Explained variance for blood gases in a population with COPD.

INTRODUCTION: Variation of blood gas levels in chronic obstructive pulmonary disease (COPD) patients has not been extensively reported and there is limited knowledge about predictors of chronic respiratory failure in COPD patients. OBJECTIVES: The aim of this study was to identify predictors of hypoxemia, hypercapnia and increased alveolar-arterial oxygen difference in COPD patients. We hypothesized that prediction of arterial blood gases will be improved in multivariate models including measurements of lung function, anthropometry and systemic inflammation. METHODS: A cross-sectional sample of 382 Norwegian COPD patients, age 40-76, Global Initiative for Chronic Obstructive Lung Disease stage II-IV, with a smoking history of at least 10 pack-years, underwent extensive measurements, including medical examination, arterial blood gases, systemic inflammatory markers, spirometry, plethysmography, respiratory impedance and bioelectrical impedance. Possible predictors of arterial oxygen (PaO(2)), arterial carbon dioxide (PaCO(2)) and alveolar-arterial oxygen difference (AaO(2)) were analyzed with both bivariate and multiple regression methods. RESULTS: We found that various lung function measurements were significantly associated with PaO2, PaCO(2) and AaO(2). In addition, heart rate and Fat Mass Index were predictors of PaO(2) and AaO(2), while heart failure and current smoking status were associated with PaCO(2). The explained variance (R(2)) in the final multivariate regression models was 0.14-0.20. CONCLUSIONS: With a wide assortment of possible clinical predictors, we could explain 14-20% of the variation in blood gas measurements in COPD patients.

Respiratory symptoms in adults are related to impaired quality of life, regardless of asthma and COPD: results from the European community respiratory health survey.

BACKGROUND: Respiratory symptoms are common in the general population, and their presence is related to Health-related quality of life (HRQoL). The objective was to describe the association of respiratory symptoms with HRQoL in subjects with and without asthma or COPD and to investigate the role of atopy, bronchial hyperresponsiveness (BHR), and lung function in HRQoL. METHODS: The European Community Respiratory Health Survey (ECRHS) I and II provided data on HRQoL, lung function, respiratory symptoms, asthma, atopy, and BHR from 6009 subjects. Generic HRQoL was assessed through the physical component summary (PCS) score and the mental component summary (MCS) score of the SF-36.Factor analyses and linear regressions adjusted for age, gender, smoking, occupation, BMI, comorbidity, and study centre were conducted. RESULTS: Having breathlessness at rest in ECRHS II was associated with mean score (95% CI) impairment in PCS of -8.05 (-11.18, -4.93). Impairment in MCS score in subjects waking up with chest tightness was -4.02 (-5.51, -2.52). The magnitude of HRQoL impairment associated with respiratory symptoms was similar for subjects with and without asthma/COPD. Adjustments for atopy, BHR, and lung function did not explain the association of respiratory symptoms and HRQoL in subjects without asthma and/or COPD. CONCLUSION: Subjects with respiratory symptoms had poorer HRQoL; including subjects without a diagnosis of asthma or COPD. These findings suggest that respiratory symptoms in the absence of a medical diagnosis of asthma or COPD are by no means trivial, and that clarifying the nature and natural history of respiratory symptoms is a relevant challenge. Several community studies have estimated the prevalence of common respiratory symptoms like cough, dyspnoea, and wheeze in adults. Although the prevalence varies to a large degree between studies and geographical areas, respiratory symptoms are quite common. The prevalences of respiratory symptoms in the European Community Respiratory Health Study (ECRHS) varied from one percent to 35%. In fact, two studies have reported that more than half of the adult population suffers from one or more respiratory symptoms. Respiratory symptoms are important markers of the risk of having or developing disease. Respiratory symptoms have been shown to be predictors for lung function decline, asthma, and even all-cause mortality in a general population study . In patients with a known diagnosis of asthma or chronic obstructive pulmonary disease (COPD), respiratory symptoms are important determinants of reduced health related quality of life (HRQoL). The prevalence of respiratory symptoms exceeds the combined prevalences of asthma and COPD, and both asthma and COPD are frequently undiagnosed diseases. Thus, the high prevalence of respiratory symptoms may mirror undiagnosed and untreated disease.The common occurrence of respiratory symptoms calls for attention to how these symptoms affect health also in subjects with no diagnosis of obstructive airways disease. Impaired HRQoL in the presence of respiratory symptoms have been found in two population-based studies 619, but no study of respiratory symptoms and HRQoL have separate analyses for subjects with and without asthma and COPD, and no study provide information about extensive objective measurements of respiratory health. The ECRHS is a randomly sampled, multi-cultural, population based cohort study. The ECRHS included measurements of atopy, bronchial hyperresponsiveness (BHR), and lung function, and offers a unique opportunity to investigate how respiratory symptoms affect HRQoL among subjects both with and without obstructive lung disease.In the present paper we aimed to: 1) Describe the relationship between respiratory symptoms and HRQoL in an international adult general population and: 2) To assess whether this relationship varied with presence of asthma and/or COPD, or presence of objective functional markers like atopy and BHR.

Neutrophil gelatinase-associated lipocalin: a biomarker in COPD.

BACKGROUND: Neutrophil gelatinase-associated lipocalin (NGAL) is an antimicrobial peptide that could be involved in the pathogenesis of COPD. This study aimed to measure the plasma levels of NGAL in a large cohort of patients with COPD and control subjects and examine the levels of NGAL by COPD characteristics. METHODS: The study included 402 patients with COPD and 229 control subjects aged 40 to 76 years from the Bergen COPD Cohort Study. All patients with COPD had an FEV(1)/FVC ratio of < 0.7, an FEV(1) < 80% predicted, and a smoking history of ≥ 10 pack-years. Plasma levels of NGAL were determined by enzyme immunoassay. Linear regression models were fitted with NGAL as the outcome variable. Confounders examined were sex, age, smoking, Charlson comorbidity score, use of inhaled steroids, neutrophil cell count, plasma creatinine and ferritin, and C-reactive protein. RESULTS: Mean ± SD plasma concentrations of NGAL were 75.1 ± 31.8 ng/mL in patients with COPD and 56.5 ± 22.0 ng/mL in control subjects (P < .01). NGAL levels were bivariately associated with age, smoking, body composition, Charlson comorbidity score, neutrophil blood count, creatinine, and C-reactive protein but were significantly elevated in patients with COPD, even after adjustment for confounders. Frequent exacerbations and hypoxemia was associated with higher levels of NGAL, whereas increasing Global Initiative for Chronic Obstructive Lung Disease stage was associated with lower levels of NGAL among patients with COPD. CONCLUSIONS: Plasma levels of NGAL were significantly higher in patients with COPD compared with control subjects. NGAL was related to important COPD characteristics.

Asthma and health-related quality of life - effect of adjusting for potential confounders.

BACKGROUND: Health-related quality of life (HRQoL) is an increasingly important outcome measure in medical research. We wanted to evaluate how adjustment for potential confounders affected the relationship between HRQoL and asthma. Furthermore, we wanted to evaluate the relationship of environmental tobacco smoke (ETS) with HRQoL. METHODS: We carried out a cross-sectional Norwegian community study in 1996/1997 including 2306 randomly selected subjects aged 26 years-81 years. Data on HRQoL were measured by SF-12. The data were analyzed by robust linear regression analyses with the physical component score (PCS) and the mental component score (MCS) as dependent variables. The effect of adjusting for the potential confounders was analyzed by bootstrap confidence intervals for differences between the adjusted and unadjusted models. RESULTS: The difference in the asthma coefficients between the unadjusted and adjusted models for both PCS and MCS varied from 0.1 to 1.1. The confidence intervals for these differences for PCS were (-0.3, 1.6) and (0.4, 1.8), using the definition 'asthma last 12 months' and 'physician's diagnosis of asthma', respectively. The confidence intervals for the corresponding differences for MCS were (-0.01, 1.3) and (-0.6, 0.4), respectively. Univariately, PCS was lower among subjects reporting ETS at home compared to people not reporting ETS at home, but this difference did not persist in the multivariate analyses. ETS at home was associated with slightly improved MCS. CONCLUSION: Adjusting for potential confounders does not change the relationship between asthma and HRQoL overtly.

Respiratory symptoms, COPD severity, and health related quality of life in a general population sample.

AIMS: The aim of this report from a general population sample was to examine the association of respiratory symptoms and COPD severity with HRQoL (health related quality of life). METHODS: In a general population study in 1996-1997, of 3181 invited subjects aged 26-81 years, a total of 2405 returned postal questionnaires on respiratory symptoms and attended a clinical examination. Altogether 2306 subjects completed the SF-12 questionnaire, a general HRQoL questionnaire. The univariate relationships between respiratory symptom burden, degree of bronchial obstruction, and HRQoL were investigated by the Wilcoxon test for trend and the Mann-Whitney U-test. Adjustment for gender, age, education, and smoking habits was done using linear regression with estimation of robust standard errors. RESULTS: In asymptomatic subjects the mean (SD) physical component scale (PCS) score was 51.8 (7.4) and the mean (SD) mental component scale (MCS) score was 52.6 (8.0). Having one to six symptoms gave mean (SD) PCS scores of 49.6 (8.8), 48.2 (9.7), 45.1 (10.4), 42.1 (11.9), 38.1 (11.4), and 34.7 (10.2), respectively. The corresponding numbers for MCS scores were 50.9 (8.0), 48.8 (9.6), 48.9 (10.6), 47.2 (10.2), 43.6 (10.4), and 44.2 (9.8), respectively. In the multivariate model, subjects in GOLD stages 3 and 4 had significantly reduced PCS scores, while subjects with COPD had a significantly higher MCS score than subjects without COPD, after adjustment for symptoms. Both the PCS and MCS scores declined significantly with increasing number of respiratory symptoms. CONCLUSION: In a general population sample, the burden of respiratory symptoms is more strongly associated with generic HRQoL than is lung function.

Changes in respiratory symptoms and health-related quality of life.

BACKGROUND: For a number of chronic diseases, health-related quality of life (HRQoL) has become an important outcome measure. Little data are available on how incidence, remission, or persistence of respiratory symptoms affect HRQoL. METHODS: The Hordaland County Cohort Study was conducted between 1985 and 1997, and comprised 3,786 subjects, randomly selected, and aged 15 to 70 years in 1985. Respiratory symptoms were assessed both in 1985 and 1996/1997, and HRQoL was measured by the Short-Form 12 questionnaire in 1996/1997. Robust linear regression analysis was used to examine the relationship between changes in six respiratory symptoms and the physical component score (PCS) and mental component score (MCS). RESULTS: Among subjects with incidence or persistence of any of the six examined respiratory symptoms, PCS and MCS were significantly lower than among subjects without symptoms. The PCS was more reduced than the MCS in symptomatic subjects; however, this trend was reduced after adjustment for the confounder's gender, age, educational level, body mass index, and smoking status. Dyspnea attacks and dyspnea grade 2 had the largest negative impact on both PCS and MCS. CONCLUSIONS: This is the first longitudinal population study to show the negative impact of incidence and persistence of respiratory symptoms on HRQoL.