Saturation in Portable Oxygen Concentrators

AG is a 75-year-old woman diagnosed with COPD 2 years earlier. Her room air oxygen saturation is 90% to 91% at rest. Treadmill oxygen titration revealed desaturation below 88%. She was prescribed 3 L via nasal cannula with saturation increasing to 98% at rest and 92% with exercise. Her physician decides to prescribe 3L via nasal cannula. Oxygen equipment was delivered to her home. She wanted portable equipment for daily activity and traveling and chose a light piece (6 lbs) portable oxygen concentrator (POC) that delivers 3L via pulsed flow.

Today, she is complaining that the POC does not feel the same as her home equipment or the oxygen she received when the treadmill titration was performed.

This, unfortunately, is too common a situation that arises in practice. Many POCs deliver only pulsed oxygen with only a few delivering continuous flow, and these tend to be larger and heavier and not preferred by patients.

Although the technology is improving, pulsed-dose oxygen does not deliver the same oxygen concentration as continuous flow. Thus, 3L delivered from wall oxygen is not the same as 3L from POC with pulsed flow.

Patients should have oxygen saturation tested during activity while receiving pulsed-dose oxygen. Moreover, pulsed flow should not be used during sleep. POCs flow is triggered by nasal inhalation, and mouth breathers will not get oxygen flow.

Most POCs also are not capable of delivering an adequate saturation level nocturnally for the patient. Continuous flow should generally be prescribed for sleep.

What matters are not the liters but the saturation, taking into account patients’ preferences.

Dr. Rubin Cohen, FCCP
NetWork Vice-Chair