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 Disabled
Alarms) 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!
April 2009 Nursing
Companion to the BTS Oxygen Therapy Guidelines
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:
References:
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
https://www.mja.com.au/journal/2015/203/3/appropriate-use-oxygen-acute-medicine
Mitchell C. Treat oxygen like a drug. MJA Insight 2015; 27
July 2015
https://www.mja.com.au/insight/2015/28/treat-oxygen-like-drug
Pilcher J, Beasley R. Acute use of oxygen therapy.
Australian Prescriber 2015; 38(3): June 2015
http://www.australianprescriber.com/magazine/38/3/98/100
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
http://www.bmj.com/content/341/bmj.c5462
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