The main goal of Intensive Care Unit (ICU) physicians is to ensure cellular oxygenation
by maintaining adequate organ perfusion in their patients. Stroke volume is a major
determinant of tissue perfusion and therefore a key parameter to monitor in patients with
hemodynamic instability. Left Ventricular Outflow Tract (LVOT) Velocity-Time Integral
(VTI) measured using pulsed wave Doppler is widely used as an estimation of stroke volume
to assess hemodynamic modifications. This value reflects the stroke distance, which
varies proportionately to stroke volume in case of hemodynamic variations resulting from
therapeutic interventions (fluid administration, vasoactive drugs...) or disease
processes. An increase in stroke volume (or LVOT VTI) is expected in response to fluid
administration and attests for its efficacy. A lack of increase indicates that the
cardiovascular system is no longer fluid-responsive, and that fluid administration is not
improving tissue perfusion and creates congestion. Therefore, measuring aortic VTI should
be a competence required for every ICU physician. However, international ICU guidelines
on echocardiography do not consider LVOT VTI measurement as a basic skill but rather as a
competence of advanced operators. More recently, the European Society of Intensive Care
Medicine published expert recommendations on echocardiography, setting the evaluation of
LVOT VTI as basic skill but with a weak recommendation, lacking published evidence to
support this statement.
The main difficulty in measuring LVOT VTI is obtaining an adequate apical 5-chamber view.
Recently, research in artificial intelligence (AI) applied to medical imaging constituted
a breakthrough in the acquisition of images. UltraSight is a company specialized in AI
applied to echocardiography. Their software is based on neural network using machine
learning to analyse extremely precisely the image obtained by an operator. The software
indicates to the operator in real time on-screen how to optimize the image by mobilizing
the probe until the desired view is correctly obtained, with the best quality.
The main objective of the present study is to characterize and to quantify the
reliability and reproducibility of LVOT VTI measurements by comparing the measures
obtained by minimally trained operators and experts, using an ultrasound platform
equipped with real-time AI-based guidance (UltraSight). If interchangeability of
minimally trained operators and expert measurements can be demonstrated, this will
constitute a strong basis to upgrade the measurement of LVOT VTI as a basic competence in
critical care ultrasound. The secondary objectives are to assess the concordance of
therapeutic decisions made by the ICU clinician in charge of the patient (i.e.: continue
or interrupt fluid administration) based on the VTI variation obtained by the
minimally-trained operator, and that based on the VTI variation obtained by the expert,
the agreement of the absolute value of the measure of LVOT VTI obtained by the minimally
trained operators and the experts, the correlation between the measures of the VTI
variation (% change following a fluid challenge of 250 mL or a passive leg-raising test)
between the minimally-trained operators and those obtained by experts.
