ETCO2

BT_SQ 1.6 Describe methods of measurement (including) … gas analysis, including capnography
BT_PO 1.29 Discuss regional ventilation-perfusion inequalities

Each of the following T/F statements applies to a cardiac arrest with CPR being performed

T / F  an ETCO2 of 15 mmHg would indicate good CPR

T / F  the PaCO2 will correlate with the ETCO2

T / F  the lower ETCO2 is due to a reduced venous CO2 content

T / F  the lower ETCO2 is due to absent aerobic cellular respiration

T / F  the lower ETCO2 is due to increased alveolar dead space

Can you provide a rationale for the correct statements above, from first principles? Hint… this blog relates to learning outcome BT_PO 1.29

 

BT_SQ 1.6 Oximetry

There have been a couple of posts on this topic before, but as we were talking about oxygen, I thought it might be worth revisiting.

Here is a comprehensive review of the sources of error with pulse oximetry, following a discussion of the principles. See the link to the CinderHK page below for more information on good references.

OLYMPUS DIGITAL CAMERA

Slightly off topic,  though I think fascinating, here is a picture of the absorption spectrum of different contaminants of glass. The glass used in long distance telecommunication fibre optic cables is ultra pure. The signal is transmitted in the IR spectrum, at about 1.5μm, such that the attenuation of the signal is only 0.2dB per km! I took this photo at the Hong Kong Science Museum.

BT_SQ 1.6 Describe the methods of measurement applicable to anaesthesia, including clinical utility, complications and sources of error in particular:

  • Oximetry
  • Plus heaps of others 😉

 

Pulsatile venous flow may cause an over estimation of SpO2                              TRUE/FALSE

The red:IR absorption modulation ratio (R) equals 1 at SpO2 85%                      TRUE/FALSE

Intravenous injection of indocyanine green causes a transient reduction in SpO2   TRUE/FALSE

The accuracy of SpO2 in humans has not been calibrated below 70%               TRUE/FALSE

Red nail polish is likely to cause inaccurate SpO2 readings                                  TRUE/FALSE

Nitrogen Analysis

BT_SQ 1.6 Describe the methods of measurement applicable to anaesthesia, including clinical utility, complications and sources of error in particular:

· Gas analysis, including capnography

 

I thought I would do a special post on Nitrogen, because it is a gas we use in most of our anaesthetics, but rarely monitor. It obviously is possible to measure it in real time, because nitrogen washout one of the methods used in the determination of FRC.

T/F Nitrogen can be measured using a paramagnetic analyser

T/F Nitrogen can be measured using a infra-red analyser

T/F Nitrogen can be measured using a gas discharge tube

T/F Nitrogen can be measured using a rapid response Clark electrode

T/F Nitrogen can be only be measured using a mass spectrometer