The feasibility of non-invasive ventilation using portable transport ventilators

Purpose: To evaluate the feasibility of non-invasive ventilation of patients being transported using a commonly available transport ventilator. Methods: We devised a system consisting of oxygen fed into a blender then into a Impact Univent® 750 ventilator. The patient module on the ventilator was then connected to a variety of non-invasive ventilator masks, including a standard anesthesia mask, a Hans-Rudolph® full face mask, a Airsep® nasal mask, and standard nasal pillows. A nebulizer or MDI chamber was placed in line between the ventilator circuit and the facemask. A Wright spirometer was connected to the ventilator circuit, as could a PEEP valve. These masks were tried on three volunteers with chronic obstructive pulmonary disease who were exercising as part of a pulmonary rehabilitation program. Results: The commonly available transport ventilators approved for air-transport typically do not have a pressure support mode available on them. However we found that adequate ventilation is possible in either the CMV or the SIMV modes. Patients were observed over a wide range of tidal volumes (200-1000ccs/breath) and respiratory rates (6-20 BPM) and appeared to synchronize with the ventilator well. As these ventilators are pressure demand triggered it is important to minimize leaks during inhalation as the entrainment of air around the mask can increase the breathing work required to trigger the ventilator. Higher gas flows through the nebulizer made it more difficult for the patient to trigger the ventilator as well. This could be circumvented by using the nasal mask and oral nebulizer or using an in line MDI chamber. It is feasible to follow exhaled tidal volume on patients supported with the Impact Univent 750 by placing a Wright spirometer in-fine with the exhalatory port. Patients reported the greatest degree of comfort using the Hans Rudolph® full face mask. Conclusions: Transport of selected patients with respiratory failure using non-invasive ventilation with commonly available equipment is feasible. Minimizing inspiratory leak is important to maximize patient-ventilator synchrony. Clinical Implications: It should be possible to transport patients with respiratory failure with support by non-invasive ventilation techniques.