In chronic heart failure (HF) patients, physical exercise induces an increase in pulmonary capillary pressure with the consequent development of pulmonary oedema [1]. This pathophysiological process accounts during exercise for a transient increase of plasma levels of brain natriuretic peptide (BNP) and a reduction in the alveolar-capillary diffusion capacity, the latter, however, mainly in patients with very severe HF [1]. In patients with less severe HF alveolar-capillary diffusion is preserved during active exercise albeit exercise-induced intrapulmonary fluid shifts have been postulated [1,2].

Ultrasound lung comets, also called B-lines, are hyperechoic artefacts perpendicular to the pleural line detectable by an echocardiographic probe on the chest, attributed to subpleural interlobular septal thickening due to the presence of liquid [3]. Lung comets evaluation is a simple, non-invasive and semi-quantitative method for determining the extravascular fluid content in the lung [4]. Lung comets are known to increase during short term high altitude exposure in healthy subjects [5] and during exercise in HF patients [6]. Moreover a clear correlation was found between the number of comets and both radiological and invasive signs of pulmonary congestion [7,8]. Furthermore, evaluation of comets was correlated with plasma BNP levels [6,9,10] and prognosis [11] in HF patients.

The purpose of the present study was to evaluate the temporal correlation between transient changes in lung diffusion, gas exchange, plasma BNP levels and lung comets during and after exercise in patients with moderate to severe HF. This information will allow a better understanding of exercise-induced intra-thoracic fluid movements and their consequence on gas exchange during and after exercise.