Masimo Announces Full Market Release of Hydration Index for the Masimo W1™ Advanced Health Tracking Watch

Masimo (NASDAQ: MASI) today announced the full market release of Hydration Index (Hi™) for the Masimo W1™ watch. The Masimo W1, an advanced health tracking wearable, is the first watch to offer accurate, continuous pulse oximetry measurements and insightful health data, from the leader in hospital pulse oximetry. Hydration Index, first announced earlier this year in a limited market release, provides an index that tracks an individual’s hydration levels and integrates seamlessly with other continuous Masimo W1 health data, such as oxygen saturation (SpO2), pulse rate, respiration, and more.

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Masimo W1™ with Hydration Index (Graphic: Business Wire)

Masimo W1™ with Hydration Index (Graphic: Business Wire)

Hydration level has been one of the most sought out parameters by athletes, vocalists, and others seeking to optimize their performance. Since creating PVi® – which allows clinicians to assess fluid responsiveness of mechanically ventilated patients – nearly 15 years ago, Masimo has been working to invent a way to help people gain insight into hydration. Proper hydration is widely recognized as an important aspect of health and performance, and lack of proper hydration affects many physiological parameters, as the body works to restore homeostasis. Masimo W1 is designed to help you identify your hydration baseline, helping you understand your hydration level, which not only affects athletic performance, but can also support healthier lifestyle decisions. Whether you’re an elite athlete, a vocalist, a health-focused individual, or just keen to gain more insight into your body’s physiological status, Masimo W1 with Hydration Index represents a breakthrough solution to better understand and manage hydration health.

Tommy Haas, Olympic silver medalist and professional tennis player, said, “I have wanted to know the level of my hydration since I began competing, but always had to guess about it. Masimo W1 with Hydration Index finally makes this possible.”

Nick Mayhugh, World Record holder and three-time Paralympic champion, added, “As a professional athlete who trains six days a week and ten hours a day, I need to know my hydration levels at all times. Masimo’s Hydration Index technology will provide athletes of all levels the opportunity to maximize their training and recovery programs, leading to optimal performance.”

Known for its exceptional accuracy and reliability during challenging conditions, such as motion and low perfusion, Masimo, with the Masimo W1, brings its expertise in signal processing, photonics, and bio-sensing to consumers looking to take control of their personal health, make better health decisions, and monitor their overall physiological status. Masimo W1 pairs via secure Bluetooth® to the Masimo Health™ smartphone app to unlock meaningful, actionable insights. The integrated Personal SafetyNet™ subscription service gives users access to sophisticated reporting tools to help them review their physiological status over time and facilitates sharing data with family members, fitness trainers, wellness coaches, and where allowed, healthcare providers.

Benefiting from Masimo’s expertise in hospital connectivity and hospital automation, a medical version of Masimo W1 will be available outside the US for use in telehealth and telemonitoring applications via Masimo SafetyNet® and Personal SafetyNet™ for healthcare providers and payers, as well as individual use. Masimo W1 is a convenient, reliable remote monitoring and telehealth solution enabling hospitals and clinicians to proactively keep track of their patients’ physiological status from afar, even as patients go about everyday tasks at home. A natural complement to the Masimo SafetyNet remote patient monitoring platform, Masimo W1 enables wireless transmission of patient data to the Masimo SafetyNet app and Masimo’s secure data cloud, where it can be reviewed in near-real time by remote monitoring teams in centralized locations for signs of physiological decline or sudden changes, such as falls or spikes in heart rate.

Dr. Amin, Professor, Endowed Chair of Medicine and Executive Director of Hospital Medicine at the University of California, Irvine, said, “Evaluating intravascular volume status is a common problem in clinical care, particularly for post-op patients and those with complicated chronic conditions such as congestive heart failure (CHF). These patients often seek care in the emergency department (ED) for monitoring and treatment. Masimo W1 helps individuals understand their hydration level by tracking their Hydration index (Hi), and provides a common additional monitoring endpoint beyond daily weights for evaluation of hydration. Having continuous, noninvasive monitoring of Hi available in a wearable device means people are now able to access important, real-time information at home. This has the potential to be a game changer for all involved in the management of chronic conditions like CHF, and also for those managing post-op patients.”

Joe Kiani, Founder and CEO of Masimo, said, “Masimo W1 represents numerous firsts: the first wrist-worn wearable device to offer consumers accurate, continuous pulse oximetry. The first—but not the last—such device from Masimo. And, with Hydration Index, the first watch to give users actionable, insightful hydration data, helping everyone to make healthier decisions so that they can live their best lives.”

Masimo W1 and Hi have not been cleared by the FDA and are not available for use in medical applications in the U.S.

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About Masimo

Masimo (NASDAQ: MASI) is a global medical technology company that develops and produces a wide array of industry-leading monitoring technologies, including innovative measurements, sensors, patient monitors, and automation and connectivity solutions. In addition, Masimo Consumer Audio is home to eight legendary audio brands, including Bowers & Wilkins, Denon, Marantz, and Polk Audio. Our mission is to improve life, improve patient outcomes, and reduce the cost of care. Masimo SET® Measure-through Motion and Low Perfusion™ pulse oximetry, introduced in 1995, has been shown in over 100 independent and objective studies to outperform other pulse oximetry technologies.1 Masimo SET® has also been shown to help clinicians reduce severe retinopathy of prematurity in neonates,2 improve CCHD screening in newborns,3 and, when used for continuous monitoring with Masimo Patient SafetyNet™ in post-surgical wards, reduce rapid response team activations, ICU transfers, and costs.4-7 Masimo SET® is estimated to be used on more than 200 million patients in leading hospitals and other healthcare settings around the world,8 and is the primary pulse oximetry at 9 of the top 10 hospitals as ranked in the 2022-23 U.S. News and World Report Best Hospitals Honor Roll.9 In 2005, Masimo introduced rainbow® Pulse CO-Oximetry technology, allowing noninvasive and continuous monitoring of blood constituents that previously could only be measured invasively, including total hemoglobin (SpHb®), oxygen content (SpOC™), carboxyhemoglobin (SpCO®), methemoglobin (SpMet®), Pleth Variability Index (PVi®), RPVi™ (rainbow® PVi), and Oxygen Reserve Index (ORi™). In 2013, Masimo introduced the Root® Patient Monitoring and Connectivity Platform, built from the ground up to be as flexible and expandable as possible to facilitate the addition of other Masimo and third-party monitoring technologies; key Masimo additions include Next Generation SedLine® Brain Function Monitoring, O3® Regional Oximetry, and ISA™ Capnography with NomoLine® sampling lines. Masimo’s family of continuous and spot-check monitoring Pulse CO-Oximeters® includes devices designed for use in a variety of clinical and non-clinical scenarios, including tetherless, wearable technology, such as Radius-7®, Radius PPG®, and Radius VSM™, portable devices like Rad-67®, fingertip pulse oximeters like MightySat® Rx, and devices available for use both in the hospital and at home, such as Rad-97®. Masimo hospital and home automation and connectivity solutions are centered around the Masimo Hospital Automation™ platform, and include Iris® Gateway, iSirona™, Patient SafetyNet, Replica®, Halo ION®, UniView®, UniView :60™, and Masimo SafetyNet®. Its growing portfolio of health and wellness solutions includes Radius Tº® and the Masimo W1™ watch. Additional information about Masimo and its products may be found at Published clinical studies on Masimo products can be found at

ORi, RPVi, and Radius VSM have not received FDA 510(k) clearance and are not available for sale in the United States. The use of the trademark Patient SafetyNet is under license from University HealthSystem Consortium.


  1. Published clinical studies on pulse oximetry and the benefits of Masimo SET® can be found on our website at Comparative studies include independent and objective studies which are comprised of abstracts presented at scientific meetings and peer-reviewed journal articles.
  2. Castillo A et al. Prevention of Retinopathy of Prematurity in Preterm Infants through Changes in Clinical Practice and SpO2 Technology. Acta Paediatr. 2011 Feb;100(2):188-92.
  3. de-Wahl Granelli A et al. Impact of pulse oximetry screening on the detection of duct dependent congenital heart disease: a Swedish prospective screening study in 39,821 newborns. BMJ. 2009;Jan 8;338.
  4. Taenzer A et al. Impact of pulse oximetry surveillance on rescue events and intensive care unit transfers: a before-and-after concurrence study. Anesthesiology. 2010:112(2):282-287.
  5. Taenzer A et al. Postoperative Monitoring – The Dartmouth Experience. Anesthesia Patient Safety Foundation Newsletter. Spring-Summer 2012.
  6. McGrath S et al. Surveillance Monitoring Management for General Care Units: Strategy, Design, and Implementation. The Joint Commission Journal on Quality and Patient Safety. 2016 Jul;42(7):293-302.
  7. McGrath S et al. Inpatient Respiratory Arrest Associated With Sedative and Analgesic Medications: Impact of Continuous Monitoring on Patient Mortality and Severe Morbidity. J Patient Saf. 2020 14 Mar. DOI: 10.1097/PTS.0000000000000696.
  8. Estimate: Masimo data on file.

Forward-Looking Statements

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 include, among others, statements regarding the potential effectiveness of Masimo W1™ and Hydration Index. 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's unique noninvasive measurement technologies, including Masimo W1 and Hydration Index, contribute to positive clinical outcomes and patient safety; risks related to our belief that Masimo noninvasive medical breakthroughs provide cost-effective solutions and unique advantages; risks related to COVID-19; 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 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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