CLINICAL MINUTE: O2 Saturation & the POC

Who: Thomas Long, RRT-RCP
Position: CAIRE and AirSep Region Manager-LATAM, Mexico, Caribbean
Topic: Questions about portable oxygen concentrators and measuring O2 saturation

HomeCare: You’ve been in the respiratory health care field for 43 years, including testing the world’s first truly portable oxygen concentrator (POC) prototypes. How much has the field changed over the course of your career? Any surprises?
Long: Yes, I never thought I’d see the day that technology advances would produce a POC that could be 10 pounds or less, be worn, and operate on a variety of power sources; AC, DC and rechargeable battery. With those advances, the world opened up for people afflicted with cardio-respiratory diseases and requiring supplemental oxygen to now be able to travel away from home for vacation, to visit friends and family, and just do things that high-pressure oxygen cylinders would not allow. This allowed for a tremendous improvement in quality of life for the person with chronic obstructive pulmonary disease (COPD). High pressure oxygen cylinders and liquid oxygen sources limit the amount of time a person can be away from their home before they have to refill that source of oxygen. They need to manage “contents” and watch time. With a POC, you manage “power” and are able to connect to any AC outlet, DC outlet in a motor vehicle or airplane, or change the rechargeable batteries—providing the opportunity to be away from home with convenience for extended periods of time.  

HomeCare: You are frequently asked about how to best saturate the long-term oxygen therapy patient on a portable oxygen concentrator. Who is asking this question and what is your advice based on their role within their organization? 
Long: All clinicians—physicians, nurses, homecare and any health care workers dealing directly with the patient needing a POC—often ask this question. Most important, it is critical for the homecare provider’s clinical or technical person to understand how to best determine the “setting” of the POC at rest and during exertion/exercise. If the user travels, they may even need to have an overnight oximetry using the POC to best determine the setting required. I typically like to ask what the current O2 prescription is and if it was determined using oximetry. It is also important to ask if they did both an at rest and at exertion (walk test) oximetry reading. I find in many cases, the O2 prescription was determined by using that ‘magic’ number of 2 LPM and that no testing was performed or, if it was, it was typically when they were at rest. In my opinion, optimal oxygen therapy for the COPD patient’s O2 prescription comes with oximetry testing at rest, during ambulation and during sleep.  

HomeCare: Is the six-minute walk test still the standard in determining oxygen saturation and the patient’s aerobic exercise capacity, or are there other metrics clinicians are utilizing, especially during this age of the COVID-19 pandemic?
Long: The six-minute walk test is still utilized at many health care facilities. Typically, a non-standardized walk test is used to determine oxygen needs during ambulation. This can be accomplished by walking the patient in a hallway or on a treadmill at a level setting while monitoring the SPO2 via oximetry the entire time and adjusting the POC setting to achieve a 90%+ SPO2.

HomeCare: Should a clinician try to titrate a patient on a POC with on-demand/pulse flow oxygen delivery features before prescribing continuous flow oxygen for use in daily activities?
Long: In my experience, the patient should initially be tested on continuous-flow oxygen at rest and, if possible, during ambulation to determine the baseline flow rate of O2 needed to maintain an SPO2 above 90%. Following baseline oximetry tests on continuous flow O2, if the patient is prescribed ambulatory O2, additional oximetry testing should always be performed so proper POC settings can be determined.

HomeCare: Most oxygen therapy prescriptions are written at 2 LPM for the new oxygen patient. What is problematic about this common practice, and what is the most important thing to remember when working with a newly-prescribed patient.
Long: Many COPD patients are discharged from a health care facility typically only having had at-rest oximetry test to determine SPO2. The ‘magic’ number of 2 LPM is probably the most prescribed for home O2. The patient should always be tested via oximetry both for determining the best POC setting at rest and during ambulation. Since each POC can have a different effect on a person’s SPO2, if the prescription for O2 from the physician calls for 2 LPM, I recommend initially using a POC’s setting of 2 to evaluate SPO2 both at rest and during ambulation to determine what settings may be needed, keeping in mind those settings typically differ from the continuous-flow prescription. Of course, any deviation from the physician’s prescription using a POC should be discussed with the patient’s physician.