PPG ISO Standards Overview: ISO 80601-2-61 and Regulatory Requirements for PPG Devices

Every PPG-based device intended for clinical measurement must satisfy rigorous international standards that define how accuracy is measured, what safety margins are required, and how performance must be validated. The cornerstone standard for pulse oximetry is ISO 80601-2-61, but the regulatory landscape extends far beyond a single document. Engineers developing PPG devices must navigate a web of interconnected standards covering electrical safety, optical emission limits, software quality, and measurement accuracy.

This guide provides a technical overview of the standards framework governing PPG-based medical devices. Whether you are designing a clinical pulse oximeter, developing cuffless blood pressure estimation algorithms, or building wearable heart rate monitors, understanding these requirements is essential for regulatory clearance and market access.

ISO 80601-2-61: The Core Pulse Oximetry Standard

ISO 80601-2-61:2017 (titled "Medical electrical equipment -- Part 2-61: Particular requirements for basic safety and essential performance of pulse oximeter equipment") is the primary international standard for pulse oximeter devices. It is a particular standard within the IEC 60601 family, meaning it supplements and modifies the general requirements of IEC 60601-1 for the specific application of pulse oximetry.

The standard was developed jointly by ISO Technical Committee 121 (Anaesthetic and respiratory equipment) and IEC Subcommittee 62D (Electromedical equipment). It replaced the earlier ISO 9919:2005 standard and has been adopted as a harmonized standard under both the EU Medical Device Regulation (MDR 2017/745) and the US FDA's recognized consensus standards program.

Scope and Applicability

ISO 80601-2-61 applies to pulse oximeter equipment and pulse oximeter probes designed for human use. This includes standalone pulse oximeters, pulse oximeter modules integrated into patient monitors, and the associated sensors (probes). The standard covers both transmittance-mode devices (where the photodetector is on the opposite side of the tissue from the LEDs, typically used on fingertips and earlobes) and reflectance-mode devices (where the LED and photodetector are on the same side, as used in wrist-worn wearables).

Critically, the standard distinguishes between spot-check and continuous monitoring applications. Spot-check devices are used for single-point measurements, while continuous monitors provide ongoing tracking over extended periods. Continuous monitoring devices face additional requirements for alarm systems and trending accuracy.

SpO2 Accuracy Requirements

The central performance requirement in ISO 80601-2-61 is the SpO2 accuracy specification. The standard defines accuracy using the Arms (root mean square accuracy) metric:

Arms = sqrt( (1/N) * sum( (SpO2_oximeter_i - SaO2_reference_i)^2 ) )

where N is the number of paired data points, SpO2_oximeter is the pulse oximeter reading, and SaO2_reference is the arterial oxygen saturation measured by laboratory co-oximetry from a simultaneously drawn arterial blood sample.

For the clinically relevant range of 70-100% SpO2, the standard requires manufacturers to declare an Arms value, with most regulatory bodies expecting Arms of 4% or less for fingertip transmittance devices. The standard does not mandate a specific Arms threshold but requires the declared accuracy to be validated through controlled desaturation studies. In practice, the FDA's guidance document (2013) establishes Arms <= 3% as the expectation for cleared devices, which is more stringent than many international implementations.

Bland and Altman (1986) established the statistical framework for comparing measurement methods that underpins the accuracy assessment methodology. The controlled desaturation protocol typically requires a minimum of 200 paired data points from at least 10 healthy adult subjects spanning the 70-100% SpO2 range in approximately equal increments.

Controlled Desaturation Study Protocol

The gold-standard validation method defined in ISO 80601-2-61 Annex EE involves induced hypoxemia in healthy volunteers under carefully controlled conditions. Subjects breathe gas mixtures containing nitrogen, oxygen, and carbon dioxide in varying proportions to achieve target SpO2 plateaus across the 70-100% range. Arterial blood samples are drawn at each plateau and analyzed using a laboratory co-oximeter (such as the IL 682 or Radiometer ABL800).

The study must include stable SpO2 plateaus at a minimum of five levels, typically targeting approximately 70%, 75%, 80%, 85%, 90%, 95%, and 100%. At each plateau, both the pulse oximeter reading and arterial blood gas values are recorded simultaneously. The protocol requires institutional review board (IRB) approval due to the deliberate induction of hypoxemia, and subjects must meet specific inclusion criteria (healthy adults, non-smokers, no hemoglobin abnormalities).

Severinghaus and Naifeh (1987) pioneered many aspects of this desaturation methodology, and their work on pulse oximeter accuracy assessment during rapid desaturation remains foundational to current testing protocols. Their study of 14 commercial oximeters using 1,462 data points from 74 subjects demonstrated the wide performance variability that motivated standardized testing requirements.

IEC 60601-1: General Medical Electrical Safety

IEC 60601-1:2005+A1:2012+A2:2020 (the consolidated third edition with amendments) establishes the baseline safety and performance requirements for all medical electrical equipment. As a particular standard, ISO 80601-2-61 inherits and modifies these general requirements for the specific context of pulse oximetry.

Key IEC 60601-1 requirements relevant to PPG devices include electrical safety testing (leakage currents, dielectric strength, protective earthing), mechanical safety (enclosure strength, moving parts protection), and risk management integration per ISO 14971. For battery-powered wearable PPG devices, the requirements around patient leakage currents are particularly relevant: Type BF applied parts (typical for skin-contact PPG sensors) must limit patient auxiliary current to 100 microamperes under normal conditions and 500 microamperes under single fault conditions.

The essential performance concept introduced in Edition 3 is especially important for PPG devices. Essential performance refers to performance characteristics where loss or degradation could result in an unacceptable risk. For pulse oximeters, this includes the accuracy of SpO2 and pulse rate measurements, alarm functionality, and display integrity. Manufacturers must identify essential performance through their risk management process and verify that it is maintained under all specified operating conditions.

IEC 62471: Photobiological Safety of LED Emissions

PPG devices emit optical radiation from LEDs (typically green at 525-530 nm, red at 660 nm, and infrared at 880-940 nm), and the photobiological safety of these emissions must be assessed under IEC 62471:2006 (Photobiological safety of lamps and lamp systems). This standard classifies optical radiation sources into four risk groups based on emission limits for various hazard types: actinic ultraviolet, near-UV, retinal blue light, retinal thermal, infrared radiation for the eye, and thermal hazard for the skin.

For PPG LEDs in skin-contact wearable devices, the primary concerns are thermal effects and, for visible wavelengths, potential photochemical effects during prolonged exposure. Most PPG LEDs operate well below the Exempt Group limits due to their low optical power (typically 1-20 mW per LED) and the fact that emission is into skin tissue rather than toward the eyes. However, manufacturers must formally assess and document the risk group classification.

Typical PPG LED specifications and their photobiological context: green LEDs at 525 nm emit 5-15 mW optical power into tissue at duty cycles of 10-25%, yielding time-averaged irradiance at the skin surface of 10-50 mW/cm^2. Red LEDs at 660 nm and infrared LEDs at 940 nm used in pulse oximetry operate at similar power levels. IEC 62471's skin thermal hazard limit for continuous exposure is 20,000 W/m^2 (2,000 mW/cm^2), providing substantial safety margin for PPG applications. Detailed comparisons of PPG LED wavelengths and their properties are covered in our wavelength comparison guide.

ISO 81060-2: Cuffless Blood Pressure Measurement

As PPG-based cuffless blood pressure (BP) estimation gains clinical interest, ISO 81060-2:2018 (Non-invasive sphygmomanometers -- Part 2: Clinical investigation of intermittent automated measurement type) becomes critically relevant. This standard defines the validation protocol for non-invasive BP measurement devices, requiring comparison against either an invasive arterial catheter reference or a dual-observer auscultatory reference.

The accuracy criterion from ISO 81060-2 requires a mean error of 5 mmHg or less and a standard deviation of 8 mmHg or less across a population of at least 85 subjects spanning a defined BP range. For PPG-based cuffless devices, meeting this standard is exceptionally challenging because the relationship between PPG features (pulse transit time, pulse wave morphology) and absolute blood pressure is confounded by arterial compliance, vascular tone, and individual calibration requirements.

The IEEE 1708-2014 standard (Standard for Wearable Cuffless Blood Pressure Measuring Devices) provides additional guidance specific to wearable cuffless BP devices, including requirements for calibration frequency, posture effects, and motion artifact tolerance. Mukkamala et al. (2015) published a comprehensive review of cuffless BP measurement technologies and the standards challenges they face, noting that no PPG-only cuffless BP device had achieved ISO 81060-2 validation at the time (DOI: 10.1109/TBME.2015.2441951). As of 2025, very few devices have achieved full validation, and those that have typically use a combination of PPG with additional sensing modalities. For a deeper technical exploration of the methods used, see our PPG blood pressure estimation methods guide.

IEC 62304: Medical Device Software Lifecycle

All software in medical PPG devices, from firmware controlling LED drive current and ADC sampling to signal processing algorithms computing SpO2 and heart rate, must comply with IEC 62304:2006+A1:2015 (Medical device software -- Software life cycle processes). This standard establishes requirements for software development planning, requirements analysis, architectural design, detailed design, implementation, verification, and maintenance.

IEC 62304 classifies software into three safety classes based on the severity of potential harm from software failure. Class A applies when software cannot contribute to a hazardous situation; Class B when software can contribute to a non-serious injury; and Class C when software can contribute to death or serious injury. Pulse oximeter software typically falls into Class B or Class C, depending on the intended use and clinical context.

For Class C software (which includes continuous monitoring pulse oximeters in critical care), IEC 62304 requires comprehensive documentation including software architecture documentation, detailed design specifications, unit-level verification (test coverage metrics), integration testing, and system-level testing. Traceability from requirements through design to verification must be maintained throughout the software lifecycle. This has significant implications for the implementation of machine learning models in PPG analysis, as the standard's verification and validation requirements are designed around deterministic software and can be challenging to apply to trained models with learned parameters.

Electromagnetic Compatibility: IEC 60601-1-2

PPG devices must demonstrate electromagnetic compatibility (EMC) per IEC 60601-1-2:2014+A1:2020 (Edition 4.1). This collateral standard specifies emissions limits (to avoid interfering with other equipment) and immunity requirements (to ensure the device functions correctly in the presence of electromagnetic disturbances).

For wearable PPG devices, immunity testing is particularly important because these devices operate in electromagnetically diverse environments (homes, gyms, hospitals). Key immunity tests include electrostatic discharge (ESD) at 8 kV contact / 15 kV air, radiated RF immunity at 3 V/m (10 V/m in close proximity), and conducted RF immunity on cables. The Edition 4 approach requires manufacturers to identify the intended electromagnetic environment and justify test levels based on a risk assessment rather than applying blanket test levels.

A practical concern for PPG devices is interference from ambient light sources. While IEC 60601-1-2 addresses radiofrequency interference, ambient light rejection is addressed within ISO 80601-2-61 itself, which requires that pulse oximeter performance is not degraded by ambient illumination up to 891 lux of fluorescent lighting and other specified light sources. Modern PPG front-end ICs (such as the Texas Instruments AFE4404 or Analog Devices ADPD4101) implement ambient light subtraction through alternating LED-on/LED-off sampling, but the standard requires system-level validation that this rejection is sufficient.

Biocompatibility: ISO 10993 Series

PPG sensors are in direct and prolonged skin contact, making biocompatibility assessment under the ISO 10993 series mandatory. ISO 10993-1:2018 (Biological evaluation of medical devices -- Part 1: Evaluation and review within a risk management process) requires a biological evaluation plan that identifies the specific tests needed based on the nature and duration of body contact.

For skin-contact PPG sensors classified as surface-contacting devices with prolonged exposure (greater than 24 hours for continuous-wear wearables), the typically required ISO 10993 evaluations include cytotoxicity (ISO 10993-5), sensitization (ISO 10993-10), and irritation (ISO 10993-23). Materials in contact with the skin (sensor housing polymers, optical windows, adhesives, and wristband materials) must be evaluated individually or as part of the final device assembly.

Regulatory Pathways and Standards Compliance

FDA Clearance (United States)

In the United States, pulse oximeters are regulated as Class II medical devices under 21 CFR 870.2710 and typically cleared through the 510(k) premarket notification pathway. The FDA recognizes ISO 80601-2-61 as a consensus standard, meaning manufacturers can declare conformity rather than conducting independent testing to FDA-specific requirements. However, the FDA's 2013 guidance document on pulse oximeters establishes expectations (Arms <= 3% for SpO2, declared accuracy for pulse rate) that may exceed the minimum requirements of the international standard.

Consumer wearable devices that measure heart rate but do not claim SpO2 measurement are generally regulated as Class I general wellness devices under the FDA's 2016 General Wellness guidance, provided they do not make disease-specific claims. This regulatory distinction is critical for product development strategy: adding SpO2 measurement capability shifts a device from Class I wellness to Class II medical device, dramatically increasing the regulatory burden.

CE Marking (European Union)

Under the EU Medical Device Regulation (MDR 2017/745), pulse oximeters are classified as Class IIa devices (measuring rule 10 -- active devices intended for diagnosis). Compliance requires a conformity assessment involving a Notified Body review, quality management system certification to ISO 13485, and technical documentation demonstrating compliance with the General Safety and Performance Requirements (GSPR) in Annex I of the MDR.

The harmonized standards (ISO 80601-2-61, IEC 60601-1, etc.) provide a presumption of conformity with the relevant GSPRs, streamlining the conformity assessment process. However, the MDR's enhanced post-market surveillance requirements (including periodic safety update reports and post-market clinical follow-up) add ongoing compliance obligations beyond the initial product launch.

Emerging Standards for Novel PPG Applications

Wearable Heart Rate Monitors

There is currently no specific ISO or IEC standard dedicated to wearable optical heart rate monitors that do not measure SpO2. The CTA-2065 standard (Physical Activity Monitor Accuracy and Reliability of Heart Rate Measurement) from the Consumer Technology Association provides voluntary accuracy requirements, but it is not a regulatory requirement. CTA-2065 specifies testing during rest and multiple exercise modalities (walking, running, cycling) with mean absolute error (MAE) as the primary metric.

Nelson et al. (2020) evaluated the accuracy of seven commercial wrist-worn heart rate monitors during various activities and found MAE values ranging from 1.8 to 7.2 BPM at rest and 4.5 to 27.3 BPM during running (DOI: 10.1038/s41746-020-0226-6). The wide performance spread highlights the need for standardized testing, as many consumers assume clinical-grade accuracy from devices that have never been validated against a reference standard.

Continuous Glucose Monitoring via PPG

As research explores PPG-based non-invasive glucose estimation, the applicable standard would be ISO 15197:2013 (In vitro diagnostic test systems -- Requirements for blood-glucose monitoring systems for self-testing). This standard requires 95% of results within +/- 15 mg/dL of the reference for glucose concentrations below 100 mg/dL and within +/- 15% for concentrations at or above 100 mg/dL. No PPG-based glucose monitor has achieved this accuracy level in peer-reviewed validation studies, with most reporting mean absolute relative difference (MARD) values of 15-30% compared to the 10-12% MARD achieved by current subcutaneous continuous glucose monitors (Rachim and Chung, 2019; DOI: 10.1016/j.bspc.2018.09.006).

Practical Implications for PPG Device Developers

Understanding the standards landscape is essential for efficient product development. The key practical takeaways for engineers and researchers are:

First, define the intended use early. The regulatory classification and applicable standards are determined entirely by the intended use claims. A device measuring heart rate for fitness has fundamentally different requirements than one measuring SpO2 for clinical monitoring.

Second, plan for validation studies during the design phase, not after. The controlled desaturation study required for SpO2 validation takes 3-6 months to plan, execute, and analyze, and it requires specialized facilities and IRB approval. Designing sensor optics, LED wavelengths, and signal processing algorithms without considering the eventual validation requirements leads to costly redesign cycles.

Third, maintain traceability throughout development. IEC 62304 requires traceability from requirements through design to verification. Starting this documentation at the beginning of a project is far less burdensome than reconstructing it retroactively for regulatory submission.

Fourth, understand that standards are minimum requirements, not design targets. The best PPG devices substantially exceed the accuracy thresholds in the standards. Designing to merely meet the minimum standard leaves no margin for manufacturing variability, sensor degradation over time, or performance in edge cases (dark skin pigmentation, low perfusion, motion, nail polish).

The standards framework for PPG devices continues to evolve as the technology moves from traditional clinical pulse oximeters to wearable multi-parameter health monitors. Engineers who understand both the current requirements and the direction of standards development will be best positioned to build devices that are both clinically meaningful and regulatorily compliant. For further exploration of PPG signal fundamentals, visit our PPG technology overview and signal processing algorithms reference.