A new tracheostomy tube. III. Bronchofiberoptic examination of the trachea after prolonged intubation with the NL tracheostomy tube

The Brandt tube system attenuates the cuff deflationary phenomenon after anesthesia with nitrous oxide

The Brandt tube system can limit excessive cuff pressure during nitrous oxide (N(2)O) anesthesia, but there is a lack of data assessing whether the Brandt tube system avoids cuff deflation after cessation of N(2)O administration. In this study, we recorded air-filled cuff pressures of the Mallinckrodt Brandt or Hi-Contour (control) tracheal tubes (Mallinckrodt, Athlone, Ireland) during 67% N(2)O anesthesia and the cuffs were aspirated if the cuff pressure exceeded 22 mm Hg; 180 min later, O(2) was substituted for N(2)O. The cuff pressure of both groups significantly decreased after N(2)O anesthesia but the time required for the cuff pressure to return to the initial pressure was longer in the Brandt group than in the control group (76.5 +/- 35.2 min and 36.5 +/- 18.1 min, respectively; P = 0.03). The incidence of air leaks was more frequent in the control group than in the Brandt group (P = 0.015); changes in intracuff N(2)O were small in the Brandt group (6.6 +/- 1.2% to 3.4 +/- 0.9%) compared with those in the control group (46.2 +/- 3.8% to 18.6 +/- 5.6%). Therefore, the Brandt tube system attenuates the cuff deflationary phenomenon after N(2)O anesthesia, whereas repeated cuff deflation during N(2)O anesthesia causes cuff deflation after cessation of N(2)O, resulting in a possible risk of air leaks.

An assessment of a method of inflating cuffs with a nitrous oxide gas mixture to prevent an increase in intracuff pressure in five different tracheal tube designs apparatus

We assessed the efficacy of inflating cuffs with a nitrous oxide gas mixture to minimise changes in intracuff pressure during anaesthesia. Patients were randomly assigned to one of five groups of 15 subjects each, and the trachea was intubated with the Profile Soft-Seal Cuff, Hi-Contour, Reinforced, Sheridan or Trachelon tracheal tubes. Cuffs were inflated with 40% nitrous oxide and cuff pressure was measured during anaesthesia with 67% nitrous oxide. Concentration of nitrous oxide in the cuff was measured at the end of anaesthesia. Cuff pressure increased slightly but significantly in the Reinforced and Trachelon groups. Nitrous oxide concentration in the Reinforced, Sheridan, or Trachelon groups was slightly but significantly higher than that in the Profile or Hi-Contour groups. Cuff pressure never exceeded 22 mmHg and there were no air leaks. Therefore, inflating cuffs with 40% N2O preserves stable cuff pressure in all five tracheal tubes, despite differences in cuff and pilot balloon design.

The effect on intracuff pressure of various nitrous oxide concentrations used for inflating an endotracheal tube cuff

We sought to determine the optimal concentration of nitrous oxide (N(2)O) for inflating endotracheal tube cuffs, to avoid overinflation and air leaks. Female patients undergoing endotracheal intubation (inner diameter 7.5 mm) during anesthesia with 67% N(2)O were randomly assigned to five groups of 25 subjects each, in which cuffs were inflated with 0% (Air), 30% (N30), 40% (N40), 50% (N50), or 67% (N67) N(2)O. The cuff pressure and the N(2)O concentration in the cuff were measured. In an additional 15 patients (N40-a group), pilot balloons were replaced with metal tubes, and the mouths and noses of the patients were wrapped with tape, to minimize N(2)O efflux into the air. Postoperative sore throats were evaluated in double-blinded interviews. Cuff pressures increased significantly in the Air and N30 groups but decreased in the N67 group. Cuff pressures were <22 mm Hg in the N40 and N50 groups, but the N50 group had air leaks. The N(2)O concentration in the cuff in the N40 group was significantly smaller than that in the N40-a group, suggesting N(2)O rediffusion. The incidence of sore throats (40% in the Air group) was reduced significantly in the N40 and N50 groups. Therefore, 40% N(2)O is optimal for filling the cuff during anesthesia with 67% N(2)O.

IMPLICATIONS

Nitrous oxide (N(2)O) diffuses into the cuff, equilibrating at a smaller concentration than the gas mixture with which patients are ventilated. Our data indicate that inflation of the cuff with 40% N(2)O is recommended to prevent both excessive endotracheal cuff pressure and air leaks during anesthesia with 67% N(2)O, reducing postoperative sore throats.

Minitracheotomy: complications and follow-up with fibreoptic tracheoscopy

Complications and changes in tracheal mucosa after minitracheotomy were evaluated in 28 patients. Tracheal mucosa was inspected fibreoptically after the insertion of a minitracheotomy cannula, and then at 3-day intervals until the cannula was removed. Thereafter, assessments were made every third day until the mucosa was considered normal. Three significant complications occurred: mediastinal puncture, paratracheal entrance of the cannula and subcutaneous emphysema. Difficulties at insertion of the minitracheotomy cannula were encountered in 15 of 28 patients (54%). Air flow detected through the cannula in one patient, and lack of air flow in another patient, were misleading signs of the position of the cannula. Passing a suction catheter in three patients and a normal end-tidal carbon dioxide tracing in one patient, were also found to be misleading. The correct position and possible complications could be verified only by fibreoptic tracheoscopy. Changes in the tracheal mucosa were independent of the duration of minitracheotomy therapy.

Airway lesions caused by prolonged intubation with standard and with anatomically shaped tracheal tubes. A post-mortem study

Two groups of patients intubated for long periods were examined post mortem. In Group A (22 patients) the mean duration of intubation was 4.0 days and in Group B (19 patients) 5.7 days. The mean for the two groups was 4.8 days. In Group A a conventional endotracheal tube was used, and in Group B an anatomically shaped tube. Both tubes had cuffs of the intermediate-volume, low-pressure type. The larynx and trachea, from the epiglottis to the bifurcation, were removed in one piece at autopsy and the inner surface was photographed. The photographs were magnified and from these the size and estimated depth of any lesions were recorded. In the arytenoid and tracheal regions no significant difference was found between the two groups. In the cricoid region, on the other hand, the outcome was significantly more favourable following use of the anatomically shaped tube.

Airway complaints and laryngeal pathology after intubation with an anatomically shaped endotracheal tube

In a group of 100 patients intubated with standard polyvinyl chloride (PVC) endotracheal tubes, 26 spontaneously complained of airway discomfort postoperatively. A further 55 patients complained of airway discomfort upon direct questioning. In a comparison group of 100 patients intubated with PVC orotracheal tubes shaped to conform with the anatomy of the airway, the corresponding figures were 14 and 21. Laryngoscopy before and 5 days after intubation revealed that among patients intubated with standard tubes there was a significantly higher frequency of mucosal lesions at the cricoid plate and at the posterior commissure of the larynx, but lesions at the medial side of the arytenoids occurred to approximately the same extent in the two groups.

Design and function of tracheal suction catheters

Tracheal suction catheters damage the mucosa of the airway, due to both the pull from the vacuum and insertion of the catheter. The pull of the vacuum from a suctioncatheter was measured on a Mettler balance. An open side hole reduced the pull by around 90% and a distance of 1 mm gave a reduction of around 90%. The combination of one side hole and a 1 mm distance gave a 99% reduction of the pull. The difference between one or more side holes was measured. The suction efficacy was higher with a single side hole than with several side holes. On the basis of these measurements and a review of the literature, the principles were outlined for the construction of a suction catheter which provided maximum suction efficacy and caused minimum damage: (1) a moderate to strong vacuum was to be used; (2) the catheter was to have a single hole at the tip and a single side hole placed at the convex side of the angle; (3) both side hole and tip hole should be so constructed that the holes were kept at a distance from the mucosa; and (4) the tip should be angulated.