Neonatal Mechanical Ventilation

1. University of Minnesota Children’s Hospital Neonatal Mechanical Ventilation Mark C Mammel, MD OF MINNESOTA

2. Mechanical ventilation • What we need to do • Support oxygen delivery, CO2 elimination • Prevent added injury, decrease ongoing injury • Enhance normal development

3. Mechanical ventilation • Support oxygen delivery, CO2 elimination • Headbox O2 • Cannula O2 • CPAP ± IMV • Intubation, ventilation

4. Mechanical ventilation • Prevent added injury • Minimize invasive therapy • Optimize lung volume • Target CO2, O2 • Use appropriate adjuncts • Manage fluids and nutrition

5. Mechanical ventilation • Enhance normal development • Manage fluids and nutrition • Encourage patient-driven support • Maintain pulmonary toilet- carefully

6. Support devices

7. Mechanical ventilation • Key concepts: • Maintain adequate lung volume • Inspiration: tidal volume • Expiration: End-expiratory lung volume • Support oxygenation and CO2 removal • Oxygenation: adequate mean airway pressure • CO2 removal: adequate minute ventilation

8. Mechanical ventilation • Key concepts: • Optimize lung mechanical function • Compliance: ∆V/∆P • Resistance: ∆Flow/∆P • Time constant: C x R

10. Boros SJ et al: J Pediatr1977; 91:794

12. Patient Patient Exhalation Inspiration Mechanical ventilation: How does it work?

13. Mechanical Ventilation:Mode classification A. Trigger mechanism • What causes the breath to begin? B. Limit variable • What regulates gas flow during the breath? C. Cycle mechanism • What causes the breath to end? B C A

14. A. Inspiratory Trigger Mechanism • Time • Controlled MechanicalVentilation – NO patient interaction • Pressure • Ventilator senses a drop in pressure with patient effort • Flow • Ventilator senses a drop in flow with patient effort • Chest impedance / Abdominal movement • Ventilator senses respiratory/diaphragm or abdominal muscle movement • Diaphragmatic activity • NAVA- Neurally adjusted ventilatory assist

15. B. Limit Variable Ti Ti Pressure A. Pressure limited Volume B. Volume limited A B

16. C. Cycle MechanismWhat causes the breath to end? Ti Ti Ti • A. Time • All ventilators • B. Flow • Pressure support modes • C. Volume • Adult / pediatric ventilators Pressure Flow Volume A B C

17. Basic waveforms

18. Time cycle- fixed Ti

19. Flow cycle- variable Ti with limit

20. Mechanical ventilation: Which vent? • Conventional • Dräger Babylog 8000 • Avea • Servo i • High frequency • SensorMedics oscillator • Bunnell HFJV

21. Conventional Ventilation • Modes: • CPAP • +/- Pressure support (PSV) • IMV/SIMV • +/- Pressure support (PSV), volume targeting • Assist/control (PAC) • +/- volume targeting

22. Continuous positive airway pressure: CPAP • Goal: • Support EELV in spontaneously breathing infant (optimize lung mechanics) • Delivery: • NeoPuff, other dedicated CPAP devices • HFNC • Using mechanical ventilator • May be done noninvasively or via ET tube (HFNC in extubated patients only) • Patients: • Newborn infants ≥26 wks with early distress • Infants in NICU with new distress or apnea • Extubated infants

23. Continuous positive airway pressure: CPAP • Setup: • NeoPuff, other dedicated CPAP devices: • Nasal prong interface • Set PEEP (4-6 cm H2O most common) • SiPAP: special type of CPAP. Uses 2 levels, usually 2-4 cm H2O different • HFNC • Nasal cannula interface • 2-4 L/min flow • Monitoring • CPAP: airway pressure displayed and alarmed • HFNC: none

24. Early CPAP • Columbia Presbyterian 500-1500 gm Infants: Variation in CLD * % * *p<0.0001 * * Van Marter et al. Pediatrics 2000;105:1194-1201

25. Intermittent mandatory ventilation: IMV/ SIMV • Goal: • Support EELV and improve Ve in spontaneously breathing infant requiring intubation • Eliminate breath-breath volume variation, cerebral blood flow abnormalities, allow patient control via synchronization of SOME breaths • Delivery: • Using mechanical ventilator • May be done noninvasively or via ET tube • Patients: • Newborn infants requiring intubation • Extubated infants with persistent distress

26. Intermittent Mandatory Ventilation: IMV/ SIMV • Setup: • ET tube interface • Variables: • Rate- range 15-60 bpm; always synchronized • Volume- target volume 4-7 mL/kg • Pressure- Set peak pressure limit (usually 30 cmH2O). Pressure then adjust based on volume. Set PEEP 5-7 cmH2O • Time- set Ti at 0.3 – 0.5 sec based on pt size • Monitoring • Dynamic. Multiple alarm settings. All measured and calculated parameters may be displayed and trended

27. IMV- unsynchronized

28. Impact of synchronization

29. Assist/control: PAC • Goal: • Support EELV and improve Ve in apneic or spontaneously breathing infant requiring intubation • Eliminate breath-breath volume variation, cerebral blood flow abnormalities, allow patient control via synchronization of ALL breaths • Delivery: • Using mechanical ventilator • Done via ET tube • Patients: • Newborn infants requiring intubation

30. Assist/control: PAC • Setup: • ET tube interface • Variables: • Rate- set minimum acceptable rate, 40-60 bpm; actual rate depends on patient effort • Volume- target volume 4-7 mL/kg • Pressure- • Peak pressure: Set limit (usually 30 cmH2O). Pressure then adjust based on volume. • PEEP: 5-7 cmH2O • Time- set Ti maximum at 0.3 – 0.5 sec based on pt size. Actual Ti varies with lung mechanics. Te varies with rate • Monitoring • Dynamic. Multiple alarm settings. All measured and calculated parameters may be displayed and trended

31. Assist/control- full synchronization

32. Conventional Ventilation • Variables- What does what? • Minute ventilation (Ve): PaCO2 • Ve = RR x Vt • Vt changes with changing lung mechanics • Tools to change: PIP, PEEP, Ti, Te • Oxygenation: PaO2, SaO2 • Mean airway pressure (Paw) • Oxygenation varies with lung volume, injury • Tools to change: PIP, PEEP, Ti, Te

33. Conventional Ventilation • Variables- What does what? • Minute ventilation (Ve): PaCO2 • Ve = RR x Vt • Vt changes with changing lung mechanics • Tools to change: PIP, PEEP, Ti, Te

34. Assessment of Vt: PAC (no volume target)

35. Assessment of Vt: PAC, improved C

36. Assessment of Vt: PAC + V, imp C- no limit

37. Conventional Ventilation • Boros SJ, et al. Pediatrics 74;487:1984 • Mammel MC, et al. Clin Chest Med 1996;17:603

38. Conventional Ventilation • Variables- What does what? • Oxygenation: PaO2, SaO2 • Mean airway pressure (Paw) • Oxygenation varies with lung volume, injury • Tools to change: PIP, PEEP, Ti, Te

40. Lung Volume • Optimize lung volume • Define opening pressure, closing pressure, optimal pressure: dependent on estimation of lung volume • Problems: no useful bedside technology to measure either absolute or change in lung volume Pmax Popt Volume Pcl Pop Pressure

41. Lung Volume • Optimize lung volume • SaO2 as volume surrogate Tingay DG et al. Am J Resp Crit Care Med 2006;173:414

42. Assessment of Paw – Ti adjustment

43. Assessment of Paw – PEEP adjustment

44. Assessment of Paw – PIP adjustment

45. Assessment of Paw – Rate adjustment

46. Neonatal Mechanical Ventilation:Ventilator setup

47. Mechanical ventilation • What we know: general • Support affects pulmonary, neurologic outcomes • Greater impact at lower GA • VILI is real • Less is usually more

48. Mechanical ventilation • What we need to know • Who needs support? • Who needs what support? • Risk/benefit for various modalities • When (how) do you wean/stop support?