Antibody response in patients with osteomyelitis of the mandible.

Patients with mandibular osteomyelitis had quantification of 10 antibodies against certain bacterial proteins and polysaccharides. Sera from 31 patients with acute or chronic osteomyelitis of the mandible and from 17 healthy controls were analyzed. Some patients showed low levels of investigated antibodies in general and a lack of specific antiteichoic acid antibodies, as well as of different antipneumococcal antibodies particularly. Two patients with therapy-resistant osteomyelitis showed IgG2 and IgG3 subclass deficiency. They had replacement therapy with intravenous 10 or 15 gm immunoglobulin every 3 weeks for 6 months. Both patients showed considerable improvement in their clinical symptoms after treatment with immunoglobulin. This study indicates that impaired humoral immune response may be of importance in subgroups of patients with osteomyelitis of the mandible.

Experimental laryngeal reconstruction with preformed composite graft.

The use of perichondrial grafts for reconstruction of the thyroid cartilage of the larynx was studied in two series of rabbits. In the first pilot study the thyroid cartilage was replaced by a cartilage performed by the neochondrogenic effect of an auricular perichondrial graft set into the defect on a subcutaneous flap. When this transplantation technique proved successful, another series was performed where a laryngeal defect of the thyroid cartilage and the underlying mucosa were replaced by a preformed composite graft. This composite graft consisted of a biological support of newly formed cartilage from the neochondrogenic effect of a free perichondrial graft and mucosal lining made of a retention cyst from a free graft of oral mucosa. The newly formed composite graft was transferred to set into the laryngeal defect on a subcutaneous flap. The reconstruction was successful and all the rabbits survived, with no respiratory distress. The newly formed cartilage offered sufficient support to the reconstructed larynx. The lining formed from the mucosa of the retention cyst consisted of undiffered stratified squamous cells. This lining membrane was sufficient to control the fibrous tissue response and maintain patency of the restored lumen.

Prevention of tracheal stricture in end-to-end anastomosis.

The development of stenosis at the suture line after tracheal resection and end-to-end anastomosis of the trachea is associated with failure to approximate the tracheal ends. Evidently, stenosis invariably will occur if the viable mucosal edges are not properly adapted to each other. We developed a method of anastomosis affording accurate approximation of the tracheal ends and particularly of the mucosa by doing Z-plasties in the mucosa. This method of tracheal anastomosis, which is comparatively easy and safe to perform, may be used reliably and without the development of mucosal structures.

New parachute cuff and positive end-expiratory pressure to minimize tracheal injury and prevent aspiration.

A new parachute cuff has been tested in combination with a positive end-expiratory pressure (PEEP) on mongrel dogs. During positive-pressure ventilation the intracuff and intratracheal pressures showed synchronous, identical pressure variations, and therefore theoretically with this type of cuff the pressure against the tracheal wall would be minimal. The cuff provided a seal against gas leakage from the lungs throughout the entire test period, i.e., for up to 7 h. To avoid aspiration of mouth contents during the passive exhalation phase, different amounts of PEEP were tested. A PEEP of 4.0--8.0 cm H2O always produced a seal against a column of fluid in the mouth exerting a hydrostatic pressure of 5.4--8.8 cm H2O against the cuff. This seal was maintained during the whole test period. No difference in sealing capacity was found when the cuff was used with a normal respiratory frequency (20/min) and with high-frequency positive-pressure ventilation (60/min). When the PEEP is eliminated, e.g., when the respirator is disconnected for suction of the endotracheal tube, the sealing effect will be abolished. As the cuff extends up into the larynx there will be no pooling of fluid above the cuff. The risk of aspiration can therefore be diminished by suction of oral cavity before disconnecting the respirator. With the use of the pneumatic valve principle together with high-frequency positive-pressure ventilation, an open respirator system can produce a continuous PEEP, thereby preventing aspiration even during suctioning of the tracheal tube.

Intrathoracic goitre with the superior vena cava syndrome, hoarseness and acute stridor.

A 69-year-old man presented with acute stridor and was found to have the superior vena cava syndrome and bilateral laryngeal paresis. A clinical diagnosis of malignancy was made, but before any definite investigations could be made an emergency operation had to be performed to relieve the trachea. On operation the patient was found to have a benign goitre. The literature on the subject is discussed. Since the great majority of cases with the superior vena cava syndrome is caused by malignant diseases, it has been suggested that in acute cases radiation therapy should be started without a microscopic diagnosis if necessary, but such a practice must be warned strongly against.

The vessels of the rabbit trachea and ischemia caused by cuff pressure.

By intraarterial injection of silicone rubber we visualized the main feeding vessels of the rabbit trachea. They originate from the right subclavian artery and supply bilateral longitudinal tracheo-esophageal arteries. These lie in the groove between the trachea and the esophagus, giving off numerous segmental branches to both of these organs. In the trachea these pass submucosally between the tracheal cartilages, feeding a rich capillary network within the mucosa. The membranous part of the trachea is extremely well supplied with vessels, originating in arteries running longitudinally in the space between the trachea and the esophagus. The mucosa contains many sinusoidal ectasias, forming an almost cavernous arrangement in the tracheal wall. It is probable that these vessels are of great importance for the conditioning of inhaled air. Experimental studies on intubated animals have shown that a large-volume tracheal tube cuff, inflated to a pressure of 50 mm Hg, decreases or completely hinders capillary silicone rubber perfusion of the tracheal mucosa.

Blood flow in the rabbit tracheal mucosa under normal conditions and under the influence of tracheal intubation.

Isotope labelled microspheres were used to study the capillary blood perfusion of the rabbit tracheal mucosa. Under resting conditions the perfusion was about 0.3 ml/min - g (i.e. about 60% of the relative cerebral blood flow). Irritation of the tracheal mucosa by an endotracheal tube caused a steep rise in blood flow, tenfold or more. This was probably due to relaxation of the arterioles caused by a release of histamine-like substances. When an endotracheal tube is equipped with a small cuff (small resting diameter, low residual volume), the part of the mucosa in contact with the cuff, i.e. the mucosa covering the surface and edges of the cartilages, will be ischaemic at a cuff to tracheal wall pressure (C-T pressure) of greater than 30 millimeters of mercury. This abrupt ischaemia threshold contributes to the risk of deep mucosal damage with subsequent tracheal scarring, possibly proceeding to stenosis. Our present studies indicate that the ideal large cuff, with properties resembling those of an air cushion, will allow the major part of the arterial pressure to be propagated as far down as the capillaries. Under these conditions the cuff would permit some of the capillary blood perfusion of the tracheal mucosa covering the cartilages also at C-T pressures exceeding 30 mmHg. Although this investigation supports the concept that the ideal thin-walled large cuff interferes much less with the mucosal blood perfusion than the small cuff, we recommend that the cuff pressure be monitored and kept below 20 mmHg.

The trachea and cuff-induced tracheal injury. An experimental study on causative factors and prevention.

The effect of a large tracheal tube cuff on the rabbit tracheal mucosa was investigated by phase contrast microscopy and scanning (SEM) and transmission (TEM) electron microscopy. The tube was left in the trachea for 15 min. The cuff was either uninflated or inflated to a cuff-to-tracheal wall pressure (C-T pressure) of up to 100 mmHg. The uninflated cuff caused superficial damage to the epithelial lamina over regions where a cartilage was situated. When the cuff was inflated, it resulted in an increase of the mucosal damage, the extent of which was directly related to the pressure in the cuff. This took the form of both widening of the injured areas and penetration of the damage to deeper regions. At a C-T pressure of 100 mmHg the damage involved almost the entire mucosa and only small unaffected mucosal regions remained. At this stage it appeared as if the basement membrane had also begun to disintegrate. It is well known that a small cuff easily causes deep ulceration in the mucosa overlying the cartilages. From this investigation it was concluded that a large cuff causes the same type of ulceration if 1) the cuff wall is not sufficiently thin and pliable, and 2) if the cuff is overinflated enough to dilate the trachea to a diameter exceeding the cuff-diameter. At that moment there will be circumferential tension in the cuff and the sealing physics of the large cuff will become the sealing physics of a small (high pressure) cuff. A large cuff, properly handled, is more benign to the trachea than a small cuff. In order to avoid overinflation of the large cuff, the intracuff pressure (= C-T pressure) should always be measured by means of a four-way stopcock and an aneroid manometer. In the case of extended periods of mechanical ventilation with a high airway pressure, the resulting tracheal diameter at the cuff site should be checked radiographically.

Tracheal reconstruction with perichondrial grafts.

Since 1972 a series of experiments (Skoog, Ohlsén & Sohn, 1972; 1975; Ohlsén, 1976) has been performed to elucidate the potential of perichondrial grafts to generate cartilage. In 1974 Sohn & Ohlsén demonstrated in rabbits that tracheal cartilage could be reconstructed from free perichondrial grafts. As these studies were carried out with an intact tracheal mucosa a series of experiments was conducted in rabbits, and reported in this paper, in which a tracheal section containing two cartiliages and the covering mucous membrane was removed and replaced with a free perichondrial graft taken from the ear. New cartilege formed in all animals. The reconstructed portion of trachea was partly covered by ciliated cells of normal appearance, partly by low epithelium with microvilli. These latter areas were mainly within the central parts of the regenerated mucosa. The use of perichondrial grafts for tracheal reconstruction was also studied in two series of dogs. In four dogs a tracheal section, consisting of two comlete cartilages with the covering mucosa, was completely removed. The circumferential defect was reconstructed by free perichondrial grafats from rib cartilage. They were placed on two fascial flaps which had been raised from the adjacent muscles, rotated into the defect and sutured for complete coverage. Regeneration of cartilage occurred in all dogs, producing a biologic framework. The lining of the reconstructed tracheal section was completely restored by epithelialization from the surrounding mucosa. Low epithelial cells were successively replaced by columnar ciliated cells typical of the respiratory tract. The morphological development of the regenerated epithelium was demonstrated by electron microscopy. The regenerated mucosa exhibited normal function by passing mucus across the reconstructed area. This was recorded by filming at low speed using Cardio-green as indicator. All the animals of this series developed tracheal stenosis within the reconstructed portion. Another experiment was therefore carried out in which four dogs were subjected to the same operative procedure. Postoperatively, however, during the phase of healing, a silicon tube was inserted and left in situ to maintain expansion of the reconstructed portion. By this means stenosis could be prevented with good regeneration of the mucosal lining.