Autonomic tone in medical intensive care patients receiving mechanical ventilation and during a CPAP weaning trial.

Mechanical ventilator support and the resumption of spontaneous ventilation or weaning create significant alterations in alveolar and intrathoracic pressure that influence thoracic blood volume and flow. Compensatory autonomic tone alterations occur to ensure adequate tissue oxygen delivery, but autonomic responses may produce cardiovascular dysfunction with subsequent weaning failure. The authors describe autonomic responses of critically ill patients (n = 43) during a 24-hr period of mechanical ventilatory support and during the 24 hr that included their initial spontaneous breathing trial using continuous positive airway pressure.

Hemodynamic changes during discontinuation of mechanical ventilation in medical intensive care unit patients.

Background: Cardiac dysfunction can prevent successful discontinuation of mechanical ventilation. Critically ill patients may have undetected cardiac disease, and cardiac dysfunction can be produced or exacerbated by underlying pathophysiology.

Objective: To describe and compare hemodynamic function and cardiac rhythm during baseline mechanical ventilation with function and rhythm during a trial of continuous positive airway pressure in medical intensive care patients.