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CI2 > Mechanical Ventilation & Hyperinflation > Flashcards

Mechanical Ventilation & Hyperinflation Flashcards

1
Q

What are the 2 reasons why patients need mechanical ventilation?

A

Respiratory failure
- Type 1 or 2

Airway protection

  • Intubation due to airway compromise (e.g. stridor)
  • Drug-induced coma
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2
Q

Why do patients with respiratory failure require mechanical ventilation?

A
  1. Pump stops working
    - diaphragm, rib cage, nerves, muscles
    - due to injury/pain or neural defect (e.g. brainstem infarct)
  2. Gas exchange surface compromised
    - needs high level of pressure to guarantee adequate O2 into bloodstream
    - e.g. pneumonia, inflammation
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3
Q

What are the causes of respiratory failure?

A
  • Opioid drug use
  • Cervical spinal cord injury
  • Surgery/general anaesthetic
  • Rib fractures
  • APO
  • PE
  • Post-op atelectasis
  • Pneumonia
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4
Q

What is the function of a ventilator?

A

Inspiratory phase

  • Provides required tidal volume
  • Unloads respiratory muscles
  • Reduces WOB
  • Allows for CO2 removal

Expiratory phase
- Passive but has PEEP at the end of it

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5
Q

What is positive end expiratory pressure (PEEP)?

A

Baseline pressure maintained in the lungs at the end of each exhalation

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6
Q

Why is PEEP important?

A
  • Prevents alveolar collapse (increases FRC)
  • Overcomes resistance of tubing
  • Reduces WOB (increases alveolar compliance)
  • Never wean below 5cm H2O
  • Holds open airways, but doesn’t make you take a breath
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7
Q

What is pressure support?

A

If a patient can start a tiny breath, a ventilator will recognise it & boost it to make it a decent size breath

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8
Q

What is the difference between pressure support & controlled ventilation?

A
  • Support: Patient is in charge of starting the breath

- Controlled: Ventilator is in charge of starting the breath

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9
Q

How does pressure support mode work?

A
  • Baseline PEEP
  • Recognises start of a breath
  • Boosts each spontaneous breath to pre-set pressure
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10
Q

What are the benefits of pressure support?

A
  • Comfortable for patient

- Reduces WOB

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11
Q

What are the two delivery modes of controlled mandatory ventilation (CMV)?

A
  • Pressure controlled: Delivers set number of breaths to pre-set pressure
  • Volume controlled: Delivers set number of breaths to pre-set volume
  • Both ignore patient effort
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12
Q

Why is CMV not commonly used?

A
  • Patients require sedation/paralysis

- If patient wakes up it’s not comfortable or appropriate

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13
Q

What is synchronised intermittent mandatory ventilation (SIMV)?

A
  • Recognises patient effort (no breath-stacking)
  • Gives controlled breaths as a minimum (even if no patient effort)
  • Guarantees ventilation
  • If patient starts spontaneous breathing, recognises these & behaves like pressure support
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14
Q

What are the benefits of SIMV?

A
  • Much more comfortable for patients who have any degree of alertness
  • Good choice for transitional patients (e.g. waking from anaesthetic)
  • Insurance policy: Will breathe even with no patient effort
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15
Q

What are the other less commonly used modes of ventilation?

A
  • Pressure control inverse ratio ventilation
  • Airway pressure release ventilation (APRV)
  • BiLevel ventilation
  • High frequency/oscillation ventilation
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16
Q

What is the meaning of the following terms:

  • PIP
  • ETCO2
  • Vt
  • Tinsp
  • MV
A
  • PIP: Peak inspiratory pressure (PEEP + PS)
  • ETCO2: End-tidal CO2
  • Vt: Tidal volume
  • Tinsp: Inspiratory time (s)
  • MV: Minute ventilation (RR x Vt)
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17
Q

What role do physios have in ventilation?

A
  • Pre-oxygenate prior to suction: 180s of 100% oxygen, then reverts to pre-set FiO2
  • Coach deep breaths (ventilator provides feedback)
  • Switch from one mode to another or increase PEEP (with medical permission)
  • Perform ventilator hyperinflation (VHI)
  • Put ventilator in stand-by mode (turn it off)
  • Measure inspiratory muscle strength
18
Q

What are the complications of mechanical ventilation?

A
  • Impaired V/Q matching
  • Reduced surfactant production: Decreases sigh breaths, increases risk of atelectasis
  • Reduced FRC: increases risk of atelectasis
  • Impaired MC clearance: Drying effects, frequent atelectasis, high risk of pneumonia
19
Q

Why is impaired V/Q matching a complication of mechanical ventilation?

A
  • Positive pressure: Ventilation goes to path of least resistance = airways already open (usually uppermost or non-dependent lung areas)
  • Opposite of spontaneous breathing
  • Increases risk of atelectasis in dependent regions
20
Q

What do the mechanical ventilation complications often lead to?

A
  • Atelectasis/collapse

- Difficulty clearing sputum

21
Q

What are invasively ventilated patients unable to do?

A
  • Truly cough/huff (ETT/trache prevents closure of glottis)
  • Expectorate sputum easily (dependent on suction)
  • Participate in PEP therapy
22
Q

What are some of the things that patients who are awake and invasively ventilated may be able to do?

A
  • Take deep breathes
  • Mobilise

If not, then hyperinflation treatment

23
Q

What are the 2 ways of performing hyperinflation treatment?

A
  • Manual

- Ventilator

24
Q

What is manual hyperinflation (MHI)?

A
  • Delivery of slow, deep inspiration greater than baseline tidal volume up to a PIP of 40cm H2O
  • Followed by inspiratory hold up to 3s
  • Followed by quick, unobstructed expiration
25
Q

What does MHI involve?

A
  • Deep breathing

- Physically disconnecting patient from ventilator & control breathing through resuscitator bag

26
Q

How does MHI work?

A
  • Slow deep inspiration re-expands areas of atelectasis
  • Inspiratory hold recruits lung segments via collateral changes (improved gas exchange & mobilises secretions
  • Quick release increases expiratory flow rates, mimics cough, mobilises secretions from distal to proximal segments
27
Q

What are the indications for MHI?

A
  • Evidence of retained secretions
  • Evidence of collapse/loss of volume
  • Poor lung compliance (stretch produces surfactant)
  • Decreased oxygenation cause by one of the above
28
Q

What are the CIs for MHI?

A
  • Undrained pneumothorax
  • ICC with continuous leak
  • Bronchopulmonary fistula
  • Recent oesophageal/lung surgery
  • Acute respiratory distress syndrome (ARDS)
29
Q

What are the precautions for MHI?

A
  • Unstable CV system
  • Bronchospasm
  • PEEP > 15cm H2O
  • PEEP dependent or high risk of de-recruitment if disconnected from ventilator
  • Pressure support + PEEP >30cm H2O
  • FiO2 >60%
  • PIP >35cm H2O
  • Raised ICP
  • Florid APO
  • Restrictive/obstructive lung disease
  • Significant pulmonary hypertension
  • Right ventricular dysfunction
30
Q

What are the practical tips for safe MHI?

A
  • Ensure bag has a filter attached
  • Attached PEEP valve is patient on PEEP >10cm H2O on ventilator
  • Ensure max flow from wall prior to disconnecting patient from ventilator
  • Slow inspiration, as quick a release as possible
  • Avoid sustained holds if increased intrathoracic pressure
  • Beware of blowing off too much CO2 (check for spontaneous breaths)
31
Q

How can MHI be used to blow off CO2 & reduce ICP?

A
  • CO2 = acid (vasodilator)
  • Increase rate or volume to blow off CO2 & reduce ICP
  • But watch for rebound
32
Q

When is MHI not possible?

A
  • When there is a CI
  • When risks of disconnecting from ventilator don’t outweigh benefit of treatment
    (Even transient loss of PEEP can worsen atelectasis in some patients)

Then consider ventilator hyperinflation

33
Q

What are the benefits of ventilator hyperinflation (VHI)?

A
  • No disconnection from ventilator (no loss of PEEP, no risk of decruitment)
  • Physio provides deep breaths (with a hold) by manipulating ventilator settings
34
Q

What are the risks of prolonged mechanical ventilation?

A
  • Ventilator associated pneumonia (VAP)

- Respiratory muscle weakness (esp > 7 days)

35
Q

What are the risks of failed extubation & reintubation?

A

Increased mortality, duration of ventilation & length of stay (more money)

36
Q

What role do physios have in assessing readiness to extubate?

A
  • Know patients on a daily basis
  • Spend more time with patients
  • Consider global picture (reconditioning, alertness, cooperation/motivation)
37
Q

What does the assessment for extubation include?

A
  • Overall mental capacity (alert, cooperating)
  • Coached ventilatory capacity (reliably take a deep breath on command)
  • Ability to clear secretions independently
  • Secretion load (can it be managed without suction)
38
Q

What do the results of extubation assessment indicate?

A
  • 4/4: Ready to extubate
  • 3/4: Some risks, but likely to succeed
  • 2/4: Borderline, consider carefully (may need extra physio)
  • 1/4: High risk of failure
39
Q

What are the limitations of extubation?

A
  • Neurological patients: May not be alert but may protect airway sufficiently
  • Palliation: One-way extubations
  • Self-extubations (pulling tube out)
40
Q

What did Hodgson et al 2007 find when comparing Laerdal circuit & Mapelson C circuit?

A

MC circuit cleared 0.89 more per treatment, but no effect on oxygen or compliance

CI2 (17 decks)

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