Endothelin-1 levels in interstitial lung disease patients during sleep

Hypoxemia stimulates endothelin-1 (ET-1) secretion. The reduction in alveolar ventilation during sleep is considered sufficient to account for the hypoxemia observed in patients with respiratory diseases. The aim of this study was to evaluate the arterial ET-1 levels and their relationship with pulmonary hypertension in patients with interstitial lung disease (ILD) during sleep. We examined 38 patients with ILD using formal polysomnography (electroencephalogram, electrocardiogram, airflow, respiratory muscle movement, oximeter) to detect the presence of nocturnal, nonapneic, oxyhemoglobin desaturation. All patients desaturated below a baseline sleep saturation of 90% for 5 minutes or more, reaching a nadir saturation of at least 85%. Each patient had already undergone right heart catheterization with a Swan-Ganz catheter for measuring hemodynamic parameters. Sampling of arterial blood from a radial artery line for determination of blood gases and ET-1 values was performed simultaneously, after 5 minutes of the first desaturation. At rest, arterial ET-1 levels were higher in ILD patients (1.73 +/- 0.37 mgr/mL) than in controls (1.22 +/- 0.15 mgr/mL) ( p < 0.001). Also, the patients with pulmonary hypertension (Pa > 20 mm Hg) presented significantly higher arterial ET-1 levels (1.86 +/- 0.32 mgr/mL) than those without pulmonary hypertension (1.31 +/- 0.13 mgr/mL) ( p < 0.001). Arterial ET-1 levels were significantly correlated with mean pulmonary arterial pressure (PAP) (r = 0.749, p < 0.001), and arterial oxygen partial pressure (PaO2) (r = 0.79, p < 0.001). At sleep, during desaturation, arterial ET-1 levels significantly increased in all patients (2.46 +/- 0.13 mgr/mL) as compared with resting values ( p < 0.001). Arterial ET-1 levels were significantly correlated with PAP (r = 0.657, p < 0.001) and PaO2 (r = 0.93, p < 0.001). According to our study, arterial ET-1 is markedly increased in ILD patients, especially in those with pulmonary hypertension.