American Journal of Respiratory Critical Care Medicine, 1994
Authors: C. Van Surell, B. Louis, F. Lofaso, L. Beydion, L. Brochard, A.
Harf, J. Fredberg, and D. Isabey
Conclusion: “This study has demonstrated the feasibility of the acoustic reflection method in the intensive care unit and that the decrease in hydraulic diameter and the change in area profile are both linked to ETT obstruction by mucus deposition. However, routine monitoring and clinical management of patients appear more difficult with the hydraulic method because (1)connection to a pneumotachygraph, (2)introduction and positioning of a pressure catheter in the ETT, and (3)adjustment of the setting of the ventilator are all difficult to handle clinically. This experimental complexity renders the hydraulic method less simple to use than
the acoustic reflection method. In addition, long-term monitoring might be compromised with the hydraulic method since fresh mucus may obstruct the side holes of the pressure catheter. By contrast, the acoustic reflection method provides a means for short- or long-term routine monitoring of the gradual reductions in ETT patency as well as for the determination of sites of mucus accumulation. However, it is difficult from the present results to ascertain the minimum value of ETT area acceptable in ventilated patients. Further studies are needed to determine, from the
acoustic area monitoring, a reliable criterion to be used as and alarm for ETT replacement. The results obtained here suggest the this new method provides a means for reducing the risk of unnecessary extubation and associated morbidity, as well as an aid to estimate the increase in the work of breathing caused by ETT obstruction.