Effects of Treatment With High Flow Nasal Cannulas on Respiratory Pattern and Work of Breathing Among Healthy Subjects

Study Overview
=================
Brief Summary
-----------------
This study evaluates the work of breathing among healthy subjects under various conditions of treatment with high flow nasal cannulas. Ten subjects will be included. The design of this study is a cross over of five treatment periods with different flow settings.

Detailed Description
-----------------
High flow oxygen therapy (HFOT) is a promising technique increasingly used in the management of acute respiratory failure. In hospitalised hypoxemic patients, recent clinical evidence showed that HFOT can reduce endotracheal intubation and reduce mortality. Physiologically, the HFOT causes a decrease in respiratory rate and minute-ventilation and may be associated with a decrease in carbone dioxyde arterial pressure. It is possible that these effects are associated with decreased work of breathing, which could explain some of the benefits in terms of comfort and efficiency. The objective of this research is to evaluate the impact of a wash-out of anatomical dead space by high flow nasal cannulas on respiratory parameters and on the work of breathing among healthy subjects. The investigators will evaluate the baseline status in room air, and then compare it with four different levels of flow. The primary endpoint will be the work of breathing.

Official Title
-----------------
Effects of Treatment With High Flow Nasal Cannulas on Respiratory Pattern and Work of Breathing Among Healthy Subjects

Conditions
-----------------
Respiratory Failure

Intervention / Treatment
-----------------
* Device: High flow nasal cannulas
* Device: Conventional flow via nasal prongs


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Healthy subjects Written and informed consent Exclusion Criteria: Pregnant or breastfeeding women; Subject enrolled in another study excluding co-enrolment; Cardio-vascular or respiratory disease; History of ear nose and throat disease (i.e. surgery, epistaxis, trauma), eso-gastric disease (i.e. esophageal varices, digestive haemorrhage), rheumatologic or neurologic disease possibly interfering with the design of the study; Subject feeling nauseous or under recent fed condition (<1h).

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

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

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

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

Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: No flow<br>Subjects will be spontaneously breathing in room air with no flow. | |
| Experimental: Conventional flow via nasal prongs<br>Subjects will be breathing with nasal prongs delivering 5 L/min of air (inspired fraction of oxygen: 0.21) | Device: Conventional flow via nasal prongs<br>* Low flow of air delivered through conventional nasal prongs<br>|
| Experimental: High flow nasal cannulas 20 L/min<br>Subjects will be breathing with high flow nasal cannulas delivering 20 L/min with an inspired fraction of oxygen of 0.21. | Device: High flow nasal cannulas<br>* Comparison of different flow levels<br>* Other names: Airvo 2; Ficher and Paykel HealthCare;|
| Experimental: High flow nasal cannulas 40 L/min<br>Subjects will be breathing with high flow nasal cannulas delivering 40 L/min with an inspired fraction of oxygen of 0.21. | Device: High flow nasal cannulas<br>* Comparison of different flow levels<br>* Other names: Airvo 2; Ficher and Paykel HealthCare;|
| Experimental: High flow nasal cannulas 60 L/min<br>Subjects will be breathing with high flow nasal cannulas delivering 60 L/min with an inspired fraction of oxygen of 0.21. | Device: High flow nasal cannulas<br>* Comparison of different flow levels<br>* Other names: Airvo 2; Ficher and Paykel HealthCare;|

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

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Work of breathing | Work of breathing at the end of each period is calculated from the measurement of esophageal pressure and tidal volume (composite outcome). | 10 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Esophageal pressure-time product | Measured at the end of each period | 10 minutes | 
| Tidal Volume | Measured at the end of each period | 10 minutes | 
| Comfort of breathing | Subjective evaluation at the end of each period | 10 minutes | 
| Blood gases | Arterial or capillary blood gases at the end of each period | 10 minutes | 
| Dyspnea | Evaluation on a borg scale at the end of each period | 10 minutes | 
| Respiratory Rate | Measured at the end of each period | 10 minutes | 
| End-tidal carbon dioxide | Measured at the end of each period | 10 minutes | 
| Heart rate | Measured at the end of each period | 10 minutes | 
| Oxygen saturation | Measured at the end of each period | 10 minutes |