Effects of fiberoptic bronchoscopy on pulmonary pressures and ventilation in ARDS: a bench evaluation
CCCF ePoster library. Chassé M. Nov 2, 2016; 151009
Dr. Michaël Chassé
Dr. Michaël Chassé
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Topic: Basic or Translational Science

Effects of fiberoptic bronchoscopy on pulmonary pressures and ventilation in ARDS: a bench evaluation


Lemay, François1,2; Lefebvre, Jean-Claude1,2; Lellouche, François1,3; Bouchard, Pierre-Alexandre3; Delage, Antoine1,3; Chassé, Michaël1,2;
1Département d’anesthésiologie et de soins intensifs, Université Laval, Québec, Canada; 2CHU de Québec-Université Laval, Québec, Canada; 3Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
 



Abstract:

Introduction
Fiberoptic bronchoscopy (FOB) is commonly performed as a diagnostic and therapeutic procedure in intubated critically ill patients1-4. The presence of a bronchoscope through the endotracheal tube (ETT) invariably increases peak airway ventilation pressures, considered to be mainly caused by increased airway resistance5,6. Thus, obstruction of ETT by the bronchoscope may impact on pulmonary pressures and/or minute-ventilation, which may impair FOB’s safety. Knowledge is scarce regarding the impact of FOB on pulmonary pressures and ventilation in acute respiratory distress syndrome (ARDS)7,8, which are of great importance for ventilator associated injuries9,10.

Objectives
To evaluate the impact of FOB and maximal inspiratory pressure (Plimit) setting on pulmonary pressures and minute-ventilation in ARDS. Our hypothesis is that plateau pressures increase during FOB, secondary to dynamic hyperinflation through air trapping distally to the bronchoscope.  Our secondary objective is to determine which ventilation parameters best preserve pulmonary pressures while maintaining adequate minute ventilation.

Methods
Using a bronchoscope with external end diameter of 5.2 mm and a Michigan test-lung, we simulated 16 different conditions of an ARDS patient (pulmonary compliance of 20 mL/cm H2O, Rp5 resistance) ventilated with a lung protective strategy (tidal volume 420 mL, respiratory rate 30/min, positive end expiratory pressure (peep) 16 cm H2O, leading to a baseline plateau pressure of 28 cmH2O). Combinations of different ETT size (from 7.0 to 8.5 mm internal diameter), inspiratory flow 30 vs 60 L/min and Plimit 50 vs 100 cm H2O were studied. Plateau pressure, total peep and minute ventilation were obtained before and after insertion of the bronchoscope through the ETT for every combination.

Results
Plateau pressures variations ranged from -8 cm H2O (Plimit50, flow 30, ETT 7.0) to a maximum of +10 cm H2O (Plimit100, flow, ETT 7.5). A significant increase of more than 5 cm H2O of plateau pressures occurred exclusively when inspiratory flow was set at 30 L/min in ETT size 7.0 to 8.0. Plateau pressures increase correlated to peep variation. The highest augmentation of peep was of + 10 cm H2O in condition of Plimit 50 cm H2O, flow 30L/min, ETT size 7.5. FOB decreased minute ventilation in most conditions with Plimit set at 50 cm H2O. With Plimit 50 cm H2O, minute ventilation, as a percentage of baseline, ranged from 16 % (flow 60, ETT 7.0) to 103 % (flow 30, ETT 8.5). When Plimit was increased to 100 cm H2O, minute ventilation ranged from 54 % (flow 60, ETT 7.0) to 115 % (flow 60, ETT 8.0). Minute ventilation was under 80 % in all conditions where plateau pressure decreased during FOB.

Conclusion
Increasing inspiratory pressure limit allows for increased odds of reaching adequate minute ventilation, while impact on pulmonary pressure is limited when performing fiberoptic bronchoscopy on an ARDS lung model. In condition where resulting pulmonary pressures are increased, the augmentation of both total peep and plateau pressure suggests that this phenomenon could be secondary to dynamic hyperinflation. With a bronchoscope size of 5.2 mm external diameter, effects of FOB on minute ventilation and pulmonary pressure are more important in ETT of sizes 7.5 and lower.
 


References:

References

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2. Jolliet P, Chevrolet J. Bronchoscopy in the intensive care unit. Intensive Care Med. 1992;18:160-169.
3. Cracco C, Fartoukh M, Prodanovic H, et al. Safety of performing fiberoptic bronchoscopy in critically ill hypoxemic patients with acute respiratory failure. Intensive Care Med.          2013;39(1):45-52.       
4. Álvarez-maldonado P, Nunez-Perez Redondo C, Casillas-Enríquez JD, Navarro-Reynoso F, Cicero-Sabido R. Indications and Efficacy of Fiberoptic Bronchoscopy in the ICU : Have They Changed Since Its Introduction in Clinical Practice ? ISRN Endosc. 2013;2013:1-6.
5. Hsia D, DiBlasi RM, Richardson P, Crotwell D, Debley J, Carter E. The Effects of Flexible Bronchoscopy on Mechanical Ventilation in a Pediatric Lung Model. Chest. 2009;135(1):33-40.
6. Kuo AS, Philip JH, Edrich T. Airway Ventilation Pressures During Bronchoscopy, Bronchial Blocker, and Double-Lumen Endotracheal Tube Use - An In Vitro Study. J Cardiothorac Vasc Anesth. 2014;28(4):873-879.
7. Nay MA, Mankikian J, Auvet A, Dequin PF, Guillon A. The effect of fibreoptic bronchoscopy in acute respiratory distress syndrome: Experimental evidence from a lung model. Anaesthesia. 2016;71(2):185-191.
8. Lawson RW, Peters JI, Shelledy DC. Effects of fiberoptic bronchoscopy during mechanical ventilation in a lung model. Chest. 2000;118(3):824-831.
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10. Slutsky AS, Ranieri VM. Critical Care Medicine Ventilator-Induced Lung Injury. N Engl J Med. 2013;22369(28):2126-2136.



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