Portable oxygen concentrators can be used as part of a comprehensive treatment plan for sleep apnea, particularly in cases where continuous positive airway pressure (CPAP) therapy is recommended. While portable oxygen concentrators provide a continuous supply of oxygen, they are not standalone sleep apnea treatment devices. Sleep apnea machines online can be bought via reputable websites like Tentabs, but make sure to consult with a healthcare provider to determine the most appropriate treatment options for sleep apnea management.