Research and Development Expenses
Research and development (“R&D”) expenses increased $0.1 million, or 9%, to $1.2 million in the three months ended June 30, 2021, compared to $1.1 million in the three months ended June 30, 2020, which was primarily attributable to an increase in clinical studies activity.
R&D expenses decreased $0.3 million, or 11%, to $2.5 million in the six months ended June 30, 2021, compared to $2.8 million in the six months ended June 30, 2020, which was primarily attributable to a $0.2 million decrease in professional services and a $0.1 million decrease in personnel-related compensation expense.
Reimbursement, General and Administrative Expenses
Reimbursement, general and administrative expenses decreased $0.2 million, or 2%, to $14.1 million in the three months ended June 30, 2021, compared to $14.4 million in the three months ended June 30, 2020. This decrease was primarily attributable to a $3.6 million impairment charge related to the write-off of our Airwear wrap-related long-lived assets recorded in the second quarter of 2020, partially offset by a $1.9 million increase in personnel-related compensation expense as a result of increased headcount in our reimbursement operations, payer relations and corporate functions and a combined $1.4 million increase in occupancy costs, depreciation expense and legal fees, in each case in the three months ended June 30, 2021 compared to the three months ended June 30, 2020.
Reimbursement, general and administrative expenses increased $3.2 million, or 13%, to $28.4 million in the six months ended June 30, 2021, compared to $25.2 million in the six months ended June 30, 2020. The increase was primarily attributable to a combined $3.5 million increase in occupancy costs, depreciation expense, legal and professional fees and a $3.3 million increase in personnel-related compensation expense as a result of increased headcount in our reimbursement operations, payer relations and corporate functions, partially offset by a $3.6 million impairment charge related to the write-off of our Airwear wrap-related long-lived assets recorded in the second quarter of 2020.
Other Income (Expense), Net
Other income (expense), net was an expense of $24,000 and income of $36,000 for the three months ended June 30, 2021 and 2020, respectively, and was an expense of $34,000 and income of $0.3 million for the six months ended June 30, 2021 and 2020, respectively. Other income (expense) was primarily impacted by interest income realized on marketable securities and the gain and loss on cost method investments.
Income Taxes
We recorded an income tax benefit of $1.4 million and expense of $5.9 million for the three months ended June 30, 2021 and 2020, respectively. We recorded an income tax benefit of $3.2 million and expense of $3.0 million for the six months ended June 30, 2021 and 2020, respectively. The primary driver of these changes was a tax benefit related to a research and development credit recognized in the second quarter of 2021.
Liquidity and Capital Resources
Cash Flows
At June 30, 2021, our principal sources of liquidity were cash and cash equivalents of $49.0 million and net accounts receivable of $42.6 million, as well as the borrowing capacity available under our Restated Credit Agreement.