The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

A Comparison of the Water Handling Capability of Two Sidestream Capnographs

Chuck McGhee, RRT, Sacred Heart Medical Center, Eugene, Oregon

The use of mainstream capnography in managing mechanically ventilated patients has been the standard of care in the Adult Intensive Care Unit of our institution for nearly two decades. However, the clinicians in the Neonatal Intensive Care Unit have been reluctant to use mainstream capnography due to the increased weight and deadspace that occurred when the sensor was connected to the flow sensor of the ventilators. We purchased the NPB-75 (Nellcor, Pleasanton, CA) hand-held pulse oximeter/capnograph for the NICU. During their use, we experienced frequent blockages and system failures that we attributed to the water handling capability of the monitor. This led us to remove them from service, due to the reliability of the units and the high cost of repair. We then trialed a new 50 ml/minute sampling rate capnography system, the Dash CapnoFlex LF (GE Medical Systems Information Technology, Milwaukee, WI)

It was deemed easier to test the capabilities of the monitors in our adult ICU. We wanted to test both systems equally and putting two adapters in line in our NICU was not an option due to added dead space. After obtaining approval from the hospital's IRB for the comparison, the CapnoFlex LF and the NPB-75 were simultaneously connected to intubated patients in the Adult Intensive Care Unit. The airway adapters of each monitor were connected in tandem between the closed suction system adapter and the ventilator circuit wye. The patients' diagnoses included pneumonia, ARDS, sepsis, multiple traumas and included both genders. Observations were made periodically over the duration of the evaluation, with patient age, diagnosis and number of sample kits used by each monitor recorded by the observer.

Eight patients were studied with sessions lasting between 8 and 27.75 hours. On average, three NPB-75 sample kits were consumed for each CapnoFlex LF sample kit. This was caused by blockage of the sample line or filter of the NPB-75 sample kit. During the trial, two NPB-75 monitors failed due to water and contaminants being drawn into the system. A third NPB-75 was put into use, while the original CapnoFlex LF module was used without problems throughout the trial. Table 1 details the comparative experience with these monitors.

Table 1

CapnoFlex LF vs. NPB-75 Sample Kits Used
Date Sex Age Diagnosis Duration NPB-75 CapnoFlex
8/9/2004 F 57 R/O Pneumonia 24h 3 1
8/11/2004 F 72 Trauma 24h 4 1
8/16/2004 F 46 Trauma 24h 3 1
9/27/2004 F 24 Trauma 24h 3 1
11/1/2004 M 30 Trauma 27.75h 4 1
11/22/2004 F 76 Pneumonia, CHF 18.25h 3 1
12/29/2004 F 52 Acute respiratory failure 24h 3 1
1/4/2005 M N/A Respiratory failure 8h 1 1
Total=> 24 8

In this study, we found the CapnoFlex LF to be superior at managing humidity under ICU conditions to that of the NPB-75. The CapnoFlex LF required fewer sample kits per patient, which leads to significant cost reductions and the need for fewer interventions by staff. The CapnoFlex LF performed to the staff's expectations throughout the trial.

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