The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

A BENCH EVALUATION OF TIDAL VOLUME DELIVERY THROUGH VARIOUS NASAL INTERFACES USING NON-INVASSIVE PERCUSSIVE HIGH FREQUENCY NASAL CPAP.

Charles J. Hoydu1, Rick Carter1, Kevin Crezee1, Donald M. Null2; 1Respiratory Care Services, Primary ChildrenÂ’s Medical Center, Salt Lake City, UT; 2Department of Pediatrics, School of Medicine, University of Utah, Salt Lake City, UT

Background: Recently, studies (1) have suggested that high frequency percussive ventilation through endotracheal tubes placed in the nasopharyngeal area of premature lambs may prevent the development of bronchopulmonary dysplasia. As a result of this finding, we believed it was important to investigate this method of ventilation in more detail in order to enhance future research. Therefore, in order begin to objectify this method of ventilation, we developed methods to measure tidal volumes, minute ventilation, peak airway pressures, and PEEP in a simulated lung model. Method: The Percussionaire Sinusoidal Bronchotron with Turbohead Phasitron and Hudson Nasal CPAP Prongs (Sizes 0-5) and endotracheal tubes(ET) 2.5 mm and 3.0 mm were attached to a SmartLung Infant test lung. The lung was set at a compliance of 1 ml/mbar and resistance at 5 mbar/L/s and then placed in the Vitaltrends Technology Neonatal Vt 1000 Plethysmograph. The Neonatal Plethysmograph was calibrated and the Bronchotron set at 30psi and oscillatory CPAP and pulsatile flow rate were set to achieve various mean airway pressures to investigate the effect on tidal volume (Vt) and minute ventilation (VE). The rate on the Bronchotron was limited to approximately 5 Hertz which was the limit for the Vt 1000 to produce accurate readings. The inspiratory time on the conventional side of the Bronchotron was placed at the lowest level (short time) and the expiratory dial placed at the highest level (long time) as to minimize conventional breaths (VtH). Ventilator frequency (279-282) was kept constant while operational pressure (30-32 psi) and the oscillatory CPAP controller were adjusted to achieve targeted mean airway pressures (MAP) of 6, 8, 10 and 12 cmH2O. At these various settings the Vt and VE were determined at the various prong and ET-tube sizes. Operational pressure was only adjusted if the oscillatory CPAP control reached the maximum level and could not meet the targeted MAP. Results: We found that increasing the prong size and endotracheal tube diameter dramatically increased both the mean tidal volume and mean minute ventilation (see attached table). Conclusion: As expected the endotracheal tubes delivered the lowest minute ventilation at the test settings because of their small diameter and longer length. Also, tidal volume and minute ventilation increased with prong size diameter at each test setting (see attached table). Sponsored Research - None