1. MECHANICAL VENTILATION
KENNEY WEINMEISTER M.D.

2. INDICATIONS FOR MV Hypoxemia Acute respiratory acidosis
Reverse ventilatory muscle fatigue
Permit sedation and/or neuromuscular blockade
Decrease systemic or myocardial oxygen consumption

3. INDICATIONS CONTINUED
Reduce intracranial pressure through controlled hyperventilation
Stabilize the chest wall
Protect airway
Neurologic impairment
airway obstruction

4. TYPES OF CONVENTIONAL MV
Timed cycled
Home ventilators
Pressure cycled
Pressure controlled
Volume cycled
Flow cycled
Pressure support

5. VOLUME VENTILATION Controlled mechanical ventilation CMV
Assist-control AC
Synchronized intermittent mandatory ventilation SIMV
Which mode?

6. VENTILATOR SETTINGS Tidal volume Respiratory rate
10 to 15 mL/kg
Respiratory rate
10 to 20 breaths/minute
normal minute ventilation 4 to 6 L/min
Fraction of inspired oxygen
Flow rate and I:E ratio

7. PRESSURE SUPPORT VENTILATION
Flow cycled
preset pressure sustained until inspiratory flow tapers to 25% of maximal value
Comfortable
Used mainly as a weaning mode
Wean pressure until equivalent to air way resistance
peak - plateau pressure

8. PRESSURE CONTROLED VENTILATION
Pressure cycled
Volume varies with lung mechanics
Minute ventilation is not assured
Improves oxygenation
recruitment of alveoli
Lessens volutrauma?

9. SETTINGS FOR PRESSURE CONTROL VENTILATION
Inspiratory pressure
I:E ratio
1:2, 1:1, 2:1, 3:1
Rate
FIO2
Peep

10. PRESSURE REGULATED VOLUME CONTROLLED
Ventilate with pressure control
Preset volume
Inspiratory pressure is adjusted breath to breath
Minute ventilation is maintained

11. INDICATIONS FOR PEEP ARDS Stabilize chest wall Physiologic peep
Decrease Auto-peep?

12. CONTRAINDICATIONS FOR PEEP
Increased intracranial pressure
Unilateral pneumonia
Bronchoplueral fistulae

13. PEEP Increases FRC Recruits alveoli Improves oxygenation Best Peep
based on lower inflection of pressure volume curve

14. TROUBLE SHOOTING VOLUME VENTILATION
High pressure alarm
Breath sounds
CXR
Low tidal volume
disconnected
Desaturation

15. TROUBLE SHOOTING PRESSURE VENTILATION
Low tidal volumes or minute ventilation
Desaturation
Breath sounds
Patient agitation
CXR

16. Sedation in Mechanically Ventilated Patients
Benzodiazepines
Opioids
Neuroleptics
Propofol
Ketamine
Dexmedetomidine

17. Benzodiazepines Lorazepam Midazolam Half-life 12 to 15 hours
Major metabolite inactive
Midazolam
Half-life 1-4 hours, increased in cirrhosis, CHF, obesity, elderly
Active metabolite

18. Opioid
Morphine
Fentanyl
Hydromorphone

19. Neuroleptics Haloperidol Side Effects Mild agitation .5mg to 2mg
Moderate agitation 2 to 5 mg
Severe 10 to 20 mg
Side Effects
Acute dystonic reactions
Polymorphic VT
Neuroleptic malignant syndrome

20. Propofol Side Effect Anticonvulsant Expensive Use short term
Hypotension
Bradycardia
Anticonvulsant
Expensive
Use short term

21. Ketamine Dissociative anesthetic state Direct cardiovascular stimulant
Brochodilator
Side Effects
Dysphoric reactions
increased ICP

22. Dexmedetomidine Centrally acting alpha 2 agonist
Approved for 24 hours or less
Side Effects
Hypotension
Bradycardia
Atrial fibrillation

23. Maintenance of Sedation
Titrate dose to ordered scale
Motor Activity Assessment Scale MAAS
Sedation-Agitation Scale SAS
Ramsay
Rebolus prior to all increases in the maintenance infusion
Daily interruption of sedation

24. NEUROMUSCULAR BLOCKING AGENTS
Difficult to asses adequacy of sedation
Polyneuropathy of the critically ill
Use if unable to ventilate patient after patient adequately sedated
Have no sedative or analgesic properties

25. Neuromuscular Blocking Agents
Depolarizing
Bind to cholinergic receptors on the motor endplate
Nondepolarizing
Competitively inhibit Ach receptor on the motor endplate

26. Depolarizing NMBA Succinylcholine
Rapid onset less than 1 minute
Duration of action is 7-8 minutes
Pseudocholinesterase deficiency
1 in 3200
Side Effects
Hyperthermia, Hyperkalemia, arrhythmias
Increased ICP

27. Nondepolarizing Agents
Pancuronium
Drug of choice for normal hepatic and renal function
Atracurium or Cisatracurium
Use in patients with hepatic and/or renal insufficiency
Vecuronium
Drug of choice for cardiovascular instability

28. No bubble is so iridescent or floats longer than that blown by the successful teacher. Sir William Osler

30. MV IN OBTRUCTIVE AIRWAY DISEASE
Decrease barotrauma
related to mean airway pressure
Increase I:E
decrease TV and/or increase flow
Minimize auto-peep
auto-peep shown to cause most barotrauma
Permissive hypercapnea

31. ARDS
Set peep to pressure shown at lower inflection point of pressure volume curve
Tidal volumes set below upper inflection point of pressure volume curve
Use pressure control ventilation early
Minimize volutrauma

33. Ventilation With Lower Tidal Volumes
Tidal volume: 6 ml/kg
Male (centimeters of height-152.4)
Female (centimeters of ht )
Decrease or Increase TV by 1ml/kg to maintain plateau pressure 25 to 30.
Minimum TV 4ml/kg
PaO mm Hg. Sats 88 to 95%
pH 7.3 to 7.45

34. CASE EXAMPLE
34 y/o female admitted with status asthmaticus and respiratory failure
You are called to see patient for inability to ventilate
Tidal volume 800 cc, FIO2 100%, AC 12 Peep 5 cm
PAP 70, returned TV 200 cc

35. Case example continued
Examine patient
CXR
Sedate
Assess auto-peep
Increase I:E
Lower PAP and MAP
Reverse bronchospasm & elect. Hypovent.

36. CONCLUSION Three options for ventilation Peep, know when to say no
volume, pressure, flow
Peep, know when to say no
Always assess to prevent barotrauma
ventilate below upper inflection point
assess static compliance daily
monitor for auto-peep