Note 10 - Stockholders' Equity - Common Shares Reserved for Future Issuance (Details) - $ / shares shares in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Common stock, capital shares reserved for future issuance (in shares)		16,629	7,228
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)
Expiration date
Common stock, capital shares reserved for future issuance (in shares)		16,629	7,228
Service Agreement - 2021 warrants (in dollars per share)
Expiration date
Investors - March 2021 Financing [Member]
Common stock, capital shares reserved for future issuance (in shares)		9,231	0
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 3.60
Expiration date		03/25/26
Common stock, capital shares reserved for future issuance (in shares)		9,231	0
Service Agreement - 2021 warrants (in dollars per share)		$ 3.60
Expiration date		03/25/26
March 2021 Warrants [Member]
Common stock, capital shares reserved for future issuance (in shares)		170	0
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 8.25
Expiration date		02/09/24
Common stock, capital shares reserved for future issuance (in shares)		170	0
Service Agreement - 2021 warrants (in dollars per share)		$ 8.25
Expiration date		02/09/24
Investors - May 2020 Financing [Member]
Common stock, capital shares reserved for future issuance (in shares)		3,155	3,155
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 7.98
Expiration date		05/22/25
Common stock, capital shares reserved for future issuance (in shares)		3,155	3,155
Service Agreement - 2021 warrants (in dollars per share)		$ 7.98
Expiration date		05/22/25
Investors - December 2019 Financing [Member]
Common stock, capital shares reserved for future issuance (in shares)		1,458	1,458
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 12.09
Expiration date		12/06/24
Common stock, capital shares reserved for future issuance (in shares)		1,458	1,458
Service Agreement - 2021 warrants (in dollars per share)		$ 12.09
Expiration date		12/06/24
Investors - Aerosurf [Member]
Common stock, capital shares reserved for future issuance (in shares)		988	988
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 0
Expiration date		02/14/24
Common stock, capital shares reserved for future issuance (in shares)		988	988
Service Agreement - 2021 warrants (in dollars per share)		$ 0
Expiration date		02/14/24
Investors - December 2018 Financing - Long-term [Member]
Common stock, capital shares reserved for future issuance (in shares)		1,296	1,296
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 12.15
Expiration date		12/04/23
Common stock, capital shares reserved for future issuance (in shares)		1,296	1,296
Service Agreement - 2021 warrants (in dollars per share)		$ 12.15
Expiration date		12/04/23
Investors - December 2018 Financing - Short-term [Member]
Common stock, capital shares reserved for future issuance (in shares)		0	0
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 11.04
Expiration date		12/24/20
Common stock, capital shares reserved for future issuance (in shares)		0	0
Service Agreement - 2021 warrants (in dollars per share)		$ 11.04
Expiration date		12/24/20
Battelle - 2018 Payables Restructuring Agreement [Member]
Common stock, capital shares reserved for future issuance (in shares)	[1]	25	25
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)	[1]	$ 19.50
Expiration date	[1]	12/07/23
Common stock, capital shares reserved for future issuance (in shares)	[1]	25	25
Service Agreement - 2021 warrants (in dollars per share)	[1]	$ 19.50
Expiration date	[1]	12/07/23
Panacea Venture Management Company Ltd. [Member]
Common stock, capital shares reserved for future issuance (in shares)		63	63
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 12.00
Expiration date		07/02/23
Common stock, capital shares reserved for future issuance (in shares)		63	63
Service Agreement - 2021 warrants (in dollars per share)		$ 12.00
Expiration date		07/02/23
LPH II Investments Limited [Member]
Common stock, capital shares reserved for future issuance (in shares)		45	45
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 16.56
Expiration date		04/04/25
Common stock, capital shares reserved for future issuance (in shares)		45	45
Service Agreement - 2021 warrants (in dollars per share)		$ 16.56
Expiration date		04/04/25
Investors - February 2017 Financing [Member]
Common stock, capital shares reserved for future issuance (in shares)		117	117
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 82.20
Expiration date		02/15/24
Common stock, capital shares reserved for future issuance (in shares)		117	117
Service Agreement - 2021 warrants (in dollars per share)		$ 82.20
Expiration date		02/15/24
Investors - July 2015 Financing [Member]
Common stock, capital shares reserved for future issuance (in shares)		80	80
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 588.00
Expiration date		07/22/22
Common stock, capital shares reserved for future issuance (in shares)		80	80
Service Agreement - 2021 warrants (in dollars per share)		$ 588.00
Expiration date		07/22/22
Battelle 2014 Collaboration Agreement [Member]
Common stock, capital shares reserved for future issuance (in shares)		1	1
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 4,200.00
Expiration date		10/10/24
Common stock, capital shares reserved for future issuance (in shares)		1	1
Service Agreement - 2021 warrants (in dollars per share)		$ 4,200.00
Expiration date		10/10/24

[1] See, Note 14 - Collaboration, Licensing and Research Funding Agreements, for further details on the Battelle collaboration agreement.