MECHANICAL VENTILATION

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MECHANICAL VENTILATION

• Marc Charles Parent

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Presentation

• Different settings to consider
• Monitoring of the patient
• Different type of patient
• COPD, Asthma
• ARDS
• Trouble shooting

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Ventilator settings
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Ventilator settings

1. Ventilator mode
2. Respiratory rate
3. Tidal volume or pressure settings
4. Inspiratory flow
5. IE ratio
6. PEEP
7. FiO2
8. Inspiratory trigger

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CMV
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A/CV
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SIMV
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PSV(pressure support ventilation)

• Spontaneous inspiratory efforts trigger the
  ventilator to provide a variable flow of gas in
  order to attain a preset airway pressure.
• Can be used in adjunct with SIMV.

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Respiratory Rate

1. What is the pt actual rate demand?

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Tidal Volume or Pressure setting

• Maximum volume/pressure to achieve good
  ventilation and oxygenation without producing
  alveolar overdistention
• Max cc/kg? 10 cc/kg
• Some clinical exceptions

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Inspiratory flow

• Varies with the Vt, IE and RR
• Normally about 60 l/min
• Can be majored to 100- 120 l/min

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IE Ratio

• 12
• Prolonged at 13, 14,
• Inverse ratio

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FIO2

• The usual goal is to use the minimum Fio2
  required to have a PaO2 gt 60mmhg or a sat gt90
• Start at 100
• Oxygen toxicity normally with Fio2 gt40

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Inspiratory Trigger

• Normally set automatically
• 2 modes
• Airway pressure
• Flow triggering

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Positive End-expiratory Pressure (PEEP)

• What is PEEP?
• What is the goal of PEEP?
• Improve oxygenation
• Diminish the work of breathing
• Different potential effects

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PEEP

• What are the secondary effects of PEEP?
• Barotrauma
• Diminish cardiac output
• Regional hypoperfusion
• NaCl retention
• Augmentation of I.C.P.?
• Paradoxal hypoxemia

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PEEP

• Contraindication
• No absolute CI
• Barotrauma
• Airway trauma
• Hemodynamic instability
• I.C.P.?
• Bronchospasm?

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PEEP

• What PEEP do you want?
• Usually, 5-10 cmH2O

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Monitoring of the patient
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Look at your patient

• Question your pt
• Examine your pt
• Monitor your pt
• Look at the synchronicity of your pt breathing

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Pressures
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Compliance pressure (Pplat)

• Represent the static end inspiratory recoil
  pressure of the respiratory system, lung and
  chest wall respectively
• Measures the static compliance or elastance

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Pplat

• Measured by occluding the ventilator 3-5 sec at
  the end of inspiration
• Should not exceed 30 cmH2O

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Peak Pressure (Ppeak)

• Ppeak Pplat Pres
• Where Pres reflects the resistive element of the
  respiratory system (ET tube and airway)

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Ppeak

• Pressure measured at the end of inspiration
• Should not exceed 50cmH2O?

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Auto-PEEP or Intrinsic PEEP

• What is Auto-PEEP?
• Normally, at end expiration, the lung volume is
  equal to the FRC
• When PEEPi occurs, the lung volume at end
  expiration is greater then the FRC

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Auto-PEEP or Intrinsic PEEP

• Why does hyperinflation occur?
• Airflow limitation because of dynamic collapse
• No time to expire all the lung volume (high RR or
  Vt)
• Expiratory muscle activity
• Lesions that increase expiratory resistance

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Auto-PEEP or Intrinsic PEEP

• Auto-PEEP is measured in a relaxed pt with an
  end-expiratory hold maneuver on a mechanical
  ventilator immediately before the onset of the
  next breath

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Auto-PEEP or Intrinsic PEEP

• Adverse effects
• Predisposes to barotrauma
• Predisposes hemodynamic compromises
• Diminishes the efficiency of the force generated
  by respiratory muscles
• Augments the work of breathing
• Augments the effort to trigger the ventilator

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Different types of patient
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COPD and Asthma

• Goals
• Diminish dynamic hyperinflation
• Diminish work of breathing
• Controlled hypoventilation (permissive
  hypercapnia)

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Diminish DHI

• Why?

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Diminish DHI

• How?
• Diminish minute ventilation
• Low Vt (6-8 cc/kg)
• Low RR (8-10 b/min)
• Maximize expiratory time

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Diminish work of breathing

• How
• Add PEEP (about 85 of PEEPi)
• Applicable in COPD and Asthma.

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Controlled hypercapnia

• Why?
• Limit high airway pressures and thus diminish the
  risk of complications

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Controlled hypercapnia

• How?
• Control the ventilation to keep adequate
  pressures up to a PH gt 7.20 and/or a PaCO2 of 80
  mmHg

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Controlled hypercapnia

• CI
• Head pathologies
• Severe HTN
• Severe metabolic acidosis
• Hypovolemia
• Severe refractory hypoxia
• Severe pulmonary HTN
• Coronary disease

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A.R.D.S.

• Ventilation with lower tidal volume as compared
  with traditional volumes for acute lung injury
  and the ARDS
• The Acute Respiratory Distress Syndrome Network
• N Engl J Med 20003421301-08

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Methods

• March 96 March 99
• 10 university centers
• Inclusion
• Diminish PaO2
• Bilateral infiltrate
• Wedge lt 18
• Exclusion
• Randomized

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Methods

• A/C 28d or weaning
• 2 groups
• 1. Traditional Vt (12cc/kg)
• 2. Low Vt (6cc/kg)
• End point
• 1. Death
• 2. Days of spontaneous breathing
• 3. Days without organ failure or barotrauma

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Results

• The trails were stopped after 861 pt because of
  lower mortality in low Vt group

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Trouble Shooting
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Trouble Shooting

• Doctor, doctor, his pressures are going up!!!
• What is your next step?

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Trouble Shooting

1. Call the I.T., he will take care of it!
2. Where is the staff?
3. I dont know this pt, and run!
4. Ask which pressure is going up

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Trouble Shooting

• Ppeak is up
• Look at your Pplat

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Trouble Shooting

• If your Pplat is high, you are faced with a
  COMPLIANCE problem
• If your Pplat is N, you are faced with a
  RESISTIVE problem
• DD?

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Trouble Shooting

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Trouble Shooting

• Doctor, doctor, my patient is very agitated!
• What is your next step?

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Trouble Shooting

1. Give an ativan to the nurse!
2. Give haldol 10mg to the patient!
3. Take 5mg of morphine for yourself!
4. Look at your pt!

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Trouble Shooting

• At the time of intubation, fighting is largely
  due to anxiety
• But what do you do if pt is stable and then
  becomes agitated?

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Trouble Shooting

1. Remove pt from ventilator
2. Initiate manual ventilation
3. Perform P/E and assess monitoring indices
4. Check patency of airway
5. If death is imminent, consider and treat most
   likely causes
6. Once pt is stabilized, undertake more detailed
   assessement and management

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Trouble Shooting
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Conclusion