Week 8 Monitoring, Diff't Airway

Question 1

Pulse oximetry is a ________ intraoperative monitor. The 2 wavelengths associated with pulse ox are:

Answer 1

Mandatory
940nm = infrared light, oxyhemoglobin absorbs more of this light, corresponds to 100% saturation
660nm = red light, deoxyhemoglobin absorbs more of this light, corresponds to 50% saturation

Question 2

Corresponding Saturation with PaO2
100
95
90
75
60
50

Answer 2

Saturation PaO2 100 100+ 95 75 90 60 75 40 (mixed venous blood in pulm. artery)
60 30 50 27 (Hb P50 point)

Question 3

Limitations of pulse oximetry include:

Answer 3

A standard pulse ox. CANNOT be used in MRI – may burn patient, dedicated MRI probe needed
AND
Endobronchial intubation will usually go undetected by pulse ox. in the absence of lung disease or low FiO2
AND
No pulse present, low peripheral perfusion

Question 4

Limitations of pulse oximetry Hemoglobin variants include:

Answer 4

Carboxyhemoglobin (COHb) – from CO poisoning is viewed as oxyhemoglobin by pulse ox. and shows a SpO2 of 100%, this is an overestimation of the true oxygenation, co-oximeter used to distinguish between the two
Methemoglobin (MetHb) – Fe+2(ferrous) in Hb is oxidized to Fe+3 (ferric) form and cannot transport O2, cyanosis seen when 15% of Hb is in methemoglomin form, caused by nitrates, nitrites, sulfonamides, benzocaine (hurricane spray), nitroglycerine (NTG), nitroprusside (SNP), absorbs equally at both wavelengths, 1:1, shows a SpO2 of 85% regardless of the true oxygen saturation, Tx’d with low dose methylene blue or ascorbic acid

Fetal hemoglobin and bilirubin do not affect pulse oximetry

Question 5

__________ Rapidly and reliably indicates esophageal intubation but does not reliably detect endobronchial intubation

Answer 5

Capnography

Question 6

is gold standard for tracheal intubation

Answer 6

+ETCO2