Prostaglandin D2 causes accumulation of eosinophils in the lumen of the dog trachea

Prostaglandin D2 (PGD2), the major product of arachidonic acid metabolism via the cyclooxygenase pathway in most mast cells, is present in the airways of atopic asthmatic patients after antigen challenge. Because eosinophilia is characteristic of asthma, we asked whether PGD2 causes eosinophils to accumulate in the airways in vivo. Using an endotracheal tube with two inflatable balloons we isolated a segment of trachea in four anesthetized mechanically ventilated dogs, and we superfused this segment with either a control solution (Hanks' balanced salt solution and antibiotics) or solution containing PGD2 (10(-6) M). Total and differential cell counts were determined at base line and every hour for 4 h during the study. PGD2 caused eosinophil accumulation in the trachea [7.0 +/- 3.4, 28.7 +/- 17.8, 33.7 +/- 13.6, and 35.4 +/- 10.7 (SD) cells/cm2 trachea after 1, 2, 3, and 4 h, respectively, P less than 0.05 vs. controls] but had no significant effect on neutrophil accumulation. The effect of PGD2 on eosinophil accumulation was significantly inhibited by the prostaglandin receptor antagonist SKF 88046 (5 mg/kg iv). We conclude that PGD2 is a selective stimulus that causes accumulation of eosinophils in the tracheal lumen of dogs in vivo.     

Tracheal length changes during zebra finch song and their possible role in upper vocal tract filtering

Sounds produced in the avian vocal organ may be modified by filter properties of the upper vocal tract. Possible mechanisms to actively control filter characteristics include movements of the beak, tongue, and larynx and adjustments of tracheal length. We investigated whether length changes of the trachea are a likely mechanism for adjusting upper vocal tract filter properties during song in the zebra finch (Taeniopygia guttata). Tracheal length was monitored at the basal end using sonomicrometry and was recorded together with subsyringeal air sac pressure and acoustic output. Tracheal shortening occurred at the onset of song bouts, and during each motif the tracheal length decreased during expiratory pressure pulses and increased during the short inspirations. A bilateral tracheal syringeal nerve cut confirmed that the initial shortening at the onset of the song bout is an active shortening of the trachea (i.e., mediated by syringeal muscle activity). The modulation of length during the motif was not affected by the denervation and is most likely driven by the pressurization of the interclavicular air sac. The absolute length change during the motif was small (<0.2 mm) and not clearly related to acoustic features of the song. For example, some high-frequency syllables, which are generated during inspiration, were accompanied by tracheal elongation. Because this elongation shifts tube resonances to lower frequencies, it is inconsistent with an active adjustment of length to enhance high frequency sounds. The small magnitude and inconsistent nature of dynamic tracheal length changes during song make it unlikely that they significantly affect vocal tract filter properties if the trachea is modeled as a rigid tube.     

A novel and simple method for endotracheal intubation of mice

Endotracheal intubation in mice is necessary for experiments involving intratracheal instillation of various substances, repeated pulmonary function assessments and mechanical ventilation. Previously described methods for endotracheal intubation in mice require the use of injection anaesthesia to immobilize the animal during the intubation procedure or the use of a volatile anaesthetic prior to intubation for immobilization. With these methods, the control of anaesthetic depth during the intubation procedure is absent. We describe a method for simple and rapid intratracheal intubation in mice for mechanical ventilation, using a self-built plastic support to facilitate the intubation procedure. General anaesthesia is maintained by means of inhalation through a non-rebreathing circuit connected to the plastic support. This set-up gives the operator control of anaesthetic depth and sufficient time to perform the intubation procedure. A purpose-made laryngoscopic blade is used to facilitate the intubation tube entering the trachea. The blade of the purpose-made laryngoscope is constructed as a retraction guide and is curved for easy handling. Under direct vision, the epiglottis is gently lifted by the laryngoscopic blade while the intubation tube is pushed into the trachea. Following this novel intubation technique, we were able to mechanically ventilate mice for at least 2 h without severely disturbing blood gases. Histological evaluation of the lungs and microscopic evaluation of the trachea and larynx showed no signs of trauma related to the intubation technique or mechanical ventilation.     

A method of endoscopic endotracheal intubation in rabbits.

Endotracheal intubation in rabbits is a formidable task and has led to the devising of a new endoscopic method. Sixty New Zealand White rabbits (2.0-3.5 kg) underwent experimental left thoracotomy requiring mechanical ventilation. After anaesthetic induction was achieved, the animal was placed in a supine position. A rigid 30 degrees endoscope was passed through a 4.5 mm endotracheal tube (ET) and then used to advance, under direct vision, through the oropharynx and vocal cords. Once passing the vocal cords, the ET was advanced into the trachea as the endoscope was withdrawn. All animals were successfully intubated within 30 s to 2 min and then ventilated. No complications or deaths occurred during or after intubation, or postoperatively. No instances of oesophageal intubation occurred. All animals survived long-term. Thirty animals underwent necropsy at 10 days and, 30 at 30 days, with no postoperative evidence of orotracheal injury. We have established a new method of endotracheal intubation in rabbits. It is reliable, effective, non-traumatic, safe, and expeditious.     

Effects of upper airway pressure on abdominal muscle activity in conscious dogs.

We have examined arousal and abdominal muscle electromyogram (EMGabd) responses to upper airway pressure stimuli during physiological sleep in four dogs with permanent side-hole tracheal stomata. The dogs were trained to sleep with a tightly fitting snout mask, hermetically sealed in place, while breathing through a cuffed endotracheal tube inserted through the tracheostomy. Sleep stage was determined by behavioral and electroencephalographic criteria. EMGabd activity was measured using bipolar fine-wire electrodes inserted into the abdominal muscle layers. Static increases or decreases in upper airway pressure (+/- 6 cmH2O), when applied at the snout mask or larynx (upper trachea), caused an immediate decrease in EMGabd on the first two to three breaths; EMGabd usually returned to control levels within the 1-min test interval. In contrast, oscillatory pressure waves at 30 Hz and +/- 3 cmH2O amplitude (or -2 to -8 cmH2O amplitude) produced an immediate and sustained reduction in IMGabd in all sleep states. Inhibition of EMGabd could be maintained over many minutes when the oscillatory pressure stimulus was pulsed by using a cycle of 0.5 s on and 0.5 s off. Oscillatory upper airway pressures were also found to be powerful arousal-promoting stimuli, producing arousal in 94% of tests in drowsiness and 66% of tests in slowwave sleep. The results demonstrate the presence of breath-by-breath upper airway control of abdominal muscle activity.     

A simple laryngoscopic technique for the endotracheal intubation of rabbits

A safe and reliable technique for the endotracheal intubation of rabbits is described. Direct laryngoscopy is followed by intubation of the trachea with a fine catheter, and subsequent advancement of the endotracheal tube over this catheter.     

Effect of air humidity on spinability and transport capacity of canine airway secretions

The effect of varying the inspired air humidity on a rheological property (spinability) and transport capacity of airway mucus has been analyzed in 10 mongrel dogs. Tracheal mucus was collected in anesthetized dogs inspiring through an endotracheal tube the air of a climate chamber maintained at constant temperature (T degrees:20 degrees C). In one test, the dogs inspired air at an absolute humidity (AH) of 9 g water/m3 air directly through the endotracheal tube. In the other test, the dogs inspired through an artificial nose connected to the endotracheal tube giving a AH of 30 g water/m3 air. Tracheal mucus was collected at the external distal end of the endotracheal tube. The spinability (Sp) or thread-forming properties of mucus was measured. The relative mucociliary transport rate (TR) of mucus was analyzed on a frog palate epithelium preparation. The transport rate was significantly (p less than 0.01) lower (range: 0.59-0.80) when the AH of the inspired air was low in comparison to that obtained with high AH (range: 0.70-1.13). The variations in mucus Sp due to changing AH were positively and significantly correlated (r = 0.80, p less than 0.01) with the corresponding variations in TR. These results suggest that lowering the AH of air induces a decrease in the transport capacity which appears to be dependent on the change of spinability that occurs in the mucus.     

A simple method for rat endotracheal intubation.

A simple, fast, reliable, and atraumatic method of endotracheal intubation was developed to provide long-term mechanical ventilation in rats. Light from a focused point source directed to the outside of the skin just anterior to the pharyngoepiglottic region penetrated the skin, muscles and trachea and allowed direct visualized placement of an endotracheal tube.     

Velocity profiles in central airways with endotracheal intubation: a model study

Steady inspiratory velocity profiles were measured at two flow rates in a 3:1 scale model of the human central airways in the presence of five modes of endotracheal intubation. The presence of an orifice or a short endotracheal tube had no significant effect on the velocity profiles distal to the carina. Long endotracheal tubes change the profiles in both main bronchi. A significant peak occurred in the frontal plane near the walls, and the maximum velocity in the airway was almost identical to the endotracheal tube center-line velocity. The flow impinging on the medial wall of the main bronchus was redirected up around the anterior and posterior walls yielding bipeak velocity profiles in the sagittal plane. A tube placed eccentrically in the trachea over the right main bronchus did not alter the velocity profiles in the left main bronchus, suggesting a redirection of flow over the carina into the left lung. An endobronchial tube at the mouth of the right main bronchus did change the shape of the velocity profiles in the left main bronchus. In the left upper lobar bronchus the presence of trachea intubation had no effect on the velocity profiles. However, in the right upper lobar bronchus, the long endotracheal tube flattened the velocity profiles from the strongly skewed ones seen in the absence of the endotracheal inserts. These results not only are relevant to distribution of ventilation and aerosol particle deposition, but also have strong implications in intrapulmonary gas mixing, especially when high-frequency low tidal-volume ventilation is involved.     

Effects of dry air and subsequent humidification on tracheal mucous velocity in dogs.

The impairment of mucociliary transport by dry air breathing and the restoration of function with subsequent humidification of inspired air were investigated in anesthetized dogs. Tracheal mucous velocity was measured by a cinebronchofiberscopic technique. The breathing of dry air through an uncuffed endotracheal tube produced almost complete cessation of the flow of tracheal mucus after 3 h. Subsequent breathing of air at 38 degrees C with 100% relative humidity restored tracheal mucous velocity to control values by the end of and additional 3 h. Histologic examination of the trachea at the end of the 3-h dry air breathing period revealed focal areas of sloughing of the ciliated epithelium and submucosal inflammation. Although morphometry was not employed, the inflammatory changes appeared to have progressed during 3 h of breathing fully humidified air subsequent to the dry air breathing period. These findings were consistent with previous reports that the inflammatory response to injury of the tracheobronchial mucosa might be delayed and that the mucociliary transport system has a great deal of functional reserve. We found that an artificial heat and moisture exchanger placed on the proximal end of an endotracheal tube partially protects against the suppression of tracheal mucous velocity caused by dry air breathing.     

Functional anatomy of the vagal innervation of the cervical trachea of the dog.

The canine cervical trachea has been used for numerous studies regarding the neural control of tracheal smooth muscle. The purpose of the present study was to determine whether there is lateral dominance by either the left or right vagal innervation of the canine cervical trachea. In anesthetized dogs, pressure in the cuff of the endotracheal tube was used as an index of smooth muscle tone in the trachea. After establishment of tracheal tone, as indicated by increased cuff pressure, either the right or left vagus nerve was sectioned followed by section of the contralateral vagus. Sectioning the right vagus first resulted in total loss of tone in the cervical trachea, whereas sectioning the left vagus first produced either a partial or no decrease in tracheal tone. After bilateral section of the vagi, cuff pressure was recorded during electrical stimulation of the rostral end of the right or left vagus. At the maximum current strength used, stimulation of the left vagus produced tracheal constriction that averaged 28.5% of the response to stimulation of the right vagus (9.0 +/- 1.8 and 31.6 +/- 2.5 mmHg, respectively). In conclusion, the musculature of cervical trachea in the dog appears to be predominantly controlled by vagal efferents in the right vagus nerve.     

Effects of helium-oxygen mixtures on endotracheal tubes: an in vitro study

QUESTION: To determine flow pattern and critical Reynolds numbers in endotracheal tubes submitted to different helium-oxygen mixtures under laboratory conditions. MATERIALS AND METHODS: Flow-pressure relationships were performed for seven endotracheal tubes (rectilinear position, entry length applied) with distal end open to atmosphere (predicted internal diameters: 6-9 mm). Nine helium-oxygen mixtures were tested, with FIHe varying from zero to 0.78 (increment: 10%). Nine flows were tested, with rates varying from 0.25 to 1.60 l s(-1) (increment: 0.15 l s(-1)). Gas flow resistance was calculated, and for each endotracheal tube, a Moody diagram was realised. Flow regime and critical Reynolds numbers were then determined (fully established laminar, nonestablished laminar, smooth turbulent, or rough). RESULTS: Even low concentration of helium in inspiratory mixture reduces endotracheal tubes resistance. Effect is maximal for high flows, small tube and high FIHe. Critical Reynolds numbers are inversely correlated to tube diameter. ANSWER: Under laboratory conditions, flow pattern in endotracheal tubes varies from fully established laminar to rough. Knowledge of the critical Reynolds numbers allows correct application of fluid mechanic formula when studying tube or gaseous mixture effects on respiratory mechanisms.     

Complications of microsurgical reconstruction of obstetrical brachial plexus palsy

The charts of the 173 consecutive patients who underwent microsurgical reconstruction for obstetrical brachial plexus palsy from 1988 to 1999 (inclusive) in the Division of Plastic Surgery at the Hospital for Sick Children were analyzed. The overall complication rate was 33.5 percent, and there was no mortality in this series. The most significant intraoperative complication was accidental extubation, which occurred five times in the first 84 patients (6 percent of this early group; 2.9 percent of the whole series). This complication was addressed by suturing the endotracheal tube to the membranous septum and by using a transparent drape to allow direct visualization of the tube in all 89 subsequent patients. There have been no further accidental extubations. Postoperative fluid overload occurred in 14 patients (8.1 percent), three (1.7 percent) of whom developed pulmonary edema. Intensive care unit admission was required in two of those patients. Diuretic treatment was required in seven patients. No patient receiving less than or equal to 4 ml/kg/hour developed fluid overload, whereas 50 percent of the patients receiving greater than or equal to 10 ml/kg/hour did. Currently, the authors' policy is to strictly limit intravenous maintenance fluids to 4 ml/kg/hour or less. Despite the long and complex procedure required to reconstruct obstetrical brachial plexus palsy, the incidence of significant complications can be minimized with simple precautions, such as suturing the endotracheal tube to the septum or reducing the amount of fluids administered during the operation.     

Neurogenic plasma extravasation: inhibition by morphine in guinea pig airways in vivo

Opioid drugs have been shown to inhibit neurogenic plasma exudation in skin by a presynaptic mechanism. We determined whether a similar inhibitory effect operates in the airways of anesthetized guinea pigs in vivo with the use of Evans blue dye as a marker of plasma leakage. Stimulation of the vagus nerve significantly increased leakage of dye in trachea and main bronchi (by approximately 300 and 600%, respectively). Similar increases in leakage were seen in the presence of atropine and propranolol. Morphine (1-30 mg/kg iv) inhibited leakage in a dose-related manner with complete inhibition in the trachea at a dose of 30 mg/kg. The inhibition was blocked by the opioid receptor-antagonist naloxone (1 mg/kg iv). Intravenous substance P significantly increased leakage but was not inhibited by morphine. We conclude that morphine inhibits neurogenic plasma leakage by presynaptic inhibition of release of neuropeptides from sensory nerve endings. If similar mechanisms are operative in human airways, inhibition of neurogenic plasma leakage by opioid drugs devoid of central effects may be of value in the therapy of asthma.     

Determination of Mineral Elements in Gentiana rigescens from Different Zones of Yunnan, China

The concentrations of nine mineral elements were determined by atomic absorption spectroscopy in Gentiana rigescens from three zones (middle, southeast, and northwest zones) of Yunnan province in China. The average concentrations of mineral elements were found in the order K>Ca>Mg>Fe>Na>Zn>Cu>Cr>Se. Samples collected from the middle zone of Yunnan were enriched in Na (242.24 ± 50.80 mg/kg) and Mg (959.78 ± 54.60 mg/kg). However, materials from the southeast zone were particularly enriched in Ca (3,448.70 ± 749.82 mg/kg), but depleted in Se. Whereas those from the northwest zone were plentiful of K (2,746.89 ± 84.84 mg/kg), Fe (923.06 ± 127.52 mg/kg), Zn (261.38 ± 53.05 mg/kg), Cu (110.08 ± 46.23 mg/kg), and Se (53.99 ± 22.38 mg/kg).     

Tracheal venous blood and lymph collection: a model to study airway injury in sheep

Airway injury is a frequent result of the inhalation or aspiration of toxic material. Although upper airway damage can be identified endoscopically, pathophysiological changes are difficult to evaluate. This paper describes an animal model in which changes in tracheal blood and lymph flow rates, wet-to-dry weight ratios, and lymph-to-plasma protein ratios can be evaluated after injury. In this model, 12 cm of the cervical trachea were isolated using a double-cuffed endotracheal tube and injured with cotton smoke at near room temperature. Injury to the trachea was evaluated in twenty-five anesthetized sheep 4 (n = 3), 8 (n = 3), 24 (n = 3), 48 (n = 3), 96 (n = 3), and 192 (n = 2) h after smoke exposure and compared with sham control animals (n = 8). A significant increase in tracheal venous blood flow from 1.3 +/- 0.4 (SD) ml.min-1.cm-1 for the noninjured trachea to 2.8 +/- 1.2 was noted 24 h after injury (P less than 0.01). Lymph flow significantly increased from 1.3 +/- 0.4 microliters.min-1.cm-1 for the noninjured trachea to 9.8 +/- 3.3 24 h after injury while wet-to-dry weight ratios were elevated from 3.0 +/- 0.2 for noninjured trachea to 4.6 +/- 0.9 from 4 to 24 h after injury (P less than 0.01) and decreased to 3.7 +/- 0.5 by 96 h. Cast material consisting of airway exudate, cellular debris, and intact ciliated epithelial cells was both expectorated and found in the trachea when the animals were killed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oral endotracheal intubation of rats for intratracheal instillation and aerosol drug delivery.

As reported in the literature, oral endotracheal intubation of rats is considered to be very difficult. Specialised equipment and complicated techniques have been described to perform this procedure. In our experiment we adopted a simple method, which allowed-without any complicated equipment-the insertion of a relatively wide tube into the trachea of rats, allowing drug administration.     

Bronchial distribution of gas mixing in a model of the upper and central airways

Longitudinal mixing of He, O2, and sulfur hexafluoride boluses with air flowing through a three-generation tracheobronchial airway model was evaluated as the increase in volume variance of gas concentration distributions monitored at upstream and downstream sampling ports. Mixing was partitioned between tracheal and branched regions of the model at steady inspiratory and expiratory airflows from 0.044 to 0.884 l/s, both in the absence and in the presence of a removable larynx cast. During inspiration in the absence of the larynx, mixing increased as airflow increased, reaching a peak value at 0.2 l/s, and decreasing as airflow increased further. This mixing peak was higher in the branched region than in the tracheal region and was inversely related to the diffusion coefficient of the indicator gas-air mixture. During inspiration in the presence of the larynx, a mixing peak was observed in the tracheal region, but mixing peaks in the branched region were eliminated by turbulence propagated downstream from the larynx. During expiration, laryngeal turbulence was propagated far enough downstream (i.e., proximal to the trachea) that mixing peaks could be observed in both tracheal and branched regions whether or not the larynx cast was present.     

Reduction of hypoxic pulmonary vasoconstriction during trichloroethylene anesthesia.

A double-lumen tube was inserted into the trachea of dogs anesthetized with intravenous pentobarbital (30-40 mg/kg). Blood flow/unit lung volume in each lung was measured with 133Xe. Both lungs were initially ventilated with oxygen and measurements of pulmonary blood flow, CO2 output, cardiac output, and blood gases were made. When nitrogen was administered to one lung blood flow was diverted to the opposite lung. The diversion of flow was reduced by the inhalation of 1% trichloroethylene but returned after withdrawal of the anesthetic. There were no significant changes in cardiac output. Changes in CO2 output and arterial Po2 were compatible with the xenon results. It is concluded that trichloroethylene may increase arterial hypoxemia by reducing vasoconstriction in hypoxic areas of lung.     

Effects of cyclohexenonic long-chain fatty alcohol on diabetic rat trachea

In order to investigate the diabetes-associated neuropathy and prevent effects of cyclohexenonic long-chain fatty alcohol, a neurotrophic substance, in trachea, we studied its effect on streptozotocin-diabetic hyper-reactivity in the rat trachea. Diabetes was induced in 8-week-old male Sprague-Dawley rats by administering an intraperitoneal injection of streptozotocin (50 mg/kg). The rats were divided randomly into four groups and were maintained for four weeks: age-matched control rats, diabetic rats without treatment with cyclohexenonic long-chain fatty alcohol, and diabetic rats treated with cyclohexenonic long-chain fatty alcohol (2 and 8 mg/kg, i.p. every day). The serum glucose and insulin levels were determined, and the contractile responses of the trachea induced by carbachol and KCl were investigated. Treatment with cyclohexenonic long-chain fatty alcohol did not alter the rats' diabetic status, i.e., body weight, thickness of the trachea, serum glucose levels, and serum insulin levels, but significantly improved the diabetic-induced hyper-reactivity of the rat trachea in a dose-dependent manner. There was no significant difference in either the carbachol- or KCl-induced contractile forces between groups with or without mucosa in the functional studies. In histological examinations, thinning of cricoid cartilage, thickness of basal membrane, and degeneration, fragmentation of elastic fibers in the submucosal layer, and hypertrophy of smooth muscle bundle in the membranous wall of trachea were observed in the diabetic rat trachea, which were improved by treatment with cyclohexenonic long-chain fatty alcohol. Our data indicate that this drug can prevent hyper-reactivity in the diabetic trachea.