Bench Evaluation of Oropharyngeal Packing to Reduce Leak During Rigid Bronchoscopy

Abstract

Background:

RB creates unique challenges for ventilation of the patient. While manual jet ventilation is the accepted standard, we have also used an LTV-1200 or a Respironics V60 ventilator. A common and recommended practice during RB is packing the oropharynx with gauze to reduce the leak and improve ventilation to the patient1. The purpose of this study was to perform a bench simulation of RB to evaluate if packing the oropharynx with gauze improves ventilation.

Methods:

We performed a bench study of RB with an intubation mannikin attached to the Ingmar ASL-5000 test lung with a Novametrix NM3-NICO flow sensor between the mannikin airway and the ASL-5000. Normal apneic adult settings were used on the ASL-5000. The manual jet was tested at 40 and 60 PSI with two breath types, "Burst" - short i-time and "Hold" - long i-time. The V60 was tested with I-Times of 0.6 s and 1 s, with a delta pressure of 20 cm H₂O and 30 cm H₂O. Two different leak scenarios were tested: "Low Leak" - typical setup of the RB with the silicon cap in place. "High Leak" - setup without silicon cap in place. All of the above variables were tested either with the mannikin's oropharynx packed with gauze as is typical during RB or not packed with gauze. Inspiratory tidal volumes were collected with each of the different scenario combinations with the NM3 device. Minitab 18 was used for statistical analysis.

Results:

See graphic for the results of the inspiratory volume delivered with various representative devices and settings with or without gauze packing or no gauze packing. Pearson correlation coefficient between both paired groups of tidal volumes (packed paired with unpacked) was 0.994 (P=0.000).

Conclusions:

Regardless of the ventilation device and settings used during RB, there is no difference in the tidal volume delivered if the oropharynx is packed with gauze or if it is not packed with gauze. The only values that differ with and without packing is during large tidal volumes of the manual jet, but the results are opposite of the purpose of packing. The tidal volume is greater without packing and may be associated with extra entrainment when packing is not present. The results of this study show that packing the oropharynx solely to maintain better ventilation is not necessary, packing does not improve ventilation during rigid bronchoscopy.

1. Ventilation and Anesthetic Approaches for Rigid Bronchoscopy. Ann Am Thorac Soc 2014;11(4):628-634.

Selected Manual Jet and V60 Tidal Volumes During Simulated Rigid Bronchoscopy: Oropharynx Packed with Gauze Versus Not Packed