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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.
The resistive work of breathing causes the deviation of the inspiratory and expiratory lines: The area between the compliance line and the inspiratory line is additional resistive inspiratory work done
Definitions of work and power of breathing. Work is the product of force and displacement, measured in joules, where 1J is the expenditure of one joule through a displacement of one metre. The equation for work at its most basic is: Work = Force × Distance
The main goal of mechanical ventilation is to help restore gas exchange and reduce the work of breathing (WOB) by assisting respiratory muscle activity. Knowing the determinants of WOB is essential for the effective use of mechanical ventilation and also to assess patient readiness for weaning.
Work of breathing (WOB) may be defined as the product of pressure and volume. It may be analyzed by plotting transpulmonary pressure against tidal volume. The WOB per kilogram body weight is similar in infants and adults.
The “work” of breathing is often assessed clinically, but there is a physical basis and objective definition of work. Work is a thermodynamics concept. Conceptually, work of breathing is the pressure change necessary to overcome resistive and elastic work in order to generate a tidal volume ∆V .
The equation above represents the mechanical work performed by the respiratory muscles. The pressure represents the force generated by the muscles, and the volume represents the amount of air moved in each breath.
In a fluid system, the mechanical work (W) is integral of press ure applied (P) and the resulting volume change (V): w=fp·dv (1) Indeed, since press ure is force per unit area (F/A) and volume is area times length (A.I), the above equation is equivalent to w=fF.dl. Mechanical work is performed by a contracting muscle only if there is dis
The work is the amount of pressure required to move a volume and is calculated by the integral of the tidal volume and esophageal pressure (as surrogate of pleural pressure) during inspiration and is expressed in units of Joules. To obtain such calculation, an esophageal balloon manometry is required to construct the Campbell diagram above. 1,2 The
Regarding our methods and data used to calculate airway work using the mechanical model, we respond as follows: work is the product of pressure and volume. Therefore, flow-resistive work on the airway equals ∫P AW dV.