Compliance of Cardio-Respiratory Systems Flashcards Preview

HMS Homeostasis I > Compliance of Cardio-Respiratory Systems > Flashcards

Flashcards in Compliance of Cardio-Respiratory Systems Deck (48)
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1
Q

Transmural Pressure

A

Pressure inside - pressure outside

So, a PTM > 0 means that a fluid will flow out or expand the vessel

and a PTM < 0 means that a fluid will flow in or compress the vessel

2
Q

As an elastic vessel stretches, . . .

A

. . . the recoil force increases and opposes the pressure inside of the vessel.

3
Q

Compliance

A

ΔP / ΔV

A characteristic of a closed, elastic structure that relates the change in volume of the structure to the change in pressure within the structure, i.e., the stiffness of the system.

4
Q

Transmural pressure determines the final volume of a vessel given its ___.

A

Transmural pressure determines the final volume of a vessel given its compliance.

5
Q

The stiffer or more rigid a structure, the more it resists. . .

A

being moved from its resting position

6
Q

The pressure inside of a vessel is equal to. . .

A

. . . the sum of the pressure outside the vessel (Po) and the recoil pressure of the vessel (Pel).

7
Q

When we discuss the alveolus in the lung, the external pressure is the. . .

A

. . . pressure of the pleural space.

8
Q

When we discuss the alveolus in the lung, the elastic pressure is the. . .

A

. . . pressure generated by the elastic recoil of the lung tissue that has expanded.

9
Q

Left ventricles of different compliance on a LV pressure / LV volume curve

A

The way this graph is drawn, the slope of the curve is ΔP/ΔV, which is 1 / compliance

10
Q

Potential causes of reduced ventricular compliance

A
  • Change in the structure of the ventricular tissue
  • Energy required to pump calcium out of the cells is impaired
11
Q

Reduced ventricular compliance leads to . . .

A

. . . higher pressures in the ventricle (and consequently in the pulmonary veins and capillaries, which empty into the ventricle) for any given filling volume, and reduced filling of the ventricle, which can compromise the stroke volume

This higher pressure in the ventricle during diastole may cause fluid to leak into the lungs

12
Q

since relaxation of the ventricle is energy dependent, . . .

A

since relaxation of the ventricle is energy dependent, conditions that reduce oxygen supply to the ventricle can be associated with reduced compliance

13
Q

Structural states that may reduce ventricular compliance

A
  • Fibrosis
  • Endocarditis
  • Bacterial plaques
  • Amyloid deposits
  • Hypertrophy of cardac muscle
14
Q

In respiratory physiology, forces are typically expressed as

A

In respiratory physiology, forces are typically expressed as the pressure generated by the height of column of water (in centimeters H2O)

15
Q

In cardiovascular physiology, forces are typically expressed as . . .

A

In cardiovascular physiology, forces are typically expressed as the pressure generated by the height of a column of mercury (in mm of Hg).

16
Q

Mercury is approximately ___ times as dense as water

A

Mercury is approximately 13 times as dense as water

17
Q

The volume of our respiratory system reflects the interaction between the actions of the ___ and ___.

A

The volume of our respiratory system reflects the interaction between the actions of the chest wall and lungs (as linked by the pleural space which separates them).

Muscles generated a negative pressure in the chest which acts against the elastic recoil of the lung tissue.

18
Q

Resting position

A

The volume occurring when there are no external forces acting on the structure. The resting position of the lungs and chest wall can only be determined in vitro

19
Q

The resting position of the chest wall alone is about ___

A

The resting position of the chest wall alone is about 75-80% of vital capacity

20
Q

Vital capacity

A

Difference between maximal inspiration and maximal expiration

21
Q

The resting position of the lung is ___

A

The resting position of the lung is below residual volume

22
Q

The pressure-volume relationships of the isolated lung, isolated chest wall and the respiratory system

A
23
Q

At the resting volume of the respiratory system, i.e., the point at which the transmural pressure is zero, . . .

A

At the resting volume of the respiratory system, i.e., the point at which the transmural pressure is zero, the tendency of the lung to collapse is offset by the tendency of the chest wall to spring out

24
Q

The volume of the respiratory system at which the transmural pressure is zero

A

functional residual capacity (FRC)

At volumes above FRC, the balance of forces is such that the respiratory system wants to get smaller; at volumes below FRC, the balance of forces pushes the system toward a higher volume

25
Q

The longer a muscle (up to certain limits) at the time that it is stimulated by a given neurological impulse, . . .

A

The longer a muscle (up to certain limits) at the time that it is stimulated by a given neurological impulse, the greater the tension generated

Same logic as the heart’s stretch/contractility relationship

26
Q

At low thoracic volumes, the inspiratory muscles are ___

At high thoracic volumes, the inspiratory muscles are ___

A

At low thoracic volumes, the inspiratory muscles are relatively long and thus generate a high tension when stimulated by a neurological impulse (end of expiration)

At high thoracic volumes, the inspiratory muscles are shortened and are less effective at generating tension for a given neural stimulus (end of inspiration)

27
Q

Gas trapping

A

As lung volume becomes smaller, some airways narrow (and resistance increases) to the point that expiratory flow is extremely low. Since you cannot exhale indefinitely, you may not be able to empty all of the air out of the lung that you would expect if end-expiratory volume were always determined merely by the balance of forces between lung and chest wall. Thus, some gas is effectively trapped in this base region of the lung,

28
Q

End expiratory lung volume

A

Generic term for the volume of the lung at the end of exhalation.

In healthy, resting individuals, EELV is equal to FRC. But, exercising individuals or individuals with a lung condition (emphysema, obesity, etc), where volume is not being determined solely by the elastic properties of the lungs and chest wall, they may be different.

29
Q

Pressure by Vital capacity curves for various lung conditions

A
30
Q

Total Lung Capacity

A

Volume of gas in the lung at maximal inspiration

Determinants: recoil of the chest wall, recoil of the lung, stiffness of the lung and chest wall, inspiratory muscle strength.

Making the respiratory system bigger – force generated by the inspiratory muscles

Making the respiratory system smaller – recoil force of the chest wall; recoil force of the lungs

31
Q

If you are using your expiratory muscles, the ___ and the ___ will not be the same.

A

If you are using your expiratory muscles, the EELV and the FRC will not be the same.

32
Q

Residual Volume

A

volume of gas in the lung at the end of a maximal expiratory maneuver

Determinants: tendency of the chest wall to spring outward, elastic recoil of the lung inward, airway narrowing (which prevents some of the gas in the small airways from exiting the lung), expiratory muscle strength to overcome the tendency of the chest wall to spring outward at low lung volumes.

33
Q

In individuals over age ___, dynamic considerations come into play in determining residual volume

A

In individuals over age 40, dynamic considerations come into play in determining residual volume

34
Q

Basic spirogram

A
35
Q

Surface tension is produced at. . .

A

an air-liquid interface

36
Q

Liquids with more surface tension / cohesion tend to. . .

A

. . . arrange in a shape that minimizes their surface area, resulting in a vector force inwards that creates a pressure according to Laplace’s Law.

37
Q

Laplace’s law for surface tension

A

P = 2T / r

38
Q

Alveolar size and position

A

Alveoli in the bottom of the lung are smaller than those at the top, due to their compression by the weight of the lung tissue.

39
Q

The alveolar surface tension problem

A

By Laplace’s law, left to their own devices, the alveoli would all collapse into one larger alveolus. In order to prevent this, and do reduce the surface tension of each alveolus proportional to its radius (to keep pressure constant, P = 2 T / r), type I pneumocytes produce a detergent, surfactant. Surfactant reduces the cohesion of the liquid, thus reducing its tension. As the radius of the alveoli increase, the density of the surfactant becomes greater.

40
Q

Major causes of changed lung compliance

A
  • Change in elastic forces
  • Change in surface tension
41
Q

Endless flow through an infinitely flexible tube

A
42
Q

Why might a patient with high thoracic pressure have a low blood pressure?

A

Because the heart cannot expand, meaning that its preload will be low, and therefore it is far to the left on a Starling curve.

43
Q

Under conditions of flow limitation, ___ is increased.

A

Under conditions of flow limitation, residual volume is increased.

44
Q

In severely obese patients, residual volume is. . .

A

. . . normal. Weirdly. It is normal because of two opposing pathologies.

  1. From a fluid statics perspective, having an increased force from the chest wall should greatly reduce its ability to recoil outward, reducing the residual volume.
  2. From a fluid dynamics perspective, increased chest wall weight translates to increased pleural pressure and thus a negative transmural pressure, causing heightened airway resistance to the point of decreased flow and exhalatory volume, increasing residual volume.

There is still increased work of breathing felt by the patient, because they must overcome a pressure barrier in order to breathe. But once they overcome that barrier, the compliance curve is the same.

45
Q

Mr. Jones is diagnosed with Amyloidosis in which the heart muscle is infiltrated with an abnormal material that reduces the compliance of the heart. You predict his blood pressure will. . .

A

increase / be higher than normal

It now takes a higher pressure to fill the heart to the same volume

46
Q

Ms. Smith is a long-time smoker, which has caused her to develop emphysema, which decreases the elastic recoil of the lung tissue. You predict that her FRC will . . .

A

increase / be higher than normal

The functional residual capacity is determined by the balance of forces between lung recoil inward, chest recoil inward, and the inspiratory muscles pulling the chest wall outward. With reduced elastic recoil of the lungs, the balance of forces is shifted such that lung volume is greater at TLC.

47
Q

Systolic vs Diastolic Failure

A
48
Q

Preload and Afterload on cardiac PV cycle

A