The ventilatory strategy to minimize expiratory flow rate in ventilated patients with chronic obstructive pulmonary disease

Abstract

Although the pathophysiology of chronic obstructive pulmonary disease (COPD) is multifactorial, central airway collapse is reported to have a great impact on symptom severity. In COPD patients, positive pressure formed by hyperinflated lungs compressing the tracheal wall and negative changes in intratracheal static pressure due to rapid expiratory flow velocity at the beginning of expiration collapse the trachea. This phenomenon can be explained by fluid dynamics theory. Our hypothesis is that ventila-tory strategy focusing on minimization of expiratory flow rate may be advantageous for patients receiving mechanical ventilation for COPD. If appropriate counter pressure could be applied on exhalation, patients may be able to exhale slowly with reduced expiratory flow rates which may prevent negative changes of the intratracheal static pressure. We devised a new conceptual ventilation mode “minimized expiratory flow rate ventilation (MExV)” which applies regulated counter pressure on exhalation. The conceptual wave-forms of “minimized expiratory flow rate ventilation” including flow rate, volume, and airway pressure are shown, compared with typical waveforms of the conventional ventilation modes.