IELTS Academic Reading Practice Test 349

Every beat of the heart begins with a small electrical signal. A wave of activity spreads through the muscle and makes it contract, and this wave can be detected at the surface of the skin as a change in voltage of about one millivolt. The difficulty for nineteenth-century scientists was that the signal is both tiny and brief: each part of it lasts only a fraction of a second. Recording it faithfully required an instrument far more sensitive, and far faster, than any then available.

For most of the nineteenth century the heart's electricity could only be observed indirectly: in 1856 two German scientists showed that a frog's nerve laid against a beating heart made the attached muscle twitch in time with the beat. The first instrument capable of measuring the current itself was the capillary electrometer, devised by the French physicist Gabriel Lippmann in 1872. It consisted of a narrow glass tube containing mercury and dilute acid; when a voltage was applied, the boundary between them moved, and the movement was watched through a microscope. In 1887 the British physiologist Augustus Waller used the instrument to show that the electrical activity of a human heart could be recorded from electrodes attached to the hands and feet. His tracings, however, were crude: mercury takes time to move, so the electrometer could not keep up with a signal that changed in milliseconds, and the record was distorted.

Willem Einthoven was born in 1860 in Semarang, on the island of Java, then part of the Dutch East Indies. His father, a medical officer, died when Willem was a child, and the family returned to the Netherlands. He studied medicine at the University of Utrecht, completing his doctorate in 1885, and a year later, at the age of twenty-five, he was appointed professor of physiology at Leiden, where he began to work on the problem that had defeated Waller.

His solution, described in 1901, was the string galvanometer. Its central element was an extremely thin filament of quartz, a few thousandths of a millimetre in diameter, suspended between the poles of a powerful electromagnet. Quartz could be drawn into a finer thread than any metal wire, yet the thread remained strong enough to stay taut. When a current passed along the filament, the magnetic field pushed it sideways, and the size of the deflection was proportional to the current. A beam of light cast the filament's shadow onto a moving photographic plate, so that the movement was recorded permanently. Because the filament was light and tightly stretched, it could respond to changes too rapid for any moving liquid.

The magnet posed problems of its own. It weighed more than two hundred kilograms, generated so much heat that it had to be cooled by a steady flow of water, and occupied a large table in Einthoven's laboratory. Yet the quality of the traces it produced was unlike anything seen before: for the first time the separate phases of a single heartbeat could be distinguished from one another.

In 1903 Einthoven published a series of tracings taken from human patients, and this paper is usually regarded as the beginning of clinical electrocardiography. The record showed a flat line interrupted by a sequence of small waves, which he labelled with five letters, P, Q, R, S and T, a scheme he had first applied in 1895 to corrected curves from the older electrometer. The tall spike of R, he argued, marked the moment when the ventricles, the heart's main pumping chambers, were activated. The letters are still used today; the reason he began at P rather than A has never been established with certainty.

The instrument proved its worth in diagnosis. By measuring the interval between the waves, physicians could detect disturbances of rhythm that the pulse alone could not reveal. The tracing also showed, for the first time, the order in which the chambers of the heart contract.

The apparatus was too heavy to move to a ward. In 1906 Einthoven therefore installed a permanent telephone line between the Leiden University Hospital and his laboratory, more than a kilometre away, so that the signals from a patient's limbs could be recorded in his own building.

Equally influential was his standardisation of electrode positions. Einthoven settled on the right arm, the left arm and the left leg, recorded the voltage between each pair of these points in turn, and called the three recordings leads. He also noticed that the second lead always equalled the sum of the first and the third, a relationship still taught to medical students as Einthoven's law.

For some years the machine remained rare. It was expensive to build, delicate to adjust and beyond the budget of most hospitals, and the copies made by commercial instrument companies in Britain and Germany were bought mainly by teaching centres. Its limitations were equally real: the filament broke easily, patients lay with their limbs in jars of salt solution to improve the contact, and the tracing appeared on photographic paper that had to be developed before anyone could read it.

Einthoven received the Nobel Prize in Physiology or Medicine in 1924. He died in Leiden three years later, aged sixty-seven. The string galvanometer was eventually displaced by electronic amplifiers and oscilloscopes, but the five letters, the three limb leads and the principle of recording the heart's electricity from the skin survive in every cardiology department.

Blood pressure is the force that blood exerts on the walls of the arteries. It is not constant: it rises each time the heart contracts and falls as the heart relaxes between beats. The higher figure in a reading, the systolic pressure, corresponds to the moment of contraction; the lower, the diastolic pressure, to the resting phase. Both are expressed in millimetres of mercury, a unit inherited from the days when pressure was measured by the height of a column of that metal. A reading of about 120 over 80 is often quoted as typical of a healthy young adult.

To measure the pressure inside an artery, the clinician must briefly stop the flow of blood through it. This is the job of the cuff, wrapped around the upper arm and inflated until the pressure it applies exceeds the systolic pressure. At that point the artery beneath is squeezed shut and nothing passes. As air is released and the cuff pressure falls, the artery reopens at the instant in each beat when the blood pressure rises above the pressure in the cuff. Blood then forces its way through the narrowed vessel, and the turbulence it creates produces a series of faint tapping sounds. These were described in 1905 by the Russian physician Nikolai Korotkoff, and they remain the basis of the traditional method.

The sounds are heard through a stethoscope placed over the artery below the cuff. The pressure at which they first appear is recorded as the systolic figure, and the pressure at which they vanish, once the vessel is fully open, as the diastolic figure. The instrument that made such measurements practical was devised in 1896 by Scipione Riva-Rocci, an Italian physician, who connected an inflatable cuff to a vertical glass tube of mercury. Because he detected the return of the pulse by touch, his method could reveal only the systolic pressure.

Mercury is used because it is extremely dense. Being more than thirteen times denser than water, it forms a column only about 76 centimetres tall when balancing the whole weight of the atmosphere, and the pressures found in human arteries correspond to a far shorter column that fits easily into a tube of modest length. Unlike a spring, a column of liquid cannot gradually lose its calibration, which is why mercury instruments became the reference against which all others were judged.

A traditional instrument is simple. The fabric sleeve that the patient sees contains an inflatable rubber bladder, and a rubber tube leads from it to the gauge. A hand-held bulb, fitted with a small screw valve, allows the operator to pump air in and to release it in a controlled way. In the mercury version the gauge is a graduated glass column; in the aneroid version, which is more portable, the column gives way to a sealed capsule that moves a needle across a circular dial. Both types work on the same principle: the pressure in the cuff is balanced against a known force, and the result is read from a scale.

Even a well-made instrument can mislead if the measurement is taken carelessly. A cuff that is too small for the arm will overestimate the pressure, because the same force is applied over a smaller area; cuffs are therefore made in several sizes, and the right one must be chosen for each patient. Talking during the measurement, an unsupported arm, crossed legs, a full bladder or a recent cup of coffee can each raise the figure by a few units. Some people also show what is known as the white-coat effect, in which pressure measured in a clinic is consistently higher than pressure recorded elsewhere.

Most measurements are now made by machines that use a different principle. An oscillometric device needs no stethoscope; instead, an electronic pressure sensor looks for small pulsations in the cuff as it deflates. These oscillations are tiny when the cuff pressure is above systolic, grow to a maximum and then fade. The pressure at which the oscillations are largest is taken as the mean arterial pressure, and the systolic and diastolic values are calculated from the pattern of the oscillations by an algorithm written by the manufacturer. No stethoscope or trained ear is needed, which is why such devices can be used at home.

Automation has brought new uncertainties. Because the algorithms are commercial secrets, independent researchers can test a device only by comparing its results with those of a carefully trained observer, and a model that performs well in one group of patients may fail in another. Readings from oscillometric devices are known to be unreliable in people with atrial fibrillation, whose heartbeats vary in strength, and separate validation is needed in pregnancy and in children. Several countries now publish lists of devices that have passed such tests.

For many patients the most useful information comes from measurements made outside the clinic. A device worn for twenty-four hours takes readings at intervals during ordinary activity and sleep, and the average it produces predicts the risk of stroke and heart disease better than a single clinic figure. Home monitoring can also reveal masked hypertension, in which the clinic reading is normal but the pressure is high during the rest of the day. Because individual readings vary so much, guidelines generally advise taking several and averaging them rather than relying on the first.

Ask a group of managers about health monitoring and most will describe a sensible scheme to keep staff well; ask a group of employees and many will describe something closer to surveillance. Both pictures can be accurate. Employers increasingly issue wearable devices, screen new recruits for cholesterol and blood pressure, and record sickness absence in fine detail, while software logs how often a delivery driver brakes hard or a call-centre worker takes a break. Whether this is care or control depends less on the technology itself than on the purpose it serves and on who is allowed to see the results. My own view is that the case for monitoring is strongest where it is tied to a specific hazard, and weakest where it becomes a general licence to inspect bodies and habits.

The best argument for surveillance is occupational disease. For decades, employers have tested the lung function of workers exposed to silica, taken blood samples from those handling lead and measured the hearing of people who work beside loud machinery. In many countries such monitoring is a legal requirement, and the justification is straightforward: where a job exposes people to a known hazard, surveillance is not an intrusion but a duty. The aim is to detect the earliest signs of harm, so that exposure can be reduced or the worker moved to other duties. Similar reasoning applies to safety-critical work. A train driver who is exhausted is a danger to the public, and monitoring hours and rest is a reasonable way of reducing that danger.

A second argument concerns the chronic conditions that cause most illness and premature death in wealthy countries. High blood pressure and type 2 diabetes can develop silently for years, and screening at work reaches people who rarely visit a doctor. Employers, insurers and governments all have an interest in earlier detection, and some workplace programmes do appear to raise employees' awareness of risk. This is where the case becomes less clear. A company that measures its staff's blood pressure is doing something different from one that measures the noise in a workshop: the first is looking at the person, the second at the environment.

Evidence about the wider benefits of workplace wellness programmes has been disappointing. One of the largest randomised evaluations, published in 2019, followed thousands of employees of a large American employer and found that those offered a wellness programme reported slightly healthier behaviour and valued the scheme, yet showed no significant improvement in clinical measures such as blood pressure or in rates of absence. Results of this kind suggest that such programmes rarely compensate for the effects of shift work, low pay, heavy workloads and jobs that require hours of standing or sitting. There is a risk that the language of wellness shifts attention from the design of work to the behaviour of the individual.

The privacy objections are equally serious, and they are not merely a matter of squeamishness. A continuous stream of data about movement, heart rate and sleep can reveal pregnancy, depression, heavy drinking or a diagnosis that an employee has chosen not to disclose. Even when a device reports only the number of steps taken, the pattern of those steps may be enough to show who was at their desk at eleven o'clock at night. Once collected, health information is difficult to keep within the purpose for which it was gathered: it may be merged with other records, examined during a dispute over promotion or exposed in a data breach.

Consent is often proposed as the answer, but in an employment relationship it is a fragile safeguard. Data protection law generally treats information about health as a special category that requires explicit agreement, and European regulators have observed that an employee who depends on the employer for a livelihood cannot easily refuse. Legislation nevertheless offers less protection than it appears to. A scheme described as voluntary becomes close to compulsory if participation carries a cash bonus or a discount on insurance, or if the colleagues who decline are noted by managers. Nor does anonymity solve the problem on its own: in a small team, an average of five people's data reveals a great deal about each of them.

There is also a risk of discrimination. If a wearable records an irregular heartbeat, or a screening test suggests early kidney disease, the information may influence decisions about promotion, transfer or redundancy, even when the condition has no bearing on the work. Well-meaning schemes can therefore punish people for being ill rather than help them to stay well, which is the opposite of what their designers intended.

None of this means that employers should stop taking an interest in health. It means that monitoring should be governed by three principles. The first is purpose limitation: if a risk is not created by the job, it is not the employer's business to measure it. The second is collective agreement, through trade unions or works councils, since individual consent is too weak to protect anyone. The third concerns control of the data: results should be held by independent occupational health staff, never passed to line managers, and destroyed once the purpose has been served.

The question, then, is not whether employers should care about the health of their staff, but who controls the information that care produces and what may be done with it. Limited, negotiated monitoring of specific occupational hazards is defensible and, in some industries, essential. Generalised surveillance of employees' bodies and habits is something else entirely, and the modest results of wellness programmes suggest that it does not even work very well.