Permanent tracheostomy for long-term respiratory studies

Abstract

Background: We describe a modified surgical technique for permanent, anterior tracheal-wall stoma for chronic, repeat respiratory studies in trained, conscious dogs. These cannula-free tracheostomies require minimal daily maintenance, permit repeat intubation with endotracheal tubes modified for airflow respiratory measurement, and facilitate up to 6 h continuous administration of aerosol agents during long-term or repeat respiratory studies.

Methods: In 20 dogs, during a 30 to 40 min procedure, portions of tracheal rings 2-4 were removed to create an oval stoma, approximately 2 x 1 cm. The dermis was secured to the transected cartilage and tracheal mucosa in such a manner that skin covered the sternohyoid muscles and grew-in flush with the tracheal mucosa at the stomal opening. Stomas were cleaned daily, and fur was clipped weekly around the stomal site. No other maintenance procedures or environmental modifications were needed. Animals breathed through both the stoma and the upper airway and barked normally.

Results: Stomas remained viable in long-term animals (n = 4) ongoing for 70.3 +/- 32.2 mo (mean +/- SEM), with an ongoing maximum of 126 mo. Postmortem examinations were performed on shorter-term animals (n = 16) sacrificed at 16.7 +/- 7.3 mo. Thirteen showed no appreciable tracheal stenosis and three showed <10% stenosis at the level of the stoma. Histopathological examination of the stomal opening and surrounding tissue revealed minimal chronic inflammation and no evidence of necrosis or infection.

Conclusions: During long-term respiratory studies, this practical and dependable tracheal stoma provides a means for examining acute and chronic effects of environmental and pathophysiological influences on the respiratory system of conscious dogs.

Figure 1

A: A 6 cm incision is made parallel to the trachea on the anterior neck. B: The trachea is exposed and the sternohyoid muscles are sutured to the lateral tracheal wall. Blue X’s mark the location of sutures. C: Tracheal rings 2,3,4 are identified and marked with electro-cautery. D: Rings 2,3,4 are removed creating a rectangular stoma, 2 × 1 cm in the anterior wall of the trachea. E: A four-leafed clover shaped incision was formed by removing a 2 cm × 1 cm semicircle of skin from either side of the tracheal opening (Dotted Blue Line). F: The edges of the four-leafed clover shaped incision approximate to the edges of the stomal opening.

Figure 2

Final surgical result. Fourteen 3-0 Prolene stitches were used to suture the anterior neck skin (four-leafed clover incision) to the edges of exposed tracheal cartilage.

Figure 3

Example of respiratory data collected from intubated tracheal stoma.

Figure 4

Histopathology. A,B: The typical gross appearance of a cross-section at the stoma. A: The cross-section with fixation. B: A whole-mount large histological section showing the trachea, stoma, cutaneous mucosal junction, and the lateral muscle-trachea approximation. The boxes highlight areas illustrated at higher magnifications in the photomicrographs shown in C-F. C: The cutaneous-mucosal junction showing the transition from stratified squamous epithelium to respiratory mucosa. There is minimal chronic inflammation in both the subcutaneous tissue and the lamina propria of the trachea. Magnification 40X. D: The later tracheal wall. The respiratory mucosa has slight squamous metaplasia, but the lamina propria between the mucosa and cartilage has no pathological changes. Magnification 200X. E: The posterior tracheal wall opposite the stoma. Slight chronic inflammation is present in the lamina propria. This was the most severe chronic inflammation seen in any section of the trachea. The respiratory mucosa has no pathological changes. Magnification 200X. F: Lateral tracheal wall with squamous metaplasia, no chronic inflammation, and normal tracheal mucosal glands. There was neither an increase in tracheal mucosal gland thickness in the lamina propria, nor a pathological shift in the normal serous/mucous gland proportions. Magnification 200X.