Tracheobronchial injury during intratracheal pulmonary ventilation in rabbits.
OBJECTIVE
We compared tracheobronchial injury following short-term intratracheal pulmonary ventilation (ITPV) and conventional mechanical ventilation (CMV) in a healthy rabbit model. ITPV, a form of tracheal gas insufflation, has been shown to decrease deadspace ventilation and increase CO2 removal and therefore may reduce ventilator-induced lung injury.


METHODS
Medical center laboratory.


METHODS
Twenty-five rabbits.


METHODS
Rabbits were randomly assigned to either ITPV or CMV (n = 15 and 10, respectively). Both groups were mechanically ventilated for 8 hrs at the same ventilator settings (FIO2, 0.4; rate, 30 breaths/min; flow, 4 L x min(-1); positive end-expiratory pressure, 4 cm H2O; tidal volume, 40 mL). Peak, mean, and end-expiratory carinal pressures, ITPV flow rate, and hemodynamic variables were continuously monitored. Tissue samples for histologic analysis were obtained postmortem from the trachea contiguous to the tip of the endotracheal tube, the distal trachea, the carina, and the main bronchus. The histologic sections were scored, in a single-blind fashion, for ciliary damage, ulceration, hemorrhage, overall inflammation, intraepithelial inflammatory infiltrate, and edema.


RESULTS
ITPV was associated with significantly lower Paco and deadspace ventilation ratio than CMV. The combined tracheobronchial injury scores for all samples were significantly higher in the ITPV group compared with the CMV group (p <.005; Mann-Whitney U test). The ITPV injury scores, compared with CMV injury scores, were significantly higher at the carina and main bronchus (p <.01; Kruskal-Wallis test followed by Dunn's multiple comparison test). The area adjacent to the endotracheal tube showed the same degree of damage in both groups. Analysis of the injury scores in individual damage categories demonstrated the greatest difference in the ulceration category (p <.001).


CONCLUSIONS
In our study, ITPV, compared with CMV at the same minute ventilation, was associated with a significantly greater difference in tracheobronchial damage at the carina and main bronchus. We postulate that this difference may have been caused by the turbulence of the gas flow generated by the small-caliber ITPV catheter used in our neonatal-size animal model.
Olarte
Jose Luis
JL
Division of Critical Care Medicine, Miami Children's Hospital, FL, USA.
Gelvez
Javier
J
Fakioglu
Harun
H
Torbati
Dan
D
Frazier
Kendall S
KS
Totapally
Balagangadhar R
BR
Raszynski
Andre
A
D000403:Airway Resistance; D000818:Animals; D001784:Blood Gas Analysis; D001980:Bronchi / Q000293:injuries*; D004195:Disease Models, Animal; D006439:Hemodynamics; D006813:Humidity; D007327:Insufflation / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D008297:Male; D010102:Oxygen Inhalation Therapy / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D011659:Pulmonary Gas Exchange; D011817:Rabbits; D011897:Random Allocation; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000295:instrumentation / Q000379:methods*; D012126:Respiratory Dead Space; D012307:Risk Factors; D016037:Single-Blind Method; D013314:Stress, Mechanical; D013990:Tidal Volume; D013997:Time Factors; D014132:Trachea / Q000293:injuries*