Mechanisms of endothelin-1 elevation in chronic obstructive pulmonary disease patients with nocturnal oxyhemoglobin desaturation.
BACKGROUND
Nonapneic, oxyhemoglobin desaturation associated with sleep has been described in patients with chronic obstructive pulmonary disease (COPD). Hypoxemia stimulates endothelin-1 (ET-1) secretion. Once released, ET-1 can act locally to elicit sustained pulmonary artery vasoconstriction, bronchoconstriction and activation of alveolar macrophages.


OBJECTIVE
The aim of this study was to examine a possible correlation between ET-1 levels and nocturnal, nonapneic, oxyhemoglobin desaturation during sleep, in patients with COPD.


METHODS
We examined 48 COPD patients with formal polysomnography (EEG, ECG, airflow, respiratory muscle movement, oximeter) to detect the presence of nocturnal, nonapneic, oxyhemoglobin desaturation. Twelve of them were disqualified because of inadequate sleep or sleep apnea syndrome. Nineteen of them desaturated below a baseline sleep saturation of 90% for 5 min or more, reaching a nadir saturation of at least 85%. We collected arterial samples to measure ET-1 levels, after 5 min of the first period of desaturation, in each of the 19 patients. We also collected arterial samples in the morning, before the study, to measure baseline ET-1 levels in all patients.


RESULTS
Baseline arterial ET-1 levels during the day were very significantly higher in 'desaturator' COPD patients (2.058 +/- 0.252 pg/ml) compared to 'non-desaturator' COPD patients (1.382 +/- 0.159 pg/ml; p < 0.001). Also in 'desaturator' COPD patients ET-1, levels during the night were significantly higher (4.297 +/- 1.107 pg/ml) compared to those during the day (p < or = 0.001) and a significant negative correlation was observed between ET-1 levels and degree of desaturation (p < 0.0001, r = 0.9305).


CONCLUSIONS
According to our study we can conclude that (1) ET-1 levels are significantly higher in 'desaturator' COPD patients both during the day and during the night, and (2) ET-1 levels correlate negatively significant with the degree of the oxyhemoglobin desaturation. These findings are consistent with the hypothesis that ET-1 plays a very important role in the pathophysiological manifestations of COPD patients.
Trakada
G
G
Department of Internal Medicine, Division of Pulmonology, University of Patras Medical School, Patras, Greece.
Marangos
M
M
Spiropoulos
K
K
D000368:Aged; D019332:Endothelin-1 / Q000097:blood* / Q000502:physiology; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D008173:Lung Diseases, Obstructive / Q000097:blood / Q000503:physiopathology*; D008875:Middle Aged; D010108:Oxyhemoglobins / Q000032:analysis; D017286:Polysomnography; D012890:Sleep / Q000502:physiology*
D019332:Endothelin-1; D010108:Oxyhemoglobins