Centimetre of water
A centimetre of water is a less commonly used unit of pressure derived from pressure head calculations using metrology.
It may be defined as the pressure exerted by a column of water of 1 cm in height at 4 °C at the standard acceleration of gravity, so that = × × 1 cm = ≈, but conventionally a nominal maximum water density of is used, giving.
It is frequently used to measure the central venous pressure, the intracranial pressure while sampling cerebrospinal fluid, as well as determining pressures during mechanical ventilation or in water supply networks. It is also a common unit of pressure in the speech sciences. This unit is commonly used to specify the pressure to which a CPAP machine is set after a polysomnogram.
