HFJV

1. HFJV Introduction to HFJV

2. MONITOR: displays patient and machine pressures • ALARMS: indicate potentially hazardous conditions • CONTROLS: regulates the Rate, PIP and On-Time of gas flowing to the patient • HUMIDIFIER: controls and monitors the temperature and humidification of the gas flowing through the humidifier and circuit • PATIENT BOX: makes and monitors the breaths delivered to the patient Overview of HFJV • The Jet is a microprocessor-controlled infant ventilator capable of delivering and monitoring between 240 and 660 heated, humidified breaths per minute. • The Jet is composed of 5 subsystems

3. Two Separate Microprocessors • One controls the valves and other components that produce and monitor ventilation and pressure • One controls and monitors humidification and temperature

4. PEEP The Role of the Conventional Ventilator • The Conventional Ventilator, when operated in tandem with the Jet, has 3 functions: • Provide fresh gas for a patient’s spontaneous breathing • Provide background IMV breaths to open collapsed alveoli • Regulate PEEP to maintain alveolar recruitment

5. 15 mm opening: provides the standard connection to the conventional ventilator • Jet Port: entrance for high-frequency pulses coming from the Jet • Pressure Monitoring Port: allows distal tip airway pressures to be approximated The LifePort Adapter • The LifePort Adapter allows the Jet and conventional ventilators to be operated in tandem. • The LifePort has 3 main features:

6. Summary • Together, these elements form a system that offers a variety of options for managing patients. • The Jet in tandem with a conventional ventilator allows the best blood gases with the least amount of pressure compared with any other form of mechanical ventilation.

7. HFJV How and Why HFJV Works

8. CO2 CO2 • gas is propelled into the lungs at a high velocity • incoming gas is forced to stream into the airways in a long spike • abundant energy of the "jet stream" also causes the gas to spiral as it flows • gas easily splits into two streams at bifurcations • fresh gas penetrates through the anatomic dead space, compressing much of the CO2 in the dead space against the airway walls

9. Adequate Gas Exchange Using Small Tidal Volumes • This possibility was first illustrated as early as 1915 • Henderson observed the shallow breathing of panting dogs • Dogs could pant indefinitely without becoming hypoxic

10. Convection penetrated smoke deeply through tube Diffusion occurred when flow stopped or slowed

11. Demonstrated Importance of Convection and Diffusion During HFJV • Convection carries fresh gas deeply into the lungs quickly • Once the flow stops, diffusion completes the gas exchange process as usual • The effective or physiologic dead space in the lungs can be reduced to less than the volume of the anatomic dead space • The jet stream is only effective for a relatively short distance and a brief time • Longer distances and times allow for development of turbulent flow • Turbulent flow quickly mixes incoming gas with resident dead space gas

12. Taking Advantage of Convection and Diffusion During HFJV • The best way to maximize the jet-stream effect with a mechanical ventilator is to place the inhalation valve as close to the patient as possible • This is accomplished with HFJV by placing the valve and pressure transducer in the small plastic "patient box" that resides close to the infant's head • Gas flow through the pinch valve is stopped almost as soon as it starts by closing the valve almost as quickly • The abrupt cessation of the incoming HFJV breath also helps prevent the development of turbulence so that a crisp jet stream of fresh gas can penetrate deep into the airways

13. What About Exhalation? • With HFJV, as with conventional mechanical ventilation, inhalation is active or forced, and exhalation is passive. • Using rates that bring in as many as 11 breaths per second, one might be concerned that there is insufficient time for breaths to get back out. • However, two factors allow exhalation to occur relatively easily. • The size of each breath (1-3 mL/kg) is much smaller than usual, and the natural or resonant frequency of the infant lungs is close to the frequency range being used by HFJV. • Thus, the lungs recoil readily during HFJV under almost all conditions.

14. Exhalation with HFJV CO2 CO2 CO2 CO2 • During HFJV, exhaled gas swirls outward around the incoming gas. • The exhaled gas sweeps through the CO2-rich deadspace gas. CO2 CO2 • This action may help evacuate CO2 and enhance ventilation.

15. More on Exhalation • Passive exhalation is the safest way to get gas back out of the lungs. • During HFJV, passive exhalation ensures that mean airway pressure will overestimate mean alveolar pressure. • Pressure drops as gas advances into the lungs on inhalation, and there is not time for the pressure in the alveoli to equilibrate with that in the upper airways because of the short inspiratory time. • Furthermore, the highest pressure during exhalation will be in the alveoli so gas flows naturally toward the trachea during exhalation until the beginning of the next inhalation.

16. Exhalation with HFOV • Active exhalation, as with high-frequency oscillation (HFO), can lead to gas trapping by lowering intraluminal pressure disproportionately below pressure in surrounding alveoli, thereby collapsing more proximal airways before exhalation is complete. • For that reason, users of HFO typically operate at higher mean airway pressures than those used with HFJV. • Elevating the baseline pressure during HFO, "splints" the airways open while gas is actively withdrawn from alveoli.

17. + + + + + + + + pressure = 0 • The highest pressure in the lung during expiration is in the alveoli • Pressure drops as gas flows out the airways + + +

18. CHOKE POINTS may develop when: • airways lack structural strength   • the chest is squeezed   • gas is sucked out of the airway

19. + + + + • The high pressure in the alveoli can overwhelm the airway walls which encase gas at lower pressure + + + + +

20. + PEEP + + + • Back pressure (High PEEP/Paw) may splint open the airway and allow gas to exit +

21. PEEP/Paw and the oscillatory pressure waveform must be raised to overcome gas trapping P time

22. The Role of Conventional Ventilation • The conventional ventilator (CV) during HFJV with the Life Pulse is to enhance oxygenation. • Conventional ventilators can deliver oxygenated gas directly to the alveolar level. • They do this by using relatively long (e.g., 0.5 second) inspiratory times and large tidal volumes (e.g., 7 to 15mL/kg body weight), and they have the capability of controlling end-expiratory pressure. • These are the factors that most readily control PO2.

23. Minimizing The Risks of Conventional Ventilation • Unfortunately, the support from the CV is most closely associated with barotrauma and volutrauma. • Thus, it is useful to minimize these factors by running the conventional ventilator at minimal rates (i.e., from 1 to 3 BPM) and moderate TI’s (i.e., from .25 to .45 sec) while the Jet ventilator is providing the bulk of the ventilation. • Using the conventional ventilator to gradually recruit collapsed alveoli allows the Jet to achieve the best possible blood gases with the lowest possible airway pressures.

24. Technical Capabilities and Clinical Implications of HFJV HFJV

25. Technical Capability Clinical Implication • Minimizes mechanical dead space • Allows use with any conventional ventilator • Provides ability to display approximated intratracheal pressure Uses LifePort Adapter

26. Technical Capability Clinical Implication P < Natural Frequency Natural Frequency > Natural Frequency Best Blood Gases with Least Pressure • Minimizes pressure needed to move gas into the lungs • The ease with which lungs recoil and send gas out in this frequency range lessens the chances of gas trapping that one normally encounters at higher frequencies Operates in the natural frequency range of the lungs

27. Technical Capability Clinical Implication • Introduces inspired gas as a sharp impulse that penetrates through the resident dead space gas Jet valve is located close to patient's airway in the Patient Box • Upper airway leaks (tracheal-esophageal and broncho-pleural fistulae) are bypassed by the momentum of the incoming gas.

28. Technical Capability Clinical Implication • Strain on the cardiopulmonary system (e.g., barotrauma and suppression of hemodynamics) is diminished • Established air leaks, restrictive and/or non-homogenous such as PIE, and pneumothorax are more readily healed These 3 factors allow less pressure to be necessary in the treatment of lung disease

29. Technical Capability Clinical Implication Pressure Monitoring Tube Purge Tube Pressure Transducer Pressure transducer is located in the Patient Box close to the patient with an automatic monitor-ing line purge system • Allows accurate measurement of high frequency pressure fluctuations in the ET tube without interference from mucus, condensation, etc.

30. Technical Capability Clinical Implication 1:1 Gas Trapping 1:6 No Gas Trapping Extended I:E ratios (1:1 to 1:12) with passive exhalation • Gas trapping is avoided

31. Technical Capability Clinical Implication Volume Increases, Servo Increases Volume Decreases, Servo Decreases Driving pressure is feedback controlled and alarm limits are automatically set and adjustable around this "Servo Pressure" • Changes in lung compliance, pneumothoraces, and the need for suctioning may be detected • Additional volume is automatic-ally provided after changes in the baby's lungs and/or leaks in the ventilator tubing or around the ET tube

32. Technical Capability Clinical Implication Gas is delivered at 100% relative humidity at body temperature via a built-in feedback controlled humidifier • Continuing therapy requires minimal intervention • Labor savings reduce cost of medical care delivery

33. Technical Capability Clinical Implication Ventilator tubing and humidifier circuit need only be changed every seven days • All gas through the circuit is inspired gas • Exhaled goes travels through the conventional ventilator circuit • Patient temperature losses and airway damage is avoided.

34. Technical Capability Clinical Implication Comprehensive alarm system and fail-safe design • Enhanced patient safety.

35. High FrequencyJet Ventilation: General Guidelines

36. The 6 Fundamentals • HFJV P (PIP - PEEP)  PaCO2 • HFJV Rate is secondary • FRC and MAP PaO2 •  PEEP to avoid hyperventilation and hypoxemia • If  CV Rate  oxygenation, PEEP is probably too low •  CV settings whenever possible • Especially when airleaks are a concern •  FiO2 before PEEP until FiO2 < 0.5

37. Common Setting When to Raise When to Lower HFJV PIP 20 cm H2O To lower PCO2 To raise PCO2 (Raise PEEP if necessary to keep MAP and PO2 constant.)

38. Common Setting When to Raise When to Lower HFJV Rate 420 bpm To increase MAP and PO2 To decrease PCO2 in smaller patients To lengthen exhalation time and reduce inad- vertent PEEP in larger patients or when weaning To increase PCO2

39. Common Setting When to Raise When to Lower HFJV I-Time 0.02 seconds To enable Jet to reach PIP at low HFJV rates in larger patients Keep at the minimum of 0.02 in almost all cases

40. Common Setting CV Rate 0 – 3 bpm When to Raise When to Lower To reverse atelectasis • Every chance you get, especially when: • Airleaks are a concern • Hemodynamics are compromised

41. Common Setting CV PIP 15 – 20 cm H2O When to Raise When to Lower To reverse atelectasis Whenever airleaks are present When you’re not seeking to recruit alveoli

42. Common Setting CV I-Time 0.4 seconds When to Raise When to Lower To reverse atelectasis Whenever airleaks are present When you’re not seeking to recruit alveoli

43. Common Setting PEEP 4 – 8 cm H2O When to Raise When to Lower To improve oxygenation To find optimal PEEP (Raise PEEP until SaO2 stays constant when you switch the CV to CPAP) Usually when airleaks are present When you’re not seeking to recruit alveoli

44. Common Setting FiO2 21 – 100 % When to Raise When to Lower As needed Lower in preference to MAP until FiO2 < 45%

45. HFJV Objectives and Actions Managing Oxygenation and Ventilation During High Frequency Jet Ventilation

46. Objective Circumstances Action To Be Taken Lower PCO2 Raise HFJV PIP Lower PCO2 HFJV PIP already uncomfortably high Raise HFJV Rate Note: watch for inadvertant PEEP

47. Objective Circumstances Action To Be Taken Raise PO2 Raise the following in this order: Atelectasis noted on X-ray Institute actions cautiously in infants with PAL 1. PEEP 2. CV Rate (max = 10) 3. CV PIP 4. CV I-Time Discontinue measures once atelectasis disappears and/or PO2 improves CV Rate, PIP, and I-time increases are temporary Use until atelectasis is alleviated Minimize CV Rate thereafter Stabilize alveoli with PEEP

48. Objective Circumstances Action To Be Taken Repeat the previous actions at a higher PEEP level Raise PO2 Previous actions were only temporarily successful Raise PO2 Lungs are over- expanded on X-ray Reduce MAP by decreasing CV support 1. CV Rate < 10 2. CV I-time < 0.5 sec 3. PEEP < 6 cm H20 4. Raise Jet PIP to maintain PO2

49. Objective Circumstances Action To Be Taken Raise PCO2 Lower HFJV PIP and/or raise PEEP Raise PCO2 PO2 drops every time HFJV PIP is dropped Raise PEEP before dropping HFJV PIP

50. Objective Circumstances Action To Be Taken Lower PO2 Lower, in this order, as necessary: 1. FiO2 2. CV PIP and/or Rate 3. PEEP Lower PO2 PCO2 is also low Lower HFJV PIP