COPD

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NIV type 2 respiratory failure

• up to 20 mortality during an acute exacerbation
  of COPD with acidosis
• 30 who survive an exacerbation of COPD with
  acidotic type 2 failure die in 18 months
• acidosis predicts mortality and ICU usage
• hypercapneic patients with a higher PaO2 are more
  likely to be acidotic

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Hypercarbia

• PaCO2 gt 6.7kPa (50 mmHg)
• Hypoventilation
• V/Q inequality
• Headache, restless or narcosis
• Flapping tremor, Oedema
• Acidosis

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Effects of Acidosis

• Hyperventilation
• Cardiac dysfunction
• Vasoconstriction
• Cerebral dysfunction
• Renal dysfunction electrolyte changes
• Muscle fatigue

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Some Equations

• PaCO2 is inversely proportional to alveolar
  ventilation
• CO2 H2O H2CO3 H HCO3-
• pH pKA log(HCO3-/CO2)
• Buffering system keeps pH 7.35 7.45
• Kidneys Lungs act together

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NIV

• The delivery of mechanically assisted or
  generated breaths without the placement of an
  artificial airway such as an endotracheal tube or
  tracheostomy, usually via a tightly fitting nasal
  or full face mask.

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NIV Benefits

• increased alveolar ventilation
• decreased work of breathing with resting of
  respiratory muscles
• cheaper than ITU and easy wean
• reduced infection risk
• able to eat and speak

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NIV Dead Space

• Minute Ventilation Tidal Volume x Resp Rate
• Tidal Volume Dead Space Alveolar Space
• Minute Alveolar Ventilation Alveolar Space x
  Resp Rate
• MV (250 250) x 10 5L normal
• MAV 250 x 10 2.5L

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NIV Dead Space

• COPD unwell
• TV 300mls
• MV (250 50) x 30 9L
• MAV 50 x 30 1.5L
• COPD unwell on BIPAP
• TV 350mls
• MV (250 100) x 20 7L
• MAV 100 x 20 2L

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NIV YONIV

• Plant et al Lancet 2000
• Previous randomised controlled trials of NIV,
  conducted in ITU have shown reduced need for
  intubation, shorter stay and reduced hospital
  mortality. Can NIV be used on a DGH general
  medical ward to the same effect

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NIV YONIV

• NIV less likely to be associated with treatment
  failure in the first 2 weeks p0.02
• NIV group less likely to die (at any time during
  admission) p0.05
• NIV group had a more rapid correction of acidosis
  and greater fall in RR plt0.05

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NIV COPDCochrane Review 2004

• Treatment Failure
• RR 0.48 (0.37-0.63)
• NNT 5
• Mortality
• RR 0.52 (0.35-0.76)
• NNT 10
• Intubation
• RR 0.41 (0.33-0.53)
• NNT 4

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NIV COPDCochrane Review 2004

• Length of Stay
• -3.2 days (-4.4 - -2.1)
• Length of ICU Stay
• -4.7 days (-9.6 - 0.2)
• Complications of Treatment
• Risk reduction of 62
• No significant differences found with pH and
  setting of treatment

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NIV why have a service

• Mortality
• Cost saving
• ITU bed usage
• Training issues

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NIV indications

• acute exacerbation of COPD causing acidotic type
  2 respiratory failure, not responding to
  conventional treatment
• no need for urgent intubation or if intubation
  deemed inappropriate

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NIV selection

• Inclusion
• COPD
• pHlt7.35 PaCO2 gt6 kPa post treatment
• resp rate gt 20 bpm
• Exclusion
• immediate intubation required
• CXR pneumothorax, LVF and lobar pneumonia
• vomiting or sputum

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NIV Equipment

• BIPAP machine
• Face mask
• Tubing
• Oxygen if necessary
• Bacterial filter

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NIV Set Up

• Decision re intubation
• HDU v MAU
• IPAP 10
• EPAP 4
• Resp Rate 8 bpm
• Titrate IPAP according to patient comfort
• up to 20

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NIV Monitoring

• Continuos oxygen saturations
• Add oxygen if necessary aiming for saturations
  between 85 - 90
• ABG or capillary blood gases at 1,4 ,12 and 24
  hours
• Respiratory rate
• Tidal volume
• Pressures

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NIV Treatment failure

• Failure to correct acidosis
• Worsening hypoxia
• Increasing confusion/agitation
• Will not wear it
• Pressure areas break down

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NIV Treatment success

• Improved ABG within 4 hours
• reduced respiratory rate increased tidal volume
• less confusion
• Aim to withdraw over 3 days
• Day 1 24hours
• Day 2 18 hours
• Day 3 12 hours

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