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Respiratory Physiology > Lung Elasticity, Surfactant & Work Of Breathing/ Lung Capacities & Volumes > Flashcards

Lung Elasticity, Surfactant & Work Of Breathing/ Lung Capacities & Volumes Flashcards

1
Q

Define lung compliance

A

It is the change in the lung volume per unit change in transpulmonary pressure gradient (i.e. distending pressure)

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2
Q

The compliance of lung or chest alone is …. L/cm H2O, while that of lung inside chest cavity is …. L/cm H2O.
Why is this?

A

0.2
0.1
Because of the limitation effect of the chest.

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3
Q

Enumerate conditions which reduce pulmonary compliance

A
  • Pulmonary congestion & edema
  • Pulmonary fibrosis
  • Respiratory distress syndrome
  • Pneumonectomy
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4
Q

Enumerate conditions which increase lung compliance

A

Old age

Emphysema

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5
Q

GR: Loss of lung elasticity result is great difficulty in expiration.

A
  • Decreased elastic lateral contraction, leading to alveolar collapse thus increasing airway resistance.
  • Decreased elastic recoil makes passive expiration not enough to empty the lungs, thus increasing work of breathing.
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6
Q

What are the causes of recoil tendency of the lung?

A
  1. Elastic tissue in the lung & thiracic wall.
  2. Alveolar surface tension by the attractive forces between water molecules at the surface of the liquid film that lines the alveoli.
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7
Q

Lung expansion requires energy to

A

A. Stretch the elastic tissue of the lungs

B. Overcome the surface tension force of the fluid layer lining the alveoli

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8
Q

Pulmonary surfactant is secreted by ….. .

It is composed of ….,…. & ….. .

A

Type II alveolar epithelium

Phospholipids, proteins & calcium ions

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9
Q

The surfactant has hydrophilic & hydrophobic parts so it remains at the …….; the hydrophilic part is in the ….phase, while the hydrophobic part is in the ….phase.

A

Gas-liquid interface

Liquid, gas

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10
Q

Function of the surfactant

A

Decreases surface tension, thus has the following functions:

  1. Increases pulmonary compliance
  2. Reduces tendency of alveoli to recoil & collapse
  3. Keeps alveoli dry and prevent pulmonary edema
  4. Stabilize the sizes of alveoli and help keep them open
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11
Q

Apply LaPlace law on alveolus

A

The inward-directed (collapsing) pressure (P) of an alveolus is directly proportional to the surface tension (T) and inversely proportional to the radius (r)

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12
Q

GR: the density of surfactant is higher in small than large alveoli.

A

Because the alveolus with smaller radius has pressure higher than alveolus with greater radius, so surfactant decreases surafce tension in smaller alveolus more than larger alveolus. This decrease in surface tension with decrease in radius, prevent the increase in pressure in small alveoli so prevent their collapse and emptying onto larger alveoli.

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13
Q

Mention the effects of IRDS

A

Inadequate synthesis of surfactant, increase surface tension, reduced lung compliance, increased tendency of alveoli to collapse, increased work of breathing, respiratory failure and death. Pulmonary edema is developed due to fluid transudation.

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14
Q

GR: hyaline membrane disease is called so.

A

Beacuse the poteinaceous fluid filling the alveoli looks like hyaline membrane under the microscope.

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15
Q

Describe the managemnet of IRDS

A

For premature infant: surfactant replacement therapy & PEEP

For mother: glucocorticoid therapy, cortisone is used for acceleration of surfactant maturation in the fetus lungs.

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16
Q

What is PEEP?

A

Positive end-expiratory pressure

Ventilate the lungs with positive pressure ventilator and keep the alveolar pressure above the atmospheric pressure.

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17
Q

Describe the role of alveolar interdependence in keeping alveoli open.

A

A) when the alveolus in a group of interconnected alveoli starts to collapse the surrounding alveoli are stretched.
B) the neighbouring alveoli recoil in resistance to being stretched, they pull outward the collapsing alveolus.

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18
Q

GR: inspiration is an active process. Mention the percentage of each work.

A
  1. Elastic work: to overcome elastic tissue & alveolar surface tension. 65%
  2. Resistive work (airway, 80%) & (tissue, 20%)
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19
Q

The percentage of breathing from TEE

A

At rest, 3%
In streneous exercise, 5%
Poorly compliant lungs/obstructive lung disease, 30%

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20
Q

The work of breathing is increased in which situations?

A
  1. Decreased pulmonary compliance (lung fibrosis & respiratory distress syndrome)
  2. Increased airway resistance (COPD)
  3. Increased ventilation (exercise)
  4. Decreased elastic recoil (emphysema)
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21
Q

Mention factors increasing ealstic/resistive work of breathing.

A

E: pulmonary fibrosis & deficiency of oulmonary surfactant
R: tissue: sarcoidosis, airway: asthma, bronchitis & emphysema

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22
Q

The volume of air inspired/expired can be measured by ….. .

A

Spirometer

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23
Q

Define tidal volume and its normal volume

A

Volume of air entering/leaving the lungs in a single breath in resting condition
500 ml

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24
Q

Define inspiratory reverve volume and its normal value

A

Extra volume of air that can be maximally inspired over the noraml tidal volume.
3000 ml

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25
Q

Define Expiratory reserve volume and its normal value

A

It is the extra volume of air that can be expired beyond that normally passively expired.
1000 ml

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26
Q

Define residual volume and its normal value.

A

The volume of air remaining in the lungs after the most forceful expiration. Expelled when chest is opened and lungs collapse.
1200 ml

27
Q

Amount of air that remains after opening the chest

A

Minimal air, 150 ml

28
Q

Significance of residual volume

A
  1. Maintains aeration between breaths
  2. Prevents marked changes in arterial concentration of O2 & CO2 which may disturb respiratory function.
  3. Prevents lung collapse & helps easy inflation
  4. Normally is 20% of lung capacity, and increases in bronchial asthma & emphysema.
  5. Medicolegal importance: in determining if an infant is stillborn or killed.
29
Q

Define inspiratory capacity and its normal value.

A

The maximum volume of air that can be inspired by maximal forced inspiration following a normal quiet expiration.
3500 ml

30
Q

Define functional residual and its normal value

A

Volume of air remaining in lungs after a normal passive expiration
2200 ml

31
Q

Define total lung capacity and its normal value

A

Volume of air present in lungs after maximal forced inspiration
5700 ml

32
Q

Define vital capacity and its normal value

A

The volume of air expelled from the lungs by maximal forced expiration following maximum deep inspiration.
4500 ml

33
Q

All pulmonary capacities & volume are …… in men than in women, they are ….. in atheletic than asthenic people thus a measure of physical fitness.

A

20-25% more

Larger

34
Q

Mention the factors affecting vital capacity

A
  1. Strength of respiratory muscles
  2. The range of diaphragm mobility
  3. Lung compliance
35
Q

Conditions affecting diaphragm mobility

A

Chest deformities
Painful chest conditions (fractured rib , pleurisy)
Increased abdominal contents (pregnancy & ascites)

36
Q

Conditions affecting lung compliance

A

Pulmonary fibrosis
RDS
Pulmonary congestion

37
Q

Define forced vital capacity and its normal value.

A

Timed vital capacity
Largest amount of air that can be expired as deep and as fast as possible after a maximal inspiratory effort.
Normal people can expire FVC in 4 to 6 sec

38
Q

Define FEV1 , normal FEV1/FVC % and its value in obstructive lung disease

A

Amount of FVC expired during the first second of forced expiration
80%
Decreased

39
Q

Describe the clinical importance of measuring FVC & FEV1

A 
Indicates the maximal air flow that is possible from the lungs.
Differentiated obstructive (difficulty emptying the lungs) from restrictive (difficulty in filling the lungs).
40
Q

FRC & RV are ….. in obstructive lung diseased , and FEV1/FVC % is …..

A

Increased

Less than 80%

41
Q

Enumerate examples of restrictive lung diseases.

A

Abnormalities in lung tissue, pleura, chest wall & neuromuscular machinery.
e.g. pulmonary fibrosis, RDS & thoracic cage deformity

42
Q

Mention 3 values that are reduced in restrictive lung disease

A

TLC, inspiratory capacity & FVC

43
Q

In restrictive lung disease, FEV1/FVC is ….

A

Normal or even higher

44
Q

Define pulmonary ventilation & its normal value.

A

The volume of air breathed in or out in one minute at rest

6 L/min

45
Q

Define maximum voluntary ventilation and its normal value.

A

It is the maximal volume of air that can be inspired or expired per minute by the deepest and fastest breathing.
80-170 L/min in men
60-120 L/min in women

46
Q

The MVV is done for how much time and why?

A

15 seconds

To avoid effects of washout of CO2 on ventilation

47
Q

GR: The increase in TV is more important than increase in RR.

A

Because of the presence of anatomical dead space

48
Q

What is the importance of MVV?

A

It is affected by all factors which affect vital capacityy but its measurement is preferred because it can never be normal in lung diseases (it indicates lung dysfunction) while vital capacity can be normal in early stages of some lung diseases.

49
Q

Determination of breathing reserve is good test for …

A

The functional reserve of the respiratory system

50
Q

Normal BM/MBC, and its value in case of dyspnea

A

90%

70%

51
Q

Define anatomical dead space and its percentage of TV

A

It is the volume of air in the conducting airways (nasal cavity, pharynx, trachea, bronchi & terminal bronchioles), where no gas exchange takes place.
30% of TV

52
Q

Dead space normal value

A

150 ml

53
Q

Mention factors increasing and decreasing anatomical dead space.

A

Inc - inspiration/bronchodilatation

Dec - supine position, bronchoconstriction & endotracheal intubation.

54
Q

Define alveolar dead space.

A

It is the volume of gas within unperfused alveoli, thus not participating in gas exchange.

55
Q

GR: the match between air & blood is not always perfect

A

Because not all alveoli are equally ventilated with air & perfused with blood.

56
Q

GR: Normally physiological almost = anatomical dead space

A

Beacuse all alveoli are functioning in normal lung

57
Q

Mention the factor increasing anatomical dead space

A

Increased breathing rate

58
Q

GR: Expired air contains higher PO2 and less PCO2 than alveolar air

A

Because expired air is a mixture of dead space air (fresh atm air) and alveolar air (old air).

59
Q

Alveolar ventilation is …. than pulmonary ventilation.

A

Less

60
Q

GR: Rapid shallow breathing produces less alveolar ventilation than slow deep breathing at the same pulmonary ventilation.

A

In rapid shallow breathing, the dead space volume increases which decreases alveolar ventilation , causing hypoxia.

61
Q

Mention two modifications to air caused by presence of dead space.

A
  • Humidification and warming of inspired air.
  • It protects alveoli from damage by bacteria and foreign particles by:
    1. Filtration action of nose that removes dust and large foreign particles from inspired air.
    2. Foreign particles stich to mucus the expelled by sneezing & coughing.
62
Q

…… produced by larynx & ….. by nose ;due to presence of dead space

A

Phonation

Smell sensation

63
Q

During exercise we should breathe ….. to….

A

Slowly & deeply to increase alveolar ventilation

64
Q

Define pulmonary ventilation

A

It is the volume of air breathed in/out the lungs in one minute.

Respiratory Physiology (5 decks)

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