oxygen analysis, saturation Flashcards
0
Q
what does an oxygen analyzer do?
A
- an insturment which continually measures FiO2 in the breathing system
- indicates when inspired O2 deviates from desired limits (last line of defense against hypoxic mixtures being delivered to patient).
1
Q
what are the standards of anesthetic parctice for:
- o2 analyzers?
- pulse oximetry?
A
- necessary to have an oxygen analyzer and chart its readings for EVERY anesthetic
2.
2
Q
what is a hypoxic mixture?
A
a mixture that contains < 21% oxygen
3
Q
what are the different types of O2 analyzers?
A
- Paramagnetic analyzer
2. Galvanic (electrochemical) type oxygen analysis
4
Q
Parametric analyzer:
- How common is the use of a paramagnetic analyzer?
- is it a separate box or integrated?
- what machines is it used in?
- how (and in what machine) does the d-lite work?
- what is the upkeep and life of this instrument?
A
- most common type in current use
- usually intergrated into gas analysis monitors (not separate)
- used in datex capnomac. also in adu and aisys gas machines
- in the ADU, the d-lite pulls a gas sample into the gas analysis monitor for analysis
- needs much less care than galvanic type, lasts years
5
Q
Parametric analyzer:
How does it work?
A
- oxygen has strong parametric properties in comparison to others
- sample and room air are pulled into a strong electromagnetic field which is rapidly switched on and off
- the alternating pressure induced between sample and refrence gas is detected by a pressure transducer and amplified to produce a DC voltage signal whose strength is proportional to the difference between the 2 samples.
6
Q
Galvanic (electrochemical) oxygen analyzer:
- how does it connect to the machine? what brand of machines?
- what type of readings (intermittened or continuous)?
- what is the measurement referred as?
- flow in sensor is proportional to what?
A
- plug in; used in Fabius, Aestiva machines
- gives continuous readings
- amperometric (measures electrochemical energy)
- current flow in sensor is proportional to pO2 in sample
7
Q
Galvanic (electrochemical) oxygen analyzer:
- what are the parts of this analyzer?
- what does the gain control do?
A
- sensor (which is exposed to gas);
- analyzer box with circuitry
- meter
- alarms
- gain control - allows calibration to sample with known oxygen concentration
8
Q
Galvanic (electrochemical) oxygen analyzer: sensor-
- what is it ?
- why does it have a membrane on it?
- why does it have a thermister?
A
- an electrochemical sensor (a battery) that consumes a small amount of O2
- –consists of 2 electrodes surrounded by an electrolyte gel, separated from the gas sample by a membrane permeable to gasses but not liquids. - membrane is necessary to make current a linear function of pO2
- the thermistor compensates for temperature changes which affect the rate of diffusion
9
Q
oxygen saturation:
- what are the methods of measuring oxygen sat?
- what are attributes of each?
A
1a. invasive (from ABGs -via arterial line)
1b. non invasive (pulse oximetry (SpO2)
10
Q
what is a normal P50?
A
27 mmHg
11
Q
- what is oxygen content (CaO2) fourmula?
2. what does this mean in lay terms?
A
- CaO2= (1.34 x Hb x SaO2) + (paO2 x 0.003)
- Each gram of Hb carries a maximum of 1.34 mL of O2
this equals ~ 20 ml O2 per every 100 mL blood
12
Q
what are the 4 methods of oximetry?
A
- INVASIVE: via ABGs intermittently check pH, paCO2, as well as O2, can measure SaO2 directly with Co-Oximetry machine
- NON INVASIVE: via SaO2 (pulse ox) is continuous measurement
- TRANSCUTANEOUS pO2 measurement-
- OXIMETRIX: minaturized oxygen electrode may be mouned on the tip of a swan to follow mixed venous pO2
13
Q
transcutaneous pO2 measurement:
- used on whom?
- what type of electrode?
- how does it work?
- does it work on adults?
A
- used on neonates;
- uses a clark type electrode
- depends on warming the skin to dilate and “arterialize” the capillary beds below the skin
- skin must be thin with little adipose (doesnt work in adults).
14
Q
- what causes a shift to the right on the oxy-Hb scale?
2. what does a shift to the right do?
A
rise in: -temp -2,3-dpg -pH right=release (gives up oxygen to the tissues easier)
