Saturday, April 16, 2011

Is the T-Piece Trial Futile? 3 Cases that Justify a T-Piece Trial.

In a current Blog posting “No More T-Piece” author Rick Frea states that at his facility T-piece trials are pretty much non-existent.

I don’t remember the last time I have preformed a T-piece trial on a patient with an E.T. Tube? It is very popular these days to perform the Spontaneous Breathing Trial (SBT) inline with the mechanical ventilator, due to the advance physiological monitoring and the extra alarm capabilities.

Most institutions I’m familiar with use a small amount of pressure support (~5 cmH2O) or Automatic Tube Compensation (a.k.a. Tube Comp, ATC, or Tube Resistance Compensation) if it is available on the machine to overcome the resistance of the artificial airway.

Even though the t-piece method is rarely used I believe it can be beneficial and more diagnostic in some cases to prevent false positives created by spontaneous breathing augmented with pressure support & PEEP.

3 examples:

1. Cost effective: The T-piece can be utilized in the post anesthesia care unit setting,  when the E.T. tube is needed for airway protection, however there is no need for a mechanical ventilator.

2. Pressure support may lead to additional air-trapping in obstructive patients if the cycle criterion setting is set too long. The air-trapping may lead to ineffective efforts (a.k.a. missed trigger attempts). These ineffective efforts are still diaphragmatic work however the ventilator will not measure these efforts.  When the operator calculates the frequency/tidal volume (f/Vt) based on the “machine” measured rate there may be a false positive.
 Example: patients true diaphragmatic rate equals 35, however 5 where ineffective efforts so the machine only measured 30.
Say they had an exhaled tidal volume of 300. If the calculated f/Vt was based on the measured value of 30 the patient’s f/vt would be 100 and acceptable. Conversely, the patient’s true f/vt is ~116 (35/ 0.300).

3. The cardiac patient with history of CHF, and dilated left ventricle. These patients respond very well to PEEP which increases their preload. So if their inotropic medications are not sufficient extubating these patients will result in flash pulmonary edema. 

Note- the practitioner does not need to place these patient’s on T-Piece trials they can be replicated through the ventilator, by performing a ZEEP (Zero End Expiratory Pressure) trial, as long as it’s a new generation ventilator.


Tobin: minimal PEEP & pressure support during SBT kills some patients

Myth Buster:ventilator weaning should be done on minimal settings (no T-Piece)

Performing a T-Piece trial through the ventilator.

The intrinsic diaphragmatic frequency.

ZEEP Trial.