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Emergency Oxygen Therapy

Emergency Oxygen Therapy. Is there a problem?. Clinical Case No. 1. 79-year-old female, diabetic, morbidly obese Admitted with ‘ LVF ’ Overnight ‘ Reduced GCS ?cause ’ 15L oxygen via non-rebreathe in situ ABG showed pH 6.9, pCO2 15.9kPa normal range 4.5-6.0kPa

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Emergency Oxygen Therapy

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  1. Emergency Oxygen Therapy Is there a problem?

  2. Clinical Case No. 1 • 79-year-old female, diabetic, morbidly obese • Admitted with ‘LVF’ • Overnight ‘Reduced GCS ?cause’ • 15L oxygen via non-rebreathe in situ • ABG showed pH 6.9, pCO2 15.9kPa normal range 4.5-6.0kPa • Woke up when oxygen removed! • Oxygen prescribed with target SpO2 88-92%, documented in notes • Following morning on AMU GCS 3/15 and 15L NRB back in situ! • Not a candidate for NIV → RIP

  3. Clinical Case No. 2 • 75-year-old male, cervical myelopathy (cord compression due to OA) • Admitted with reduced GCS (9/15) • pH 7.1, pCO2 9.6kPa (respiratory acidosis) • Improved with controlled O2 24-28% • Treated for pneumonia • Became drowsy again with rising pCO2 and low RR • Miotic (small) pupils • Covered in fentanyl patches • Improved once patches removed and naloxone given!

  4. Clinical Case No. 3 • 86-year-old female from RH, osteoporosis • Admitted with pneumonia • Asked to see on AMU because of ‘fitting’ • Hypotensive, myoclonic jerks, bounding pulse • On 10L O2 via NRB since admission • ABG showed pH 7.23, pCO2 12.9kPa • Minimal improvement with reduced FiO2 • Not a candidate for HDU or NIV on the respiratory ward →RIP

  5. Oxygen —there is a problem! Published national audits have shown; • Doctors and nurses have a poor understanding of how oxygen should be used • Oxygen is often given without any prescription • If there is a prescription, it is unusual for the patient to receive what is specified on the prescription • Monitoring of oxygen administration is often poor →OXYGEN IS DANGEROUS NPSA alert 2009

  6. Emergency Oxygen Use in Adult Patients BTS Guideline 2009 • Prescribing by target oxygen saturation • Keeping SpO2 within normal limits • Target SpO2 94-98% for most patients 92-98% if >70 • Target SpO2 88-92% (pO2 6.7-10kPa) for those with or at risk of hypercapnic (high CO2) respiratory failure

  7. Aims of Emergency Oxygen Therapy • To correct or prevent potentially harmful hypoxaemia • To alleviate breathlessness only if hypoxaemic Increasing FiO2 (inspired oxygen concentration) is only one way of increasing overall O2 carrying capacity of blood: • Protect airway • Enhance circulating volume and cardiac output • Correct severe anaemia • Avoid or reverse respiratory depressants e.g. morphine • Treat underlying cause e.g. LVF, asthma

  8. Indications for Emergency Oxygen • SpO2 <94% <88% if risk of hypercapnia • Critical illness e.g. septic shock, major trauma, anaphylaxis, acute LVF during initial ABCDE • Carbon monoxide poisoning irrespective of SpO2

  9. Too much O2 can be harmful… • Risk of hypercapnia (high CO2) in selected patients • some patients with chronic hypercapnia are dependent on hypoxaemia to maintain respiratory drive • Constriction of coronary arteries • high O2 levels INCREASED mortality in survivors of cardiac arrest • Constriction of cerebral arteries • high O2 levels INCREASED mortality in non-hypoxic patients with mild-moderate stroke

  10. Patients at risk of hypercapnia? • COPDnot all patients with COPD —elevated HCO3- on ABG is a useful clue to chronic CO2 retention • Morbid obesity OHS and OSA • Neuromuscular weakness MND, myasthenia, GBS • Chest wall deformity kyphoscoliosis • Reduced conscious level • Morphineand other respiratory sedatives

  11. How should oxygen be delivered to… Critically unwell / severely hypoxaemic patients? • high-concentration reservoir / non-rebreathe mask • delivers 60-80% O2 at 10-15L/min • SHORT-TERM use only • ensure bag is filled with oxygen before attaching to patient • DO NOT turn down oxygen flow below 10L/min

  12. How should oxygen be delivered to… Most other patients? • nasal cannulae / specs • comfortable, well-tolerated, low-cost and no risk of re-breathing • 2-6L/min gives ~24-50% oxygen • concentration actually delivered also depends on patient’s: • tidal volume • respiratory rate patients with COPD tend to breath disproportionately more oxygen than air with every breath → risk of hypercapnia

  13. How should oxygen be delivered to… Patients at risk of hypercapnic respiratory failure? • Venturi / fixed performance masks • increasing oxygen flow does NOT increase FiO2 • accurate between 24-40% • 60% venturi delivers ~50% oxygen • less affected by tidal volume and respiratory rate (useful in COPD)

  14. Monitoring and Titration of O2 ALWAYS • question whether oxygen is actually required and if so, what is the target saturation range • monitor oxygen saturations frequently / continuously • titrate flow rate and / or device up or down until target saturations achieved • use minimum flow rate required • seek to wean off oxygen as soon as possible NEVER • leave patients on high-concentration O2 without repeating ABGs • use non-rebreathe masks with flow rates <10L/min • adjust the flow rate through a Venturi device without changing the mask • suddenly stop high-concentration oxygen in a hypercapnic patient without titrating down first (35%)

  15. BTS National Oxygen Audits Percentage of patients within target range where this was prescribed 69% 9% of patents at risk of iatrogenic hypercapnia due to being >2% above their target range (despite recognised hypercapnic risk)

  16. How can we improve? Nurse-led and delivered process —ask yourself these key questions: • Does this patient actually need oxygen? • check saturations on air oxygen won’t help unless hypoxaemic • only give oxygen if patient is outside of their target range • if in doubt, ask somebody! • Is oxygen prescribed on the drug chart? • immediately ask a clinician to prescribe if not • Which device is best for my patient • nasal cannulae for majority, Venturi mask if risk of hypercapnia • What is the target saturation range and is this being achieved? • titrate oxygen up or down until target SpO2 is achieved

  17. Key Learning Points • Oxygen is a drug —if it’s not prescribed, DON’T GIVE IT except in an emergency —like most drugs, oxygen has the potential to kill • Consider risk of CO2 retention not just COPD patients • Select best device for delivery nasal cannulae > Venturi > non-rebreathe • Frequent monitoring of SpO2 is required in all patients on oxygen • Titrate O2 up or down to achieve target SpO2 94-98% 88-92% if high risk • Avoid hyperoxaemiarisk of hypercapnia and adverse cerebral / coronary effects • Wean down oxygen at the earliest opportunity once stable • NEVER leave patients on high-concentration O2 for prolonged periods

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