OXYGEN THERAPY. Catherine Jones June 2017

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1 OXYGEN THERAPY Catherine Jones June

2 ACKNOWLEDGEMENT 2

3 LEARNING OUTCOMES 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

4 WHAT DOES OXYGEN DO? Aerobic Metabolism: OXYGEN + FUEL ENERGY + CARBON DIOXIDE + WATER Anaerobic Metabolism GLUCOSE ENERGY + LACTIC ACID 4

5 CLINICAL FEATURES OF HYPOXAEMIA Altered mental state Dyspnoea, cyanosis, tachypnoea, arrhythmias, coma Hyperventilation when PaO 2 <5.3kPa(SpO2 <72%) Loss of consciousness ~ 4.3 kpa(spo2-56%) Death approximately 2.7 kpa 5

6 ASSESSMENT/MEASUREMENT 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

7 CYANOSIS

8 WHY IS OXYGEN USED? 12/05/2017

9 AIMS OF OXYGEN THERAPY 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 nonhypoxaemic patients 12/05/2017

10 OXYHAEMAGLOBIN DISSOCIATION CYRVE Little increase in oxygen-carrying capacity if SpO 2 is normal BTS (2017)guideline only recommends supplemental oxygen when SpO 2 is below the target range. 10

11 WHAT ARE THE TARGETS? 11

12 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 (FIO 2 ) Establish the reason for Hypoxia and treat the underlying cause (e.g Bronchospasm, LVF etc) 12/05/2017

13 PROBLEMS WITH OXYGEN THERAPY? 13

14 OXYGEN TOXICITY 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

15 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 CO 2 level is elevated (or if it was high in the past) 12/05/2017

16 HIGH CONCENTRATION OXYGEN MAY DOUBLE THE RISK OF DEATH IN ACUTE EXACERBATIONS OF COPD (AECOPD) 16

17 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 12/05/2017

18 DELIVERY & DEVICES 12/05/2017

19 ADMINISTRATION 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?? 19

20 Beware of air outlets They may be mistaken for oxygen outlets Oxygen outlet (Usually white) Air outlet (usually black) Use a cover for air outlets or else remove the flow meter for air when not in use 12/05/2017

21 12/05/2017

22 OXYGEN FLOW METER The centre of the ball indicates the correct flow rate /05/2017

23 High Concentration Reservoir Mask Non re-breathing Reservoir Mask Delivers O 2 concentrations between 60 & 80% or above Variable performance dependent upon mask fit & breathing pattern Effective for short term treatment 12/05/2017

24 NASAL CANNULAE Variable performance 1-6L/min gives approx 24-50% FIO 2 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 12/05/2017

25 SIMPLE FACE MASK Delivers variable O 2 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 CO 2 build up. Not suitable for T2RF 12/05/2017

26 VARIABLE PERFORMANCE DEVICES Oxygen delivery is dependant on patients minute volume (RR X VT) MV = 30 L/min 40 bpm x 740 ml/breath O 2 flow rate = 2 L/min Inspired O 2 concentration = 2 l/min of 100% O L/min air drawn into mask (1x2) + (0.21x28) = FiO 2 of 0.26 (or 26%) 30 L/min

27 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 12/05/2017

28 OPERATION OF VENTURI VALVE Air O 2 O 2 + Air Air 12/05/2017

29 HUMIDIFIED OXYGEN Large volume nebulisationbased 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 12/05/2017

30 TRACHEOSTOMY MASK Neck breathing patients Adjust oxygen flow to maintain target saturation Prolonged oxygen use requires humidification Patients may also need suction to remove airway mucus 12/05/2017

31 OPTIFLOW Delivers heated & humidified high flow oxygen (up to 100%) via nasal cannula. Provides low level of CPAP

32 SUMMARY 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 32

33 ANY QUESTIONS..? 33

34 12/05/2017 EXPOSURE TO HIGH CONCENTRATIONS OF OXYGEN MAY BE HARMFUL Absorption Atelectasis even at FIO % 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 Harten JM et al J Cardiothoracic V Anaesth 2005; 19: Kaneda T et al. Jpn Circ J 2001; Frobert O et al. Cardiovasc Ultras This guideline recommends an upper 2: 22 limit of 98% for most patients Combination of what is normal and safe Haque WA et al. J Am Coll Cardio Thomaon aj ET AL. BMJ 2002; 14 Stub D et a;. Circulation 2015 ; 13 Helmerhorst HJ Crit Care Med Girardis M et al. JAMA 2016; 316:

35 WHAT IS A SAFE LOWER OXYGEN LEVEL IN ACUTE COPD? In acute COPD po 2 above 6.7 kpa or 50 mm Hg will prevent death (SpO 2 above about 85%) SaO 2 OxyHaemoglobin Dissociation Curve Murphy R, Driscoll P, O Driscoll R Emerg Med J 2001; 18:333-9 mmhg PaO 2 This guideline recommends a minimum saturation of 88% for most COPD patients 12/05/2017