08/14/061 HFOV vs. Conventional Ventilation Latoya Robinson Julie Ordones Joshua Globke Matthew Heaton

08/14/062 Introduction We are students attending Kingwood College researching the safety and hazardous effects of High Frequency Oscillatory Ventilation (HFOV) vs. Conventional Mechanical Ventilation (CV) for adult patients with ARDS.

08/14/063 Hypothesis We predict that adults with ARDS that are placed on HFOV will have a lower mortality rate as opposed to ARDS patients left on CV.

08/14/064 Background High frequency was accidentally discovered by anesthetist P. Lunkenheimer in (5) In 1980, Bohn also using HFOV discovered excellent gas exchange in normal dogs with the use of oscillatory ventilation.(1)

08/14/065 Definition: What is HFOV? HFOV “employs the delivery of small tidal volumes ”called Amplitude at frequencies or Hertz of greater than one fifty beats per minute; usually equal or less than the dead space.(3) Lungs are kept open to a constant airway pressure via a mean pressure adjustment system.(3) HFOV improves gas exchange and V/Q matching, increases alveolar recruitment, and enables stable lung inflation by use of a rapid flow pattern, and constant airway pressures(3)

08/14/066 Indications for HFOV Severe blunt trauma to the thoracic cavity Persistent Pulmonary Hypertension of the Newborn Pneumothoracies and Congenital Diaphragmatic Hernias Risks of volutrauma and barotraumas with conventional ventilator settings that are very high

08/14/067 Hazards of HFOV Over distension Tension Pneumothorax Lung collapse Difficulty maintaining ET tube position Difficulty assessing breath sounds due to the loud noise from the HFOV

08/14/068 Methodology Population In all 3 studies the population was selected as a pt with ARDS and the following criteria: Adult >35 kg P/F ratio of <200 CXR w/ bilateral pulmonary infiltrates No atrial hypertension No Hx of COPD

08/14/069 Methodology Equipment Used All 3 studies in the HFOV trial used the Sensormedics 3100B oscillatory ventilator. The conventional mechanical ventilators used in one of the studies included the Dräger EVITA4, Lübeck, and the Siemens Servo300B. The other studies did not list which vents used.

Methodology Testing Methods 1 st Study In the first study, within the CV group, ventilators were initially set on a time cycled pressure controlled mode with a respiratory rate to achieve low tidal volumes up to 60 bpm. The maximum peak pressure was limited to 40 cmH2O. PEEP was advocated up to 15cmH2O and an I: E Ratio up to 2:1 could be used to achieve adequate oxygenation. In order to minimize the inspiratory pressures, an arterial PH > 7.20 was acceptable regardless of the level of PaCO2.

Methodology Testing Methods 1 st Study Patients in the HFOV group of Study 1 were ventilated with a Sensor Medics 3100 B ventilator using a high lung volume strategy with continuous distending pressure at 5 cm H2O higher than mean airway pressure on CV and then adjusted to receive the most favorable lung volume. Initially CDP was increased until an O2 saturation of >95% was achieved; and not decreased until a FiO2 of < 60% was possible. The frequency was initially set at 5 Hz with an inspiratory time of.33. Delta P was adjusted according to PaCO2 and chest wall vibrations.

Methodology Testing Methods 2 nd Study In Study 2, ventilators were initially set on a tidal volume of 6-10 ml/kg with a RR to maintain a Ph of >7.15, and an I-time also of.33. Adjustments were made accordingly, for ventilation, an increase in RR and Vt, and for oxygenation, an increase in PEEP, FiO2, and or an increase in inspiratory time. When weaning adjustments were made they included a decrease in FiO2 and PEEP and converting to PS for breathing trials.

Methodology Testing Methods 2 nd Study In Study 2, the initial settings for the HFOV were RR- 5 Hz, mPaw – CV + 5, and an I time of 33%.Once deemed appropriate a patient was changed to conventional ventilation once the FiO2 was reduced to less than.50 and mPaw was weaned to 24 cm H2O with an SaO2 of 88% or greater. For transition, the conventional ventilator was set in pressure-control mode with an adjusted PIP to achieve a delivered Vt of 6-10 ml/kg of actual body weight, PEEP of 10 cm H2O, and an Inspiratory time of 50%. Adjustments were similar to those made in conventional ventilation.

Methodology Testing Methods 3 rd Study In study 3 during the HFOV trial, the initial settings used were as follows; FIO2 of 1.0, continuous distending pressure (CDP) 5 cmH2O above the last measured mean airway pressure on conventional ventilation, inspiratory time at 33% of total respiratory cycle; oscillatory frequency at 5 Hz; bias flow at 30 l/min; oscillatory amplitude (P) scaled relative to entry PaCO2.

08/14/06 Discussion: Limitations for all three of our studies included small populations, concurrent studies, and not listing the brands of conventional ventilators.

08/14/0616 Statistics: Conventional Ventilators Raw Data Total number of Subjects:

08/14/0617 Statistics: Mean Data CV Mean MAP= 21 cmH2O Mean O2 Index= 21 Mean CO2= 50 torr SD MAP= 21.3 cmH2O SD O2 Index= 4.5 SD CO2= 7.0 torr

08/14/06 Statistics: Raw Data HFOV Total number of Subjects: 154

08/14/06 Statistics: Mean Data HFOV Mean MAP= 22 cmH2O Mean O2 Index= 25 Mean CO2= 51 torr SD MAP= 22 cmH2O SD O2 Index= 4.9 SD CO2= 7.11 torr

Conclusions In studies 1 & 2, MAP, O2 Index, and CO2 were very similar. We found that the mean MAP in the CV groups were less than that of the HFOV group. Also, the mean O2 Index was less in the CV group than in the HFOV group. The CO2 mean values correlated in both groups. In the HFOV group, in study 1:43% (16/37) died, in study 2: 37% (28/75) died, we were not able to obtain the mortality rates in the 3 rd study. In the CV group for study 1: 30% (8/24) died, and in study 2: 52% (38/73) died.

08/14/06 Conclusion Overall we discovered that HFOV is an effective option for treating ARDS patients because it actively recruits alveoli while keeping MAP airway pressures to a minimal. It was evident from our studies that HFOV is most effective in reducing the mortality rate when started at the earliest possible time.

08/14/06 References Study 1 1. Bryan, A. C. & Cox, P. N. (1999). History of high frequency oscillation. Schweiz Med Wochenschr, 129, High Frequency Oscillatory Ventilation. (n.d.) Retrieved July 10, 2006 from Higginson, R., RN BN (Sept. 2002). High Frequency Oscillatory Ventilation. CHEST Medicine Online retrieved July , from

08/14/06 References Study 2 Derdak, S. (Nov. 2001). High frequency oscillatory ventilation: clinical management strategies for adult patients. Retrieved July 20, 2006, from Critical_Care/CCRs/CCR-Derdak.pdf

08/14/06 References Study 3 Matthias David1, Norbert Weiler2, Wolfgang Heinrichs1, Markus Neumann1, Thilo Joost1, Klaus Markstaller1 and Balthasar Eberle1 (1) Department of Anesthesiology, Johannes Gutenberg University, Langenbeckstrasse 1, Mainz, Germany (2) Department of Anesthesiology and Intensive Care Medicine, Christian Albrecht University, Schwanenweg 21, Kiel, Germany