The completion of repatriation, September 1947 to June 1948

a) Equipment

i. Cuff bladder size: It has been observed that a cuff with too narrow a bladder will over estimate blood pressure levels in children and adults.¹¹³ Most authorities now agree that a cuff bladder width that is approximately 40% of arm circumference most closely approximates intra-arterial readings.^5,113

ii. Stethoscope: proper use of the bell, with smaller bells for smaller arms and care to achieve a seal with the lightest possible pressure, should achieve the best result.¹¹⁴

b) Subject factors

i. Activities before and during measurement.

If undertaken within 30 minutes before blood pressure measurement, such stimuli as food, alcohol, caffeine, nicotine, and exercise lead to high values.⁸Crossing one’s legs may raise measured blood pressure, as may talking or performing mental tasks during measurement.¹¹³Unless the goal is to quantify such activities, as in ambulatory blood pressure monitoring, children should avoid eating and exercise for 30 minutes before a reading, and they should rest quietly with legs uncrossed for 5 minutes before and throughout blood pressure measurement.⁹⁷

ii)Age and anthropometric indices: There are many studies which confirmed that blood pressure increases with age.^60,63,72Also a linear relation have been established between anthropometric indices (especially weight and height) and a mean blood pressure level.^2,9,57 c) Environmental factors

i. Time of day: It has been documented from studies in children who have used ambulatory blood pressure monitoring that blood pressure is lowest during sleep.^115,116Some data suggest two peaks of blood pressure during the day, in the late morning and in midafternoon.¹¹⁷It is

44

prudent to record the time of day when blood pressure is measured to control for it or to examine its effects in data analysis.⁹⁶

ii. Season and Temperature: Few studies^114,118 examined the effect of season and ambient temperature on blood pressure in children. Priners et al¹¹⁴and Jenner et al¹¹⁸agreed that systolic pressure rises substantially with decreasing ambient temperature, but their finding on diastolic pressure were divergent. As with time of day, recording of ambient temperature is necessary should an investigator wish to control for the factor in analyses of data.⁹⁷

d) Observer or Technique factors

i. Standardization and Training: Observer bias has been identified as an important factor in many large epidemiological studies involving blood pressure measurement.^119,120 It is important to note that standardization, restandardization, and certification of observers are vital to achieving valid result in any study of blood pressure.

ii. Observer Bias: Digit preference is the tendency for observers to record round numbers as the terminal digit of any reading. The most common terminal digit is zero in studies that use the standard mercury sphygmomanometer.¹¹⁹The effect of digit preference can be seen most readily in studies involving classification into categories. For example in a study in which subjects are to be included if diastolic pressure is least 90 mmHg, rounding up readings of 88 mmHg to 90 mmHg will misclassify some individuals into group to be included for study.⁹⁷ More important for studies in children, which usually do not involve categorization, is bias resulting from knowledge of earlier readings. When taking multiple readings over several minutes, observers tend to record readings that resemble the previous readings. This bias tends to falsely reduce intrapersonal variability and therefore may actually obscure associations of blood pressure with other variables.¹¹⁹Although standardized training may

45

minimize those biases, use of devices other than the standard mercury sphygmomanometer may also be helpful.⁹⁷

iii) Measurement of Diastolic Pressure: For at least 50 yrs, there has been a controversy over whether muffling (korotkoff phase 4[k4]) or the disappearance korotkoff sounds (k5) should be used for measurement of diastolic pressure in children. Although apparently settled for adolescents and adults, in whom k5 is generally accepted, the controversy continues for children under the age of 13 years. Some favour k4 in this age group because it is more closely approximate intra arterial pressure and because k5 may be heard as low as 0 mmHg, especially in the presence of undue pressure on the stethoscope head.¹²¹Population data in children² and risk associated epidemiological data in adult¹²²have established the fifth korotkoff sound (k5), or the disappearance of korotkoff sounds, as the definition of DBP.

Although the current evidence seems to favour the use of k5, it is prudent to record both k4 and k5 in epidemiological studies.⁹⁷

DIAGNOSIS OF HIGH BLOOD PRESSURE

Hypertension is generally diagnosed on the basis of a persistently high blood pressure.

Usually this requires three separate sphygmomanometer measurements.²Initial assessment of the hypertensive patient should include a complete history and physical examination.

Exceptionally, if the elevation is extreme, or if symptoms of organ damage are present then the diagnosis may be made, investigations and treatment started immediately.

Once the diagnosis of hypertension has been made, physicians should attempt to identify the underlying cause based on risk factors and other symptoms, present. Secondary hypertension is more common in pre-adolescent children, with most cases caused by renal disease. Primary or essential hypertension is more common in adolescents and has multiple risk factors, including obesity and family history of hypertension.⁴⁵

46

Laboratory tests can also be performed to identify possible causes of secondary hypertension, and determine if hypertension has caused damage to the heart, eyes, and kidneys. Additional tests for diabetes mellitus and high cholesterol levels are also performed because they are additional risk factors for the development of heart disease require treatment. Test typically performed are as below.⁵

Table I Basic Evaluation of Confirmed Hypertension.⁵ Study or Procedure Purpose

BUN, Cr, electrolyte, urine culture To rule out renal disease and chronic pyelonephritis and urinalysis

Complete blood count R/O Anaemia, consistent with chronic renal disease Renal USS R/O renal scar, congenital anomaly, disperate renal Size

Evaluation for co-morbidity

FBS, Fasting lipid panel Identify hyperlipidaemia, metabolic abnormalities Drug screen Identify substance that might cause hypertension

Polysomnography Identify sleep disorder in association with hpn Evaluation for target organ damage

Echocardiogram Identify LVH and other cardiac involvement Retinal exam Identify retinal vascular changes

Further evaluation as indicated

Ambulatory BP monitoring Identify white coat hypertension, abnormal diurnal BP

47

pattern, BP load

Plasma renin determination Identify low renin, suggesting mineralocorticoid related Disease

Reno vascular imaging

 Isotopic scintigraphy (renal scar)

 Magnetic resonance angiography

 Duplex Doppler flow studies

 3 dimensional CT

 Arteriography: DSA or classic

Plasma and urine steroid level Identify steroid mediated HTN

Plasma and urine catecholamines Identify catecholamine mediated HTN

Adapted from National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The Fourth Report on the Diagnosis, Evaluation and Treatment of High Blood Pressure in Children and Adolescents. Paediarics 2004; 114 (2 supple 4^th Report): s555 – 76

COURSE AND PROGNOSIS

The natural history of essential hypertension that is detected during childhood or adolescence is under investigation in several large long term population studies.¹²³Many of these children continue to have essential hypertension as adults. In adult with essential hypertension, drug therapy has been shown to be beneficial in reducing the incidence of congestive heart failure, renal failure and stroke.¹²³

The prognosis of a child with secondary hypertension is primarily determined by the nature of the underlying disease and its responsiveness to specific therapy.¹²³Survival in

48

patients with underlying chronic renal disease is determined by the patient’s response to dialysis and renal transplantation.¹²³Abdurrahman et al²⁶reported overall mortality of 28% in his study in Northern Nigeria that he attributed to lack of facilities or manpower for haemodialysis and kidney transplant.

PREVENTION OF HIGH BLOOD PRESSURE

The degree to which hypertension can be prevented depends on a number of features including current blood pressure level, sodium/potassium balance, detection and omission of environmental toxins, changes in end/target organs(retina, kidney, heart, among others), risk factors for cardiovascular diseases and the age at diagnosis of pre hypertension or at risk for hypertension. A prolonged assessment in which repeated measurements of blood pressure are taken provides the most accurate assessment of blood pressure levels, following this, lifestyle changes are recommended to lower blood pressure, before initiation of pharmacotherapy.⁸¹

Population approaches to prevention of essential hypertension include reduction in sodium intake and an increase in physical activity through school based programs.¹²³ A substantial body of evidence strongly supports the concept that multiple dietary factors affect BP. Dietary modifications that effectively lower BP are weight loss, reduced salt intake, increased potassium intake, and consumption of diet rich in fruits and vegetable, low fat dairy products, reduction in saturated fat and cholesterol, called the Dietary Approaches to stop Hypertension (DASH) diet.¹²⁴

49 OBJECTIVES OF THE STUDY

GENERAL AIM: To determine the blood pressure profiles among primary school children in Kano metropolis, Kano State.

SPECIFIC OBJECTIVES:

1. To determine the systolic and diastolic blood pressure of primary school children in Kano metropolis.

2. To determine the relationship between the systolic and diastolic blood pressure and the age, and body mass index (BMI) of primary school children in Kano metropolis.

3. To determine the prevalence of elevated blood pressure among primary school children in Kano metropolis.

4. To determine the relationship between the systolic and diastolic blood pressure and socioeconomic status of the parents.

50 MATERIALS AND METHOD STUDY SITE:

The study was conducted in Kano metropolis, Kano State. Kano is located in the Sudan savannah belt of Nigeria. It lies between latitude 12.05^oN and longitude 8.51^oE with an area of 20,760 square kilometres.¹²⁶ Kano is one of the original Hausa States dating from 900 AD, and is the most populated state in Nigeria with an estimated population of 9.3 million and population density of 450 people per square meter according to 2006 census estimate.¹²⁶ Kano Metropolis is made up of eight LGAs; namely Tarauni, Dala, Fagge, Gwale, Kano municipal, Nassarawa, Kumbotso and Ungogo. It has an area of 499 km² with a population of 3,628,861 according to 2006 census.¹²⁶ Kano city has 2 seasons: the wet season between June and September/October with an average temperature of 29^oC and an average annual rainfall of 869 mm; The dry season include the cold harmattan period between October and February, with average temperature of 22^oC; and the hot and dry period from March to May with average temperature of 32^oC. Kano city has an annual average humidity of 50%.

The indigenous Hausa and Fulani tribes mostly occupy Kano city, with a substantial number of other Nigerian ethnic groups like the Yorubas, Ibos, and Igalas at Sabongari, Brigade and newer settlements. The majority of the indigenous population are Muslims, whose main occupations include trading, farming and the civil service. There are several public and private hospitals within the metropolis including four State Specialist Hospital and the Teaching Hospital located within Tarauni local Government Area.

There are several institutions of higher learning including Federal and State Universities, a Federal college of education and a state polytechnic.

51 STUDY DESIGN

The study design was descriptive and cross sectional.

STUDY POPULATION

These were apparently healthy primary school children aged 6-14 years. The minimum age for admission into primary schools is 6 years and by the age of 14 years, most of the pupils would have completed their primary school education. This forms the basis for the definition of the age group involved in this study.

STUDY PERIOD

The study was carried out over a period of nine months (February to October 2013) INCLUSION CRITERIA

1. Apparently healthy children aged 6 - 14 years attending primary schools in Kano Metropolis.

2. Children not on any medications that are known to affect blood pressure like steroids, antihypertensive drugs, nasal drops etc

3. Those whose parents/guardians consented to the study.

EXCLUSION CRITERIA

a. Children on treatment for hypertension or diabetes.

b. Children with macroscopic haematuria at time of study.

c. Those with generalized body swelling.

52 DEFINITION OF TERMS

a. Elevated Blood Pressure is defined as average SBP and/or DBP that is greater than or equal to the 95^th percentile for sex, age, and height on three or more occasions,⁵ using normogram generated from the study.

b. Pre hypertension is defined as average SBP or DBP levels that are greater than or equal to the 90^th percentile, but less than the 95^th percentile.⁵

c. Systolic blood pressure is the blood pressure in vessels during a heart beat.⁷⁷ d. Diastolic blood pressure is the pressure between heart beats.⁷⁷

ETHICAL APPROVAL

Institutional approval for the study was obtained from State Primary Education Board.

Ethical clearance was obtained from Medical Research Ethics Committee of Aminu Kano Teaching Hospital. Permission was also obtained from the headmasters of the respective schools. Written informed consent/assent was obtained from parents / guardians of each child.

SAMPLE SIZE DETERMINATION

The sample size was estimated using the standard formula for cross sectional study¹²⁶ n=z²pq

d²

where n=minimum sample size

z=standard normal deviate, usually set at 1.96 which corresponds to 95% confidence interval

p=the prevalence of hypertension among children in Ibadan=4.8%¹

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q=complementary probability to p (1-p=0.952) d=Absolute precision = 5%

Thus n= (1.96)²x0.048x0.952 0.05²

n=70

A contingency of 10% was added, thus, a total 2000 subjects were recruited.

SUBJECTS SELECTION

The 2000 subjects were selected for the study using multistage sampling technique.

Stage 1, Three Local Government Areas (30%) were selected randomly by simple balloting from eight Local Government Areas in Kano metropolis. Thus; Kumbotso, Nassarawa and Tarauni local Government Areas were selected.

Stage 2, With the help of the list of public and private primary schools in the Local Govt Areas selected,⁸² one primary school each, in both public and private schools were selected by simple random sampling from each political wards of the selected Local Governments Areas. Thus; a total numbers of 66 schools were selected as follows:

Table II statistic of schools in the selected Local Govt

LOCAL GOVT PUBLIC SCHOOLS PRIVATE SCHOOLS TOTAL

Tarauni 10 10 20

Kumbotso 11 11 22

Nassarawa 12 12 24

Total 33 33 66

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Stage 3, In order to achieve the required sample size, proportionate allocation was given to each school depending on its population in relation to other schools. The number of pupils selected from each school was determined as follows;

Pa=na x 2000 nT 1

Where Pa=no. of pupils to be selected in primary school a na=total number of pupils in primary school a

nT=total number of pupils in 66 selected primary schools.

For example; Babban giji Special Primary School has a total of 1579 pupils, number of pupils to be selected can be calculated as follows: Pa=1579 x 2000

46589 1 Pa=68.

Thus; the numbers of pupils selected in each school are shown below:

Table III: Distribution of Selected Schools and the Corresponding Selected Pupils

S/N Name of the School Population of the Selected School No of pupils Selected A Kumbotso Local Govt

i)PUBLIC

1 Naibawa Sp Pri School 1030 44 2 Danladi Nasidi Pri Sch 1180 51 3 Danmaliki Pri School 1058 45 4 Kumbotso Sp Pri Sch 1214 52 5 Panshekara Sc Pri Sch 1150 49 6 Chalawa Pri Sch 1115 48 7 Kuruken Sani Pri School 1280 55 8 Yusuf Islamiyya Pri Sch 750 32 9 Gurungawa Pri School 1145 49 10 Jannatul firdaus Pri Sch 856 37 11 Chiranchi Sp Pri School 1084 47

55 ii) PRIVATE

1 Liberty International 368 16 2 Arewa Star Academic 358 15 3 Hamszabent International 338 15 4 Lipson Quality 248 11 5 Nagarta Target 285 12 6 Salmat Prime Nur/Pri 375 16 7 Victory Academy 278 12 8 The Light International 308 13 9 Radiance International 264 11 10 Progressive Nur/Pri Sch 258 11 11 Gulf Group of Schools 218 10 B Nassarawa Local Govt

i)PUBLIC

1 Dakata Sp Pri Sch 1260 54 2 Ladanai Pri Sch 1384 59 3 Gawuna Sci and Tech Pri Sch 1230 53 4 Maisalati Islamiyya Pri Sch 650 28 5 Zamzam Pri School 1140 49 6 Imam Kabiru Islamiyya Pri Sch 812 35 7 Brigade Girl Model Pri Sch 987 42 8 Tagarji Primary School 1033 44 9 Kawaji Jigirya Sp Pri Sch 1244 53 10 Giginyu Sp Pri School 1089 47 11 Nurulhayat Islamiyya Pri Sch 780 33 12 Tokarawa Sp Pri School 1166 50 ii)PRIVATE

1 Alhalim Sharon Nur/Pri Sch 425 18 2 ABC Play Group 248 12 3 Augustine Pri School 356 15 4 Palm Group International 269 12 5 Accada Tudun Wada 328 14 6 ABU Science 405 17 7 Comprehensive Grammar 380 16 8 Charis Preparatory 188 10 9 Dolphine International 368 16 10 Liberty International 288 12 11 Bright Future Academy 308 13 12 Assalam private Nur/Pri 220 10

56 Tarauni Local Govt

i)PUBLIC

1 Kundila Pri School 1258 54 2 Gyadi Gyadi Sp Pri Sch 1360 58 3 Unguwa uku Sp Pri Sch 1045 45 4 Babbangiji Sp Pri Sch 1579 68 5 Hausawa Sp Pri Sch 1150 49 6 Darmanawa Pri School 1260 54 7 Daurawa Sp Pri Sch 1350 58 8 Surutul Auladi Islamiyya 780 33 9 Unguwar Gano Sp Pri Sch 1060 46 10 Usman bin Affan Islamiyya 890 38 ii)PRIVATE

1 Aishatu Lamido Kundila 240 10 2 Emphatic Nur/Pri Sch 320 14 3 Brain Group of School 410 18 4 Maitama Nur/Pri School 312 13 5 Juliet Nur/Pri School 280 12 6 Muazzam International 260 11 7 Zenith International 308 13 8 AT International Nur/Pri 345 15 9 Agreed Foundation 284 12 10 Alheri Nur/Pri School 380 16 TOTAL 46589 2000 Nur= Nursery Pri=primary Sch=school Sp=special

Stage 4, In each school, in order to achieve the number of pupils required, proportionate allocation was given to each class from primary one to six depending on the population of each class as follows;

P1=p1T X pT Pn 1

Where p1=no of pupils to be selected in class primary one p1T=total number of pupils in class one

pn=total number of pupil in the school

57 pT=sample size required in that school.

Eg in Babban Giji primary school P1=232 X 68 1579 1 P1=10

Stage 5, in each class, using the class registers, and with the assistance of the class teachers, the pupils in all arms of the various classes (eg classes 1A, 1B, 1C) were grouped together and stratified on the basis of age. Subjects were proportionately chosen from each age cohort using sampling ratio to make up the number to be chosen from that class.

E.g age cohort 7 yr to be selected in classes 1 = TC1A7yr x TC1Sel TC1 1 Where TC1A7yr = total no. Of 7 yr age cohort in classes 1

TC1 = total no. Of pupils in classes 1

TC1Sel = total no. Of pupils to be selected in classes 1 Eg in Babbangiji Pri Sch = 116 x 10

232 1 =5

5 pupils were selected in 7 yr age cohort among pupils in classes 1.

Sampling ratio was determined as follows; age cohort 7 yr to be selected in class 1(5): total no. of 7 yr age cohort in class 1(116). Therefore sampling interval was every 23^rd pupil.

The starting point was determined by simple balloting of the names arranged in alphabetical order of that age cohort. On occasion where the subject selected did not meet the inclusion criteria of the study, the process was repeated to replace such subject.

These steps were repeated for other classes and also other schools until a total number of 2000 pupils were recruited.

58 INSTRUMENTS

1. Mercury sphygmomanometer (Accuson)^R hospital model BS 274 was used for measurement of blood pressure. Cuff sizes of 9cm used for <12 yrs and 13 cm used for ≥ 12 yrs old were used for the study.

2. Weylux weighing scale ( model 424) was used in weighing each pupil.

3. ACCUSTAT^TMROSS Stadiometer was used to measure the heights of the study subjects.

4. A simple questionnaire was used to obtained information about the subject including personal bio data, symptoms (if any), drug history, past medical history and family history.

Part 1 of the questionnaire was filled by the parent/guardian along with their consent form.

For those who were not literate, it was requested that the consent form and questionnaire should be read by a literate relation or neighbour and to be communicated to them in a language best understood.

METHODS

The researcher carried out a general examination on all selected pupils. The weight and height were measured by the research assistant who had prior training on weight and height measurement, while blood pressure and pulse rate were measured by the researcher.

WEIGHT

The weight of the pupils was taken by a research assistant with the use of a Weylux weighing scale with an accuracy of 100 g. Each pupil was allowed to stand on the scale barefooted with light clothing only. Measurements were recorded to the nearest one tenth of a kilogramme (0.1 kg). The scale was cross checked using a known weight and any fine adjustment was made at the beginning of each enrolment session.

59 HEIGHT

The height was measured with the use of an ACCUSTAT^TMROSS Stadiometer.

The subjects were asked to stand erect with the heels, buttocks, upper part of the back and the occiput against the stadiometer. The heels were in an apposition and the arms were hanging naturally by sides, the external auditory meatus and the lower border of the orbit were in a plane parallel to the floor.¹²⁸The measurement was taken to the nearest one-tenth of a centimetre (0.5cm)

PULSE RATE

The subjects were asked to sit first, rest the arm. The radial artery at the wrist was carefully palpated with the tips of the fingers, the subject’s forearm being pronated and the wrist slightly flexed. The rate was counted over sixty (60) seconds after any quickening due nervousness in the subject had subsided and the rate and rhythm had been steady.¹³¹

BLOOD PRESSURE

Two instruments were used for measuring blood pressure: a sphygmomanometer and a stethoscope.¹³²

The following precautions were taken when using mercury sphygmomanometer.

1. The mercury was clearly visible, not obscured by oxidized mercury on the inside of the glass.¹³²

2. Before inflation the mercury level was at zero.¹³² Cuff sizes

By convention, an appropriate cuff size is one with an inflatable bladder width that is at least 40 percent of the arm circumference at a point midway between the olecranon and the

In document British attitudes towards German prisoners of war and their treatment: 1939 48 (Page 193-197)