Mechanical ventilation in COPD Asthma drtrc


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Mechanical ventilation in COPD Asthma drtrc

  1. 1. Conventional Mechanical Ventilation for Respiratory Failure in COPD Dr.T.R.Chandrashekar M.D Director critical care K.R.Hospital, Bangalore .
  2. 2. COPD <ul><li>It is defined as a preventable and treatable disease state characterized by airflow limitation that is not fully reversible </li></ul><ul><li>The airflow limitation is in most cases is both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases . </li></ul><ul><li>Although COPD affects the lungs, it also produces significant systemic consequences </li></ul>
  3. 3. Systemic effects of COPD Effects Mechanism
  4. 4. Why COPD is Important ? <ul><li>COPD is the only chronic disease that is showing progressive upward trend in both mortality and morbidity </li></ul><ul><li>It is expected to be the third leading cause of death by 2020 </li></ul><ul><li>Approximately 14 million Indians are currently suffering form COPD* </li></ul><ul><li>Currently there are 94 million smokers in India </li></ul><ul><li>10 lacs Indians die in a year due to smoking related diseases </li></ul><ul><li>* The Indian J Chest Dis & Allied Sciences 2001; 43:139-47 </li></ul>
  5. 5. In COPD limitation is EF <ul><li>No conventional ventilator supports expiration actively </li></ul><ul><li>How does MV help ? </li></ul><ul><li>Although the load is expiratory the failure is inspiratory </li></ul>Inspiratory muscle loading and fatigue is of central pathophysiological importance in the development of acute respiratory failure
  6. 6. Pathophysiology of COPD Expiratory flow limitation is the primary problem
  7. 7. Lung Capacity and Disease Space for fresh air TLC
  8. 8. The Vicious Cycle Increased resistance Airtrapping Decreased Compliance ↑ PVR >DH >DH  WOB FATIGUE ↑ PCO2/↓Pao2 ↓ PH V/Q mismatch
  9. 9. Worsening EFL <ul><li>Gas Exchange </li></ul><ul><li>Vd/Vt increase </li></ul><ul><li>Neuromechanical </li></ul><ul><li>Uncoupling </li></ul><ul><li>Dyspnea </li></ul>COPD Exacerbation <ul><li>Increased ventilatory drive </li></ul><ul><li>Hypoxia </li></ul><ul><li>Hypercarbia </li></ul><ul><li>Acidosis </li></ul>Tachypnea DH EELV, IC <ul><li>Mechanical </li></ul><ul><li>Disadvantage </li></ul><ul><li>PEEPi </li></ul><ul><li>Cdyn </li></ul><ul><li>Elastic/threshold </li></ul><ul><li>loading of insp muscles </li></ul><ul><li>Insp muscle dysfn </li></ul><ul><li>CVS effects </li></ul><ul><li>Pulm MAP </li></ul><ul><li>RV preload </li></ul><ul><li>LV afterload </li></ul>
  10. 10. Identify & Measure Complications Manage COPD Key factor is DH Auto PEEP PEEPi EELV
  11. 11. Concept of DH <ul><li>It is a adaptive mechanism which leads to increased elastic recoil force and keeps airways patent to force out air but…. </li></ul><ul><li>Due to use of accessory muscle usage increased force is also applied to airways which lead to collapse & exaggerate the EFL </li></ul>
  12. 12. Concept of Auto PEEP, DH <ul><li>AUTO PEEP is defined as the difference between PEEP set by the clinician and the PEEP as measured by the ventilator with an expiratory hold. </li></ul>
  13. 13. Identification of Auto PEEP Inspiration Expiration Time (sec) Flow (L/min) } Normal Patient Air Trapping Auto-PEEP
  14. 14. Measurement of Auto PEEP Reduce set PEEP to zero before measuring Auto PEEP Paralysed patient only AT HE END OF EXPIRATION 2 -3 SEC OCCULSION
  15. 15. Auto-PEEP and Volume of Trapped Gas Tuxen, Am Rev Respir Dis 1989; 140:5
  16. 16. WHAT ARE EFFECTS OF AUTO PEEP? <ul><li>Hemodynamic compromise. </li></ul><ul><li>Due to increase in FRC, respiration starts in the flatter portion of the P/V curve, where change in volume for a change in pressure is less –Increased WOB. </li></ul><ul><li>Trigger will have to cross the auto PEEP level before inspiration is initiated. </li></ul><ul><li>Missed breaths </li></ul>
  17. 17. Mechanical Effects of AECOPD Thorax 2006;61:354-61
  19. 19. Missed breath Auto PEEP Wasted effort, increased WOB
  20. 20. There are only 3 factors that determine auto-PEEP. <ul><li>Minute ventilation. (It doesn’t matter whether it’s from respiratory rate or VT). </li></ul><ul><li>I: E [inspiratory: expiratory] ratio. </li></ul><ul><li>Expiratory time constants. </li></ul>Let us learn how to manipulate these parameters To prevent Auto PEEP
  21. 21. CO2 removal is inversely proportional to Minute Ventilation CO2 removal is inversely proportional to Effective Alveolar Ventilation Effective Alveolar Ventilation = Minute Ventilation – Dead Space Ventilation
  22. 22. COPD on ventilator on VC Vt 500ml, Fio2 40%, PEEP 4cms H2o RR10/mt, I:E 1:2 Po2 is 60, PCo2 is 68 Increase Vt to 500ml Increase RR 15 After one hr repeat ABG shows PO2 of 58 PCO2 of 83 Minute ventilation of 500x10=5000 Minute ventilation of 500x15=7500
  23. 23. Effective Alveolar ventilation <ul><li>Vt=500ml </li></ul><ul><li>RR=10 </li></ul><ul><li>MV=5l </li></ul><ul><li>EAV=MV-Dead space </li></ul><ul><li>Dead space ventilation </li></ul><ul><li>=150x10=1.5l </li></ul><ul><li>EAV=5l-1.5l=3.5l </li></ul><ul><li>Vt-500ml </li></ul><ul><li>RR= 15 </li></ul><ul><li>MV=7.5l </li></ul><ul><li>EAV=MV-Dead space </li></ul><ul><li>Dead space ventilation </li></ul><ul><li>=300x15=4.5l </li></ul><ul><li>EAV=7.5l-4.5l=3.0l </li></ul>
  24. 24. FRC EELV/DH COPD compliance Resistance PVR
  25. 25. Respiratory rate <ul><li>RR 10breaths/ min, If I:E ratio 1:2 </li></ul><ul><li>Total cycle time 60 sec/10 = 6 sec </li></ul>Inspiration = 2seconds Expiration 4 seconds RR 20 breaths/ mt, I:E Ratio 1:2, TCT=60/20=3 sec Inspiration = 1seconds Expiration 2 seconds 3 sec 1sec 2 sec
  26. 26. Minute ventilation <ul><li>Tidal volume=6-7ml/kg </li></ul><ul><li>Rate 12/mt, IC is reduced </li></ul><ul><li>Low minute ventilation leads to ↑ PCO2 which is the price we pay for preventing DH, </li></ul><ul><li>In fact current literature suggests that risk of dynamic hyperinflation is much larger than those of permissive hypercapnia. </li></ul><ul><li>Provide enough ventilation to keep a normal PH, not a normal PCO2. </li></ul>
  27. 27. Manipulate - I:E Ratio Pressure T ime Gives more time for expiration and reduces DH T insp . . I : E = 1 : 2 I : E = 1: 3 PEEP PIP PIP PEEP T insp . T exp Total cycle time
  28. 28. Peak flow <ul><li>Normally in adults it is set between 40-60l/min, or can be calculated as follows </li></ul>Ins time Tidal volume PEAK FLOW = X 60 A peak flow of around 80-90l/mt
  29. 29. RISE TIME 40 P CIRC cmH 2 O INSP EXP 30 20 10 0 10 -20 80 60 40 20 0 20 -80 40 60 0 4 8 12s 2 6 10 Slow rise Moderate rise Fast rise TE TE TE TI L min V .
  30. 30. PEAK FLOW Peak Flow 30l/mt Peak Flow 90 l/mt
  31. 31. Addition of external PEEP “The Paradox “
  32. 33. +6 +6 +7 Pleural Alveolus Mouth start of Inspiration Airway Pressures with Auto-PEEP Auto-PEEP = +6 Wilson et al, U of Iowa
  33. 34. Can PEEP be used in all COPD pts? <ul><li>Whenever accessory muscles are in use to counter act them PEEP can be used </li></ul><ul><li>when patients are on partial/ supported modes </li></ul><ul><li>In asthmatics and when patients are paralysed the response can be variable and unpredictable… </li></ul><ul><li>Then the question arises how to be sure it is not harmful? </li></ul>
  34. 35. Monitoring the response to external PEEP
  35. 36. 0 cm H 2 O PEEP 8 cm H 2 O PEEP Auto peep
  36. 37. Calculation of Exp time constants <ul><li>Compliance x Resistance </li></ul><ul><li>0.1l/cmH2O x 5 cmH2O/l/sec= o.5 sec </li></ul><ul><li>0.5 x3= 1.5 sec </li></ul><ul><li>Increased resistance </li></ul><ul><li>0.1 x 20 = 2sec </li></ul><ul><li>2x3=6sec </li></ul>
  37. 38. Management of Auto PEEP. <ul><li>1) low tidal volume </li></ul><ul><li>Decrease the RR </li></ul><ul><li>2) Increase expiratory time. </li></ul><ul><li>3) Increase peak flow </li></ul><ul><li>4) Addition of Extrinsic PEEP </li></ul><ul><li>Sedation/Control of Fever </li></ul><ul><li>6) Bronchodilatation </li></ul>}}} Low MINUTE VENTILATION
  38. 39. <ul><li>Ventilatory support in COPD…… </li></ul>
  39. 40. ARF-COPD <ul><li>ABG </li></ul><ul><li>PH-7.45 </li></ul><ul><li>PO2-57mmHg </li></ul><ul><li>PCO2-65mmHg </li></ul><ul><li>Spo2-89% </li></ul><ul><li>HCo3-34mmoles </li></ul><ul><li>Patient is 60 yr old has COPD on room air </li></ul><ul><li>Comfortable </li></ul><ul><li>RR-25/mt </li></ul><ul><li>HR-100/mt </li></ul>
  40. 41. ARF-COPD <ul><li>ABG </li></ul><ul><li>PH-7.30 </li></ul><ul><li>PO2-57mmHg </li></ul><ul><li>PCO2-65mmHg </li></ul><ul><li>Spo2-89% </li></ul><ul><li>HCo3-23mmoles </li></ul><ul><li>Patient is restless </li></ul><ul><li>Disoriented </li></ul><ul><li>Accessory muscle used </li></ul><ul><li>RR-35/mt </li></ul><ul><li>Paradoxical breathing </li></ul><ul><li>0n 4l of oxygen on resv bag. </li></ul>Baseline Pco2, PH, WOB, Hemodynamic stability, FIO2,Mentation Should be kept in mind while interpreting ABG’s and decision to ventilate
  41. 42. Spontaneous Weaning Controlled Conventional ventilation NIV Mechanical ventilation
  42. 43. Ventilation difficulties in COPD <ul><li>Ventilating a COPD patient is difficult because the disease may not have a reversible component, </li></ul><ul><li>Quantifying dynamic hyper inflation at bedside is very difficult </li></ul><ul><li>COPD patients are difficult to wean. </li></ul><ul><li>Co morbidities & systemic effects </li></ul>
  43. 44. <ul><li>60 yr old COPD patient is </li></ul><ul><li>Drowsy, disoriented </li></ul><ul><li>RR-40/mt, accessory muscle+, </li></ul><ul><li>BP-80/50mmHg, </li></ul><ul><li>ABG –PH-7.08, </li></ul><ul><li>PCO2-85mmHg,Pao2-49mmHg, </li></ul><ul><li>SPo2-83% on 5l of oxygen </li></ul><ul><li>or </li></ul><ul><li>COPD pt on NIV after 2hrs restless , not synchronizing, PH,PCO2,PO2 deteriorated </li></ul>Case scenario
  44. 45. Indications for Invasive Mechanical Ventilation. <ul><li>NIPPV failure. </li></ul><ul><li>Severe dyspnea with use of accessory muscles+. </li></ul><ul><li>RR> 35 breaths per minute. </li></ul><ul><li>Life-threatening hypoxemia (PaO2, 50-40 mm Hg). </li></ul><ul><li>Severe acidosis (pH < 7.25) and hypercapnia ( >60 mm Hg). </li></ul><ul><li>Respiratory arrest. Somnolence, impaired mental status. </li></ul><ul><li>Cardiovascular complications (hypotension, shock, heart failure). </li></ul>
  45. 46. Intubation and MV <ul><li>Decision to intubate if the patient is not a candidate for NIV or has not done well on NIV- has to be made decisively and if delayed both morbidity and mortality are higher. </li></ul><ul><li>Post intubation bagging has to be low tidal volume and low rate 6-7/mt. </li></ul>If paralysed keep them on relaxants for a day or two. Fill them adequately before induction , Add a small dose of a inotrope in a corpulmonale patient
  46. 47. Ventilatory settings in passive pt <ul><li>Set a moderate FIO2, usually 40%, target a SPO2 of 90% </li></ul><ul><li>Mode –Volume controlled, square wave. </li></ul><ul><li>Tidal volume = </li></ul><ul><li>RR= </li></ul><ul><li>I: E ratio = </li></ul><ul><li>Flow </li></ul>7ml/kg 12/mt =80-100l/mt 1:3 or more depending on expiratory time constants
  47. 48. Ventilation in a passive patient <ul><li>External-PEEP application has a variable and unpredictable response </li></ul><ul><li>Due to no contribution of the expiratory muscles, the reason how external PEEP helps to reduce DH </li></ul><ul><li>Reducing the lung heterogeneity. </li></ul><ul><li>Opening up previously closed units it could help in mucus clearance and bronchodilator therapy. </li></ul>
  48. 49. Paw (cm H 2 O) Normal P Plat (Normal Compliance) Increased PIP } Increased P TA (increased Airway Resistance ) Increased Airway Resistance Begin Inspiration Begin Expiration P aw (cm H 2 O) Time (sec) Airway Resistance Distending (Alveolar) Pressure Expiration PIP Normal Inflation Hold (seconds)
  49. 50. <ul><li>A PIP = 40-45 cmH2O. </li></ul><ul><li>Ppl pressure < 30cmH2O. </li></ul><ul><li>Minimal sensitivity- Pressure or Flow trigger. </li></ul><ul><li>PEEP setting- Start at 5 cmH2O, any further increase always look at PIP and plateau pressure. </li></ul><ul><li>Any increase in these pressures, decrease PEEP. (Keep a close watch on hemodynamics) </li></ul>
  50. 51. Ventilating a spontaneous patient <ul><li>PS /PC mode/PAV </li></ul><ul><li>Pressure support to generate 7ml/Kg VT </li></ul><ul><li>Minimal trigger setting- flow or pressure </li></ul><ul><li>Peak flow -80-100l/min </li></ul><ul><li>PEEP can be added starting at 5cmH2O in an increments of 2cmH2O </li></ul>
  51. 52. Ventilating a spontaneous patient <ul><li>You rarely require more than 10cmH2O PEEP. </li></ul><ul><li>Expiratory sensitivity (PS) can be set much above the default setting of 25%.( 40%) </li></ul><ul><li>If the patient is not synchronizing, increasing PS could lead to increased VT, DH, and missed breaths. </li></ul><ul><li>In such a situation other causes like fever, pain etc have to be looked for. In case no other cause can be found, sedation can be used . </li></ul>
  52. 53. CYCLING AT 40% OF FLOW CYCLING AT 25% 0F PEAK FLOW PRESSURE SUPPORT Flow cycling Flow Time Peak flow 40% 25%
  53. 54. Weaning <ul><li>Weaning begins when the precipitating factor of the respiratory failure is partially or totally reversed. </li></ul><ul><li>Marginal respiratory mechanics. </li></ul><ul><li>Factors which increase resistance like size of the tube, deposition of secretions in the tube, kinking/curvature of the tube, presence of elbow-shaped parts, HME in the circuit </li></ul>Steroids + Relaxants Myopathy
  54. 55. Weaning <ul><li>Role of tracheostmy is uncertain, but due to marginal respiratory mechanics it is thought it may help in weaning. </li></ul><ul><li>Weaning can be done with PS mode to SBT. </li></ul><ul><li>In very difficult cases extubation on to NIV is a option </li></ul><ul><li>Corpulmonale may warrant small dose of inotrope, a dose of diuretic & low fluid strategy during weaning. </li></ul>
  55. 56. IN COPD <ul><li>Preventing VILI is not the primary objective here; </li></ul><ul><li>Avoiding barotrauma, improving airway clearance, and reducing the consequences of hyperinflation have been the motivators. </li></ul><ul><li>Yet, use of small VT for avoidance of high plateau pressure, </li></ul><ul><li>Acceptance of permissive hypercapnia, </li></ul><ul><li>Judicious use of PEEP to lessen effort and perhaps to reopen compromised airways in some patients now guide the care of obstructed patients as well. </li></ul>
  56. 57. Thank you Stop Smoking……