Work of breathing Work of breathing Work of breathing (WOB) is the energy expended to inhale and exhale a breathing gas. It is usually expressed as work per unit volume, for example, joules/litre, or as a work rate (power), such as joules/min or equivalent units, as it is not particularly useful without a reference to volume or time. It can be calculated in terms of the pulmonary pressure multiplied by the change in pulmonary volume, or in terms of the oxygen consumption attributable to breathing. In a normal resting state the work of breathing constitutes about 5% of the total body oxygen consumption.
Orbital replacement unit (HST) of fasteners). HST servicing mission 3A (SM3A) replaced (or added) 15 ORUs, e.g. it replaced the DF-224 computer with the "Advanced Computer". The electrical system of the International Space Station also has such subsystems that provide power generation, power distribution and energy storage. Orbital replacement unit (HST) An orbital replacement unit or orbital replaceable unit is a modular component of spacecraft that can be replaced upon failure either by robot or by extravehicular activity. The Hubble Space Telescope (HST) was designed with 70 such parts, including scientific instruments and limited-life items such as batteries. On HST some parts were designed