Monday June 23, 2008

Scenario; You have been called to psychiatric floor to intubate a patient, who was found unconscious on floor. You felt thready pulse. You successfully intubated the patient and confirmed endotracheal tube placement by listening to bilateral chest and bright color change on CO2 detector. While RT (respiratory therapist) was applying ETT-holder you noticed thar Color change on CO2 detector stopped and remained purple. What is your next step?


A) Change CO2 detector and watch for color change.

B) You are probably in GI tract - so remove ET tube and reintubate.

C) Check for pulse and if no pulse is palpable, start CPR

D) Hook ET-tube to ventilator and watch for exhaled tidal volume

E) Ask nurse to check blood pressure with cuff

Answer: Check for pulse and if no pulse is palpable, start CPR

Always remember, CO2 detector may not change color if their is cardio-respiratory collapse. The visible color change of carbon dioxide detection devices depends on a minimum concentration of the gas reaching the detector. Pulmonary gas exchange (blood flow and delivery of CO2 to the lungs is low) may be inadequate to deliver the required concentration of carbon dioxide to the detector device in cardio-respiratory collapse.

False-negative readings (failure to detect CO2 despite tube placement in the trachea) have also been reported in association with pulmonary embolus because pulmonary blood flow and carbon dioxide delivery to the lungs are reduced. Also note, elimination and detection of CO2 can be drastically reduced following an intravenous bolus of epinephrine or with severe airway obstruction (eg, status asthmaticus) and pulmonary edema.

Another interesting scenario is - CO2 detector may display a constant color rather than breath-to-breath color change. This happens, if the detector is contaminated with gastric contents or acidic drugs (eg, endotracheally administered epinephrine).

In case, patient appears hemodynamically intact but if CO2 color change is not detected, a second method should be used to confirm endotracheal tube placement, such as direct visualization or the esophageal detector device.

Reference:
[Advanced Cardiovascular Life Support] Part 7.1: Adjuncts for Airway Control and Ventilation Circulation: Volume 112(24) Supplement13 December 2005pp IV-51-IV-57