Tracheal Dilatation in Pediatric Patients With Acquired Tracheal Stenosis, and the Effects of Apneic Oxygenation

The study presents an alternative method of tracheal dilatation in pediatric patients with acquired tracheal stenosis. Dilatation is performed by the use of balloon catheter connected with manometer, that is bronchoscopic guided into trachea in the stenotic area, through the wide canal of supraglottic device i-Gel. Every dilatation cession consists of three consequent tracheal balloon dilatations of maximum 3 minutes duration each, followed by 10-15minutes interval of controlled ventilation. The balloon is inflated for 60 seconds to reach predefined pressure, and then deflated. This method is minimal traumatic for tracheal mucosa, and application of several dilatation procedures every 2-3months, in pediatric patients with acquired tracheal stenosis, may lead to a relative reopening of trachea and recession of clinical symptoms.For the right performance of the dilatation procedure, patients receive general anesthesia with cessation of spontaneous ventilation. During procedure, controlled ventilation-oxygenation is impossible, because the i-Gel canal is occupied by bronchoscope and balloon catheter, so patients will remain apneic for a short period of time. For pediatric patients is important to perform proper preoxygenation prior to procedure, and to maintain oxygenation as long as possible during procedure. This is achieved by application of apneic oxygenation, through a small catheter, connected to high flow oxygen. Participants are exposed during first dilation to no oxygenation, while during second and third dilatation to apneic oxygenation. Aim of the study is to investigate primarily whether application of apneic oxygenation, in pediatric patients during tracheal balloon dilatation, maintains regional cerebral oxygen saturation rSO2 in significant higher levels, compared with no application of oxygenation. rSO2 levels are a sensitive index of oxygenation efficacy of the brain, accordingly this refers to a safe procedure. Secondary issues are whether application of apneic oxygenation maintains pulse oximetry SpO2 and artierial oxygen partial pressure PaO2 in higher levels, and what are the effects on arterial carbon dioxide partial pressure PaCO2 and on haemodynamic parameters (heart rate, blood pressure), compared with no application of apneic oxygenation.

The study is taking place in the Bronchoscopy Unit of the 3rd Pediatric Dpt of the Aristotles University of Thessaloniki, in the area of the Operating Rooms in the Hippokratic General Hospital of Thessaloniki, Greece. The procedure of tracheal balloon dilatation was developed and performed in Hippokratic General Hospital of Thessaloniki, Greece, for the last three years. From October 2020, pediatric patients are recruited and enrolled in this study, according to specific criteria, set by the Collaborators of the Pulmonology and Bronchoscopy Unit of the 3rd Pediatric Dpt of Aristotles University of Thessaloniki, Greece. Prior to the dilatation procedure, following steps are necessary, performed by the Principal Investigator:

1.detailed preanesthetic evaluation of the participant, for recognition of clinical signs or pathology, that can complicate the procedure and jeopardize health status 2. written informed consents from parents/caregivers, for anesthesia procedure, for tracheal dilatation procedure, and for participation in the study. All recordings during procedures are performed by the Principal Investigator, and double checked by two Collaborators.In cases of appearance of adverse events during the procedure (i.e. severe desaturation, anaphylactic reaction, severe bronchospasm), it is automatically discontinued, advanced life support is initiated, anesthesia is terminated, and participants are closely monitored during recovery.

Sample size calculation was performed according to G\* power analysis 3.1.9.2. and the Means test: for extraction of results is necessary to record at least five different pediatric patients, who will undergo at least four tracheal dilatation cessions.

For statistical analysis, quantitative variables will be described as median values and standard deviation (or IQR), qualitative variables as frequencies and percentages, while significancy level will be defined as \<0.05.

Eligibility Criteria:
Inclusion Criteria:

* Persistent clinical signs of inspiratory stridor, combined with high pitched cry, hoarse voice, persistent cough or recurrent inspiratory tract infections
* Bronchoscopic conferment of tracheal stenosis from the subglottic area to the area above carina
* Maintenance of clinical symptoms despite intensive and long drug therapy with inhalational steroids, adrenalin or salbutamol
* Urgent need for expansion of trachea, because of risk of full obstruction of trachea

Exclusion Criteria:

* children with haemodynamic instability prior or during the procedure
* children with active respiratory tract infection
* children with low hemoglobin levels - anemia
* children with physical status, according to the American Society of Anesthesiologists, III and IV
* parents who refuse the participation of their children in the study and to sign the informed consent