This is a great trivia question that nobody around you will know!  We have traveled to high altitudes (think Utah--our CEO’s home state!) from sea level without a problem; however, we have not rigorously tested the pump at altitude. It is always best to check your fluid level prior to each session and if you notice a drop in efficiency please follow the troubleshooting steps listed in the user manual. We have read that air-based pumps (all breast pumps except for yours truly) can lose some suction strength in high altitudes (again Utah and hello Colorado!) When in doubt, we’re here for you! Just email us at support@nayahealth.com