High Flow Nasal Cannula in Thoracic Surgery: a Physiologic Study

Study Overview
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Brief Summary
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The goal of this study is to evaluate the role that high-flow nasal cannulas (HFNC) have on respiratory drive, work of breathing and neuromuscular efficiency after lung resection surgery. The main question the investigators aim to answer is whether HFNC decrease respiratory drive by at least 15% in these patients, assessed by a special diaphragmatic electromyography (EMG) device (NAVA catheter). In order, to perform this study, the investigators will perform a physiological study in 40 patients. These patients will be assessed in the immediate postoperative period and HFNC will be compared to conventional face-mask therapy.

Detailed Description
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Single centre, physiological crossover clinical trial in 40 patients in the immediate postoperative period after lung resection, equipped with a NAVA catheter to monitor diaphragm electrical activity (EAdi) and assess the effects that HFNC have on the respiratory drive and work of breathing as compared to conventional facemask oxygen therapy. Once in the postoperative care unit (PACU) and 1) after recovery from anaesthesia, 2) cardiorespiratory stable and 3) pain-free (see below), the intervention will start. The study will assess the effect of HFNC and oxygen via face mask on EAdi and diaphragm function, as measured by ultrasonography. HFNC and oxygen via face mask order will be randomized in a sequence (A-B or B-A) with the aid of a website (www.randomization.com). Each intervention will last for 30 minutes. The oxygen-inspired fraction (FiO2) will be adjusted to maintain a pulse oximetry (SpO2) between >92%. In the case of the high-flow nasal cannula, the study will be carried out with a flow of 50 L/min. EAdi signal will be continuously monitored and its signal later exported to a laptop for further analysis. At the end of the 30-minute period, a blood sample will be obtained for gas analysis from the arterial line and the investigators will perform a diaphragm ultrasonography. Ultrasonography will consist of measurement of diaphragm thickness and thickening on the right side during quiet breathing and diaphragmatic excursion on both sides.

Official Title
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High Flow Nasal Cannula in Thoracic Surgery: a Physiologic Study

Conditions
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Thoracic Surgery, Respiratory Failure

Intervention / Treatment
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* Device: High-flow nasal cannula


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subjects submitted to lung resection with an expected mechanical ventilation time of more than 180 minutes. Exclusion Criteria: Patient refusal to participate Contraindications to nasogastric tube placement (i.e. oesophageal varices) Patients less than 18 years old Pregnancy Neuromuscular disease Prior thoracic surgery

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: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| No Intervention: Face-mask oxygen therapy<br>Oxygen delivered through a conventional face mask to keep saturation above 92%. | |
| Active Comparator: High-flow nasal cannula<br>High-flow nasal cannula delivered at 50 L/min and FiO2 adjusted to keep saturation above 92%. | Device: High-flow nasal cannula<br>* To provide high-flow nasal cannula in the immediate postoperative period after lung resection surgery as compared to conventional face-mask therapy, in a randomized sequence, for 30 minutes.<br>* Other names: Airvo 2, Fisher&Paykel.;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Respiratory drive | Respiratory drive will be assessed as maximal EMG activity during each respiratory cycle (peak EAdi of the NAVA catheter) | Mean or median EAdi for both conditions (30 minutes each) | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Thickening fraction of the right hemidiaphragm | Diaphragm thickness will be assessed at end-inspiration and end-expiration and presented as percentage of change. | An ultrasound will be performed 25 minutes after starting each study condition | 
| Diaphragmatic excursion | Diaphragmatic excursion will be assessed on each side and measured in millimeters | An ultrasound will be performed 25 minutes after starting each study condition | 
| Oxygenation | Arterial oxygen pressure to inspired oxygen fraction ratio (PF ratio) | An arterial blood sample will be obtained at the end (30 min) of each study condition | 
| Ventilation | Arterial pressure of carbon dioxide (CO2) | An arterial blood sample will be obtained at the end (30 min) of each study condition | 
| Dyspnea | The presence of dyspnea will be assessed by a visual analog scale (VAS). This scale presents a range of discrete values from 0 to 10; with lower values indicating less symptoms and higher values indicating more symptoms. Participants will subjectively rate their own level of dyspnea. | Dyspnea presence by VAS will be assessed at the 30-minute mark of each condition (end of each condition) and will evaluate dyspnea for the whole condition (30 minutes). |