Physiological Effect High-flow Tracheal Oxygen on Viscosity of Airway Mucus and Respiratory Effort in Patients Weaning from Invasive Mechanical Ventilation

Rationale: Tracheostomized patients weaning from mechanical ventilation are at risk for dryness of airway mucosa and sputum accumulation during disconnection from mechanical ventilation. High-flow tracheal oxygen (HFTO) is being used as supportive therapy during disconnection sessions in tracheostomized patients weaning from invasive mechanical ventilation (IMV) to limit dryness while maintaining oxygenation. We recently summarized the studies comparing physiological effects HFTO as compared to other interfaces, collectively referred to as conventional oxygen therapy (COT), in a systematic review and identified areas of lacking knowledge: effect on sputum viscoelasticity, respiratory effort early in the weaning process and dyspnea sensation. We hypothesize that HFTO, compared to COT, decreases viscoelasticity of the sputum and provides respiratory support during weaning. This may improve weaning by facilitating clearance of airway mucus, preventing respiratory failure, and providing comfort by decreasing dyspnea.

Objective: To determine the physiological effect of HFTO compared to COT on sputum viscoelasticity, respiratory effort and dyspnoea.

Study design: Pilot study with randomized crossover design, single-center. Study population: Twenty adult patients weaning from mechanical ventilation with tracheostomy.

Intervention (if applicable): Crossover with COT and HFTO during two days in the weaning phase.

Main study parameters/endpoints: Primary endpoint: sputum viscoelasticity measured by rheology during long disconnection sessions in the final phase of weaning. Secondary endpoints: respiratory effect measured by swings in esophageal pressure (PES) and prevalence and severity of dyspnoea sensation by visual analogue scale (VAS).

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: The study compares two therapeutic modalities both used in clinical care without side-effects or complications. Study procedures and measurements consist of standard clinical procedures that are performed daily in clinical setting with negligible risk of deterioration for the patient. During weaning with HFTO sputum clearance might be more easy for the patient and respiratory effort might decrease, both are assumed to be beneficial for the weaning process of the patient.


Eligibility Criteria:
Inclusion:

* Age ≥18 years
* Weaning from mechanical ventilation with tracheostomy

Exclusion Criteria:

* Longstanding tracheostomy, defined as tracheostomy being present prior to current hospital admission
* Tracheostomy primarily indicated for chronic upper airway obstruction or to secure airway patency due to persistent stupor/coma
* Chronic positive pressure respiratory support at home (excluding night-time continuous positive airway pressure for sleep apnea)
* Mucociliary disease in medical history (e.g. cystic fibrosis, pulmonary ciliary dyskinesia)
* Neuromuscular disease in medical history (excluding ICU-acquired weakness)
* Contra-indication placement oesophageal balloon for measurement of PES, such as:

  * Fractures in mandibular, orbital or ethmoid bone or skull base
  * Esophageal varices or surgery in medical history
  * Severe bleeding disorders
* Hemoptysis in 72 hours prior to the first disconnection session. Clinically relevant hemoptysis is defined as hemoptysis requiring tracheal/endobronchial or radiologic intervention, or administration of pro-coagulating drugs such as tranexamic acid.