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27/01/2019
1
Ventilatory supportOxygen to NIV
Dr Henry Bettinson
Consultant in Respiratory and Intensive Care Medicine
Oxford University Hospitals
Aims
• Two cases
• Oxygen Therapy
– Controlled vs Uncontrolled
– High flow (nasal) oxygen
• Continuous Positive Airways Pressure
• Non-invasive Ventilation
Case 1
• 63 year old male
• Presented with increased breathlessness
• Background
– Type 2 diabetes mellitus
– Panic attacks
– COPD
• 100 pack years
• ET 250 yards
• No previous hospital admissions
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Case 1
• Increasing breathlessness over one week
• On admission breathless at rest
• Minimal white sputum
• On examination– Cyanosed
– Using accessory muscles
– Speaking in sentences
– Widespread wheeze
– SpO2 92% on FiO2 0.24
– HR 70 / min bounding BP 187/85 mmHg
– No oedema
Case 1
• CXR
Case 1
• ABG on FiO2 0.24
– pH 7.32
– PaCO2 7.48
– PaO2 7.66
– HCO3 25.4
– BE 1.5
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Case 1
• Initial treatment– Prednisolone
– Nebulised salbutamol and ipratropium
– Controlled oxygen therapy
• ABG after 3h unchanged
• ABG after 5h
• FiO2 0.24– pH 7.28
– PaCO2 7.62
– PaO2 8.21
– HCO3 23.2
– BE -1.2
Case 1
• Aminophylline commenced
• ABG after 7h
• FiO2 0.24
– pH 7.25
– PaCO2 7.30
– PaO2 10.1
– HCO3 21.0
– BE -4.0
Case 1
• NIV commenced– 12/6 FiO2 0.25
• ABG after 5h– pH 7.37
– PaCO2 6.21
– PaO2 9.24
– HCO3 25.4
– BE -1.1
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Mortality COPD
4000 patients
4% in-hospital mortality
22% mortality survivors at 1 year
Mortality in COPD
Plant PK et al Early Use of Non-invasive ventilation for acute exacerbations of COPD Lancet 2000;355:1931
Mortality COPD
• Mortality of patients undergoing NIV in
COPDClin Respir J. 2019 Jan 19. doi: 10.1111/crj.12994. [Epub ahead of print]
Temporal trends in survival following ward-based NIV for acute hypercapnic
respiratory failure in patients with COPD.
Trethewey SP1, Edgar RG2,3, Morlet J1, Mukherjee R1, Turner AM1,3
• Retrospective cohort study
– 547 pts 2x6 year cohorts 2004 and 2013
– First episode ward-based NIV
– Mortality 17% and 20%
– No difference in intubation, ICU or ceilings of care between
cohorts
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Case 2
• 78 year old female
• Retired nurse
• Background
– Mild interstitial lung disease
– Hypertension
– Unlimited exercise capacity
Case 2
• ‘Cold’ for one week
• Day before admission diarrhoea and
vomiting
• Treated with imodium and rehydration by
GP
• Night before admission breathlessness
• Morning of admission Temp 39°C
Case 2
• On examination
– Temp 38°C
– HR 105 BP 78/53 mmHg HS normal
– SpO2 97% on 15L O2
– RR 26 Coarse crackles throughout
– Abdo soft, non-tender. Bowel sounds present
– Alert and orientated
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Case 2
Case 2
• ABG
– pH 7.14
– PCO2 6.46
– PO2 7.90
– HCO3 15
– BE -10.9
– Lac 3.2
Case 2
• Diagnosis:
• Initial treatment– Fluids 4.5L crystalloid
– IV augmentin, gentamicin and clarithromycin
• ABG after 3h 15L/min O2
– pH 7.22
– PCO2 6.5
– PO2 9.1
– HCO3 19
– BE -5.5
– Lac 3.6
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Case 2
• High Flow Nasal Oxygen commenced
– 60 L/min FiO2 0.8
• 2h later
– pH 7.35
– PaCO2 6.0
– PaO2 9.16
– HCO3 21
– BE -3
Case 2
• Initially stabilized
• Reduction in FiO2 to 0.4 over next 2 days
• Sudden desaturation to 60% on 3rd day
• CTPA no PE. Increasing bibasal
consolidation
• 3x 1g Methylprednisolone
• No significant improvement over next
week
Case 2
• Patient and family discussion
• Palliative measures instituted
• HFNO weaned once no apparent distress
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Mortality exacerbation of IPF
• Prognosis dependent on extent of pre-
existing disease and spirometry
• 3 month mortality 55% vs 81%Kishaba T, Tamaki H Shimaoka Y et al. Staging of acute exacerbation in patients with
idiopathic pulmonary fibrosis Lung 2014;192:141-9
• Systematic review
• 1 month mortality 60%Agarwal J, Jindal SK. Acute exacerbation of idiopathic pulmonary fibrosis: a systematic
review Eur J Intern Med 2008;19:227-35
Oxygen Guidelines
Aims of emergency
oxygen therapy
• To correct or prevent potentially harmful
hypoxaemia
• To alleviate breathlessness if hypoxaemic
Oxygen has no effect on breathlessness if the oxygen saturation
is normal
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Oxygen Guideline
• Prescription by target saturation
– 94%-98% for most patients
– 88%-92% for patients with or at risk of type 2
respiratory failure
• Administer oxygen to achieve target saturation
Oxygen Guideline
• Monitor oxygen saturation and titrate to keep in target range
• Taper oxygen dose and stop when stable
Oxygen guidelines
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NEWS2
Exposure to high concentrations of
oxygen may be harmful
• Absorption atelectasis even at FIO2 30-50%
• Intrapulmonary shunting
• Post-operative hypoxaemia
• Risk to COPD patients
• Coronary vasoconstriction
• Increased Systemic Vascular Resistance
• Reduced Cardiac Index
• Possible reperfusion injury post MI
• Worsens systolic myocardial performance
• Oxygen therapy INCREASED mortality in non-hypoxic patients with mild-moderate stroke
Upper limit of 98% for most patients
Harten JM et al J Cardiothoracic Vasc Anaesth 2005; 19: 173-5
Kaneda T et al. Jpn Circ J 2001; 213-8
Frobert O et al. Cardiovasc Ultrasound 2004; 2: 22
Haque WA et al. J Am Coll Cardiol 1996; 2: 353-7
Thomaon aj ET AL. BMJ 2002; 1406-7
Ronning OM et al. Stroke 1999; 30
Fallacies regarding Oxygen Therapy
“Routine administration of supplemental
oxygen is useful, harmless and clinically
indicated”
• Little increase in oxygen-carrying capacity
• Renders pulse oximetry worthless as a measure of ventilation
• May prevent early diagnosis & specific treatment of hypoventilation
This guideline only recommends supplemental oxygen when SpO2 is below the target range
or in critical illness or CO Poisoning
John B Downs MD Respiratory care 2003;48:611-20
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What is a safe lower Oxygen
level in acute COPD?
• In acute COPD
PaO2 above 6.7 kPa
will prevent death
SpO2 above about 88% SaO
2
mmHg
PaO2
OxyHaemoglobin Dissociation Curve
Minimum SpO2 of 88% for most COPD
patients
Murphy R, Driscoll P, O’Driscoll R Emerg Med J 2001; 18:333-9
Devices
• Non re-breathing Reservoir
Mask.
• Critical illness / Trauma
patients.
• Post-cardiac or respiratory
arrest.
• Delivers O2 concentrations
60%-80% or above
• Effective for short term
treatment.
High Concentration Reservoir Mask
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Nasal Cannulae
• Recommended in the Guideline as suitable for most patients with both type I and II respiratory failure.
• 2-6L/min gives approx 24-50% FIO2
• FiO2 depends on oxygen flow rate and patient’s minute volume and inspiratory flow and pattern of breathing.
• Comfortable and easily tolerated
• No re-breathing
• Low cost product
• Preferred by patients (vs simple mask)
Simple face mask(Medium concentration,
variable performance)
• Used for patients with type I respiratory failure.
• Delivers variable O2 concentration 35%-60%.
• Low cost product.
• Flow 5-10 L/min
Flow must be at least 5 L/min to avoid CO2 build up and resistance to breathing
(although packaging may say 2-10L)
Venturi or Fixed Performance Masks
Aim to deliver constant oxygen concentration
within and between breaths.
24-40% Venturi Masks operate accurately
A 60% Venturi mask gives ~50% FIO2
With TACHYPNOEA (RR >30/min) the oxygen
supply should be increased by 50%
Increasing flow does not increase oxygen
concentration
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Operation of Venturi valve
O2
O2
+
Air
Air
Air
For 24% Venturi mask, the typical oxygen flow of 2 l/min gives a total gas flow of
51 l/min
For 28% Venturi mask, 4 l/min oxygen flow, gives a total gas flow of 44
l/min(Table 10.2)
Oxygen Flow Meter
The centre of the ball indicates the correct flow rate.
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2
1
3
2
1
This diagram illustrates the correct
setting of the flow meter to deliver
a flow of 2 litres per minute
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High flow oxygen
High flow oxygen interfaces
High flow oxygen
• Advantages
– Patient comfort
– Permits controlled high flow oxygen delivery
– Matches patient’s peak inspiratory flow
– Delivers some CPAP/ PEEP
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High flow oxygen
• Disadvantages
– Airvo requires electricity supply
– Not portable
– MR850 system noisy
– Risk of pressure sores with prolonged use
High flow oxygen
• Disadvantages
– Second O2 point necessary for using other
devices eg nebulisers
– Risk of humidification chamber running dry
– Increased staff training necessary
– May prolong terminal phase of illness
High flow oxygen
• Indications– Type 1 respiratory failure
– Type 2 respiratory failure where accurately titrated
humidified O2 is necessary
– Pre and post extubation
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High flow oxygen
• Indications– Weaning from NIV or CPAP
– Claustrophobia to O2 masks
– Tracheostomy patients
– Increased humidifcation to help with sputum
clearance
High flow oxygen
• Contraindications
– Nasal septal defects
– Epistaxis
– Severe facial injuries
– Base of skull fracture
High flow oxygen
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High flow oxygen
• 26 ICUs
• 310 patients
• HFNO vs STD vs NIV
• Primary outcome intubation rate
• 38% vs 47% 50%
• HR death 2.01 standard vs HFNO
• HR death 2.5 NIV vs HFNO
High flow oxygen
• Management of HFNO in palliation
– Use not recommended routinely
– Weaning/ withdrawal may be indicated
– Management depends on time-scale
• Involve patients and families where possible
• Discuss balance of benefits and harms
• Explain symptom management
• Ensure good symptomatic relief prior to any
weaning
OUHFT O2 Prescription and Administration Policy Jan 2019
Types of NIV
• CPAP
• Non-invasive ventilation
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CPAP
Normal CPAP
Inspiration
Inspiration
ExpirationPaw
0
Paw
0
5
cmH2O cmH2O
Expiration
t t
NIV
Inspiration
ExpirationPaw
0 Inspiration
Paw
0
Expiration
4
cmH2O cmH2O
t t
CPAP - indications
• Type I Respiratory failure
– Unresponsive to conventional management
• Pneumonia
• PCP
• Pulmonary oedema
• Acute lung injury
• Post-operative atelectasis
• Obstructive Sleep Apnoea
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CPAP – how does it work?
• P-V Curves
Pressure
Volume Inspiration
Expiration
CPAP – how it works (1)
• Operating at higher functional residual
capacity
• On straight-line part of curve
• Decreased work of breathing
CPAP – how it works (2)
• Improves ventilation – perfusion matching
– Shunting with some blood going to under-
ventilated areas
70%96%
96%
96%
70%
96%
83%
70%QT
QTQs
QT-QS
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CPAP – evidence in pulmonary
oedema
CPAP vs Standard
Reduces Intubation
RR 44%
NNT=7
Bilevel vs Standard
Reduces Intubation
RR 50%
NNT=8
CPAP vs Bilevel
No difference
CPAP vs Standard
Reduces Mortality
RR 59%
NNT=11
Bilevel vs Standard
Reduces Intubation
RR 50%
NNT=8
CPAP vs Bilevel
No difference
Intubation Rate Mortality
Peter 2006 Lancet 367:1155
NIV in pulmonary oedema -3CPO
3CPO
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3CPO
• No effect on 7 day mortality
• No effect on rates of intubation
• Drop in PaO2 at 1h
• Decrease in treatment failures
• Faster resolution of symptoms
• Faster resolution of physiology
3CPO
• Intention to treat analysis
• Crossover
– ? Type 2 error
• 10% overall mortality
• Low rates of intubation
• 2h in emergency departments
– Duration of treatment?
– 24h mortality more appropriate?
• Not treating underlying cause of heart failure
Cochrane review 2008
• 21 studies 1071 (3-120) patients
• Improvement of resp rate
• No difference in oxygenation
• Decreased intubation (RR 0.53, CI 0.34-0.83, NNT 8)
• Decreased mortality (RR 0.62, CI 0.45-0.84, NNT 14)
• Decreased ICU LOS (1d), but not hospital
• No increase in acute MI (RR 1.24, CI 0.79-1.95)
• Trend to increased adverse events– Skin damage
– Gastric distension
• No additional benefit of Bilevel vs CPAP
Vital 2008 Cochrane database
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NIV
• Synonyms
– BiPAP Bilevel positive airway pressure
– PS Pressure support
– NIPPy Non-invasive positive pressure
NIV
• How does it work?
– PaCO2 α 1/ minute ventilation
– In COPD ventilation wasted in dead-space
– Impaired ventilation-perfusion matching
COPD pathophysiology
• Obstructed alveoli –
chronic bronchitis
• Gas trapping –
prolonged time
constants and
intrinsic PEEP
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COPD pathophysiology
• Flat diaphragm poor mechanical advantage
• Reduced tidal volume with rapid breathing -
• Increased VD/ VT ratio
• Large intrathoracic pressure swings
• Increased work of breathing
NIV in COPD
• Deeper breaths for less effort
• Applied expiratory pressure decreases
dynamic hyperinflation
• Better ventilation – perfusion matching
NIV in COPD
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NIV Indications
• Clear evidence
– Acute exacerbation of COPD
– Kyphoscoliosis and other chest wall deformity
– Neuromuscular weakness
– Bridge to transplant in cystic fibrosis
• Less clear evidence
– Pneumonia
– Acute respiratory distress syndrome
– Chronic heart failure
NIV in acute exacerbations of
COPD
• 14 studies in meta-analysis
– 7 ICU based
– 5 ward based
– 2 unspecified
• Multi-national and often multi-centre
– UK landmark study Plant 2000 14 UK centres
• 118 in each arm
• Mortality difference 10% vs 20% (p=0.05)
• Intubation difference 15% vs 27% (p=0.02)
• Faster improvements in respiratory rate and pH
Treatment failure
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Mortality
Intubation
Mortality according to pH
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Success or failure?
Success
• PaCO2 6-13 KPa
• pH >7.3
• Less severe A-a gradient
• Good level of consciousness
• Younger
• Minimal leaks
• Tolerance
• Rapid improvement in physiological parameters
Failure
• Confusion/ ↓ LOC
• >1 organ failure
• Copious respiratory secretions
• Pneumonia/ ARDS as underlying diagnosis
• Poor nutritional status
• Edentulous
Location?
• Respiratory ward?
– 236 patients Leeds and surrounding DGHs
– Intubation criteria reached in 15% NIV vs 27%
controls
– Lower in-hospital mortality rate
But
• For severely acidotic on ward benefit marginal
• No titration of inspiratory pressures
Plant Lancet 2000 355: 1931
Location
• ER?
– Small studies in 1990s suggested not
– Concerns over delayed intubation
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Interfaces
NIV for other indications
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CPAP in chronic heart failure
• Possibly if additional
OSA
• No deaths in 14
treated patients
Questions
?
Summary
• Oxygen
– Prescription
– Administration
• Indications and evidence
• Controlled
• High flow
• CPAP and NIV
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