Short-term blood pressure? Its variability phenotype, changes & risks.
Short-term blood pressure? Its variability phenotype, changes & risks.
Arterial blood pressure indicates the pressure by large arteries in the systemic circulation system. Arterial pressure is regulated by several interrelated systems & each of them performs a specific function. This is known as the blood pressure regulating system.
These mechanisms can be divided into 3 groups-
- Rapidly acting/short-term pressure control mechanisms
- Intermediate-acting pressure control mechanisms.
- Long term mechanisms.
Blood pressure can be varied for different reasons. There are some common factors that influence arterial blood pressure & controls the mechanism. Changes in average bp value can affect the whole regulation system & leads to further difficulties. It’s also considered as a golden standard in clinical Sectors for screening & diagnosis purposes. Successful management of hypertension cannot be achieved without the help of exact BP readings. phenotypes of short-term BP variability is especially needed in the primary-care setting. In this review, we’ll explain the phenotypes and variability of short-term blood pressure. Also, let you know how it affects our body mentioning the changes & risks accordingly.
Different types of Blood pressure variability:
Rapidly acting/short term pressure control mechanism: the rapidly acting control mechanisms are almost entirely acute nervous reflexes or other nervous responses. The three mechanisms that show responses within seconds. They are-
- The baroreceptor feedback mechanism
- The central nervous system ischemic mechanism
- The chemoreceptor mechanism
Intermediate-acting pressure control mechanism: intermediate pressure control mechanism responds after few minutes following acute arterial pressure change. Three of these are:
- The renin-angiotensin vasoconstrictor mechanism. Stress-relaxation of the vasculature. Capillary fluid shift mechanism ( shift of fluid through the tissue capillary walls in and out of the circulation to readjust the blood volume as needed.
Long term mechanisms for arterial pressure regulation:
- Renal-body fluid pressure control mechanism. renin-angiotensin-aldosterone mechanism
Factors that influence arterial blood pressure:
There are different factors that regulate & control arterial blood pressure. Some of them are discussed below:
. pumping action of heart:
effectual contraction of the heart is the main factor for controlling the cardiac output, blood pressure & blood flow within the vessels.
. cardiac output:
BP = cardiac output × total peripheral resistance
So, if total peripheral resistance is constant, increased total peripheral resistance causes increased blood pressure & vice versa.
.peripheral resistance :
BP = cardiac output × total peripheral resistance
So, if cardiac output is constant, increased total peripheral resistance causes increased blood pressure & vice versa.
. The elasticity of arterial walls:
In normal diastolic pressure, arterial walls are stretched but due to the presence of elastic tissues in the walls, they tend to recoil. Due to the elasticity of arterial walls, the blood pressure the blood flow is pulsatile in the arteries. In the capillaries & venules, the flow is continuous. In old age, the expansion of arterial walls becomes limited due to sclerotic changes & the Blood pressure rises.
. Blood volume:
Increased blood volume will raise both systolic & diastolic pressure due to the increased quantity of blood in the arterial system & greater stretching of the arterial walls.
The viscosity of blood:
Increased viscosity causes increased total peripheral resistance which in turn causes the rise of diastolic blood pressure.
Understanding short term blood pressure variability :
Short-term BPV indicates the changes in blood pressure that occur within a short time. Maybe within a few seconds/a days. It is mainly controlled by autonomic reflexes and changes in the elastic properties of arteries. Studies have shown that short term BPV is clinically important in the medical sectors. It can control cardiovascular events as well as target-organ damage and also have prognostic implications.
Short term blood pressure variability can be measured in 2 way:
. ABPM ( measures bp every 15-30 minutes)
. HBPM ( measures bp while sleeping)
The short term BPV can be monitored both during working hours and sleeping hours. As a result, we can detect the bp changes over 24 hours. Also provides information about –
*morning bp surge & *nocturnal dipping. These two are the important phenotypes of short-term blood pressure variability.
Morning blood pressure surge – morning hypertension:
Morning blood pressure surge indicates maintaining adequate blood supply in a condition of increased activity which is an essential physiological phenomenon. Blood pressure tends to surge higher in the morning which is a normal psychological process. But in some hypertensive patients, early/ exaggerated morning bp surge has been observed. It’s known as morning hypertension.
Morning hypertension that can be detected by HBPM. The causes are-
. extreme morning bp surge.
prolonged nocturnal hypertension that extends into the morning
Variation of Bp values for Morning hypertension diagnosis –
. By using OBPM – ≥140/90 mmHg.
.By using out-of-office BP monitoring- ≥135/85 mmHg.
. If, having a morning-evening BP difference is >15 mmHg
Or, the morning–nocturnal BP difference is >35–55 mmHg.
It’s recommended to monitor the values through HBPM in the morning and the evening which is the most used method. It can be also measured within 1 hour of waking, during sleep if possible, and also after urination. Two or three readings for five to seven days in the morning is enough to measure it properly. But in some cases, if the patient is going through any medications or taking meals lately then evening HBP should be measured just before sleep.
Nocturnal dipping – nocturnal hypertension:
Due to a phenomenon in normotensive patients, blood pressure generally dips about 10-20%. It’s known as nocturnal dipping. An average nocturnal BP value is ≥ 120/70 mmHg.
Causes for the absence of dipping:
Obesity, orthostatic hypotension, chronic kidney diseases, diabetics, sleep disturbance, old age, etc.
Based on the extent of fall in nighttime blood pressure it can be categorized into four different groups.
- Dippers (BP falls in the range of 10%–20%)
- Extreme- dippers (dip >20%)
- Non- dippers ( exhibit <10% dip)
. Reverse- dippers (increase in nocturnal BP, instead of a fall)
Nocturnal bp represents the patient’s actual blood pressure more closely. So it’s very essential to control it properly. It’s also strong evidence of indicating circadian significance & variety of both normotensive & hypertensive patients. Associated with morning bp surge it can increase cardiovascular events & give a rise to other phenotypes of short-term blood pressure.
Short-term regulation of blood pressure:
The rapidly acting pressure control mechanisms are acute nervous reflexes or other nervous responses. Following three mechanisms responses in seconds. The steps are given below-
The baroreceptor feedback mechanism:
>When the arterial pressure increases, the baroreceptor present in the aortic arch and carotid sinus gets stimulation. This signal goes to the medulla via vagus & glossopharyngeal nerves than to the nucleus of tractus solitaries. As a result, inhibition of the vasoconstrictor area occurs and the vasomotor tone decreases. The blood pressure normalizes due to dilatation of the blood vessels. On the other hand, the stimulation of the vasodilator area increase in the vagal tone, and the blood pressure normalizes by the reduction of cardiac output.
The central nervous system ischemic mechanism:
>when the blood pressure reduces it causes cerebral ischemia. As a result, blood flow to the vasomotor center of the medulla decreases & the concentration of Carbon dioxide increases. Stimulation of the vasoconstrictor area results in vasoconstriction which rises the arterial Pressure.
The chemoreceptor mechanism:
>when the arterial blood pressure is below 80 mmHg the blood flow to the chemoreceptors present in the carotid sinus & aortic body decreases. A decrease in Carbon dioxide stimulates the chemoreceptors. This stimulation goes to the vasomotor center of the medulla via –
- Glossopharyngeal (from carotid sinus)
- Vagus ( from the aortic body)
Then the arterial blood pressure rises due to vasoconstriction. Thus how Short- term blood pressure is controlled.
Blood pressure monitoring methods:
ABPM ( Ambulatory blood pressure monitoring) & HBPM ( Home blood pressure monitoring) :
The main difference between ABPM & HBPM is that in the ABPM method blood pressure is monitored during working periods & within a short time (24 hours). On the other hand, HBPM is measured in the resting periods of the patient for a long time. It can be monitored well when the patient is sleeping, but most of the HBPM devices cannot obtain blood pressure readings during sleep. So it’s been measured in the resting stage. HBPM is not recommended as often as ABPM in measuring short-term blood pressure though it’s widely available & easy to work with. HBPM is used mainly for monitoring long-term blood pressure.
Procedures & precautions for measuring BP:
The ambulatory blood pressure monitoring method ( ABPM) is used for measuring 24- hour blood pressure.
- A blood pressure cuff on the upper arm of the patient is adjusted which is connected to a monitor.
- The patient must be calm and seated with back support. Legs should be on the floor uncrossed.
- The patient should relax for 1-5 minutes before taking the measurement.
- The arm should be supported well at the heart level.
- Measurements should be taken before workouts & meals, and after defecation.
- Beverages, drugs, cigarettes, etc. are prohibited before & during the procedure.
The monitor records the blood pressure several times during working hours & also during sleep. The patient can feel uncomfortable during the procedure while sleeping or working. The cuff may feel congested & rashes are common which disappears after a short time.
Risks due to short-term BP changes:
Uncontrolled high blood pressure & hypertension are the most common reason behind immature death nowadays. Hypertension is a sustained elevation of systemic arterial pressure. At any age, sustained elevation of systolic pressure 140 mmHg and diastolic pressure 90 mmHg or more ( whereas normotensive pressure is 120/80 mmHg) should be considered as hypertension. Rather than controlling bp level, bp surges are much effective in the management of hypertension. Hypertension is associated with an increased rate of coronary diseases. But controlling the blood pressure effectively can reduce the causes of stroke and death. Short-term high blood pressure damages the blood vessels which may rupture in course of time. It also clots the blood to the vessels that go to the brain & potentially lead to brain stroke. If the bp is uncontrolled & left untreated, it can lead to further coronary diseases, brain stroke, kidney failure, metabolic diseases & so on. A healthy lifestyle & daily check-up can help you to slow down its effects for longer life. Proper diet, workouts, quitting caffeine, smoking & alcohol, cutting of sugar &sodium, a stress-free & regular medications are mostly needed to control the entire mechanism. It’s preventable if it’s possible to take steps earlier. Otherwise, it can lead you to death as well.
It’s very essential to maintain healthy blood pressure because a simple variation of the regulation can be deadly. Short-term blood pressure variability consists of some necessary phenotypes as nocturnal dipping & morning bp surge that associates to defect further health issues as well. ABPM/HBPM method is highly recommended to identify the changes during the measurements. Both patient & doctor should be tolerant & stress-free during the procedure. For these, Proper clinical management is recommended.
>what time of day blood pressure is lowest?
Blood pressure is lowest in the nighttime while you’re sleeping.
It gradually rises during day time. In the mid-afternoon, it’s the highest. Then it drops again slowly.
>can hormone imbalance cause high blood pressure?
If the secretion of endocrinal glands is too much or not enough it can cause high blood pressure. Such as- endocrine hypertension. Most of the imbalance is caused by the secretion of the pituitary or adrenal gland.
>what hormones affect bp?
Angiotensin & aldosterone hormones which are Produced by renin controls the width of the lumen of the arteries thus how controls the blood pressure.
>how does baroreceptor affects bp?
Baroreceptors are nerve endings in the walls of blood vessels & the heart. The stimulation baroreceptor increases the secretion of norepinephrine on the heart & blood vessels & the blood pressure increases.
>what can bring blood pressure down immediately?
A healthy change in daily lifestyle is the key to maintain blood pressure. Staying active all day, workouts, meditations can help you to lead a stress-free life. Following a healthy diet & avoiding smoking, alcohol & beverages can lower blood pressure in a short time.
Writer: Aniqa Jahin
BDS (Bachelor Of Dental Surgery)
Mymensingh Medical College
Edited By: AR