Invasive pressure monitoring (arterial blood pressure via arterial catheter and central venous pressure via central venous catheter) is fundamental to clinical decision-making in intensive care. Treatment with vasopressors, fluids, and nursing interventions depends on accurate measurements. Because pressure transducers are hydrostatic, even small levelling errors can produce clinically relevant deviations (approximately 1 mmHg per 1.3 cm of vertical misplacement). Such errors may contribute to inappropriate therapy, for example under-recognition of hypotension, unnecessary vasopressor escalation, or missed venous congestion.

This prospective, multicenter, blinded observational study will quantify transducer levelling deviations during routine ICU care and evaluate whether clinically relevant deviations are associated with treatment decisions. Adult mechanically ventilated ICU patients with an arterial catheter, a central venous catheter, and ongoing vasopressor therapy will be included at hospitals in Västra Götalandsregionen, Sweden. Two blinded reference lines/sensors will be placed at predefined physiological zero levels for MAP and CVP and connected in parallel to the patient monitoring system. Continuous deviation (mmHg) between the clinical transducer position and the blinded reference level will be recorded for 8 hours while clinical staff remain unaware of the reference setup. MAP/CVP-related treatment decisions (e.g., vasopressor adjustments, fluid therapy, and nursing interventions) will be recorded with timestamps.

The study will provide real-world data on the magnitude and frequency of invasive pressure transducer misalignment in daily ICU practice and its potential relationship to patient management.

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

The study population consists of adult (≥18 years) critically ill, mechanically ventilated ICU patients receiving routine invasive arterial blood pressure and central venous pressure monitoring, often under sedation and vasoactive support.

De-identified individual participant data underlying the results will be shared on reasonable request. Shared data will be limited to variables necessary to reproduce the primary analyses and will not include any direct identifiers.

SD: 2028-01-01 ED: 2033-12-31

Access to de-identified individual participant data will be provided to qualified researchers upon reasonable request. Requests must include a brief research proposal and a data management plan. Data will be shared under a data use agreement that prohibits re-identification of participants and limits use to the approved purpose.