1. Purpose and Scope

This bulletin explains the Cyanosis Observation Index (COI) requirements in AS/NZS 1680.2.5:2018 – Interior and workplace lighting – Part 2.5: Hospital and medical tasks, and how they apply to hospital treatment areas. It integrates course material and standard requirements and is intended for:

• Electrical and lighting designers

• Hospital engineers and facility managers

• Clinical stakeholders involved in the design and evaluation of treatment areas

2. Clinical Context: Cyanosis and Visual Observation

A significant aspect of clinical observation in hospital treatment areas is the reliable detection of cyanosis – the bluish discolouration in the skin and mucous membranes indicating that oxygen saturation in the blood is dangerously low.

While pulse oximeters are routinely used in operating rooms and recovery areas, there are areas within hospitals where these devices are not universally used, and there are patients and conditions where pulse oximetry can be unreliable. For example:

• Patients with poor peripheral circulation

• Some shock states and vasoconstrictive conditions

• Situations where sensors cannot be placed or maintained reliably

In these instances, the ability of medical staff to detect the onset of cyanosis by visual observation may be critical to a patient’s wellbeing.

Because perceived skin and mucous membrane colour depend strongly on the spectral power distribution (SPD) of the light source, cyanosis‑critic alareas require lighting that meets the COI, CCT and CRI criteria set out inAS/NZS 1680.2.5:2018.

3. Origin and Definition of the Cyanosis Observation Index

Using data from trials and the known reflective properties of blood, along with the spectral properties of commercially available lamps, a methodology for calculating a Cyanosis Observation Index (COI) was established and published in 1975. This has since been revised and re‑published in its current form in AS/NZS 1680.2.5:2018.

The Australian requirement for cyanosis lighting is intentionally demanding. The Standard defines the Cyanosis Observation Index(COI) as:

• An open‑ended numerical scale which ranks an artificial light source for the purpose of visual observation of cyanosis.

• A dimensionless number that is a function of the spectral power distribution of the lamp.

Interpretation:

• Lower COI → better performance for visual detection of cyanosis.

• COI is not a measure of brightness; it is a colour‑appearance index specifically tied to blood oxygenation cues.

4. COI Calculation Method (Conceptual Overview)

The COI methodology models how blood of different oxygen saturations appears under a test light source compared to a reference source.

4.1 Measurement Inputs

• Spectral power distribution (SPD) of the test light source

– Measured in 5 nm steps between 380 nm and 760 nm.

• Spectral reflectance of blood at two states:

– Fully oxygenated blood (100% oxygen saturation)

• Cyanosed blood (50% oxygen saturation)

4.2 Reference Source

• A 4000 K Planckian (blackbody) source is used as thereference lamp.

– Blood colour under the test lamp is compared to blood colour under this reference source.

4.3 Calculation Steps

1. Combine the test lamp SPD with the spectral reflectances of100% and 50% oxygen‑saturated blood to obtain tri stimulus values/colour coordinates for each blood state under the test lamp.

2. Repeat the calculation for the 4000 K reference source.

3. For each blood state (100% and 50%), compute the difference i n chromaticity (colour) between test lamp and reference lamp.

4. Average the chromaticity differences for the 100% and 50%states. This average is taken as the Cyanosis Observation Index (COI) for that light source.

Note (critical for practice):
Spectral analysis of the light source must be available from the manufacturer or obtained via laboratory testing to calculate COI. Without the spectral characteristics of the light source, COI cannot be determined.

5. AS/NZS 1680.2.5:2018 – Performance Requirements

To comply with AS/NZS 1680.2.5:2018 for reliable diagnosis of cyanosis, a light source used in relevant treatment areas must satisfy all of the following:

5.1 Cyanosis Observation Index (COI)

• COI must be ≤ 3.3.

• The lower the value of the index, the better the light source is deemed to be for cyanosis observation.

5.2 Correlated Colour Temperature (CCT)

• The CCT of the light source must be between 3300 K and 5300K.

• This range avoids excessively warm or excessively cool light that could distort skin colour or mask early cyanosis.

5.3 Colour Rendering Index (CRI)

• The CRI (Ra) of the lamp must be ≥ 80.

• This ensures generally acceptable colour rendering for abroad range of clinical tasks, in addition to cyanosis‑specific performance.

5.4 Summary of Key Technical Criteria

• Cyanosis Observation Index (COI) ≤ 3.3

• CCT between 3300 K and 5300 K

• CRI (Ra) ≥ 80

• SPD measured 380–760 nm in 5 nm steps for COI calculation

• COI lower value = better cyanosis observation performance

6. Hospital Areas Requiring Cyanosis Lighting

Every hospital has an implied Duty of Care under OHS legislation to provide and maintain the facility in accordance with currentAustralian Standards.

Clause F3 in Appendix F of AS/NZS 1680.2.5:2018 defines the differentiation of treatment areas in a hospital. Because of the variety ofprocedures and corresponding lighting needs, treatment areas are categorisedfor application in Table F1 of the Standard:

6.1 Treatment Area Categories (Clause F3)

(a) Type A areas

• Areas where anaesthesia or intravenous sedation is requiredas part of the procedure.

• Cyanosis observation lighting may be required in theseareas, as accurate assessment of patient colour is often critical before,during and after sedation/anaesthesia.

(b) Type B areas

• Areas where observation of the skin colour of patients is important, but anaesthesia or intravenous sedation is not required.

• These areas typically involve ongoing clinical observation where cyanosis may be a key indicator of deterioration, so COI‑compliant lighting is commonly needed.

(c) Type C areas

• General examination and treatment rooms, i.e. areas other than Type A and Type B.

• The need for cyanosis‑compliant lighting is more task‑dependent,but should be considered if colour‑based assessment is part of routine care.

6.2 Responsibility for Determining COI‑Compliant Areas

The decision as to which part(s) or areas of the hospital require COI‑compliant lighting is made by:

• The hospital management team,

• In conjunction with the electrical services engineer or lighting designer, and

• With input from clinical staff.

They must review:

• The clinical function of the area

• The criticality of colour‑based observation (e.g. detectionof cyanosis, pallor, jaundice)

• The guidance of Clause F3 and Table F1 in AS/NZS1680.2.5:2018

• The hospital’s OHS Duty of Care and internal risk management policies

In practice, cyanosis‑compliant lighting is commonly applied to:

• Emergency departments, resuscitation areas, operating theatres, induction and recovery rooms

• Intensive care units (ICU) and high‑dependency units (HDU)

• Observation bays and other treatment spaces where rapidrecognition of patient deterioration is essential

(Exact area lists and illuminance values should be taken directly from AS/NZS 1680.2.5:2018 and the broader AS/NZS 1680 series.)

7. Design, Specification, and Maintenance Guidance

7.1 Design and Specification

When designing or refurbishing areas that may require cyanosis lighting:

Include COI in project specifications for relevant spaces:

• “Luminaires in cyanosis‑critical areas shall have COI ≤ 3.3,CCT 3300–5300 K, CRI ≥ 80, demonstrated by manufacturer test reports inaccordance with AS/NZS 1680.2.5:2018.”

Request full photometric and spectral data from manufacturers:

• SPD (380–760 nm in 5 nm increments)

• COI value, CCT, CRI, and (where available) R9

• Confirmation that values apply at luminaire level, not justLED chip level

Check tuneable or multi‑channel systems:

• Ensure all clinical presets/operating modes used for examination remain within the specified COI, CCT and CRI ranges.

7.2 Installation and Verification

• Ensure that installed luminaires in Type A and Type B areas match the specified models and performance data.

• Where possible, keep manufacturer’s COI reports and SPD files on record for compliance audits and future refurbishments.

7.3 Maintenance and Replacement

• Record COI, CCT and CRI requirements in the asset register.

• When replacing luminaires, confirm that replacement products provide equivalent or better COI performance and remain within the required CCT and CRI ranges.

• Review COI performance if there are major changes in lamp technology (e.g. moving from fluorescent to LED) in critical areas.

8. Key Takeaways

• Cyanosis Observation Index (COI) is a dimensionless, open‑ended index that ranks light sources by how well they support visual detection ofcyanosis.

• COI is based on colour differences of blood at 50% and 100% oxygen saturation under the test lamp compared with a 4000K Planckian reference source, using SPD data from 380–760 nm in 5 nm steps.

• Under AS/NZS 1680.2.5:2018, for areas where reliable cyanosis observation is required:

– COI ≤ 3.3

– CCT between 3300K and 5300K

– CRI ≥ 80

Treatment areas are categorised as Type A, B, and C; the need for cyanosis‑compliant lighting is determined collaboratively by hospital management, clinical staff, and lighting/electrical designers, guided by ClauseF3 and Table F1 and by the hospital’s Duty of Care under OHS legislation.

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