Dysfonction diaphragmatique après chirurgie cardiaque

Phrenic dysfunction following cardiac surgery is very frequent but most patients remain asymptomatic and can be weaned from the ventilator without any difficulty. Indeed, even in case of complete hemidiaphragmatic paralysis, the contralateral hemidiaphragm may generate enough transdiaphragmatic pressure to allow weaning from the ventilator. However, in some patients, bilateral diaphragmatic dysfunction is responsible for respiratory failure with prolonged ventilation, ventilator-acquired pneumonia and high risk of sudden respiratory arrest when breathing spontaneously. Although these severe forms of diaphragmatic dysfunction are infrequent in the whole population of cardiac surgery patients, it is often encountered in the subset of patients requiring prolonged ventilation after surgery. To the clinician facing such patients, the challenge is to determine whether the patient has a diaphragmatic dysfunction severe enough to account for the weaning failure. Diaphragmatic ultrasonography showed its ability to rule out such severe forms when showing that at last one of the hemidiaphragm excursion is above 25 mm. Transdiaphragmatic pressure measurements remain the reference technique to diagnose severe diaphragmatic dysfunction in the ICU setting evidencing the functional impairment associated with diaphragmatic failure. In patients with severe diaphragmatic dysfunction, prolonged invasive mechanical ventilation is required while waiting for the recovery of the diaphragmatic function that occurs in weeks to months.