Less is more in: Emergency Oxygen Therapy

Transcription

1 Less is more in: Emergency Oxygen Therapy Dr Ronan O Driscoll Consultant Respiratory Physician Salford Royal University Hospital Salford M6 8 HD ronan.o.driscoll@srft.nhs.uk

2 Oxygen is the most commonly used drug in emergency medicine 34% of emergency ambulance patients receive oxygen Oxygen is used in about 2 million ambulance journeys in the UK each year

3 Oxygen in Hospital 15-17% of UK hospital patients were receiving oxygen during BTS audits About 18,000 people every day More than 2 million per year

4 Oxygen saves lives But too much oxygen may cause death Essential in severely ill patients with low blood oxygen levels High concentration oxygen probably causes >1,000 avoidable COPD deaths per year in the UK >100,000 COPD admissions per annum in UK with 7.5% mortality: Mortality 9% on high concentration O2 but 4% with controlled O2 Hyperoxaemia is linked to increased risk of death in strokes, ICU patients and survivors of cardiac arrest

5 Chaos reigned until 2008 Most patients were given too much oxygen And there was disagreement about how much oxygen to give Oxygen was rarely prescribed 68% of UK hospital patients who were using oxygen in 2008 had no prescription and most prescriptions were incomplete Doctors and nurses had very little knowledge about safe use of oxygen and many false beliefs

6 UK Emergency Oxygen Guideline published 2008 The Solution Endorsed or supported by 21 other Societies and Colleges

7 R O'Driscoll AAGBI WSM 2012

8 Key Principles of the Guideline Oxygen is a treatment for Hypoxemia (Giving oxygen does not relieve breathlessness or increase the oxygen supply to vital organs if the patient s oxygen level is normal to start with) Aim for a normal or near-normal oxygen saturation level for most patients (94-98%) Aim at a lower level for (88-92%) for those at risk from higher doses of oxygen Doctors prescribe a target range Nurses adjust equipment and flow rates to achieve the desired target range

9 What is normal and what is dangerous?

10 Normal Range for Oxygen saturation Normal range for healthy young adults is approximately 96-98% Slight fall with advancing age SpO2 ~0.5% lower above age 70

11 Effects of sudden hypoxia (e.g Removal of oxygen mask at altitude or in a pressure chamber) Impaired mental function; Onset at mean SaO 2 64% No evidence of mental impairment above SaO 2 of 84% Loss of consciousness: Onset at mean saturation of 56% Organ damage: Brain tissue is the most sensitive Death: Risk depends on extent and speed of onset and duration of hypoxia (no experimental studies in man) Test Pilots in decompression chambers do not experience breathlessness when the oxygen tension is lowered

12 Defining safe lower and upper limits of oxygen saturation

13 What is the minimum arterial oxygen level recommended in acute illness Target oxygen Saturation Critical care consensus guidelines Minimum 90% Surviving sepsis campaign Aim at 88-95% But these patients have intensive levels of nursing & monitoring BTS guideline recommends a minimum of 94% for most patients combines what is near normal and what is safe

14 Pulmonary Oxygen Toxicity Lorrain-Smith Effect

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16 Exposure to high concentrations of oxygen may be harmful Absorption Atelectasis even at FIO % 1 Intrapulmonary shunting and post-operative hypoxaemia (on return to room air) 1 Risk to COPD patients 2 Coronary vasoconstriction 3 Increased Systemic Vascular Resistance 3 Reduced Cardiac Index after coronary bypass surgery 4 Possible reperfusion injury post Myocardial Infarction 5 Oxygen therapy increased mortality in non-hypoxic patients with mild-moderate stroke 6 Hyperoxaemia was associated with increased mortality in survivors of cardiac arrest 7 Hyperoxaemia was associated with increased mortality in the first 24 hours on ICU 8 BTS guideline recommends an upper limit of 98% for most patients. Combination of what is normal and safe

17 What is a safe lower Oxygen level in acute COPD? OxyHaemoglobin Dissociation Curve In acute COPD po 2 above 6.7 kpa or 50 mm Hg will prevent death SaO 2 above about 85% (Keep SpO 2 88% to allow for oximeter error and ensure SaO2 >85% ) SaO 2 mmhg PaO 2 Murphy R, Driscoll P, O Driscoll R Emerg Med J 2001; 18:333-9 BTS guideline recommends a minimum saturation of 88% for most COPD patients

18 What is a safe upper limit of oxygen target range in acute COPD? 47% of 982 patients with exacerbation of COPD were hypercapnic on arrival in hospital 20% had Respiratory Acidosis (ph < 7.35) 5% had ph < 7.25 (and were likely to need ICU care) Most hypercapnic patients with po 2 > 10 kpa were acidotic (equivalent to oxygen saturation of above ~ 92%) i.e. They had been given too much oxygen Plant et al Thorax 2000; 55:550 RECOMMENDED UPPER LIMITS Keep PaO2 below 10 kpa and keep SpO 2 92% in acute COPD

19 Recent clinical evidence Mortality in acute COPD was 9% when high concentration oxygen was given compared with 4% mortality with controlled oxygen (target range 88-92%) 1 Mortality in acute COPD was 11% when >35% oxygen was given but 7% when lower doses of oxygen were used 2 Need for ventilatory support; 22% v 9% 2 1. Austin MA, et al. BMJ Oct 18;341:c5462. doi: /bmj.c Roberts CM et al. Thorax 2011: 66: 43

20 Recommended target saturations The target ranges are a consensus agreement by the guidelines group and the endorsing colleges and societies Rationale for the target saturations is combination of what is normal and what is safe Most patients 94-98% Risk of hypercapnic respiratory failure 88 92%* *Or patient specific saturation on Alert Card

21 Oxygen saturation on air and survival for 37,593 acute medical admissions Smith GB et al. Resuscitation 2012 ;83:1201-5

22 Oxygen saturation on air and survival for 37,593 acute medical admissions Smith GB et al. Resuscitation 2012 ;83: Our findings suggest that the BTS should consider changing its target saturation for actively treated patients not at risk of hypercapnic respiratory failure to 96-98% Thus giving Oxygen to an extra 20% of all medical patients

23 Would normalising the respiratory rate with morphine and normalising the heart rate with beta blockers and increasing blood oxygen content by 2% be expected to save lives? BUT. There was an average 2% fall in mean and median saturation above age 65 (and age is a strong predictor of death) Hypoxaemia is a marker of disease severity just like tachycardia and tachypnoea

24 Why is oxygen used?

25 Aims of emergency oxygen therapy To correct / prevent potentially harmful hypoxaemia To alleviate breathlessness (only if hypoxaemic) Oxygen has no effect on breathlessness if the oxygen saturation is normal

26 Five common beliefs (But wrong in most circumstances) Routine administration of supplemental oxygen is useful, harmless and clinically indicated Giving oxygen is the most effective way to increase oxygen delivery to the tissues Oxygen relieves breathlessness at normal oxygen saturations High concentration oxygen is safe in all emergency situations apart from COPD Many patients are at risk from hypoxaemia and only a few near terminal COPD patients are at risk from hyperoxaemia

27 Prophylactic oxygen Less or More? Little increase in oxygen-carrying capacity (e.g. 3% rise in blood oxygen content at SpO 2 97%) Renders pulse oximetry worthless as a measure of ventilation May prevent early diagnosis & specific treatment of hypoventilation

28 Perioperative Oximetry Data from 23,000 patients in Cochrane Review Hypoxaemia was 1.5 to 3 times less common amongst patients monitored with oximetry if the results were made available to the clinicians More oxygen was given to these patients compared with patients where the oximetry reading was concealed from the clinicians No difference observed in complications or mortality i.e. Correcting modest hypoxaemia may confer no benefit to patients although clinicians who saw oximeter results believed that they had prevented harm to several patients

29 Five common beliefs (But wrong in most circumstances) Routine administration of supplemental oxygen is useful, harmless and clinically indicated Giving oxygen is the most effective way to increase oxygen delivery to the tissues Oxygen relieves breathlessness at normal oxygen saturations High concentration oxygen is safe in all emergency situations apart from COPD Many patients are at risk from hypoxaemia and only a few near terminal COPD patients are at risk from hyperoxaemia

30 Oxygen therapy is only one element in the resuscitation of a critically ill patient The oxygen carrying power of blood may be increased by Safeguarding the airway Enhancing circulating volume Correcting severe anaemia Enhancing cardiac output Avoiding/Reversing Respiratory Depressants Increasing Fraction of Inspired Oxygen (FIO 2 ) Establish the reason for Hypoxaemia and treat the underlying cause (e.g Bronchospasm, LVF etc) Patient may need, CPAP or NIV or Invasive ventilation

31 Five common beliefs (But wrong in most circumstances) Routine administration of supplemental oxygen is useful, harmless and clinically indicated Giving oxygen is the most effective way to increase oxygen delivery to the tissues Oxygen relieves breathlessness at normal oxygen saturations High concentration oxygen is safe in all emergency situations apart from COPD Many patients are at risk from hypoxaemia and only a few near terminal COPD patients are at risk from hyperoxaemia

32 Does oxygen relieve breathlessness in COPD and in Palliative Care? Short Burst Oxygen Therapy administered after exercise does not relieve breathlessness in non-hypoxaemic patients with COPD 1 Nasal oxygen did not relieve breathlessness in palliative care patients with PaO2 > 7.3 kpa 2

33 Five common beliefs (But wrong in most circumstances) Routine administration of supplemental oxygen is useful, harmless and clinically indicated Giving oxygen is the most effective way to increase oxygen delivery to the tissues Oxygen relieves breathlessness at normal oxygen saturations High concentration oxygen is safe in all emergency situations apart from COPD Many patients are at risk from hypoxaemia and only a few near terminal COPD patients are at risk from hyperoxaemia

34 Patients at risk of hypercapnia/acidosis due to high concentration oxygen (even with PaO 2 in the normal range) Chronic hypoxic lung diseases COPD Severe Chronic Asthma Bronchiectasis / Cystic Fibrosis Chest wall disease Kyphoscoliosis Thoracoplasty Neuromuscular disease Obesity hypoventilation

35 Patients at potential risk from hyperoxaemia COPD patients and other groups shown in the previous slide are at risk if oxygen saturation is elevated beyond 92% are at increased risk if SpO 2 is raised above 98% Myocardial Infarction 1 Increased mortality in non-hypoxic patients with mildmoderate stroke randomised to oxygen (controlled trial) 2 Hyperoxaemia was associated with increased mortality in survivors of cardiac arrest 3 Hyperoxaemia was associated with increased mortality in the first 24 hours on ICU 4

36 Hospital Mortality Hyperoxia 63% Normoxia 45% Hypoxia 57%

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39 Mortality for each quintile Mortality according to calculated oxygen saturation level Adapted from dejonge et al Critical Care 2008; Overall mortality 31% <93% % % % >98.8% Estimated oxygen saturation based on conversion from PaO2 Adapted from table 2 in de-jonge et al Critical Care 2008, 12:R156 Multivariate regression analysis of in-hospital mortality based on arterial oxygen tension in first 24 hours on ICU Overall hospital mortality for 36,307 consecutive ICU patients was 31%

40 Five common beliefs (But wrong in most circumstances) Routine administration of supplemental oxygen is useful, harmless and clinically indicated Giving oxygen is the most effective way to increase oxygen delivery to the tissues Oxygen relieves breathlessness at normal oxygen saturations High concentration oxygen is safe in all emergency situations apart from COPD Many patients are at risk from hypoxaemia and only a few near terminal COPD patients are at risk from hyperoxaemia

41 Audit of 7956 blood gas samples at one hospital over one year 10% of samples outside A&E had Type 1 respiratory failure with PO2 <8 kpa and normal or low PCO2 (30% of A&E samples showed Type 1 Failure) 22% had Type 2 respiratory failure (including 7% with respiratory acidosis) 24% of patients who had blood gases sampled had risk factors for Type 2 Respiratory Failure and 73% of these samples had saturation >92% 26% of samples had saturation >98%

42 Oxygen prescription Model for oxygen section in hospital prescription charts DRUG OXYGEN (Refer To Trust Oxygen Policy) Circle target oxygen saturation 88-92% 94-98% Other STOP DATE Starting device/flow rate PRN / Continuous Tick if saturation not indicated PHARM (Saturation is indicated in almost all cases except for palliative terminal care) SIGNATURE / PRINT NAME DATE ddmmyy

43 What device and flow rate should you use in each situation?

44 Standard Oxygen Therapy 1960s-2008 Acute Patients Stable Patients

45 Oxygen therapy 2008 onwards Critical illness Selected COPD patients Most patients

46 Prescribe to target BTS Recommendations Critical Illness Requiring High Levels of Oxygen Supplementation Serious Illness Requiring Moderate Levels of Oxygen if the Patient is Hypoxaemic COPD and Other Conditions Requiring Controlled or low-dose Oxygen Therapy Conditions for which patients should be monitored closely but oxygen therapy is not required unless the patient is hypoxaemic

47 Some patients need high-dose oxygen to normalise saturation (Usually for short periods of time) Severe Pneumonia Severe LVF Major Trauma Sepsis and Shock Major atelectasis Pulmonary Embolism Exacerbation Lung Fibrosis etc

48 Titrating Oxygen up and down. This table below shows APPROXIMATE conversion values. Venturi 24% (blue) 2-4l/min OR Nasal specs 1L Venturi 28% (white) 4-6 l/min OR Nasal specs 2L Venturi 35% (yellow) 8-10l/min OR Nasal spec 4L Venturi 40% (red)10-12l/min OR Simple face mask 5-6L/min Venturi 60% (green) 15l/min OR Simple face mask 7-10L/min Reservoir mask at 15L oxygen flow seek medical advice I f reservoir mask required seek senior medical Input immediately

49 Monitoring patients Oxygen saturation and delivery system should be recorded on the monitoring chart Delivery devices and/or flow rates should be adjusted to keep oxygen saturation in target range

50 Implementation and Dissemination Incorporation of Emergency Oxygen Guidelines in other Guidelines JRCALC (Joint Royal Colleges Ambulance Liaison Committee) Oxygen Guideline April 2009 BTS Pneumonia Guideline 2009 NICE Guideline for Chest Pain of Recent Onset March 2010 Resuscitation Council (UK) Guideline 2010 European Resuscitation Guideline 2010 BTS-SIGN Asthma Guideline 2011

51 Summary Oxygen is like every other drug Use no more than is necessary If it is used properly for the right indications, it is beneficial and safe Giving oxygen to those who do not need it or giving too much or too little oxygen may cause harm Compared with present practice, it is likely that a reduction in oxygen use will deliver safer care, especially for patients at risk of hypercapnia. Further information at

52 Who was the first person to realise that moderate oxygen may be safer than pure oxygen? Less is More