director may be eligible for additional payments for the achievement of sales milestones specified in our merger agreement with Cianna Medical.
Fair Value of Other Financial Instruments
The carrying amount of cash and cash equivalents, receivables, and trade payables approximate fair value because of the immediate, short-term maturity of these financial instruments. Our long-term debt re-prices frequently due to variable rates and entails no significant changes in credit risk and, as a result, we believe the fair value of long-term debt approximates carrying value. The fair value of assets and liabilities whose carrying value approximates fair value is determined using Level 2 inputs, with the exception of cash and cash equivalents, which use Level 1 inputs.
Impairment and Other Charges
We recognize or disclose the fair value of certain assets, such as non-financial assets, primarily property and equipment, right-of-use operating lease assets, intangible assets and goodwill in connection with impairment evaluations. All our nonrecurring valuations use significant unobservable inputs and therefore fall under Level 3 of the fair value hierarchy. During the three-month periods ended June 30, 2020 and 2019, we recorded impairment charges of approximately $2.4 million and $548,000, respectively, related to certain acquired intangible assets (see Note 6).
During the three and six-month periods ended June 30, 2020, we had losses of approximately $88,000 and $529,000, compared to losses of approximately $46,000 and $257,000, respectively, for the three and six-month periods ended June 30, 2019, related to the measurement of other non-financial assets, property and equipment and patents, at fair value on a nonrecurring basis subsequent to their initial recognition.
During the three-month period ended June 30, 2020, we identified changes in events and circumstances relating to a certain right-of-use (“ROU”) operating lease asset. We compared the anticipated undiscounted cash flows generated by a sublease to the carrying value of the ROU operating lease and related long-lived assets and determined that the carrying value was not recoverable. Consequently, we recorded an impairment loss of approximately $1.5 million, which is equal to the excess of the carrying value of the assets over their estimated fair value. The impairment loss was driven by site consolidation decisions and changes in our projected cash flows for the ROU operating lease asset and related long-lived assets, due to changes in the real estate market as a result of the COVID-19 pandemic. These changes include an increase in the anticipated time to identify a lessee, an increase in anticipated lease concessions, and a decrease in the expected lease rates for the property.
During the six-month period ended June 30, 2020 we recorded a charge of $3.5 million due to our write-off of our purchase option to acquire Bluegrass Vascular Technologies, Inc. (“Bluegrass Vascular”) due to our decision not to exercise our option to purchase the company.
Equity Investments
Our equity investments in privately held companies, including options to acquire these companies, were $14.5 million and $17.1 million as of June 30, 2020 and December 31, 2019, respectively. We analyze our investments in privately held companies to determine if they should be accounted for using the equity method based on our ability to exercise significant influence over operating and financial policies of the investment. Investments not accounted for under the equity method of accounting are accounted for at cost minus impairment, if applicable, plus or minus changes in valuation resulting from observable transactions for identical or similar investments.
Notes Receivable
Our outstanding long-term notes receivable, including accrued interest, were approximately $2.8 million and $2.7 million as of June 30, 2020 and December 31, 2019, respectively. As of June 30, 2020, we had an allowance for current expected credit losses of $757,000 associated with these notes receivable and our contractual obligation to extend credit to Selio. We assess the allowance for current expected credit losses on an individual security basis, due to the limited number of securities, using a probability of default model, which is based on relevant information about past events, including