Impact of Current Volume Under High-rate Nasal Oxygen Therapy During Acute Hypoxemic Respiratory Failure de Novo

Study Overview
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Brief Summary
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De novo acute hypoxemic respiratory failure (AHRF) is associated with high overall mortality, which increases significantly with the use of orotracheal intubation. High flow nasal canula (HFNC) has turned to be the first line non-invasive oxygenation strategy aiming to avoid intubation. One of the main factors worsening lung injury and increasing mortality in invasively ventilated patients is a too high tidal volume (TV) delivered by the ventilator. Consistent data suggest that such an aggravation of respiratory lesions may occur during spontaneous ventilation if TV is too large. This phenomenon is called Patient self-inflicted lung injury (P-SILI). The effect of TV on the outcome of patients with de novo AHRF under HFNC has never been evaluated since TV is not easily accessible in patients under HFNC. Investigators hypothesized that a large TV during HFNC has an impact on the outcome. TV will be measured using chest Electrical Impedance Tomography (EIT). To calibrate the EIT data, i.e. to be able to convert changes in thoracic impedance into TV, thoracic impedance signal, flow and volume will be collected during a 4 cmH2O continuous positive airway pressure (CPAP) test, using a pneumotachograph inserted on the ventilator circuit between the mask and the Y-piece. Such a level of CPAP is supposed to reproduce the majority of the physiological effects of HFNC. Thus, EIT signal can be used to calculate TV during HFNC since it remains reliable even when the positive expiratory pressure changes. A secondary objective is to quantify a respiratory distress index. This quantification will be recorded by respiratory inductance plethysmography (RIP), obtained using two elastic bands equipped with a sensor sensitive to their stretching, one positioned at the level of the thorax, the other at the level of the abdomen. The stretching changes of the two bands during the respiratory cycle allow evaluating their possible asynchronism by calculating the phase angle Investigators want to be able to evaluate up to 6 predictors of HFNC failure in this research with an effect size of 0.15, α risk of 0.05, and a power of 0.8. A number of 55 participants is required. Investigators plan to include 60 patients due to potential withdrawal of consent and/or unusable data.

Official Title
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Impact of Current Volume Under High-rate Nasal Oxygen Therapy During Acute Hypoxemic Respiratory Failure de Novo

Conditions
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Acute Hypoxemic Respiratory Failure

Intervention / Treatment
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* Diagnostic Test: Assessment of tidal volume using Electrical Impedance Tomography (EIT) during high flow nasal canula(HFNC)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age ≥ 18 years old HFNC initiated as part of the care Respiratory rate > 25 / minute PaO2/FiO2 ratio < 300 mm Hg PaCO2 < 45 mm Hg Affiliated with a social security system Informed consent signed by the patient, trusted person or family member if the patient is unable to consent Exclusion Criteria: Acute cardiogenic pulmonary edema Underlying chronic respiratory disease Asthma exacerbation Chronic obstructive pulmonary disease Exacerbation Hemodynamic instability, defined as systolic arterial blood pressure < 90 mm Hg or mean arterial blood pressure < 65 mm Hg or the use of vasopressors Glasgow Coma Score <= 12 Contraindication to CPAP (maxillofacial surgery, facial trauma) Refusal of the patient to perform the CPAP test Need for emergency intubation according to the clinician in charge of the patient Patient protected by law Pregnancy or breastfeeding woman

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Interventional Model Description: Tidal volume (TV) during high flow nasal canula (HFNC) will be measured using chest Electrical Impedance Tomography (EIT). To calibrate EIT data, i.e. to be able to convert changes in thoracic impedance into TV, thoracic impedance signal, flow and volume will be collected during a 4 cmH2O continuous positive airway pressure (CPAP) test, using a pneumotachograph inserted on the ventilator circuit between the mask and the Y-piece. Such a level of CPAP is supposed to reproduce the majority of the physiological effects of HFNC. The quantification of respiratory distress index will be recorded by respiratory inductance plethysmography (RIP), obtained using two elastic bands equipped with a sensor sensitive to their stretching, one positioned at the level of the thorax, the other at the level of the abdomen. The stretching changes of the two bands during the respiratory cycle allow evaluating their possible asynchronism by calculating the phase angle.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Experimental<br>Every adult patient admitted to the medical intensive care unit for de novo acute hypoxemic respiratory failure, and placed under hign flow nasal canula (HFNC). Inclusion and exclusion criterion are listed elsewhere. | Diagnostic Test: Assessment of tidal volume using Electrical Impedance Tomography (EIT) during high flow nasal canula(HFNC)<br>* After information and consent, patients under HFNC for de novo acute hypoxemic respiratory failure will undergo a ten minutes 4cmH2O continuous positive airway pressure(CPAP) test while monitored with 1)chest Electrical Impedance Tomography (EIT) 2) a pneumotachograph inserted on the ventilator circuit between the mask and the Y-piece and connected to a differential pressure sensor, and 3) respiratory inductance plethysmography (RIP). Airway flow signal will be acquired using an analog/digital converter and stored for further analysis with acknowledge software. This will allow converting EIT data into tidal volume (TV), and estimating TV under HFNC. RIP signals will allow evaluating asynchronism between chest and abdomen by calculating the phase angle, thus quantifying respiratory distress. Patients monitored with an arterial catheter, arterial blood gas measurements will be done during CPAP and HFNC. These measures will be collected the first day of HFNC, and everyday up to three days<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Failure of high flow nasal canula (HFNC) at day 28 | Failure of HFNC is defined as death or need for invasive mechanical ventilation | Day 28 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Tidal volume under high flow nasal canula (HFNC) | Tidal volume will be measured using chest Electrical Impedance Tomography (EIT) | Day 0, Day 1 and Day 2 | 
| Phase angle computed by respiratory inductance plethysmography (RIP) | Phase angle will be measured by respiratory inductance plethysmography | Day 0, Day 1 and Day 2 | 
| Respiratory rate | respiratory rate will be measured at each evaluation | Day 0, Day 1 and Day 2 | 
| pH under high flow nasal canula (HFNC) | pH will be measured via Blood gases | Day 0, Day 1 and Day 2 | 
| PaO2 under high flow nasal canula (HFNC) | PaO2 will be measured via Blood gases | Day 0, Day 1 and Day 2 | 
| PaCO2 under high flow nasal canula (HFNC) | PaCO2 will be measured via Blood gases | Day 0, Day 1 and Day 2 | 
| SaO2 under high flow nasal canula (HFNC) | SaO2 will be measured via Blood gases | Day 0, Day 1 and Day 2 | 
| Regional tidal volume. | computed by Electrical Impedance Tomography | Day 0, Day 1 and Day 2 | 
| Mortality | Mortality at Day 28, Day 90 | Day 28, Day90 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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High flow nasal canula / P-SILI/ AHRF / EIT