catherine oxygen therapy jones june 2017 · 2019. 8. 30. · oxygen therapy is only one element of...
TRANSCRIPT
Catherine
Jones
June 2017
1
OXYGEN THERAPY
2
ACKNOWLEDGEMENT
To revise why Oxygen is important
To identify the indications for Oxygen Therapy
To identify problems with administration of
oxygen
To discuss different devices/interfaces
available in critical care
3
LEARNING OUTCOMES
Aerobic Metabolism:
Anaerobic Metabolism
4
WHAT DOES OXYGEN DO?
OXYGEN + FUEL ENERGY + CARBON DIOXIDE + WATER
GLUCOSE ENERGY + LACTIC ACID
• Altered mental state
• Dyspnoea, cyanosis, tachypnoea, arrhythmias, coma
• Hyperventilation when PaO2 <5.3kPa(SpO2 <72%)
• Loss of consciousness ~ 4.3 kPa(SpO2 -56%)
• Death approximately 2.7 kPa
5
CLINICAL FEATURES OF HYPOXAEMIA
BLOOD GASES: PaO2 and SaO2
PaO2 = Arterial oxygen partial pressure in blood gas specimen
SaO2 =Arterial oxygen saturation measured
OXYGEN SATURATION
Easily measured by pulse oximetry & widely available
SpO2 = Oxygen saturation measured by pulse oximeter
Normal range in healthy adults 96-98%
CYANOSIS
Often not recognised
Absent with anaemia
6
ASSESSMENT/MEASUREMENT OF
HYPOXAEMIA
CYANOSIS
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WHY IS OXYGEN
USED?
• To correct potentially harmful hypoxaemia & support the delivery of oxygen to cells
• To alleviate breathlessness (only if hypoxaemic)
Oxygen has not been proven to have any consistent effect on the sensation of breathlessness in non-hypoxaemic patients
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AIMS OF OXYGEN THERAPY
• Little increase in oxygen-carrying capacity if SpO2 is normal
• BTS (2017)guideline only recommends supplemental oxygen when SpO2 is below the target range.
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OXYHAEMAGLOBIN DISSOCIATION CYRVE
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WHAT ARE THE TARGETS?
OXYGEN THERAPY IS ONLY ONE
ELEMENT OF RESUSCITATION
OF A CRITICALLY ILL PATIENT The oxygen carrying power of blood may be
increased by
• Safeguarding the airway
• Sit the pt up where possible
• Enhancing circulating volume
• Correcting severe anaemia
• Enhancing cardiac output
• Avoiding/Reversing Respiratory Depressants
• Increasing Fraction of Inspired Oxygen (FIO2)
• Establish the reason for Hypoxia and treat the underlying cause (e.g Bronchospasm, LVF etc)
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PROBLEMS WITH
OXYGEN THERAPY?
Production & accumulation of Reactive Oxygen
Species leads to cell damage & necrosis. Cell
death initiates further inflammatory processes
causing further lung damage.
Atelectasis caused by
Inhibits pulmonary surfactant production causing
alveoli to collapse on expiration.
Increased viscosity of tracheal mucous – reduces
clearance & contributes to plugging
Hyperoxic inflammation
OXYGEN TOXICITY
SOME PATIENTS ARE AT RISK OF
CO2 RETENTION AND ACIDOSIS IF
GIVEN HIGH DOSE OXYGEN*
Chronic hypoxic lung disease
COPD
Severe Chronic Asthma
Bronchiectasis / CF
Chest wall disease
Neuromuscular disease
Morbid obesity and OHVS (Obesity
Hypoventilation Syndrome)
*Blood gases should be checked for all such patients if they
need oxygen
*Target saturation range is 88-92% if CO2 level is elevated (or if
it was high in the past) 12/05/2017
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HIGH CONCENTRATION OXYGEN MAY
DOUBLE THE RISK OF DEATH IN
ACUTE EXACERBATIONS OF COPD
(AECOPD)
DANGER OF REBOUND
HYPOXAEMIA
If you find a patient who is severely hypercapnic
due to excessive oxygen therapy……
Do NOT stop oxygen therapy
abruptly
It is safest to step down to 35% oxygen if the
patient is fully alert or provide mechanical
ventilation if the patient is drowsy
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DELIVERY &
DEVICES
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Record delivery system,
flow rate, % & sign on
med chart
Always check expiry
dates on cylinder
Record SpO2
Target for acutely ill….??
Target for hypercapnic
respiratory failure…??
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ADMINISTRATION
Beware of air outlets They may be mistaken for oxygen outlets
Use a cover for air outlets or else remove the flow meter for air when not in use Oxygen outlet
(Usually white) Air outlet (usually black)
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OXYGEN FLOW METER
3
2
1
3
2
1
The centre of the ball indicates the
correct flow rate.
Non re-breathing Reservoir Mask
Delivers O2 concentrations
between 60 & 80% or above
Variable performance dependent
upon mask fit & breathing pattern
Effective for short term treatment
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High Concentration Reservoir Mask
Variable performance
1-6L/min gives approx 24-50%
FIO2
Comfortable and easily tolerated
No re-breathing
Able to eat & drink
Problems with nasal irritation
Don’t use where nose is blocked
or there are polyps
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NASAL CANNULAE
• Delivers variable O2
concentration between 35% &
60%.
• Flow 5-10 L/min – not useful
for pts requiring lower flows
• Low cost product.
• Flow must be at least 5
L/min to avoid CO2 build up.
• Not suitable for T2RF
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SIMPLE FACE MASK
VARIABLE PERFORMANCE DEVICES
• MV = 30 L/min
• 40 bpm x 740 ml/breath
• O2 flow rate = 2 L/min
• Inspired O2 concentration = 2 l/min of 100% O2 + 28 L/min
air drawn into mask
• (1x2) + (0.21x28) = FiO2 of 0.26 (or 26%)
30 L/min
Oxygen delivery is dependant on patients
minute volume (RR X VT)
Venturi or Fixed Performance
Masks (V) • Aim to deliver constant oxygen
concentration
• Venturi Valve delivers fixed %O2
• Increasing flow does not increase
oxygen concentration because it is a
fixed dose device
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OPERATION OF VENTURI VALVE
O2
O2
+
Air
Air
Air
Large volume nebulisation-based humidifiers
1 litre of saline & adjustable venturi valve
Useful for long term oxygen therapy
Always use humidification for tracheostomy
Humidification may be provided by cold or warm humidifiers
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HUMIDIFIED OXYGEN
“Neck breathing patients”
Adjust oxygen flow to maintain
target saturation
Prolonged oxygen use requires
humidification
Patients may also need suction
to remove airway mucus
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TRACHEOSTOMY MASK
OPTIFLOW
Delivers heated & humidified high flow
oxygen (up to 100%) via nasal cannula.
Provides low level of CPAP
New & very comprehensive Emergency O2 Guidelines
our – GO READ THEM!
FiO2 is important but key consideration is target
saturation
Take care when giving O2 to people at risk of AHRF
Lots of devices/interfaces..
Oxygen is a drug & should be treated as such
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SUMMARY
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ANY QUESTIONS..?
EXPOSURE TO HIGH
CONCENTRATIONS OF
OXYGEN MAY BE HARMFUL Absorption Atelectasis even at FIO 2 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 Increased CK level in STEMI and increased infarct size on
MR scan at 3 months Worsens systolic myocardial performance Association of hyperoxaemia with increased mortality in
several ITU studies
This guideline recommends an upper limit of 98% for most patients
Combination of what is normal and safe
• 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
• Stub D et a;. Circulation 2015’; 131: 2143-50
• Helmerhorst HJ Crit Care Med 2015; 43:
1508-19
• Girardis M et al. JAMA 2016; 316: 1583-89
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WHAT IS A SAFE LOWER OXYGEN
LEVEL IN ACUTE COPD?
In acute COPD
pO2 above 6.7 kPa
or 50 mm Hg
will prevent death
(SpO2 above about
85%) S
aO
2
mmHg
PaO2
OxyHaemoglobin Dissociation Curve
This guideline recommends a minimum
saturation of 88% for most COPD patients
Murphy R, Driscoll P, O’Driscoll R Emerg Med J 2001; 18:333-9
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