Transthoracic Echocardiography in Prone Patients With Acute Respiratory Distress Syndrome: A Feasibility Study

Abstract

Objectives: Patients with acute respiratory distress syndrome are at risk for developing cardiac dysfunction which is independently associated with worse outcomes. Transthoracic echocardiography is an ideal imaging modality for goal-directed assessment and optimization of cardiac function and volume status. Prone positioning, while demonstrated to improve oxygenation, offload the right ventricle, and reduce short-term mortality in acute respiratory distress syndrome, has previously precluded transthoracic echocardiography on these patients. The purpose of this study was to assess the ability to perform focused transthoracic echocardiography examinations on acute respiratory distress syndrome patients in the prone position.

Design: We performed a cross-sectional study of critically ill patients hospitalized for acute respiratory distress syndrome due to coronavirus disease 2019.

Setting: This study was conducted in medical and surgical intensive units in a tertiary hospital.

Patients: We examined 27 mechanically ventilated and prone patients with acute respiratory distress syndrome due to coronavirus disease 2019. Participants were examined at the time of enrollment in an ongoing clinical trial (NCT04306393), and no patients were excluded from echocardiographic analysis.

Interventions: None.

Measurements and main results: We were able to perform transthoracic echocardiography and obtain satisfactory images for quantitative assessment of right ventricular function in 24 out of 27 (88.9%) and left ventricular function in 26 out of 27 (96.3%) of patients in the prone position, including many who were obese and on high levels of positive end-expiratory pressure (≥ 15 cm H₂O).

Conclusions: Transthoracic echocardiography can be performed at the prone patient's bedside by critical care intensivists. These findings encourage the use of focused transthoracic echocardiography for goal-directed cardiac assessment in acute respiratory distress syndrome patients undergoing prone positioning.

Keywords: acute respiratory distress syndrome; coronavirus disease 2019; critical care; prone; transthoracic echocardiography; ultrasound.

Figure 1.

Patient positioning for prone transthoracic echocardiography, with the left shoulder slightly elevated by a pillow support. To obtain the apical four-chamber view, the transducer is placed along the left anterior axillary line at the fourth to fifth intercostal space with the indicator directed posteriorly (A; blue arrow). To obtain a lateral inferior vena cava view, the transducer is placed between the right anterior and midaxillary lines at the fifth to sixth intercostal space with the indicator directed toward the patient’s head (B; blue arrow).

Figure 2.

Assessments of right ventricular (RV) function performed on a patient in the prone position including apical four-chamber view (A; Supplemental Video 1, Supplemental Digital Content 1, http://links.lww.com/CCX/A256; legend, Supplemental Digital Content 6, http://links.lww.com/CCX/A261) for comparison of chamber sizes (A), tricuspid annular plane systolic excursion (B), RV peak systolic tricuspid annulus velocity (C), color Doppler across the tricuspid valve showing a regurgitant jet (D; Supplemental Video 2, Supplemental Digital Content 2, http://links.lww.com/CCX/A257; legend, Supplemental Digital Content 6, http://links.lww.com/CCX/A261), continuous-wave Doppler of the same regurgitant jet to obtain the tricuspid regurgitant peak gradient (E), and lateral inferior vena cava (IVC) view for measurement of IVC diameter and distensibility/collapsibility index (F). BPM = beats per minute, PG = peak gradient, Vel = velocity.

Figure 3.

Assessments of left ventricular (LV) function performed on a patient in the prone position including mitral annular plane systolic excursion (A), pulsed-wave Doppler of the mitral inflow (E and A waves) (B), pulsed-wave tissue Doppler of the mitral annular velocities (e′ and a′) (C), and pulsed-wave Doppler of the LV outflow tract velocity time integral (D). BPM = beats per minute, max PG = maximum peak gradient, mean PG = mean peak gradient, PG = peak gradient, Vel = velocity, Vmax = maximum velocity, Vmean = mean velocity, VTI = velocity time integral.

Figure 4.

Agitated saline bubble echocardiography study performed on a patient in the prone position (Supplemental Video 3, Supplemental Digital Content 3, http://links.lww.com/CCX/A258; legend, Supplemental Digital Content 6, http://links.lww.com/CCX/A261). Injection of agitated saline caused opacification of the right ventricular (A) without the appearance of bubbles in the left heart (B), indicating absence of intracardiac shunting. BPM = beats per minute.

Figure 5.

Comparison of apical four-chamber views obtained on the same patient while positioned supine (A; Supplemental Video 4, Supplemental Digital Content 4, http://links.lww.com/CCX/A259; legend, Supplemental Digital Content 6, http://links.lww.com/CCX/A261) and prone (B; Supplemental Video 5, Supplemental Digital Content 5, http://links.lww.com/CCX/A260; legend, Supplemental Digital Content 6, http://links.lww.com/CCX/A261). Images were acquired within a 24-hr period. BPM = beats per minute.