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Human Systems > Respiration- mechanics + gas exchange > Flashcards

Respiration- mechanics + gas exchange Flashcards

1
Q

What is the meaning of respiration

A

Two meanings:​
Tissue respiration: the aerobic metabolism in cells.

Breathing: gas exchange and the associated processes

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2
Q

What is respiration mechanics

A

The study of mechanical properties of lung and chest wall ​

The process by which air enters and leaves the lungs

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3
Q

What is the job of the lungs

A

To bring in fresh air rich in the oxygen needed to fuel the body​
and to expel the waste gas
(carbon dioxide, CO2) produced from cells in the body.​

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4
Q

Why is respiratory mechanics important?​

A

To understand how lung works normally and in disease states.​

Almost all lung diseases affect mechanical properties of lung.​

Death from lung disease usually due to inability to overcome changes in lung and/or chest mechanics.​

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5
Q

What are the functions of upper airways in conducting air to lungs

A

Humidify (saturate with water)
Warm
Filter

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6
Q

What epithelium lines the upper airways

A

Pseudo-stratified ciliated, columnar epithelium

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7
Q

What is the difference between strenuous and quiet breathing

A

During inspiration in strenuous breathing there is greater contraction of the diaphragm
(1cm quiet, up to 10cm strenuous)

Respiratory skeletal muscles are active during more strenuous exercise

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8
Q

What are the average values of exchange during breathing
-At rest
-Walking
-Severe exercise

A
  • 250ml O2/min & ~200ml CO2/min​

-800ml O2/min ​& ~750ml CO2/min​

-5000ml O2/min & 6000ml CO2/min

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9
Q

What is the difference in expiration during quiet and strenuous breathing

A

Quiet - passive

Strenuous - active

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10
Q

What are some respiratory skeletal muscles

A

-Inspiratory accessory muscles active, e.g., sternocleidomastoid, alae nasi, genioglossus
-Abdominal muscles (rectus abdominus, internal oblique, external oblique and transversus abdominus)

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11
Q

What is the alveolar pressure at the beginning of inspiration

A

0 (no flow)

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12
Q

What is the functional residual capacity

A

The volume of air in the lung at the end of expiration during quiet breathing

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13
Q

When are elastic recoil and outward recoil equal

A

At FRC these forces are opposite and equal and muscles are relaxed

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14
Q

Minimal lung volume

A

30 - 120 ml

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15
Q

Which breathing is more efficient in healthy lungs

A

Low level breathing (small muscle effort)

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16
Q

Why is higher intensity breathing less efficient

A

Gas flow is turbulent, using more muscles
The accessory muscles can fatigue easily to limit exercise

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17
Q

What is:
Ppl
Pel
Pa
Pl
Pb

A

Pleural pressure
Elastic recoil pressure
Alveolar pressure
Transpulmonary pressure
Barometric pressure

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18
Q

What is the pleural space

A

Space between lungs and chest wall

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19
Q

What is the Transpulmonary pressure (P L)

A

Difference between (pleural pressure) Ppl and Pa (alveolar pressure)

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20
Q

Why is the pleural pressure always negative

A

Chest wall is constantly pulling out while lung is trying to collapse in meaning pleural pressure is always negative (forces constantly applied) therefore increase in space (muscles contract) pressure becomes more negative and when lungs relax and fill space the pressure increases again to return to normal

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21
Q

What is the process of inspiration

A
  • Beginning of inspiration, no flow: PA=0 PB=0.​
  • Inspiratory muscles contract – inc. thoracic volume.​
  • Pleural pressure becomes more negative.​
  • Increase in transpulmonary pressure.​
  • Lungs expand and alveolar volume increases.​
  • PA becomes negative (below PB).​
  • Air flows into alveoli (from higher to lower pressure).​
  • End inspiration - Muscles stop contracting, thorax and alveoli stop expanding, PA = PB (no flow).​
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22
Q

How does exhalation/expiration occur

A
  • Beginning expiration: Thoracic volume decreases. .​
  • Ppl & PL return to pre-inspiration values.​
  • Thorax and lungs recoil (elastic recoil pressure).​
  • Air in alveoli compressed.​
  • PA becomes greater than PB.​
  • Air flows out of lungs.​
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23
Q

When/why does the flow into the lungs stop

A

When atmospheric and Pa are equal

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24
Q

What is partial pressure

A

Sum of the partial pressures or tensions of a gas must be equal to total pressure

The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own

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25
Q

What is the calculation of partial pressure of gas

A

Fraction in gas mixture x barometric pressure

Pgas = Fgas x Pb

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26
Q

What is the atmospheric pressure at sea level

A

760 mmHg (barometric pressure)

PN2 + PO2 + PCO2 + PArgon + other gases​

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27
Q

What is the PO2 of 21% of O2 in air

A

PO2 = 0.21 x 760 = 159 mmHg or torr AT MOUTH​

28
Q

When saturated with water in airways the water vapour partial pressure at body temp is 47mmHg

What is the PO2

A

PIO2 = (Pb – PH2O) x FO2​
= (760 – 47 mmHg) x 0.21​
=150 mmHg or torr IN
TRACHEA​

29
Q

Do conducting airways participate in gas exchange

A

NO

30
Q

What are conducting airways

A

Bronchi containing cartilage and non-respiratory bronchioles

31
Q

What are the respiratory airways

A

Bronchioles with alveoli where gas exchange occurs (from terminal bronchioles to alveoli).​

32
Q

How long is the respiratory airways

A

5mm

33
Q

What is another term for a respiratory unit

A

Gas exchanging unit

34
Q

What is a respiratory unit

A

The basic physiological unit of the lung consisting of respiratory bronchioles, alveolar ducts and alveoli

35
Q

What volume can be contained in respiratory airways

A

2500ml

36
Q

How many alveolar sacs does an adult have

A

300-400 million

37
Q

What are the two types of epithelia cells which make up the alveoli

A

Epithelial cells type 1
-occupy 97% of surface area of alveoli
-Primary site of gas exchange

Septal cells type 2
-occupy 3%​ surface area
-Produce pulmonary​ surfactant (reduces​ surface tension)

38
Q

What shape are alveolar sacs

A

Polygonal

39
Q

How are alveoli adapted for gas exchange

A
  • Large surface area: ~100m2​
  • Very thin walls (~ 0.5um)​
  • Good diffusion characteristics​
40
Q

What are the two separate blood supplies of the lung

A

Pulmonary circulation:
Brings deoxygenated blood from heart to lung and oxygenated blood from lung to heart and then rest of body.​

Bronchial circulation:​
Brings oxygenated​ blood to lung ​parenchyma.​

41
Q

What occurs if the septal cells aren’t formed on birth (premature babies)

A

No surfactant produced therefore lung don’t have elasticity lacking ability for expansion reducing ability to breath dramatically

42
Q

What does the lymphatic system do in the lung

A

Defence and removal of lymph fluid

43
Q

Reason for two circulation systems in lungs

A

Brachial - oxygenated, systemic circulation (feeds cells and tissues of respiratory tree in order to allow processes to occur)

Pulmonary - deoxygenated, gas exchange

44
Q

What is the total blood volume in pulmonary circulation

A

500ml (10%)

45
Q

What is ventilation

A

Process by which air moves in and out of lung

46
Q

What is the distance between alveoli and RBCs

A

1-2um

47
Q

What is perfusion

A

Process by which deoxygenated blood passes through the lung and becomes oxygenated

48
Q

What is the ventilation perfusion relationship called

A

V/Q ratio

49
Q

Gas concentration gradients
LEARN

A

Pulmonary Capillary​
Alveolar Air Venous Blood​

PO2 100 ———–> 40​

PCO2 40 <———— 46​

        Systemic capillary​
  Tissues                 Arterial Blood​

PO2 <40 <————- 100​

PCO2 >46 ————-> 40​

50
Q

Why is the alveoli in apex more expanded than at the base of the lungs

A

Gravity pulls lung down and away from chest wall:​

Pleural pressure (Ppl) more​ negative at apex than at base. ​

Transpulmonary pressure (PL) is greater at apex than at base.​

Increased alveolar volume in apex.

51
Q

What is compliance

A

Refers to how much effort is required to stretch the lungs and chest wall

52
Q

What does high compliance mean

A

Lungs and chest wall expand easily

53
Q

What causes decreased compliance

A

Decreased compliance is a common
feature in pulmonary conditions:​

-Scarring in lung tissue (tuberculosis)​
-Lung filled with fluid (edema)​
-Deficiency in surfactant
production​
-Destruction of elastic fibres (emphysema)​

54
Q

What is resistance

A

Refers to any narrowing or obstruction of the airway that may reduce​ airflow

55
Q

What causes increased resistance

A

Asthma​
COPD (emphysema, chronic bronchitis) due to obstruction or collapse​ of airways

56
Q

What is a low pressure low resistance system

A

Pulmonary circulation

57
Q

What is the V/Q ratio

A

The ratio of ventilation to blood flow

58
Q

How is the V/Q ratio defined for a single alveolus compared to a lung

A

Single alveolus: ratio defined as alveolar ventilation divided by capillary flow

Lung: ratio defined as total alveolar ventilation divided by cardiac output

59
Q

What is the V/Q ratio in healthy individuals

A

LUNG = 0.8-1.2​

60
Q

When does V/Q >1

A

When ventilation exceeds perfusion

61
Q

When does V/Q < 1

A

When perfusion exceeds ventilation

62
Q

What happens to each gas in the pulmonary and systemic circuit

A

Pulmonary circuit:
O2 enters blood, CO2 leaves​

Systemic circuit:
O2 leaves blood, CO2 enters.​

63
Q

What is the most frequent cause of arterial hypoxemia in patients with respiratory disorders

A

V-Q mismatching

Some alveoli V/Q >1, some V/Q < 1

Results in varying alveolar and capillary gas contents

64
Q

What is the arterial PO2 with arterial hypoxemia

A

< 80 mmHg
(normal 100 mmHg)

65
Q

What are the regional differences in ventilation and perfusion largely due to

A

Gravity

Human Systems (34 decks)

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