[Nocturnal and diurnal oxygen saturation in patients with chronic pulmonary embolism]

Little is known on oxygen saturation in patients with chronic pulmonary embolism. AIM OF THE STUDY WAS: Tto assess the occurrence and importance of oxygen desaturations (D) in these patients.

The study involved 58 normotensive patients with chronic pulmonary embolism (18 males, 40 females, mean age 60 years, range 22-87 years) and was carried out 6 weeks to 2 years after an acute pulmonary embolic event. During 24-hour pulse oximetry mean oxygen saturation (SpO2), and number and duration of desaturations (D), defined as at least a 6% drop of pSO2, below 88%, lasting a minimum of 8 s, were recorded. Simultaneously echocardiographic study and blood gases analysis was performed.

Desaturations were found in 39 (67.2%) patients, whereas 79% patients had pSO2 <95% in gasometry. 27 patients had both diurnal (06(00)-22(00)) and nocturnal (22(00)-06(00)) D, 9 patients only nocturnal D, and 3 patients only diurnal D. The number (14.7 vs 36.1) and duration (733.9 vs 1528 s) of D episodes were approximately 2 times greater at night than day. There were 18 (75%) desaturators among patients with pulmonary hypertension (defined as an echocardiographic tricuspid gradient >30 mmHg), and 21 (61.8%) desaturators among patients with chronic pulmonary embolism and without pulmonary hypertension. The patients with pulmonary hypertension had a lower mean SpO2 (p=0.005) and a lower number and duration of nocturnal (p=0.008, 0.03) and diurnal (p=0.008, 0.035) D.

A large number of D episodes were found in the patients with chronic pulmonary embolism, mostly at night and in the patients with pulmonary hypertension. It is unclear whether D merely reflects pulmonary vasculature embolization or whether they are capable of impacting development of chronic thromboembolic pulmonary hypertension on the basis of vicious circle. In the latter case the need for a long term oxygen therapy, or at least nighttime oxygenation, should be taken into account to slow down progression of the disease.