attributable to a $0.7 million increase in meetings, seminars and tradeshow related expenses and a $0.3 million increase in travel and entertainment expenses, partially offset by a $0.2 million decrease in educational grants expense, a $0.2 million decrease in expenses relating to demo units and a $0.2 million decrease in personnel-related compensation expenses.
Sales and marketing expenses increased $1.5 million, or 3%, to $56.0 million in the six months ended June 30, 2024, compared to $54.5 million in the six months ended June 30, 2023. The increase was primarily attributable to a $0.7 million increase in travel and entertainment expenses, a $0.6 million increase in meetings, seminars and tradeshow related expenses and a $0.2 million increase in personnel-related compensation expenses.
Research and Development Expenses
Research and development (“R&D”) expenses increased $0.4 million, or 22%, to $2.2 million in the three months ended June 30, 2024, compared to $1.8 million in the three months ended June 30, 2023. The increase was primarily attributable to a $0.3 million increase in professional fees and a $0.1 million increase in clinical study related expenses.
R&D expenses increased $0.3 million, or 8%, to $4.4 million in the six months ended June 30, 2024, compared to $4.1 million in the six months ended June 30, 2023. The increase was primarily attributable to a $0.1 million increase in professional fees, a $0.1 million increase in clinical study related expenses and a $0.1 million increase in personnel-related compensation expenses.
Reimbursement, General and Administrative Expenses
Reimbursement, general and administrative expenses increased $1.8 million, or 12%, to $16.8 million in the three months ended June 30, 2024, compared to $15.0 million in the three months ended June 30, 2023. This increase was primarily attributable to a $0.8 million increase in occupancy costs, depreciation expense and professional fees, a $0.5 million increase in personnel-related compensation expenses and a $0.5 million increase in IT related expenses.
Reimbursement, general and administrative expenses increased $2.6 million, or 9%, to $33.0 million in the six months ended June 30, 2024, compared to $30.4 million in the six months ended June 30, 2023. This increase was primarily attributable to a $1.0 million increase in personnel-related compensation expenses, a $1.0 million increase in IT related expenses, and a $0.6 million increase in occupancy costs, depreciation expense and professional fees.
Intangible Asset Amortization and Earn-out Expense
Intangible asset amortization and earn-out expense decreased $0.6 million to $0.6 million in the three months ended June 30, 2024, compared to $1.2 million in the three months ended June 30, 2023. The decrease was related to there being no earn-out expense in the three months ended June 30, 2024, as final payment under the AffloVest Acquisition earn-out Arrangement was made on November 28, 2023, compared to an increase in the fair value of the earn-out expense of $0.6 million for the three months ended June 30, 2023.
Intangible asset amortization and earn-out expense decreased $1.3 million to $1.3 million in the six months ended June 30, 2024, compared to $2.5 million in the six months ended June 30, 2023. The decrease was related to there being no earn-out expense in the six months ended June 30, 2024, as final payment under the AffloVest Acquisition earn-out arrangement was made on November 28, 2023, compared to an increase in the fair value of the earn-out expense of $1.2 million for the six months ended June 30, 2023.