[Hypercapnia under controlled mechanical ventilation in patients with high-risk acute pulmonary thromboembolism]

Objective: To evaluate the variation of arterial partial pressure of carbon dioxide (PaCO₂) in patients with high-risk pulmonary embolism under mechanical ventilation. Methods: We retrospectively analyzed the cases of high-risk pulmonary embolism who underwent intravenous thrombolysis in Peking Union Medical College Hospital from January 1, 2012, to May 1, 2022. The enrolled patients were divided into a mechanical-ventilated group and an active-breathing group according to whether they received invasive mechanical ventilation or not. The level of PaCO₂ under active breathing between the two groups, the changes in PaCO₂ before intubation, after intubation and after thrombolysis in the mechanical-ventilated group were compared. The 14-day all-cause mortality of the two groups was calculated and compared. Results: A total of 49 patients with high-risk pulmonary embolism were enrolled, including 22 patients in the mechanical-ventilated group and 27 patients in the active-breathing group. Before intubation, PaCO₂ in both groups was lower than normal without statistically significant difference between the two groups. After effective thrombolysis therapy, PaCO₂ in both groups recovered to the normal range. In the mechanical-ventilated group, PaCO₂ significantly increased 11-147 min after intubation and returned to the normal range after thrombolysis therapy. The 14-day mortality in the mechanical-ventilated group was 54.5%, while all patients in the active-breathing group survived. Conclusions: Under mechanical controlled ventilation, patients with high-risk pulmonary embolism could represent hypercapnia which resolved after effective thrombolytic therapy. In mechanical ventilated patients with sudden-onset hypoxemia and hypercapnia, the possibility of high-risk pulmonary embolism should be considered.