Facial injuries are common and can involve both soft tissue injury and bony injury. These often occur because of motor vehicle collisions, secondary to direct impact against the windshield, steering wheel, or dashboard, as well as from broken glass fragments, causing lacerations and eye injuries. Many facial injuries also occur because of physical assault or because of falls to the head and face, especially in the elderly, who are less able to protect their face while falling.

Children are not simply ‘small adults’. The anatomical and physiological differences between children and adults have a significant impact on their anaesthetic management.

The cardiac output (CO) is the volume of blood ejected by the left ventricle (LV) or right ventricle (RV) per minute.

Triiodothyronine (T3), the strongly biologically active thyroid hormone. T3 comprises only 10% of the hormones released by the thyroid gland. In the circulation, T3 is very highly protein bound (99.7%), mainly to albumin, and has a short half-life (24 h). Only the unbound fraction of T3 is able to diffuse into the tissues to exert its effects.

The Valsalva manoeuvre is performed by forced expiration against a closed glottis. It is attributed to Antonio Valsalva (1666–1723), who described it as a test of Eustachian tube patency and as a method of expelling pus from the middle ear.

The electrocardiogram (ECG) represents a summation of electrical activity in the heart, derived from extracellular electrode recordings obtained from the body surface. Although a detailed description of ECG analysis for detecting cardiac pathology is beyond the scope of this book, this chapter provides a simplified outline of the electrical basis of the normal ECG.

In 2003, the completion of the Human Genome Project resulted in the sequencing of every human gene and subsequently heralded the ‘age of the genome’. Whilst the knowledge of genetics has revolutionised medicine, the phenotypic significance of most genes remains poorly understood. This will be a major focus of physiological research in the future.

The liver is responsible for a wide range of strategic biochemical functions, synthesising and eliminating a huge number of molecules for a variety of purposes. A healthy liver has some important features.

The pulmonary circulation differs significantly in characteristics from the systemic circulation. The pulmonary circulation is a low-pressure, low-resistance, high-flow circulation: a blood flow of 5 L/min (i.e. 100% of cardiac output, CO) is achieved with a driving pressure (i.e. mean pulmonary artery pressure, MPAP) of only 15 mmHg.

The lower airways can be divided into the larynx and tracheobronchial tree, which is subdivided into the conducting and respiratory zones.

The primary function of the heart is ejection of blood into the vascular system. Individual cardiomyocytes are specialised in the generation of spontaneous activity (automaticity), transmission of the resulting excitable activity and contraction in response to such excitation.

The Frank–Starling law (also known as Starling’s law of the heart) states that the strength of ventricular contraction is dependent on the length of the resting fibres. In other words, when all other factors are kept constant, an increase in left ventricular preload causes stroke volume (SV) to increase, without the need for extrinsic neural or humoral regulatory mechanisms. As left ventricular preload (i.e. left ventricular end-diastolic volume, LVEDV) is difficult to measure, left ventricular end-diastolic pressure (LVEDP) is often used as its surrogate marker. The relationship between SV and LVEDP is nonlinear (Figure 30.1).

A volume of 500–1000 mL of saliva is secreted by the parotid, submandibular and sublingual glands per day in response to the thought, smell, taste and presence of food in the mouth or stomach. Saliva is 98% water, with the remaining 2% made up of.

Pulmonary function tests (PFTs) are used to quantify an individual patient’s respiratory physiology. A battery of tests and manoeuvres are performed to measure the performance of the different lung components.