Device for exhaled gas monitoring during high frequency ventilation

Children's Hospital Boston
posted on 12/19/2011

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The HAAD is a device to enable flow, carbon dioxide (CO2), volumetric carbon dioxide (VCO2) and volumetric oxygen (VO2) monitoring as well as metabolic assessment through the application of an indirect calorimeter in patients undergoing High frequency oscillatory ventilation (HFOV or 'hifi'). HFOV is a mode of ventilation that employs a relatively high mean airway pressure upon which pressure oscillations are superimposed at rates from 3-15Hz. HFOV is used in patients with respiratory distress syndrome, acute lung injury or acute respiratory failure to maintain end-expiratory lung volume. HFOV is often applied when conventional ventilation is unable to provide adequate oxygenation and ventilation.|| Current bedside technology (which is used during conventional ventilation) was not developed to measure changes in flow and CO2 as rapidly as occurs during HFOV and therefore is unable to be used presently. VCO2 monitoring during HFOV has not previously been demonstrated. Rather than adapt the technology to the flow, the HAAD employs a simple solution that essentially adapts the exhaled gas flow during high-frequency oscillatory ventilation to the technology. The HAAD works by attenuating the flow/pressure amplitude of the breaths that are exhaled during HFOV. The net result is a significant reduction in the variability of exhaled gas flow that enables that application of flow- and CO2 monitoring to HFOV while not affecting the function of the HFOV.