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Permanent Tracheostomy for Long-Term Respiratory Studies
Abstract
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.
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.
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.
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.
... The blood pressure catheter was tunneled subcutaneously to the inguinal region and implanted 4-6 cm, oriented upstream in the femoral artery using a technique similar to our previously described method (Bartoli et al. 2006). We created a permanent tracheostomy to facilitate exposure, as previously described (Bartoli et al. 2008;Godleski et al. 2000). Breathing via tracheostomy has minimal effects on airway mechanics (Drazen et al. 1982). ...
... Third, upper-airway receptors in the nostrils, nasopharynx, and trachea may participate in respiratory and cardio vascular responses. In our canine model, inhalation exposure to CAPs occurs via a permanent tracheostomy (Bartoli et al. 2008), which bypasses the nasopharynx and may exclude important pathophysiologic pathways, especially in canines, which rely heavily on olfactory senses. Fourth, we performed this study in healthy, female dogs. ...
Epidemiologic studies suggest a positive association between fine particulate matter and arterial blood pressure, but the results have been inconsistent.
We investigated the effect of ambient particles on systemic hemodynamics during a 5-hr exposure to concentrated ambient air particles (CAPs) or filtered air (FA) in conscious canines.
Thirteen dogs were repeatedly exposed via permanent tracheostomy to CAPs (358.1+/-306.7 microg/m3, mean+/-SD) or FA in a crossover protocol (55 CAPs days, 63 FA days). Femoral artery blood pressure was monitored continuously via implanted telemetry devices. We measured baroreceptor reflex sensitivity before and after exposure in a subset of these experiments (n=10 dogs, 19 CAPs days, 20 FA days). In additional experiments, we administered alpha-adrenergic blockade before exposure (n=8 dogs, 16 CAPs days, 15 FA days). Blood pressure, heart rate, rate-pressure product, and baroreceptor reflex sensitivity responses were compared using linear mixed-effects models.
CAPs exposure increased systolic blood pressure (2.7+/-1.0 mmHg, p=0.006), diastolic blood pressure (4.1+/-0.8 mmHg; p<0.001), mean arterial pressure (3.7+/-0.8 mmHg; p<0.001), heart rate (1.6+/-0.5 bpm; p<0.001), and rate-pressure product (539+/-110 bpm x mmHg; p<0.001), and decreased pulse pressure (-1.7+/-0.7 mmHg, p=0.02). These changes were accompanied by a 20+/-6 msec/mmHg (p=0.005) increase in baroreceptor reflex sensitivity after CAPs versus FA. After alpha-adrenergic blockade, responses to CAPs and FA no longer differed significantly.
Controlled exposure to ambient particles elevates arterial blood pressure. Increased peripheral vascular resistance may mediate these changes, whereas increased baroreceptor reflex sensitivity may compensate for particle-induced alterations in blood pressure.
... The air pressures in the breathing tubes and in the chamber are closely monitored and balanced so that the animals never breathe against any pressure gradient. The tracheostomy procedure and this exposure system have been described by Godleski et al. (2000) as well as by Clarke et al. (2000B) and Wellenius et al. (2003) and further evaluated by Bartoli et al. (2008). In order to correlate the observed cardiac, pulmonary, inflammatory, and neurologic responses to specific components of particulate matter, CAPs are continuously measured during each exposure. ...
Epidemiologic studies indicate an association between airborne particulate matter and cardiovascular morbidity and mortality.
However, the underlying pathophysiologic mechanisms require further investigation. This review examines insights derived from
large animal inhalation studies on systemic and coronary hemodynamic function and susceptibility to cardiac arrhythmias. We
present evidence of acute cardiovascular alterations in chronically instrumented or anesthetized large animals exposed to
concentrated ambient particles. Significant changes were observed in a number of clinically relevant variables. These included
elevations in arterial blood pressure and reductions in myocardial perfusion during coronary occlusion that resulted in the
exacerbation of ischemic parameters, such as ST-segment elevation and vasoconstriction. The involvement of sympathetic nerve
activity was implicated by the fact that alpha-adrenergic blockade with prazosin significantly blunted the vasoconstrictor
effects. Alterations in baroreceptor function during air particulate exposure were also substantial. Enhanced susceptibility
to both atrial and ventricular arrhythmias was demonstrated. These studies with clinically relevant large animal models underscore
the importance of the role of air particulate pollution in inducing adverse effects on cardiovascular function and warrant
further exploration of specific components of air pollution as well as the physiologic triggers that lead to cardiovascular
events. New clinically applicable research tools have evolved, particularly heart rate turbulence, a noninvasive measure of
baroreceptor function, and T-wave alternans, an index of susceptibility to life-threatening arrhythmias, which can be employed
clinically to evaluate the impact of air pollution on cardiovascular risk.
KeywordsMyocardial ischemia–Myocardial infarction–Sudden cardiac death–Atrial fibrillation–Cardiac arrhythmias–Hypertension–Autonomic nervous system
... In four animals, a radio telemetry unit (D70-CCTP; Data Sciences International, St. Paul, MN, USA) capable of measuring femoral arterial blood pressure and electrocardiogram was implanted in the left flank. In all animals, a permanent tracheostomy was surgically created to facilitate inhalation exposure (Bartoli et al. 2008a). After surgery, animals recovered for a minimum of 3 weeks before participating in experiments. ...
Experimental and observational studies have demonstrated that short-term exposure to ambient particulate matter (PM) exacerbates myocardial ischemia.
We conducted this study to investigate the effects of concentrated ambient particles (CAPs) on myocardial blood flow during myocardial ischemia in chronically instrumented conscious canines.
Eleven canines were instrumented with a balloon occluder around the left anterior descending coronary artery and catheters for determination of myocardial blood flow using fluorescent microspheres. Telemetric electrocardiographic and blood pressure monitoring was available for four of these animals. After recovery, we exposed animals by inhalation to 5 hr of either filtered air or CAPs (mean concentration+/-SD, 349.0+/-282.6 microg/m3) in a crossover protocol. We determined myocardial blood flow during a 5-min coronary artery occlusion immediately after each exposure. Data were analyzed using mixed models for repeated measures. The primary analysis was based on four canines that completed the protocol.
CAPs exposure decreased total myocardial blood flow during coronary artery occlusion by 0.12 mL/min/g (p<0.001) and was accompanied by a 13% (p<0.001) increase in coronary vascular resistance. Rate-pressure product, an index of myocardial oxygen demand, did not differ by exposure (p=0.90). CAPs effects on myocardial blood flow were significantly more pronounced in myocardium within or near the ischemic zone versus more remote myocardium (p interaction<0.001).
These results suggest that PM exacerbates myocardial ischemia by increased coronary vascular resistance and decreased myocardial perfusion. Further studies are needed to elucidate the mechanism of these effects.
Mechanical stresses on the lung impose the major stimuli for developmental and compensatory lung growth and remodeling. We used computed tomography (CT) to noninvasively characterize the factors influencing lobar mechanical deformation in relation to posture, pneumonectomy (PNX), and exogenous pro-angiogenic factor supplementation. Post-PNX adult canines received weekly inhalations of nebulized nanoparticles loaded with recombinant human erythropoietin (EPO) or control (empty nanoparticles) for 16 weeks. Supine and prone CT were performed at two transpulmonary pressures pre- and post-PNX following treatment. Lobar air and tissue volumes, fractional tissue volume (FTV), specific compliance (Cs), mechanical strains and shear distortion were quantified. From supine to prone, lobar volume and Cs increased while strain and shear magnitudes generally decreased. From pre- to post-PNX, air volume increased less and FTV and Cs increased more in the left caudal (LCa) than in other lobes. FTV increased most in the dependent subpleural regions and the portion of LCa lobe expand laterally wrapping around the mediastinum. Supine deformation was non-uniform pre- and post-PNX; strains and shear were most pronounced in LCa lobe and declined when prone. Despite non-uniform regional expansion and deformation, post-PNX lobar mechanics were well preserved compared to pre-PNX owing to robust lung growth and remodeling towards establishing a new mechanical equilibrium. EPO treatment eliminated posture-dependent changes in FTV, accentuated the post-PNX increase in FTV and reduced FTV heterogeneity without altering absolute air or tissue volumes, consistent with improved microvascular blood volume distribution and modestly enhanced post-PNX alveolar microvascular reserves.
Paracrine erythropoietin (EPO) signaling in the lung recruits endothelial progenitor cells, promotes cell maturation and angiogenesis , and is upregulated during canine post-pneumonectomy (PNX) compensatory lung growth. To determine whether inhalational delivery of exogenous EPO augments endogenous post-PNX lung growth, adult canines underwent right PNX and received, via a permanent tracheal stoma, weekly nebulization of recombinant human EPO-containing nanoparticles or empty nanoparticles (control) for 16 weeks. Lung function was assessed under anesthesia pre- and post-PNX. The remaining lobes were fixed for detailed morphometric analysis. Compared to control treatment, EPO delivery significantly increased serum EPO concentration without altering systemic hematocrit or hemoglobin concentration, and abrogated post-PNX lipid oxidative stress damage. EPO delivery modestly increased post-PNX volume densities of the alveolar septum per unit of lung volume and type II epithelium and endothelium per unit of septal tissue volume in selected lobes. EPO delivery also augmented the post-PNX increase in alveolar double-capillary profiles, a marker of intussusceptive capillary formation, in all remaining lobes. EPO treatment did not significantly alter absolute resting lung volumes, lung and membrane diffusing capacities, alveolar-capillary blood volume, pulmonary blood flow, lung compliance, or extravascular alveolar tissue volumes or surface areas. Results established the feasibility of chronic inhalational delivery of growth-modifying biologics in a large animal model. Exogenous EPO selectively enhanced cytoprotection and alveolar angiogenesis in remaining lobes but not whole-lung extravascular tissue growth or resting function; the unbalanced response contributes to structure-function discrepancy, a major challenge for interventions aimed at amplifying the innate potential for compensatory lung growth.
Chronic ventilatory support may be required for survival after total artificial heart (TAH) implantation in calves. However, prolonged or repeated intubation may negatively affect a calf's ability to eat, drink, ruminate, and stand after surgery. To mitigate these limitations, we performed tracheotomies on 23 consecutive calves at the time of TAH implantation. The tracheostomies served as the primary route for ventilatory support and airway management. Tracheostomies were left in place for up to 25 days (mean, 7 +/- 7 days) and were well tolerated. Prolonged presence of a tracheostomy facilitated cleaning of the airway secretions and did not inhibit the calf's ability to stand, eat, or drink. The calves survived from 2 to 49 days (mean, 8 days). Twenty-two calves that maintained their tracheostomies died of causes unrelated to airway management. The calf that had the tracheostomy removed on day 25 died of respiratory arrest on day 49. At necropsy, we found that severe tracheal stenosis had developed at the tracheostomy site. In calves, an elective tracheotomy can be a valuable adjunct to TAH implantation or other procedures that might require prolonged ventilatory support or airway access, but care should be exercised if the tracheostomy is removed to ensure that the calf does not develop late tracheal stenosis.
Pulmonary inflammatory and hematologic responses of canines were studied after exposure to concentrated ambient particles (CAPs) using the Harvard ambient particle concentrator (HAPC). For pulmonary inflammatory studies, normal dogs were exposed in pairs to either CAPs or filtered air (paired studies) for 6 hr/day on 3 consecutive days. For hematologic studies, dogs were exposed for 6 hr/day for 3 consecutive days with one receiving CAPs while the other was simultaneously exposed to filtered air; crossover of exposure took place the following week (crossover studies). Physicochemical characterization of CAPs exposure samples included measurements of particle mass, size distribution, and composition. No statistical differences in biologic responses were found when all CAPs and all sham exposures were compared. However, the variability in biologic response was considerably higher with CAPs exposure. Subsequent exploratory graphical analyses and mixed linear regression analyses suggested associations between CAPs constituents and biologic responses. Factor analysis was applied to the compositional data from paired and crossover experiments to determine elements consistently associated with each other in CAPs samples. In paired experiments, four factors were identified; in crossover studies, a total of six factors were observed. Bronchoalveolar lavage (BAL) and hematologic data were regressed on the factor scores. Increased BAL neutrophil percentage, total peripheral white blood cell (WBC) counts, circulating neutrophils, and circulating lymphocytes were associated with increases in the aluminum/silicon factor. Increased circulating neutrophils and increased BAL macrophages were associated with the vanadium/nickel factor. Increased BAL neutrophils were associated with the bromine/lead factor when only the compositional data from the third day of CAPs exposure were used. Significant decreases in red blood cell counts and hemoglobin levels were correlated with the sulfur factor. BAL or hematologic parameters were not associated with increases in total CAPs mass concentration. These data suggest that CAPs inhalation is associated with subtle alterations in pulmonary and systemic cell profiles, and specific components of CAPs may be responsible for these biologic responses.
Short-term increases in ambient air pollution have been associated with an increased incidence of acute cardiac events. We assessed the effect of inhalation exposure to concentrated ambient particles (CAPs) on myocardial ischemia in a canine model of coronary artery occlusion. Six mongrel dogs underwent thoracotomy for implantation of a vascular occluder around the left anterior descending coronary artery and tracheostomy to facilitate particulate exposure. After recovery (5-13 weeks), pairs of subjects were exposed for 6 hr/day on 3 or 4 consecutive days. Within each pair, one subject was randomly assigned to breathe CAPs on the second exposure day and filtered air at other times. The second subject breathed CAPs on the third exposure day and filtered air at other times. Immediately after each exposure, subjects underwent 5-min coronary artery occlusion. We determined ST-segment elevation, a measure of myocardial ischemia heart rate, and arrhythmia incidence during occlusion from continuous electrocardiograms. Exposure to CAPs (median, 285.7; range, 161.3-957.3 microg/m3) significantly (p = 0.007) enhanced occlusion-induced peak ST-segment elevation in precordial leads V4 (9.4 +/- 1.7 vs. 6.2 +/- 0.9 mm, CAPs vs. filtered air, respectively) and V5 (9.2 +/- 1.3 vs. 7.5 +/- 0.9 mm). ST-segment elevation was significantly correlated with the silicon concentration of the particles and other crustal elements possibly associated with urban street dust (p = 0.003 for Si). No associations were found with CAPs mass or number concentrations. Heart rate was not affected by CAPs exposure. These results suggest that exacerbation of myocardial ischemia during coronary artery occlusion may be an important mechanism of environmentally related acute cardiac events.
Trachea-innominate artery fistula is an uncommon but frequently fatal complication of tracheostomy. Three successive patients who developed this complication while receiving ventilatory assistance through a tracheostomy tube were successfully managed, with long-term survival. Bleeding was controlled by direct digital pressure on the innominate artery or by hyperinflation of the balloon cuff of the tracheostomy tube. In 2 patients, replacement of the tracheostomy tube with an orotracheal tube improved direct access to the innominate artery for digital compression. Late follow-up examination of the right carotid circulation revealed complete reversal of flow in the right internal and common carotid arteries in the 2 patients studied.
The flap tracheostomy was studied in 25 adult canines to further investigate its best management. Tracheostomies were performed by employing the inverted U flap incision in the trachea. After decannulation, the flap was either formally resewn to the trachea, bluntly dissected from the surrounding soft tissues, or left in place. The time required for epidermal closure over the tracheostomy site was measured, along with fixation of skin to soft tissues in the area. Histologic examinations were made, and tracheal dimensions were calculated on sections through the stomal area. More rapid skin closure and less soft tissue fixation occurred in animals that underwent resuturing or release of the tracheal flap. In all groups, cartilage viability and regrowth were noted. Tracheal diameters were maintained in all groups, but smoother contouring was seen with resuturing. Additional support for the flap tracheostomy is provided from this animal experimentation.
A surgical procedure to produce a permanent tracheostomy in dogs was developed. The procedure consisted of dissecting portions of the cartilaginous rings free from the underlying tracheal mucosa, cutting through the mucosa and suturing the mucosa to the skin. The procedure was performed in approximately 30 minutes and resulted in a permanent, maintenance-free, mucocutaneous stoma that also permitted breathing through the upper respiratory airways.
The effect of the inhalation of dried (less than 40% water-saturation) or humidified air (100% water-saturation at 25, 30, 35 and 40 degrees C) was studied in dogs in which a tracheostomy had been performed to determine the optimal humidity. After inhalation for various periods, the dogs were killed and pieces of lung tissue were excised for analysis of surfactant. Sections of the trachea and the primary to tertiary bronchi were taken for scanning electron microscopic examination. Structural changes were observed in the trachea of dogs inhaling dried at and in the tertiary bronchi of dogs inhaling 100% water-saturated air at 35 degrees C. No changes was observed after 24 h in dogs which had inhaled 100% water-saturated air at 25 degrees C under anaesthesia or at 30 degrees C without anaesthesia. Consequently, the optimal range of humidity was determined to be 100% water-saturation between 25 and 30 degrees C.
Three standard tracheostomy incisions in dogs were compared to determine whether any were more likely associated with stomal stenosis. Each incision resulted in an average reduction in tracheal lumen of 25 per cent, with a 50 per cent maximum. The incision selected should depend on the conditions present.
A surgical technique of performing tracheostomy in dogs requiring prolonged intubation with either cuffed or uncuffed tubes is described. Cannulae used in humans are anatomically unsuitable for the dog. The cannula and cuff described in this paper did not predispose to severe mechanical trauma to the trachea and we attempted to minimize factors that may predispose to tracheal damage during the period of intubation and the subsequent development of late tracheal injuring after extubation.
A simple method of humidification in these healthy dogs proved adequate; neither tenacious tracheobronchial secretion nor the retention of secretions were seen.
Respiration through an endotracheal tube often provides very adequate ventilation for infants and children with respiratory distress. Nevertheless, there are pediatric patients for whom tracheostomy is indicated.A technical point of contention concerns the tracheal incision. Excision of tracheal tissue or multiple incisions, which meet or cross have been abandoned in the pediatric age group. The choice today is a vertical incision dividing several cartilages1–3 versus a transverse incision between tracheal rings.4,5 This experiment was designed to compare the effect of longitudinal and transverse incisions on tracheal growth and development in the immature growing animal.
Tracheostomies were performed on 25 mongrel dogs, employing either a vertical or inverted U flap incision in the trachea. Following cannulation for 14 days, the animals were maintained for three months and endolarygeal photographs were taken. At the time of autopsy, comparisons of the gross specimens were carried out, as well as histological sectioning through the tracheal stomal area. Both endolaryngeal examination and study of the gross specimens at autopsy revealed less distortion of the tracheal lumen following the flap versus vertical tracheostomy, especially in those animals having the flap of cartilage resewn to the trachea at the time of decannulation. Measurements of the cross sectional area at the tracheal stoma were also made. In animals having a flap tracheostomy, the stomal lumen was preserved, regardless of resuturing the flap. However, animals having a vertical tracheostomy lost an average of 18% of the tracheal area when compared with those having a flap incision. Histological examination revealed cartilaginous growth across the tracheostomy incision only in animals having the flap tracheostomy. Support for the flap tracheostomy is provided from animal experimentation.
The dog is an animal widely used in experiments, and tracheostomy is frequently necessary when laryngeal experiments are carried out. Unfortunately, dogs generally do not tolerate tracheostomy well because the inserted cannula easily becomes displaced or blocked. This article presents a new surgical technique aimed at providing a long-term, dependable, and safe airway. It is based on previously established, clinically tested principles to avoid local tracheal complications. No essential tissue is removed or irreparably damaged and the procedure is reversible. Flexibility in management of the resultant stoma is possible, allowing either maintenance of maximal patency or gradual closure. Twenty-one animals were studied for 3- and 6-month periods, and there was no morbidity because of airway obstruction. This technique can reduce loss of valuable experimental animals caused by airway complications. It may also have application in human beings.
Experiments on dogs showed that the extent and number of rings damaged by the tracheostomy incision tube and tube motion seem to be the determining factor in the degree of narrowing which occurred at the stomal level. The scar tissue which formed in the area of the defect contracted and tended to convert the elliptically shaped tracheal lumen into a more triangular one, with resulting narrowing. If only one or 2 rings were damaged, adjacent rings limited narrowing. More severe stenosis resulted if 3 or more rings were injured. Thus, it seems that no tracheal cartilage should be excised in performing a tracheostomy, that as small a tracheostomy tube as possible should be utilized, and that all unnecessary tube motion and rotation from attached tubing should be prevented.
A study was undertaken to clarify the pathogenesis of tracheal stenosis complicating the use of cuffed tracheostomy tubes, a complication of increasing clinical significance.Tracheostomy with a cuffed inflated tube was established in dogs and was maintained for two weeks. The effects of tracheostomy were assessed by bronchoscopy, tracheography, and histology at the time of killing, eight weeks after extubation. Animals were divided into four groups, each mimicking a common clinical situation. A control group had uncuffed tubes. A method was designed to determine the pressure developed between the cuff and the tracheal wall. Cuff inflation was maintained at low pressure and at high pressure in a second and third group of animals. A fourth group of animals received prednisone during the two weeks of low pressure inflation.Tracheal stenosis, resembling the defect we have encountered in humans, occurred at the tracheostome in all animals. The greater the diameter of the tracheostomy tube relative to the tracheal diameter, the more severe was the resultant stenosis. Greater degrees of tracheal injury occurred with cuffed than with uncuffed tubes, and still greater injury was observed in animals in which high inflationary pressures or steroids were used.These findings suggest that tracheal stenosis complicating cuffed tracheostomy tubes is the result of ischaemic death of tracheal cartilage due to pressure and infection. Steroids used concomitantly accelerate these changes.
Observations are reported from a 3-year prospective study of tracheal injury occurring in patients managed by cuffed-tube tracheostomy and assisted ventilation in the Respiratory Failure Unit at Toronto General Hospital. When the cuffed tracheostomy tube was finally removed an initial bronchoscopic examination of the trachea was performed. Further clinical and radiological assessments were made 3 weeks and 3 months later, using bronchoscopy when indicated.
The incidence of symptomatic tracheal stenosis in 153 patients studied was 21 per cent. Of these strictures, 18 occurred at the level of the tracheostome and 14 at the level of the inflatable cuff. Disability due to airway obstruction was severe in 18 and mild in 14 patients. These mild lesions might easily have remained undetected. Two patients with severe strictures died of airway obstruction before treatment could be instituted, a mortality of 6·2 per cent in patients developing strictures. The remaining 30 strictures required treatment either by dialtation alone or by dilatation and resection of the stricture with tracheal reanastomosis. Two of the 153 patients studied developed chronic tracheo-oesophageal fistulas.
The observations indicate that stenosis can be anticipated before the lesion has developed by the finding of circumferential mucosal ulceration or segmental collapse at the initial per stomal bronchoscopy.
Observations from the study prompted the following changes in technique:-
The conclusions reached by this study were as follows:–
A tubeless tracheostomy technique has been developed for long-term canine laryngeal experimentation. Strict adherence to the guidelines set forth, and avoidance of pittalls discussed should allow an investigator to count on only 10% to 15% mortality from long-term tracheostomy in dogs. Furthermore, tracheostomy care for these animals should be minimized drastically. Canine research in this difficult area of the airway will hopefully be facilitated.
To facilitate continuous collection of exhaled air in conscious unmedicated dogs, a surgical technique of permanent tracheostomy was developed. Small portions of cartilagenous rings were dissected from the trachea creating a stoma approximately 0.5 x 2 cm. The tracheal mucosa and cut cartilage was secured to the dermis in such as manner that skin covered sternohyoid muscle covered the permanent tracheostomy when not in use. This allowed the dog to use its upper respiratory tract more effectively, preventing the frequent complication of tracheobronchitis and pneumonia. This procedure resulted in a maintenance-free stoma that did not require a high humidity environment or special care.
Chronic bronchitis was induced in 6 mongrel dogs by chronic exposure to SO2 gas; the degree of chronic airway obstruction and the effects on airway responsiveness to inhaled histamine, carbachol, and prostaglandin F2 alpha were examined. Five dogs developed chronic airway obstruction, as indicated by an increase in pulmonary resistance, and clinical mucous hypersecretion. In addition, in each of the animals in which chronic airway obstruction developed there was a decrease in the airway responsiveness to inhaled mediators. Those findings demonstrate that induction of chronic bronchitis in dogs results in hyporesponsiveness to inhaled mediators, a finding distinctly different from that reported in human subjects with naturally occurring disease.
The purpose of the study was to assess healing of horizontal and vertical tracheotomy after short-duration tracheostomy in dogs using clinical, radiographic, endoscopic, and histologic methods.
Horizontal tracheotomy (n = 6) between the third and fourth tracheal rings or vertical tracheotomy (n = 6) across tracheal rings three through five was performed for airway management during laryngoplasty. Tracheostomy tubes were maintained for 6 hours with low-pressure cuff inflation time limited to the first 1.5 hours. Cervical radiographs and tracheoscopy were performed preoperatively and at postoperative weeks 2, 4, 8, and 12. Ten of the 12 dogs were killed 12 weeks after tracheostomy.
There was no significant difference in preoperative and postoperative tracheal diameter or change in endoscopic tracheal circumference at the tracheostomy site when dogs were compared based on type of tracheotomy. Three dogs with horizontal tracheotomies had evidence of scar (web) within the tracheal lumen 12 weeks after surgery. All vertical tracheotomies had a mild, ventral, triangular deformity. Histologic examination of vertical tracheotomy sites showed complete restoration of the pseudostratified columnar epithelium. Horizontal tracheotomies healed with a single layer of columnar epithelium. Intraluminal scar was composed primarily of loose connective tissue.
Based on the results of this study, vertical tracheotomy shows more consistent healing compared with horizontal tracheotomy after short-duration tracheostomy. No evidence was found to support the preferential recommendation of horizontal tracheotomy for short-duration tracheostomy airway management.
The goal was assessment of a revolutionary approach to laryngeal stenting. A radically designed, atraumatic, inflatable, low-pressure, high-volume, endoscopically inserted laryngeal stent for effective intralaryngeal support or long-term prevention of aspiration was prospectively evaluated in a canine model to reveal any significant short- and long-term anatomic and functional changes in the larynx.
A self-sustaining, tube-free, long-term flap tracheostomy was performed in 14 dogs, followed by endoscopic laryngeal stent insertion. The stents were inflated, and their intraluminal pressures were monitored daily. The stenting period ranged between 3 and 46 days (mean 27.4 days). The animals were then euthanized, and total laryngectomy was performed. The larynges underwent gross and microscopic examinations, and a grading scale of reactive changes caused by the stent placement was created on the basis of the findings.
Dye studies for aspiration were negative in all animals. Gross findings consisted of varying degrees of small ulceration, localized polypoid lesions, and granulomas. Grossly, 9 dogs exhibited small superficial ulceration of the true vocal cords and posterior commissure. Six dogs developed minor polyps or polypoid changes and/or granulomas, respectively. No gross changes were seen in 2 of the dogs. Histopathologically, 10 dogs demonstrated grade I or II histopathologic changes. Only 4 of the dogs exhibited inflammation extending into the underlying cartilages, grade III. One dog did not complete the observation period.
This new stent demonstrated safety and biocompatibility with minimal local tissue reaction to its extended long-term placement. Good tolerance to the stent was documented, with minimal side effects similar to those that would be observed in human subjects after endotracheal intubation. When followed up in human patients, such minimal lesions have not resulted in significant long-lasting functional impairments. These initial results would indicate that this stent is well tolerated for long-term application and qualify as the preferred device for both management of aspiration and postoperative endolaryngeal bolstering support.
The studies reported here assessed pathophysiologic mechanisms that result from exposure to concentrated ambient particles (CAPs) in animals with and without cardiopulmonary compromise. These studies were carried out to determine the biologic plausibility of epidemiologic observations of increases in particulate air pollution associated with increases in human morbidity and mortality. Dogs were exposed two at a time to CAPs or filtered air via tracheostomy for six hours per day on three consecutive days. The electrocardiogram (ECG) and breathing pattern were recorded continuously, and indicators of inflammation were also assessed. In one experimental design, normal dogs were exposed in pairs to CAPs and subsequently to filtered air or to filtered air and subsequently CAPs (the double CAPs/double sham design). Comparisons were made between the CAPs measurements and each dog's own sham responses. In another design, one dog was exposed to CAPs while the chambermate received a sham exposure; these experiments were followed by crossover of the protocol the subsequent week (the crossover design). Comparisons were made between the CAPs exposure and both the chambermate's sham and each dog's own sham responses. The crossover experiments were conducted in normal animals and in animals who had undergone balloon occlusion of the left anterior descending (LAD) coronary artery to induce myocardial compromise. The effects of CAPs in animals with induced chronic bronchitis were part of the original specific aims; because these studies were not fully pursued, the results are presented only in Appendix A. In normal dogs, analyses of all double CAPs and crossover studies revealed low frequency (LF) and high frequency (HF) powers for heart rate variability (HRV) that were significantly higher for CAPs exposure compared to sham exposure. Variation in day-to-day exposure concentrations, aerosol composition, and pathophysiologic responses were also found. The crossover design, continuous measures of aerosol mass, and biologic responses were incorporated in the development of a statistical model that allowed isolation of changes associated with CAPs from changes due to animal variations. Comparison of individual exposures with this model revealed a range from no response in any measured parameter to statistically significant changes in cardiac autonomic balance, pulmonary air flow, and breathing pattern. On days in which dogs showed statistically significant changes in responses, the findings were consistent in both cardiac and respiratory parameters. Days associated with significant increases in LF and HF HRV, LF/ HF HRV ratio, and heart rate standard deviation (HR SD) were also associated with decreases in average heart rate. These same days had decreases in respiratory frequency, tidal volume, minute volume, and peak flows with corresponding increases in respiratory cycle times and enhanced pause (Pauenh), a measure of bronchoconstriction. These cardiac and respiratory changes suggest an effect mediated via both the sympathetic nervous system and the vagus nerve. Alternatively, days associated with increased heart rate had decreases in the HR SD; decreases or no change in HF and LF HRV; increases in respiratory flows and volumes; and decreases in breathing cycle times, all suggesting only sympathetic nervous system mediation. When all data from the crossover design experiments were assessed with this model, the heart rate and respiratory rate were significantly decreased in relation to both cumulative and actual exposure and the LF HRV, LF/HF HRV ratio, HR SD, and all other respiratory parameters were significantly increased (p < 0.0001 for all). When cardiac data were grouped by days in which the air mass trajectory came from the north or northwest (versus west, south, east, or northeast), significant increases in HR SD and HF HRV and significant decreases in average heart rate were associated with the northwest trajectory. (ABSTRACT TRUNCATED)
To compare outcomes of various surgical techniques for treatment of laryngeal paralysis in dogs and determine incidence and risk factors for development of postoperative complications.
Retrospective study.
140 dogs undergoing surgical treatment for laryngeal paralysis at a veterinary teaching hospital between 1985 and 1998.
Data were analyzed to determine outcome and factors influencing outcome and development of complications. Kaplan-Meier curves were constructed for survival analysis.
Postoperative complications were documented in 48 (34.3%) dogs; 20 (14.3%) dogs died of related causes. Aspiration pneumonia was the most common complication (33; 23.6%). Seven dogs died of aspiration pneumonia > 1 year after surgery. Dogs that underwent bilateral arytenoid lateralization were significantly more likely to develop complications and significantly less likely to survive than were dogs that underwent unilateral arytenoid lateralization or partial laryngectomy. Factors that were significantly associated with a higher risk of dying or of developing complications included age, temporary tracheostomy placement, concurrent respiratory tract abnormalities, concurrent esophageal disease, postoperative megaesophagus, concurrent neoplastic disease, and concurrent neurologic disease.
Results suggest that surgical repair of laryngeal paralysis may be associated with high postoperative complication and mortality rates. Surgical technique and concurrent problems or diseases increased the risk of complications. Dogs appeared to have a life-long risk of developing respiratory tract complications following surgical correction.
Experimental induction of chronic bronchitis in dogs Effects on airway obstruction and responsivenessPubMed: 6953777] Bartoli et al. Page
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Flow restrictor for measuring respi-ratory parameters. U.S. patent no. 6224.560B1
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Gazula GK, Godleski JJ. Flow restrictor for measuring respi-ratory parameters. U.S. patent no. 6224.560B1; 2001.
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