Capnography Flashcards
PaO2 of 60 mmHg equals…
SaO2 of 90%
PaO2 of 40 mmHg equals…
SaO2 of 75%
The strength of non-covalent binds between two substances
Affinity
Describes the ability of hemoglobin to carry increased amounts of CO2 in the deoxygenated state
Haldane Effect
An increase in CO2 results in a decrease in blood pH, resulting in hemoglobin releasing their load of O2
Bohr Effect
Technology used in Pulse Oximetry
- Photoelectric (optical) plethysmography
- Spectrophotometry
- Light Emitting Diodes (LED)
Uses light absorption to produce waveforms from the blood pulsating in the vascular beds
Photoelectric (Optical) Plethysmography
The science that uses light wavelengths to measure light absorption through a substance, in our case blood
Spectrophotometry
Indications to for using Oximetry
- Noninvasive
- For continuous monitoring of arterial oxyhemoglobin saturation
- To monitor the adequacy of oxyhemoglobin saturation
Advantages of Pulse Oximetry
- Noninvasive
- Saturations can be monitored continuously at the bedside in real time
- Little training or knowledge is required to use the equipment
- Safe and usually quite accurate
Disadvantages of Pulse Oximetry
- Abnormal forms of Hb can not be measured
- HbCO is measured as HbO2 therefore false SpO2 readings
- Not as accurate as co-oximetry
Appropriate Oximetry Sites
- Finger
- Toe
- Ear
- Bridge of nose
- Forehead
- Infant: across the foot or hand
Factors that effect Accuracy of Pulse Oximetry
- Motion
- Low perfusion
- External lights
- False nails/Nail polish
- Wrongs types of sensor or incorrect placement (to light/loose)
- Dysfunctional Hb
- Anemia
- Vascular dyes
Partial pressure of CO2 in arterial blood
PaCO2
Measurement of the concentration of CO2 at the end of exhalation
EtCO2
Difference between EtCO2 and PaCO2 (normally 2-5 mmHg)
A-ADCO2
Measurement and the numerical display of CO2 at the patients airway
Capnometry
Measurement and waveform display of CO2 concentration at the patients airway
Capnography
Waveform display of CO2 throughout respiration
Capnogram
Indications for EtCO2
- Intubated applications
- Non-intubated
Intubated Applications
- Verifying ETT placement
- Monitoring ETT position during transport
- Head injury
- CPR (effectiveness, ROSC, Predictor of survival)
Non-Intubated Applications
- Bronchospastic disease (asthma, COPD)
- Hypoventilation states
- Shock states (sepsis, hypovolemia, anaphylaxis, cardiogenic)
- Hyperventilation
Normal values of PaCO2
35-45 mmHg
Normal values of EtCO2
35-45 mmHg
Causes of low EtCO2
- Mechanical (circuit disconnect, leaks)
- Respiratory (airway obstruction, bronchospasm, displaced ETT, hyperventilation, mucous plug)
- Circulatory (cardiac arrest, embolism, sudden hypovolemia)
- Metabolic (hypothermia)
Causes oh high EtCO2
- Mechanical (excessive mechanical dead space, faulty valve)
- Respiratory (COPD, respiratory depression or insufficiency)
- Circulatory (increased cardiac output)
- Metabolic (hyperthermia, malignant hyperthermia)