Beginning with our April 8, 2008 Patient Safety Tip of the Week Oxygen as a Medication we lamented the fact that oxygen is used rather cavalierly in many medical settings. Indications for oxygen use have often lacked a solid evidence base and safety issues are largely ignored. We made a plea that oxygen should be treated just like a medication. It should require a prescription with:
In our January 27, 2009 Patient Safety Tip of the Week Oxygen Therapy: Everything You Wanted to Know and More! we highlighted the British Thoracic Society Guideline for Emergency Oxygen Use in Adult Patients (ODriscoll 2015). Now the Thoracic Society of Australia and New Zealand (TSANZ) has developed new guidelines for oxygen use in the acute medical setting (Beasley 2015). These share many features with the BTS guideline but there are some differences. Also, the TSANZ guidelines do not apply to perioperative patients or ICU patients, though many of the core principles would be the same.
One key difference is in the target oxygen saturation level for most patients. The BTS guideline used an oxygen saturation of 94-98% as the target whereas the TSANZ guideline uses 92-96% as the target. This compromise was made to discourage overoxygenation (Walters 2015) but it also allows for identification of both deterioration and improvement in patients on supplemental oxygen. So the oxygen FIO2 or flow rate can be increased if the oxygen saturation falls below the target level but, for example, if a patients oxygen saturation reached 97% the FIO2 or flow rate could be reduced. Walters and King (Walters 2015) note that the emphasis is on heeding changes in the levels of oxygen saturation, not for their own sake, but as a reflection of the underlying condition.
The target for those patients with COPD or others at risk for hypercarbia remains 88-92% in both guidelines. In our January 27, 2009 Patient Safety Tip of the Week Oxygen Therapy: Everything You Wanted to Know and More! it was also recommended that those patients with a history of previous hypercapnic respiratory failure carry an alert card that contains recommendations about the ideal oxygen dose and target saturation range for that individual patient. Pilcher and Beasley (Pilcher 2015) cite a randomized controlled trial in COPD patients (Austin 2010) that showed mortality was over two times higher in COPD patients randomized to higher concentration oxygen, with a number need to harm (death) of 14.
The TSANZ guidelines do recommend initial arterial blood gas measurements to define the true oxygen and carbon dioxide status of the patient. They note that use of only pulse oximetry tells you nothing about the patients CO2 status and note the inaccuracies of venous blood gases for both oxygen and CO2 status.
The indication for supplemental oxygen therapy, with rare exceptions, is hypoxemia. For years we would routinely use supplemental oxygen in patients with acute MI or stroke. But evidence has accumulated that such is not only not helpful but may actually be harmful in patients who are not hypoxemic (see list of columns below on dangers of oxygen therapy). Note that there are patients who are short of breath but who have normal oxygen saturations and supplemental oxygen is not indicated in such cases.
The dose of oxygen is the oxygen concentration or flow rate anticipated to create the desired oxygen saturation for the particular patient. As we have emphasized before, the target oxygen saturation for most patients is 92-96% but for patients at risk for hypercarbia, such as those with COPD, the target range is lower, usually 88-92%. The oxygen concentration/flow rate should be maintained at a level to keep the oxygen saturation within the target range.
The route of oxygen administration in most cases is via nasal cannula, using FIO2s in the 24-35% range and flow rates on 1-4 L/minute. Other routes (eg. face mask, non-rebreather reservoir masks, Venturi masks, hi-flow nasal cannula) may be used under certain circumstances.
Monitoring is by pulse oximetry, plus attention to vital signs and level of arousal. However, whenever the potential for respiratory depression is present (eg. COPD, patients with neuromuscular diseases, patients on opioids, etc.) or the patient has known or possible sleep apnea the patient should also be monitored by end-tidal CO2 measurement (capnography). And since it is really almost impossible to identify all patients at risk for sleep apnea or respiratory depression, isnt it time we make capnography universal?
Patients with sleep apnea and those on opioids or other drugs that may cause respiratory depression merit special consideration. Firstly, they should not be routinely placed on supplemental oxygen. Only if they are hypoxemic at baseline should oxygen be used. The major risk in such patients is hypercarbia and oxygen therapy may in fact mask evolving deterioration. If you are only monitoring oxygen saturation by pulse oximetry and not monitoring end-tidal CO2 the patient may be developing progressive hypercarbia without any appreciable drop in oxygen saturation and then deteriorate precipitously.
Another note of caution regarding pulse oximetry and sleep apnea: oxygenation is normal in sleep apnea patients when they are awake. So a scenario we see over and over again is the nurse responds to the pulse oximetry alarm, the patient wakens, nurse checks the pulse oximeter and it is now working normally and shows a good oxygen saturation. It is assumed that problem leading to the alarm was false, perhaps positional in nature, and nothing further is done. The patient now falls asleep and has his bout of sleep apnea.
Unfortunately, at almost every hospital we visit we find patients receiving supplemental oxygen long after their need for it has ceased. That is very costly and exposes the patient to potential adverse effects of oxygen therapy. Therefore, every hospital should consider ways to flag patients no longer in need of oxygen and mechanisms for stopping oxygen therapy. You should have criteria for cessation of oxygen (eg. when x consecutive oxygen saturation readings are above 96%). Most hospitals are afraid of having time-limited orders or automatic stop orders for oxygen but having a tickler to trigger an alert for review of oxygen orders is pretty easy to do in todays CPOE systems.
Note also that there are many other oxygen safety considerations. A major one is ensuring safe transport of patients on supplemental oxygen. Some of our previous columns have noted that a high percentage of in-hospital transports (eg. to radiology) result in supplemental oxygen running out. In others oxygen may be disconnected during transport, sometimes by a non-clinical person who does not understand the importance. Because of this each facility should have a formal transport handoff tool like the Ticket to Ride program in which all key safety considerations for transport are in checklist form to be addressed before, during and after transport (see the Ticket to Ride columns listed below).
Another issue oxygen cylinders being empty. On our patient safety walk rounds we routinely look at storage of oxygen cylinders. We cant tell you how many times we find used (empty) cylinders stored together with full ones. It is so easy, particularly under urgent situations, for staff to grab an empty cylinder by mistake.
Metallic oxygen cylinders may also become lethal projectiles in the MRI suite (see our February 19, 2008 Patient Safety Tip of the Week MRI Safety and the other columns listed below on MRI safety).
Medical gas mix-ups fortunately have become less common now that facilities use color coding and unique connectors for different gases. Perhaps the one gas mix-up we still see is hooking up a patient to compressed air instead of oxygen.
Oxygen, of course, is one of the three elements of the fire triad. While weve done numerous columns of surgical/OR fires, dont forget that all 3 elements may be present in other situations. Patients smoking while on oxygen is the most common cause of oxygen-related fires elsewhere in the hospital but remember that almost any heat source in an oxygen-rich environment can trigger a fire since fuel is ubiquitous.
Oxygen tubing disconnections are also possible. We previously described a case (see our March 5, 2007 Patient Safety Tip of the Week ) in which an oxygen blender alarm on a ventilator failed to alert staff to disconnection of the oxygen source because a piece of tape had been placed over the blender alarm (probably during maintenance). While most such disconnections should readily trigger an alarm from the pulse oximetry system when the O2 saturation falls, in that case there had also been a problem with a faulty pulse oximeter.
Just as you audit the use of medications in your facility, auditing the use of oxygen in your facility should be a mandatory exercise to improve patient safety. However, you are also likely to make your CFO happy because your audit will likely lead to changes that will reduce unnecessary costs associated with inappropriate oxygen use. You should also audit compliance with orders for oxygen therapy. How many times have you gone into a patient room and seen the nasal prongs hanging down on his/her neck or being worn on his/her forehead like a sweatband or bandana!
Some hospitals have a Medical Gas Committee that oversees all aspects related to oxygen (and other gas) use. Much like your Pharmacy and Therapeutics Committee this should be a multidisciplinary body with expertise from multiple departments (medical staff, nursing, respiratory therapy, central supply, biomedical engineering, etc.).
The new TSANZ guidelines essentially make it more difficult to prescribe oxygen and create more documentation (Mitchell 2015) but both are necessary evils that translate to good medical care. Implementing many of the other recommendations above also requires human, time and financial resources but likely pays off in the long run.
Some of our prior columns on oxygen and potential harmful effects of oxygen:
April 8, 2008 Oxygen as a Medication
January 27, 2009 Oxygen Therapy: Everything You Wanted to Know and More!
October 6, 2009 Oxygen Safety: More Lessons from the UK
July 2010 Cochrane Review: Oxygen in MI
December 6, 2011 Why You Need to Beware of Oxygen Therapy
February 2012 More Evidence of Harm from Oxygen
March 2014 Another Strike Against Hyperoxia
June 17, 2014 SO2S Confirms Routine O2 of No Benefit in Stroke
December 2014 Oxygen Should Be AVOIDed
Other Patient Safety Tips of the Week pertaining to opioid-induced respiratory depression:
Some of our prior columns on the Ticket to Ride concept:
Some of our prior columns on patient safety issues related to MRI:
ODriscoll BR, Howard LS, Davison AG and the British Thoracic Society. Emergency Oxygen Guideline Group. BTS Guideline Emergency Oxygen Use in Adult Patients. Thorax 2008; 63 (suppl. VI): 1-68
Beasley R, Chien J, Douglas J, et al. TSANZ Oxygen guidelines for acute oxygen use in adults; swimming between the flags. Respirology. In press 2015
Walters E, King G. Appropriate use of oxygen in acute medicine. Med J Aust 2015; 203(3): 125
Mitchell C. Treat oxygen like a drug. MJA Insight 2015; 27 July 2015
Pilcher J, Beasley R. Acute use of oxygen therapy. Australian Prescriber 2015; 38(3): June 2015
Austin MA, Wills KE, Blizzard L, et al. Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: randomised controlled trial. BMJ 2010; 341: c5462
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