Incidence of Dyssynchronies in Early ARDS

Measurements

Physiological measurements Airway pressure, esophageal pressure, electrical activity of the diaphragm and flow

1. Flow and airway pressure signal will be recorded from the ventilators by connecting the ventilator to a laptop computer if possible. Recording these data simultaneously with esophageal pressure or electrical activity of the diaphragm (see later in protocol for details) could be technically unfeasible. In this case, a flow sensor and an additional port for pressure measurement will be connected to the endotracheal tube proximal to the Y connector (without interfering with patient's breathing). Both, flow sensor and pressure port will be connected to differential pressure transducers respectively. Signals will be acquired with at least 100 Hz sampling.
2. In centers used to perform esophageal pressure measurements, an esophageal catheter will be inserted as per usual clinical practice, checked for accuracy with an occlusion test, and connected to a 3 ways stopcock and a pressure transducer. The occlusion test will be recorded and performed before any new recordings. Any ventilator can be used if an esophageal pressure is used.
3. If available, in centers used to record or monitor the electrical activity of the diaphragm, instead of an esophageal catheter, the electrical activity of the diaphragm will be provided by a catheter dedicated to the monitoring of the electrical activity of the diaphragm, or EaDi, on a Servo-I or Servo-U ventilator (Maquet©, Lund, Sweden). This catheter is formally designed to be used for a specific mode of ventilation called Neurally Adjusted Ventilatory Assist (NAVA) but here will be used for monitoring purposes only (NAVA catheter). In such cases a specific software (Servotracker, Maquet) may be used to record all signals from the ventilator.
4. In case the patient has been enrolled but the esophageal catheter cannot be placed or is contraindicated, the recordings will be limited to airway pressure and flow. Each centre should have a minimum of 5 patients with esophageal catheter or electrical activity recording.
5. As an ancillary study, in a subgroup of patients, simplified recordings will be obtained only flow and airway pressure signals will be performed continuously directly taken from the ventilator by connecting the ventilator to a laptop computer equipped with a special software for off line analysis (Better Care ©, Sabadell, Spain).
6. Occlusion pressure (or pressure at 0.1 sec, P0.1) as an index of respiratory drive. In patients triggering the ventilator, the P0.1 will be analyzed from the tracings. The only condition to have reliable measurements is to use a pressure triggering, not a flow triggering.

As an ancillary study, in a subgroup of patients, a simplified extended polysomnography recording will be performed during the first 7 days after inclusion using a home polysomnography device (Prodigy, CerebraHealth ©, Canada) equipped with 2 frontal EEG a reference electrode to the mastoid, EMG, and electrooculogram.

Data collection

At the beginning of the recordings, ventilatory settings will be collected: ventilator brand, mode of ventilation and settings including: FiO2, PEEP, set and real tidal volume (or pressure), set and real respiratory rate, maximum inspiratory flow, inspiratory time, Glasgow coma scale and Richmond Agitation Sedation Scale (RASS) or Riker Sedation Agitation Scale (SAS). Any medications used at the day of the measurement and before will be collected especially neuromuscular blocking agents, sedatives (brands and doses), opiates and vasopressors including dose, duration of the treatment and date of last use. Investigators will also collect clinical characteristics of the patients (SAPS and SOFA at ICU admission and at the day of the recording, main ARDS or AHRF etiology and risk factors, age, gender, weight, height, days of mechanical ventilation, patient's position -supine vs prone-, kidney and liver function). Other comorbidities will be recorded, with special emphasis in the ones that could affect the incidence of the studied phenomenon, such as: COPD, lung transplant or any neuromuscular condition that could affect the respiratory drive or respiratory muscle function.

Patients will be followed up to get the total duration of mechanical ventilation, ICU length of stay, day of the first weaning attempt, day of tracheotomy if any, status at ICU discharge (alive or death) and at hospital discharge and at day 60.