In April 2004 a questionnaire was sent to 7 well-known manufacturers of Pulse Oximeters in order to identify currently available models with re-usable sensors which would be suitable for use world-wide in medical and children’s wards.

2. Response

The 7 manufacturers responded with details of 24 models of pulse Oximeters. These are summarized in Table 1 and range in sophistication and cost from US$ 395 to US$ 4500. They have been listed in 3 categories: digit; hand-held; and portable. The categories are defined as follows:

Digit Integrated sensor and display, battery powered, for finger or toe. Cost about US$ 400.

Hand-Held Plug-in sensors, hand-held monitor with numerical display, battery or mains powered, may have alarms.Cost range US$ 475 to US$1255, depending on features.

Portable Plug-in sensors, small, portable monitor with numerical and possibly graphical display, mains powered via re-chargeable batteries, with alarms for high and low SpO2 and heart-rate and may have other alarms.Cost range US$ 1100 to US$ 4500 depending on features.

Other models There are other models available which combine pulse oximeters with capnographs and ECG monitors. These were not considered for this survey.

3. Criteria for Inclusion in Report

The criteria for models to be included in this report were suitability for use in medical and children’s wards, re-usable sensors, mains powered operation, easily moved form one patient to another, and alarms for both SpO2 and heart-rate.

An upper price limit for a pulse oximeter was set at US$ 1500, with additional costs for re-usable sensors. This broad specification was met by some of the portable and hand-held models listed in Table 1.

4. Models Not Considered

Some models listed in Table 1 were not considered in detail for one or more of the following reasons: they did not operate on mains power via a re-chargeable battery; they did not have alarms; their cost was too high.

5. General Specification

The pulse oximeters which are listed in Table 2 all reach the basic specification which meets the criteria given above. They are small, light, work on mains power 110V / 60Hz or 230V / 50Hz. The range of operating temperatures is at least 10 to 40 oC with a maximum relative humidity of at least 90%. They have 2 light sources at wavelengths of 660nm (red) and in the range 905 to 940nm (infra-red). High and low alarm values may be set for SpO2 and heart-rate. All models with re-chargeable batteries have an indication for low battery charge and, in some cases, an indication of mains power failure.

It was claimed that no special maintenance was needed for any of these models, although 2 manufacturers listed the cost of a replacement battery.

All except the Mediaid models had a related (more expensive) model capable of storing and downloading data collected over longer periods. In some cases the models listed had some data storage capability.

User and Service Manuals were provided. It was stated that all models had been tested for resistance to vibration and dropping but these tests had been carried out to different test specifications so the performance may not be comparable for all models.

The general characteristics of the pulse oximeters are summarized in Table 2.

6. CE Marking

All the models listed in Table 2 are CE marked, which means that they have been certified by a Notified Body to comply with the requirements of the European Medical Device Directive and are manufactured under a quality system which complies with ISO 13485:2000.

7. Summary of Data Provided

The details of replies to particular questions are summarized in Table 3 and are discussed in turn.

Battery Life This heading relates to the time for which the oximeter would function after mains power had been cut off. The longer, the better. This characteristic would be more important in areas which regularly have power cuts.

Display Type All the monitors have numerical display of SpO2 and heart-rate. Some of the monitors also had waveforms, bar graphs or plethysmographic displays.

Sensor Lifetime Sensor lifetime and cost are both important. It was stated on the questionnaire that the aim of the survey was to identify a limited number of re-usable sensors in order to simplify stock control. Since most sensors are company specific there is essentially only one source of sensors for each model, but all manufacturers can supply a wide range of different sensors.

Date of Introduction and Numbers Produced

The models listed are mostly of fairly recent introduction into the market and so have only reached comparatively low totals top date. However, the Mediaid 300 series was introduced in 1990-92, and the manufacturers state that more than 50,000 have been made. Model 3303 from Smiths was introduced in 1996 with 20,000 having been made.

In general, there is safety in longer production runs which give manufacturers the opportunity to deal with production problems.

It should however be noted that the response to a question about the reliability of pulse oximeters was very poor, apart from general claims that these devices do not often fail.

Maintenance Costs

All the manufacturers state that there is no specific requirement for maintaining pulse oximeters. Medair recommend an annual check of performance. The battery is probably the component most likely to fail. No data on the failure rate in actual use was provided. The major maintenance problem and cost clearly lies with the sensor, not the oximeter.

Warranty Cover

The User Manuals for these devices typically include a section defining terms of warranty for a stated period of time and warranty cover varies from one manufacturer to another. However, to quote one example, “items excluded from warranty are the batteries, power adaptor, sensor extension cable, sensors and other accessories”. Clearly these are the items most likely to fail or be damaged. The meaning of the term “guarantee”, as applied to a sensors lifetime has not been clarified with the manufacturers.

8. Summary

Seven manufacturers sent replies to the questionnaire on pulse oximeters which resulted in a list of 24 models varying in sophistication and cost from US$ 395 to US$ 4500. By applying three simple criteria this list of possible models was reduced to 5. Details of these 5 models are given in Tables 2 and 3. It is considered that, on the basis of the statements made by the manufacturers, these models all offer adequate performance and good value for money.

Contact details for the companies listed in Table 1 are given in Annex A.

Table 1

Pulse Oximeter Categories and List Prices