The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

TUBING CIRCUIT COMPLIANCE COMPENSATION: A PHYSICIAN ORDERABLE SETTING OR NOT.

 

Joel Brown, RRT, Tim Cox, RRT, James H. Hertzog, MD. Departments of Respiratory Care Services and Anesthesiology and Critical Care Medicine, Alfred I. duPont Hospital for Children, Wilmington DE.

Background: Today microprocessor technology has a vital role in the function of mechanical ventilators. Most of these functions are used to enhance patient ventilator synchrony and do not change physician ordered ventilator settings such as: respiratory rate (RR), tidal Volume (Vt), positive end expiratory pressure (PEEP), peak inspiratory pressure (PIP), and inspiratory time (It). Tubing compensation is a function that is being implemented on several ventilators, but it is one of the enhancements that will alter physician ordered settings. Therefore, we evaluated the effect tubing compliance compensation has on Vt, and PIP at the point of the patient airway.

Methods: Three trials each were done on neonatal, pediatric and adult tubing with tubing compliance compensation on and off. The ventilator was calibrated prior to the start of each trial. The dry circuits were attached to a test lung with appropriate ventilator setting and lung compliance for each patient population. Inspiratory tidal volume (Vt insp), PIP and PEEP were measured at the airway using the Bicore pulmonary mechanic monitor. 

RESULTS:
Table: Vt, PIP, and PEEP measured at the vent monitor and airway with tubing compensation active and in-active.

Neo Tubing        
 SIMV RR30 Vt50 PEEP5 It0.5 Tubing Comp OFF Tubing Comp ON
Vt (ml) 50 47 51 57
PIP 11 11 13 13
PEEP 5 5 5 5
Ped Tubing        
 SIMV RR18 Vt300 PEEP5 It1.0        
Vt (ml) 299 261 303 308
PIP 26 26 28 28
PEEP 5 5 5 5
Adult Tubing        
SIMV RR12 Vt800 PEEP5 It1.33        
Vt (ml) 799 780 806 810
PIP 22 22 24 24
PEEP 5 5 5 5


Tidal volume and PIP increased in each trial considerably. Vt increase varied based on tubing type while PIP consistently increased by 2 cm H20.


CONCLUSION: 
Tubing compensation is an effective tool for ventilator management in the intensive care unit. But, it is important for the practitioner to be aware of the physical changes that occur when it is activated. As seen in our results, the ventilator will increase Vt, and delivered minute volume to the circuit, which would not be accounted for otherwise. The adjustment alters gas exchange and inevitably ventilator management. The failure to report or initiate a physician order for the use of tubing compensation can lead to misinterpretation of a patients pulmonary status. 

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