John Medical Store

26/06/2016

Blood Pressure Measurement
What is blood pressure
Lateral pressure exerted on the vessel wall by the circulating blood; also referred to as systemic arterial pressure.

Calculation of blood pressure:
BP = CO x TPR
BP = blood pressure.
CO = cardiac output, volume of blood ejected from the ventricle in one minute.
TPR = total peripheral resistance, sum of the resistance of all peripheral vasculature in the systemic circulation.

Systolic pressure: Peak pressure that occurs in the artery following ventricular systole
Diastolic pressure: The level to which the arterial blood pressure falls during ventricular diastole.

Normal blood pressure is arbitrarily set at 120/80 mm Hg, although variations from this often occur in normal healthy people.
Factors affecting blood pressure
Cardiac output:
a) Increase cardiac output
Increase in blood volume
Physical exercise
Emotional excitement
b) Decrease cardiac output
Change of posture
Reduction in blood volume
Cardiac compression
Myocardial ischaemia and infarction

Peripheral resistance
a) Increase peripheral resistance
Chemoreceptor reflex (React to blood O2, CO2 and pH level) *
Baroreceptor reflex (React to vessel wall stretching)*
Renin-angiotensin mechanism

*Chemoreceptor and baroreceptors are located in aortic and carotid bodies. They adjust blood pressure through autonomic nervous system.
b) Decrease peripheral resistance
Vasovagal attack
Exercise

Others
Age, sleep, gravity, and any other underlying diseases.
Equipment for blood pressure measurement
Things to prepare for blood pressure measurement:
1. Stethoscope
2. Blood pressure set (Meter, pump, cuff of CORRECT SIZE in relation to the patient)

Before starting:
Wash your hand.
Introduce yourself to the patient.
Explain what you are doing, and possible, why you doing it, and obtain permission.
5 questions to be asked:
Smoking.
Caffeinated drink, such as coffee or tea.
Enough sleep?
Exercise.
Any Anti-hypertensive drugs.
ANY PAIN?

Example:
Good morning, I'm ###, 3rd year medical student. May I check on your full name and date of birth please?
The doctor had instructed me to measure your blood pressure today (because of your history of hypertension / the symptoms you are having / previous high blood pressure / normal check up / etc...). Have you had your blood pressure measured before? Would you like me to explain how this is done?
Basically, I will fit this cuff around your arm and inflate air into it, then slowly deflate to gain an estimate of your blood pressure from the meter reading. You may experience some temporary discomfort as the cuff may become quite tight. Please do let me know if it becomes too painful to continue.
Before we start, there are several routine questions I would like to ask you...
Locate pulses

Radial pulse:
Locate by following your thumb down to the wrist. lateral to the flexor carpi radialis tendon.
Comment on: rate, rhythm, volume and characteristic.

Brachial pulse:
Located medial to biceps tendon.
Taking the measurement
Palpating method
Patient's upper arm should be at the level of the heart.
Wrap the cuff around upper arm with bladder centred over the brachial artery.
Feel for radial pulse.
Inflate cuff until radial pulse is impalpable.
Increase pressure by 20mmHg then deflate until radial pulse is back.
The measurement is the estimated systolic pressure.
This should be follow by auscultating method as shown below to obtain a more accurate estimation of blood pressure

Auscultating method

Auscultating Method
Place stethoscope over the brachial artery.
Inflate the cuff until the measurement reaches the estimated systolic pressure + 20 mmHg.
Deflate SLOWLY and listen to the first “click” sound => this is the systolic blood pressure.
Continue deflate until the “clicking” sound disappear => final reading is the diastolic blood pressure.
Importance of Palpating method
It is important to perform palpating method before auscultatory method to:
1. Prevent discomfort from unnecessary high cuff pressure.
2. Avoid auscultatory gap (the sounds disappear just below the systolic pressure and reappear before diastolic pressure, can lead to underestimate of systolic blood pressure)

Korotkoff Sound
5 phases sounds will be heard as the cuff is slowy released, which are called the Korotkoff sounds:
Phase 1: 1st appearance of sound (systolic pressure)
Phase 2 and 3: increase volume
Phase 4: muffling of sound
Phase 5: disappear of sound (diastolic pressure)

Reference
NJ Talley, SO Connor, Clinical Examination: A systematic guide to physical diagnosis, 6th Edition, 2010.

26/06/2016

THE ORIGINS OF PUBLIC HEALTH

Historians once commonly believed that plague was a primary cause of the breakdown of medieval society and the transition to the modern era. Although this is no longer widely accepted, there is no denying that plague did have a powerful impact. Arguably the most significant of its effects was the stimulus it provided to the development of public health, and, more speculatively perhaps, to the more general idea that the purpose of government was to formulate policy, not just maintain order. The idea that the government could exercise a regulatory and policy-making function was certainly not unprecedented in the late fourteenth and early fifteenth centuries, but the horrific consequences of repeated plague outbreaks made matters of health a particular focal point of concern and regulation.

As early as 1348, the town council of Venice appointed three of its members as a special commission to devise measures against the plague that had broken out there, and, in general, highly developed Italian cities like Florence, Milan, and Genoa were among the earliest to formulate measures against the plague. Many European cities and principalities north of the Alps followed suit during the next 150 years. The measures taken by these boards included the institution of quarantine, a practice whereby plague victims were shut up in their houses, together with their families and servants, if they had any. Quarantine could also be placed on entire towns and cities, and because such bans could last for weeks or even months, a declaration of quarantine had serious consequences for trade and economic well-being. Plague ordinances further specified how those who had died of plague should be buried and what should be done with their personal possessions—clothing and bedding could be burned, for example. More controversially, they also prohibited public gatherings of different kinds, including church processions. Since such public gatherings were a major component of medieval Catholic spirituality, their prohibition by secular authorities was a recurrent source of conflict with the church.

Throughout the fifteenth century, most of the health commissions charged with dealing with plague remained temporary institutions, dissolving as soon as the threat posed by the current epidemic had subsided. But during the sixteenth century, more permanent health magistracies began appearing in northern Italian cities. The responsibilities given these boards gradually evolved to cover not only times of emergency but also the more routine supervision of public health. Justified by a desire to forestall future outbreaks of plague and building on prior medieval attempts to enforce sanitary standards in larger cities (in some cases dating much further back than the 1340s), these health boards began formulating more comprehensive sanitary measures to control such things as the cleaning of streets and dumping of wastes. Beggars and Jews, who were suspected of being transmitters of disease, were often singled out for unwelcome attention.

A somewhat different system evolved in German-speaking central Europe during the sixteenth and seventeenth centuries. There, towns and principalities began appointing a local physician or surgeon to the partially salaried post of physicus. Their primary responsibility normally involved providing medical care for the poor, but physici were also charged with enforcing sanitary regulations, instructing and supervising other practitioners, and conducting medical-forensic inquiries, among other functions. In effect, these practitioners served as the instruments for the enforcement of public health ordinances, while at the same time gathering information about local health conditions that could be transmitted back to the political authorities.

26/06/2016

PATTERNS OF DISEASE

Death was a common occurrence in the early modern period, a fact that colored nearly every aspect of social and cultural life. Nor was it just the elderly who expected to die; infants and children died at such high rates that someone could be counted fortunate just to reach the age of twenty-one, not to mention sixty or seventy. This depressing fact was not lost on contemporaries. "Of each 1,000 people born," wrote a German physician in 1797, "24 die during birth itself; the business of teething disposes of another 50; in the first two years, convulsions and other illnesses remove another 277; smallpox . . . carries off 80 or 90, and measles 10 more." Of every 1,000 people born, he concluded, "one can expect that only 78 will die of old age or in old age." Although we cannot verify the accuracy of these numbers, there is no disputing the appallingly high mortality rates they indicate. Available records of baptisms and burials from local churches suggest that in countries such as France and Denmark, deaths of infants (that is, children under the age of two) from all causes could climb as high as two hundred or more deaths per thousand births.

A variety of factors contributed to these high mortality rates, including the prevalence of malnutrition and intestinal parasites. Although these may have only rarely caused death directly, they undoubtedly weakened the body's defenses against disease. More directly responsible were infectious diseases like smallpox and measles, mentioned in the quotation above, along with other serious childhood diseases like diphtheria, whooping cough, and dysentery.

The most dangerous disease of all was the plague, which first struck various parts of Europe between 1347 and 1351 and returned to afflict almost every generation until the very end of the seventeenth century. The disease is believed to have begun in China and then spread along trade routes in Central Asia in the early 1340s. By 1346 it had reached the Crimean city of Caffa, and from there it was brought to Sicily and southern Italy. Once established there, plague spread, again along trade routes, to other parts of Europe. Skepticism has grown in recent years over whether the plague (caused by the bacterium Yersina pestis ) was exclusively bubonic plague, induced in its victims by the bite of a flea, or whether it was mixed with a more dangerous airborne form known as pneumonic plague. It is possible too that one or more other diseases were also part of the mix. Whatever its precise cause, there can be no question that plague hit many parts of Europe hard. Over the entirety of Europe, it is estimated that the first onset of plague killed approximately 25 percent of the population, although actual mortality varied considerably from place to place. Even as late as the seventeenth century, outbreaks of plague continued to hit with devastating impact. In 1656–1657, the Italian city of Genoa lost 60 percent of its population of 75,000 to plague—a horrific, although unusually high, mortality rate—while between 1609 and 1611 about 42 percent of the residents of the Swiss city of Basel (population 15,000) caught the plague and 62 percent of those victims died.

A second serious disease, syphilis, appeared for the first time in Europe at the very end of the fifteenth century. While having nowhere near the demographic impact of plague in terms of deaths caused by it, syphilis was serious enough, especially in the virulent form in which it first appeared. The disease was first reported during the French army's campaigns in Italy during 1494–1495 (hence the common name given it, the "French Pox"), and from there it spread rapidly throughout Europe. Sufferers from syphilis, reported the German scholar Ulrich von Hutten in the early sixteenth century, "had boils that stood out like acorns, from which issued such filthy stinking matter, that whosoever came within the scent believed himself infected." The stinking stain described by von Hutten could have been more than just physical, for it was soon determined that syphilis was s*xually transmitted, thus giving the disease extra significance as an apparent punishment for sinful promiscuity.

26/06/2016

IDEAS OF HEALTH AND ILLNESS

The dominant medical thinking of the early modern period saw health as dependent on a particular balance in the body's four humors, known conventionally as blood, phlegm, black bile, and yellow bile. Each individual humor, in turn, manifested a distinctive combination of qualities from the pairs wet/dry and cold/hot. Thus, blood was believed to be hot and wet, yellow bile, hot and dry, and so on. The balance of humors required to maintain health was highly individual, depending on someone's age, s*x, local environment, diet, work, lifestyle—in principle, almost anything could influence health. Excessive exercise, for example, could cause the body to heat up, resulting in an excess of blood or yellow bile. Scholars, on the other hand, were thought to suffer from particular diseases resulting from their having too little exercise and too much brainwork. The prevention of illness and its cure depended in principle on the same idea, whereby the practitioner sought to maintain or restore the proper humoral balance. The application of many treatments, such as the use of bloodletting or emetics (agents that cause vomiting), can be understood as working in this way.

Over against these doctrines concerning pathology and therapeutics must be set a partially separate set of ideas concerning what we now call physiology, the functions of the living body. The body's functions were thought to be governed by three principal organs: the liver, which converted nutritive juices produced by digestion into blood, which was then sent via the venous system to all parts of the body and nourished it; the heart, which mixed air taken in by the lungs with some blood, producing vital spirit, which was distributed throughout the body by the arteries and governed vital processes such as motion, breathing, and digestion; and the brain, which produced animal spirits, responsible for the higher functions of sensation and consciousness, and which traveled throughout the body via the nerves. Although not entirely divorced from the humoral doctrines that molded thinking about health and illness, the theories governing physiology were formulated to answer a distinctive and separate set of questions, such as what breathing does or how the movement of muscles occurs.

The source of many of these ideas was a collection of writings attributed to the ancient Greek physician Hippocrates (c. 460 b.c.e.–375 b.c.e.), especially as interpreted by the later Greek physician Galen (129–199? c.e.). Very few of Hippocrates' and Galen's writings were available in Latin translation during the early Middle Ages, but a far richer view of Hippocratic and Galenic medicine started appearing in Latin-speaking Europe at the end of the eleventh century, when translations of Arabic medical writings were made in southern Italy and Spain. These encyclopedic compendia of ancient medicine became the basis for medical teaching in the universities that began appearing at the end of the twelfth century.

By the early sixteenth century, medicine was a widely accepted part of the university curriculum, with the teaching of theory and practice based largely on Hippocratic and Galenic precepts, as interpreted and synthesized by medieval Muslim scholars. A second wave of translations, beginning in the late fourteenth century and inspired by the humanist cultural program for the restoration of classical antiquity, produced a wave of Latin translations from ancient Greek manuscripts, bypassing the mediation and (so the humanists claimed) the barbarism of earlier Muslim translators and commentators. The output from all this effort is astonishing: between 1500 and 1600, there are said to have been approximately 590 different editions of Galen's writings. To a surprising extent, these new translations from Greek sources did little to change the curriculum or the dominant medical theories. Yet in one important area, anatomy, the recovery of Galen's writings, especially his On Anatomical Procedures (first published in 1531), a guide to dissection, did lead to dramatic changes in medical thinking.

The conduct of dissections as part of the teaching of anatomy was a well-established, if also a sporadic, part of the medical curriculum. Well before 1500, medical scholars had used dissection as a means of engaging in critical dialogue with their ancient and medieval Muslim predecessors, to the extent that these sources were available to them. The appearance of On Anatomical Procedures in Latin translation, however, gave to humanistically inclined physicians an impeccably ancient source of authority for the practice of dissection, as well as practical tips for doing so. Consequently, anatomy and the practice of dissection acquired a status far exceeding what it had enjoyed before, and knowledge of human anatomical structure became a focal point of research interest. This burst of activity culminated with the publication of De Humani Corporis Fabrica (1543; On the structure of the human body), by Andreas Vesalius, the most renowned anatomist of the era. Vesalius's richly illustrated text presented itself as an extended critique of Galen's claims about anatomy, offering its readers a far more visually concrete picture of the body than anything previously available.

The critique of Galen's anatomical ideas, however, did not translate immediately into a broader abandonment of his physiology, in part because his theories about the body's functions made a great deal of sense in the context of physicians' experiences with the bodies of their patients. Only in the greatly changed circumstances of the seventeenth century, when a new generation of scholars deployed a new "mechanical" philosophy based on experiment to overthrow the entire edifice of ancient natural philosophy and the kinds of explanations it offered, did physicians shift from engaging in their centuries-long critical dialogue with their ancient sources to thinking about the body's functions in ways that departed significantly from ancient models. The most important among these later physicians was William Harvey (1578–1657), a highly skilled anatomist and experimentalist whose carefully designed investigations into the function of the heartbeat, published in 1628 as Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (An anatomical essay on the motion of the heart and blood in animals), directly attacked the physiological role assigned to the heart by Galen, suggesting instead that the heart acts as a pump, distributing blood to the body through the arteries and receiving it back again from the veins.

26/06/2016