Usefulness of lung ultrasound for early detection of hospital-acquired pneumonia in cardiac critically ill patients on venoarterial extracorporeal membrane oxygenation

Abstract

Background: Hospital-acquired pneumonia (HAP) is the most common and severe complication in patients treated with venoarterial extracorporeal membrane oxygenation (VA ECMO) and its diagnosis remains challenging. Nothing is known about the usefulness of lung ultrasound (LUS) in early detection of HAP in patients treated with VA ECMO. Also, LUS and chest radiography were performed when HAP was suspected in cardiac critically ill adult VA ECMO presenting with acute respiratory failure. The sonographic features of HAP in VA ECMO patients were determined and we assessed the performance of the lung ultrasound simplified clinical pulmonary score (LUS-sCPIS), the sCPIS and bioclinical parameters or chest radiography alone for early diagnosis of HAP.

Results: We included 70 patients, of which 44 (63%) were independently diagnosed with HAP. LUS examination revealed that color Doppler intrapulmonary flow (P = 0.0000043) and dynamic air bronchogram (P = 0.00024) were the most frequent HAP-related signs. The LUS-sCPIS (area under the curve = 0.77) yielded significantly better results than the sCPIS (area under the curve = 0.65; P = 0.004), while leukocyte count, temperature and chest radiography were not discriminating for HAP diagnosis.

Discussion: Diagnosis of HAP is a daily challenge for the clinician managing patients on venoarterial ECMO. Lung ultrasound can be a valuable tool as the initial imaging modality for the diagnosis of pneumonia. Color Doppler intrapulmonary flow and dynamic air bronchogram appear to be particularly insightful for the diagnosis of HAP.

Keywords: Color Doppler intrapulmonary flow; Doppler color lung ultrasound; Dynamic air bronchogram; Hospital-acquired pneumonia; Intensive care unit; Lung ultrasound; Venoarterial extracorporeal membrane oxygenation.

Fig. 1

A Color Doppler lung ultrasound in the consolidated left lower lobe in a 54-year-old patient without pneumonia on venoarterial extracorporeal membrane oxygenation. The extracorporeal membrane oxygenation was initiated 2 days before and pneumonia was ruled out by a bronchoalveolar lavage retrieving 2.10² orophayngeal flora. Color signals are diffuse and changing resulting from interferences caused by respiratory movements and heart beats. Corresponding to Video S1A (Additional File 1). B Color Doppler intrapulmonary flow detected in the consolidated right lower lobe of a 43-year-old patient with pneumonia on venoarterial extracorporeal membrane oxygenation. The extracorporeal membrane oxygenation was initiated 12 days before for a cardiogenic shock and pneumonia was confirmed by a bronchoalveolar lavage retrieving 10⁴ Escherichia coli. The blood flow in a vessel is seen as a color signal persisting in the same location during the respiratory cycle with a tubular, curvilinear, or branching distribution on real-time images. When blood flow signals are detected, pulse-wave Doppler can identify their spectral waveform.¹⁹ Corresponding to Video S1B (Additional File 2). C Dynamic air bronchogram in a 79-year-old patient with pneumonia on venoarterial extracorporeal membrane oxygenation. The extracorporeal membrane oxygenation was initiated 5 days before for a cardiogenic shock and pneumonia was confirmed by a bronchoalveolar lavage retrieving 6.10⁶ Hafnia alvei. Corresponding to Video S1C (Additional File 3)

Fig. 2

Receiver operating characteristic (ROC) curves of simplified Clinical Pulmonary Infection Score and Lung ultrasound-simplified Clinical Pulmonary Infection Score. LUS = lung ultrasound; sCPIS = simplified Clinical Pulmonary Infection Score