cuffed tube tracheostomy in the dog

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DOI: 10.1258/002367778781088495

1978 12: 203Lab Anim J. N. Leverment and S. RaeCuffed tube tracheostomy in the dog

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Laboratory Animals (I978) 12,203-206

Cuffed tube tracheostomy in the dog

J. N. LEVERMENT* & S. RAEThoracic Surgical Department. Medical Sciences Building, University of Toronto. Toronto, Canada

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SummaryA surgical technique of performing tracheostomy indogs requiring prolonged intubation with either cutTed or uncutTed tubes is described. Cannulae used inhumans are anatomically unsuitable for the dog. Thecannula and cutT described in this paper did not predispose to severe mechanical trauma to the tracheaand we attempted to minimize factors that may predispose to tracheal damage during the period of intubation and the subsequent development of latetracheal injuring after extubation.

A simple method of humidification in these healthydogs proved adequate; neither tenacious tracheobron-chial secretion nor the retention of secretions wereseen.

Nelson (1957), in reviewing the history of tracheo-stomy, mentions that it was once considered a 'scandalof surgery', a description which still may apply today because it is too often considered to be an easyoperation. However, if it is done without due care itcan lead to serious complications.

During a recent series of experimental studiesinvolving tracheostomized dogs for prolonged in-tubation with uncuffed and cuffed tubes, a surgicaltechnique w as evolved to circum vent som e of the diffi-culties commonly encountered. Modifications intracheostomy tube design were also made.

Materials and methodsTracheostomy tubes

Tracheostomy tubes designed for man areanatomically curved for man's trachea, but not for thedog's. A horizontal incision in the trachea (hereafter referred to as the 'stoma') often allows this curved cannula to tilt further anteriorly at its tip, or the curved part of the tube may inwardly buckle the superior margin of the stoma or damage the posterior trachealwall. Soft low-pressure cuffs attached to these tubesexpand asymmetrically on inflation, or are inefficientin centering the tube in the tracheal lumen.

An anatomically suitable tube can be moulded froma semi-rigid siliconized vinyl tube 10 cm long with

*

Present address: Cardiothoracic Surgery, Bristol RoyalInfirmary, Bristol, England.

Received 10 December 1976. Accepted 13 April 1978.

internal and external diameters of 7 and 9 mmrespectively. The section which lies outside the tracheais 3 cm long and the endotracheal section is 7 cm, thefirst 3 cm of which curves through an angle of 140 0 .The end of the tube is bevelled so that the tip is dorsalin the trachea. The endotracheal section is longenough to guard against displacement of the tube outof the trachea. The 3 cm length of the external sectionis sufficient to allow for the swelling and induration of the peri stomal tissues, and further guards againstdislodgement of the tube.

Fig. I. Modified tracheostomy cannula fitted with low-pressure culT.

A short adaptor can be fitted, but the length of tube projecting above the skin must be limited so thatrepeated contact is not made with the dog's lower jaw.Fig. I shows the tube fitted with a low-pressure high-residual-volume cuff.

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204 Leverment & Rae

Inc isionWhen the dog is supine with its head extended, asduring the trach eostomy procedure, the lax skin of theneck is drawn upwards in relation to the trachea. 2surface markings were therefore used (Fig. 2), point A

suture was used to check the movement cranially of the tube and prevent the destruction of intact trachealrings proximal to the incised rings. The snare wasconstructed with a silk suture (0) and a 3 cm length of vinyl tubing (Portex 800/010/250; Portex Ltd, Hythe,

Kent) as depicted in Fig. 4. The suture was subse-quently completed by looping it over the adaptor piece

Fig. 3. Incision with retractors showing incised tracheal rings posteriorly and 'traction' sutures anteriorly.

--A

--B

Surgical techniqueAnaesthesia was obtained using a single intravenousdose (20 mg/kg) of a 2% solution of sodium thio- pentone. Endotracheal intubation was not used. Thehair around the neck was cut short with an electricclipper, but only the skin overlying the trachea wherethe incision was to be made was cleanly shaved with ascalpel. Strict asepsis with proper preparation and surgical technique was used.

flig. 2. Surface markings on dog for tracheostomy skin incision.

being the midline between the cricoid cartilage and suprasternal notch with the neck in the normal 'awake'semiflexed position, and point B being the midline between the cricoid and the suprasternal notch withthe dog anaesthetized and the neck extended. These

points were marked witll a pencil line and a verticalincision made between them. The cervical strapmuscles were split on the midline and retracted laterally to expose the trachea.

The stoma was fashioned by a vertical slit involvingthe 3 tracheal cartilages exposed at the lower end of the wound (Fig. 3). Two long 'traction' silk or nylonsutures (000) were placed at the upper end of the skinincision; each suture first passing through the skin and subcutaneous tissue, then through the proximal and distal incised tracheal rings, and finally back againthrough the subcutaneous tissue and skin.

It is difficult to prevent excessive movement of the

tracheostomy tube in a playful and restless animalsuch as the dog. In addition, rapid up and downexcursions of the trachea and oesophagus occur during deglutition and attempts at barking. A 'snare'

".

I '.)~

I I !Fig.4. Tracheostomy with 'traction' and 'snare' sutures.



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Tracheostomy in the dog

when the animal had fully recovered from theanaesthetic. By sliding the vinyl tubing up or down,tension in the suture could be adjusted.

The tracheostomy tube was kept in place withcotton tapes tied around the neck. The pilot tube and mechanical valve of the tracheostomy tube weresutured onto the cotton tapes out of reach of theinquisitive tongue of the dog. Broad cotton tapes werefound to cause less chafing to the animal's neck than broad rubber strips. Suturing of the neck plate of thetracheostomy tube directly to the skin proved anunreliable method of preventing displacement of thetube. In addition, unnecessary skin sepsis can resultfrom these sutures being as they are, so near thetracheostomy wound.

A thin short elastic band with metal paper clips ateach end can be used to approximate the 'traction'sutures behind the animal's neck, keeping these suturesout of reach of the ever-exploring tongue of the dog.After only a short period of intubation, healing of thetracheostomy wound by primary intention can beenhanced by crossing these sutures and similarlyapproximating them behind.

With the dog in the normal standing position, thestoma and tracheostomy tube come to lie opposite the'traction' sutures, which facilitated introduction of thetube and subsequently simplified the process of cleaning and changing the tubes. In addition, nounsightly redundant cervical skin folds appeared above the tracheostomy with the tubes in situ (Pig. 5).

\

Fig. 5. Traeheoslomy assembly in situ.

The lower end of the tracheostomy incision mustnot be sutured, but should be left open to allow freedrainage of secretions, otherwise severe peristomalinfection or abscess formation is likely to occur. After

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4-5 days this part of the tracheostomy heals by

primary intention, leaving a neat stoma just slightly bigger than the cannula of the tracheostomy tube. Atthis stage the process of changing the tubes becomessimple and the 'traction' sutures can be removed. Inner cannulae prevent unnecessary trauma which mayresult from repeated reinsertions of cuffed tracheo-stomy tubes.

Antibiotic cover should be given for the first 5 days postoperatively, and analgesics as required.

HumidificationThere are practical difficulties in obtaining prolonged optimal humidification in such an active animal as the

dog. Modelle, Giammona & Davis (1967) exposed puppies to ultrasonic aerosols of normal salinesolution or distilled water for 72 h and found patho-logical changes in the lungs. However, Noguchi(1972) claimed that lung function in tracheostomiz~dogs can be conditioned best with air of 100% relativehumidity saturation at 25-30C for 24 h. We used asimple method of providing humidification for tracheo-stomized dogs continuously intubated with cuffed tracheostomy tubes for 14 days. The dogs were caged separately under a transparent canopy in a large air-conditioned room. Humidity was provided as tapwater vapour mist to each cage by a commercial

humidifier (Sovereign model 707S/M; Water RefiningCo. Ltd, 475 Edward Street, Richmond Hill, Ontario,Canada). The humidified environment was maintained at 100% relative humidity at 22-24C, with theoxygen concentration 20% and carbon dioxide con-centration negligible.

The animals were set free from their cages twicedaily for 30 min while the tracheostomies wereinspected and the cages cleaned. Drinking water and food were supplied ad libitum.

Tracheobronchial secretions were serosanguinous innature over the first 4-5 days after tracheostomy and intubation, but became markedly decreased and lessviscous afterwards. At no stage was endobronchialsuction used.

All the dogs remained clinically healthy and apparently happy during the 2 weeks of intubation.Their body weights remained steady. Chest radio-graphs showed no evidence of bronchopneumonicchanges.

3 bronchoscopic examinations were done duringintubation. Throughout this period, only superficial patchy areas of damage to the trachea were seen at thecuff site. No residual damage was noticed en-doscopically 2 weeks after removal of the cuffed tubes.

The stomas healed by primary intention within the 1stweek after removal of the tube. Permanent puckeringof the skin around the tracheostomy site was notevident. No post-intubation tracheal stenosesdeveloped.



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DiscussionRichards & Glenn (1932) and Watts (1963) presented

experimental evidence that cartilage does not regener-ate, and that healing occurs by fibrous tissue. Largecartilage defects at the stomal site after tracheostomycan result from surgical removal of too large a piece of cartilage, pressure necrosis of the cartilage by usingtubes with large external diameters, or excessivemovement of these tubes. Infection which invariablyfollows tracheostomy and intubation also impairs theviability of the cartilage at the margin of the stoma.Such large defects may subsequently result in theformation of functionally significant tracheal stenosesat stomal level (Andrews, 1971).

Damage to the tracheal wall at cuff level was

reportedly due to pressure necrosis by the cuff; non-yielding low-residual volume cuffs caused extensiveearly and late damage to the trachea at cuff site(Goldberg & Pearson, 1972). The superiority of

References

Andrews, H. J. (1971). The incidence and pathogenesis of tracheal injury following tracheostomy with cuffed tubeand assisted ventilation. Analysis of a 3 year prospectivestudy. British Journal of Surgery 58, 749-755.

Goldberg, M. & Pearson, F. G. (1972). Pathogenesis of

tracheal stenosis following tracheostomy with a culTed tube: an experimental study in dogs. Thorax 27.678-691.

Grillo, H. C., Cooper, J. D., Geffin, B. & Pontoppidan, H.(1971). A low-pressure culT for tracheostomy tubes tominimize tracheal injury. Journal of Thoracic and Cardiovascular Surgery 62, 898-907.

Leverment, J. N., Pearson, F. G. & Rae, S. (1975). Trachealsize following tracheostomy and culTed-tube intubation:an experimental study in dogs. Thorax 30, 271-277.

Leverment & Rae

recently-designed low-pressure cuffs over those pre-viously used is now clinically and experimentally well

established (Grillo, Cooper, Geffin & Pontoppidan,1971; Leverment, Pearson & Rae, 1975). Themajority of experimental studies to investigate factors

predisposing to tracheal injury have been carried outin dogs. Investigators should bear in mind that faultytechnique in itself will cause severe tracheal damage,and this can be minimized by suitably modifying thesurgical procedure and the tracheostomy devices.

AcknowledgementsWe wish to thank Miss C. Allen, secretary to ThoracicSurgical Department, Frenchay Hospital, Bristol for

secretarial assistance. Our sincere thanks are due toProfessor F. G. Pearson, Head of Thoracic Surgery,University of Toronto, Canada, for his extremelyhelpful suggestions and support.

Modelle, H. J., Giammona, S. T. & Davis, J. H. (1967).Effect of chronic exposure of ultrasonic aerosols on thelung. Anesthesiology 28,680-688.

Nelson, T. G. (1957). Tracheotomy: a clinical and experimental study. Part Ill. American Surgeon 22, 841-

881. Noguchi, H. (1972). Studies on proper humidification in

tracheostomised dogs. Nagoya Medical Journal 17, 159-178.

Richards, L. & Glenn, F. (1932). The histopathologicreaction of the tracheotomic wound. Archives of Otolaryngology 15,389-412.

Watts, J. McK. (1963). Tracheostomy in modern practice. British Journal of Surgery s o , 954-975.


cuffed tube tracheostomy in the dog

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