Inspiratory-to-Total Lung Capacity Ratio Predicts Mortality in Patients with Chronic Obstructive Pulmonary Disease

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112

The objective of this study was to redesign the current grading of obstructive lung disease so that it is clinically relevant and free of biases related to age, height, sex and ethnic group.Spirometric records from 17 880 subjects (50.4% female) from hospitals in Australia and Poland, and 21 191 records (53.0% female) from two epidemiological studies (age range 18-95 years) were analysed. We adopted the American Thoracic Society(ATS)/European Respiratory Society (ERS) criteria for airways obstruction based on an forced expiratory volume in 1 s (FEV1)/(forced) vital capacity ((F)VC) ratio below the fifth percentile and graded the severity of pulmonary function impairment using z-scores for FEV1, which signify how many standard deviations a result is from the mean predicted value.Using the lower limit of normal for FEV1/(F)VC and z-scores for FEV1 of -2, -2.5, -3 and -4 to delineate severity grades of airflow limitation leads to close agreement with ATS/ERS severity classifications and removes age, sex and height related bias.The new classification system is simple, easily memorised and clinically valid. It retains previously established associations with clinical outcomes and avoids biases due to the use of per cent predicted FEV1. Combined with the Global Lung Function prediction equations it provides a worldwide diagnostic standard, free of bias due to age, height, sex and ethnic group. @ERSpublications Using FEV1 z-scores to classify severity of airways obstruction is clinically valid and overcomes bias inherent in % pred

Section: Discussionmentioning

confidence: 99%

Grading the severity of airways obstruction: new wine in new bottles

Quanjer

Pretto

Brazzale

et al. 2013

123

112

“…The 6MWD was expressed in absolute values and as per cent pred using two published reference values [18,19]. Inspiratory fraction, or ratio of inspiratory capacity (IC) to total lung capacity (TLC) was used as a measure of static lung hyperinflation [11]. The combined Charlson index was used to determine the degree of comorbidity [22].…”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, it correlates well with other important outcomes in COPD patients such as dyspnoea, airway obstruction and lung hyperinflation [11]. The test has been shown to be an important prognostic factor for outcome independent of the forced expiratory volume in one second (FEV1) [12].…”

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confidence: 90%

The 6-min walking distance: long-term follow up in patients with COPD

Casanova¹,

Côté²,

Marı́n³

et al. 2007

154

105

The 6-min walking distance (6MWD) test is used in clinical practice and research into patients with chronic obstructive pulmonary disease (COPD). However, little is known about natural long-term change in this parameter.The 6MWD was measured at baseline and then annually for 5 yrs in 294 patients with COPD and its annual rate of decline was determined. Forced expiratory volume in one second (FEV1) was also measured and the relationship between changes in both markers was explored.At baseline, the median 6MWD was 380 m (range 160-600 m). It declined by 19% (16 m?yr -1 ) over the 5 yrs compared with baseline in patients with American Thoracic Society/European Respiratory Society stage III COPD (FEV1 30-50% predicted) and by 26% (15 m?yr -1 ) in patients with stage IV COPD (FEV1 ,30% pred). Over the 5-yr follow-up, the proportion of patients with a minimal clinically significant decline of 54 m increased with the severity of the disease. It was 24% in stage II, 45% in stage III, and 63% in stage IV disease. In contrast, the rate of decline of FEV1 was greater in patients with milder airflow obstruction and lesser in patients with lower absolute FEV1 values.In conclusion, the 6-min walking distance test provides increasingly useful information as the severity of chronic obstructive pulmonary disease increases.KEYWORDS: Chronic obstructive pulmonary disease, 6-min walking distance T he 6-min walking distance (6MWD) test has gained importance in the assessment of functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD) [1,2] Introduced in 1976 as a 12-min walk test to measure the exercise capacity of patients with COPD, the abbreviated 6MWD has proved to be reliable, inexpensive, safe and easy to apply [7][8][9][10]. Furthermore, it correlates well with other important outcomes in COPD patients such as dyspnoea, airway obstruction and lung hyperinflation [11]. The test has been shown to be an important prognostic factor for outcome independent of the forced expiratory volume in one second (FEV1) [12]. The 6MWD is a submaximal excercise test, but it correlates well with the maximal cardiopulmonary exercise test [13][14][15], and appears to be better tolerated and more reflective of the activities of daily living than other walk tests [16,17].While there is plenty of data concerning the natural history of FEV1 over time, little information has been published regarding the temporal behaviour of the 6MWD. This is a significant omission, as the 6MWD test is frequently used to evaluate the long-term impact of interventions. Changes in 6MWD over time have been addressed in one published study [12], but it was limited to patients with severe COPD, the follow-up time was relatively short (1 yr) and the decline trend was established with only two measurements.As part of the large body mass index, degree of obstruction, dyspnoea and exercise capacity (BODE) cohort, the present authors have evaluated the 6MWD systematically as one of several variables included in the evaluation of pati...

“…Other resting indices have been found to predict the prognosis of these patients, the most important being BMI [175,176], IC/total lung capacity (TLC) ratio [177], arterial hypoxaemia during sleep [178], pulmonary artery pressure [179], mixed venous partial pressure of oxygen (PO 2 ) [180] and the degree of functional breathlessness [181].…”

Section: Utility Of Exercise Testing In Prognostic Evaluationmentioning

confidence: 99%

Recommendations on the use of exercise testing in clinical practice

Palange¹,

Ward²,

Carlsen³

et al. 2006

534

383

Evidence-based recommendations on the clinical use of cardiopulmonary exercise testing (CPET) in lung and heart disease are presented, with reference to the assessment of exercise intolerance, prognostic assessment and the evaluation of therapeutic interventions (e.g. drugs, supplemental oxygen, exercise training). A commonly used grading system for recommendations in evidence-based guidelines was applied, with the grade of recommendation ranging from A, the highest, to D, the lowest.For symptom-limited incremental exercise, CPET indices, such as peak O 2 uptake (V9O 2 ), V9O 2 at lactate threshold, the slope of the ventilation-CO 2 output relationship and the presence of arterial O 2 desaturation, have all been shown to have power in prognostic evaluation. In addition, for assessment of interventions, the tolerable duration of symptom-limited high-intensity constant-load exercise often provides greater sensitivity to discriminate change than the classical incremental test. Field-testing paradigms (e.g. timed and shuttle walking tests) also prove valuable.In turn, these considerations allow the resolution of practical questions that often confront the clinician, such as: 1) ''When should an evaluation of exercise intolerance be sought?''; 2) ''Which particular form of test should be asked for?''; and 3) ''What cluster of variables should be selected when evaluating prognosis for a particular disease or the effect of a particular intervention?''