Noninvasive Blood Pressure Monitors: Considerations for Intensive Care Patients

Devices and methods that impact accurate monitoring for the critically ill
By: 
Namrata Sundaresan

 

May 22, 2006

Blood pressure measurement is a given for patients in the hospital, but for surgical or critically ill patients — in operating rooms, surgical recovery rooms, intensive care units, emergency departments and other critical care areas — frequent or continual blood pressure is imperative.

Due to the acuity of these patients' conditions and speed with which their conditions can change, trend information obtained from successive blood pressure measurements plays an important role in diagnosis. Approximately 114 million people visit U.S. emergency departments each year, with each visitor requiring a blood pressure reading at least once. Recently it’s been reported that approximately 65 million people in the U.S. are considered hypertensive, which represents a 30 percent increase in the last decade.

Blood pressure measurement is integral to the intensive care patient's vital signs and is used to screen for hypertension, estimate cardiovascular risk, and diagnose, manage, and treat acute and chronic medical conditions.

Blood pressure can be obtained by one of three following methods:

• Direct intra-arterial measurement is the gold standard of blood pressure measurement; however, it is the least used due to the high potential of infection and trauma.

• Indirect, noninvasive methods are most accepted. The most popular indirect, noninvasive technique is the use of a sphygmomanometer and auscultation.

• An alternative indirect noninvasive method is use of an automated device and oscillometric measurements.

For over 20 years, noninvasive blood pressure (NIBP) monitors have been extensively used in intensive care units to closely monitor patient's blood pressure. Despite the widespread use of automated blood pressure monitors, clinicians continue to deliberate over the accuracy and reliability of automated NIBP devices compared to other noninvasive methods of blood pressure determination. The blood pressure device most commonly used in the ICU is the sphygmomanometer.

A vital aspect in the use of NIBP devices is to use the correct cuff size. The American Heart Association (AHA) provides recommendations for appropriate cuff sizes based on upper-arm circumference that should be followed when using NIBP monitors. Using a cuff that is small will lead to erroneously high readings, and using a cuff that is too large will lead to low readings. The cuff width selected should equal 40 percent of the arm circumference. The table above shows AHA’s recommended bladder dimensions for blood pressure cuffs according to arm circumference.

The downside of NIBP monitoring is that certain conditions can prevent accurate determination of blood pressure. A large number of NIBP devices utilize oscillometric technology that is reliant on fairly regular cardiac rhythms to determine blood pressure; hence, irregular or rapid cardiac rhythms make it difficult to accurately determine blood pressure using NIBP devices because of the great beat-to-beat variability.

Also, excessive patient movement such as shivering, restlessness, or external movements such as from vehicles while on the move (in an ambulance), or a rapid-cycling ventilator can interfere with detection of cardiac oscillations by the NIBP monitor, leading to erroneous measurements.

Dollars and Cents

Noninvasive automated blood pressure monitors used in the ICU are stand-alone, preconfigured units that permit single or dual parameter vital signs monitoring. In 2005, revenues generated by the U.S automated blood pressure monitors market were $95.1 million, reflecting an estimated growth rate of 13.9 percent over 2004 revenues. This market is experiencing slow growth as a result of the cost containment issues in hospitals. With prices declining as much as five percent a year, revenue growth rate has been lagging behind the higher unit growth rates.

Declining prices make it more cost efficient for hospitals to purchase higher end multiparameter devices when they replace their low-end automated units. This trend toward integration is driven by cost efficiency rather than a push toward acquiring higher technology in hospitals. Other market influences include the trend toward shorter hospital stays and increased consolidation among the hospitals.

But the recent wave of sensor-based technologies is poised to change the parameters of NIBP in the intensive care departments. Technology innovation and new product innovations by companies such as Medwave, Healthstats, Tensys Medical, Triage Wireless, to name a few, are setting new industry standards.

Namrata Sundaresan is a senior research analyst at Frost & Sullivan. Since joining the consulting firm in December 2004, she has generated research services including the U.S. medical wireless ambulatory telemetry monitoring equipment markets, U.S. fetal and neonatal monitoring equipment markets and U.S. blood pressure monitoring markets. She can be reached at: nsundaresan@frost.com

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