Physics - Measurement Methods

Question 1

CO2 conc. measurement in anesthetized patient

Answer 1

1. Direct: Severinghaus CO2 electrode

2. Indirect
I) From gas: 
Capnograph,
Mass spectrometer,
Haldane apparatus,
Interferometer / gas chromatograph

II) From blood: 
ABG,
Transcutaneous electrode,
Van slyke apparatus, 
Siggar Anderson nomogram

Question 2

O2 conc. measurement in anesthetized patient

Answer 2

A) Measurement of O2 saturation:
Spectrophotometric measurement
ABG
Pulse oxymetry

B) Measurement of O2 tension:

I) Intermittent measurement:
Paramagnetic analyzer,
Fuel cell,
ABG

II) Continuous measurement:
Mass spectrometer,
O2 electrode

Question 3

Parts of Fuel cell

Answer 3

Anode: Lead

Cathode: Gold mesh

Electrolyte solution: KOH

Question 4

Parts of O2 electrode

Answer 4

Anode: Silver chloride wire

Cathode: Platinum

Question 5

Advantage of fuel cell

Answer 5

1. No battery required
2. Portable
3. Reliable analyzer for bedside use
4. Inexpensive
5. Not affected by water vapor

Question 6

Disadvantage of fuel cell

Answer 6

1. Long response time (about 30 sec)
2. Detector cells are exhausted due to continuous exposure. So limited life span and not replacable
3. Affected by temperature

Question 7

Methods of BP measurement

Answer 7

Invasive
1. Arterial cannulation: Radial, Femoral, Axillary, ADP

Noninvasive

  1. Palpation
  2. Oscillometry (NIBP)
  3. Auscultation (Aneroid gauge)
  4. Doppler probe
  5. Arterial tonometry
  6. Penaz technique (IR)

Question 8

Gas flow measurement

Answer 8

1. Variable orifice flowmeter:
   a) Rotameter
   b) Wright peak flow meter
2. Fixed orifice flowmeter:
   a) Pneumotachograph
   b) Aneroid gauge
   c) Pitot tubes
3. Other devices:
   a) Hot wire flowmeter
   b) Ultrasonic flowmeter

Question 9

Gas volume measurement

Answer 9

1. Benedict roth spirometer
2. Vitalogaph
3. Dry gas meter
4. Wrigt’s respirometer
5. Dragger volumeter
6. Pneumography
7. Electric volume monitor

Question 10

Fluid flow measurement

Answer 10

1. Fick principle
2. Ultrasonic flowmeter
3. Electromagnetic flowmeter
4. Dye dilution
5. Thermal dilution
6. Plethysmograph

Question 11

Relative humidity measurement

Answer 11

1. Hair hygrometer
2. Regnault hygrometer
3. Wet and dry bulb hygrometer
4. Psychrometer

Question 12

Absolute humidity measurement

Answer 12

1. Transducer
2. Mass spectrometer
3. Light absorption
4. Thermal conduction
5. Regnault hygrometer
6. Electrolysis hygrometer
7. IR hygrometer

Question 13

Fluid volume measurement

Answer 13

1. Measuring cylinder

2. Dye dilution

Question 14

Temperature measurement

Answer 14

1. Direct reading / non electrical thermometers:
      A. Liquid expansion thermometers: 
                  Mercury thermometer, 
                  Alcohol thermometer.
      B. Gas expansion thermometers: 
                  Aneroid gauge
      C. Dial thermometer: 
                  Bourdon gauge type
      D. Chemical thermometer:
                  Reversible chemical thermometer
      E. Disposable chemical thermometer
      F. IR thermometer: 
                  Pyroelectric sensor, 
                  Thermopile sensor

2.Remote reading / Electrical thermometers:
A. Thermistor
B. Thermocouple
C. Platinum resistance