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.