It is a 2007 HCPCS code for "Oxygen concentrator, single delivery port, capable of delivering 85 percent Oxygen"
The allowance for E1390 can be looked up but your location drives the allowance with all insurances. Your zip code is necessary to answer your question.
E1390 and K0738 can be billed together since one is a stationary unit, and one is a patient owned portable unit. However, suppliers shall bill HCPCS code K0738 only in situations where the beneficiary owns stationary oxygen equipment but rents gaseous oxygen transfilling equipment.