HFNC During Bronchoscopy for Bronchoalveolar Lavage

Study Overview
=================
Brief Summary
-----------------
The execution of diagnostic-therapeutic investigations by bronchial endoscopy can expose the patient to acute respiratory failure (ARF). In particular, the risk of hypoxemia is greater during broncho-alveolar lavage (BAL). For this reason, oxygen therapy is administered at low or high flows during the course of bronchoscopic procedures, in order to avoid hypoxemia. Few clinical studies have demonstrated the efficacy and safety of high flow oxygen through nasal cannula (HFNC) during BAL procedures, and no study has evaluated, during bronchial endoscopy, the effects of HFNC on diaphragmatic effort (assessed with ultrasound) and aeration and ventilation of the different lung regions (assessed with electrical impedance tomography). Therefore, investigators conceived the present randomized controlled study to evaluate possible differences existing during bronchoscopy between oxygen therapy administered with HFNC and conventional (low-flow) oxygen therapy, delivered through nasal cannula.

Detailed Description
-----------------
Patients with Acute Respiratory Failure may sometimes require a bronchial endoscopy for broncho-alveolar lavage (BAL). During the procedure, hypoxemia may worsen and oxygen may be require to avoid desaturation. In the recent years, High-Flow through Nasal Cannula (HFNC) has been introduced in the clinical practice. HFNC delivers to the patient heated humidified air-oxygen mixture, with an inspiratory fraction of oxygen (FiO2) ranging from 21 to 100% and a flow up to 60 L/min through a large bore nasal cannula. HFNC has some potential advantages. First of all, HFNC provides heated (37°C) and humidified (44 mg/L) air-oxygen admixture to the patient, which avoids injuries to ciliary motion, reduces the inflammatory responses associated to dry and cold gases, epithelial cell cilia damage, and airway water loss, and keeps unmodified the water content of the bronchial secretions. Second, HFNC determines a wash out from carbon dioxide of the pharyngeal dead space. Third, HFNC generates small amount (up to 8 cmH2O) of pharyngeal pressure during expiration, which drops to zero during inspiration. Fourth, HFNC guarantees a more stable FiO2, as compared to conventional oxygen therapy. Whenever the inspiratory peak flow of a patient exceeds the flow provided by a Venturi mask, the patient inhaled also part of atmospheric air. Electrical impedance tomography (EIT) is a noninvasive imaging technique providing instantaneous monitoring of variations in overall lung volume and regional distribution of ventilation, as determined by variations over time in intrathoracic impedance, which is increased by air and reduced by fluids and cells. EIT allows determining changes in end-expiratory lung impedance (EELI), a surrogate estimate of end-expiratory lung volume, assessing global and regional distribution of Vt, and obtaining indexes of spatial distribution of ventilation. Diaphragm ultrasound is a bedside, radiation free technique to assess the contractility of the diaphragm and the respiratory effort. In this study investigators aim to evaluate possible differences existing during bronchoscopy between oxygen therapy administered with HFNC and conventional (low-flow) oxygen therapy, delivered through nasal cannula in terms of respiratory effort (as assessed through diaphragm ultrasound), lung aeration and ventilation distribution (as assessed with EIT) and arterial blood gases.

Official Title
-----------------
High Flow Oxygen Therapy Through Nasal Cannula in Patients With Acute Respiratory Failure During Bronchoscopy for Bronchoalveolar Lavage

Conditions
-----------------
Acute Respiratory Failure, Bronchoscopy, Bronchoalveolar Lavage

Intervention / Treatment
-----------------
* Device: High Flow Nasal Cannula
* Device: Conventional Oxygen Therapy


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: need for bronchial endoscopy for bronchoalveolar lavage Exclusion Criteria: life-threatening cardiac aritmia or acute miocardical infarction within 6 weeks need for invasive or non invasive ventilation presence of pneumothorax or pulmonary enphisema or bullae recent (within 1 week) thoracic surgery presence of chest burns presence of tracheostomy pregnancy nasal or nasopharyngeal diseases dementia lack of consent or its withdrawal

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: High Flow Nasal Cannula<br>High Flow Nasal cannula is a system to deliver heated and humidified oxygen with an inspired oxygen fraction between 21 and 100% through large bore nasal cannula. The system delivers a flow up to 60 liters/min. | Device: High Flow Nasal Cannula<br>* High Flow Nasal Cannula will be set at 60 liters per minute of air/oxygen admixture to reach a peripheral oxygen saturation equal or greater than 94%<br>|
| Active Comparator: Conventional Oxygen Therapy<br>Conventional oxygen therapy will be administered through common nasal cannula with a flow up to 6 Liters per minute | Device: Conventional Oxygen Therapy<br>* Conventional Oxygen Therapy will be administered through nasal cannula with a oxygen flow set to achieve a peripheral oxygen saturation equal or greater than 94%<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Arterial blood gases at end of the procedure | Arterial blood will be sample for gas analysis | After 0 minute from the end of the bronchial endoscopy | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Respiratory effort at end of the procedure | The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction | After 0 minute from the end of the bronchial endoscopy | 
| Respiratory effort at baseline | The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction | After 0 minute from enrollment | 
| Respiratory effort at the beginning of the bronchoscopy | The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction | 5 minutes before the beginning of the bronchial endoscopy, while receiving the assigned treatment | 
| Respiratory effort after bronchoscopy | The respiratory effort will be assessed through the ultrasonographic assessment of the diaphragm thickening fraction | After 10 minute from the end of the bronchial endoscopy | 
| Change of end-expiratory lung impedance (dEELI) from baseline at the beginning of the bronchoscopy | change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography | 5 minutes before the beginning of the bronchial endoscopy, while receiving the assigned treatment, compared to baseline | 
| Change of end-expiratory lung impedance (dEELI) from baseline at end of the procedure | change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography | After 0 minute from the end of the bronchial endoscopy, compared to baseline | 
| Change of end-expiratory lung impedance (dEELI) from baseline after bronchoscopy | change from baseline, expressed in mL, of the end expiratory lung volume as assessed through electrical impedance tomography | After 10 minute from the end of the bronchial endoscopy, compared to baseline | 
| Change of tidal volume in percentage (dVt%) from baseline at the beginning of bronchoscopy | change from baseline, expressed in percentage, of the tidal volume as assessed through electrical impedance tomography | 5 minutes before the beginning of the bronchial endoscopy, while receiving the assigned treatment, compared to baseline | 
| Change of tidal volume in percentage (dVt%) from baseline at end of the procedure | change from baseline, expressed in percentage, of the tidal volume as assessed through electrical impedance tomography | After 0 minute from the end of the bronchial endoscopy, compared to baseline | 
| Change of tidal volume in percentage (dVt%) from baseline after bronchoscopy | change from baseline, expressed in percentage, of the tidal volume as assessed through electrical impedance tomography | After 10 minute from the end of the bronchial endoscopy, compared to baseline | 
| Arterial blood gases at baseline | Arterial blood will be sample for gas analysis | After 0 minute from enrollment |