The logarithmic scale produces a 10-fold change in hydrogen ion concentration per unit change in pH. Modern blood gas machines rapidly measure several variables including pH, pCO2, PO2, oxyhaemoglobin concentration…

Absorbance is a dimensionless number; 0 indicates no absorbance of light, while 1 indicates 90% of light has been absorbed. Absorbance >1 is uncommon, as Beer–Lambert’s law ceases to be…

Venturi systems utilise the Bernoulli principle to create a negative pressure. They are driven by compressed gas, but are limited by weak flow rates and loud noise. Applied science What…

Cardiac impulses begin in the right atrium at the sino-atrial node. The wave of depolarisation spreads through both atria to the atrioventricular node. Here it travels via the bundle of…

At room temperature and one atmosphere pressure, most anaesthetic agents exist in their liquid form. The vaporising chamber is fully saturated with anaesthetic vapour. Wicks help to increase the surface…

The highest energy level is the most unstable state, and electrons quickly decay by releasing energy in the form of heat to a slightly lower energy level called the metastable…

Wavelength is the distance between two points of maximum compression or rarefaction. The frequency of a wave is the number of wavelengths per second expressed as hertz (Hz). High-frequency sounds…

Surface tension is commonly measured as force per unit length or energy per unit area. The curved meniscus formed in column of mercury in the liquid barometer is an example…