The pocket echocardiograph: a pilot study of its validation and feasibility in intubated patients

The clinical use of miniaturized echocardiograph devices is expanding due to the potential to rapidly assess cardiac function in the critically ill patient. Novice echocardiographers have used the pocket echocardiograph (PE) to estimate ejection fraction in ambulatory patients, but have not evaluated intubated patients. We hypothesize that a novice echocardiographer can use PE to acquire interpretable cardiac images, and provide an accurate tool for estimating ejection fraction.

Subjects scheduled for cardiac surgery underwent blinded transesophageal echocardiography (TEE) and PE during a hemodynamically stable period after endotracheal intubation prior to incision. A single cardiology fellow acquired all PE images. The fellow and an experienced echocardiographer interpreted PE studies offline in a blinded fashion, visually estimating ejection fraction and assigning an image quality grade. Comparisons were made to the TEE study.

Subjects (n = 22) were 81% male; age 69 ± 9 years, and had a mean ejection fraction of 51% ± 10.0%. Parasternal images were adequate in the vast majority of patients (77%), limited in 14%, and unacceptable in 9%, while apical (41%, 45%, and 14%) and subcostal (36%, 32%, and 32%) image quality was inferior. Ejection fraction showed fair correlation, bias, and limits of agreement for the fellow's interpretation (r = 0.50, 4.9%, ± 20.7%), with stronger association for the experienced echocardiographer (r = 0.76, 3.3%, ± 16.6%).

A novice echocardiographer using PE can acquire interpretable images in the majority of intubated patients. Novice and expert echocardiographers can reasonably estimate ejection fraction using PE. PE may allow novice echocardiographers to rapidly assess cardiac function in intubated patients.