The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

SAMPLE LINE MODIFICATION TO AVOID MONITORING FAILURE ALARMS WHEN USING THE INOVENT WITH A FLUIDIC NASAL CPAP GENERATOR.

Michael Tracy RRT-NPS, Timothy R. Myers RRT-NPS. Rainbow Babies and Children's Hospital, Cleveland Ohio


Background:
As part of a multi-center clinical trial using nitric oxide (NO) for premature infants, we encountered monitoring failure alarms with the INOVent (Datex-Ohmeda, Madison, WI). Patients receiving NO who were extubated to fluidic CPAP (FCPAP) often caused the INOVent to read "monitoring failure" and loose digital read outs for NO, NO2 and FIO2. "Monitoring failure " occurs, in this scenario, when the sample inlet port of the INOVent is exposed to > 70 cm H2O pressure. Anecdotal fixes have been accomplished elsewhere by inserting a 3-way stop cock into the sample line and leaving the 3rd port open to the atmosphere or by creating a CPAP circuit hole to vent the excess pressure. The purpose of this study was to determine if a simple INOVent sample line modification could prevent the "monitoring failure" condition. We hypothesize a reconfiguration of the INOVent's sample line/inlet port interface would keep pressure in the CPAP circuit below the alarm threshold.

Methods:
10 consecutive FCPAP patients had the circuit pressure tested from +3 to +9 with the INOVent in line. Pressure was monitored by removing the thermister from the CPAP circuit's distal port, inserting a Sensormedic's elbow adapter with a female leur fitting and attaching an INOVent sample line connected to a calibrated pressure manometer. Circuit pressure was recorded and a notation was made when the "monitoring failure" alarm was activated. The high calibration gas "T" (INO-T part #6002-000-106) was modified by adding a male leur fitting (Cole Palmer) to the open end of the "T". The "T" was then inserted between the sample line and the inlet port of the INOVent. The "T" comes with a one-way check valve. After reconfiguration, pressure was monitored as the CPAP was increased from 3 to 9 cm H2O. Manipulations in flow required to maintain a desired CPAP level and monitoring failures were also noted.

RESULTS:
FIO2 and NO levels were measured with and without the "T" in line and were unchanged. Changes in pressure and flow are summarized in the table below.

CPAP CPAP with device CPAP Flow Required flow to stable CPAP Back Pressure without Device Back Pressure with Device Meter Failure without device Meter Failure with device
3 2.5 ± 0.4 7.0 ± 0.6 7.6 ± 0.6 61.9 ± 8.2 1.5 ± 0.7 0.0% 0.0%
4 3.2 + 0.3 7.9 ± 0.7 8.3 ± 0.6 76.0 ± 8.4 2.0 ± 0.0 70.0% 0.0%
5 4.2 ± 0.2 8.3 ± 0.5 8.9 ± 0.6 85.5 ± 7.2 2.1 ± 0.3 40.0% 0.0%
6 5.1 ± 0.2 8.9 ± 0.5 9.5 ± 0.8 101.6 ±7.8 2.3 ± 0.5 100.0% 0.0%
7 6.1 ± 0.2 9.5 ± 0.8 10.3 ± 1.4 113.8 ±5.6 3.2 ± 0.6 100.0% 0.0%
8 7.0 ± 0.2 10.6 ± 1.5 11.3 ± 1.5 117.6 ±2.6 2.6 ± 0.5 100.0% 0.0%
9 7.8 ± 0.5 12.0 ± 1.7 12.8 ± 2.1 118.4 ±0.9 4.2 ± 0.3 100.0% 0.0%



Conclusions:
1) Use of the modified high cal gas "T" in the sample line keeps the CPAP circuit pressure below the "monitoring failure" threshold. 2) Changes in delivered CPAP are consistent. 3) Compensation for loss of pressure is consistent and easily obtained at CPAP levels used clinically at our institution. The use of the modified high calibration gas "T" is a safe and effective way to prevent "monitoring failure" alarms with the INOVent and FCPAP generator.

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