Emergency Mechanical Ventilation by Portable Ventilator for AED Doctors

1. Emergency Mechanical Ventilation by Portable Ventilator for AED Doctors Dr LAU Chun Wing Arthur Department of Intensive Care Pamela Youde Nethersole Eastern Hospital 31 Mar 2009

2. Four important equations in respiratory medicine PaCO2 is measured in mm Hg, VCO2 in ml/min (STPD), and VA in L/min (BTPS); hence the units must be converted to mm Hg. This conversion is achieved by the constant, 0.863.

3. Four important concepts in assisted ventilation • Know the set of pathophysiology in your patient • Resistance = ∆Pressure/∆Flow • High: COPD, asthma • Compliance = ∆Volume/∆Pressure • Low (lung): ARDS, APO, pneumonia • Low (chest wall): neuromuscular diseases • High: emphysema • Know how to and how much to correct the pathophysiology (e.g. open lung approach, protective lung strategy, permissive hypercapnia)

4. Invasive and non- ventilation

5. ICU ventilators Siemens Servo i Viasys Avea Draeger Evita 4 Puritan Bennett 840 Have to be equipped with a “noninvasive mode”: leak-tolerant, use only the essential alarms

6. Hybrid ventilators Viasys Vela Bird VSO2

7. Home ventilators Versamed iVent Breas PV 102 Respironics BiPAP Vision Breas LTV 1000 Sirio NIV-S

8. Used in AED of PYNEH

12. SIMV + CPAP mode The patient must be able to produce a negative pressure during inspiration of at least 2 mbar below PEEP (pressure trigger).

13. Facial Nasal Nasal pillow Total face

14. Helmet Nasal prong device

15. Exhalation device • In mask • In circuit • Whisper-Swivel • Whisper-Swivel II • Plateau valve Whisper-Swivel II, Respironics Whisper-Swivel Plateau valve

16. Clinical conditions

17. Scenario 1 • M/80: 60 pack-year smoking history, c/o SOB for 3 days

18. COPD: Ventilation requirements • NIV: very useful • IPPV • Similar for asthma

19. Practical aspect of NIV

20. Predictors of success and failure

21. Scenario 2 • M/20: Non-smoker, c/o wheezing and SOB for 3 days

22. Smooth muscle hypertrophy and spasm Inflamed airway Thick bronchial cast Status asthmaticus: pathophysiology

23. Asthma: Requirements • NIV may not be useful • IPPV setting: • High resistance • Low freq and small volume • Long expiratory time • Zero PEEP • Allow pCO2 to rise (permissive hypercapnia), allow pH around 7.2 • Muscle relaxation

24. Scenario 3 • M/30: Multiple trauma

25. Acute Respiratory Distress Syndrome (ARDS) • Formation of protein-rich alveolar edema after damage to the integrity of the lung’s alveolar-capillary barrier • Can be initiated by physical or chemical injury or by extensive activation of innate inflammatory responses

27. CT thorax ARDS Normal

28. Total PEEP levels applied in recent studies on protective mechanical ventilation Black: study patients White: control patients

29. ARDS requirements • NIV useful only in early acute lung injury (PaO2/FiO2) = 200 to 300, not useful in ARDS (PaO2/FiO2) < 200 • IPPV • Low volume (6ml/kg PBW) • High freq • High PEEP • High FiO2 • Allow pCO2 to rise (permissive hypercapnia) and allow pH around 7.2

30. Scenario 4 • M/60: DM, ECG: ST elevations

31. APO requirements • NIV (both CPAP or BiPAP) useful • IPPV • Low volume (6 – 8 ml/kg PBW) • Higher freq • High PEEP • High FiO2

32. Neuromuscular disease

33. Problems • Removal of secretions • Ventilatory pump failure • Progressive atelectasis • Increasing oxygen requirement • Decreasing MIP and VC

36. Choice of ventilatory support • Noninvasive positive-pressure ventilation • If reversibility is expected over hours to days, e.g. mild LRTI in chronic neuromuscular disease as polymyositis or MG; Problem: secretion retention • Intermittent positive pressure ventilation via endotracheal tube • Assist control or high-level pressure-support • Decelerating ramp • High flow early in inspiration • Larger tidal volumes (12 – 14 ml) may be better tolerated and maximize stimulaton of surfatant production • PEEP: use physiological PEEP (3- 5 cm H2O) • MV adjusted for desired pH • Flow triggering • Tracheostomy for failure to wean within 3 weeks

37. Summary

38. Invasive ventilatory settings in various conditions

39. Non-invasive ventilation

40. SARS Non-invasive ventilation

41. Thank you