Respiratory Variability and Dyspnea During Spontaneous Breathing Trial

In intensive care unit, dyspnea, the distressing and fearful awareness of breathing, is frequent and harmful. To be treated, dyspnea must be detected and quantified, which is impossible in approximately 50% of patients receiving invasive mechanical ventilation. However, these non-communicative patients are exposed to the same risk factors for dyspnea as communicative patients and the impossibility to communicate a suffering increases its traumatic impact. In addition, simple therapeutic means, such as optimizing the settings of the ventilator, can significantly alleviate or even eliminate dyspnea. It is therefore particularly important to be able to detect and quantify it effectively. The Mechanical Ventilation - Respiratory Distress Observation Scale (MV-RDOS) is an observational dyspnea scale that bypasses patient involvement and represents a promising tool in the detection of dyspnea in non-communicative patients. However, its use is partly based on the observation of the facial expression of fear or the abdominal paradox, the assessment of which remains subjective. The analysis of ventilatory variability, which reflects the load-capacity balance of the respiratory system, could provide an alternative to detect dyspnea in these patients. The investigators are therefore going to measure the ventilatory variability using the thoracic motion signals obtained with a force sensor integrated in a chest strap and the ventilatory flows at airways in patients receiving invasive mechanical ventilation during a spontaneous breathing trial and compare the indices of ventilatory variability with the dyspnea visual analog scale in communicative patients and with the MV-RDOS in all patients (communicative and non-communicative).

Inclusion Criteria:Invasive mechanical ventilation > 48h,Readiness-to-wean ability: ability defined by all of the following criteria: effective cough, no excessive tracheo-bronchial secretions, resolution of the disease that prompted the intubation, heart rate ≤ 140/min, pressure systolic blood pressure between 90 and 160 mmHg, no or very low dose of amines, SpO2 > 90% in 40% FiO2 (or PaO2/FiO2 > 150), positive expiratory pressure < 8 cmH2O, respiratory rate ≤ 35/min, tidal volume > 5ml/kg of theoretical body weight, respiratory rate / tidal volume ratio < 105 cycles/min/LDecision by the clinician in charge of the patient to perform a SBT,Patient or close consent obtained,Person affiliated to a Social Security scheme or beneficiary (excluding AME).Exclusion Criteria:Minor patient,Pregnant or breastfeeding woman,Agitation/sedation: RASS > 2 or < 2,Post-operative thoracic or abdominal surgery,Chest skin lesion contraindicating the placement of a chest strap,Person under legal protection (guardianship, curators), safeguarded by justice.