1997 OPEN FORUM Abstracts
COMPARISON OF IMPOSED WORK THROUGH TRACHEOSTOMY SPEAKING VALVES AND TRACHEOSTOMY TUBES USING A SPONTANEOUS BREATHING MODEL.
Robert J. Mortensen, CRTT, Michael S. Benson BS, RTT, Michael W. Sipes BA, RRT, David J. Pierson MD, Harborview Medical Center, University of Washington, Seattle, Washington.
INTRODUCTION: Tracheostomy speaking valves (TSV) are commonly used in patients with a tracheostomy. TSV are employed to enhance communication, decrease aspiration and improve swallowing mechanics. Knowledge of relative imposed work of breathing (WOBi) through TSV and tracheostomy tubes could guide clinicians in choosing the appropriate combination of TSV and tracheostomy tubes. In order to obtain this information we measured WOBi through five commercially available TSV and three different diameter tracheostomy tubes. Method: The five TSV studied were Montgomery (M), Passey-Muir (P), Instrumentation Industries (I), Olympic (O) and Shiley (S). Three different diameter Shiley tracheostomy tubes (6mm, 7mm, 8mm ID) were also studied. A Bio-Tek VT-1 test lung was modified to simulate spontaneous breathing in a sine wave pattern at Vts of 300, 500 and 700 ml respectively. IE ratio was held constant at 1:4 (flow range 32-75 L/min at a RR of 15/min). WOBi was measured using a Novametrix VenTrak 1550 respiratory mechanics monitor. In random fashion three valves from each manufacturer and one tracheostomy tubes of each diameter were tested. WOBi is the average of 10 breaths through each device minus baseline work (no valve or tube in line). The Anova Single Factor Test was performed on all devices at each Vt. Results:
Vt Valves Trach Tubes (ID)
M P I O S 6 mm 7 mm 8 mm
WOBi 0.306 0.401 0.604 0.519 0.423 0.828 0.524 0.335
SD± 0.007 0.015 0.006 0.027 0.015 0.003 0.003 0.003
p < 0.001 all valves Vt 700 ml. p < 0.001 all trach
tubes Vt 700 ml.
WOBi 0.205 0.269 0.443 0.279 0.271 0.560 0.327 0.225
SD± 0.010 0.010 0.024 0.021 0.014 0.003 0.003 0.002
p < 0.001 all valves Vt 500 ml. p < 0.001 all trach
tubes Vt 500 ml.
WOBi 0.151 0.168 0.283 0.117 0.159 0.242 0.143 0.095
SD± 0.003 0.005 0.005 0.014 0.003 0.002 0.001 0.002
p < 0.001 all valves Vt 300 ml. p < 0.001 all trach
tubes Vt 300 ml.
Conclusions: 1.) Under these study conditions, there are statistically significant differences in WOBi between all TSV and tracheostomy tubes; however all valves would be clinically acceptable for spontaneous breathing. 2.) Because WOBi through a TSV and tracheostomy tubes is additive, a combination of a higher work valve (I or O) and a smaller diameter tracheostomy tubes could produce unacceptable levels of work, especially in patients with minimal pulmonary reserve.