A Clinical Study Used to Estimate Central Venous Pressure Non-invasively Using Occlusion Pressure

Mean absolute error (MAE) between non-invasive estimated central venous pressure (Doppler-coupled occlusion-pressure device) and invasive central venous pressure (central venous catheter)

Unit of Measure: mmHg For each participant, the non-invasive estimated CVP value derived from the Doppler-coupled occlusion-pressure measurement (5 technical replicates per session) will be compared to the simultaneous invasive CVP value obtained from the central venous catheter (standard of care). The primary reportable outcome is the MAE across participants, defined as the mean of the absolute difference between paired estimated and measured CVP values, expressed in mmHg. The pre-specified target is MAE ≤ 2 mmHg, consistent with the sample-size justification (n=25 to achieve 80% power assuming an acceptable margin of error of 2 mmHg, a Type I error rate of 5%, and an expected standard deviation of 4 mmHg from prior literature). Intermediate algorithm inputs including vein-occlusion pressure, initial vein diameter, Doppler-isolated venous waveform characteristics, internal jugular vein Doppler recording, and intrapatient and interpatient variability of device output.

Correlation between non-invasive estimated central venous pressure and invasive central venous pressure, adjusted for concurrent physiologic context variables abstracted from the electronic medical record

Unit of Measure: Pearson correlation coefficient (r), unitless, range -1.00 to +1.00 Strength of the linear association between the non-invasive estimated CVP (Doppler-coupled occlusion-pressure device) and simultaneous invasive CVP (central venous catheter). The regression model will adjust for concurrent physiologic context variables abstracted from the EMR at the single study session - collected as standard of care, with no extra research procedures: heart rate, cardiac rhythm, respiratory rate, non-invasive and arterial-line blood pressure (systolic, diastolic, MAP), SpO2, ETCO2, awRR, mixed venous oxygen saturation, stroke volume, cardiac output, and intracardiac chamber pressures. Only readily available EMR parameters will be recorded; no procedures will be added to obtain missing data.