Chapter 5: Oximetry
Operation Manual SurgiVet V3395
5-1
Chapter 5: Oximetry
General Description
The SurgiVet V3395’s Oximeter noninvasively and continuously monitors and displays arterial
blood oxygen saturation (SpO
2
), pulse rate, and plethysmogram. The V3395 beeps with each
pulse beat. The pitch of the pulse beep depends on the SpO
2
value; the higher (or lower) the SpO
2
value, the higher (or lower) the pulse beep pitch.
The V3395 flexible alarm system lets you choose alarm parameters and audible tone volumes.
You can select the high and low alarm limits for SpO
2
and pulse rate, and independently choose
the volume for alarm and pulse beep tones.
Pulse Oximetry Theory of Operation
The SurgiVet V3395 determines SpO
2
and pulse rate by passing two wavelengths of light, one red and
one infrared, through body tissue to a photo detector. Pulse identification is accomplished by using
plethysmographic techniques, and oxygen saturation measurements are determined using
spectrophotometric Oximetry principles. During measurement, the signal strength resulting from each
light source depends on the color and thickness of the body tissue, the sensor placement, the intensity
of the light sources, and the absorption of the arterial and venous blood (including the time varying
effects of the pulse) in the body tissues.
FIGURE 5.1: PULSE OXIMETRY THEORY OF OPERATION
1.
Low intensity red and infrared LED light sources
2.
Detector
The monitor processes these signals, separating the time invariant parameters (tissue thickness,
skin color, light intensity, and venous blood) from the time variant parameters (arterial volume
and SpO
2
) to identify the pulse and calculate oxygen saturation. Oxygen saturation calculations
can be performed because blood saturated with oxygen predictably absorbs less red light than
oxygen depleted blood.
Since measurement of SpO
2
depends on a pulsating vascular bed, any condition that restricts
blood flow, such as use of a blood pressure cuff or extremes in systemic vascular resistance, may
cause an inability to determine accurate pulse and SpO
2
readings.
