Morphological findings in the tracheal epithelium of dogs exposed to the inhalation of poorly conditioned gases under use of an endotracheal tube or laryngeal mask airway

Norimar Hernandes Dias,Regina Helena Garcia Martins,Lídia Raquel Carvalho,José Reinaldo Cerqueira Braz,Júlio Defaveri

doi:10.1590/s0102-86502011000500006

Abstract

To study morphological findings in the tracheal epithelium of dogs exposed to the inhalation of poorly conditioned gases under use of an endotracheal tube (ET) or laryngeal mask airway (LMA). Twelve dogs randomly were allocated to two groups: ET group (n-6) and LMA group (n-6), anaesthetized and mechanically ventilated, without CO(2) reabsorption. Haemodynamic and ventilatory parameters, tympanic temperature, temperature, relative and absolute humidity of the ambient and inhaled gases were analyzed during three hours. The animals were submitted to euthanasia and biopsies were carried out along the tracheal segment to morphological study. Three healthy dogs were used to morphological control. Inhaled gas temperature was maintained between 24ºC and 26ºC, relative humidity between 10% and 12%, and absolute humidity between 2 - 3 mg H(2)O.L(-1) with no significant differences between groups. In both groups, histological analysis showed epithelial inflammation and congestion in the corion and scanning electron microscopy showed ciliary grouping and disorganization. Transmission electron microscopy showed higher alterations in ET group than LMA group as widening of cell junctions, ciliary disorientation, cytoplasmic vacuolization, nuclear abnormalities, picnosis and chromatin condensation. LMA determined less pronounced changes in the tracheal epithelium in dogs exposed to the inhalation of poorly conditioned gases.

Highlights

During respiration, inspired air gains approximately 75% of heat and humidity as it passes through the nose and rhinopharynx, due to the high vascularization and a large contact surface[1]
In order to complement our previous investigation, this study aimed at describing the morphological particularities of the tracheal epithelium in dogs exposed to the inhalation of gases with low temperature and humidity to confirm the advantages of using a laryngeal mask airway (LMA) in relation to endotracheal tube (ET)
The animals were randomly allocated into the two following groups, according to the method used for airway maintenance: ET group, using ET Portex no 8.5 (England) and LMA group (Laryngeal Mask Airway; n - 6), using LMA Classic TM no 4 (Singapore)

Summary

Introduction

During respiration, inspired air gains approximately 75% of heat and humidity as it passes through the nose and rhinopharynx, due to the high vascularization and a large contact surface[1]. In the remainder airway segments (pharynx, larynx, trachea and bronchi), the conditioning process is completed. Tracheotomy, intubation or laryngectomy are conditions that the passage of inspired air through the nasal cavities is impaired requiring high participation of remaining airway segments in the humidity and heat exchanges[2]. Experimental researches have reported respiratory epithelial injuries of varying degrees in consequence of the inhalation of cold and dry gases as decreased mucociliary clearance; increased mucus viscosity and dryness; ciliary disorganization, grouping or devastation; mucosa erosion, ulceration and necrosis; inflammation and even metaplasia of the tracheal epithelium in chronic processes[3,4,5]

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