Note 2 - Summary of Significant Accounting Policies (Details Textual) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares	Jan. 01, 2019 USD ($)
Number of Major Distributors				3
Accounts Receivable, Allowance for Credit Loss, Ending Balance				$ 51	$ 10
Allowance for Doubtful Accounts, Past Due Period Threshold				120 days
Inventory Valuation Reserves, Ending Balance				$ 247	104
Operating Lease, Impairment Loss		$ 125		$ 125
Payment for Product Supply Period				30 days
Additional Paid in Capital, Ending Balance				$ 125,718	$ 119,764
Earnings Per Share, Basic, Total | $ / shares				$ (0.48)	$ (0.39)	$ (0.48)
Earnings Per Share, Diluted, Total | $ / shares				$ (0.48)	$ (0.46)	$ (0.48)
Accounting Standards Update 2017-11 [Member]
Additional Paid in Capital, Ending Balance		56		$ 56			$ 356
Warrants and Rights Outstanding		$ (56)		$ (56)			(56)
Accounting Standards Update 2017-11 [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
Software and Software Development Costs [Member]
Impairment of Long-Lived Assets Held-for-use	$ 32