Hilo Cuffless Blood Pressure Monitoring System: Technology, Clinical Validation, Regulatory Trajectory and Market Dynamics

Nelson Advisors
52 minutes ago
9 min read

Corporate Genesis, Rebranding and Capital Structure

The Hilo blood pressure monitoring platform represents a pivotal technological advancement in continuous, non-invasive cardiovascular surveillance. Originally established in Neuchâtel, Switzerland, as Aktiia SA, the enterprise emerged from nearly two decades of dedicated micro-engineering research conducted at the Swiss Center for Electronics and Microtechnology (CSEM). Co-founded by Mattia Bertschi and Josep Sola, the organisation pioneered optical pulse wave analysis to derive arterial pressure dynamics continuously without relying on repetitive inflatable cuff measurements. In May 2025, Aktiia underwent a comprehensive institutional rebranding to become Hilo, a transition timed to support commercial scaling, international market expansion and enterprise platform integration.

The organisation’s capital structure has expanded through institutional venture funding. Hilo closed an oversubscribed $42 Million Series B financing round co-led by Earlybird Health and Wellington Partners, with participation from new institutional investors including Kfund and naturalX Health Ventures, alongside existing backers such as Khosla Ventures, redalpine, Molten Ventures, Translink Capital and Verve Ventures. Subsequent extension rounds increased the company’s total raised capital beyond $119 Million. Under the executive leadership of Chief Executive Officer Raghav "Rags" Gupta, Hilo achieved a 76% compound annual revenue growth rate (CAGR) and recorded over 130,000 commercial device sales across global jurisdictions prior to its full commercial entry into the United States market.

The operational transition from CSEM micro-engineering research to Aktiia SA, and ultimately to Hilo, illustrates a structural evolution from a specialized biomedical startup to a high-volume digital health infrastructure provider.

By integrating continuous physiological signal collection with cloud-based Machine Learning foundation models, Hilo has positioned its platform at the convergence of consumer medical wearables and clinical-grade diagnostics.

Technological Architecture and Operational Mechanism

Optical Blood Pressure Monitoring Dynamics

The technical foundation of the Hilo system centers on its proprietary Optical Blood Pressure Monitoring (OBPM) technology, which operates within a lightweight wristband pod. Unlike traditional sphygmomanometers that depend on mechanical arterial occlusion via inflatable bladders, Hilo utilises reflective photoplethysmography (PPG). Green light-emitting diodes (LEDs) integrated into the underside of the wrist pod illuminate the microvascular bed of the inner wrist. Photosensors capture variations in reflected light intensity that correspond directly to microvascular volume oscillations driven by cardiac ventricular ejection.

The underlying software algorithms process these raw PPG signals beyond simple peak detection for heart rate calculation. Hilo’s foundation machine learning model, trained on tens of billions of optical signals and refined against hundreds of millions of clinical calibration points, analyses the complete morphological structure of each pulse wave. The algorithm extracts biophysical features related to arterial compliance, pulse wave velocity, peripheral vascular resistance and reflected wave timing to calculate uncalibrated estimates of Systolic Blood Pressure (SBP) and Diastolic Blood Pressure (DBP).

This optical wave processing flow functions as an integrated pipeline. Subcutaneous photoplethysmography sensors capture raw volumetric waveforms, which are immediately passed to local and cloud-based signal quality filters. Once low-quality signals caused by major motion artifacts are discarded, the foundation machine learning model extracts structural features of pulse morphology. These features are mapped against the user's calibration profile to compute absolute systolic and diastolic blood pressure values approximately 25 to 50 times per day.

The Calibration Architecture

Because optical PPG sensors measure relative volumetric changes rather than absolute hydrostatic pressure, Hilo incorporates a hybrid calibration architecture. To ground continuous optical estimates in absolute millimetres of mercury (\text{mmHg}), the platform includes an oscillometric upper-arm calibration cuff.

During initial setup, and periodically at 30-day intervals, the user performs a seated calibration using the upper-arm cuff. The initialisation algorithm establishes a personalised baseline transfer function that maps the individual’s unique arterial wave features to discrete oscillometric pressure measurements.

Periodic recalibration ensures that long-term changes in vascular tone, ambient temperature influences, or biological aging do not cause measurement drift from absolute pressure baselines over extended monitoring windows.

Parameter / Feature	System Specification
Measurement Technology	Reflective Photoplethysmography (PPG) & Pulse Wave Morphology Analysis
Calibration Method	Oscillometric Upper-Arm Cuff (Initial & 30-Day Recalibration Cycle)
Sampling Frequency	Automatic continuous background sampling (~25 to 50 readings per 24 hours)
Wrist Pod Dimensions	8.5 { mm (thickness)} \times 16 { mm (width)} \times 34 \{ mm (length)}
Wrist Strap Fit Range	140 { mm} to 210 mm} wrist circumference
Calibration Cuff Fit Range	22 { cm} to 42{ cm} upper-arm circumference
Hardware Weight	16 { grams} total (wrist pod and silicone strap combined)
Battery Life & Charging	Up to 15 days operational life; full charge in ~90 minutes via magnetic USB pod
Ingress Protection	IP68 Certified (Water resistant for showering, handwashing, and swimming)
Wireless Protocols	Bluetooth Low Energy (BLE 5.0+)
Operating System Support	iOS 16.0 or later; Android 8.0 or later
Data Security Standards	End-to-end encrypted transport, cloud storage, GDPR compliant (EU)

Clinical Evidence, Diagnostic Performance and Regulatory Approvals

ISO 81060-2 Validation Data

The diagnostic authority of any automated blood pressure measurement platform depends on validation against international reference standards. Hilo, operating clinically under its validated Aktiia technology foundation, has undergone validation aligned with the International Organisation for Standardisation ANSI/AAMI/ISO 81060-2 guidelines.

ISO 81060-2 compliance requires meeting two statistical evaluation criteria:

Criterion 1: Evaluates total population bias, requiring the mean error between the test device and reference determinations (double-blinded auscultation or mercury sphygmomanometry) to be within 5.0 mmHg}, with a standard deviation (SD) of 8.0 mmHg}.
Criterion 2: Evaluates subject-level consistency, requiring the standard deviation of averaged paired differences per subject to meet specified acceptance thresholds based on the overall mean error.

Clinical investigations have evaluated the cuffless wrist sensor against invasive intra-arterial catheterisation within intensive care environments. In these studies, optical blood pressure estimation achieved a standard deviation of error of $7.1 \text{ mmHg}$ for SBP and $2.9 \text{ mmHg}$ for DBP relative to continuous arterial lines, demonstrating statistical significance ($p < 0.001$) and high linear correlation coefficients approaching $r=1.0$ for diastolic metrics.

Clinical Study / Cohort Focus	Cohort Size (N)	SBP Mean Error (mmHg)	SBP SD (mmHg)	DBP Mean Error (mmHg)	DBP SD (mmHg)	Key Validation Outcome
ISO 81060-2 Initialisation Cuff Validation	85 adults	+1.30	7.11	-0.20	5.46	Passed ISO Criteria 1 & 2 vs. double-auscultation
Invasive Arterial Line Comparison	ICU cohort	N/A	7.10	N/A	2.90	Validated optical wave tracking vs. direct intra-arterial catheters
Older Adults (Age 60 to 88)	86 seniors	+0.46	< 8.00	-0.39	< 8.00	Accuracy maintained across seated, standing, and supine positions
24-Hour ABPM Concordance Study	54 patients	Comparative	236 rdgs/day	Comparative	51 rdgs/day	79% concordance in detecting nocturnal dipping vs standard ABPM
COOL-BP Remote Monitoring Trial	Mass General Brigham	r = 0.57	28,971	r = 0.64	91% preference	87.5% concordance in tracking pharmacotherapeutic BP adjustments

Global Regulatory Profile

Hilo has established a comprehensive international regulatory footprint across multiple jurisdictions. In the European Union, the system earned CE Mark certification as a Class IIa Medical Device under the European Union Medical Device Regulation (EU MDR 2017/745). In the United States, Hilo received 510(k) clearance from the U.S. Food and Drug Administration (FDA) for over-the-counter (OTC) sales of its G0 / Hilo Core blood pressure monitoring system, representing the first over-the-counter clearance granted by the FDA for a cuffless blood pressure monitor.

Beyond Europe and the United States, the company has secured full medical device regulatory approvals across Health Canada, the Australian Therapeutic Goods Administration (TGA), and the Saudi Food and Drug Authority (SFDA).

Clinical Utility, Guidelines Alignment and Diagnostic Exclusions

Alignment with Contemporary Clinical Guidelines

Hypertension guidelines worldwide, including those issued by the National Institute for Health and Care Excellence (NICE) in the United Kingdom and the American Heart Association (AHA) in the United States, increasingly emphasise out of clinic blood pressure monitoring. Isolated measurements taken in clinical settings are often distorted by the "white coat effect," where stress elevates blood pressure, or by masked hypertension, where normal clinic readings obscure elevated out-of-office pressure.

Traditional Home Blood Pressure Monitoring (HBPM) requires patients to adhere to strict resting protocols twice daily for seven days, whereas 24-hour Ambulatory Blood Pressure Monitoring (ABPM) relies on daytime and night-time cuff inflations that can disrupt sleep patterns.

Hilo addresses these diagnostic limitations by collecting continuous out-of-clinic datasets automatically. Taking between 25 and 50 measurements across 24-hour periods during daily activities and rest, Hilo enables healthcare providers to evaluate cardiovascular dynamics through metrics such as Time in Target Range (TTR). TTR quantifies the proportion of time a patient's blood pressure remains within target physiological limits, offering a broader view of blood pressure control than isolated spot checks.

Furthermore, continuous optical monitoring captures circadian blood pressure variations, specifically night-time dipping profiles and morning surges. Blunted nocturnal dipping is an independent risk factor for stroke, heart failure, and target organ damage, while rapid morning surges correlate with elevated risks of acute cardiovascular events. By tracking these patterns without waking the patient, Hilo provides longitudinal data that help clinicians refine risk assessments and optimise medication timing.

Population Exclusions and Diagnostic Contraindications

Despite its analytical capabilities, the optical PPG waveform analysis underlying the Hilo platform has specific operational boundaries. Cardiac arrhythmias, such as Atrial Fibrillation (AFib), frequent premature ventricular contractions (PVCs), or severe heart block, disrupt systemic pulse wave morphology, preventing the algorithm from performing accurate feature extraction. Consequently, sustained arrhythmias represent a primary contraindication.

Similarly, peripheral microvascular impairments limit optical signal propagation. Conditions that attenuate peripheral perfusion, including severe Raynaud's phenomenon, end-stage renal failure, untreated thyroid disorders, pheochromocytoma, or active arteriovenous fistulas, reduce optical light reflection below acceptable signal-to-noise thresholds.

Anatomically, the wrist pod cannot be worn over damaged skin, surgical scar tissue, or limbs exhibiting severe peripheral edema. Demographically, Hilo is clinically validated for adults aged 21 to 85 years, excluding pediatric cohorts, adults over 85, and pregnant women due to altered vascular compliance and gestational hemodynamic profiles.

Commercial Model, User Experience and Competitive Landscape

Commercial Strategy and Monetisation Structure

Hilo operates on a commercial framework combining direct hardware sales with a Software-as-a-Service (SaaS) subscription model. In European and British markets, the system is distributed as a complete package that includes the Hilo Band, the upper-arm calibration cuff, a charging pod and a 12-month software membership.

Annual membership renewals are priced at approximately £119.99 or $119.99 per year. Following FDA 510(k) OTC clearance in the United States, the device was positioned at an initial retail launch price of approximately $280, with eligibility for pre-tax consumer healthcare purchases through Health Savings Accounts (HSA) and Flexible Spending Accounts (FSA).

The subscription structure funds continuous cloud storage, machine learning model updates, GDPR-compliant data security, and automated PDF clinical report exports formatted for physician consultations.

Real-World User Experience Analysis

Real-world operational data and user feedback highlight key aspects of daily device management. Continuous automated data collection gives patients insight into how stress, physical activity, dietary choices, and sleep habits directly influence blood pressure trends. This continuous visibility can encourage positive lifestyle adjustments, though some users initially experience checking anxiety when observing short-term fluctuations, emphasising the importance of focusing on multi-week trends rather than single readings.

From a technical perspective, platform updates have addressed user friction regarding Bluetooth Low Energy (BLE) pairing stability and server sync timing during monthly upper-arm recalibration cycles. Software enhancements include revised app pairing flows—featuring red LED pod flashing indicators—and updated health cards that integrate step counts, sleep duration, and heart rate metrics alongside primary blood pressure analytics.

Feature / Metric	Hilo Band	Samsung Galaxy Watch (5/6/7)	Huawei Watch D	Sky Labs CART-I Ring	Traditional Upper-Arm Cuff
Form Factor	Dedicated minimal wristband	Full Smartwatch	Smartwatch with micro-cuff	Smart Ring	Upper-Arm Cuff & Pump
Measurement Tech	Optical PPG (Wrist)	Optical PPG (Wrist)	Miniaturized Air Bladder	Optical PPG (Finger)	Oscillometric Inflation
Sampling Mode	Continuous / Passive 24/7	On-demand spot check	Manual/scheduled inflation	Passive Continuous	Manual Spot Check
Calibration Need	Monthly cuff calibration	Monthly cuff calibration	None required	Regular recalibration	N/A (Self-contained)
FDA OTC Status	FDA 510(k) OTC Cleared	Region-restricted approval	Limited regional approvals	Regional approvals	Standard FDA Clearance
Nighttime Tracking	Unobtrusive during sleep	Requires manual trigger	Cuff inflates on wrist	Passive during sleep	Disruptive inflation sound

Conclusions and Strategic Outlook

The Hilo blood pressure monitoring system illustrates how continuous physiological data collection can replace episodic diagnostic snapshots in managing cardiovascular health. By converting microvascular optical signals into calibrated arterial pressure estimations, Hilo addresses long-standing challenges in traditional sphygmomanometry, including white-coat hypertension, unrecognised masked hypertension, missed nocturnal dipping patterns, and variable patient compliance.

Technologically, Hilo's deployment of machine learning models trained on extensive optical datasets establishes a validated baseline for cuffless blood pressure monitoring. The system's compliance with ISO 81060-2 validation protocols and its correlation with intra-arterial catheter measurements support its clinical accuracy.

Nevertheless, physiological boundary conditions remain; cardiac arrhythmias, severe peripheral vascular disease, and specific demographic exclusions require continued reliance on traditional oscillometric devices.

Strategically, securing FDA 510(k) OTC clearance positions Hilo to scale within the United States consumer and remote patient monitoring markets, expanding upon its foundation across Europe, Australia and the Middle East. As global clinical guidelines place greater emphasis on out-of-clinic longitudinal blood pressure trends, Hilo's continuous monitoring architecture offers a practical approach to modern cardiovascular risk management.

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