Pressure In Drops, Bubbles, And Capillary Rise

Pressure in Drops

Let’s consider a liquid drop which is having a pressure P1; on comparing its pressure with the atmospheric pressure Patm, we found that P1 > Patm.

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This happens due to surface tension.

The surface of the body behaves as if covered by a stretched membrane having tension in all directions parallel to the surface that the pressure of liquid increases within a bubble. 

Consider the free-body diagram of a liquid drop, as shown in Fig. 

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If the force due to surface tension at the circumference is balanced by the pressure forces inside the drop, then:

                                    2πRσ = PπR2

We get:                         ΔP = 2σ/R  

Here, ΔPis the pressure difference between inside the drop and outside.

What is Blood Pressure?

Our heart pumps blood, oxygen, and nutrients through the arteries in our body.

Blood pressure is the measure of the force exerted by the circulating blood against our arterial walls.

There Are Two Readings Which Measure Blood Pressure, Which Are

1. Systolic blood pressure

2. Diastolic blood pressure

Systolic blood pressure is the higher number. It measures the force of blood being pumped around our body when our heart contracts.

Diastolic blood pressure is the lower number. It measures when the heart relaxes between beats.

The normal bp value is 120 mm Hg/80 mmHg.

Where mmHg stands for millimeters of mercury.

High BP 

High blood pressure is always higher than the normal range of the bp. 

It is also known as hypertension.

Its value is 140 mmHg / 90 mmHg or higher. 

BP Drop

The value of bp, 90 mmHg/60 mmHg or lower is considered to be lower bp or bp drop. 

Bp drop is also known as hypotension.

A Sudden Drop in Blood Pressure

A sudden drop in blood pressure happens when your organs don't get the proper amount of blood and oxygen.

According to the American Heart Association, we don't have fixed readings for specifying low bp.

However, medical experts say that our bp is low when systolic bp is less than 90 mmHg diastolic bp is less than 60.

So, if bp measures 84 mmHg/57 mmHg; it means our bp is low.

The Consequences of a Sudden Drop in BP Are

1. Dizziness or light-headedness

This happens when our brain doesn’t get enough supply of blood.

     2. Fainting

Insufficient supply of blood to the brain can cause us to lose consciousness.

    3. Blurred vision

    4. Lack of concentration

    5. Unable to focus on anything

Bp drop diminishes attention.

   6. Memory nausea

We may feel discomfort, uneasiness, or an urge to vomit, and 

  7. Rapid breathing

   8. Breath becomes shallow and breathing rate per minute increases. 

The heart compensates for the lack of blood by pumping faster.

   9. Fatigue

Tired or not wanting to do any physical activity.

BP Drops During Exercise

Blood pressure is measured by multiplying cardiac output and the total peripheral resistance.

Bp can change in response to an activity, body size, and diet.

It may happen due to health problems like obesity, or because of the blood vessel disease.

Bp is internally managed by baroreceptors, enlarged arteries that can detect changes in the blood pressure, and alert our nervous system to release hormones that constrict or dilate the vessels as per the requirement.

According to the Hemodynamics of Hypertension report, the type and duration of the exercise, how much water we lose through sweat, and in-case we exercise in the heat are factors that can usher to a drop in blood pressure.

However, if our bp persistently drops when we go from lying down to sitting up or from sitting to standing, we may have an orthostatic drop in blood pressure or postural bp drop.

Postural Hypotension Drop

The age-factor is the cause of postural hypotension.

Let’s assume an old person seated or lying down just like a bottle resting on the table as shown below:

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The blood is uniformly distributed in the body. 

Now, if he suddenly stands up, due to the gravity effect, the blood tends to pool in the lower part of his body.

Just like we drink some amount of water, the remaining quantity rests at the lower part of the bottle.

Now, if he certainly stands up, the blood pools in the lower part (because of gravitational pooling), his upper part may not get enough blood. 

This, in turn, may lead to a deficiency in the supply of blood and oxygen to cerebral ischemia, resulting in vertigo dizziness.

Therefore, to compensate postural hypotension, his heart pumps at a higher rate to bring the bp at a normal level.

Postural Drop in Blood Pressure

While measuring our bp, we could see a drop from 120/80 to 100/70 within minutes of changing your position.

Do You Know?

According to Langdon’s position, if we suddenly stand or sit, 600 to 700 ml, our blood is reduced in the upper part of the body because of pulling in the lower part of the body.