The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

Mechanical Ventilator "Liberation" Utilizing Non-Traditional Weaning Parameters in the Long Term, Acute Care Hospital (LTAC) Setting

 D. Orloff BS,RRT, J. Chaballa RRT, Department of Respiratory Care, Specialty Hospital at Kimball, Lakewood, NJ.

Background: Mechanical ventilator "liberation" or weaning is one primary goal at Long Term, Acute Care Hospital's (LTAC). The ventilator patients received to an LTAC unit are typically from acute care hospital ICU's that have failed several attempts at the mechanical ventilator liberation process and have undergone tracheotomy. Traditional weaning maneuvers (NIF, VC, RSBI) are utilized as well as the utilization of a monitor that is now available by Respironics, Inc. called the NICO. The NICO allows the practitioner to follow trends of exhaled Volumetric Carbon Dioxide (VCO2) on a breath by breath basis. Several additional parameters that are available on the NICO are end tidal carbon dioxide (ETCO2), alveolar minute volume (Ve alv.), and dead space to tidal volume ratio (Vd/Vt). VCO2 is the volume of expired CO2 per breath which is influenced by metabolism and/or circulation and perfusion. Ve alv. is the amount of effective tidal volume per minute that reaches the alveoli, and what is made available for gas exchange (normal range 2.5-3.5 mls/kg/min.). Pulmonary deadspace (Vd) is the component of ventilation that does not participate in gas exchange. Normal or "anatomic" Vd averages about 1 ml/pound (lb.) of body weight. In diseased states such as Chronic Obstructive Pulmonary Disease (COPD), Vd/Vt ratios can be increased altering the gas exchange ratio. 

Methods:  It was hypothesized that the liberation potential of patients received to our LTAC unit who possessed underlying pulmonary disease (COPD primarily) would have a high enough efficiency of ventilation for successful liberation to trach collar and/or decannulation. Patients were placed on a weaning protocol where a base line arterial blood gas, Vd/Vt ratio (NICO) and VCO2 (NICO) were collected. Traditional weaning parameters (NIF,VC,RSBI) were also collected. VCO2 was measured for a period of 24 hours to analyze breath by breath CO2 elimination looking for any downward trends in CO2 elimination (weaning failure). Vd/Vt was also trended looking for any changes/improvement in ventilation. Patients were termed "liberated" when they were able to stay off mechanical ventilation for a period of greater than 7 days consecutively.  

Results:   28 patients were admitted to our unit diagnosed with Ventilator Dependant Respiratory Failure (VDRF). Each patient had varying degrees of COPD. 8 patients (29%) were also on renal dialysis. The average age of our patients was 73. Patient weights averaged 77.8 kilograms (kgs.). The average Vd/Vt ratio was 0.64 [(range 0.52-0.77) all reversible underlying cardiopulmonary disease states were corrected]. VCO2 measurements averaged 157mls/kg./min. (67% of predicted value (using 3.0 mls/kg/min. as predicted)). 17 patients (60.7%) were liberated from mechanical ventilation and 7 (25%) patients were decannulated. The average number of ventilator days per patient was reduced from 18.91 to 11.17.  

Conclusions:  Non-traditional weaning parameters (VCO2, Vd/Vt ratio, Ve alv.) obtained by utilizing the NICO, provided additional assistance in mechanical ventilator liberation evidenced by a reduction in the average number of ventilator days per patient decreasing from 18.91 to 11.17. In the presence of moderate to severe lung disease, ventilator dependant respiratory patients with a reduction of VCO2 up to 33% and high Vd/Vt ratios (0.52-0.77) possess a high probability (60.7%) for successful ventilator liberation.

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