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VIASYS HEALTHCARE INTERNATIONAL. Oslo, November 2006 High Frequency Oscillation. SensorMedics 3100. Putting things into perspective:. Most patients do not die of respiratory insufficiency. Stapleton et al. Crit Care Med 2005;128:525-532. However:.
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Oslo, November 2006High Frequency Oscillation SensorMedics 3100
Putting things into perspective: • Most patients do not die of respiratory insufficiency
However: • MOF may be the result of inadequate mechanical ventilation • VILI, biotrauma
Alveolar interdepedence, shear stress Mead et al. J Appl Physiol 1970: 28:596 - 608
Capillary Leak Fu Z, JAP 1992; 73:123
Overstretching • Volutrauma • Caused by cycling of the lung (change in surface area), independent of pressure required • Alters Surfactant function • Promotes Atelectasis • Increases capillary leak of proteinacious material • Promotes Atelectasis Dreyfuss,D ARRD 1988;137:1159
So, how to avoid iatrogenic injury and interrupt pulmonary injury sequence? • Try to avoid: • Shear • Overdistention • Cyclic stretch • biotrauma
So, how to avoid iatrogenic injury and interrupt pulmonary injury sequence? • Use of small tidal volumes
Clinical studies • Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress SyndromeThe Acute Respiratory Distress Syndrome Network. 2000;342:1301-08 • Effect of a Protective-Ventilation Strategy on Mortality in the Acute Respiratory Distress Syndrome Amato, et al.1998;338:347-54
So, how to avoid iatrogenic injury and interrupt pulmonary injury sequence? • Use of small tidal volumes • Avoid cyclic closure/reexpansion
So, how to avoid iatrogenic injury and interrupt pulmonary injury sequence? • Use of small tidal volumes • Avoid cyclic closure/reexpansion • Open up the lung, recruitment
Pig model 35 kg with ARDS PCV PEEP : 15 cm H2O MAP : 23 cm H2O PIP : 31 cm H2O Optimized longvolume : “safe window” • Overdistension • Edema fluid accumulation • Surfactant degradation • High oxygen exposure • Mechanical disruption Zoneof Overdistention Injury “Safe” Window Volume Zone of Derecruitment and Atelectasis • Derecruitment, Atelectasis • Repeated closure / re-expansion • Stimulation inflammatory response • Inhibition surfactant • Local hypoxemia • Compensatory overexpansion Injury Pressure
High Frequency Ventilation in Adults: • HFJV : High Frequency Jet Ventilation • HFOV : High Frequency Oscillating Ventilation
HV Jet Ventilator in ARDS: • Delivers short pulses of pressurized gas in ET tube • Advantages: • Disadvantages - Simple divices - Improvement of gas exchange - Need for combination CV/HFJV - Need for canula / modified ET tube - Passive exhalation - Air trapping / Airway strech - Humidification problems
HFJV HFOV Mechanism Frequency Exhalation CDP Control Humidity ET Tube Oscillator Jet, Set back Jet 3-15 HZ (180-900) 1-10 HZ (60-600) Active Passive Direct setting Gas trapping by incr. Frequency and set Peep Standard Humidifier Vaporizer, Nebulizer Humidity Entrainment HFOV-HFJV what is different ? Standard ETT Modified ETT
Approaches to oxygenation and ventilation PaO2PaCO2 Paw alv. ventilation CMVPEEP / PIP / IT f / TV HFOV CDP f / amplitude
Sensormedics 3100 HFO Ventilator 2 Principles: 1) Oxygenation (O2) CPAP 2) Ventilation (CO2) Oscillation
HFOV Principle 1: CDP Adjust Valve Oscillator ET Tube Patient BIAS Flow • Increase lung volume with a “super CPAP system” • Create a Continuous Distending Pressure (CDP /MAP)
Expiration = ACTIVE Air trapping • Disconnection Oxygenation from Ventilation Principle 2: CDP Adjust Valve Oscillator ET Tube Patient BIAS Flow • Decrease Tidal Volume to equal or below physiological dead space • and increase frequency (0.1 – 2ml/Kg)
HFOV Principle:Pressure curves CMV / HFOV Injury Injury
CMV Instable Aveoli versus HFOV Carney et al. Crit Care Med 2005;33:S122-S128
Pulmonary Injury Sequence: • If we cannot prevent the injury sequence , then the target goal is to interrupt the sequence of events ! • High Frequency Oscillation does not reverse injury, but will interrupt the progression of injury
Clinical Applications • Pediatric/Adult • ARDS • Pneumonia • (Bronchiolitis) • Thoracic Trauma • Smoke Inhalation • Blood Aspiration • > 24 hrs. > 60% FiO2 • Ped./Adult Air leaks • Interstitial Emphysema • Subc. Emphysema • Pneumothorax • Pneumoperitoneum • Pneumomediastinum • Post-op Lung Surgery • Post-op Heart Surgery • Lung Surgery