Transducer Levelling Errors in Everyday ICU Practice - A Multicentre Blinded Observational Study

This is a prospective, multicenter, blinded observational study evaluating the accuracy of invasive pressure transducer levelling for arterial pressure (mean arterial pressure, MAP) and central venous pressure (CVP) during routine intensive care. Adult mechanically ventilated ICU patients with an indwelling arterial catheter and central venous catheter receiving vasopressor therapy are observed without any protocol-mandated changes to standard clinical care.

To quantify levelling deviations without influencing clinical behavior, a parallel reference measurement setup is connected to the existing monitoring system. Two fluid-filled reference lines are connected in parallel to the pressure dome used for invasive monitoring and secured to the chest wall at the fourth intercostal space at half of the anteroposterior thoracic diameter, one on each side of the chest. This configuration allows continuous estimation of vertical deviation (mmHg) between the clinical transducer position and a predefined physiological reference level. During lateral positioning, deviation is calculated using the midpoint between the two reference lines as the reference. Reference lines are covered with dressings to maintain blinding of clinical staff to the reference levels.

Physiological waveforms and calculated deviations are recorded continuously for an 8-hour monitoring period for each participant. In parallel, treatment actions plausibly influenced by interpretation of MAP or CVP (including vasopressor titration, fluid administration or removal, and nursing interventions related to positioning or transducer handling) are documented with timestamps to allow temporal association analyses. Relevant contextual variables are collected to support interpretation of deviations and clinical responses.

Data quality is ensured through predefined measurement procedures, continuous digital waveform acquisition, synchronization of reference and clinical signals, and post hoc review of signal integrity. Periods affected by technical artifacts or signal loss are flagged according to predefined criteria. Data segments that are missing, uninterpretable, or invalid due to technical failure are treated as missing and excluded from analyses, without imputation.

The study is designed to quantify the magnitude and frequency of invasive pressure transducer misalignment during routine ICU care and to explore whether clinically relevant deviations are associated with contemporaneous treatment decisions, with the aim of informing patient safety and quality improvement initiatives.

Inclusion criteria

• Age ≥18 years
• ICU admission
• Mechanically ventilated
• Arterial catheter for MAP
• Central venous catheter for CVP
• Ongoing vasopressor therapy

Exclusion criteria

• Severe hemodynamic or respiratory instability
• Contraindications for lateral positioning
• Expected survival <24 hours