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

QUANDO VENTILARE? CON COSA VENTILARE?. Andrea Vianello S.C. Fisiopatologia Respiratoria Ospedale-Università di Padova. RESPIRATORY FAILURE. LUNG FAILURE. PUMP FAILURE. GAS EXCHANGE FAILURE. VENTILATORY FAILURE. HYPERCAPNIA. HYPOXEMIA. What’s the point of ventilation?

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

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  1. QUANDO VENTILARE? CON COSA VENTILARE? 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. Non-InvasiveVentilation “a formofventilatorysupportthatavoidsairwayinvasion” Hill et al Crit Care Med 2007; 35:2402-7

  7. Paziente con riacutizzazione acidotica di BPCO Terapia medica + O2 q.b. per SpO2 89-92%

  8.  VCO2 Airway narrowing & obstruction Airway Inflammation  Frictional WOB Auto- PEEP Shortened muscles curvature  Elastic WOB Gas trapping  muscle strength VT VE VA • PaCO2 • pH • PaO2

  9.  VCO2 usa i farmaci e bene ! Airway narrowing & obstruction Airway Inflammation Steroids  Frictional WOB Abx Auto- PEEP Shortened muscles curvature BDs  Elastic WOB Gas trapping Teophylline  muscle strength VT VE VA • PaCO2 • pH • PaO2

  10. MV  VCO2 usa i farmaci e bene ! Airway narrowing & obstruction Airway Inflammation Steroids  Frictional WOB Abx PEEP Auto- PEEP Shortened muscles curvature BDs  Elastic WOB Gas trapping Teophylline MV  muscle strength VT VE MV VA • PaCO2 • pH • PaO2

  11. Paziente con riacutizzazione acidotica di BPCO Terapia medica + O2 q.b. per SpO2 89-92% Ripetizione di EGA pH < 7.20 pH < 7.30 pH > 7.35 >7.30 pH < 7.35 NIV non indicata

  12. NIV consigliata l’80% dei pazienti migliora comunque con terapia standard Ogni 10 pazienti trattati con NIV si evita 1 ETI; NIV migliora la dispnea >7.30 pH < 7.35 NIV altamente consigliata Senza NIV 1 paziente su 2 necessita di ETI NIV migliora la sopravvivenza pH < 7.30 NIV altamente consigliata 1 paziente su 2 fallisce NIV Tuttavia con NIV migliora outcome ospedaliero e sopravvivenza a 1 anno pH < 7.20

  13. NIV VS TRATTAMENTO STANDARD Keenan S et al

  14. NIV VS TRATTAMENTO STANDARD Keenan S et al

  15. NIV VS TRATTAMENTO STANDARD Keenan S et al

  16. The ICU studies Confirm the feasibility of NIV Confirm the effectiveness of NIV Selected patients / enthusiastic Units Reduced complications - particularly infectious 16% v 48% 1 ,18 v 60% 2 Reduce ICU / Hospital stay 23 v 35 days 1 , 9 v 15 days 2 • 1. Brochard et al NEJM 1995; 333:817-22 2. Girou et al JAMA 2000; 284:2361-7

  17. 2005; 128

  18. 49 pazienti con IRA in BPCO dopo fallimento terapia medica, pH 7.2 • Simili durata di permanenza in ICU, durata VM, complicanze generali, mortalità in ICU, e mortalità in ospedale • con NIV 48% evitano ETI, sopravvivono con permanenza in ICU inferiorevs pazienti VM invasiva (P=0.02) • A 1 anno: NIV inferiore riospedalizzazione (65% vs 100% P=0.016) e minor frequenza di riutilizzo supplemento di ossigeno (0% vs 36%)

  19. Studio caso-controllo: 64 paz. con IRA trattati con NIV pH = 7.18 • 40/64 (62%) fallimento NIV (RR con NIV - 38%) • Simili mortalità in ICU, e mortalità in ospedale; durata di permanenza in ICU e post ICU, ma: • Inferiori complicanze (P=0.01) e probabilità di rimanenere in VM (P=0.056) • Se NIV efficace (24/64 = 38%) migliore sopravvivenza e ridotta permanenza in ICUvs pazienti VM invasiva NIV riduce necessità di ETI e ospedalizzazione, migliora outcome a lungo termine

  20. 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

  21. 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

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

  23. 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

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

  25. 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

  26. Ventilator breath Portableventilator ICU ventilator ICU ventilator

  27. 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

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

  29. 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

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

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

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

  33. 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.

  34. 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.

  35. Details: Inspiration Pressure or Volume?

  36. 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

  37. 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

  38. 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

  39. 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

  40. Interaction Ventilator Respiratory muscle pump

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

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

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

  44. 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

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

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

  47. Pao Pes patient 3 patient 1 patient 2

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