Pulmonary exercise testing predicts prognosis in patients with chronic obstructive pulmonary disease

Prevalence and prognostic importance of exercise limitation and physical inactivity in COPD

Exercise limitation and physical inactivity are separate, but related constructs. Both are commonly present in individuals with COPD, contribute to disease burden over and above the respiratory impairments, and are independently predictive of adverse outcomes. Because of this, clinicians should consider assessing these variables in their patients with COPD. Field tests of exercise performance such as the 6-min walk test and the incremental and endurance shuttle walk tests require limited additional resources, and results correlate with negative outcomes. Laboratory measures of exercise performance using a treadmill or cycle ergometer assess exercise capacity, provide prognostic information and have the advantage of explaining physiological mechanisms (and their interactions) underpinning exercise limitation. Limitations in exercise capacity (i.e. "cannot do") and physical inactivity (i.e. "do not do") are both associated with mortality; exercise limitation appears to be the more important driver of this outcome.

The six-minute walk test - a reliable test for detection of exercise-related desaturation in patients with chronic obstructive pulmonary disease

INTRODUCTION

Exercise-induced desaturation is common in patients with moderate to severe chronic obstructive pulmonary disease (COPD). It provides additional information about physical capacity and disease evolution, and it is an important predictor of mortality.

Value of Cardiopulmonary Exercise Testing in the Prognosis Assessment of Chronic Obstructive Pulmonary Disease Patients: A Retrospective, Multicentre Cohort Study

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases associated with high mortality. Previous studies suggested a prognostic role for peak oxygen uptake (VO2peak) assessed during cardiopulmonary exercise testing (CPET) in patients with COPD. However, most of these studies had small sample sizes or short follow-up periods, and despite their relevance, CPET parameters are not included in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) tool for assessment of severity.

OBJECTIVES

We therefore aimed to assess the prognostic value of CPET parameters in a large cohort of outpatients with COPD.

METHODS

In this retrospective, multicentre cohort study, medical records of patients with COPD who underwent CPET during 2004-2017 were reviewed and demographics, smoking habits, GOLD grade and category, exacerbation frequency, dyspnoea score, lung function measurements, and CPET parameters were documented. Relationships with survival were evaluated using Kaplan-Meier analysis, Cox regression, and receiver operating characteristic (ROC) curves.

RESULTS

Of a total of 347 patients, 312 patients were included. Five-year and 10-year survival probability was 75% and 57%, respectively. VO2peak significantly predicted survival (hazard ratio: 0.886 [95% confidence interval: 0.830; 0.946]). The optimal VO2peak threshold for discrimination of 5-year survival was 14.6 mL/kg/min (area under ROC curve: 0.713). Five-year survival in patients with VO2peak <14.6 mL/kg/min versus ≥ 14.6 mL/kg/min was 60% versus 86% in GOLD categories A/B and 64% versus 90% in GOLD categories C/D.

CONCLUSIONS

We confirm that VO2peak is a highly significant predictor of survival in COPD patients and recommend the incorporation of VO2peak into the assessment of COPD severity.

Dynamic Metabolic Risk Profiling of World Trade Center Lung Disease: A Longitudinal Cohort Study

Rationale: Metabolic syndrome (MetSyn) increases the risk of World Trade Center (WTC) lung injury (LI). However, the temporal relationship of MetSyn, exposure intensity, and lung dysfunction is not well understood. Objective: To model the association of longitudinal MetSyn characteristics with WTC lung disease to define modifiable risk. Methods: Firefighters, for whom consent was obtained (N = 5,738), were active duty on September 11, 2001 (9/11). WTC-LI (n = 1,475; FEV₁% predicted <lower limit of normal [LLN]) and non-WTC-LI (n = 4,263; FEV₁% predicted ⩾LLN at all exams) was the primary outcome, and FVC% predicted <LLN and FEV₁/FVC <0.70 were secondary outcomes. We assessed 1) the effect of concurrent MetSyn on longitudinal lung function by linear mixed models, 2) the temporal effect of MetSyn and exposure by Weibull proportional hazards, 3) the effects of MetSyn's rate of change by two-stage models, and 4) the nonlinear joint effect of longitudinal MetSyn components by a partially linear single-index model (PLSI). Measurements and Main Results: WTC-LI cases were more often ever-smokers, arrived in the morning (9/11), and had MetSyn. Body mass index ⩾30 kg/m² and high-density lipoprotein <40 mg/dl were most contributory to concurrent loss of FEV₁% predicted and FVC% predicted while conserving FEV₁/FVC. Body mass index ⩾30 kg/m² and dyslipidemia significantly predicted WTC-LI, FVC% predicted <LLN in a Weibull proportional hazards model. Dynamic risk assessment of WTC-LI on the basis of MetSyn and exposure showed how reduction of MetSyn factors further reduces WTC-LI likelihood in susceptible populations. PLSI demonstrates that MetSyn has a nonlinear relationship with WTC lung disease, and increases in cumulative MetSyn risk factors exponentially increase WTC-LI risk. An interactive metabolic-risk modeling application was developed to simplify PLSI interpretation. Conclusions: MetSyn and WTC exposure contribute to the development of lung disease. Dynamic risk assessment may be used to encourage treatment of MetSyn in susceptible populations. Future studies will focus on dietary intervention as a disease modifier.

Exertional Desaturation Has Higher Mortality Than Non-Desaturation in COPD

Background and objectives: Exertional desaturation (ED) is often overlooked in chronic obstructive pulmonary disease (COPD). We aim to investigate the impact of ED on mortality and the predictors of ED in COPD. Materials andmethods: A cohort of COPD patients with clinically stable, widely ranging severities were enrolled. ED is defined as oxyhemoglobin saturation by pulse oximetry (SpO2) < 90% or a drop of ΔSpO2 ≥ 4% during a six-minute walk test (6MWT). Cox regression analysis is used to estimate the hazard ratio (HR) for three-year mortality. Results: A total of 113 patients were studied, including ED (N = 34) and non-ED (N = 79) groups. FVC (% of predicted value), FEV1/FVC (%), FEV1 (% of predicted value), DLCO (%), maximal inspiratory pressure, SpO2 during the 6MWT, GOLD stage, and COPD severity were significantly different between the ED and non-ED groups in univariate analysis. Low minimal SpO2 (p < 0.001) and high maximal heart rate (p = 0.04) during the 6MWT were significantly related to ED in multivariate analysis. After adjusting for age, gender, body mass index, 6MWD, FEV1, mMRC, GOLD staging, exacerbation, hs-CRP, and fibrinogen, the mortality rate of the ED group was higher than that of the non-ED group (p = 0.012; HR = 4.12; 95% CI 1.37–12.39). For deaths, the average survival time of ED was shorter than that of the non-ED group (856.4 days vs. 933.8 days, p = 0.033). Conclusions: ED has higher mortality than non-ED in COPD. COPD should be assessed for ED, especially in patients with low minimal SpO2 and high maximal HR during the 6MWT.

Dietary phenotype and advanced glycation end-products predict WTC-obstructive airways disease: a longitudinal observational study

BACKGROUND

Diet is a modifier of metabolic syndrome which in turn is associated with World Trade Center obstructive airways disease (WTC-OAD). We have designed this study to (1) assess the dietary phenotype (food types, physical activity, and dietary habits) of the Fire Department of New York (FDNY) WTC-Health Program (WTC-HP) cohort and (2) quantify the association of dietary quality and its advanced glycation end product (AGE) content with the development of WTC-OAD.

METHODS

WTC-OAD, defined as developing WTC-Lung Injury (WTC-LI; FEV1 < LLN) and/or airway hyperreactivity (AHR; positive methacholine and/or positive bronchodilator response). Rapid Eating and Activity Assessment for Participants-Short Version (REAP-S) deployed on 3/1/2018 in the WTC-HP annual monitoring assessment. Clinical and REAP-S data of consented subjects was extracted (7/17/2019). Diet quality [low-(15-19), moderate-(20-29), and high-(30-39)] and AGE content per REAP-S questionnaire were assessed for association with WTC-OAD. Regression models adjusted for smoking, hyperglycemia, hypertension, age on 9/11, WTC-exposure, BMI, and job description.

RESULTS

N = 9508 completed the annual questionnaire, while N = 4015 completed REAP-S and had spirometry. WTC-OAD developed in N = 921, while N = 3094 never developed WTC-OAD. Low- and moderate-dietary quality, eating more (processed meats, fried foods, sugary drinks), fewer (vegetables, whole-grains),and having a diet abundant in AGEs were significantly associated with WTC-OAD. Smoking was not a significant risk factor of WTC-OAD.

CONCLUSIONS

REAP-S was successfully implemented in the FDNY WTC-HP monitoring questionnaire and produced valuable dietary phenotyping. Our observational study has identified low dietary quality and AGE abundant dietary habits as risk factors for pulmonary disease in the context of WTC-exposure. Dietary phenotyping, not only focuses our metabolomic/biomarker profiling but also further informs future dietary interventions that may positively impact particulate matter associated lung disease.

Cardiopulmonary exercise testing in chronic obstructive pulmonary disease: An update on its clinical value and applications

Chronic obstructive pulmonary disease is a debilitating disorder, characterized by airflow limitation, exercise impairment, reduced functional capacity and significant systemic comorbidity, which complicates the course of the disease. The critical inspiratory constraint to tidal volume expansion during exercise (that may be further complicated by the presence of dynamic hyperinflation), abnormalities in oxygen transportation and gas exchange abnormalities are the major pathophysiological mechanisms of exercise intolerance in COPD patients, and thus, exercise testing has been traditionally used for the functional evaluation of these patients. Compared to various laboratory and field exercise tests, cardiopulmonary exercise testing (CPET) provides a thorough assessment of exercise physiology, involving the integrative respiratory, cardiovascular, muscle and metabolic responses to exercise. This review highlights the clinical utility of CPET in COPD patients, as it provides important information for the determination of the major factors that limit exercise among patients with several comorbidities, allows the assessment of the severity of dynamic hyperinflation, provides valuable prognostic information and can be used to evaluate the response to several therapeutic interventions.

The key questions in rehabilitation in thoracic surgery

Enhancing the recovery of patients undergoing Thoracic Surgery is the raison d'être of a pulmonary rehabilitation (PR) process. Benefits of a PR program have been shown to include reduced postoperative complications, hospital length of stay (LOS) and improved exercise and lung function parameters. Identifying which groups of patients benefit most and the constituency of the perfect PR program is subject to ongoing research. Providing PR to patients in a manner acceptable to their lifestyle and disease timeline within economic limitations is the challenge.

Highs and lows of hyperoxia: physiological, performance, and clinical aspects

Molecular oxygen (O₂) is a vital element in human survival and plays a major role in a diverse range of biological and physiological processes. Although normobaric hyperoxia can increase arterial oxygen content ([Formula: see text]), it also causes vasoconstriction and hence reduces O₂ delivery in various vascular beds, including the heart, skeletal muscle, and brain. Thus, a seemingly paradoxical situation exists in which the administration of oxygen may place tissues at increased risk of hypoxic stress. Nevertheless, with various degrees of effectiveness, and not without consequences, supplemental oxygen is used clinically in an attempt to correct tissue hypoxia (e.g., brain ischemia, traumatic brain injury, carbon monoxide poisoning, etc.) and chronic hypoxemia (e.g., severe COPD, etc.) and to help with wound healing, necrosis, or reperfusion injuries (e.g., compromised grafts). Hyperoxia has also been used liberally by athletes in a belief that it offers performance-enhancing benefits; such benefits also extend to hypoxemic patients both at rest and during rehabilitation. This review aims to provide a comprehensive overview of the effects of hyperoxia in humans from the "bench to bedside." The first section will focus on the basic physiological principles of partial pressure of arterial O₂, [Formula: see text], and barometric pressure and how these changes lead to variation in regional O₂ delivery. This review provides an overview of the evidence for and against the use of hyperoxia as an aid to enhance physical performance. The final section addresses pathophysiological concepts, clinical studies, and implications for therapy. The potential of O₂ toxicity and future research directions are also considered.

Diagnosis, assessment, and phenotyping of COPD: beyond FEV₁

COPD is now widely recognized as a complex heterogeneous syndrome, having both pulmonary and extrapulmonary features. In clinical practice, the diagnosis of COPD is based on the presence of chronic airflow limitation, as assessed by post-bronchodilator spirometry. The severity of the airflow limitation, as measured by percent predicted FEV1, provides important information to the physician to enable optimization of management. However, in order to accurately assess the complexity of COPD, there need to be other measures made beyond FEV1. At present, there is a lack of reliable and simple blood biomarkers to confirm and further assess the diagnosis of COPD. However, it is possible to identify patients who display different phenotypic characteristics of COPD that relate to clinically relevant outcomes. Currently, validated phenotypes of COPD include alpha-1 antitrypsin deficiency, and "frequent exacerbators". Recently, a definition and assessment of a new phenotype comprising patients with overlapping features of asthma and COPD has been suggested and is known as "asthma COPD overlap syndrome". Several other phenotypes have been proposed, but require validation against clinical outcomes. Defining phenotypes requires the assessment of multiple factors indicating disease severity, its impact, and its activity. Recognition and validation of COPD phenotypes has an important role to play in the selection of evidence-based targeted therapy in the future management of COPD, but regardless of the diagnostic terms, patients with COPD should be assessed and treated according to their individual treatable characteristics.

Use of exercise testing in the evaluation of interventional efficacy: an official ERS statement

This document reviews 1) the measurement properties of commonly used exercise tests in patients with chronic respiratory diseases and 2) published studies on their utilty and/or evaluation obtained from MEDLINE and Cochrane Library searches between 1990 and March 2015.

Exercise tests are reliable and consistently responsive to rehabilitative and pharmacological interventions. Thresholds for clinically important changes in performance are available for several tests. In pulmonary arterial hypertension, the 6-min walk test (6MWT), peak oxygen uptake and ventilation/carbon dioxide output indices appear to be the variables most responsive to vasodilators. While bronchodilators do not always show clinically relevant effects in chronic obstructive pulmonary disease, high-intensity constant work-rate (endurance) tests (CWRET) are considerably more responsive than incremental exercise tests and 6MWTs. High-intensity CWRETs need to be standardised to reduce interindividual variability. Additional physiological information and responsiveness can be obtained from isotime measurements, particularly of inspiratory capacity and dyspnoea. Less evidence is available for the endurance shuttle walk test. Although the incremental shuttle walk test and 6MWT are reliable and less expensive than cardiopulmonary exercise testing, two repetitions are needed at baseline. All exercise tests are safe when recommended precautions are followed, with evidence suggesting that no test is safer than others.

Systematic Review of the Association Between Laboratory- and Field-Based Exercise Tests and Lung Function in Patients with Chronic Obstructive Pulmonary Disease

Introduction: Typical symptoms of chronic obstructive pulmonary disease (COPD) include breathlessness and reduced exercise capacity. Several laboratory- and field-based exercise tests are used to assess the exercise capacity of patients with COPD. It is unclear whether these exercise tests reflect the spirometric measures recommended for diagnosis of COPD. We therefore aimed to systematically assess the correlation between these exercise tests and common measures of lung function. Methods: A search of Embase™, MEDLINE^® and The Cochrane Library identified primary publications in English that reported data on the correlations (Pearson's r or Spearman's rho) between the outcomes of exercise tests and the physiological measures of interest: forced expiratory volume in 1 second (FEV₁), forced vital capacity, inspiratory capacity and arterial oxygen saturation. We included studies reporting on the following exercise tests: 6- and 12-minute walk tests (6MWT and 12 MWT), incremental and endurance shuttle walk tests, incremental and endurance cycle ergometer tests, and treadmill tests. Results: Of 1781 articles screened, 45 were ultimately deemed eligible for inclusion in this review. The most commonly reported lung function variable was FEV₁ (reported by 39 studies); the most commonly reported exercise test was the 6-minute walk test (reported by 24 studies). FEV₁ appears to correlate moderately-to-strongly with 6MWT and 12MWT; and moderately-to-very strongly with incremental cycle ergometer tests (ICET); evidence for other exercise tests was limited. Conclusion: There is evidence that 6MWT, 12MWT and ICET correlate with FEV₁ to some degree; - evidence for associations of other exercise tests with measures of lung function in patients with COPD is limited. Clinicians must consider this when deciding to use these tests. Further comparisons of these tests must be made in order to assess which physiological and hemodynamic characteristics they reflect in patients with COPD.

Exertional hypoxemia in stable COPD is common and predicted by circulating proadrenomedullin

BACKGROUND

The prevalence of exertional hypoxemia in unselected patients with COPD is unknown. Intermittent hypoxia leads to adrenomedullin (ADM) upregulation through the hypoxia-inducible factor-1 pathway. We aimed to assess the prevalence and the annual probability to develop exertional hypoxemia in stable COPD. We also hypothesized that increased ADM might be associated with exertional hypoxemia and envisioned that adding ADM to clinical variables might improve its prediction in COPD.

METHODS

A total of 1,233 6-min walk tests and circulating proadrenomedullin (proADM) levels from 574 patients with clinically stable, moderate to very severe COPD enrolled in a multinational cohort study and followed up for 2 years were concomitantly analyzed.

RESULTS

The prevalence of exertional hypoxemia was 29.1%. In a matrix derived from a fitted-multistate model, the annual probability to develop exertional hypoxemia was 21.6%. Exertional hypoxemia was associated with greater deterioration of specific domains of health-related quality of life, higher severe exacerbation, and death annual rates. In the logistic linear and conditional Cox regression multivariable analyses, both FEV1% predicted and proADM proved independent predictors of exertional hypoxemia (P < .001 for both). Adjustment for comorbidities, including cardiovascular disorders, and exacerbation rate did not influence results. Relative to using FEV1% predicted alone, adding proADM resulted in a significant improvement of the predictive properties (P = .018). Based on the suggested nonlinear nomogram, patients with moderate COPD (FEV1% predicted = 50%) but high proADM levels (> 2 nmol/L) presented increased risk (> 30%) for exertional desaturation.

CONCLUSIONS

Exertional desaturation is common and associated with poorer clinical outcomes in COPD. ADM improves prediction of exertional desaturation as compared with the use of FEV1% predicted alone.

TRIAL REGISTRY

ISRCTN Register; No.: ISRCTN99586989; URL: www.controlled-trials.com.

COPD patients with exertional desaturation are at a higher risk of rapid decline in lung function

PURPOSE

A recent study demonstrated that exertional desaturation is a predictor of rapid decline in lung function in patients with chronic obstructive pulmonary disease (COPD); however, the study was limited by its method used to detect exertional desaturation. The main purpose of this study was to explore whether exertional desaturation assessed using nadir oxygen saturation (SpO₂) during the 6-minute walk test (6MWT) can predict rapid lung function decline in patients with COPD.

MATERIALS AND METHODS

A retrospective analysis was performed on 57 patients with moderate to very severe COPD who underwent the 6MWT. Exertional desaturation was defined as a nadir SpO₂ of <90% during the 6MWT. Rapid decline was defined as an annual rate of decline in forced expiratory volume in 1 second (FEV₁)≥50 mL. Patients were divided into rapid decliner (n=26) and non-rapid decliner (n=31) groups.

RESULTS

A statistically significant difference in exertional desaturation was observed between rapid decliners and non-rapid decliners (17 vs. 8, p=0.003). No differences were found between the groups for age, smoking status, BODE index, and FEV₁. Multivariate analysis showed that exertional desaturation was a significant independent predictor of rapid decline in patients with COPD (relative risk, 6.8; 95% CI, 1.8 to 25.4; p=0.004).

CONCLUSION

This study supports that exertional desaturation is a predictor of rapid lung function decline in male patients with COPD.

Exertional desaturation as a predictor of rapid lung function decline in COPD

BACKGROUND

To date, no clinical parameter has been associated with the decline in lung function other than emphysema severity in COPD.

OBJECTIVES

The main purpose of this study was to explore whether the rate of lung function decline differs between COPD patients with and without exertional desaturation.

METHODS

A total of 224 subjects were selected from the Korean Obstructive Lung Disease cohort. Exertional desaturation was assessed using the 6-min walk test (6MWT), and defined as a post-exercise oxygen saturation (SpO2) of < 90% or a ≥ 4% decrease. The cohort was divided into desaturator (n = 47) and non-desaturator (n = 177) groups.

RESULTS

There was a significant difference between the desaturator and non-desaturator groups in terms of the change in pre-bronchodilator forced expiratory volume in 1 s (FEV1) over a 3-year period of follow-up (p = 0.006). The mean rate of decline in FEV1 was greater in the desaturator group (33.8 ml/year) than in the non-desaturator group (11.6 ml/year). A statistically significant difference was also observed between the two groups in terms of the change in the St. George's Respiratory Questionnaire (SGRQ) total score over 3 years (p = 0.001).

CONCLUSIONS

This study suggests, for the first time, that exertional desaturation may be a predictor of rapid decline in lung function in patients with COPD. The 6MWT may be a useful test to predict a rapid lung function decline in COPD.

Lung function tests in clinical decision-making

In this article, we review the utility of the most common lung function tests (spirometry, reversibility test, peak expiratory flow, lung volumes, maximal respiratory pressure, carbon monoxide transference, arterial blood gas, 6-minute walk test and desaturation with exercise and ergospirometry) related to the most frequent pathologies (dyspnea of undetermined origin, chronic cough, asthma, COPD, neuromuscular diseases, interstitial diseases, pulmonary vascular diseases, pre-operative evaluation and disability evaluation). Our analysis has been developed from the perspective of decision-making, clinical interpretation or aspects that the physician should take into account with their use. Consequently, the paper does not deal with aspects of quality, technique or equipment, with the exception of when regarding costs as we believe that this is an important element in the decision-making process. The document is extensively supported by references from the literature.

The relationship of the BODE index to oxygen saturation during daily activities in patients with chronic obstructive pulmonary disease

BACKGROUND

The frequency of oxygen desaturation during daily activities in chronic obstructive pulmonary disease (COPD) is poorly defined. The BODE index predicts survival in COPD. The purpose of this study was to determine the relationship between BODE scores and oxygen saturation during daily activities.

METHODS

Seventy-eight patients with COPD (FEV(1) = 37%) underwent ambulatory oximetry and activity monitoring. We defined four activity categories: Walking, Slow-Intermittent-Walking (SIW), Active-Not-Walking (ANW), and Rest. We quantified oxygen desaturation during activity using a desaturation index (DSI = % time oxygen saturation <90%). BODE scores were categorized into three groups: group I (0-3), II (4-6), and III (7-10).

RESULTS

The percentage of patients demonstrating oxygen desaturation (DSI ≥ 10%) during each activity was 55% for Walking, 35% for SIW, 15% for ANW, and 28% for Rest. There was a strong association between BODE score and desaturation for Walking and SIW. During Walking, 21, 44, and 86% of patients in BODE groups I, II, and III, respectively, demonstrated desaturation. The DSI for Walking and SIW was increased in patients in BODE groups II and III compared to group I (P < 0.006, P < 0.007, respectively). BODE score was also linked to long-term oxygen therapy (LTOT) usage; the majority of patients not on LTOT (89%) had a BODE score <7. The majority of patients on LTOT (84%) demonstrated desaturation during Walking, but 42% of patients not on LTOT also demonstrated desaturation. In this subgroup of patients not on LTOT, all patients with a BODE score ≥ 7 demonstrated desaturation during Walking.

CONCLUSIONS

The link between the BODE index and oxygen desaturation during daily activities suggests that desaturation is linked to disease severity. Our data suggest that patients with a BODE score ≥ 7 should be evaluated for desaturation during daily activities. Use of the BODE index to screen for exertional desaturation may have value as a tool that can lead to the earlier identification of patients who may be candidates for LTOT.

Sniff nasal inspiratory pressure versus IC/TLC ratio as predictors of mortality in COPD

BACKGROUND

Hyperinflation is a recognized adverse prognostic factor in COPD. As the sniff inspiratory nasal pressure (SnIP) principally reflects the severity of hyperinflation in COPD, we hypothesized that it might also be a predictor of mortality. We therefore compared the SnIP to the inspiratory capacity-to-total lung capacity (IC/TLC) ratio as predictors of mortality in advanced COPD.

METHODS

A retrospective mortality analysis of 110 patients with COPD (mean FEV(1) 1.01litres, 37% predicted; 66% male) was performed. All patients had SnIP and lung volume measurements performed. The power of each test to predict mortality was determined, and predicted survival curves were created for both the SnIP and IC/TLC ratio.

RESULTS

37 patients (34%) died during the study period (29 male, 8 female). Mortality rates were analysed with a Chi(2) test; there was a significant trend towards male death (mortality rate male vs. female; 39.7% vs. 21.6% respectively; chi(2)p=0.058, Chi 3.6). ROC curves demonstrated that both SnIP and IC/TLC ratio are predictors of mortality, but analysis by Cox proportional hazards suggested the SnIP has a stronger predictive power (SnIP vs. IC/TLC ratio; p=0.017 vs 0.525; HR 0.97 vs 0.99 respectively), and analysis of the area under ROC curves (AUC) suggest that SnIP is a better discriminator than IC/TLC ratio (AUC SnIP vs IC/TLC; 0.679 vs 0.618).

CONCLUSIONS

The SnIP conveys at least as much predictive power for mortality in COPD as hyperinflation determined by IC/TLC ratio. This test is cheaper, quicker and easier than measuring lung volumes by plethysmography.

Reduced confounding by impaired ventilatory function with oxygen uptake efficiency slope and VE/VCO2 slope rather than peak oxygen consumption to assess exercise physiology in suspected heart failure

Heart failure and ventilatory disease often coexist; both create abnormalities in cardiopulmonary exercise test measurements. The authors evaluated the relative dependency of a well-recognized index of heart failure, peak oxygen consumption (VO(2)), and 2 newer indices, the minute ventilation (VE)/carbon dioxide production (VCO(2)) slope and oxygen uptake efficiency slope (OUES), on standard markers of impaired cardiac and ventilatory function. One hundred twenty-four patients (median age, 65.8; range, 22.6-84.9), with functional limitation from clinical heart failure were exercised. Peak VO(2) was 17.14 ± 7.58 mL/kg/min, VE/VCO(2) slope 50.1 ± 20.1, OUES 1.46 ± 0.68 L/min, and forced expiratory volume in 1 second (FEV(1) ) 1.88 ± 0.75 L. Peak VO(2) is substantially more sensitive to FEV(1) than ejection fraction (4.0 mL/kg/min difference between above- and below-median FEV(1) and 1.5 mL/kg/min between above- and below-median ejection fraction). OUES does not share this peculiar excess sensitivity to FEV(1) (0.12 L/min difference between above- and below-median FEV(1) and 0.01 L/min between above- and below-median ejection fraction). VE/VCO(2) slope has a borderline effect by FEV(1) (7.07 difference between above- and below-median FEV(1) and 2.07 between above- and below-median ejection fraction). Although widely used as a marker of heart failure severity, peak VO(2) is very sensitive to spirometry status and is indeed more affected by FEV(1) than by ejection fraction. OUES in contrast does not show this preferential sensitivity to impaired FEV(1).

The minimal important difference of exercise tests in severe COPD

Our aim was to determine the minimal important difference (MID) for 6-min walk distance (6MWD) and maximal cycle exercise capacity (MCEC) in patients with severe chronic obstructive pulmonary disease (COPD). 1,218 patients enrolled in the National Emphysema Treatment Trial completed exercise tests before and after 4-6 weeks of pre-trial rehabilitation, and 6 months after randomisation to surgery or medical care. The St George's Respiratory Questionnaire (domain and total scores) and University of California San Diego Shortness of Breath Questionnaire (total score) served as anchors for anchor-based MID estimates. In order to calculate distribution-based estimates, we used the standard error of measurement, Cohen's effect size and the empirical rule effect size. Anchor-based estimates for the 6MWD were 18.9 m (95% CI 18.1-20.1 m), 24.2 m (95% CI 23.4-25.4 m), 24.6 m (95% CI 23.4-25.7 m) and 26.4 m (95% CI 25.4-27.4 m), which were similar to distribution-based MID estimates of 25.7, 26.8 and 30.6 m. For MCEC, anchor-based estimates for the MID were 2.2 W (95% CI 2.0-2.4 W), 3.2 W (95% CI 3.0-3.4 W), 3.2 W (95% CI 3.0-3.4 W) and 3.3 W (95% CI 3.0-3.5 W), while distribution-based estimates were 5.3 and 5.5 W. We suggest a MID of 26 ± 2 m for 6MWD and 4 ± 1 W for MCEC for patients with severe COPD.

Exertional desaturation in patients with chronic obstructive pulmonary disease

Although the Centers for Medicare and Medicaid Services oxygen prescription guidelines utilize a threshold arterial oxygen tension <or=55 mmHg or an oxygen saturation <or=88%, a range of oxygen levels and relative declines have been used in investigations of exertional desaturation in patients with chronic obstructive pulmonary disease (COPD). There is no uniform definition of exertional hypoxemia or standardized exercise protocol to elicit decreases in oxygen levels in individuals with COPD. The causes for exertional desaturation in patients with COPD are multifactorial with ventilation-perfusion mismatching, diffusion-type limitation, shunting and reduced oxygen content of mixed venous blood all contributing to some degree. Neither resting oxygen saturation nor pulmonary function studies can reliably predict which patients with COPD will develop exertional desaturation. However, preserved pulmonary function, especially diffusing capacity, reliably predicts which patients with COPD will sustain oxygenation during exercise. Although exertional desaturation in patients with COPD appears to portend a poor prognosis, there is no evidence that maintenance of normoxemia during exercise improves the survival of these patients. Studies of the effect of supplemental oxygen on exercise performance in individuals with COPD who desaturate with exertion have yielded conflicting results. The use of short-term or "burst" oxygen either prior to or after exertion may not have significant clinical benefit. Differences in the definition of desaturation, mode of exercise, and characteristics of the patient population make it difficult to compare studies of exertional desaturation and its treatment and to determine their applicability to clinical practice.

Hyperinflation and its management in COPD

Chronic obstructive pulmonary disease (COPD) is characterized by poorly reversible airflow limitation. The pathological hallmarks of COPD are inflammation of the peripheral airways and destruction of lung parenchyma or emphysema. The functional consequences of these abnormalities are expiratory airflow limitation and dynamic hyperinflation, which then increase the elastic load of the respiratory system and decrease the performance of the respiratory muscles. These pathophysiologic features contribute significantly to the development of dyspnea, exercise intolerance and ventilatory failure. Several treatments may palliate flow limitation, including interventions that modify the respiratory pattern (deeper, slower) such as pursed lip breathing, exercise training, oxygen, and some drugs. Other therapies are aimed at its amelioration, such as bronchodilators, lung volume reduction surgery or breathing mixtures of helium and oxygen. Finally some interventions, such as inspiratory pressure support, alleviate the threshold load associated to flow limitation. The degree of flow limitation can be assessed by certain spirometry indexes, such as vital capacity and inspiratory capacity, or by other more complexes indexes such as residual volume/total lung capacity or functional residual capacity/total lung capacity. Two of the best methods to measure flow limitation are to superimpose a flow–volume loop of a tidal breath within a maximum flow–volume curve, or to use negative expiratory pressure technique. Likely this method is more accurate and can be used during spontaneous breathing. A definitive definition of dynamic hyperinflation is lacking in the literature, but serial measurements of inspiratory capacity during exercise will document the trend of end-expiratory lung volume and allow establishing relationships with other measurements such as dyspnea, respiratory pattern, exercise tolerance, and gas exchange.

Replacement of the 6-min Walk Test With Maximal Oxygen Consumption in the BODE Index Applied to Patients With COPD

INTRODUCTION

Patients with COPD have decreased exercise capacity and low oxygen consumption (Vo(2)) during formal cardiopulmonary exercise testing, and lower scores on health-related quality of life questionnaires. When isolated, these three variables show different correlations with COPD mortality. The multidimensional BODE (body mass index[BMI], airflow obstruction, dyspnea, and exercise capacity in COPD) index, which comprises four variables including the 6-min walk test (6MWT), predicts survival in COPD.

OBJECTIVES

To evaluate the degree of association between the values of the BODE index using the 6MWT with the BODE index using maximal Vo(2) (Vo(2)max) obtained in a maximal incremental test.

MATERIALS AND METHODS

Fifty patients with mild-to-severe COPD (average age, 63.5 +/- 9.9 years; FEV(1), 65.3 +/- 23.6% of predicted) [+/- SD] had BMI, spirometric function (FVC and FEV(1)), and dyspnea status (Medical Research Council) evaluated. Two BODE index scores were then completed: one with the 6MWT, and one with the Vo(2)max obtained during maximal incremental testing on a treadmill.

RESULTS

Correlation between BODE index and Vo(2) in milliliters per minute per kilogram (r = - 0.41) was weak; the correlation was moderate (r = - 0.64) when Vo(2) percentage of predicted was used. The BODE index modified by replacing the 6MWT with Vo(2) showed excellent correlations with Vo(2) in milliliters per minute per kilogram (r = 0.92) and Vo(2) percentage of predicted (r = 0.95).

CONCLUSION

The excellent correlation between the conventional BODE index and the modified BODE index with Vo(2) replacing the 6MWT enables us to reach the conclusion that the original BODE index is very effective in the evaluation of COPD patients.

Walking distance is a predictor of exacerbations in patients with chronic obstructive pulmonary disease

BACKGROUND

Patients with chronic obstructive pulmonary disease (COPD) are responsible for a high utilisation of the health care resources, and the cost is expected to increase. Physiological measures of lung function often fail to describe the impact the symptoms have on exacerbations, days of hospitalisation, and on a patient's health.

METHODS

Twenty-one patients (14 female) with COPD (65 years, 40-79 years) admitted to the Department of Respiratory Medicine in Uppsala, performed a pulmonary function test (FEV(1)% predicted=37) and health status measurement (St. Georges Respiratory Questionnaire, SGRQ) at discharge. Four to six weeks after discharge, when they were in a stable clinical condition, they performed an exercise test (Incremental Shuttle Walk Test, ISWT) to measure their exercise capacity.

RESULTS

Nine of 21 patients (43%) were rehospitalised within 12 month. The mean distance walked in the ISWT was 174m in patients who were hospitalised and 358m in non-hospitalised patients (P<0.001). Oxygen saturation 88% after the ISWT was found in 73% of hospitalised patients in contrast to only 22% in non-hospitalised patients (P<0.05). Activity related health status (SGRQ-activity) was higher (worse) in hospitalised patients than in non-hospitalised patients (75 vs. 50) (P<0.05). The association between walking distance and the risk of rehospitalisation was significant after adjusting for oxygen saturation and health status (hazard risk ratio 0.8 (0.67-0.97) per 10m). This study has shown that walking distance is a good and reliable predictor of rehospitalisations in moderately and severely disabled patients with COPD.

Distance and oxygen desaturation in 6-min walk test predict prognosis in COPD patients

The aim of the present study was to predict the prognosis of Chronic obstructive pulmonary disease (COPD) patients who underwent comprehensive pulmonary rehabilitation (PR). A total of 144 patients who performed PR between 1992 and 1999 was assessed. After PR, 67 patients underwent lung volume reduction surgery (LVRS). Baseline data before PR consisted of body mass index, serum albumin levels, use of supplement oxygen at home, pulmonary function, arterial blood gas analysis, and distance and fall of hemoglobin oxygen saturation (DeltaSpO(2)) in 6-min walk test. In addition to pre-PR factors, treatment with LVRS was taken into the analysis. The prognostic significance of variables influencing survival was determined by univariate analysis with Log rank test or multivariate analysis using Cox's proportional hazard model. By a median follow-up time of 8.4 years, the median survival time was 8.1 years (95% confidence interval: 6.9-9.4 years). Albumin level, PaCO(2), distance and DeltaSpO(2) were significant prognostic factors in univariate analysis. LVRS did not affect the prognosis. The multivariate analysis showed short distance and increase of DeltaSpO(2) as significant independent predictors of the risk of death. 6-min walk test was very useful for predicting the prognosis of the COPD patients.