Respiratory Effects of Flow-Controlled Ventilation and Jet Ventilation in Patients Undergoing Laryngotracheal Surgery

Laryngotracheal surgery often requires a small diameter endotracheal tube to oxygenate patients under general anesthesia. Oxygenation is often only possible with high-frequency jet ventilators due to the use of small diameter and high resistance airway cannulas.

Flow controlled ventilation is a new ventilation modality capable for ventilation through a small diameter endotracheal tube (Tritube) with an active expiratory phase and the possibility of controlled carbon dioxide elimination during mechanical ventilation.

The aim of the present trial is to characterize perioperative changes in lung volume, ventilation inhomogeneity and respiratory mechanics in patients undergo upper airway surgery under general anesthesia with either flow controlled or high-frequency jet ventilation.

This study is a randomized, controlled, assessor blind, monocentric study.

A new ventilation mode, called Flow Controlled Ventilation (FCV), has been suggested to minimize the amount of dissipated energy in the lungs and potentially could be protective during mechanical ventilation. FCV is unique in creating a stable gas flow into and also out of the patient's lungs to generate inspiration and expiration respectively. The FCV ventilation mode by its design allows the use of an ultrathin endotracheal tube with an inflatable cuff to secure the airways for ventilation. Therefore FCV offers several new surgical options for the treatment during laryngeal and tracheal surgery where the standard approach is usually the use of high-frequency jet ventilation (HFJV). The limitations of HFJV are however the lack of airway protection, limited monitoring of the respiratory variables and potential carbon dioxide (CO2) accumulation.

Participants for this study will be recruited at the University Hospitals of Geneva, scheduled for laryngotracheal surgery under general anesthesia. A total of 50 patients will be enrolled and randomly assigned into 2 groups: Group FCV (Flow controlled ventilation) and Group HFJV (high-frequency jet ventilation).

Measurements of functional residual capacity (FRC) and lung clearance index (LCI) will be performed in patients with a nitrogen multiple breath washout method, before and approximately 1 hour after surgery. Similarly, respiratory system resistance (R) and respiratory reactance (X) will be measured at the same time by using the Forced Oscillation Technique.

Relevance: There are no studies that addressed the value of flow controlled ventilation in terms of lung function parameters (FRC and LCI) and lung mechanics (R, X) in comparison to high-frequency jet ventilation in patients undergoing upper airway surgery.

Eligibility Criteria:
Inclusion Criteria:

* Informed Consent signed by the subject
* General anesthesia for laryngotracheal surgery
* Adult patients, female and male, over 18 years of age
* Elective surgery

Exclusion Criteria:

* Documented severe heart conditions (New York Heart Association Class 4, severe pulmonary hypertension)
* Documented severe respiratory disease (uncontrolled asthma, severe pulmonary fibrosis, chronic obstructive pulmonary disease GOLD 4)
* Documented severe Neurological diseases (Acute ischemic and hemorrhagic stroke within the preceding 3 months, uncontrolled seizures)
* Surgery that requires tracheotomy
* Obesity (Body Mass Index ≥ 30 kg/m2)
* Inability to follow the procedures of the study (mental condition or language barrier e.g. incomprehension of French language)
* Previous enrolment into the current study or other study that involves unknown medication in the past 12 months
* Allergy or contraindication to Propofol and/or Remifentanil and/or Rocuronium