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

• Ventilator mode
• Respiratory rate
• Tidal volume or pressure settings
• Inspiratory flow
• IE ratio
• PEEP
• FiO2
• 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

• 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

• Call the I.T., he will take care of it!
• Where is the staff?
• I dont know this pt, and run!
• 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

• Give an ativan to the nurse!
• Give haldol 10mg to the patient!
• Take 5mg of morphine for yourself!
• 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

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

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Trouble Shooting
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Conclusion