Brain-lung Interaction During Acute Respiratory Failure

Acute hypoxemic de novo respiratory failure (AHRF) is a common cause of admission to the intensive care unit (ICU). Its main cause is community-acquired pneumonia. Prevention of intubation relies, among other things, on high-flow nasal canulae (HFNC). However, approximately 40% of patients are intubated despite HFNC.

Our team has developed measurements derived from electroencephalograms (EEG) and near-infrared spectroscopy (NIRS) that enable the study of brain-ventilation interactions. To date, these tools have been studied exclusively in intubated patients. the investigators now wish to study them in non-intubated patients.

The objective of this study is to investigate the relationship between the brain and lungs in adult patients admitted to the intensive care unit for acute hypoxemic respiratory failure and for whom the attending physician has decided to initiate HFNC.

Before and one hour after the introduction of HFNC, electroencephalogram (EEG), near-infrared spectroscopy (NIRS), and electromyogram (EMG) of the Scalen muscles will be collected.

From these recordings, the following variables will be collected: 1) The density of the gamma (30-100 Hz), beta (13-30 Hz), alpha (8-12 Hz), theta (4-8 Hz), and delta (0.5-4 Hz) frequency spectrum of the EEG in each of the following right and left cortical regions: medial region of the prefrontal cortex, anterior region of the cingulate gyrus, posterior region of the cingulate gyrus, insula, somatosensory cortex, angular gyrus, lateral prefrontal cortex, and supplementary motor area; 2) Connectivity between these regions for each frequency spectrum; 3) Pre-inspiratory potential; 4) Rieman classifier; 5) Coherence and Granger causality between each frequency spectrum and the scalene muscles EMG.

These variables will be compared before and 1 hour after initiation of HFNC and between patients who will be intubated because of HFNC failure and those who will not.

Inclusion criteria

• - Age ≥ 18 years
• Admitted to the intensive care within the last 48 hours
• De novo acute hypoxemic respiratory failure with an indication for high-flow nasal cannula (HFNC), defined by the combination of the following three criteria:

• Tachypnea > 25 breaths/min or labored breathing
• PaO2 (partial pressure of oxygen ) /FiO2 ( fraction of inspired oxygen ) ≤ 200 mmHg
• Unilateral or bilateral alveolar opacities on chest X-ray
• Decision by the attending physician to initiate HFNC treatment
• After information, the patient or next of kind did not refuse to participate (according to the French law, written informed consent is waived)

Exclusion criteria

• - Exacerbation of an underlying chronic respiratory disease
• Acute cardiogenic pulmonary edema indicating non-invasive ventilation (NIV)
• Hypercapnia > 45 mmHg indicating NIV
• Glasgow Coma Scale < 13
• Imminent intubation
• Underlying central neurological disease likely to alter EEG signals
• Pregnancy or breastfeeding
• Lack of health insurance coverage
• Patient under legal protection