Tube Placement and Beyond by Alfred Sacchetti, MD

Alfred Sacchetti, MDEndotracheal intubation is one of the defining procedures of Emergency Medicine.  It is also one of the few procedures in medicine that we have to get right.  This doesn’t mean that we can never place an ET tube in the wrong spot.  In fact if you haven’t intubated the esophagus at some time in your career you are either not a practicing emergency physician or you are a liar.  

 

The key to successful endotracheal intubation is not recognizing when the ET tube is in trachea, but realizing when it is not.  Over the years we have been taught a myriad of clinical findings to confirm proper ET tube placement, all of which have failed at one time or another.  Over the last decade or so, capnometry has replaced physical examination as the only acceptable means of determining ET tube location.  

 

The current crop of carbon dioxide detectors fall into two categories, colormetric and quantitative.  The colormetric detectors use a litmus paper like reaction to detect exhaled carbon dioxide and change color from yellow to purple.   The quantitative detectors actually measure the specific amount of carbon dioxide exhaled and presents it as a waveform on a monitor screen along with a numeric readout of the peak expired CO2.  This number actually correlates to the pCO2 measured on an arterial blood gas.

 

A neonate with a wave form capnometer attached to the end of the ET tubeFrom an emergency medicine perspective colormetric capnometry is borderline useless and should be replaced at every institution by quantitative waveform capnometry.  

Both can detect esophageal intubation in patients with effective cardiac circulations and most cardiac arrest patients.  But that is not whole story.  Endotracheal intubation is not simply about placement of the ET tube, it also involved ventilation once the tube is placed and this is where colometric cpanometry misses the boat.  

 

At the time the tube is placed no one in the room is sure of the patient’s pCO2 or pH.  The respiratory technician or who ever is doing the manual bagging of the patient gives it a best guess and takes their best shot at a reasonable minute ventiloation.  An anxious tech or nurse may hyperventilate the patient, blowing off carbon dioxide resulting in cerebral vasoconstriction, neuronal ischemia and metabolic alkalosis.  A timid tech or nurse may hypoventilate the patient leading to hypercarbia, cerebral dilation and increased ICP.  Even the most experienced of clinicians cannot accurately balance the patient’s anatomic habitus and physiologic demands to produce a reasonable pCO2.  This potential for iatrogenic cerebral perfusion problems may be the reason for some of the poor outcomes with pre-hospital intubations. 

 

With waveform capnometry any clinican can match their manual ventilation to the patients respiratory needs.  The continuous end tidal CO2 read out provides immediate feedback to anyone doing the bagging of an intubated patient.  In fact as the director of a resuscitation, the physician need only instruct a technician to increase or decrease the rate or depth of bagging to maintain the CO2 readout within a very specific range.  This is enormously important in any critically ill patient.  This effect is magnified in pediatric and head injured patients in whom errors in minute ventilation can produce disastrous outcome results. 

 

A monitor scree with a capnometer, the capnometer waveform is the blue line. The end tidal CO2 is the number 34.

Quantitative waveform capnometry is the standard equipment in every operating room, is now recommended an essential piece of equipment for the care of pediatric ED patients and is even becoming a routine component of most portable monitor systems.   If your department does not have a waveform capnometer you are placing every intubated patient a increased risk for an adverse outcome, despite your spectacular management of their airway.  

 

So the next time you perform an intubation, consider exactly what information it is you need from your capnometer.  Do you want a simple color change to confirm tube placement or do you want breath to breath guidance that allows you to taylor the ideal physiologic conditions for your patient.

Comments

[Scott Oslund, M.D.]

Actually the colormetric changes from purple to yellow when the ETT is correctly placed.....remember, "if it's yellow, you're mellow".

[gerovital]

an article written by an expert. I do not understand all, but I tried subsequent

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