ABSTRACT

Questions on pressure can start innocently enough but can lead to almost any aspect of anaesthesia. One college question starts by comparing the pressure generated in 2 and 20 mL syringes and ends up with altitude effects via calibration of pressure transducers. Pressure is the force applied per unit area. Force is a vector quantity that can cause an object with mass to accelerate. Newton’s second law defined force as the mass of an object multiplied by its acceleration. Its Standard International unit is the newton. Dalton’s law states that in a gas mixture the pressure exerted by each individual gas is equal to the pressure that gas would exert if it occupied the container alone. This is the partial pressure. Total pressure is the sum of all the partial pressures in the mixture. Gauge pressure refers to pressure measurements above or below atmospheric pressure.