Blood Pressure Monitoring Accuracy in Patients Undergoing Lung Surgery With One-Lung Ventilation Using an Arm Cuff and Arterial Line

This is a prospective observational study designed to evaluate the clinical accuracy and reliability of non-invasive blood pressure (NIBP) monitoring in adult patients undergoing video-assisted thoracoscopic surgery (VATS) with one-lung ventilation (OLV). The accuracy of NIBP will be assessed by comparing it to invasive arterial blood pressure (IABP), which is considered the reference standard. The comparison will be performed using error grid analysis, a method that not only quantifies measurement differences but also categorizes the clinical risk of those discrepancies.

During VATS procedures, one lung is intentionally deflated to improve surgical access, which alters thoracic pressures, ventilation dynamics, and cardiovascular physiology. These changes may affect the accuracy of peripheral blood pressure measurements obtained using an arm cuff. Previous evaluations of NIBP in surgical patients have primarily relied on Bland-Altman analysis, which measures statistical agreement but does not assess the clinical consequences of disagreement between methods.

Error grid analysis overcomes this limitation by mapping paired NIBP and IABP values into predefined clinical risk zones (A-E), based on their potential to affect treatment decisions. Zone A represents measurements with no risk of causing inappropriate treatment, while Zones B through E indicate increasing levels of clinical risk due to measurement error.

In this study, NIBP and IABP measurements will be recorded simultaneously approximately every 20 minutes throughout surgery. The percentage of measurements that fall within each error grid zone will be calculated. If fewer than 90% of the paired measurements fall within Zone A, NIBP will be considered insufficiently reliable for use without concurrent invasive monitoring in this clinical context.

A pilot study of five patients was used to estimate the intracluster correlation coefficient and design effect, which informed the final sample size calculation. Based on these preliminary data, a total sample size of 90 patients is estimated to provide adequate statistical power to evaluate the primary outcome with 95% confidence and a 5% margin of error.

The study will also collect intraoperative data that may influence blood pressure measurement accuracy, such as the use of vasoactive infusions. These data may help identify subgroups in which NIBP is more or less reliable during one-lung ventilation.

The results of this study may help refine intraoperative monitoring strategies and potentially reduce unnecessary use of invasive blood pressure lines in selected thoracic surgical patients, improving both safety and comfort while maintaining clinical reliability.

• Distribution of Paired Systolic Blood Pressure Measurements Across All Error Grid Zones (A-E) [Срок оценки: Intraoperative period (measurements taken every 20 minutes during surgery)]
• Distribution of Paired Mean Arterial Pressure (MAP) Measurements Across All Error Grid Zones (A-E) [Срок оценки: Intraoperative period (measurements taken every 20 minutes during surgery)]
• Effect of Antihypertensive Medication Use on the Accuracy of Systolic NIBP Measurements [Срок оценки: Intraoperative period (measurements taken every 20 minutes during surgery)]
• Effect of Antihypertensive Medication Use on the Accuracy of Mean Arterial Pressure (MAP) NIBP Measurements [Срок оценки: Intraoperative period (measurements taken every 20 minutes during surgery)]