Frank cyanosis and oxygen saturation level

Q: 67 years old male collapsed at the hospital parking lot. "Code blue" is called. On arrival, patient appears to be in frank cyanosis. CPR is started, and the team proceeds to perform intubation. Cyanosis appears to be resolving with CPR and bagging via endotracheal tube (ETT). Frank cyanosis corresponds to an arterial oxygen saturation (SaO2) of around what percentage? - select one

A) 85%

B) 75%

C) 65%

Answer: C

Frank cyanosis usually does not develop until the arterial oxygen saturation (SaO2) level drops to around 65-67 percent. This corresponds to the level of deoxyhemoglobin of about 5 g/dL.

Although pulse oximetry is a great tool for assessing oxygenation, cyanosis often occurs in code situations or in ARDS, and pulse oximetry may not be able to pick up accurate parameters. Clinical exam may play a vital role.

Clinicians should understand that cyanosis is affected by many variables, such as peripheral perfusion, skin pigmentation, and hemoglobin concentration.

#oxygenation

#physical-exam

Reference:

Grace RF. Pulse oximetry. Gold standard or false sense of security? Med J Aust 1994; 160:638.