Positive end expiratory pressure (PEEP). Where does hypertension come from? Checking the kidneys and treating snoring Modern research into the Casimir effect

LABORATORY WORK No. 2

Topic: “MEASURING BLOOD PRESSURE”

TARGET. Study the biophysical mechanism of creating blood pressure, as well as the biophysical properties of blood vessels. Understand the theoretical foundations of the method of indirect measurement of blood pressure. Master the N.S. method Korotkov for measuring blood pressure.

DEVICES AND ACCESSORIES. Sphygmomanometer,

phonendoscope.

STUDY PLAN

1. Pressure (definition, units of measurement).

2. Bernoulli's equation, its use in relation to blood movement.

3. Basic biophysical properties of blood vessels.

4. Changes in blood pressure along the vascular bed.

5. Hydraulic resistance of blood vessels.

6. Method for determining blood pressure using the Korotkov method.

BRIEF THEORY

Pressure P is a quantity numerically equal to the ratio of the force F acting perpendicular to the surface to the area S of this surface:

P S F

The SI unit of pressure is pascal (Pa), non-system units: millimeter of mercury (1 mm Hg = 133 Pa), centimeter of water, atmosphere, bar, etc.

The action of blood on the walls of a vessel (the ratio of the force acting perpendicularly per unit area of the vessel) is called blood pressure. There are two main cycles in the work of the heart: systole (contraction of the heart muscle) and diastole (its relaxation), therefore systolic and diastolic pressure is noted.

When the heart muscle contracts, a volume of blood equal to 6570 ml, called stroke volume, is pushed into the aorta, which is already filled with blood under appropriate pressure. The additional volume of blood entering the aorta acts on the walls of the vessel, creating systolic pressure.

The increased pressure wave is transmitted to the periphery of the vascular walls of arteries and arterioles in the form of an elastic wave. This pressure wave

called a pulse wave. The speed of its spread depends on the elasticity of the vascular walls and is equal to 6-8 m/s.

The amount of blood flowing through the cross-section of a section of the vascular system per unit time is called the volumetric blood flow velocity (l/min).

This value depends on the pressure difference at the beginning and end of the section and its resistance to blood flow.

The hydraulic resistance of blood vessels is determined by the formula

R 8, r 4

where is the viscosity of the liquid; is the length of the vessel;

r is the radius of the vessel.

If the cross-sectional area of a vessel changes, then the total hydraulic resistance is found by analogy with a series connection of resistors:

R=R1 +R2 +…Rn ,

where Rn is the hydraulic resistance of a section of the vessel with radius r and length.

If a vessel branches into n vessels with hydraulic resistance Rn, then the total resistance is found by analogy with a parallel connection of resistors:

The resistance R of a system of branched vessels will be less than the minimum of the vessel resistances.

In Fig. Figure 1 shows a graph of changes in blood pressure in the main parts of the vascular system of the systemic circulation.

Rice. 1. where P0 is atmospheric pressure.

Pressure that is excess above atmospheric pressure is considered positive. Pressure less than atmospheric pressure is negative.

According to the schedule in Fig. 1 we can conclude that the maximum pressure drop is observed in the arterioles, and in the vein there is negative pressure.

Measuring blood pressure plays an important role in the diagnosis of many diseases. Systolic and diastolic pressure in the artery can be measured directly using a needle connected to a manometer (direct or blood method). However, in medicine, the indirect (bloodless) method proposed by N.S. is widely used. Korotkov. It is as follows.

A cuff capable of being filled with air is placed around the arm between the shoulder and elbow. At first, the excess air pressure in the cuff above atmospheric pressure is 0, the cuff does not compress the soft tissues and artery. As air is pumped into the cuff, the cuff compresses the brachial artery and stops blood flow.

The air pressure inside the cuff, which consists of elastic walls, is approximately equal to the pressure in the soft tissues and arteries. This is the basic physical idea of the bloodless method of measuring pressure. By releasing air, the pressure in the cuff and soft tissues is reduced.

When the pressure becomes equal to systolic, blood will be able to break through at high speed through a very small cross-section of the artery - and the flow will be turbulent.

The characteristic tones and noises accompanying this process are listened to by the doctor. At the moment of listening to the first tones, the pressure (systolic) is recorded. By continuing to reduce the pressure in the cuff, laminar flow of blood can be restored. The murmurs stop, and at the moment they stop, the diastolic pressure is recorded. To measure blood pressure, a device is used - a sphygmomanometer, consisting of a bulb, a cuff, a pressure gauge and a phonendoscope.

QUESTIONS FOR SELF-CONTROL

1. What is pressure called?

2. In what units is pressure measured?

3. Which pressure is considered positive and which negative?

4. State Bernoulli's rule.

5. Under what conditions is laminar fluid flow observed?

6. What is the difference between turbulent flow and laminar flow? Under what conditions is turbulent fluid flow observed?

7. Write down the formula for the hydraulic resistance of blood vessels.

9. What is systolic blood pressure? What is it equal to in a healthy person at rest?

10. What is diastolic blood pressure? What does it equal in vessels?

11. What is a pulse wave?

12. In which part of the cardiovascular system does the greatest pressure drop occur? What is it due to?

13. What is the pressure in the venous vessels, large veins?

14. What device is used to measure blood pressure?

15. What components does this device consist of?

16. What causes the appearance of sounds when determining blood pressure?

17. At what point in time does the device reading correspond to the systolic blood pressure? At what point is diastolic blood pressure?

WORK PLAN

Subsequence		Method of completing the task.
actions
1. Check		The created pressure should not change within 3
tightness.
	Define	1. Take measurements 3 times, record the readings in
systolic		table (see below).
diastolic	pressure	2. Place a cuff on the bare shoulder, find
right and left hands		on the elbow bend a pulsating artery and
method N.S. Korotkova		install over it (without pressing hard)
		phonendoscope. Apply pressure to the cuff and then
		by slightly opening the screw valve, air is released, which
		leads to a gradual decrease in pressure in the cuff.
		At a certain pressure the first weak sounds are heard
		short-term tones. At this moment it is fixed
		systolic blood pressure. With further
		As the pressure in the cuff decreases, the sounds become louder,

		finally, they sharply muffle or disappear. Pressure
		the air in the cuff at this moment is taken to be
		diastolic.
		3. Time during which the measurement is made
		pressure according to N.S. Korotkov, should not last more than 1

	Definition	1. Do 10 squats.

systolic					2. Measure the pressure on your left arm.
diastolic		pressure			3. Enter the readings into the table.
blood using the Korotkoff method
after physical activity.
		Definition			Repeat measurements after 1, 2 and 3 minutes. after
systolic				physical activity.
diastolic		pressure			1. Measure the pressure on your left arm.
blood at rest.					2. Enter the readings into the table.

	Normal (mm Hg)					After load	After rest

	Syst. pressure		Diast. pressure
	Syst. pressure		Diast. pressure






		Decor			1. Compare the results obtained with normal
laboratory work.				blood pressure.
					2. Draw a conclusion about the state of the cardiovascular system

Analogy

A phenomenon similar to the Casimir effect was observed back in the 18th century by French sailors. When two ships, swaying from side to side in conditions of strong waves but weak wind, were at a distance of approximately 40 meters or less, then as a result of the interference of waves in the space between the ships, the excitement ceased. The calm sea between the ships created less pressure than the rough sea on the outer sides of the ships. As a result, a force arose that tended to push the ships sideways. As a countermeasure, sailing manuals from the early 1800s recommended that both ships send a lifeboat with 10 to 20 sailors to push the ships apart. Due to this effect (among others), garbage islands are formed in the ocean today.

History of discovery

Hendrik Casimir worked in Philips Research Laboratories in the Netherlands, studying colloidal solutions - viscous substances containing micron-sized particles. One of his colleagues, Theo Overbeck ( Theo Overbeek), discovered that the behavior of colloidal solutions was not entirely consistent with existing theory, and asked Casimir to investigate this problem. Casimir soon came to the conclusion that deviations from the behavior predicted by the theory could be explained by taking into account the influence of vacuum fluctuations on intermolecular interactions. This prompted him to ask what effect vacuum fluctuations could have on two parallel mirror surfaces, and led to his famous prediction about the existence of an attractive force between the latter.

Experimental detection

Modern research into the Casimir effect

Casimir effect for dielectrics
Casimir effect at non-zero temperature
connection between the Casimir effect and other effects or branches of physics (relationship with geometric optics, decoherence, polymer physics)
dynamic Casimir effect
taking into account the Casimir effect when developing highly sensitive MEMS devices.

Application

By 2018, a Russian-German group of physicists (V.M. Mostepanenko, G.L. Klimchitskaya, V.M. Petrov and a group from Darmstadt led by Theo Tschudi) developed a theoretical and experimental scheme for a miniature quantum optical chopper for laser beams based on the Casimir effect, in which the Casimir force is balanced by light pressure.

In culture

The Casimir effect is described in some detail in Arthur C. Clarke's science fiction book The Light of Another Day, where it is used to create two paired wormholes in space-time and transmit information through them.

Notes

Barash Yu. S., Ginzburg V. L. Electromagnetic fluctuations in matter and molecular (van der Waals) forces between bodies // UFN, vol. 116, p. 5-40 (1975)
Casimir H.B.G. On the attraction between two perfectly conducting plates (English) // Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen: journal. - 1948. - Vol. 51. - P. 793-795.
Sparnaay, M.J. Attractive Forces between Flat Plates // Nature. - 1957. - Vol. 180, no. 4581. - P. 334-335. - DOI:10.1038/180334b0. - Bibcode: 1957Natur.180..334S.
Sparnaay, M. Measurements of attractive forces between flat plates (English) // Physica: journal. - 1958. - Vol. 24, no. 6-10. - P. 751-764. -

Positive end expiratory pressure (PEEP) and continuous positive airway pressure (CPAP).
The PEEP and CPAP methods have long been firmly established in the practice of mechanical ventilation. Without them, it is impossible to imagine providing effective respiratory support in seriously ill patients (13, 15, 54, 109, 151).

Most doctors, without even thinking, automatically turn on the PEEP regulator on the breathing apparatus from the very beginning of mechanical ventilation. However, we must remember that PEEP is not only a doctor’s powerful weapon in the fight against severe pulmonary pathology. Thoughtless, chaotic, “by eye” use (or abrupt cancellation) of PEEP can lead to serious complications and deterioration of the patient’s condition. A specialist performing mechanical ventilation is simply obliged to know the essence of PEEP, its positive and negative effects, indications and contraindications for its use. According to modern international terminology, English abbreviations are generally accepted: for PEEP - PEEP (positive end-expiratory pressure), for CPAP - CPAP (continuous positive airway pressure). The essence of PEEP is that at the end of expiration (after forced or assisted inspiration), the pressure in the airways does not decrease to zero, but
remains above atmospheric pressure by a certain amount determined by the doctor.
PEEP is achieved by electronically controlled expiratory valve mechanisms. Without interfering with the onset of exhalation, subsequently at a certain stage of exhalation these mechanisms close the valve to a certain extent and thereby create additional pressure at the end of exhalation. It is important that the PEEP valve mechanism does not create1 additional expiratory resistance during the main phase of expiration, otherwise Pmean increases with corresponding undesirable effects.
The CPAP function is designed primarily to maintain constant positive airway pressure while the patient breathes spontaneously from the circuit. The CPAP mechanism is more complex and is ensured not only by closing the expiratory valve, but also by automatically adjusting the level of constant flow of the respiratory mixture in the breathing circuit. During exhalation, this flow is very small (equal to the basic expiratory flow), the CPAP value is equal to PEEP and is maintained mainly by the expiratory valve. On the other hand, to maintain a given level of a certain positive pressure during spontaneous inspiration (especially at the beginning). the device supplies a sufficiently powerful inspiratory flow into the circuit, corresponding to the inspiratory needs of the patient. Modern fans automatically regulate the flow level, maintaining the set CPAP - the “Demand Flow” principle. When the patient spontaneously attempts to inhale, the pressure in the circuit decreases moderately, but remains positive due to the supply of inspiratory flow from the device. During exhalation, the pressure in the airways initially increases moderately (after all, it is necessary to overcome the resistance of the breathing circuit and the expiratory valve), then it becomes equal to PEEP. Therefore, the pressure curve with CPAP is sinusoidal. A significant increase in airway pressure does not occur in any phase of the respiratory cycle, since the expiratory valve remains at least partially open during inhalation and exhalation.

negative pressure- Gas pressure is less than ambient pressure. [GOST R 52423 2005] Inhalation topics. anesthesia, art. ventilator lungs EN negative pressure DE negativer Druck FR pression negativepression subatmosphérique …

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