Справочник Пользователя для Innokas Yhtyma Oy VC150

8-16

VC150 Vital Signs Monitor

KO00065K

: Masimo rainbow

®

 SET

®

 SpO

2

 and special features

In the case of SpO

2

, different results are usually obtained from the arterial blood 

gas sample if the calculated measurement is not appropriately corrected for the 
effects of variables that shift the relationship between the partial pressure of 
oxygen (PO

2

) and saturation, such as: pH,temperature, the partial pressure of 

carbon dioxide (PCO

2

), 2,3-DPG, and fetal hemoglobin. In the case of SpCO, 

different results are also expected if concentration of methemoglobin in the 
blood gas sample is abnormal (greater than 2% for methemoglobin 
concentration).

High levels of bilirubin may cause erroneous SpO

2

, SpMet, SpCO, and SpHb 

readings. As blood samples are usually taken over a period of 20 seconds (the 
time it takes to draw the blood) a meaningful comparison can only be achieved if 
the oxygen saturation, carboxyhemoglobin, and methemoglobin concentration 
of the patient are stable and not changing over the period of time that the blood 
gas sample is taken. Subsequently, blood gas and laboratory CO-Oximetry 
measurements of SpO

2

, SpCO, SpMet, SpHb, and SpOC may vary with the rapid 

administration of fluids and in procedures such as dialysis. Additionally, drawn 
whole blood testing can be affected by sample handling methods and time 
elapsed between blood draw and sample testing.

Measurements with Low Signal IQ should not be compared to laboratory 
measurements.

Oxygen (O

2

) is carried in the blood in two forms, either dissolved in plasma or 

combined with hemoglobin. The amount of oxygen in the arterial blood is 
termed the oxygen content (CaO

2

) and is measured in units of ml O

2

/dL blood. 

One gram of hemoglobin (Hb) can carry 1.34 ml of oxygen, whereas 100 ml of 
blood plasma may carry approximately 0.3 ml of oxygen*. The oxygen content is 
determined mathematically as:

Where HbO

2

 is the fractional arterial oxygen saturation and PaO2 is the partial 

pressure of arterial oxygen.

For typical PaO

2

 values, the second part of the above equation (PaO

2

 [mm Hg] x 

[0.3 ml O2/ 100 mm Hg/dL]) is approximately 0.3 ml/dL. Furthermore, for typical 
carboxyhemoglobin and methemoglobin levels, the functional saturation (SpO

2

) 

as measured by a pulse oximeter is given by: