The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

AIRWAY RESISTANCE IMPOSED BY ENDOTRACHEAL TUBES

William French, MA, RRT

Lakeland Community College , Kirtland , OH

Background

Airway resistance is a critical element in the management of patients receiving mechanical ventilation. Resistance imposed by artificial airways is an important part of that element, especially if the patient is doing any spontaneous breathing. However, as important as this element is, normal values for resistance through endotracheal (ET) tubes of different sizes is not published in common sources. Thus, the point of this study was to provide reference resistance numbers for various size ET tubes.

Methods and Materials

Measurements were made by attaching an Espirit ventilator (Respironics) to ET tubes ranging from 5.0 mm to 9.0 mm. The ET tube was attached to a test lung (Michigan Industries) set at a compliance of 0.05 L/cmH2O. The ventilator was set in volume control, tidal volume 600 mL, rate 12, square wave flow pattern. Two consecutive measurements were made and the results calculated by the ventilator with no variation. Data was reported in cmH2O/L/second.

Results

ET Tube size flow rate (L/m) resistance
5.0 40 19.5
5.0 60 28
5.0 80 34
6.0 40 8.1
6.0 60 12.5
6.0 80 15.6
7.0 40 4.6
7.0 60 6.7
7.0 80 8.7
8.0 40 3.0
8.0 60 4.2
8.0 80 5.6
9.0 40 2.0
9.0 60 2.6
9.0 80 3.4


 Conclusions

Clearly, this was a bench study, and the data should be viewed accordingly. However, the study does establish reference numbers for various size ET tubes. It is also interesting to note that the data follow what could be predicted from the math associated with airway resistance (R=∆P/flow).

You are here: RCJournal.com » Past OPEN FORUM Abstracts » 2006 Abstracts » AIRWAY RESISTANCE IMPOSED BY ENDOTRACHEAL TUBES