IRVINE, Calif., April 21, 2011 /PRNewswire/ -- Masimo (NASDAQ: MASI) announced today that a new study published in this month's issue of the peer-reviewed journal, Annals of Emergency Medicine, demonstrates that noninvasive Masimo carboxyhemoglobin (SpCO®) measurements provide an "effective means for screening at-risk populations for CO poisoning" with "acceptable bias and precision" compared to invasive blood gas analysis. The prospective diagnostic accuracy study is more than ten times larger than any other published SpCO accuracy study to date and provides a strong rationale for clinical use of SpCO in the evaluation of emergency department (ED) patients.(1)
Carbon monoxide (CO) poisoning is a major cause of morbidity and mortality. At least 20,000 known exposures(2) and 439 deaths(3) a year are attributed to non-fire-related, unintentional CO poisoning cases in the U.S. However, large registry trials show the prevalence of CO poisoning is far greater with approximately 50,000 ED visits per year.(4) Because the symptoms of CO poisoning are nonspecific—ranging from mild headache, nausea, confusion, and dizziness to end-organ injury, such as myocardial infarction, stroke, and death—diagnosis is difficult and has historically relied on clinical suspicion and confirmation by measurement of carboxyhemoglobin (COHb) via invasive blood gas analysis. Unfortunately, it has been estimated that up to half of U.S. hospitals do not have invasive COHb testing ability—increasing the potential that many victims of CO poisoning could be overlooked and misdiagnosed.(5)
The study, conducted over a year-long period in the Department of Emergency Medicine at one of the largest hospitals in Europe, the Vienna General Hospital (AKH Vienna), compared the accuracy of SpCO measured noninvasively using the Masimo Radical-7 with COHb measurements obtained via invasive blood gas analysis in 1,578 ED patients. Results showed a bias of 2.99% COHb (1.50% for smokers, 4.33% for nonsmokers) and a precision of 3.27% COHb (2.90% for smokers, 2.98% for nonsmokers) between SpCO and lab values—demonstrating "acceptable bias and precision" for the "detection of high concentrations of COHb, found in acute CO poisoning." Values ranged from 0-50% for SpCO and 0-39.3% for COHb with limits of agreement from -3.55% to 9.53% COHb (-4.30% to 7.30% for smokers, -1.63% to 10.29% for nonsmokers). A total of 17 patients (9 smokers, 8 nonsmokers) with a mean COHb of 14.1% received a final diagnosis of CO poisoning. Using a cut-off SpCO value of 6.6%, the researchers found a 94% sensitivity (ability to detect CO poisoning) and 77% specificity (ability to identify a lack of CO poisoning) and stated that the method "appears to be a reasonable upper limit of normal cutoff value for a screening test in the ED setting."
Researchers also found that several factors influence SpCO measurement accuracy as compared to COHb, including smoking, SpCO level, interval between measurements, and age. Because cigarettes increase CO levels in the blood, users were cautioned to pay attention to "the number of cigarettes smoked." Importantly, because CO in the blood decreases with time, researchers cited the "half-life of CO" and "time between multiwave pulse oximetry and blood gas analysis" as other possible "influencing factors on the deviation between SpCO and COHb." The study also shows that time between measurement was still a factor within the 60-minute cut-off established by the researchers—underscoring the importance of simultaneous comparisons between SpCO and invasive blood gas measurements due to the half-life of CO.
Study authors concluded that SpCO measurement via multiwave pulse oximetry has "an acceptable bias and precision" and "keeping influencing factors in mind, it can therefore be used to screen large numbers of patients for latent CO poisoning." They also noted the "potential for different measurement results from correct and incorrect (sensor) placement," an encouragement for users to closely follow the directions for use. The current study follows the results by researchers in the ED of a Rhode Island Hospital, who first demonstrated that large scale population screening of ED patients using SpCO could identify patients with unsuspected CO poisoning.(6)
(1) Roth D, Herkner H, Schreiber W, Hubmann N, Gamper G, Laggner A, Havel C. "Accuracy of Noninvasive Multiwave Pulse Oximetry Compare with Carboxyhemoglobin From Blood Gas Analysis in Unselected Emergency Department Patients." Annals of Emergency Medicine Published April 2011 online ahead of print here.
(2) Centers for Disease Control and Prevention. "Nonfatal, unintentional, non–fire-related carbon monoxide exposures—United States, 2004-2006." MMWR Morb Mortal Wkly Rep. 2008;57:896-899.
(3) Centers for Disease Control and Prevention. "Carbon monoxide–related deaths—United States, 1999-2004." MMWR Morb Mortal Wkly Rep. 2007;56:1309-1312.
(4) Keles A, Demircan A, Kurtoglu G. "Carbon monoxide poisoning: how many patients do we miss?" Eur J Emerg Med. 2008;15:154-157.
(5) Hampson NB, Scott KL, Zmaeff JL. "Carboxyhemoglobin measurement by hospitals: implications for the diagnosis of carbon monoxide poisoning." J Emerg Med. 2006;31:13-16.
(6) Suner S, Partridge R, Sucov A, et al. "Noninvasive Pulse CO-Oximetry Screening in the Emergency Department Identifies Occult Carbon Monoxide Toxicity." J. Emerg Med. 2008; 34(4): 441-450.
Masimo (NASDAQ: MASI) is the global leader in innovative noninvasive 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 rainbow® SET Pulse CO-Oximetry™ technology, allowing noninvasive and continuous monitoring of blood constituents that previously required invasive procedures, including total hemoglobin (SpHb®), oxygen content (SpOC™), carboxyhemoglobin (SpCO®), methemoglobin (SpMet®), and Pleth Variability Index (PVI®), in addition to SpO2, pulse rate, and perfusion index (PI). In 2008, Masimo introduced Patient SafetyNet™, a remote monitoring and wireless clinician notification system designed to help hospitals avoid preventable deaths and injuries associated with failure to rescue events. In 2009, Masimo introduced rainbow Acoustic Monitoring™, the first-ever noninvasive and continuous monitoring of acoustic respiration rate (RRa™). Masimo's rainbow SET technology platform offers a breakthrough in patient safety by helping clinicians detect life-threatening conditions and helping guide treatment options. In 2010, Masimo acquired SEDLine®, a pioneer in the development of innovative brain function monitoring technology and devices. Masimo SET and Masimo rainbow SET technologies can be also found in over 100 multiparameter patient monitors from over 50 medical device manufacturers around the world. Founded in 1989, Masimo has the mission of "Improving Patient Outcome and Reducing Cost of Care … by Taking Noninvasive Monitoring to New Sites and Applications®." Additional information about Masimo and its products may be found at www.masimo.com.
This press release includes forward-looking statements as defined in Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, in connection with the Private Securities Litigation Reform Act of 1995. These forward-looking statements are based on current expectations about future events affecting us and are subject to risks and uncertainties, all of which are difficult to predict and many of which are beyond our control and could cause our actual results to differ materially and adversely from those expressed in our forward-looking statements as a result of various risk factors, including, but not limited to: risks related to our assumptions regarding the repeatability of clinical results, risks related to our belief that Masimo SpCO will provide an accurate and effective method of screening for CO poisoning in large numbers of at-risk populations, as well as other factors discussed in the "Risk Factors" section of our most recent reports filed with the Securities and Exchange Commission ("SEC"), which may be obtained for free at the SEC's website at www.sec.gov. Although we believe that the expectations reflected in our forward-looking statements are reasonable, we do not know whether our expectations will prove correct. All forward-looking statements included in this press release are expressly qualified in their entirety by the foregoing cautionary statements. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of today's date. We do not undertake any obligation to update, amend or clarify these statements or the "Risk Factors" contained in our most recent reports filed with the SEC, whether as a result of new information, future events or otherwise, except as may be required under the applicable securities laws.
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