Note 2 - Summary of Significant Accounting Policies (Details Textual) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of Major Distributors	3		3
Number of Major Source Manufacturers	2		2
Accounts Receivable, Allowance for Credit Loss, Ending Balance	$ 24		$ 24				$ 10
Allowance for Doubtful Accounts, Past Due Period Threshold			120 days
Inventory Valuation Reserves, Ending Balance	109		$ 109				104
Operating Lease, Impairment Loss			$ 125
Impairment of Long-Lived Assets Held-for-use	0	$ 0		$ 0
Payment for Product Supply Period			30 days
Additional Paid in Capital, Ending Balance	123,518		$ 123,518				119,764
Warrants and Rights Outstanding	$ 266		$ 266				$ 178
Earnings Per Share, Diluted, Total | $ / shares	$ (0.14)	$ (0.12)	$ (0.38)	$ (0.26)
Earnings Per Share, Basic, Total | $ / shares	$ (0.14)	$ (0.09)	$ (0.38)	$ (0.22)
Accounting Standards Update 2017-01 [Member]
Additional Paid in Capital, Ending Balance					$ 56	$ 356
Warrants and Rights Outstanding					$ (56)
Accounting Standards Update 2017-01 [Member] | Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption						$ (356)
Accounting Standards Update 2018-07 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 2
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life			5 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life			7 years
Computer Equipment and Software [Member]
Property, Plant and Equipment, Useful Life			3 years
Furniture and Fixtures [Member]
Property, Plant and Equipment, Useful Life			7 years
Leasehold Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life			7 years