Computed Tomography Yield and Predictors of Pulmonary Embolism in Mechanically Ventilated Patients-A Retrospective Study.

Abstract

The reported prevalence of pulmonary embolism (PE) detected during intensive care varies substantially. Computed tomography pulmonary angiography (CTPA) is the diagnostic reference method, but assessing pre-test probability and finding distinct indications for CTPA from clinical observations is difficult in mechanically ventilated critically ill patients. To describe the rate of positive diagnostic outcome (yield) from CTPA exams performed on PE suspicion and to identify predictors in the free text motivational reasons from the referring clinician and among selected patient variables during intensive care for other conditions. CTPA exams and reports in adult, mechanically ventilated patients referred from two intensive care units during a 5-year period were compared to the radiology order content and to data collected from medical records. The association between a positive exam and five arbitrarily defined reasons for ordering the exam as well as selected patient variables was assessed using multivariable logistic regression. Among 1113 thoracic computed tomography exams, 243 were CTPA ordered on clinical PE suspicion, yielding 52 (21% [95% CI: 17-26]) positives. Reasons "Elevated D-dimer" and "Undefined clinical suspicion" were significantly associated with a positive exam. However, none of the selected patient variables was significantly associated with a CTPA finding of PE. The diagnostic yield of clinical CTPA exams for suspected PE in mechanically ventilated patients fell within a range commonly cited for suspected acute PE in emergency department populations, but its association with clinical signs described in the CTPA order and with selected patient variables was low. The report describes a single center experience, including 2 years of the COVID-19 pandemic, with computed tomography pulmonary angiography performed to evaluate suspected pulmonary embolism in mechanically ventilated ICU cases. An elevated D-dimer as well as high degree of clinical suspicion were associated with a positive pulmonary embolism finding on the radiological examination.