Lung function in relation to six-minute walk test in pulmonary hypertension.

Background: Pulmonary hypertension (PH) is a progressive disorder of the pulmonary circulation, associated with diverse medical conditions. Exercise limitation is the most prominent symptom in PH. Exercise capacity, commonly assessed through a six-minute walk test (6MWT), correlates with both functional status and survival in PH. Few studies have analysed the relation between respiratory function and exercise limitation. Therefore, we investigated the relationship between resting pulmonary function, exercise capacity, and exertional desaturation, assessed through the 6MWT, in unselected PH patients. Methods: Fifty consecutive patients with PH diagnosis, referred for pulmonary function testing (lung volume, spirometry, and diffusing capacity for carbon monoxide (DLCO)) and 6MWT, were recruited at Molinette University Hospital, Turin. Results: The majority of the patients (54%) had PH due to left heart disease. Airway obstruction (FEV1/VC-ratio < 0.7) was found in 46% of the patients and they performed significantly worse in the 6MWT than unobstructed patients (307 m vs. 377 m). Patients with PH due to left heart disease also performed significantly poorer 6MWT when airway obstruction was present (305 m vs. 389 m). Twenty-two patients (44%) presented exertional desaturation upon 6MWT. Lower DLCO divided by the alveolar volume (DLCO/VA), FEV1/VC-ratios and resting PaO2-values were significantly correlated with exertional desaturation after adjustments for age, sex, BMI, and smoking habits. DLCO/VA was the main determinant of exertional desaturation in a stepwise regression model. Conclusions: Spirometric parameters of airway obstruction were related to walk distance and exercise-induced desaturation in PH patients. This suggests a place for spirometry in clinical monitoring of PH patients.

Cross-sectional and longitudinal analyses of the association between lung function and exercise capacity in healthy Norwegian men.

BACKGROUND: It is widely accepted that exercise capacity in healthy individuals is limited by the cardiac function, while the respiratory system is considered oversized. Although there is physiological, age-related decline in both lung function and physical capacity, the association between decline in lung function and decline in exercise capacity is little studied. Therefore, we examined the longitudinal association between lung function indices and exercise capacity, assessed by the total amount of work performed on a standardized incremental test, in a cohort of middle-aged men. METHODS: A total of 745 men between 40 and 59 years were examined using spirometry and standardized bicycle exercise ECG test within "The Oslo Ischemia Study," at two time points: once during 1972-1975, and again, approximately 16 years later, during 1989-1990. The subjects exercise capacity was assessed as physical fitness i.e. the total bicycle work (in Joules) at all workloads divided by bodyweight (in kg). RESULTS: Higher FEV1, FVC and PEF values related to higher physical fitness at both baseline and follow-up (all p values < 0.05). Higher explanatory values were found at follow-up than baseline for FEV1 (r2 = 0.16 vs. r2 = 0.03), FVC (r2 = 0.14 vs. r2 = 0.03) and PEF (r2 = 0.13 vs. r2 = 0.02). No significant correlations were found between decline in physical fitness and declines in FEV1, FVC or PEF. CONCLUSIONS: A weak association between lung function indices and exercise capacity, assessed through physical fitness, was found in middle-aged, healthy men. This association was strengthened with increasing age, suggesting a larger role for lung function in limiting exercise capacity among elderly subjects. However, decline in physical fitness over time was not related to decline in lung function.

Clinical outcome and functional characteristics of patients with asymptomatic low-flow low-gradient severe aortic stenosis with preserved ejection fraction are closer to high-gradient severe than to moderate aortic stenosis.

Asymptomatic "paradoxic" severe low-flow low-gradient aortic stenosis with preserved ejection fraction (PAS) constitutes a challenging condition where the optimal management and follow-up remain elusive. We evaluated the clinical outcome in patients with PAS as compared to asymptomatic patients with moderate (MAS) or classical severe aortic stenosis (CAS). Consecutive asymptomatic moderate or severe aortic stenosis patients without concomitant other heart or lung disease (n = 121) were invited. Participants (n = 74) were assigned to three subgroups with regard to degree of aortic stenosis: MAS (n = 25), CAS (n = 22) and PAS (n = 27). Echocardiographic parameters at baseline and clinical outcome data after > 3 years of follow-up time were obtained. Patients with PAS had the smallest stroke volumes and the highest relative wall thickness (p < 0.05). Left ventricular mass index was highest in subjects with CAS, followed closely by PAS and eventually MAS subjects. Whereas ejection fraction was similar amongst the subgroups, a stepwise decrease in global longitudinal left ventricular strain with increasing degree of aortic stenosis was observed, with CAS patients displaying the lowest mean global longitudinal strain, followed by PAS and MAS. A trend towards increasing mortality rate by increasing degree of stenosis was observed. Patients with CAS underwent aortic valve replacement surgery more frequently than both PAS and MAS (p < 0.001). These data suggest that echocardiographic parameters and clinical outcome in patients with PAS bear closer resemblance to CAS than to MAS, but management of PAS is more conservative than in CAS.

Impaired Carbon Monoxide Diffusing Capacity is the strongest lung function predictor of decline in 12 minute-walking distance in COPD; a 5-year follow-up study.

BACKGROUND: The purpose of this study was to evaluate the longitudinal relationship between functional exercise capacity, assessed through standardized 12-minute walk test (12MWT), and various lung function parameters obtained using spirometry, body plethysmography and diffusing capacity (DLco) measurements in patients with COPD. METHODS: Spirometry, body plethysmography and DLco-measurements were performed at baseline in 84 subjects with moderate to very severe COPD and at follow-up visit (n = 34) after 5 years. Functional exercise capacity was determined using standardized 12MWT. RESULTS: Patients were characterized at baseline by FEV1 of 1.2 ± 0.4 L (41 ± 13% predicted), RV of 3.4 ± 1.0 L (187 ± 58% predicted) and DLco of 3.8 ± 1.2 mmol/min/kPa (51 ± 16% predicted). A decrease of 12MWD was found between baseline and follow-up (928 ± 193 m vs. 789 ± 273 m, p < 0.001). DLco and 12MWD at baseline were the only independent predictors of 12MWD at follow-up in a multiple logistic regression model that also included all other lung function parameters, gender, age and BMI. Decline in 12MWD was mainly explained by deterioration in DLco. Furthermore, DLco value at baseline had the highest explanatory value for the loss in 12MWD after 5 years (R2 = 0.18, p = 0.009). CONCLUSIONS: In a 5-year longitudinal study, DLco-measurements at baseline were the most important predictors of declining exercise capacity in COPD patients. These results suggest that integration of DLco in the clinical workup provides a more comprehensive assessment in patients with COPD.

CV imaging: what was new in 2012?

Echocardiography, single-photon emission computed tomography (SPECT), positron emission tomography (PET), cardiac magnetic resonance, and cardiac computed tomography can be used for anatomic and functional imaging of the heart. All 4 methods are subject to continuous improvement. Echocardiography benefits from the more widespread availability of 3-dimensional imaging, strain and strain rate analysis, and contrast applications. SPECT imaging continues to provide very valuable prognostic data, and PET imaging, on the one hand, permits quantification of coronary flow reserve, a strong prognostic predictor, and, on the other hand, can be used for molecular imaging, allowing the analysis of extremely small-scale functional alterations in the heart. Magnetic resonance is gaining increasing importance as a stress test, mainly through perfusion imaging, and continues to provide very valuable prognostic information based on late gadolinium enhancement. Magnetic resonance coronary angiography does not substantially contribute to clinical cardiology at this point in time. Computed tomography imaging of the heart mainly concentrates on the imaging of coronary artery lumen and plaque and has made substantial progress regarding outcome data. In this review, the current status of the 5 imaging techniques is illustrated by reviewing pertinent publications of the year 2012.

Impaired carbon monoxide diffusing capacity is the strongest predictor of exercise intolerance in COPD.

BACKGROUND: Exercise intolerance is a hallmark of chronic obstructive pulmonary disease (COPD) and forced expiratory volume in one second (FEV1) is the traditional metric used to define the severity of COPD. However, there is dissociation between FEV1 and exercise capacity in a large proportion of subjects with COPD. The aim of this study was to investigate whether other lung function parameters have an additive, predictive value for exercise capacity and whether this differs according to the COPD stage. METHODS: Spirometry, body plethysmography and diffusing capacity for carbon monoxide (DLCO) were performed on 88 patients with COPD GOLD stages II-IV. Exercise capacity (EC) was determined in all subjects by symptom-limited, incremental cycle ergometer testing. RESULTS: Significant relationships were found between EC and the majority of lung function parameters. DLCO, FEV1 and inspiratory capacity (IC) were found to be the best predictors of EC in a stepwise regression analysis explaining 72% of EC. These lung function parameters explained 76% of EC in GOLD II, 72% in GOLD III and 40% in GOLD IV. DLCO alone was the best predictor of exercise capacity in all GOLD stages. CONCLUSIONS: Diffusing capacity was the strongest predictor of exercise capacity in all subjects. In addition to FEV1, DLCO and IC provided a significantly higher predictive value regarding exercise capacity in COPD patients. This suggests that it is beneficial to add measurements of diffusing capacity and inspiratory capacity when clinically monitoring COPD patients.

Nocturnal gastro-oesophageal reflux, asthma and symptoms of OSA: a longitudinal, general population study.

Nocturnal gastro-oesophageal reflux (nGOR) is associated with asthma and obstructive sleep apnoea (OSA). Our aim was to investigate whether nGOR is a risk factor for onset of asthma and onset of respiratory and OSA symptoms in a prospective population-based study. We invited 2640 subjects from Iceland, Sweden and Belgium for two evaluations over a 9-year interval. They participated in structured interviews, answered questionnaires, and underwent spirometries and methacholine challenge testing. nGOR was defined by reported symptoms. Subjects with persistent nGOR (n=123) had an independent increased risk of new asthma at follow-up (OR 2.3, 95% CI 1.1-4.9). Persistent nGOR was independently related to onset of respiratory symptoms (OR 3.0, 95% CI 1.6-5.6). The risk of developing symptoms of OSA was increased in subjects with new and persistent nGOR (OR 2.2, 95% CI 1.3-1.6, and OR 2.0, 95% CI 1.0-3.7, respectively). No significant association was found between nGOR and lung function or bronchial responsiveness. Persistent symptoms of nGOR contribute to the development of asthma and respiratory symptoms. New onset of OSA symptoms is higher among subjects with symptoms of nGOR. These findings provide evidence that nGOR may play a role in the genesis of respiratory symptoms and diseases.