Transthoracic echocardiogram by protocol apical-subcostal in prone position during invasive mechanical ventilation
Authors: Del Castillo Gordillo C , Appiani Florit F , Begazo Gonzales A , Yanez Vidal F , Mora Valdes R , Avila Cisternas C , Garcia Medina A , Luque Gonzales M , Ibanez Mora A , Alfaro Diaz M 
Published: April 2021

Abstract

Funding Acknowledgements
Type of funding sources: None.

Introduction
During COVID-19 pandemic reports increased of transthoracic echocardiography (TTE) in prone and invasive mechanical ventilation (IMV), mostly describing four and five chamber apical views, and inferior vena cava (IVC) by lateral IVC window (from right side of the patient).

Purpose
Evaluate quality of images obtained with protocol of apical-subcostal TTE in patients with IMV and prone position.

Methods
Prospective study, between August and December 2020, in adults who required prone position during IMV. After placing the patient in the prone position, left arm was extended overhead, and a pillow was placed only under the left hemithorax to elevate and facilitate the apical window and space below the patient for subcostal window. Operator stands on the left side of the patient and takes images with the transducer in your right hand, starting with apical window and subsequently subcostal window. Apical views were apical four, two and three-chambers, to obtain function parameter of right and left ventricle (LV), evaluation of aortic valve, mitral and tricuspid valve. Subcostal views were four cardiac chambers and IVC, to obtain qualitative ventricle function, presence of pericardial effusion, and volume status and estimation of pulmonary pressure (together to peak systolic tricuspid pressure gradient from apical views). The images were acquired by cardiologist, then were saved, and finally evaluated by two echocardiography cardiologist experts.

Results
16 ETTs were performed. Male gender and obesity predominate. Positive end-expiratory pressure average was 10.8 cm of water. One patient cannot be assessed by absence of acoustic window and the rest (n = 15) were analyzed with experts. It was achieved a four-chamber apical view in 100% (n = 15), a two-chambers apical view in 60% (n = 9) and a three-chambers apical view in 100% (n = 15). It was possible to assess global function of the LV in 100% (n = 15), LV segmental function in 53% (n = 8), LV outflow tract velocity time integral in 100% (n = 15) and tricuspid annular plane systolic excursion in 100% (n = 15). Pulsed wave doppler of mitral valve in 100% (n = 15) and tissue doppler of lateral mitral valve annulus 100% (n = 15). Continuous wave doppler of aortic valve in 100% (n = 15) and tricuspid valve in 93% (n = 14). Subcostal four-chamber 80% (n = 12), presence pericardial effusion 100% (n = 15) and IVC 93% (n = 14). Non-complications associated with obtaining the position.

Conclusions
ETT in the prone position during IMV was possible and interpretable images were achieved. The position described allows assessment by apical and subcostal views at the same time and position of the operator and the patient. In addition, it was a safe technique, and the position was easy to be incorporated by the health team. Limitations were obtaining the two-chamber apical view and evaluation of segmental alterations of the LV. Better validation requires a larger sample.