Work of breathing When there is increased gas flow resistance, the optimal respiratory rate decreases. This work (generally during the inhalation phase) is stored as potential energy which is recovered during exhalation. A pressure difference is required to overcome the frictional resistance to gas flow due to viscosity, and to provide non-elastic components of movement of the airway tissues to accommodate pulmonary volume change. Total work done against non elastic forces is 35% of total. Work is defined as a force applied over a distance. The SI unit of work is the Joule, equivalent to a force of 1 Newton exerted along a
History of energy biological thermodynamics and thermoeconomics, to name a couple; as well as related terms such as entropy, a measure of the loss of useful energy, or power, an energy flow per unit time, etc. In the past two centuries, the use of the word energy in various "non-scientific" vocations, e.g. social studies, spirituality and psychology has proliferated the popular literature. In 1918 it was proved that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time. That is, energy is conserved because the laws of physics do not