ISSN 2398-2969      

Trachea: stricture

Clapis

Synonym(s): Tracheal stricture, tracheal stenosis


Introduction

  • Tracheal stenosis is the most commonly reported tracheal pathology in rabbits secondary to intubation trauma, but even this is uncommon.
  • Cause: mechanical abrasion, inflammation, focal edema, hemorrhage, erosion, ulceration, pressure necrosis with secondary stenosis.
  • Signs: usually arise 2-21 days post-intubation and include inspiratory dyspnea, respiratory wheezing, barking sounds, harsh lung sounds, dark pink to cyanotic (blue) mucous membranes, neck hyperextension associated with increased breathing effort, elbow abduction, nasal flaring, open mouth breathing, abdominal effort.
  • Diagnosis: history of recent endotracheal intubation (ETI), clinical signs, radiography, tracheoscopy, post-mortem, histopathology.
  • Treatment: medical treatment usually unrewarding.
  • Prognosis: poor.

Anatomy

  • Rabbits have a small and narrow oropharynx with reduced mandibular excursion, a relatively large and fleshy tongue and a small, steep and ventral laryngeal opening which makes ETI a relatively challenging task.
  • The epiglottis is normally engaged over the soft palate thus preventing access to the trachea via the oral cavity.
  • Hyperextension of the head facilities disengagement and ventral repositioning of the epiglottis allowing intubation.
  • The rabbit trachea courses caudally in a slightly open angle to the thoracic vertebrae and ends at the 4th intercostal space.
  • The rabbit trachea has a rich vascular sinus in the submucosa and mucosa with few glands.
  • Average airway size has been reported for New Zealand White rabbits New Zealand White, with a weight range of 2.3-5.1 kg, at the level of the cricoid cartilage (5.4-5.8 mm) and the 8th tracheal cartilage (4.7-5.9 mm).
  • The dimension of the subglottis is independent of weight, whereas the tracheal size at the 8th intercostal space varies significantly with weight.
  • Severe hyperemia of the trachea is a normal finding, however the deep red color does not involve the dorsal tracheal membrane and stops at the level of the carina.

Risk factors

  • Traumatic/prolonged intubation.
  • Incorrect intubation technique.
  • Use of a cuffed or un-cuffed endotracheal tube (ETT).
  • Infection.
  • Movement of the ETT.
  • Exposure to irritating substances.

Presenting signs

  • Usually arise 2-21 days post-intubation.
  • Inspiratory dyspnea Dyspnea.
  • Respiratory wheezing.
  • Barking sounds.
  • Harsh lungs sounds.
  • Mucous membranes are dark pink to cyanotic.
  • Neck hyperextension.
  • Elbow abduction.
  • Nasal flaring.
  • Opened mouth breathing.
  • Abdominal effort.

Acute presentation

  • Sudden onset of respiratory distress in an animal that is otherwise well normally suggests tracheal obstruction.
  • In mammals, dyspnea at rest is noticeable when the luminal compromise is severe and the tracheal diameter is reduced by 85-90%.

Species/breed predisposition

  • One report described the rabbit trachea as rich in vascular supply, suggesting the pressure and ischemia caused by a tracheal tube may hinder tracheal perfusion, contributing to the risk of mucosal damage and stenosis.
  • It is possible that this species may be more susceptible to any type of mucosal irritation. In one laboratory study, simple brushing of the mucosa led to stricture within 14 days with a narrowing of 43%.

Special risks

  • High risk anesthetic patients.
  • Ventilator compromise.
  • Complete occlusion of the airway by equipment.

Pathogenesis

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Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Jekl V (2021) Respiratory disorders in rabbits. Vet Clin Exot Anim 24 (2), 459-482 PubMed
  • Swisher S, Lennox A & Vecchio N (2020) Tracheal resection and anastomosis for treatment of tracheal collapse in a rabbit. J Exotic Pet Med 33, 46-49 VetMedResource.
  • Ferris R L, Quesenberry K E & Weisse C W (2019) Outcome of intraluminal tracheal stent placement for tracheal stenosis in a rabbit (Oryctolagus cuniculus). J Exot Pet Med 31, 23-27 VetMedResource.
  • Arellano-Orden E, Serrano C, Montes-Worboys A et al (2017) Stent-induced tracheal stenosis can be predicted by IL-8 expression in rabbits. Eur J Clin Invest 47 (1), 84-92 PubMed.
  • Luo X, Liu Y, Zhang Z et al (2013) Long-term functional reconstruction of segmental tracheal defect by pedicled tissue-engineered trachea in rabbits. Biomaterials 34 (13), 3336-3344 PubMed.
  • Steehler M K, Hesham H N, Wycherly B J et al (2011) Induction of tracheal stenosis in a rabbit model -endoscopic versus open technique. Laryngoscope 121 (3), 509-514 PubMed.
  • Crotaz I R (2010) Initial feasibility investigation of of the v-gel airway: an anatomically designed supraglottic airway device for use in companion animal veterinary anaesthesia. Vet Anaesthesia Analgesia 37 (6), 579-580 PubMed.
  • Nakagishi Y, Morimoto N, Fujita M et al (2009) Amelioration of airway stenosis in rabbit models by photodynamic therapy with talaporfin sodium (NPe6). Photochem Photobiol 85 (3), 714-718 PubMed.
  • Lennox A M & Capello V (2008) Tracheal intubation in exotic companion mammals. JEPM 17 (3), 221-227 VetMedResource.
  • Lee C H, Peng M J & Wu C L (2007) Dexamethasone to prevent postextubation airway obstruction in adults: a prospective, randomized, double-blind, placebo-controlled study. Critical Care 11 (4), R72 PubMed.
  • Culp W T, Weisse C, Cole S G et al (2007) Intraluminal tracheal stenting for treatment of tracheal narrowing in three cats. Vet Surg 36 (2), 107-113 PubMed.
  • Grint N J, Sayers I R, Cecchi R et al (2006) Postanaesthetic tracheal strictures in three rabbits. Lab Anim 40 (3), 301-308 PubMed.
  • Gubbels S P, Richardson M, Trune D et al (2006) Tracheal reconstruction with porcine small intestine submucosa in a rabbit model. Otolaryngology-Head Neck Surg 134 (6), 1028-1035 PubMed.
  • Phaneuf L R, Barker S, Groleau M A et al (2006) Tracheal injury after endotracheal intubation and anaesthesia in rabbits. J Am Assoc Lab Anim Sci 45 (6), 67-72 PubMed.
  • Dodge-Khatami A, Niessen H W, Baidoshvili A et al (2003) Topical vascular endothelial growth factor in rabbit tracheal surgery: comparative effect on healing using various reconstruction materials and intraluminal stents. European J Cardiothoracic Surg 23 (1), 6-14 PubMed.
  • Loewen M S & Walner D L (2001) Dimensions of rabbit subglottis and trachea. Lab Anim 35 (3), 253-256 PubMed.
  • Loewen M S, Walner D L & Caldarelli D D (2001) Improved airway healing using transforming growth factor beta-3 in a rabbit model. Wound Rep Regen (1), 44-49 PubMed.
  • Kil H K, Alberts M K, Liggitt H D et al (1997) Dexamethasone treatment does not ameliorate subglottic ischemic injury in rabbits. Chest 111 (5), 1356-1360 PubMed.
  • Nordin U & Lindholm C E (1977) The vessels of the rabbit trachea and ischemia caused by cuff pressure. Archives of Otorhinolaryngology 215 (1), 11-24 PubMed.
  • Nordin U, Lindholm C E & Wolgast M (1977) Blood flow in the rabbit tracheal mucosa under normal conditions and under the influence of tracheal intubation. Acta Anaesthesiologica Scandinavia 21 (2), 81-94 PubMed.
  • Conrardy P A, Goodman L R, Lainge F et al (1976) Alteration of endotracheal tube position. Flexion and extension of the neck. Crit Care Med (1), 8-12 PubMed.
  • Coon R A, Jones R A, Jenkins L J Jr. et al (1970) Animal inhalation studies on ammonia, ethylene glycol, formaldehyde, dimethylamine, and ethanol. Toxicol Appl Pharmacol 16 (3), 646-655 PubMed.

Other sources of information

  • Mancinelli E & Eatwell K (2013) Tracheal Stricture after Laparoscopic Ovariectomy in Two Domestic Rabbits. In: Proc 18th Int Vet Emerg & Crit Care Symposium. pp 190.
  • Eatwell K (2012) Use of a Supraglottic Airway Device to Maintain Gaseous Anaesthesia in Rabbits (Oryctolagus cuniculus). In: Proc 18th Int Vet Emerg & Crit Care Symposium. pp 737.
  • Vella D & Donnelly T M (2012) Basic Anatomy, Physiology and Husbandry. In: Ferrets, Rabbits and Rodents Clinical Medicine and Surgery. Eds: Quesenberry K E & Carpenter J W. 3rd edn. Elsevier. pp 157-173.

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