9. Commitments and contingencies Non-cancelable contractual obligations The Company enters into non-cancelable contractual obligations for software licenses and maintenance agreements. As of June 30, 2019, the minimum aggregate payments due under specified non-cancelable contractual obligations are summarized as follows: Non-cancelable contractual obligations Remaining 6 months of 2019 $ 288 2020 578 2021 457 2022  2023  Thereafter  $ 1,323 Purchase obligations The Company had approximately $61,700 of outstanding purchase orders with its outside vendors and suppliers as of June 30, 2019. Warranty obligations The following table identifies the changes in the Companys aggregate product warranty liabilities for the six and twelve-month periods ended June 30, 2019 and December 31, 2018, respectively: June 30, December 31, 2019 2018 Product warranty liability at beginning of period $ 9,530 $ 6,171 Accruals for warranties issued 3,948 7,693 Adjustments related to preexisting warranties (including changes in estimates) (275 ) 90 Settlements made (in cash or in kind) (2,878 ) (4,424 ) Product warranty liability at end of period $ 10,325 $ 9,530 Legislation and HIPAA The healthcare industry is subject to numerous laws and regulations of federal, state and local governments. These laws and regulations include, but are not necessarily limited to, matters such as licensure, accreditation, government healthcare program participation requirements, reimbursement for patient services, and Medicare and Medicaid fraud and abuse. Government activity has continued with respect to investigations and allegations concerning possible violations of fraud and abuse statutes and regulations by healthcare providers. Violations of these laws and regulations could result in exclusion from government healthcare programs together with the imposition of significant fines and penalties, as well as significant repayments for patient services previously billed. The Company believes that it is in compliance in all material respects with applicable fraud and abuse regulations and other applicable government laws and regulations. Compliance with such laws and regulations can be subject to future government review and interpretation as well as regulatory actions unknown or unasserted at this time. The Health Insurance Portability and Accountability Act of 1996 (HIPAA) ensures health insurance portability, reduces healthcare fraud and abuse, guarantees security and privacy of health information, and enforces standards for health information. The Health Information Technology for Economic and Clinical Health Act (HITECH Act) imposes notification requirements of certain security breaches relating to protected health information. The Company believes that it complies in all material respects with the provisions of those regulations that are applicable to the Companys business. Legal proceedings Securities class action and derivative lawsuits On March 6, 2019, plaintiff William Fabbri filed a lawsuit against Inogen, Scott Wilkinson, and Alison Bauerlein, in the United States District Court for the Central District of California on behalf of a purported class of purchasers of the Companys securities. On March 21, 2019, plaintiff Steven Friedland filed a substantially similar lawsuit against the same defendants in the same court. On May 20, 2019, the court issued an order consolidating the two lawsuits under the name In re Inogen, Inc. Sec. Litig., No. 2:19-cv-01643-FMO-AGR, appointing Dr. John Vasil and Paragon Fund Management as lead plaintiffs, and appointing Robbins Geller Rudman &amp; Dowd LLP and Glancy Prongay &amp; Murray LLP as lead plaintiffs counsel. On July 10, 2019, the lead plaintiffs filed a consolidated amended complaint on behalf of a purported class of purchasers of the Companys common stock between November 8, 2017 and May 7, 2019. The complaint generally alleges that the defendants failed to disclose that: (i) Inogen had overstated the true size of the total addressable market for its portable oxygen concentrators and had misstated the basis for its calculation of the total addressable market; (ii) Inogen had falsely attributed its sales growth to the strong sales acumen of its salesforce, rather than to deceptive sales practices; (iii) the growth in Inogens domestic business-to-business sales to home medical equipment providers was inflated, unsustainable and was eroding direct-to-consumer sales; and (iv) Inogens decision to focus on sales over rentals of portable oxygen concentrators harmed its ability to serve the Medicare market. The complaint seeks compensatory damages in an unspecified amount, costs and expenses, including attorneys fees and expert fees, prejudgment and post-judgment interest and such other relief as the court deems proper. The Company intends to vigorously defend itself against these allegations. On June 26, 2019, plaintiff Twana Brown filed a shareholder derivative lawsuit against Inogen, Scott Wilkinson, Alison Bauerlein, Benjamin Anderson-Ray, Scott Beardsley, R. Scott Greer, Raymond Huggenberger, Heath Lukatch, Loren McFarland, and Heather Rider for breaches of their fiduciary duties as directors and/or officers of Inogen, unjust enrichment, waste of corporate assets and violations of section 14(a) of the Securities Exchange Act of 1934, as amended. The complaint generally alleges similar claims to the securities class action. The complaint seeks compensatory damages in an unspecified amount, changes to the Companys corporate governance and internal procedures, costs and expenses, including attorneys fees and expert fees, and such other relief as the court deems proper. On August 5, 2019, the court issued an order staying the derivative action pending the resolution of the motion to dismiss stage in In re Inogen, Inc. Sec. Litig . The Company intends to vigorously defend itself against these allegations. Other litigation In addition to the lawsuits discussed above, the Company is party to various legal proceedings arising in the normal course of business. The Company carries insurance, subject to specified deductibles under the policies, to protect against losses from certain types of legal claims. At this time, the Company does not anticipate that any of these other proceedings arising in the normal course of business will have a material adverse effect on the Companys business. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources, and other factors.