The effect of continuous positive airway pressure on inferior vena cava collapsibility as measured by bedside ultrasound.

Objectives: The purpose of this study was to determine the impact of progressively increasing continuous positive airway pressure (CPAP) on measurements of the caval index (CI) using bedside ultrasound at the 3 common inferior vena cava (IVC) evaluation sites. Methods: This was a prospective, observational trial that included 165 healthy adults over 18 years old enrolled between February 2015 and May 2018. Measurements of the IVC were obtained during normal tidal respirations from the subxiphoid area in the long and short axis and from the right mid-axillary line in the long axis. Measurements were obtained in each of these locations at atmospheric pressure and with CPAP at 5, 10, and 15 cmH2O. The CI was then calculated for each of the 3 selected locations at each level of pressure. Results: As CPAP pressures increased from 0 to 15 cmH2O the CI measurements obtained at the lateral mid-axillary line did not show any statistically significant variation. There was a statistically significant difference (P < 0.001) when comparing measurements of the CI from the lateral mid-axillary line location to both anterior locations. As CPAP pressures increased, the CI calculated from the subxiphoid area in both the anterior short and anterior long axis orientations initially trended upwards at 5 cmH2O, then began to downtrend as the pressures increased to 10 and 15 cmH2O. Comparing the CI measurements from the anterior long and anterior short axis at 0, 5, 10, and 15 cmH2O, there was no statistically significant difference at any pressure (P > 0.05). Conclusion: When evaluating the IVC in a spontaneously breathing patient, measurements from an anterior orientation are preferred as the lateral mid-axillary view can underestimate CI calculations.

Comparison of four handheld point-of-care ultrasound devices by expert users.

BACKGROUND: Point-of-care ultrasound (POCUS) is rapidly becoming ubiquitous across healthcare specialties. This is due to several factors including its portability, immediacy of results to guide clinical decision-making, and lack of radiation exposure to patients. The recent growth of handheld ultrasound devices has improved access to ultrasound for many clinicians. Few studies have directly compared different handheld ultrasound devices among themselves or to cart-based ultrasound machines. We conducted a prospective observational study comparing four common handheld ultrasound devices for ease of use, image quality, and overall satisfaction. Twenty-four POCUS experts utilized four handheld devices (Butterfly iQ+™ by Butterfly Network Inc., Kosmos™ by EchoNous, Vscan Air™ by General Electric, and Lumify™ by Philips Healthcare) to obtain three ultrasound views on the same standardized patients using high- and low-frequency probes. RESULTS: Data were collected from 24 POCUS experts using all 4 handheld devices. No single ultrasound device was superior in all categories. For overall ease of use, the Vscan Air™ was rated highest, followed by the Lumify™. For overall image quality, Lumify™ was rated highest, followed by Kosmos™. The Lumify™ device was rated highest for overall satisfaction, while the Vscan Air™ was rated as the most likely to be purchased personally and carried in one's coat pocket. The top 5 characteristics of handheld ultrasound devices rated as being "very important" were image quality, ease of use, portability, total costs, and availability of different probes. CONCLUSIONS: In a comparison of four common handheld ultrasound devices in the United States, no single handheld ultrasound device was perceived to have all desired characteristics. POCUS experts rated the Lumify™ highest for image quality and Vscan Air™ highest for ease of use. Overall satisfaction was highest with the Lumify™ device, while the most likely to be purchased as a pocket device was the Vscan Air™. Image quality was felt to be the most important characteristic in evaluating handheld ultrasound devices.