Sunday, July 3, 2011

Capnography the Importance of Perfusion

Capnography/ETCO2 monitoring (ETCO2) has been used for many years in the operating room to confirm endo-tracheal tube placement and to evaluate the patient’s ventilatory status. Since the technology has become more portable and affordable, it has migrated to intensive care units, emergency rooms, ambulances, and even step down units. Due to this prevalence Capnography/End-tidal carbon dioxide monitoring is becoming the “fifth” vital sign [1].

Capnography is a very useful non-invasive tool to determine airway patency, evaluate ventilation status, titrate PEEP, evaluate lung recruitment vs. over-inflation, monitor patients for patient controlled anesthesia (PCA) over doses, etc. At a one institution I’m familiar with, ETCO2 monitoring has been implemented in cardiopulmonary arrests.

This is not a new concept; EtCO2 monitoring during resuscitation may provide insight on the mechanisms of arrest and evaluate the blood flow generated by external compressions [2].

When using EtCO2 monitoring during resuscitation healthcare providers need to remember the importance of perfusion and how the technology works.


Cardiac Arrest ONE

The patient was in full arrest and the EtCO2 monitor was used to evaluate airway patency. During auscultation of breath sounds I was manually bagging the patient; however compressions were ceased so the physician could listen. Breath sounds were audible bilaterally, however no Capnography waveform present. Someone (I won’t mention who) wanted to pull the E.T. Tube believing that the E.T. Tube was misplaced due to no Capnography waveform. I had to remind them that there was no perfusion present and wait to evaluate after compressions resumed. Once compressions were initiated the EtCO2 waveform was present.

Cardiac Arrest TWO

The patient was in full arrest and the EtCO2 monitor was used to evaluate airway patency and blood flow. Manual chest compressions were being performed as well as manual ventilation. The patient regained a pulse with an extremely low blood pressure and inotropics were initiated. I was bagging the patient with approximately 12 breaths per minute and the EtCO2 reading was 12 mmHG. Due to this low EtCO2 one of the health care practitioners (I won’t mention who) suggested that I slowed down my bagging, since I was hyperventilating the patient as evidence by the low EtCO2 reading. I had to kindly remind the practitioner about the perfusion part of ETCO2 and that the low ETCO2 reading was directly related to the patient’s extremely low blood pressure. I ensured them that once the blood pressure increases the EtCO2 will increase. Sure enough more inotropics were administered the patients blood pressure increased as well as the EtCO2 value (42 mmHg).

[1]. The Fifth Vital Sign: Respiratory Rate, Heart Rate, & Blood Pressure are the 3 standard. Pulse oximetry (4th), EtCO2 (5th).

[2]. Gazmuri, R. & Kube, E. (2003). Capnography During Cardiac Resuscitation: a clue on Mechanisms & a Guide to Interventions. Critical Care Forum. 7 (6): 411-412.