Andrea Vianello S.C. Fisiopatologia Respiratoria Ospedale-Università di Padova

1. PNEUMOTRIESTE 2016 CONCETTI GENERALI SUI VENTILATORI Andrea Vianello S.C. Fisiopatologia Respiratoria Ospedale-Università di Padova

2. RESPIRATORY FAILURE LUNG FAILURE PUMP FAILURE GAS EXCHANGE FAILURE VENTILATORY FAILURE HYPERCAPNIA HYPOXEMIA

3. What’s the point of ventilation? • Deliver O2 to alveoli • Hb binds O2 (small amount dissolved) • CVS transports to tissues to make ATP - do work • Remove CO2 from pulmonary vessels • from tissues - metabolism

4. Why ventilate?- purposes • To maintain or improve ventilation, & tissue oxygenation. • To decrease the work of breathing & improve patient’s comfort.

5. When ventilate?- indications • Failure of pulmonary gas exchange • Hypoxaemia: low blood O2 • “Mechanical” failure • Hypercarbia: high blood CO2 • Respiratory muscle fatigue • Need to intubate eg patient unconscious • Others eg • need neuro-muscular paralysis to allow surgery • cardiovascular reasons

6. Definition: What is it? • Mechanical Ventilation =Machine to ventilate lungs = move air in (+ out) • Several ways to..move air in (IPPV vs others) Intermittent Positive Pressure Ventilation

8. Definition: What is it? • Mechanical Ventilation =Machine to ventilate lungs = move air in (+ out) • Several ways to..move air in (IPPV vs others) Intermittent Positive Pressure Ventilation • Several ways to connect the ventilator to the patient

9. Several ways to connect the machine to patient • Oro-tracheal Intubation • Tracheostomy • Non-Invasive Ventilation

10. Normal breath Normal breath inspiration, awake Lung @ FRC= balance Diaphragm contracts -2cm H20 Chest volume Pleural pressure -7cm H20 Alveolar pressure falls Air moves down pressure gradient to fill lungs

11. La pompa diaframmatica genera Pgarantendo la ventilazione polmonare, regolata da: • Equazione di moto del Sistema Respiratorio: Pmusc = V / C + V’ x R

12. Normal breath Normal breath expiration, awake -7cm H20 Diaphragm relaxes Pleural / Chest volume  Pleural pressure rises -2cm H20 Alveolar pressure rises Air moves down pressure gradient out of lungs

13. Ventilator breath Portableventilator ICU ventilator ICU ventilator

14. Ventilator breath Ventilator breath inspiration Air blown in 0 cm H20  lung pressure Air moves down pressure gradient to fill lungs +5 to+10 cm H20  Pleural pressure

15. Il ventilatore sostituisce totalmente o parzialmente la pompa muscolare: • Equazione di moto del Sistema Respiratorio: Pappl (+ Pmusc) = V / C + V’ x R

16. Ventilator breath Ventilator breath expiration Similar to spontaneous…ie passive Ventilator stops blowing air in Pressure gradient Alveolus-trachea Air moves out Down gradient  Lung volume

17. Practicalities • Ventilator settings: • Pressure vs volume • ‘Assist’ vs ‘Control’ • Trigger sensitivity • PEEP?

18. Practicalities Ventilator settings: Pressure vs volume ‘Assist’ vs ‘Control’ Trigger sensitivity PEEP?

19. Details: Inspiration Pressure or Volume? • Do you push in.. • A gas at a set pressure? = ‘pressure…..’ • A set volume of gas? = ‘volume….’

20. Pressure Ventilators • The use of pressure ventilators is increasing in critical care units. • A typical pressure mode delivers a selected gas pressure to the patient early in inspiration, and sustains the pressure throughout the inspiratory phase. • By meeting the patient’s inspiratory flow demand throughout inspiration, patient effort is reduced and comfort increased.

21. Details: Inspiration Pressure or Volume? Pressure cm H20 Time Pressure cm H20 Time

22. Although pressure is consistent with these modes, volume is not. • Volume will change with changes in resistance or compliance • Therefore, exhaled tidal volume is the variable to monitor closely. • With pressure modes, the pressure level to be delivered is selected, and with some mode options, rate and inspiratory time are preset as well.

23. Volume Ventilators • The volume ventilator has been historically used in critical care settings • A respiratory rate, inspiratory time, and tidal volume are selected for the mechanical breaths. • The basic principle of this ventilator is that a designated volume of air is delivered with each breath. • Theamount of pressure required to deliver the set volume depends on : - Patient’s lung compliance - Patient–ventilator resistance factors

24. Details: Inspiration Pressure or Volume?

25. Peak Inspiratory Pressure (PIP ) must be monitored in volume modes because it varies from breath to breath 30 Peak Inspiratory Pressure P aw Time (s) cmH2O 1 2 3 -10

26. Details: Pressure vs Volume in the Acute Setting Secretions hypoventilation Vt preserved partial compensation hypoventilation sensitive insensitive Schönhofer ERS Monograph 2001; 16: 259-73, mod

27. small leak huge leak Details: leak compensation without leakage with leakage Pressure Vol Pressure Vol Pre-set Mehta et al. Eur Respir J 2001; 17: 259-267

28. Practicalities Ventilator settings: Pressure vs volume ‘Assist’ vs ‘Control’ Trigger sensitivity PEEP?

29. Interaction Ventilator Respiratory muscle pump

30. . . Ventilator Respiratory muscle pump work of breathing spontaneous assisted controlled

32. Noninvasive mechanical ventilation in acute exacerbation of restrictive thoracic disease Eur Respir Mon 2001; 6:70-73

34. Practicalities Ventilator settings: Pressure vs volume ‘Assist’ vs ‘Control’ Trigger sensitivity PEEP?

35. Pressure Flow Volume Time 4 Phases • Inspiratory triggering • Inspiration • Termination • of inspiration • Expiration Nilsestuen et al. Respir Care 2005; 50:202-232

36. Details: trigger sensitivity trigger asynchrony insensitive trigger sensitive trigger auto- triggering • trigger sensitivity to low • high level of PSV • hypercapnic encephalopathy • sedation • sleep • intrinsic PEEP (COPD) • tubing obstruction • trigger sensitivity to high • resistance changes • tubing leakage • cardiac oscillation

37. Trigger poco sensibile: allo sforzo inspiratorio non segue l’atto meccanico del respiratore

38. Pao Pes patient 3 patient 1 patient 2

39. Trigger troppo sensibile: l’atto meccanico si innesca spontaneamente

40. Problems: • Increased work of breathing • Need for sedation • „Fighting the ventilator“ • Ventilation-Perfusion-Mismatch • Dynamic hyperinflation • Consequences: • Insufficient ventilation • Withdrawal from NIV • Weaning failure • Prolonged ICU stay • Costs Prognosis ! Asynchrony between patient and ventilator

42. PSV - pressione inspiratoria - sensibilità trigger - eventuale “rampa” (tempo di raggiungimento PS) L’operatore imposta:  • - pressure-controlled • flow-cycled • patient-triggered Caratteristiche: - > sincronismo paziente-ventilatore  > comfort - possibile graduazione sforzo inspiratorio

43. lenta media rapida Diversi tipi di rampa

44. PSV Problemi: • difficoltà di impostazione • livello PS  VT: 6-8ml/Kg; RR: 20-35b/min • P0.1: 2-4 cm H2O • abolizione dissincronismitoraco- addominali • possibile sovrassistenza

45. A-CV -volume corrente -frequenza respiratoria -rapporto I/E -sensibilità del trigger L’operatore imposta: • volume-controlled • time-cycled • machine e/o patient-triggered (assistito) • pressure-limited (eventuale)  - volume corrente insufflato garantito - rapporto I/E variabile Caratteristiche: - possibile sovrassistenza alcalosi respiratoria - insorgenza di PEEP intrinseca Problemi:

46. A-CV

47. Hybrid modes combine the advantages of pressure pre-set and volume pre-set VAPS Volume Assured Pressure Support • Automatic adjustment of inspiratory pressure (range setting) • Target volume set • Measurement of inspiratory pressure and expiratory volume • Calculation of missing inspiratory volume • Increase of inspiratory pressure Assurance of tidal volume + comfort of pressure pre-set

48. VAPS Volume Assured Pressure Support

49. VAPS Volume Assured Pressure Support

50. Storre et al. Chest 2006;130: 815-821