2001 OPEN FORUM Abstracts
HIGHFREQUENCY OSCILLATORY VENTILATION IN ADULTS WITH ARDS
Dr.Jeffrey Miller, MICU Medical Director, Pulmonologist, Internist, Aultman Hospital,Canton, Ohio / Dr. Robert Miller, Medical Director of Respiratory Care,Pulmonologist, Internist, Aultman Hospital, Canton, Ohio / Dr. Eyad Nashawati,Pulmonologist, Internist, Sleep Specialist, Aultman Hospital, Canton, Ohio /Thomas J. Paris, RRT, RCP, Clinical Specialist, Aultman Hospital, Canton, Ohio/ Douglas Lauby, RRT, RCP, Respiratory Care Manager, Aultman Hospital, Canton,Ohio / Thomas F. Opeka, RRT, RCP, Clinical Specialist, Aultman Hospital, Canton,Ohio / Timothy Larson, RRT, RCP, Perinatal / Pediatric Specialist, Aultman Hospital,Canton, Ohio.
High Frequency OscillatoryVentilation (HFOV) has been in use for a number of years in neonates for thetreatment of Respiratory Distress Syndrome (RDS) mostly due to a loss of surfactantin the lungs. In Adult Respiratory Distress Syndrome (ARDS), adults also losesurfactant, causing decreased tidal volume (Vt), decreased airway distentionand increased airway resistance, resulting in volutrauma. HFOV provides a consistentmean airway pressure (MAP) which in turn recruits alveoli / lung volume thatwas either infiltrated and/or had become atelectatic. HFOV is described as arespiratory rate of > 150 bpm. HFOV should be used on adult patients whenconventional volume ventilation and/or pressure control ventilation have becomeinsufficient enough to maintain adequate oxygenation and carbon dioxide elimination,or peak inspiratory pressures > 45cmH2O and MAP > 22cmH2O in either modeof ventilation. Criteria for HFOV include an Oxygen Index (OI) > 13, in twoarterial blood gases (ABG?s) within a six hour period (OI = 100 x FiO2 x MAP/PaO2).Place an arterial line and CVP for monitoring pressures and serial ABG?s. Maintaina normal Mean Arterial Pressure (minimum of 60mmHg) and CVP should be 15-20mmHg.Starting parameters for HFOV are as follows: FiO2 at 100%, MAP started at 4-8cmH2O> MAP on CMV mode of conventional ventilation, and increased by incrementsof 1-2cmH2O to achieve optimal lung volume. Optimal lung volume is reached oncethere is an increase in SpO2 enabling a decrease in the FiO2, and a CXR revealsthe right hemi-diaphragm at the T9-9.5 level with clear lung fields. Flowrateat max flow of 40 lpm. Frequency starts at 6 Hertz (Hz) where 1Hz = 60bpm. TheDelta-P or power setting is started at 4.0 and increased until the chest vibratesdown to the level of the groin. Percent inspiratory time is started at 33%.The amplitude (which is controlled by Delta-P) can be increased to improve ventilation(CO2 removal) in increments of 5cmH2O. Should the PaCO2 still be high afterthe amplitude is increased by 20cmH2O, the frequency can be decreased by 1Hz.The goal is to use the highest frequency possible. Slightly deflating the ETTcuff to provide a leak may also decrease PaCO2. The percent inspiratory timeshould be kept at 33%. However, it may be increased only to decrease PaCO2 orincrease PaO2 when Delta-P is maximized and frequency is minimized to 3Hz. TheFiO2 can be weaned for arterial saturation > 88%, and once the FiO2 is 40-60%the MAP can be decreased in increments of 1cmH2O. The amplitude is weaned byincrements of 5cmH2O for PaCO2 < desired goal. Failure criteria include theinability to decrease the FiO2 by 10% within 24hrs. of institution, or failureto improve or maintain adequate ventilation with PaCO2 < 100mmHg and thepH > 7.15. An OI < 42 at 24hrs. of instituting HFOV is a good indicatorof a positive response. Parameters for conversion from HFOV to CMV are: FiO2< 40%, MAP 15-20cmH2O, and amplitude < 40cmH2O. The success rate for theuse of HFOV on adults at Aultman Hospital has been 85% with the key elementbeing early intervention.