Evaluation of Over-the-Counter Portable Oxygen Concentrators Utilizing a Metabolic Simulator

Supplemental oxygen is designed to raise alveolar P_O to facilitate diffusion into arterial blood. Oxygen is generally delivered by nasal cannula either by continuous or pulsatile flow. Battery-powered portable oxygen concentrators (POCs) facilitate ambulation in patients experiencing exertional hypoxemia. In the United States, the Food and Drug Administration (FDA) clears these devices to be sold by physician prescription. Recently, however, lower-cost devices described as POCs have been advertised by online retailers. These devices lack FDA clearance and are obtained over the counter (OTC) without prescription. This study determined whether a selected group of OTC POCs have oxygen delivery characteristics suitable for use by hypoxemic patients.

A metabolic simulator, capable of simulating a range of metabolic rates and minute ventilations, determined effects of oxygen supplementation delivered by a variety of devices on alveolar P_O . Devices tested included 3 OTC POCs, an FDA-cleared POC, and continuous-flow oxygen from a compressed oxygen cylinder. End-tidal P_ETO , a surrogate of alveolar P_O , was determined at each of each device's flow settings at 3 metabolic rates.

Continuous-flow tank oxygen yielded a linear P_ETO increase as flow increased, with progressively lower slope of increase for higher metabolic rate. The prescription POC device yielded similar P_ETO elevations, though with somewhat smaller elevations in pulse-dose operation. One OTC POC was only technically portable (no on-board battery); it provided only modest P_ETO elevation that failed to increase as flow setting was incremented. A second OTC POC produced only minimal P_ETO elevation. A third OTC POC, a pulsed-dose device, produced meaningful P_ETO increases, though not as great as the prescription device.

Only one of 3 OTC POCs tested was potentially of use by patients requiring ambulatory oxygen. Physicians and respiratory therapists should inform patients requiring portable oxygen that OTC devices may not meet their oxygenation requirements.