The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Quan M. Nguyen1, Shubhra Ghosh1, Clarence G. Finch1, Kristen J. Price1

Background: Negative inspiratory force (NIF) measurement is a routine component of pulmonary mechanics done in mechanically ventilated (MV) patients prior to attempting weaning/extubation. NIF measures the strength of inspiratory lung muscles which is an indicator of patient's readiness for successful extubation. NIF is usually measured with a reusable external manometer connected to ETT via a disposable adapter. In most institutions, therapists take 3 measurements and use the highest value to report the maximum inspiratory pressure. This requires instrument calibration before every use. Also, this method carries a risk of cross contamination between patients. This is even more significant in the frequently immunocompromised cancer patients. Recently a disposable manometer has become available which does not require calibration and is for single-patient use. Our objective for this study was to compare NIF measurements as obtained by the new disposable device with the conventional manometer measurements.

Methods: NIF measurements were obtained using the conventional manometer and the disposable manometer in all the patients undergoing assessment for weaning/extubation readiness. MV was reinstated between measurements to optimize results.

Results: NIF measurements using the conventional manometer and the disposable NIF manometer were obtained in 18 critically ill, MV cancer patients as a part of their assessment for weaning readiness (figure 1). Fifteen patients (83%) were alert and awake during the NIF measurements. Among these patients the median pressure difference between the two devices was 1 cm H2O (mean = 3, range 0 - 5). Three patients (17%) were not fully alert and awake during the assessment and among them the median pressure difference was 10 cm H2O (mean = 10, range 7 - 12).

Conclusion: In an effort to minimize the rising healthcare costs in MV patients, prevention of infections has become a primary focus in respiratory care practice. Disposable devices are in vogue since they do not carry the risk of cross contamination when properly stored. Availability of a disposable NIF manometer which offers accuracy comparable to conventional devices deserves serious consideration for use in weaning/extubation readiness assessment. Its ease of use and no need for calibration provides added advantage. The use of disposable NIF manometer should be studied further for the possibility of its implementation as the manometer of choice for NIF measurements.