DID YOU KNOW:
- Hospital Oxygen is NOT FREE
- Pulse oximeters are key to oxygen therapy. They consist of two light-emitting diodes, one in the red range and one in the infrared range, and a detector. Oxygenated and deoxygenated haemoglobin absorb light at different wavelengths differently. Deoxygenated or ‘‘blue’’ blood absorbs light maximally in the red band, whereas Oxygenated or ‘‘red’’ blood absorbs light maximally in the infrared band. The ratio of absorption of the two wavelengths of light are then compared with an algorithm in the microprocessor generated by empirically measuring the absorption in healthy volunteers at varying degrees of directly measured arterial oxygen saturation. The displayed value is usually an average based on the previous 3 to 6 seconds of recording.
- At an SPO2 of 94%, additional oxygen is of NO BENEFIT. At this level, the standard dissociation curve is relatively flat, which means that the oxygen content of the blood does not change significantly even with large increases in oxygen.
- Oxygen DOES NOT CURE DIFFICULTY IN BREATHING (DYSPNOEA), just HYPOXIA.
- Oxygen should be delivered to achieve a target saturation of 94–98% for most acutely ill patients or 88–92% for those at risk of hypercapnic respiratory failure e.g. COPD
- Humidification of supplemental oxygen commonly delivered by bubbling oxygen through either cold or warm sterile water before it reaches the patient should NOT be used because there is NO EVIDENCE of a clinically significant benefit but there is a risk of infection.
- Nasal prongs delivers 4% additional oxygen per 1 litre of flow i.e. at 1L/min it delivers 24% (20% is already in the air), at 2L per min it delivers 28%, 3L/min 32%…and so on so at 6L/min it delivers 44%
- A simple face mask should be used at a minimum of 6L/min (normal minute ventilation) to prevent the patient from breathing back their own CO2.
- Application of a self inflating Bag-Valve-Mask on a patient’s face without compressing the bag is called suffocation. Due to the valves system, oxygen is only delivered ON COMPRESSING THE BAG
- Specific targets for oxygen therapy;
- Most patients – 94-98%
- COPD patients – 88-92%
- Heart Attack (ACS) patients – 90%
- Stroke patients – 90%
- Cardiac arrest patients post ROSC – 92-98%
- Nonhypoxic heart attack victims treated with oxygen endure a 25 to 30% more heart damage than patients not given oxygen
- Oxygen supplementation to nonhypoxic patients with mild or moderate strokes may increase mortality.
- High-dose oxygen therapy to produce hyperoxaemia (above normal oxygen saturation) can cause absorption atelectasis
- Oxygen is liberally administered to many critically ill patients, thereby exposing them to supranormal arterial oxygen levels.
- Hyperoxia also results in the formation of reactive oxygen species, which adversely affect the pulmonary, vascular, cnetral nervous, and immune systems.
- Though the optimal PaO2 remains unknown, recent evidence indicates that hyperoxia is associated with increased mortality in post-cardiac arrest, CVA, acute coronary syndrome, and traumatic brain injury patients.
- Take Home Point: Carefully titrate oxygen to the lowest tolerable level to meet the patient’s needs.
Need to calculate your oxygen requirements? Use the calculator below to estimate how long different oxygen sources/cylinders will last or how much/many you will need while using various O2 delivery devices and flow rates.
What you need to know
- It is a longstanding cultural norm to provide supplemental oxygen to sick patients regardless of their blood oxygen saturation
- A recent systematic review and meta-analysis has shown that too much supplemental oxygen increases mortality for medical patients in the hospital
- For patients receiving oxygen therapy, aim for peripheral capillary oxygen saturation (SpO2) of ≤ 96% (strong recommendation)
- For patients with acute myocardial infarction or stroke, do not initiate oxygen therapy in patients with SpO2 ≥ 90% (for ≥ 93% strong recommendation, for 90-92% weak recommendation)
- A target SpO2 range of 90-94% seems reasonable for most patients and 88-92% for patients at risk of hypercapnic respiratory failure; use the minimum amount of oxygen necessary
Humidified oxygen is widely administered in hospitals and EMS vehicles and this is presumed to alleviate nasal and oral discomfort in the non-intubated patient. Humidification of supplemental oxygen is commonly delivered by bubbling oxygen through either cold or warm sterile water before it reaches the patient. However, the effect on patient comfort is negligible. Bubble humidifiers may, however, represent an infection hazard and should not be used.