Friday, March 25, 2011

SmartCare "Too Short for This Ride"

I remember when I was younger how upset I got over the fact that I was too short to ride a stand up roller coaster. It would have been not so traumatic; however my younger brother of two years was able to ride and antagonized me the rest of the day.
Yes, I was the Husky (short & chubby) kid and isolated from sports where height is an advantage.

Being too short for riding a roller coaster or playing basketball is a common occurrence, however what about being too short for a mode of mechanical ventilation?
Now I’m not talking about neonatal vs. pediatric or pediatric vs. adult mechanical ventilation. I’m referring strictly to adult ventilation; can one be too short for a mode?

Evidently, yes one can be too short for SmartCare PS® (Draeger Medical) an intelligent mode of ventilation that is the only automated weaning ventilator mode in the United States that relies entirely on a rule-based expert system.

Previously I posted my initial concerns with the SmartCare software upgrade (The Not So Smart, Smart Care) and determined it would not add any benefit to my current patient population. I have recently reviewed the knowledge based rules yet again and noticed that patients that are vertically challenged may not progress to a spontaneous breathing trial.

Let me explain:

*      To progress to a spontaneous breathing trial the pressure support has to be at a predetermined minimum level.
*      To get to this minimal level of pressure support the ventilator has to decrease the pressure support based on a classification system.
*      There are eight (8) separate classifications and only two (2) allow for the reduction of pressure support.
*      The two classifications that allow for deceasing pressure support are: “Normal Ventilation” and “Hyperventilation”.
*      For these two classifications the tidal volume has to be > 250 ml for patients less than 55 kg & > 300 ml for patients > 55 kg.

This can be problematic in patients that normally breathe shallow, ≥ 4ml/kg/IDBW.


  1. Men whose heights are greater than 5’-2” (62 inches) their ideal body weight is over 55 kg. However at 5’-10” (70 inches) a tidal volume of under 300 (292) is still 4ml/kg/IDBW which may be significant to this patient.  So any male patient ≤ 70 inches with a tidal volume of 4ml/kg/IDBW would never be classified “Normal Ventilation”, most likely these patients would be classified “Insufficient Ventilation” .
  2. Women that are ≤ 6’-1” (73 inches) would run into the same circumstances as mentioned above.
  3. For male and female patients less than 55 kg the situation would be the same.

So again, SmartCare PS  may not be the ideal mode of ventilation for weaning mechanically ventilated patients.

New auto-weaning ventilator might make pulmonologist obsolete