2007 July Lecture Series “Mechanical Ventilation”

1. 2007 July Lecture Series“Mechanical Ventilation” A July Intern’s Guide to Ventilators 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. Type I: Acute Hypoxemic Respiratory Failure Severe Hypoxia Refractory to Supplemental Oxygen Type II: Acute Ventilatory Failure Imbalance between Load and Strength Why did this happen?Classification of Respiratory Failure

6. I. Acute Hypoxemic Respiratory Failure (AHRF)….Etiologies • Normal Alveoli • Intra-cardiac Shunts • PFO • VSD,ASD • Intrapulmonary Shunts • AVM • Hepato-Pulmonary Syndrome • Abnormal Alveoli • Pulmonary Edema • High Pressure • CHF • Low Pressure • ARDS • Mixed • ? Neurogenic • Pneumonia • Alveolar Hemorrhage • Atelectasis Rarely Acute Commonly Acute

7. II. Acute Ventilatory Failure Strength Load

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

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 ? TV Inspiration Expiration

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

13. Synchronized Intermittent Mandatory Ventilation (SIMV) “Set” TV ? TV

14. SIMV Peak Pressure depends upon TV and lung mechanics

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 “Set” TV

19. Assist Control/Volume Control Peak Pressure depends upon TV and lung mechanics

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 ? TV

23. Pressure Support Ventilation Peak Pressure depends solely upon the amount of Pressure Support

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 “Set” TV ? TV

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 Specifically Set Inspiratory Time Reduced Expiratoy Time

28. Pressure Control Ventilation Peak Pressure depends solely upon the amount of pressure applied.

29. Pressure Control Ventilation • Almost never used as initial setting: • Reserved for refractory hypoxemia. • MAY increase gas exchange. • Limits Peak Pressure. • Prolonged Inspiratory Time results in Reduced Expiratory Time • Potential for auto-PEEP

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: • 7-8 cc/kg if “normal” lungs • 7-8 cc/kg if typical med-surg patients • 6 (or less) cc/kg if ARDS • ? Which weight – predicted body 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. Sedation/Pain Control: Midazolam (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 Talk with your nurse!

39. 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 Daily Assessment

40. What are Peak and Plateau Pressures?

42. PIP:complianceresistancevolumeflow PEEP Pressure PEEP time

43. No active breathing Treats lung as single unit PIP resistance flow Pplat end-inspiratory alveolar pressure compliance tidal volume PEEP

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

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

49. PRESSUREALARM 80 Pao . V x Ti Te Ti Te TIME Choose Your Poison Pressure: Peak or auto-PEEP

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