Individual testing of oxygen saturation of demand oxygen delivery systems (DODS) suitability is recommended in patients with chronic hypoxemia and chronic obstructive pulmonary disease (COPD), according to the results of a prospective, single-blinded randomized cross-over study ( Identifier: NCT02744170) published in Respiratory Medicine.

Supplemental oxygen may be provided by continuous flow; however, DODS, which provide an oxygen bolus during inspiration only have gained increasing use because they extend oxygen cylinder life and battery life. Because there are few data on whether different DODS and continuous flow devices are equivalent, researchers examined 70 patients with hypoxemic COPD (forced expiratory volume in 1 sec [FEV1] 32.4±9.6% predicted, partial pressure of oxygen in arterial blood [PaO2] 56.3±6.5 mm Hg) on long-term oxygen therapy in a 3-week inpatient pulmonary rehabilitation program in Germany. Patients first performed an incremental shuttle walk test and then 3 endurance shuttle walk tests at 85% of their maximum pace on 3 consecutive days in random order.  

Oxygen supplementation via DODS (based on liquid oxygen or as an oxygen concentrator) yielded comparable physiologic effects during standardized walking in people with stable hypoxemia and COPD, including continuous flow. Patients used an average oxygen flow rate of 2.9±1.0 L/min with continuous flow, 2.9±1.0 L/min while using a DODS based on liquid oxygen, and 4.4±1.2 L/min while using a DODS oxygen concentrator. The oxygen saturation at endurance shuttle walk test isotime was not significantly different between continuous flow and DODS oxygen concentrator (90±4% vs 90±5%, respectively; P =.43), but was significantly different between continuous flow and liquid oxygen DODS (90±4% vs 89±5%, respectively; P =.03). In addition, 20% of the patients showed ³4% lower oxygen desaturation while using a DODS device.

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This was the first study to compare the effects of various oxygen delivery systems using a standardized walk test procedure in a large sample of patients with COPD. The researchers concluded that, “based on these results, individual oxygen saturation testing should be performed under various conditions (rest, exercise and sleep) with the device intended to be prescribed in all patients [who] want to use a DODS system.”

Disclosure: This clinical trial was supported by Linde Healthcare (Germany). Please see the original reference for a full list of authors’ disclosures.


Gloeckl R, Jarosch I, Schneeberger T, et al. Comparison of supplemental oxygen delivery by continuous versus demand based flow systems in hypoxemic COPD patients – a randomized, single-blinded cross-over study. Respir Med. 2019;156;26-32.