Always check your withholding with this tool if there are personal or financial changes in your life that might change your tax liability, for example new employment or a promotion changing income amount, or new family members altering the number of dependents you claim.
believe the answer you're looking for has to do with the pressure-altitude-voltage derating related to corona discharge, which increases (gets worse) with higher altitude and peaks at around 80-100,000' Typically this is considered to occur at votlages above 300 V peak, but be sure you are accounting for all transients and internal voltages.
Effects of inhaled nitric oxide in patients with acute respiratory distress syndrome: results of a randomized phase II trial. Inhaled Nitric Oxide in ARDS Study Group. Crit Care Med. 1998 Jan. 26(1):15-23.