2002 OPEN FORUM Abstracts
ACCURACY OF A DISPOSABLE MANOMETER
SRT*, Teresa A. Volsko RRT, FAARC+
Youngstown State University, Youngstown, Ohio,* University Hospitals Health
System, Case Western Reserve University Cleveland, Ohio+
Background: Pressure manometers monitor airway pressures in all patient types during manual ventilation to assure ventilating pressures are adequate, but not excessive enough to contribute to barotrauma (J Trauma, 1996;40:320 322). We evaluated the Disposable Manometer (Mercury Medical®, Clearwater, Florida) in a laboratory setting to determine the accuracy and values for unlabeled reference markings on the manometer?s face. This manometer is a small,1-1/2 by 2 inches, lightweight spring-loaded device that can measure pressures between 5 and 60 cmH2O. The manometer?s face contains labeled reference values of 5, 10, 15, 20, 30, 40, and 60 cmH2O, as well as unlabeled reference markings, represented by a dot, which fall between each of the first five reference values. We hypothesize that the manometer design would prevent consistent accurate measurements during manual ventilation. We also sought to determine the approximate value of the unlabeled markings on the face of the manometer.
Methods: The Breath Tracker 1705 (Core-M Precision Instruments®, West Newton, MA) was used to perform measurements. It was zero calibrated then calibrated at 5, 10, 15, 20, 30, and 40 cmH2O with a U-tube manometer. The Breath Tracker was connected to the disposable manometer with small -bore connector tubing, a stop-cock, and a 60 mL piston syringe. Air from the syringe was injected until the pressure indicator (dial) on the manometer reached the center of the reference number and/or dot. The value displayed on the Breath Tracker was recorded, in cm H2O, for each of the numbered reference values and dots from 5 through 40 cmH2O. Ten manometers were tested and this procedure was repeated 3 times for each manometer. Mean (± SD) values and percent max error per reading were calculated for each marked reference value. Determination of the unlabeled reference markings was accomplished by calculating the mean of all the measured values (total of 30 measurements) for each of the unmarked reference dots on the 10 devices tested.
Results: Percent max error per reading and mean value of all readings is displayed in the table and graph below respectively. The calculated value of each unlabeled reference dot is displayed in the table below followed by a (*).
|Reference Value||5||8 (*)||10||14 (*)||15||19 (*)||20||24 (*)||30||40|
|Max Error (% of reading)||40||25||30||7||20||5||15||17||13||15|
Conclusion: The manometers displayed a small constant systematic error, with mean values falling close to the line of identity. The large max error may be attributed to the difficulty determining the target pressure relative to the true reading. This may pose a problem when attempting to monitor airway pressures during manual ventilation in the neonatal population.