The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

Leak Compensation Comparisons in Mechanical Ventilation

Jessica Patnaude, RRT, Keisha Smith, CRT, Ryan Totten, CRT, Joe Warren, CRT, & Aaron Light BSRT RRT Ozarks Technical Community College, Springfield, MO

Background:  A bench test was performed comparing leak compensation on the Maquet Servo i, Drager Evita 4, and the Viasys Avea. Using the same ventilator circuit for each ventilator a leak was created by opening the saline port on a Ballard suction catheter. Using the same ventilator settings the peak pressure, minute volume, measured rate, and exhaled tidal volume were measured.  The intrinsic peep was measured by a Hans Rudolph Series 1101 breathing simulator. This study will confirm which ventilator tolerates a leak with a minimal change in parameters.

Method: A piece of large bore tubing was connected to a Hans Rudolph Series 1101 breathing simulator. Then a size 7.0 mm endotracheal tube was placed in the tubing and the cuff inflated to make sure there was no leak.   Each ventilator was then attached to the endotracheal tube (ETT) using the same ventilator circuit. A Ballard closed system catheter was also placed in line with the circuit at the ETT.  The breathing simulator was set for a resistance of 7 cmH20/l/sec, compliance of 40 ml/cmH20, and a set breath rate of 12.  All ventilator parameters were set the same (VT 500ml, f 12, PEEP 5 cmH20, I.T. 1.2 seconds). The Viasys Avea and Maquet Servo I were placed in the pressure regulated volume control mode of ventilation while the Drager E4 was placed in CMV with auto-flow. The sensitivity on all ventilators was set for flow trigger.  PIP, VE, measured f, exhaled VT and intrinsic PEEP was then noted without a leak.  A leak was created by uncapping the saline port on the Ballard suction catheter and then all parameters were then noted with the leak.

Results:

                                                 

Drager  Evita 4     Without Leak With Leak
Peak Pressure 18 cmH2O 18 cmH2O
Minute Volume 5.7 L/min 5.2 L/min
Measured Rate 12 bpm 12 bpm
Tidal Volume Exhaled 489 ml 439 ml
Intrinsic PEEP 5 cmH2O 4.2 cmH2O


                                                            

Viasys Avea        Without Leak  With Leak
Peak Pressure 18 18
Minute Volume 6 6.5
Measured Rate 12 19
Tidal Volume Exhaled 460 350
Intrinsic PEEP 4 4


                                               

Maquet Servo I    Without Leak    With Leak
Peak Pressure 19 13
Minute Volume 5.7 5
Measured Rate 12 14
Tidal Volume Exhaled 493 378
Intrinsic PEEP 5 3

Conclusion:  The Drager Evita 4 ventilator performed the best with minimal changes in measured parameters.  The Viasys Avea showed signs of auto triggering but did not decrease the peak inspiratory pressure in response to the leak.  The Maquet Servo i did not perform as well as the other two ventilators. Not only did it auto trigger but also the peak inspiratory pressure decreased in response to the leak. We believe this drop in pressure is due to the ventilator sensing the leak was a sign of improved lung compliance.

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