Background

Patient-ventilator asynchrony during assisted mechanical ventilation (MV) is a serious problem associated with prolonged MV, intensive care unit hospitalization and increased mortality in people. A common way to detect asynchronies is by examining ventilator waveforms.

Case Presentation

A 9-year-old female Rottweiler dog (body weight 38 kg) was presented 2 days after cervical (C2–C3) hemilaminectomy for subarachnoid cyst removal with tetraparesis and hypoventilation (PaCO₂ 51 mm Hg/PaO₂ 67 mm Hg) requiring MV. Pressure controlled ventilation (PCV) was initiated and total intravenous anaesthesia with propofol and dexmedetomidine was started. Emergency MRI showed a cervical extradural haematoma requiring spinal cord decompressive surgery. Weaning from MV, 24 hours post-surgery, was unsuccessful and on day 3 a tracheostomy was performed to allow sedative de-escalation and long-term ventilation management. Once anesthetics were discontinued, consciousness and spontaneous feeding returned. Pressure regulated volume control (PRVC) ventilation was set (tidal volume 420 ml, inspiratory flow trigger 2 l/min). Flow and pressure waveforms analysis showed an auto trigger of 10 l/min due to cardiac oscillations which caused tachypnea. Therefore, asynchrony was corrected by increasing the flow trigger from 2 to 11 l/min. From day 3 to 6, PRVC and pressure support ventilation (PSV) modes (with expiratory trigger optimized from 15 to 40%) were interchanged ensuring protective ventilation and avoiding respiratory fatigue. From day 6, PSV and gradually longer periods of invasive CPAP (up to 4 hours) were used and weaning was possible on day 11. The dog was discharged after 1 month with completely recovery of ambulatory functions.

New/Unique Information

PRVC is a form of an adaptive pressure assist control ventilation in which tidal volume is used as a feedback control to continuously adjust the pressure limit. This ventilation mode allows patient to start the breath supported by the ventilator avoiding an excessive work of breathing. Auto trigger is a frequent but often unrecognized patient-ventilator asynchrony, associated with ventilator induced diaphragm dysfunction and prolonged ventilation weaning. In the case presented, flow and pressure waveforms were essential to detect asynchronies and optimize the ventilation.

Disclosures

No disclosures to report.