Alternate Methodology of Pulse Oximeter Validation

Pulse oximeters are non-invasive devices that use light to display an estimate (denoted by
SpO2) of the true arterial blood oxygen saturation (SaO2). The accuracy of the pulse oximeter
is determined from desaturation sequences (reduction in SpO2 from 100 to 70%) performed in
healthy volunteers. The current standard desaturation sequence is a step-wise reduction in 5%
SpO2 increments, achieved by reduction in inspired oxygen delivered by a gas blender such as
the ROBD (Reduced Oxygen Breathing Device). This mixes oxygen and nitrogen (components of
air) to produce the desired gas mixture. Throughout the desaturation sequence arterial blood
gas samples are drawn at each step. The blood gas samples are processed through a co-oximeter
to measure the SaO2. For each SaO2 measurement there will be a corresponding SpO2 recorded.
All data points from all subjects are amalgamated together to allow calculation of how well
SpO2 corresponds to the SaO2 throughout the range of 70 - 100% oxygen saturation. Accuracy,
A[RMS], is the unit of measure and this incorporates both bias and precision.

When the ROBD is used in a desaturation sequence, the subjects' arterial blood carbon dioxide
(CO2) level will initially be normal (normocapnia). With the reduction in SpO2 during the
desaturation sequence, the subjects' breathing rate will increase and this will cause the a
physiological reduction in the blood CO2 value (hypocapnia). The extent of hypocapnia will
vary from one subject to another. It is not known whether the presence of hypocapnia may have
an effect upon the accuracy measurement.

The RespirAct is a gas blender which, in contrast to the ROBD, can control both the oxygen
level as well as the carbon dioxide level. The end-tidal oxygen level (PAO2) is continuously
displayed by the RespirAct during the desaturation sequence. The PAO2 closely approximates to
arterial blood oxygen (PaO2) - the degree of closeness will be measured in the study. Through
an accepted formula, the SaO2 can be derived from the measured PAO2. The derived SaO2 values
can subsequently be used to measure the accuracy of the pulse oximeter. This A[RMS] can then
be compared with the A[RMS] calculated from the blood gas co-oximeter PaO2 / SaO2 values. If
the accuracies are comparable then this would remove the need for arterial line placement
during pulse oximeter validation studies.

Eligible healthy volunteers will complete five (5) oxygen desaturation sequences with
adjustment of sequence type and/or CO2 level. Two sequences will be delivered by step-wise
reduction and two will be delivered by gradual slope. Two sequences will be delivered at
normocapnia and two will be delivered at hypocapnia values. The ROBD sequence will be a
step-wise reduction with CO2 value set by the subjects' own breathing control.

Inclusion Criteria:

- Aged 18 - 50 years

- Subject is willing to provide written informed consent and is able to comply with
anticipated study procedures

Exclusion Criteria:

- Body Mass Index (BMI) < 18.0 or > 30.0

- Known significant respiratory, cardiovascular or medical condition that precludes
study participation as judged by investigator

- Anemia [hemoglobin value below lower range of normal for gender]

- Abnormal hemoglobin electrophoresis result

- Exposure to nicotine [positive test at screening or study day]

- Abnormal drug screen [positive test at screening or on day of study]

- Positive pregnancy test for females [serum test at screening; urine test on study day]

- Abnormal Allen's test for collateral circulation

- Abnormal Electrocardiogram

- Abnormal Pulmonary Function Test

- Abnormal venous blood gas result

- Intolerance of facemask