Physical examination procedures

9.1.1

The evidence base: When and how should blood pressure be measured

Blood pressure (BP) should be measured when fundus features suggest hypertension. These include hypertensive retinopathy, choroidopathy, optic neuropathy, arterial and venous occlusive disease, embolic events, and arteriolar macroaneurysm formation. Wong and Mitchell proposed a simplified classification of hypertensive retinopathy that combined the Keith–Wegener–Barker classification of stage I and II into a ‘mild’ category ( Table 9.1 ). However, not all patients with hypertension develop retinopathy. Even after 10 years, 70% of patients show either no retinopathy or only slight constriction and arteriolosclerosis. In addition, the inter-rater reliability of detection and classification of hypertensive retinopathy with ophthalmoscopy has been shown to be poor. ^, Barnard showed that referral made on fundus signs alone resulted in a 78% false–positive rate in patients between 45 and 64 years of age. BP should also be measured when there is a positive family history because with this history the risk of developing hypertension is increased two to four times. A history of cardiovascular disease, cerebrovascular disease, obesity, physical inactivity, heavy alcohol intake, smoking, diabetes mellitus, and hyperlipidaemia are indicators that BP measurement may be useful. The presence of unexplained headaches, particularly pulsating, suboccipital headaches that subside during the day, particularly in an older patient, may suggest acute hypertension and thus the need for BP measurement.

It can be useful to measure BP in a patient who is being treated for hypertension, depending on the patient. For example, if a patient is taking medication regularly and having their BP regularly monitored, then there would be little need for you to measure BP. If, however, the patient stopped taking their medication 6 months ago owing to an adverse reaction and has not seen their physician to follow up, it would be prudent to take a BP reading and advise the patient accordingly even in the absence of abnormalities on the ocular fundus examination.

It can also be useful to measure BP in patients with ocular hypertension, glaucoma suspects, and patients with glaucoma. High BP is associated with high intraocular pressure. Hypotension (i.e., low BP) should be considered in patients with normal tension glaucoma or in patients with glaucoma who are experiencing progressive loss of visual field despite treatment adherence. This is hypothesised to be as a result of impaired ocular perfusion pressure (the difference between the mean arterial BP and the intra-ocular pressure) especially at night when BP drops and intra-ocular pressure is raised. In addition, some patients with hypertension may be over-treated, which can result in impaired ocular perfusion pressure. Ambulatory BP monitoring in these patients might be helpful in determining if there are significant nocturnal dips that are contributing to the disease. A survey by Wolffsohn et al. found that the majority of primary care physicians would appreciate receiving a report of their patients’ BP if it was found to be over 140/90. The usefulness of routine BP screening as an add-on to the eye examination of older patients needs further research. The negative aspects of false–positive results need to be considered ( section 1.3 ).

Most devices for measuring BP occlude a blood vessel in an extremity (usually the arm, wrist, or finger) with an inflatable cuff then measure the BP either by detection of Korotkoff sounds or oscillometrically. In the auscultatory method a stethoscope is used on the brachial pulse to detect Korotkoff phase I sound (the systolic BP) and the cessation of the Korotkoff phase V sounds (the diastolic pressure) on the deflation of the cuff. In this method the sphygmomanometer used to measure the pressure can be mercury, aneroid, or electronic with a digital display. Mercury sphygmomanometers have largely gone out of use owing to concerns about toxicity of mercury for users, personnel, and the environment. Aneroid devices are inexpensive and portable but the bellow-and-lever system used to measure pressure is subject to jolts and bumps, which can lead to false readings. Aneroid devices require regular calibration and should be checked against a mercury sphygmomanometer every 6 months.

An alternative to the auscultatory method are automated (oscillometric) sphygmomanometers, which are very simple and easy to use ( Fig. 9.1 ). They detect the variation in pressure oscillations caused by arterial wall movement under the cuff to measure systolic, diastolic, and mean arterial BP. Canadian, US, European, and Australian Guidelines for diagnosis and measurement of hypertension recommend using validated automated (oscillometric) upper arm devices over auscultation for in-office and at-home measurements. ^, Oscillometric measurements improve the repeatability of the measurements, are closer to ambulatory measurements, and the results are lower than conventional methods. ^, Ambulatory measurements may be better predictors of cardiac outcomes than conventional methods. Patients are usually left alone in the room and multiple measures are taken one to two minutes apart. This has the advantage of not taking up clinician time. These devices should not be used in patients who have arrhythmia. Thresholds for conventional sphygmomanometry should not be applied to automated readings. The definition of hypertension when using these devices is the same as for ambulatory methods at normal being <135/85. ^,

9.1.2

Automated oscillometric blood pressure measurement

• 1.

  Have the patient remain seated quietly with feet on the floor and back against a chair (see Fig. 9.1 ) for at least 5 minutes before BP readings are measured. Caffeine and other stimulants, and smoking and exercise should have been avoided for 30 minutes prior to the BP reading. There should be no acute anxiety, stress, or pain, and there should not be bowel or bladder discomfort.

• 2.

  Describe the procedure to the patient: “I am now going to measure your blood pressure. This involves wrapping a cuff around your arm and inflating it. You will feel the pressure on your arm increase, but you shouldn’t experience any pain. Please stay silent during the test.”

• 3.

  Ask the patient to remove any clothing covering the arm and ensure that any rolled up sleeve does not excessively constrict the arm.

• 4.

  Ask the patient to bend their arm slightly with the palm turned upwards and rest it on the chair armrest or nearby table. The arm should be at heart level.

• 5.

  Select a BP cuff that encircles at least 80% of the arm to ensure accuracy. Typically two cuff sizes are required: large and regular adult ( Fig. 9.2 ). A too small cuff will result in an artificially elevated reading.

  

• 6.

  Locate the brachial artery along the inner upper arm by palpation. Wrap the cuff smoothly and snugly around the arm, centering the bladder over the brachial artery (the artery arrow on the cuff should be pointing at the artery). The lower margin should be 2.5 to 3 cm above the antecubital crease (bend of the elbow).

• 7.

  Check that the cuff fits snugly, but is not too tight or too loose. If it is difficult to insert a finger under the cuff edge, it is too tight; if you can insert more than one finger, it is too loose.

• 8.

  Set the device to take measurements at 1- or 2-minute intervals. You should verify the first measurement and then leave the patient alone while the device automatically takes the subsequent readings. Depending on the device three to six readings are taken and then averaged, usually discounting the first reading.

9.1.3

Recording

Record the patient’s position and the time and the arm used for the measurement. Record the cuff size if it was not the regular adult cuff that was used. Record the pulse rate and record the systolic and diastolic reading in mmHg.

Examples:

• 120/80 right arm seated @ 2:30 pm. Pulse 70 bpm

• 132/84, left arm, seated @ 9.30 am, large adult cuff. Pulse 72 bpm

9.1.4

Interpreting the results

The classification of hypertension, which is based on two properly measured seated BP readings on each of two or more separate office visits, is shown in Fig. 9.3 , although research suggests that ambulatory measurements better predict who should be placed on treatment. ^, Individuals who are suspected to be in the elevated classification should be referred to a general physician for health-promoting lifestyle modifications. These modifications include weight control, increase in physical activity, a reductions in salt intake and alcohol consumption, and smoking cessation. Stage 1 and 2 hypertension (i.e., systolic BP above 130mmHg and diastolic BP above 80mmHg, see Fig. 9.3 ) should be referred to a general physician for further investigation and to consider treatment with pharmacological interventions. Cardiovascular disease risk and concomitant disorders, such as diabetes, will inform the decision to treat hypertension and to what level. ^, A hypertensive emergency occurs when the systolic BP is greater than 210 mmHg and the diastolic greater than 130 mmHg. There is evidence of progressive or impending target-organ damage and the BP must be lowered immediately but carefully to prevent end-organ damage from lowering the BP too quickly. This treatment normally requires hospitalisation. A hypertensive urgency is an increase in diastolic BP to greater than 120 to 130 mmHg without end-organ damage which can be treated in office or in the emergency room with oral medications over several hours to lower the BP. This usually occurs in patients who discontinue their treatment after achieving normal BP. ^,

9.1.5

Most common errors

• 1.

  Not preparing and positioning the patient correctly. The pressure in the arm increases as the arm is lowered from the level of the heart (phlebostatic axis); conversely, raising the arm above this position lowers the pressure measurement.

• 2.

  Using the wrong cuff size: Typically two cuff sizes are required in optometric practice: large adult and regular adult. Child size cuffs are also available (see Fig. 9.2 ), but unlikely to be used in optometric practice.