Accuracy of Non-invasive Blood Pressure Monitoring at the Wrist in Obese Patients

Arterial blood pressure (ABP) monitoring is a corner stone in perioperative management. Recently, tight intraoperative individualized control of systolic blood pressure (SBP) (within 10% of baseline reading) was reported to reduce the risk of postoperative organ dysfunction in high risk patients undergoing abdominal procedures. However, proper control of SBP requires accurate measurement of ABP.

The gold standard for ABP measurement is through a catheter placed in an artery. Being an invasive, measurement of BP through an arterial catheter is restricted to patients with rapid major fluid shifts. Many indirect methods are used for measurement of ABP. Oscillometric blood pressure (OBP) monitoring is considered the standard non-invasive monitor for use in most clinical situations. In OBP monitor, a pressure transducer located in the cuff senses the series of small oscillations heart-beat induced pulse volume changes. These oscillations are detected during deflation of the cuff pressure from above the SBP to diastolic blood pressure (DBP).

The upper arm is the standard location of application of the blood pressure cuff as it is aligned with the heart level regardless the patient position. In obese patients, OBP monitoring is considered superior to auscultatory method which is limited by faint auscultatory sounds. However, application of blood pressure cuff at the upper arm in this population is frequently limited by large arm circumference and asymmetrical arm contour. Thus, locating the cuff at the wrist might be a more feasible alternative for the upper arm. OBP monitoring at the wrist was previously compared to auscultatory measurement of ABP in non-surgical patients. A recent study investigated the accuracy of OBP at the upper forearm in obese patients. No data to the best of our knowledge validated OBP monitoring at the lower forearm in obese patients using invasive blood pressure monitor as a reference standard.

The aim of this work is to validate the wrist OBP monitor in obese patients and compare it to upper arm location (in accuracy, convenience, and trending) using invasive blood pressure monitor as a reference standard.

Inclusion criteria

• Adult patients (aged above 18 years)
• obese (with body mass index above 30 Kg/squared meter)

Exclusion criteria

• Peripheral vascular diseases
• Upper limb operations
• Upper limb scars
• Upper limb deep venous thrombosis
• Arrhythmias