD, p=0.027.

CONCLUSION

Patients with COPD derived greater benefits than those with CPFE, from the relatively short periods of inpatient pulmonary rehabilitation.

Pulmonary rehabilitation for interstitial lung disease

BACKGROUND

Interstitial lung disease (ILD) is characterised by reduced functional capacity, dyspnoea and exercise-induced hypoxia. Pulmonary rehabilitation, an intervention that includes exercise training, is beneficial for people with other chronic lung conditions; however its effects in ILD have not been well characterised.

OBJECTIVES

• To determine whether pulmonary rehabilitation in patients with ILD has beneficial effects on exercise capacity, symptoms, quality of life and survival compared with no pulmonary rehabilitation in patients with ILD.• To assess the safety of pulmonary rehabilitation in patients with ILD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 6), MEDLINE (Ovid), EMBASE (Ovid), the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EBSCO) and the Physiotherapy Evidence Database (PEDro) (all searched from inception to June 2014). We also searched the reference lists of relevant studies, international clinical trial registries and respiratory conference abstracts to look for qualifying studies.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials in which pulmonary rehabilitation was compared with no pulmonary rehabilitation or with other therapy in people with ILD of any origin were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data and assessed risk of bias. Study authors were contacted to provide missing data and information regarding adverse effects. A priori subgroup analyses were specified for participants with idiopathic pulmonary fibrosis (IPF) and participants with severe lung disease (low diffusing capacity or desaturation during exercise). We planned to subgroup according to training modality applied, but there were insufficient data.

MAIN RESULTS

Nine studies were included, six of which were published as abstracts. Five studies were included in the meta-analysis (86 participants who undertook pulmonary rehabilitation and 82 control participants). One study used a blinded assessor and intention-to-treat analysis. No adverse effects of pulmonary rehabilitation were reported. Pulmonary rehabilitation improved the six-minute walk distance with weighted mean difference (WMD) of 44.34 metres (95% confidence interval (CI) 26.04 to 62.64 metres) and improved oxygen consumption (VO2) peak with WMD of 1.24 mL/kg/min(-1) (95% CI 0.46 to 2.03 mL/kg/min(-1)). Improvements in six-minute walk distance and VO2 peak were also seen in the subgroup of participants with idiopathic pulmonary fibrosis (IPF) (WMD 35.63 metres, 95% CI 16.02 to 55.23 metres; WMD 1.46 mL/kg/min(-1), 95% CI 0.54 to 2.39 mL/kg/min(-1), respectively). Reduced dyspnoea (standardised mean difference (SMD) -0.66, 95% CI -1.05 to -0.28) following pulmonary rehabilitation was also seen in the IPF subgroup (SMD -0.68, 95% CI -1.12 to -0.25). Quality of life improved following pulmonary rehabilitation for all participants on a variety of measures (SMD 0.59, 95% CI 0.20 to 0.98) and for the subgroup of people with IPF (SMD 0.59, 95% CI 0.14 to 1.03). Two studies reported longer-term outcomes, with no significant effects of pulmonary rehabilitation on clinical variables or survival at three or six months. Available data were insufficient to allow examination of the impact of disease severity or exercise training modality.

AUTHORS' CONCLUSIONS

Pulmonary rehabilitation seems to be safe for people with ILD. Improvements in functional exercise capacity, dyspnoea and quality of life are seen immediately following pulmonary rehabilitation, with benefits also evident in IPF. Because of inadequate reporting of methods and small numbers of included participants, the quality of evidence was low to moderate. Little evidence was available regarding longer-term effects of pulmonary rehabilitation.

Factors limiting exercise tolerance in chronic lung diseases

The major limitation to exercise performance in patients with chronic lung diseases is an issue of great importance since identifying the factors that prevent these patients from carrying out activities of daily living provides an important perspective for the choice of the appropriate therapeutic strategy. The factors that limit exercise capacity may be different in patients with different disease entities (i.e., chronic obstructive, restrictive or pulmonary vascular lung disease) or disease severity and ultimately depend on the degree of malfunction or miss coordination between the different physiological systems (i.e., respiratory, cardiovascular and peripheral muscles). This review focuses on patients with chronic obstructive pulmonary disease (COPD), interstitial lung disease (ILD) and pulmonary vascular disease (PVD). ILD and PVD are included because there is sufficient experimental evidence for the factors that limit exercise capacity and because these disorders are representative of restrictive and pulmonary vascular disorders, respectively. A great deal of emphasis is given, however, to causes of exercise intolerance in COPD mainly because of the plethora of research findings that have been published in this area and also because exercise intolerance in COPD has been used as a model for understanding the interactions of different pathophysiologic mechanisms in exercise limitation. As exercise intolerance in COPD is recognized as being multifactorial, the impacts of the following factors on patients' exercise capacity are explored from an integrative physiological perspective: (i) imbalance between the ventilatory capacity and requirement; (ii) imbalance between energy demands and supplies to working respiratory and peripheral muscles; and (iii) peripheral muscle intrinsic dysfunction/weakness.

Gas exchange in disease: asthma, chronic obstructive pulmonary disease, cystic fibrosis, and interstitial lung disease

Ventilation-perfusion (VA/Q) inequality is the underlying abnormality determining hypoxemia and hypercapnia in lung diseases. Hypoxemia in asthma is characterized by the presence of low VA/Q units, which persist despite improvement in airway function after an attack. This hypoxemia is generally attenuated by compensatory redistribution of blood flow mediated by hypoxic vasoconstriction and changes in cardiac output, however, mediator release and bronchodilator therapy may cause deterioration. Patients with chronic obstructive pulmonary disease have more complex patterns of VA/Q inequality, which appear more fixed, and changes in blood flow and ventilation have less benefit in improving gas exchange efficiency. The inability of ventilation to match increasing cardiac output limits exercise capacity as the disease progresses. Deteriorating hypoxemia during exacerbations reflects the falling mixed venous oxygen tension from increased respiratory muscle activity, which is not compensated by any redistribution of VA/Q ratios. Shunt is not a feature of any of these diseases. Patients with cystic fibrosis (CF) have no substantial shunt when managed according to modern treatment regimens. Interstitial lung diseases demonstrate impaired oxygen diffusion across the alveolar-capillary barrier, particularly during exercise, although VA/Q inequality still accounts for most of the gas exchange abnormality. Hypoxemia may limit exercise capacity in these diseases and in CF. Persistent hypercapnic respiratory failure is a feature of advancing chronic obstructive pulmonary disease and CF, closely associated with sleep disordered breathing, which is not a prominent feature of the other diseases. Better understanding of the mechanisms of hypercapnic respiratory failure, and of the detailed mechanisms controlling the distribution of ventilation and blood flow in the lung, are high priorities for future research.

The benefits of exercise training in interstitial lung disease: protocol for a multicentre randomised controlled trial

Background

Interstitial lung disease encompasses a diverse group of chronic lung conditions characterised by distressing dyspnoea, fatigue, reduced exercise tolerance and poor health-related quality of life. Exercise training is one of the few treatments to induce positive changes in exercise tolerance and symptoms, however there is marked variability in response. The aetiology and severity of interstitial lung disease may influence the response to treatment. The aims of this project are to establish the impact of exercise training across the range of disease severity and to identify whether there is an optimal time for patients with interstitial lung disease to receive exercise training.

Methods/Design

One hundred and sixteen participants with interstitial lung disease recruited from three tertiary institutions will be randomised to either an exercise training group (supervised exercise training twice weekly for eight weeks) or a usual care group (weekly telephone support). The 6-minute walk distance, peripheral muscle strength, health-related quality of life, dyspnoea, anxiety and depression will be measured by a blinded assessor at baseline, immediately following the intervention and at six months following the intervention. The primary outcome will be change in 6-minute walk distance following the intervention, with planned subgroup analyses for participants with idiopathic pulmonary fibrosis, dust-related interstitial lung disease and connective-tissue related interstitial lung disease. The effects of disease severity on outcomes will be evaluated using important markers of disease severity and survival, such as forced vital capacity, carbon monoxide transfer factor and pulmonary hypertension.

Discussion

This trial will provide certainty regarding the role of exercise training in interstitial lung disease and will identify at what time point within the disease process this treatment is most effective. The results from this study will inform and optimise the clinical management of people with interstitial lung disease.

Trial registration

Australian New Zealand Clinical Trials Registry ACTRN12611000416998

Impaired exercise performance in systemic sclerosis and its clinical correlations

OBJECTIVES

To investigate the prevalence of impaired exercise performance as assessed by a standardized cardiopulmonary exercise test (CPET) in systemic sclerosis (SSc) and to identify the associated disease features.

METHODS

Forty-six SSc patients were enrolled and evaluated for clinical and serological SSc subset, extent of skin and internal organ involvement, and disease activity and severity. Exercise performance was subsequently evaluated in these patients and in 23 healthy individuals matched for sex and age, using a standardized CPET.

RESULTS

Exercise performance, measured by maximum oxygen uptake (VO2 max < 80% of predicted value), was found to be impaired in 43/46 patients. Stepwise regression analysis showed that VO2 max adjusted for body weight VO2 max/kg) was independently correlated with the severity of heart (p = 0.001) and lung (p = 0.013) involvement, left ventricular diastolic dysfunction (p = 0.009), and the Health Assessment Questionnaire Disability Index (HAQ-DI) score (p = 0.016).

CONCLUSIONS

This study demonstrates that physical disability contributes significantly to the development of impaired exercise performance in SSc patients. Cardiopulmonary exercise testing may be included among the battery of tests used to determine the severity of SSc.

Acidosis and raised norepinephrine levels are associated with exercise dyspnoea in idiopathic pulmonary fibrosis

BACKGROUND AND OBJECTIVE

Exertional dyspnoea limits patients with IPF in their activities of daily living. The mechanism, however, has not been elucidated. This study tested the hypothesis in IPF that exertional dyspnoea correlates with cardiopulmonary exercise responses, specifically changes in arterial blood pH and plasma norepinephrine (NE).

METHODS

Cardiopulmonary exercise testing with measurements of dyspnoea (Borg scale), plasma NE, plasma lactate and arterial blood gases were performed in 29 patients with IPF and in nine controls.

RESULTS

Both groups showed obvious break points in dyspnoea changes during exercise. In IPF, an abrupt change in the Borg scale, pH, PaCO(2) and plasma NE occurred in the late exercise phase after the 'break point'. Compared with controls, patients with IPF had significantly higher HCO(3)(-) levels and physiologic dead space/tidal volume during exercise. In IPF, during both exercise phases, the dyspnoea slope (DeltaBorg scale/Deltaminute ventilation) correlated with the pH slope (DeltapH/Deltaoxygen uptake) (before the break point: r = -0.537, P = 0.0022; r = -0.886, P < 0.0001, after the break point) and the NE slope (DeltaNE/Deltaoxygen uptake) (before the break point: r = 0.481, P = 0.0075; R = 0.784, P < 0.0001, after the break point).

CONCLUSIONS

In patients with IPF, exercise-induced acidosis and increases in circulating NE levels were associated with intensity of exertional dyspnoea.

Imitators of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is described by transient narrowing of the airways after exercise. It occurs in approximately 10% of the general population, while athletes may show a higher prevalence, especially in cold weather and ice rink athletes. Diagnosis of EIB is often made on the basis of self-reported symptoms without objective lung function tests, however, the presence of EIB can not be accurately determined on the basis of symptoms and may be under-, over-, or misdiagnosed. The goal of this review is to describe other clinical entities that mimic asthma or EIB symptoms and can be confused with EIB.

Review series: Rehabilitation in non COPD: Mechanisms of exercise limitation and pulmonary rehabilitation for patients with pulmonary fibrosis/restrictive lung disease

The standard of care in the treatment of chronic lung disease includes pulmonary rehabilitation (PR). While evidence of the effectiveness of PR in chronic obstructive lung disease (COPD) is robust, that for pulmonary fibrosis and other non-fibrotic restrictive lung diseases is less extensive. However, PR has been shown to improve functional exercise capacity and health-related quality of life in non-COPD patients, primarily those with interstitial lung diseases. This review examines mechanisms of exercise limitation in non-COPD patients and discusses how they might affect both the application of and outcome measures of PR. We also review the assessment of exercise performance, dyspnea, and quality of life as well as special protocols, safety considerations, and special techniques in PR as applied to patients with pulmonary fibrosis or restrictive lung disease. At present, there are no evidence-based guidelines for PR in non-COPD patients whereas PR is firmly recommended in COPD management. More research is needed to strengthen the evidence for the use of PR in non-COPD patients. Meanwhile, the available data, summarized in this review, support the inclusion of PR in the management of all patients with chronic lung disease including pulmonary fibrosis and restrictive lung disease.

Physical training for interstitial lung disease

BACKGROUND

Interstitial lung disease (ILD) is characterised by reduced functional capacity, dyspnoea and exercise-induced hypoxia. Physical training is beneficial for people with other chronic lung conditions, however its effects in ILD have not been well characterised.

OBJECTIVES

To assess the effects of physical training on exercise capacity, symptoms, quality of life and survival compared to no physical training in people with ILD.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (The Cochrane Library 2007, Issue 4), MEDLINE, EMBASE, CINAHL and the Physiotherapy Evidence Database (PEDro) (all searched from inception to December 2007). The reference lists of relevant studies were hand-searched for qualifying studies.

SELECTION CRITERIA

Randomised or quasi-randomised controlled trials in which physical training was compared to no physical training or to other therapy in people with ILD of any aetiology were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data and assessed risk of bias. Authors were contacted to obtain missing data and information regarding adverse effects. A priori subgroup analyses were specified for participants with idiopathic pulmonary fibrosis (IPF), severe lung disease and training modality.

MAIN RESULTS

Five studies were included, three of which were published as abstracts. Two studies were included in the meta-analysis (43 participants who undertook physical training and 42 control participants). One study used a blinded assessor and intention-to-treat analysis. No adverse effects of physical training were reported. Physical training improved the 6-minute walk distance with weighted mean difference (WMD) 38.61 metres (95% confidence interval 15.37 to 61.85 metres). Improvement in 6-minute walk distance was also seen in the subgroup of participants with IPF (WMD 26.55 metres, 2.81 to 50.30 metres). No effect of physical training on VO(2)peak was evident. There was a reduction in dyspnoea (standardised mean difference (SMD) -0.47, 95% CI: -0.91 to -0.04) however this did not reach significance in the IPF subgroup (SMD -0.43, 95% CI: -0.94 to 0.08). Quality of life improved following physical training in all participants (SMD 0.58, 95% CI: 0.15 to 1.02) and in IPF (SMD 0.57, 95% CI: 0.06 to 1.09). Only one study reported longer-term outcomes, with no significant effects of physical training on clinical variables or survival at six months. Insufficient data were available to examine the impact of disease severity or training modality.

AUTHORS' CONCLUSIONS

Physical training is safe for people with ILD. Improvements in functional exercise capacity, dyspnoea and quality of life are seen immediately following training, with benefits also evident in IPF. There is little evidence regarding longer-term effects of physical training.

Role of arterial hypoxemia and pulmonary mechanics in exercise limitation in adults with cystic fibrosis

We tested the hypothesis that maximal exercise performance in adults with cystic fibrosis is limited by arterial hypoxemia. In study 1, patients completed two maximal exercise tests, a control and a test with 400 ml of added dead space. Maximal O2 consumption was significantly lower in the added dead space study vs. control (1.04 ± 0.15 vs. 1.20 ± 0.11 l/min; P < 0.05), with no difference in peak ventilation. There was significant O2 desaturation during exercise that was equal in both control and added dead space studies. The decrease in maximal O2 consumption with added dead space suggests that maximal exercise in cystic fibrosis is limited by respiratory factors. We subsequently examined whether pulmonary mechanics or arterial hypoxemia limits maximal exercise performance. In study 2, patients completed two maximal exercise tests, a control and a test with 400 ml of added dead space while also breathing 38% O2. Added dead space was used to overcome the suppressive effects of hyperoxia on minute ventilation. Maximal O2 consumption was significantly higher with added dead space and 38% O2 vs. control (1.62 ± 0.16 vs. 1.43 ± 0.14 l/min; P < 0.05). Peak ventilation and O2 saturation were significantly greater in the added dead space and 38% O2 test vs. control. The increase in maximal O2 consumption and peak ventilation with added dead space and 38% O2 suggests that maximal exercise in cystic fibrosis is limited by arterial hypoxemia.

Quadriceps weakness is related to exercise capacity in idiopathic pulmonary fibrosis

STUDY OBJECTIVE

In COPD, it has been shown that peripheral muscle dysfunction is a factor determining exercise intolerance. We examined the hypothesis that exercise capacity of patients with idiopathic pulmonary fibrosis (IPF) is, at least in part, determined by peripheral muscle dysfunction.

METHODS

Maximum oxygen uptake (V(O2)max) was evaluated in 41 consecutive patients with IPF, along with potential determinants of exercise capacity, both in the lungs and in the peripheral muscles.

RESULTS

Patients had reduced V(O2)max (893 +/- 314 mL, 46.0% predicted) and reduced quadriceps force (QF) [65% predicted]. Significant correlates of V(O2)max reduction were vital capacity (VC) [r = 0.79], total lung capacity (r = 0.64), diffusion capacity (r = 0.64), QF (r = 0.62), maximum expiratory pressure (r = 0.48), and Pa(O2) at rest (r = 0.33). In stepwise multiple regression analysis, VC and QF were independent predictors of V(O2)max. Furthermore, in subgroup analysis, QF was a significant contributing factor for V(O2)max in patients who discontinued exercise because of dyspnea and/or leg fatigue.

CONCLUSIONS

We conclude that QF is a predictor of exercise capacity in IPF. Measures that improve muscle function might improve exercise tolerance.

The shuttle walk exercise test in idiopathic pulmonary fibrosis

The shuttle walk test (SWT) is a validated, incremental walking test for chronic obstructive pulmonary disease, but not for idiopathic pulmonary fibrosis (IPF). The measurement of maximal oxygen consumption (VO2 max) is considered to be the gold standard measurement of functional capacity. This study examines the relationship between IPF patients' performance on the SWT and VO2 max. Twenty patients were recruited for the study, which consisted of two separate experiments. Firstly, the relationship between SWT performance on a conventional corridor SWT, with that on a programmable treadmill SWT designed to reproduce the corridor SWT was examined (n=10). In the second experiment, the relationship between performance on the treadmill equivalent SWT and VO2 max measurements was studied (n=10). There was a significant correlation between distance walked on the corridor SWT, and that walked on the treadmill equivalent SWT without VO2 max measurements (367 m vs. 410 m) (r=0.91, P=0.0003). There was a significant correlation between distance walked on the treadmill equivalent SWT (277 m), and the directly determined VO2 max (14.87 ml/kg/min) (r=0.74, P=0.01). During both experiments, a significant correlation was also observed between baseline PaO2 and SWT performance, and between DLCO and SWT performance. The shuttle walk test is a simple objective measure of functional capacity in IPF patients, which should facilitate the evaluation of new therapeutic compounds for IPF.

Impairments and prognostic factors for survival in patients with idiopathic pulmonary fibrosis

The aim of the present study was to evaluate exercise limiting factors using cardiopulmonary exercise testing (CPET) in patients with idiopathic pulmonary fibrosis (IPF), and to investigate whether these parameters are related to survival after CPET. We evaluated 41 patients with IPF (mean 68.2 years, 27 male) who performed CPET. The exercise capacity in patients with IPF was limited more strongly by gas exchange and/or ventilatory impairments, compared with cardiac impairment. Using univariate analysis, the severity of exercise-induced hypoxemia (EIH) evaluated by deltaPaO2/deltaVO2 (PaO2-slope), oxygen uptake at maximum exercise, oxygen pulse at maximum exercise, ventilatory equivalent for carbon dioxide at maximum exercise and age were significantly related to the survival rate. Interestingly, the PaO2-slope was most closely correlated with the survival rate using multiple analysis with a stepwise evaluation. Nevertheless, PaO2 at rest and at maximum exercise were not factors influencing survival. In patients with IPF, CPET can simultaneously evaluate the ability of both the cardiovascular and respiratory systems, and should be available so that parameters can be derived to make the necessary prognostic estimations, with the most useful parameter being the degree of EIH as represented by the PaO2-slope.

Radiographic (ILO) readings predict arterial oxygen desaturation during exercise in subjects with asbestosis

BACKGROUND

Exercise impairment is common in subjects with asbestosis. Arterial oxygen desaturation during exercise is an important contributor to exercise limitation. The International Labour Office (ILO) classification of plain chest radiographs correlates with resting pulmonary function, but its value in predicting abnormal ventilatory responses to exercise, including desaturation, has not been explored.

AIMS

To determine in subjects with asbestosis (1) if radiographic profusion scores and the extent of small irregular shadows on plain chest radiographs correlate with resting lung function and abnormal ventilatory responses to exercise; and (2) if radiographic scores add value to resting lung function tests in predicting abnormal ventilatory responses to exercise.

METHODS

Thirty eight male subjects with asbestosis were included. Plain chest radiographs were read according to the ILO classification independently by three observers. All subjects underwent assessment of lung function and an incremental exercise test.

RESULTS

Profusion scores and number of affected zones correlated significantly with the percentage predicted values of single breath diffusing capacity (DLCO), forced vital capacity (FVC), and total lung capacity (TLC). Arterial oxygen desaturation occurred in 29% of the subjects. The severity of desaturation correlated significantly with profusion and the number of affected zones. The combined use of number of affected zones, FEV(1)/FVC ratio and DLCO predicted desaturation during exercise with an explained variance of 41%. VO(2)max was significantly related only to DLCO but was not predicted by the ILO score.

CONCLUSION

Arterial oxygen desaturation correlated with the profusion and extent of parenchymal abnormality on chest radiographs. The addition of morphological indices to physiological measurements is valuable for predicting oxygen desaturation during exercise but not for VO(2)max. Refinement of the radiographic scoring system and the addition of more sophisticated imaging techniques may further improve the predictive power.

External thoracic restriction, respiratory sensation, and ventilation during exercise in men

Multiple factors may contribute to the dyspnea associated with restrictive ventilatory disease (RVD). Simple models that examine specific features of this problem are likely to provide insight into the mechanisms. Previous models of RVD utilizing elastic loads may not represent completely the impact on pulmonary and chest wall receptors derived from breathing at low thoracic volumes. The purpose of this study was to investigate the sensory consequences of breathing at low lung volumes induced by external thoracic restriction in an attempt to further elucidate the etiology of dyspnea in this setting. Ten men were studied, with and without an inelastic corset applied at residual volume (restriction resulted in mean reductions in vital capacity, functional residual capacity, residual volume, and forced expired volume in 1 s of 44, 31, 12.5, and 42%, respectively). During 10-min steady-state exercise tests (at a workload set to achieve approximately 65% maximum heart rate), restriction resulted in significant increases, compared with control, in minute ventilation (61 vs. 49 l/min), respiratory frequency (43 vs. 23 breaths/min), and visual analog scale measurements of respiratory discomfort (65 vs. 20 mm). Alveolar hyperventilation (end-tidal PCO2 = 39 vs. 44 Torr for control) and mild O2 desaturation (arterial blood O2 saturation = 93 vs. 95% for control) occurred. Hypoxemia, atelectasis, increased work and effort of breathing, or a decrease in the volume-related feedback from chest wall and/or lungs could be responsible for the increased dyspnea reported. External thoracic restriction provides a useful model to study mechanisms of dyspnea in RVD.

Mechanical ventilatory constraints in aging, lung disease, and obesity: perspectives and brief review

Mechanical ventilatory constraints in aging, lung disease, and obesity; perspectives and brief review. Med. Sci. Sports Exerc., Vol. 31, No. 1 (Suppl.), pp. S12-S22, 1999. One of the most difficult tasks of cardiopulmonary exercise testing is to determine the influence of ventilatory limitations on the ventilatory response to exercise. Currently there is no generally accepted method in which to quantify the magnitude of mechanical ventilatory constraints during exercise. Nor is there agreement on how to quantify maximal ventilatory capacity. To address these issues, this article focuses on the evaluation of mechanical ventilatory constraints during exercise and provides an overview of the mechanical ventilatory constraints that are encountered with aging, lung disease, and obesity.