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Study Affirms Benefits of Noninvasive Technology in Surgery

July 14, 2008

The clinical evaluation published in the British Journal of Anaesthesia reveals Masimo's new PVI measurement allows noninvasive, automated, and continuous monitoring of the variation in the pulse oximeter waveform amplitude during respiration.


IRVINE, CA /PRNewswire-FirstCall/ -- Masimo, the inventor of Pulse CO-Oximetry and Measure-Through-Motion-and-Low-Perfusion Pulse Oximetry, announced that a new clinical study, published in the June 2008 issue of the British Journal of Anaesthesia, concluded that under the study protocol Masimo's PVI measurement "can predict fluid responsiveness in mechanically ventilated patients under general anesthesia." PVI is a new measurement available in the Masimo Rainbow SET technology platform that allows noninvasive, automated, and continuous monitoring of the variation in the pulse oximeter waveform amplitude during respiration.

During surgery, one of the biggest challenges anesthesiologists face is deciding whether to administer fluid to increase the cardiac index (the amount of blood the heart pumps each minute) and maintain an adequate delivery of oxygen to the body. However, multiple studies have shown that traditional invasive measurements are only 50% to 60% accurate at predicting an improvement in the cardiac index after volume administration. Administration of unnecessary fluid should be avoided because it is associated with increased morbidity and mortality. Newer invasive measurements based on dynamic changes during the respiratory cycle have shown improved accuracy at predicting fluid responsiveness, but market adoption has been slow due to complexity and cost. Therefore, a noninvasive method to accurately assess fluid responsiveness and guide fluid administration would provide tremendous value to clinicians and patients alike.

In the British Journal of Anaesthesia study, a patient was defined as a "responder" if their cardiac index increased by 15% or more after administration of 500 ml of fluid. If the cardiac index increased <15% after volume administration, the patient was defined as a "nonresponder." Of the 25 patients evaluated in the study, 16 were considered responders and 9 were considered nonresponders. PVI showed a similar accuracy (0.93 area under the curve, AUC) at predicting fluid responsiveness when compared with pulse pressure variation from an invasive arterial catheter (0.94 AUC) and superior accuracy when compared with central venous (0.42 AUC) or pulmonary capillary wedge pressure (0.40).

"PVI demonstrated high accuracy in discriminating fluid responders from nonresponders, providing a unique opportunity to better manage a patient's fluid volume to optimize cardiac performance and organ perfusion," stated Maxime Cannesson, M.D., lead researcher and anesthesiologist at Louis Pradel Hospital in Lyon, France. "Fourteen of the sixteen patients who responded to fluid administration with a cardiac index increase of 15% or more had a PVI value of >14% before volume administration. All nine patients who did not respond to fluid administration with a cardiac index increase of 15% or more had a PVI value of <14% before volume administration."

According to a recent clinical study published in Critical Care, monitoring pulse pressure variation with an arterial catheter showed an ability "to decrease the duration of hospital stay, mechanical ventilation, and post-operative morbidity in patients undergoing high-risk surgery." While pulse pressure variation from an arterial pressure catheter is considered the gold standard for assessing fluid responsiveness, only a small minority of patients receive this type of catheter during surgery due to its invasiveness, complexity, and risk. In Dr. Cannesson's study, Masimo PVI showed similar accuracy as pulse pressure variation at predicting fluid responsiveness but offers clinicians an easy and noninvasive assessment of fluid responsiveness in any patient undergoing surgery by simply using their existing noninvasive Masimo SpO2 sensor with Masimo Rainbow SET monitors.

Joe E. Kiani, Chairman and CEO of Masimo, stated, "The excellent work of Dr. Cannesson and colleagues adds to the growing body of evidence supporting the use of PVI as a new standard of care to optimize fluid status in patients both in the operating room and at the bedside. We are happy to see that yet another one of our inventions has the potential to improve outcomes and increase safety for patients."

About Masimo
Masimo develops innovative monitoring technologies that significantly improve patient care, helping solve "unsolvable" problems. In 1995, the company debuted Measure-Through-Motion-and-Low-Perfusion Pulse Oximetry, known as Masimo SET, which virtually eliminated false alarms and increased pulse oximetry's ability to detect life-threatening events. More than 100 independent and objective studies demonstrate Masimo SET provides the most reliable SpO2 and pulse rate measurements even under the most challenging clinical conditions, including patient motion and low peripheral perfusion. In 2005, Masimo introduced Masimo Rainbow SET, a breakthrough noninvasive blood constituent monitoring platform that can measure many blood constituents that previously required invasive procedures. Masimo Rainbow SET continuously and noninvasively measures total hemoglobin (SpHb), oxygen content (SpOC), carboxyhemoglobin (SpCO), methemoglobin (SpMet), and PVI, in addition to oxyhemoglobin (SpO2), pulse rate, and perfusion index, allowing early detection and treatment of potentially life-threatening conditions. Founded in 1989, Masimo has the mission of "Improving Patient Outcomes and Reducing Cost of Care by Taking Noninvasive Monitoring to New Sites and Applications."


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