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Medicine year 1 semester 2 > Case 6- breathing > Flashcards

Case 6- breathing Flashcards

1
Q

Muscles of inspiration- principal (quiet breathing)

A

External intercostals
Interchondral part of internal intercostals
Diaphragm

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2
Q

Muscles of inspiration- forced breathing (accessory)

A

Sternocleidomastoid
Scalenes
Serratus anterior
Pectoral muscles

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3
Q

Muscles of expiration- Quiet breathing

A

Passive action from the relaxation of the diaphragm, the elastic recoil of the lungs and the weight of the thoracic cage

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4
Q

Muscles of expiration- forced breathing (accessory)

A

Internal intercostals except for the interchondral part
Thoracic wall muscles
Abdominal muscles

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5
Q

The external intercostals effect on breathing

A

They pull the ribs up when contracting, this increases the volume of the pleural cavity. Occurs in both quiet and forced inhalation

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6
Q

The internal intercostal muscles effect on breathing

A

When they contract they depress the ribs and decrease the transverse and anterior volume of the pleural cavity. Occurs in both quiet and forced expiration

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7
Q

How the abdominal walls affects breathing

A

The muscles compress the abdominal contents to increase the abdominal pressure and push up on the diaphragm, reducing the volume of the thoracic cavity. This only happens when they contract. This occurs in expiration

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8
Q

How the chest expands

A

Chest wall expansion is via the pump handle and bucket handle movement, the Sternum moves in a superior and anterior direction. The lateral shaft of ribs elevate. This causes the volume of the lungs to increase and the pressure drops below external atmospheric pressure. The air moves from high to low pressure and enter the lungs

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9
Q

How does air leave the lungs

A

In expiration the lungs undergo elastic recoil and reduce in volume, this increases pressure inside the lungs to above external atmospheric pressure and air leaves the lungs

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10
Q

The 4 steps in physiological respiration

A
  1. Pulmonary ventilation, moving gas in and out of the lungs.
  2. Gaseous exchange: gases in the alveoli exchange with dissolved gases in the pulmonary capillaries blood. O2 is taken up and CO2 is expelled.
  3. Gas transport: O2 is transported in the blood to tissues, CO2 is transported from the tissues to the lungs.
  4. Gaseous exchange occurs between tissues and the blood
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11
Q

Movement of diaphragm and sternum in respiration

A

During inspiration the sternum increases the vertical dimensions of the thorax and lifts the ribs upwards and outwards increasing the lateral dimensions of the thorax. The diaphragm also contracts and moves downwards increasing the volume of the chest cavity. When the diaphragm descends the central tendon becomes fixed on the abdominal viscera

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12
Q

How much air enters the lungs in inspiration

A

During quiet breathing the diaphragm moves down 1.5cm so 200-300ml of air is sucked in. During forced breathing it can be up to 7cm.

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13
Q

External intercostals role in respiration

A

Best developed in the lateral and posterior regions of the thorax. When they contract they tend to lift the ribs upwards and forwards therefore expanding the diameter of the thorax. They are used in inspiration

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14
Q

Internal intercostals role in respiration

A

Best developed in lateral and parasternal region. Fibres in this muscle layer slope backwards, downwards and between adjacent ribs. When they contract they pull the ribs downwards and inwards and are muscles of expiration.

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15
Q

Forced breathing

A

During forced breathing expiratory muscles are required. Major muscles of forced expiration include anterior abdominal muscles as when they contract they increase the intra-abdominal pressure which forces the diaphragm up into the thoracic cavity reducing the volume of the lungs.

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16
Q

Physiological defenition of respiration

A
  • Pulmonary ventilation
  • Involves gas exchange in the alveoli
  • Transport of oxygenated blood from the lungs to the tissues
  • Gas exchange at the tissues
  • Transport of deoxygenated blood and carbon dioxide from the tissues to the lungs
  • Pulmonary ventilation
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17
Q

Biochemistry definition of respiration ((cellular respiration)

A
  • Utilisation of oxygen delivered to the tissues
  • Cellular metabolic processes
  • Production of ATP (energy) by catabolic reactions
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18
Q

Intrapleural pressure

A

The pressure in the pleural space between the pleural membranes. This is determined by the pressure exerted by the chest wall and the elastic recoil of the lungs. It’s measured relative to atmospheric pressure

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19
Q

The intrapleural pressure in quiet breathing

A

Negative

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20
Q

Why is the intrapleural pressure negative

A

The elastic recoil of the chest wall is trying to push the chest wall outwards, the elastic recoil of the lungs is trying to pull them inwards. Because the lungs and chest want to move in opposite directions a negative pressure is created in the space between them

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21
Q

The intrapleural pressure difference in both expiration and inspiration

A

0.4kPa in both the apex and the base

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22
Q

The intrapleural pressure in forced breathing

A

The chest wall compresses the lungs creating a more positive pressure, the intrapleural pressure then increases

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23
Q

How to directly measure intrapleural pressure

A

You inject a bubble between the pleural layers, you measure the pressure in the bubble using a manometer. It carries a degree of risk

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24
Q

How to indirectly measure intrapleural pressure

A

You measure intra-oesophageal pressure by inserting a balloon catheter in an upright position. It’s nicer for the patient but only approximates intra-pleural pressure

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25
Q

How is the intrapleural pressure gradient generated

A

Due to the gravity and weight of the lung tissue pulling the lung tissue from the apex to the base

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26
Q

Intrapleural pressure in the apex

A

The alveoli are stretched by the weight of the lung tissue below, making them more open. The stretching gives them a greater degree of elastic recoil. The alveoli are pulling the lung from the chest wall, so they want to ping back in place. The intrapleural pressure is more negative

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27
Q

Intrapleural pressure in the base

A

There is a more positive intrapleural pressure in the base of the lungs because the lung tissue is being puled down compressing the intrapleural space.

28
Q

Ventilation in the apex

A

Bigger alveoli so more elasticity surrounding it so more force has to be overcome.

29
Q

What happens to the intrapleural pressure when you breathe in

A

It becomes more negative

30
Q

Transpulmonary pressure

A

The pressure inside the alveoli take away the intrapleural pressure

31
Q

The effect Pulmonary fibrosis has on breathing

A

It’s a restrictive disease causing a low volume of air in the lungs. The alveoli are less stretched so there is less elastic recoil so the intrapleural pressure is less negative and there is less of a pressure gradient for the gas to move down

32
Q

The effect Pulmonary fibrosis has on breathing

A

It’s a restrictive disease causing a low volume of air in the lungs. The alveoli are less stretched so there is less elastic recoil so the intrapleural pressure is positive. Near the bottom of the Pressure-Volume curve, base is lower then apex

33
Q

What is breathing like in the apex of the lung in Pulmonary fibrosis

A

As it’s still a negative pressure you will get better ventilation, at the base it will be positive

34
Q

Effects of COPD on breathing

A

There will be a large lung volume as its hard to get air out. The intrapleural pressure becomes more negative as the alveoli are stretched more, and there is higher elasticity so the lung is trying to pull back on itself. The base is slightly more positive then the apex but is still negative. Both top and bottom of the lungs are at the upper part pf the Pressure-Volume curve where compliance is low because the alveoli are overly stretched. The alveoli cant be stretched any more. Compliance is reduced to collagen deposition. A change in pressure will give a small change in volume and there will be no difference between the apex and the base.

35
Q

Dalton’s law of partial pressure

A

Partial pressure= Total pressure x fractional concentration in mixture
Px= Ptot x Fx

36
Q

Calculating the partial pressure of a gas which is saturated with water

A

The air we breathe in is wet and saturated with water vapour.
Px(wet)= (Ptot-Ph2o) x Fx(dry)
The partial pressure of the alveolar air is 150mmHg. Its calculated by subtracting the water vapour pressure from the atmospheric pressure, the water vapour pressure is 47mmHg at 47 degrees.

37
Q

What’s the atmospheric pressure

A

760 mmHg

38
Q

How the partial pressure changes when it enters the alveoli

A

The pressure of oxygen drops in the inspired air before it reaches the lower airways as the water vapour dilutes it. You also have to subtract the partial pressure of CO2 which is 40mmHg. So the actual partial pressure of oxygen in the alveolars is 100mmHg. This is the start of the oxygen cascade as it moves down its partial pressure.

39
Q

Different partial pressures

A

Ambient air = 159
Alveoli = 104
Arterial blood = 95-100
Venous blood = 40-50

40
Q

Henry’s law

A

The concentration of a gas dissolved in a liquid is proportional to its partial pressure and solubility in the blood.
(Cx= K x Px)
Cx= concentration of the gas
K is the solubility coefficient, higher for CO2 than O2, so CO2 is more souble

41
Q

Fick’s law of diffusion

A

The rate of diffusion is proportional to the following factors: area, partial pressure gradient, diffusion constant (solubility and intrinsic qualities of the substance). It is inversely proportion to barrier thickness, any condition that makes the alveolar wall thicker will make it harder (pulmonary odema).

42
Q

Why is partial pressure of oxygen in the venous system low

A

The oxygen has been taken up by the respiring tissue

43
Q

Explain the pO2 in the artery

A

The pO2 rises as it has received oxygen from the alveolus

44
Q

Oxygen cascade

A

Oxygen moves down its partial pressure gradient from a high to low pressure. As you go down this cascade the partial pressure of oxyegn decreases

45
Q

Oxygen cascade

A

Oxygen moves down its partial pressure gradient from a high to low pressure. As you go down this cascade the partial pressure of oxygen decreases

46
Q

Partial pressure of expired air- explanation

A

High because it hasn’t taken part in gas exchange

47
Q

Gas pressure of oxygen(kPa)

A 
Inspired air- 21.3
Expired air- 15.7
Alveolar air- 13.7
Pulmonary artery- 5.3
Pulmonary vein- 13.7
48
Q

How exercise affects gas transport

A

Blood crosses a pulmonary capillary in 0.75 seconds at rest. Strenuous exercise may reduce the transit time due to the increased cardiac output. There may not be enough time for complete equilibrium to occue

49
Q

2 main factors which affect gas exchange

A

It can be diffusion or perfusion (flow) limited

50
Q

Diffusion limited gas exchange

A

Problems in the alveolar barrier itself, can be Emphysema (reduced area) or fibrosis (thickened barrier).

51
Q

How can you determine if its diffusion limited gas exchange

A

The partial pressure gradient between the alveolar and the blood is always maintained because the haemoglobin mops up any excess CO. So if there is a problem with CO moving into the blood, this means there is a problem with the barrier itself (surface area or thickness)

52
Q

How can you determine if gas exchange is perfusion limited

A

N2O stays in the solution and does not bind to haemoglobin. The partial pressure increases immediately in the capillary so the partial pressure gradient is lost. When there is more blood in the capillaries it will flush out the N2O so the amount of gas transferred is limited by the delivery of new blood (flow limited).

53
Q

What is O2 limited by

A

A lot of the O2 stays in the blood solution so it is flow limited, can be diffusion limited in disease

54
Q

Effects of exercise on pulmonary ventilation

A

Mild and moderate exercise- physiological adaptions able to supply sufficient O2 to the working muscles and metabolism is aerobic.
Severe- physiological adaptions are unable to supply sufficient O2 to the working muscles and a proportion of the metabolism becomes anaerobic, which will produce lactic acid.

55
Q

How is the increase in oxygen consumption achieved

A

There is a large increase (x30) in ventilation and in cardiac output (x4-5). O2 consumption increase from 250ml/min at rest to in severe exercise 4L/min

56
Q

Ventilation change in rest and exercising

A

At rest ventilation is 5-6 L/min in severe exercise it’s 150 L/min. The changes in exercise are mediated by an increase in the frequency of breathing, at rest its 10-12/min in severe exercise its 50/min. There is an increase in tidal volume from 500ml at rest to 2-2.5L in severe exercise which is 50% of vital capacity

57
Q

Anaerobic Threshold

A

As O2 consumption increases, pulmonary ventilation slowly increases. At about 2.8L/min of O2 consumption you get to the anaerobic threshold, beyond this there is a dramatic increase in pulmonary ventilation for a modest increase in O2 consumption. The anaerobic threshold is the body’s limit in delivering O2 to the tissues, muscles will then go from aerobic to anaerobic respiration

58
Q

What increases after the anaerobic threshold

A

Pulmonary ventilation and CO2 concentration because its being produced from the protons in lactic acid

59
Q

How does the partial pressure of gases in the blood change during exercise

A

In the blood the partial pressure of O2 stays the same no matter the severity of exercise. PaCO2 stays the same till you get to the anaerobic threshold and then it drops, due to the rise in ventilation. [H+] stays the same till it gets to the anaerobic threshold and then it rises due to the production of lactic acid.

60
Q

How the V/Q ratio changes in exercise

A

Increases as exercise intensity increases. Mild and moderate exercise produces the ideal V/Q ratio due to the increase ventilation. V/Q ratio is about ventilation and perfusion.
• At rest- 0.8
• Mild and moderate- 1.0 (ideal value)
• Severe- 2-3

61
Q

How exercise affects Lung diffusing capacity

A

Increases as exercise intensity increases. It is a measure of the ability of lungs to conduct gases and for gases to get across the alveoli membrane. It is affected by the surface area available for gas exchange. It increases 4 fold in severe exercise.

62
Q

Phases of breathing in exercise

A

Once exercise starts you get a rapid increase in the pattern of ventilation (phase 1). In phase 2 the ventilation rate steadily increases till it starts to plateau out. In phase 3 exercise stops and there is a sudden decrease in the rate of ventilation and then a steady decrease.

63
Q

How chemical factors affects the ventilatory response in exercise

A

A rise in K+ levels may have a role in phase 2 and 3 of exercise. Hypoxia could effect phase 1 of ventilation as a higher ventilation rate is needed to replenish oxygen levels.

64
Q

How neural factors affect the ventilatory response in exercise

A

When exercise begins the muscles release CO2, this is detected by Mechanoreceptors and Chemo-sensitive receptors which send a signal to the CNS. This sends a signal to the lungs to increase ventilation and is the main cause of phase 1 ventilation. Controlled by motor cortex

65
Q

How do metabolic changes affect the ventilatory response in exercise

A

The CO2 concentration in the blood also increases the rate of respiration. It crosses the blood brain barrier and enters the cerebrospinal fluid (CSF). It then undergoes an equilibrium reaction and forms hydrogen ions which stimulate receptors on the medulla. This then fires to the respiratory receptors which control the ventilation rate.

Medicine year 1 semester 2 (61 decks)

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