Stridor of the larynx and the trachea, according to world statistics, are of iatrogenic origin in 90% to 95% of cases.The reasons are as follows: prolonged intubation, tracheotomy, removal of vocal cords (chordectomy). They are also an occasional result of laryngeal operations.

In spite of our exact knowledge of the causes of iatrogenic stridor there is no apparent tendency to reduce these alarming figures. Reconstruction of the constricted laryngeal lumen and tracheal opening is usually a multi – stage operational procedure, requiring knowledge of several techniques, advanced equipment allowing treatment to be adjusted to the age of the patient, the local state of health and the extent of the constriction.

The Dental Otholaryngological Hospital of A.M Warsaw has dealt with constrictive complications of the larynx and the upper trachea for 11 years. The experience gained in this time fully convinces us of the need to extend the use of endoscopic intervention procedures. The usage of high frequency ventilation increases the effectiveness of endoscopic procedures. High frequency ventilation (HFV) may be defined as ventilation where the frequency of the respiration used is four times higher than that of the patient in the resting state. The limit value for adults is set at 60 breaths/min (1 Hz) and the limit value for infants is 120 breaths/min (2 Hz) (1).

The aim of HFV is reduction of the average and the maximum pressures in the respiratory tract. This is achieved by using a much lower than normal respiratory volume (1-5 ml/kg). We should distinguish 3 different types of HFV:

– HFPPV high frequency positive pressure ventilation;

– HFJV high frequency jet ventilation;

– high frequency oscillation.

The above – named HFV types vary in the following aspects among others; the respiratory volume, ventilation frequency, and expiration where in HFPPV and in HFJV expiration is active and in HPO it is passive. The basic difference that exists between HFPPV and HFJV is the way in which the gases are supplied to the respiratory tract (1).

In the period 1990 to 2000 in the Dental Otholaryngological Hospital of the Medical Academy in Warsaw, 115 patients with stridor of the larynx and trachea were treated. The constrictions were of an anatomical nature, and 160 patients had paralysis of both sides, that is functional stridor. For 5 years the treatment of stridor has been helped by HFJV. For this technique we qualified patients exceeding 17 years of age with first or second degree stridor according to Cotton, as well as patients with vocal cord paralysis on both sides, who had no earlier tracheotomy due to the local conditions and pressure in the vocal cords not allowing precise execution.

This ventilation method was used in 6 patients with anatomical stridor and in 5 patients with functional stridor. In all cases HFJV was used in conjunction with TIVA (total i.v. anaesthesia), using Propofol in a continous infusion together with fractioned doses of Fentanyl, an opiod and Tracrium, and Pavulon which is an anti – spasmic drug.

The respiratory gases were given through a catheter (in 9 patients) or through a needle directed through the skin to the opening of the trachea (2 patients). In all these cases an effort was made to stabilise the catheter so that the ends were visible throughout the whole operation and were kept a safe distance from the bifurcation of the trachea. Reconstruction of the lumen was done by using classical microsurgical – techniques as well as using Nd-Yag and Holm-Yag lasers. Usually these techniques were combined and applied depending on the effectiveness in the stipulated conditions. The result in 10 cases was satisfactory patency in a single stage procedure, and only in one case from the anatomical stridor group were we forced to use the next stage of surgical treatment. We observed only one complication, in the form of pneumothorax of the right lung of a patient. She had been ventilated by catheter. She needed several days observation and was treated conservatively.

Similar to other authors, we always combined HFJV with total intravenous anaesthesia (2). Endoscopic procedures are thus less traumatic and allow more natural access to the obturatory pathology of the larynx and trachea. They are the method of choice. Usually it was impossible to assure effective ventilation with an appropriate view of the constriction area. The presence of intubation tubes makes resection of the stenosis impossible. This leaves the operator with no choice but to perform tracheostomy, which automatically lengthens the period of treatment. The same patient experiences the negatives effects of tracheotomy. The use of HFPPV gives a positive effect, increasing safety in the operating area (3). This allows accurate judgement of changes, and precise elimination.

Lack of an intubation tube gives a more true endoscopic picture of actual conditions in the patient´s respiratory tract, and allows better treatment adapted to the patient´s needs. This aspect is especially important in the treatment of functional stridor, where little resistance in the stridor area allows intubation with tubes of a larger size than the actual cross – section of the respiratory tract. Small size ventilation catheters (Xomed Hunsaker Mon – Jet ventilation) used in HFPPV can be the device of choice in patients with a more severe stridor, due to the avoidance of trauma to the respiratory tract (4). This reduces the risk of iatrogenic complications like postoperative swelling or granulation and formation of scars. HFPPV is highly rated in operations with the use of lasers, where it reduces the potential threat of explosion of gases in the respiratory tract. In the eighties lasers were used on a large scale in endoscopic techniques. Later CO₂ lasers and Nd-Yag and Holm-Yag lasers were used. In our clinic we used a Nd-Yag laser, at first which is conducted by a fibre optic and its energy (unlike the CO₂ laser) enters deep into the tissue, even several centimetres, causing coagulation. In such a type of technique surgeons had to get used to the immediate effect of treatment. At low power and short exposure times coagulation effects were seen after two hours in the form of swelling of tissue, where the laser had also hit neighbouring tissue. Precise judgement during the procedure allows avoidance of re-intubation or tracheotomy for this reason. Today we consider the Nd-Yag laser as the tool of choice when removing primary or secondary granulations. From 1998 we introduced the Holm laser to treatment. It is an impulse laser with possibilities of regulating the power every 50 mJ to 450 mJ. Like the Nd-Yag laser, it is directed by a fibre optic light. Its action can be compared with the action of a classical knife. The depth in tissue is a few micrometres. Coagulation of small blood vessels allows operating without any bleeding. The Holm laser works similarly on all types of tissue. In soft tissue, remember the effect of acoustic waves, which increases the depth of destruction. In laryngology it was found from 1991 in endoscopy procedures of the sinuses as well as in the nose and throat (6). The Holm laser even allows the removal of cartilage. Its properties, as well as the usage of HFPV, makes reopening possible in the larynx, and in upper tracheal type II/III changes according to Cotton (7). These are treated using external access. The advantage of using endoscopic treatment is the certainty that the reopened channel will have support from cartilage.

1. The use of HFJV with TIVA is a very useful method in anaesthesia in microsurgery.

2. Usage of HFJV in endoscopic procedures increases the precision of judement of changes and precise elimination.

3. The use of HFJV allows a reduction of indications for external access procedures and decreases indications for tracheostomy.

4. Ventilation with HFJV increases the safety of laser operations in the larynx and trachea.