Pulm. Intraoperative monitoring and Difficult Airway Algorithm Flashcards
T/F: Pulse oximetry is NOT a mandatory intraoperative monitor.
False: Pulse Oximetry is a mandatory intraoperative monitor.
What are the wave lengths of light for pulse oximetry and which one measures what?
940nm=infared light, oxyhemoglobin absorbs more of the light, corresponds to 100% saturation.
660nm=red light, deoxyhemoglobin absorbs more of this light, corresponds to 50% saturation.
Saturation (SpO2) and PaO2
What is the “rough rule” relating oxygen saturation reading with PaO2?
PaO2: Saturation:
40 70
50 80
60 90
*remember 50% saturation=PaO2 27 (Hb P50 point)
Limitations of pulse oximetry:
What effect does Carboxyhemoglobin (COHb) poisoning have on pulse oximetry?
CO poisoning is recognized as oxyhemoglobin and the reading will be SpO2 of 100%.
Limitations of pulse oximetry:
Methemoglobin has what effect on pulse oximetry?
What are causes of Methemoglobin?
Absorbs light equally at both wavelengths, shows SpO2 of 85% regardless of the true oxygen saturation. Fe2+ (ferrous) is oxidized to Fe3+ (Ferric) form and cannot transport O2. Cyanosis is seen when 15% of Hb is in methemoglobin form.
Caused by nitrates, nitrites, sulfonamides, benzocaine
At what level of anemia will pulse oximetry be effected? (what Hgb/Hct?)
Hgb 3-4
Hct 12-16
Why does R heart failure (cor pulmonale) or tricuspid regurgitation disturb SpO2 readings?
RHF and tricuspid regurg cause venous pulsations in the dependent limb. the pulse ox is designed to assume pulsations are arterial.
Capnography: Rapidly and reliably indicates esophageal intubation but does not reliably detect _____?
it does not reliably detect endobronchial intubation.
What sensor/monitor is the Gold Standard for tracheal intubation?
End-tidal CO2!!!!!!
Listen to breath sounds, and also check for chest rise and fall.
In the movie Revenge of the Nerds, what was the name of their fraternity?
Lambda, Lambda, Lambda
What is the difference between a capnometer and capnograph?
Capnometer- measures CO2
Capnograph- records and displays CO2 readings
What are the 2 types of capnography (CO2 detection)?
Aspiration: continual suction of gas from breathing circuit. Prone to water precipitation.
Flow-through: sensor attaches directly to circuit.
A normal I:E ratio is ___? (Inspiratory: Expiratory)
For a patient with COPD, what would be a normal I:E ratio?
Normal I:E = 1:2
COPD I:E = 1:3 (prolonged expiratory phase)
dCO2:
What is the normal EtCO2 to arterial CO2 gradient? (or difference)
2-5mmHg (in Steven’s lecture)
5-10 mmHg (in Levi’s lecture-Nagelhout)
dCO2 reflects alveolar dead space=alveoli ventilated but not perfused.
Which should always be higher, PaCO2 or EtCO2?
PaCO2 will always be higher than EtCO2 due to mixing and dilution with the dead space.
