Echocardiography during Prone-Position Mechanical Ventilation in Patients with COVID-19: A Proposal for a New Approach.

To the Editor:

During the severe acute respiratory syndrome coronavirus-2 pandemic, patients with coronavirus disease 2019 pneumonia tend to deteriorate and develop acute respiratory distress syndrome. Most of these patients receive mechanical ventilation, and many may benefit from prone positioning as a lifesaving maneuver in the setting of severe hypoxemia, aiming to attempt to open the collapsed and congested parenchymal lung segments. These patients require detailed cardiocirculatory evaluation because of the effects of sedation and the high respiratory pressures that affect venous return and right ventricular (RV) performance. This evaluation often includes echocardiography.

It is known that mechanically ventilated patients generally do not present good ultrasound windows to allow high-quality echocardiography, because of the “curtain effect” of the left lung that reduces the ability of the ultrasound beam to penetrate to the heart and return to the transducer. Furthermore, echocardiography may be required during prone positioning. The “gold standard” solution to these issues is transesophageal echocardiography. Although transesophageal echocardiography performed in the prone position has been reported as a safe procedure, in our opinion, one limitation may be the position of the neck and head of the patient, which is laterally rotated and may make it difficult to introduce the transesophageal echocardiographic probe. Additionally, given the large number of patients requiring this type of evaluation and the number of devices available, transesophageal echocardiography is often a logistic challenge.

To overcome these technical issues, transthoracic echocardiography (TTE) may play an important role, as it is noninvasive, reproducible, and easily available. Unlike the technique for TTE in a prone patient reported by Ugalde et al., we performed TTE in prone-positioned patients during mechanical ventilation without the need to adopt the “swimming position” (extension of the left arm above the head) and without the need to elevate the left shoulder with pillows. We temporarily deflated the lower thoracic section of the air mattress to position the probe optimally to obtain the apical four-chamber view, taking advantage of the gravitational effect on the heart, causing it to slide closer to the chest wall. The operator is positioned to the left of the patient and uses his or her left hand to position the transducer. The only ultrasound window we could assess was the apical four-chamber view (Figure 1 ). This allows evaluation of many of the parameters included in the assessment of left ventricular and RV performance: left ventricular ejection fraction, mitral annular plane excursion, diastolic functional parameters (mitral valve and annular Doppler velocities), aortic valve Doppler flow velocity (by tilting the probe, we can obtain the apical five-chamber view), RV end-diastolic diameter and its ratio to left ventricular end-diastolic diameter, RV systolic performance by tricuspid annular plane systolic excursion, and pulmonary artery systolic pressure from the tricuspid regurgitation peak Doppler velocity.

Figure 1

The apical four-chamber view and ventricular diameter measurements.

We used this approach in eight patients to assess cardiac performance. In only one case was the quality of the ultrasound view poor, and this was in a patient with a markedly increased body mass index of 60 kg/m2.

In our experience during the current severe acute respiratory syndrome coronavirus-2 outbreak, prone-position TTE is feasible and provides sufficient information to monitor some basic aspects of cardiac performance.