2007 July Lecture Series Mechanical Ventilation

1. 2007 July Lecture Series�Mechanical Ventilation� Kevin P Simpson, MD

2. Ventilator Management Indications for Intubation Classification of Respiratory Failure Initial Ventilator Settings �.and other orders! Daily Assessment of the Ventilated Patient Trouble Shooting: Increased Peak Pressures ETT Position Desaturation Cuff Leaks Self-Extubation Shock � Pneumothorax/Auto-PEEP Patient-Ventilator Dyssynchrony �Double-Triggering� Trach Trouble Weaning Specifics of ARDS and Asthma; Permissive Hypercapnea

3. Ventilator Management:Stepwise Recognize Respiratory Failure Stabilize on the Vent Talk with your nurse! Figure out why? Daily Routine Sound like a doc on rounds. Trouble Shooting That�s what interns do Weaning

4. Indications for Intubation �VOPS� vs �The Look� Ventilation Oxygenation Airway Protection Secretions No single �level� of any vital sign, physical exam finding, or lab value is an indication for intubation

5. Why did this happen?Classification of Respiratory Failure Type I: Acute Hypoxemic Respiratory Failure Severe Hypoxia Refractory to Supplemental Oxygen Type II: Acute Ventilatory Failure Imbalance between Load and Strength

6. I. Acute Hypoxemic Respiratory Failure (AHRF)�.Etiologies Abnormal Alveoli Pulmonary Edema High Pressure CHF Low Pressure ARDS Mixed ? Neurogenic Pneumonia Alveolar Hemorrhage Atelectasis

7. II. Acute Ventilatory Failure

8. Acute Ventilatory Failure Increased Load Resistance COPD, Asthma Elastance ILD, Effusions Minute Ventilation DKA, Sepsis Decreased Strength Reduced Drive Impaired Transmission Muscle Weakness

9. �If you don't know where you are going, you might wind up someplace else.� Try to figure out �why� the patient is requiring intubation.

10. Typical Initial Settings Mode: Goal = �REST� Four Options: SIMV A/C Pressure Support Pressure Control

11. Spontaneous Breathing

12. Spontaneous Breathing Patient does ALL work of breathing TV depends entirely upon patient effort and lung mechanics

13. Synchronized Intermittent Mandatory Ventilation (SIMV)

14. SIMV

16. SIMV Patient does ALL work of breathing on the spontaneous breaths. Plus some work on the SIMV breaths. TV on the spontaneous breaths depends entirely upon patient effort and lung mechanics. Overall, not good for resting the patient.

17. Assist Control/Volume Control

18. Assist Control/Volume Control

19. Assist Control/Volume Control

21. Assist Control/Volume Control Patient does ONLY the work necessary to �trigger� the vent. Typically, minimal (i.e., 2 cm H2O) TV is always the �set� TV. Overall, a very good mode for resting the patient.

22. Pressure Support Ventilation

23. Pressure Support Ventilation

24. Pressure Support Ventilation Patient does a VARIABLE amount of work of breathing: If �adequate� pressure, work is limited to simply that required to trigger. TV depends upon the combination of patient effort/lung mechanics AND the amount of pressure applied. Overall, CAN achieve rest if administer enough pressure. NO back up rate: Not appropriate if fluctuating level of mental status. Limits Peak Pressures

25. SIMV + Pressure Support

26. SIMV + Pressure Support If �adequate� pressure support, work of breathing is minimal. Only that necessary to trigger the vent. If �inadequate� pressure support, work of breathing is similar to SIMV alone. PS = 5 cm H2O is almost always inadequate

27. Pressure Control Ventilation

28. Pressure Control Ventilation

29. Pressure Control Ventilation

30. Typical Initial Settings Mode: Desire �Rest� Either: A/C or SIMV with �adequate� PS

31. Typical Initial Settings Mode: A/C

32. Typical Initial Settings Mode: assist control RR: 12 -16

33. Typical Initial Settings Mode: assist control RR: 12 -16 Tidal Volume: 10-15 cc/kg if �normal� lungs 7-10 cc/kg if typical med-surg patients 5 (or less) cc/kg if ARDS ? Which weight

34. Typical Initial Settings Mode: assist control RR: 12 -16 Tidal Volume: 500 cc

35. Typical Initial Settings Mode: assist control RR: 12 -16 Tidal Volume: 500 cc FIO2: 100% to start Avoid O2 Toxicity Titrate by pulse oximeter (> 92%)

36. Typical Initial Settings Mode: assist control RR: 12 -16 Tidal Volume: 500 cc FIO2: 100% PEEP: Typically start with 5 cm H2O Increase if needed to reach non-toxic FIO2 How much PEEP?

37. Typical Initial Settings Mode: assist control RR: 12 -16 Tidal Volume: 500 cc FIO2: 100% PEEP: 5 cm H2O Goal is to �REST� the patient No distress Don�t forget about sedation

38. Talk with your nurse! Sedation/Pain Control: Versed (100 mg in 100cc) Start 1 mg/hr and titrate to sedation score = 0 Fentanyl (2500 mcg/50cc) Start 1 mcg/kg/hr and titrate to relief of pain CXR immediate and daily Restraints Dobhoff CNU consult for TF�s Change meds to suspension or IV Titrate FIO2 to maintain SpO2 > 92% ? ABG ? ? MDI�s NOTIFY FAMILY

39. Daily Assessment Presentation Style: Hx: Since yesterday� Overnight� Presently� Vitals Exam Ventilator Settings: Mode/Rate/Volume� FIO2/PEEP (PS) On these� Total RR ____ Peak/Plateau __ /__ Raw ____ Compliance ____ ABG: pH/pCO2�/pO2/Sat

40. What are Peak and Plateau Pressures?

44. Airways Resistance and ComplianceBut you said there would be no math�. Raw: [Peak � Plateau]/Flow Rate Flow Rate is in L/sec and is typically ~1 L/s Normal < 10 (cm H2O/L per sec) Static Compliance: TV (cc)/ [plateau � PEEP] Normal > 60 mL/cm H2O Awful! < 20

45. Peak and Plateau Pressures:Pattern Recognition ? Ppeak with a Normal Pplateau = Increased Raw ETT trouble, Bronchospasm Give Bronchodilators ? Ppeak with a ? Pplateau = Decreased Compliance ARDS, IPF, Pneumothorax, Effusions, � Check a CXR

46. Prima non nocere�Peak and Plateau Pressures Avoid: Ppeak > 45 cm H2O Pplateau > 32 cm H2O

47. Flow Rates �Normal� ~ 1 L/sec or 60 L/min �Abnormal� Flow Rates May be uncomfortable and increase WOB May induce tachypnea, double-triggering, auto-PEEP, ALARMS! May be adjusted directly or indirectly By changing the flow profile

50. Flow Rates Consider adjusting when: Elevated Peak Pressures Unexplained tachypnea Patient discomfort Auto-PEEP Increasing Flow Rate: Reduces auto-PEEP but increases peak pressures Decreasing Flow Rate: Reduces peak pressures but increases auto-PEEP

51. Patient Ventilator Dyssynchrony

52. Airway Pressure Waveforms �During true relaxed/passive inflation, the airway pressure tracing shows a smooth rise, it remains convex upward, and it is highly reproducible from breath to breath.� �In a patient who is receiving partial (�inadequate�) ventilator support, the degree of deformation and scooping of the airway pressure provides a means of monitoring the amount of effort expended by the patient.� Charles Alex, MD�..Loyola

53. Auto-PEEP

55. Measuring Auto-PEEP Apply an �expiratory hold� Assess pressure rise

56. Trouble Shooting Increased Peak Pressures: Look at the patient Distress, biting the ETT? Pass suction catheter through ETT Biting the ETT, crusted ETT? Check Peak/Plateau Pressures Primarily increased Raw �.. Bronchodilators Primarily decreased compliance�.check CXR Consider Lower TV, Lower Flow Rate, Sedation

57. Trouble Shooting ETT Position: What�s correct: Below the larynx At least 2 cm above the carina How do you know? �corner of the mouth� Average 22 cm in women, and 23 cm in men CXR position ? Variation with head position

59. Trouble Shooting Desaturation 100% FIO2, Suction/Bag Patient Cuff Leak (Exhaled TV < Inhaled TV) Inflate Balloon, Replace ETT Self-Extubatioin URGENT assessment, �Dr. Respiratory� Shock Pneumothorax, Auto-PEEP Trach Trouble ENT (Don�t replace yourself if a fresh trach)

60. �Weaning� Daily Assessment

61. �Weaning� Daily Assessment Weaning Parameters RSBI RR/TVL < 100 predicts success NIF (or MIP) Less negative than -20 cm H2O predicts failure

62. �Weaning� Daily Assessment Weaning Parameters RSBI NIF T-Piece Trial Pressure Support possibly equivalent SIMV delays extubation

63. Weaning Trials

64. Weaning Trials

65. �Weaning� Daily Assessment Weaning Parameters RSBI NIF T-Piece Trial Trial of Extubation

66. General �Rules� of Mechanical Ventilation Indications for Intubation�. �The Look� �Rest�� Get rid of �The Look� Keep the Pressures Low� Peak < 45 cm H2O Plateau < 32 cm H2O Forget the PaCO2�. �Permissive Hypercapnea�

67. Who�s Watching the Patient?

68. General �Rules� of Mechanical Ventilation �Make the Beeping Stop�

69. Status Asthmaticus Maximize Medical Therapy Nebulized Albuterol Nebulized Ipratropium Bromide IV Steroids IV Magnesium NOT: CPT Acetylcysteine Antibiotics � unless infection

70. Status Asthmaticus Heliox Decreased WOB Unclear Role Ventilator Strategy High Inspiratory Flow Rate 80-100L/min Accept High Peak Pressures Increase Expiratory Time Reduces auto-PEEP Try to avoid neuromuscular blockade Risk of prolonged weakness

71. �Permissive Hypercapnea� Accept Hypercapnea Rather than impose high pressures Minimizes risk of barotrauma Reduces ventilator-induced lung injury ? Bicarbonate Drip If pH unacceptably low ? �permissive acidosis�

72. ARDS�Definition Severe Hypoxemia P/F ratio < 200 Diffuse CXR Lesion 3 of 4 quadrants Normal Pcwp �no CHF� ?�d Compliance

73. ARDS�Treatment of Hypoxia Treat the Underlying Cause Supplemental O2 Diuresis PEEP Optimize the Mixed Venous O2 Prone Positioning

74. Treat the Underlying Cause Pneumonia Sepsis Aspiration Trauma Multiple Transfusions Pancreatitis Inhalational Injury

75. Supplemental O2 Mainly Shunt therefore poor response to O2 ? O2 Toxicity Only use �toxic� FiO2 if significant improvement on PaO2

76. Supplemental O2 Mainly Shunt therefore poor response to O2 ? O2 Toxicity Only use �toxic� FiO2 if significant improvement on PaO2

77. Decrease Drive to Edema Formation

78. Decrease Drive to Edema Formation

79. Decrease Drive to Edema Formation

80. PEEP Good�. Recruits Alveoli Redistributes Pulmonary Edema Fluid ? PaO2 Bad�. ?�d Venous Return / C.O. ?�s Risk of Barotrauma

84. Optimize the Mixed Venous O2 ? O2 Consumption Treat Fever Decrease WOB Sedation Analgesia Muscle Relaxation ? O2 Delivery DaO2 = CO X CaO2 CaO2 = 1.39 X Hgb X Sat + 0.0031 X PaO2

86. Effect of Prone Positioning on PaO2

87. ARDS�Treatment Treat the Underlying Cause Supplemental O2 Diuresis PEEP Improve Mixed Venous O2 Prone Positioning

88. Acute Ventilatory Failure

89. Acute Ventilatory Failure

90. Acute Ventilatory Failure Manifested by: Hypercapnea or Eucapnea with Increased MV Requirements or Increased �Work of Breathing� PaCO2 = (VCO2 x k)/VA VA = MV (1 � VD/VT) Therefore, Hypercapnea requires: ? VCO2 (extremely rare) ? MV (easily recognized) ? VD/VT (don�t forget!)

91. Acute Ventilatory Failure:? VD/VT Dead Space: Ventilated but Non-Perfused Alveolar Units Anatomic Dead Space Averages 1 cc/kg (or 30% of a typical TV) Physiologic Dead Space: ? Zone 1 ? Pulmonary Perfusion (i.e., volume depletion) ? Alveolar Pressures (i.e., PEEP) Pulmonary Vascular Disease Pulmonary Hypertension Pulmonary Embolism

92. Acute Ventilatory Failure Increased Load Resistance COPD, Asthma Elastance ILD, Effusions Minute Ventilation DKA, Sepsis Decreased Strength Reduced Drive Impaired Transmission Muscle Weakness

93. Acute Ventilatory Failure:Neuromuscular Disease Vital Capacity ? Intubate when < 15 cc/kg (~1 liter) Spinal Cord Injury C3-C5 Phrenic Nerve Injury Post-Cardiac Surgery, Traumatic, Post-Lung Transplant Unilateral, rarely problematic Severe Orthopnea, Thoraco-Abdominal Paradox

94. Acute Ventilatory Failure: Treatment Underlying Cause Oxygen May increase PaCO2 NOT by �Blunting Drive to Breath� Promotes VQ Mismatch and Dead Space Assisted Ventilation Nasal CPAP / BiPAP Intubation

95. CPAP/BiPAP Indications Acute Pulmonary Edema �Severe� COPD Exacerbations Acute Respiratory Failure in the Immunosuppressed To Facilitate Early Extubation in COPD Note: NOT for extubation failures