Surgical resection of a primary tracheal fibrosarcoma in a dog

A four-year-old, entire male Rottweiler was presented with a history of respiratory distress. A tracheal mass was diagnosed on thoracic radiographs and tracheoscopy. Surgical excision of three tracheal rings incorporating the tumour was performed. The mass was found to be a low-grade fibrosarcoma. Twenty-four months later, the owner reported that there was no recurrence of respiratory distress and the dog appeared to be doing well clinically. This case of primary tracheal fibrosarcoma suggests that this type of tumour should be listed in the differential diagnoses for tracheal neoplasia in dogs and that surgical treatment alone may be curative.

Evidence that guanylate cyclase is involved in modulating the resting tension and neurally induced contraction of the guinea pig tracheal muscle

Electrical field stimulation of guinea-pig tracheal muscle strips produced a frequency-dependent biphasic response consisting of an initial cholinergic contraction followed by relaxation. Both phases of the response were of neural origin. In the presence of methylene blue, a guanylate cyclase inhibitor, the resting tension and the contraction were increased, but the accompanying relaxation was inhibited. However, in the presence of sodium nitroprusside, guanylate cyclase activator, the resting tension was reduced and the contraction was inhibited, but the relaxation was prolonged and increased. Similarly, in the presence of either 3-isobutyl-lmethylxanthine, which promotes cyclic guanosine monophospate (cGMP) accumulation, or 8-bromo-cGMP, an analogue of cGMP, the resting tension was reduced and the contraction was inhibited but the relaxation was prolonged and increased. From these results, it is concluded that guanylate cyclase is involved in modulating the resting tension and the neurally-induced contraction of guinea-pig tracheal muscle(AU)

Activation of guanylate cyclase in the guinea-pig trachea reduces contractile responses of the smooth muscle

Guinea-pig tracheal strips were used to investigate whether activation of guanylate cyclase in the trachea can reduce the contractile response of the smooth muscle. Guanylate cyclase was activated by glyceryl trinitrate and a combination of sodium nitrite and ascorbic acid. These activators inhibited tracheal smooth muscle contractions produced by acetylcholine histamine and electrical field stimulation. However, in the presence of methylene blue, a guanylate cyclase inhibitor, tracheal smooth muscle contractions were not inhibited by the activators. But, in the presence of propranolol, which blocked inhibition mediated by beta-adrenoceptor, both glyceryl trinitrate and the sodium nitrite/ascorbic acid combination were still capable of inhibiting tracheal smooth muscle contractions. Additionally, methylene blue inhibited tracheal smooth muscle relaxation that was electrically induced. These results suggest that the inhibitory action mediated by activated guanylate cyclase may be a mechanism for regulating tracheal smooth muscle contractile reponses (AU)

Comparative observations of mucus transport velocity in health and disease

The present study evaluated mucus transport velocity (MTV) in different areas of the tracheobronchial tree in vitro in normal, acute and chronic bronchitic animals. The average MTV in animals ranged from 11.5 mm/min in the trachea to 0.64 mm/min in the pre-terminal bronchus. Chronic bronchitic animals showed mucus hypersecretion, areas of ciliary abnormality and mucus stagnation. The mean transport velocities ranged from 21.2 mm/min in the trachea to 4.1 mm/min in the pre-terminal bronchus. In the acutely ill animals, MTV ranged from 2.5 mm/min in the trachea to zero below the upper lobar bronchus. It is postulated that the higher than normal values in chronic bronchitis are due to altered mucus rheology, increased peristalsis and linear acceleration; whereas those in acute bronchitis were attributed to an early phase of viral or bacterial infection. (AU)

Tracheobronchial function in health and disease: effect of mucolytic substances

The effect of mucolytic and expectorant substances on ciliary beat frequency, mucus transport velocity and mucus production, was investigated in normal and bronchitic rats. The results showed that: (i) N-acetylcysteine and S-carboxymethylcysteine were mildly cilioexcitatory at low and ciliodepressive at higher concentrations in both normal and bronchitic rats. A similar pattern was seen in mucus transport velocity. (ii) Bisolvan enhanced all aspects of muciciliary activity in both groups of animals. Sobrepin was less effective than Bisolvan and more effective than Tachoquilin. (iii) Geleomytrol, Ozothin and prostaglandin E1 were all cilioexcitatory in rats with bronchitis. Mucus transport velocity was similarly stimulated by both Geleomyrtol and Ozothin. (iv) Ammonium chloride and potassium iodide enhanced mucociliary activity in normal and bronchitic rats. (v) All substances stimulated mucus production, however, the most potent was prostaglandins E1. The mechanisms for increased mucociliary activity involve inter alia the probable cleaving of disulphide bridges, decreased mucosal swelling, altered rheological characteristics and stimulation of adenylate cyclase (AU)

Insignificance of colonic bacteria in the sputum of patients in a new ICU

Over a 12-month period, 27 percent of patients in a new ICU grew bacterial pathogens from sputum or tracheal cultures. The commonest isolates were Pseudomonas aeruginosa and Klebsiella species. Endotracheal intubation, the length of time intubated, and antimicrobial therapy all predisposed to the isolation of organisms from sputum. No patient developed a gram-negative pneumonia, and there was no case of septicemia associated with a positive sputum culture. The presence of epithelial or pus cells in sputum was unrelated to the culture results. It was concluded that the growth of colonic bacteria from sputum or tracheal aspirates was of little prognostic or clinical significance. No significant common environmental site or cross-infection pathway was identified: sinks were contaminated by patients rather than vice versa. Most sputum isolates were probably endogenous in origin. (AU)

A method for comparing endotracheal cuffs: a controlled study of tracheal trauma in dogs

Damage to the trachea produced in dogs by large and small residual volume cuffs during 6 h of IPPV was compared using a specifically designed endotracheal tube. The cuffs under evaluation were adjusted to exert similar average pressures on the tracheal walls, so that many of the variables believed responsible for tracheal injury were controlled. The tube compliance of the cuff was measured with tube inside and outside the trachea of the anesthetized dogs. The maximum estimated pressure transmitted to the tracheal wall, derived from these compliance curves, was found to equal the peak airway pressure in the presence of a small air leak past each cuff. At various tracheal wall pressures there were only minor differences in tracheal damage between the large and small residual volume cuffs tested (AU).

Tracheobronchomegaly

Over fifty cases of tracheobronchomegaly reported in the literature are reviewed and two new cases are described. The radiological appearances of this rare condition are described and its concomitant occurrence with bronchiectasis is noted. The condition is thought to be due to faulty development of the connective tisssues of the tracheobronchial tree. However, a study of the age of presentation showed that the majority presented in the third or later decades which suggests that it is an acquired rather than a developmental anomaly. (AU)

Critical anatomical site in healthy subjects from observation of forced expiratory volume curves with external resistances

The internal diameter of the air passages narrows from the trachea to the periphery of the lungs. Because of this it should be possible to predict the site at which the greatest change in resistance would occur for a given flow rate using the orifice flow equation (P = p/Cý(1/A2ý 1/A1ý) Vý where p = density of air, C = discharge constant which depends on the roughness of the tube and on Reynolds number, V is the volume rate of flow and A1 and A2 are the cross sectional areas) and compare it with forced expiratory volume curves (FEV) in healthy subjects. Theoretical calculations showed that the 3rd-6th generation of the bronchial tree contributed about 40 percent to the total airway resistance. Direct measurements by previous workers showed that approximately 55 percent of the total pulmonary resistance was contributed by the 3rd-6th generation i.e. 3-6 mm internal diameter bronchi. Results of FEV curves in normal subjects against external resistance of known internal diameters will be presented. These results show that the critical orifice (i.e. the point at which greatest inflection begins in the FEV curve) is in the range of 6-9 mm internal diameter (around the 3rd generation of the tracheobronchial tree). An analog of the tracheobronchial tree is being prepared to simulate the resistance to breathing, and thereby provide a simple method of measuring airway resistance (AU)

Guide to endobronchial tubes

The salient features of currently available bronchus blockers, single and double lumen endobronchial tubes are briefly discussed (AU)