Respiratory 4

Question 1

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

10cm fibrocartilaginous tube stretching from C6 to the sternal angle
Cervical portion: inferior boundary: imaginary line of the thoracic inlet
Mediastinal (thoracic) portion: crosses from the anterior mediastinum to the posterior mediastinum
Lined with pseudostratified columnar ciliated epithelium and goblet cells
Superiorly, bordered by the larynx
Posterior relation: oesophagus
Right lateral relations: pleura, lung, and the vagus nerve; azygous vein inferiorly
Left lateral relation: left common carotid and subclavian arteries, arch of the aorta, left recurrent laryngeal nerve
Anterior relations: skin and thyroid superiorly, SVC
Inferior relations: right pulmonary artery
Supplied by the inferior thyroid and bronchial arteries; veins drain to the inferior thyroid plexus.
Innervated by the vagus and T2-6 sympathetic chain

Answer 1

deranged

The trachea:

10cm fibrocartilaginous tube stretching from C6 to the sternal angle
Cervical portion: inferior boundary: imaginary line of the thoracic inlet
Mediastinal (thoracic) portion: crosses from the anterior mediastinum to the posterior mediastinum
Lined with pseudostratified columnar ciliated epithelium and goblet cells
Superiorly, bordered by the larynx
Posterior relation: oesophagus
Right lateral relations: pleura, lung, and the vagus nerve; azygous vein inferiorly
Left lateral relation: left common carotid and subclavian arteries, arch of the aorta, left recurrent laryngeal nerve
Anterior relations: skin and thyroid superiorly, SVC
Inferior relations: right pulmonary artery
Supplied by the inferior thyroid and bronchial arteries; veins drain to the inferior thyroid plexus.
Innervated by the vagus and T2-6 sympathetic chain

Question 2

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

x cm fibrocartilaginous tube stretching from x to the x

Answer 2

deranged

The trachea:

10cm fibrocartilaginous tube stretching from C6 to the sternal angle

Question 3

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Cervical portion: x

Answer 3

deranged

The trachea:

Cervical portion: inferior boundary: imaginary line of the thoracic inlet

I don’t understand, it would be inferior if a person was laying down supine

Question 4

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Mediastinal (thoracic) portion: x

Answer 4

deranged

The trachea:

Mediastinal (thoracic) portion: crosses from the anterior mediastinum to the posterior mediastinum

note; does this imply the trachea moves posterior as it descends

Question 5

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Lined with X

Answer 5

deranged

The trachea:

Lined with pseudostratified columnar ciliated epithelium and goblet cells

Question 6

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Superiorly, bordered by the X

Answer 6

deranged

The trachea:

Superiorly, bordered by the larynx

Question 7

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Posterior relation: X

Answer 7

deranged

The trachea:

Posterior relation: oesophagus

Question 8

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Right lateral relations: X

Answer 8

deranged

The trachea:

Right lateral relations: pleura, lung, and the vagus nerve; azygous vein inferiorly

Question 9

The azygos vein is

i always forget this

Answer 9

The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava

Question 10

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Left lateral relation: X

Answer 10

deranged

The trachea:

Left lateral relation: left common carotid and subclavian arteries, arch of the aorta, left recurrent laryngeal nerve

Question 11

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Anterior relations: X

Answer 11

deranged

The trachea:

Anterior relations: skin and thyroid superiorly, SVC

Question 12

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Inferior relations: X

Answer 12

deranged

The trachea:

Inferior relations: right pulmonary artery

Question 13

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Supplied by the X and X arteries; veins drain to the X

Answer 13

deranged

The trachea:

Supplied by the inferior thyroid and bronchial arteries; veins drain to the inferior thyroid plexus.

Question 14

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The trachea:

Innervated by the X and X

Answer 14

deranged

The trachea:

Innervated by the vagus and T2-6 sympathetic chain

Question 15

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

The bronchi:

• The left main bronchus is longer, runs more horizontally and is about twice as long as the right main bronchus.
• Dichotomously branching divisions of increasingly smaller tubes, consisting of complete and incomplete cartilaginous rings as well as smooth muscle
  o Gen 1-4: bronchi (cartilaginous)
  o Gen 5-14: bronchioles (no cartilage)
  o Gen 15-18: Respiratory bronchioles (some gas exchange)
  o Gen 19-22: alveolar ducts
  o Gen 23: alveolar sacs
• Supplied by bronchial arteries and pulmonary circulation
• Venous drainage of the right main bronchus is into the azygos vein, and the left main bronchus drains into the accessory hemiazygos vein.
• Innervated by the vagus and T2-6 sympathetic fibres

Answer 15

deranged

The bronchi:

• The left main bronchus is longer, runs more horizontally and is about twice as long as the right main bronchus.
• Dichotomously branching divisions of increasingly smaller tubes, consisting of complete and incomplete cartilaginous rings as well as smooth muscle
  o Gen 1-4: bronchi (cartilaginous)
  o Gen 5-14: bronchioles (no cartilage)
  o Gen 15-18: Respiratory bronchioles (some gas exchange)
  o Gen 19-22: alveolar ducts
  o Gen 23: alveolar sacs
• Supplied by bronchial arteries and pulmonary circulation
• Venous drainage of the right main bronchus is into the azygos vein, and the left main bronchus drains into the accessory hemiazygos vein.
• Innervated by the vagus and T2-6 sympathetic fibres

Question 16

2019 august Q5 and 2016 august Q24

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

examiner comment

Answer 16

deranged

2019 august Q5
Describe the anatomical course and relations of the trachea and bronchial tree (to the level of the segmental bronchi)

Better answers included details of the significant structures related to the cervical and mediastinal trachea and bronchi. The lobar branches and bronchopulmonary segments requiring naming to attract full marks. Many answers lacked sufficient detail or contained inaccuracies regarding vertebral levels and key structural relations. Some candidates discussed the general anatomy of the airway, including the larynx, structure of the airways, blood supply and innervation. This did not attract marks.

2016 august Q24
24 Outline the tracheal (60% of marks) and left and right main bronchial anatomy (40% of marks) in an adult.

To pass this question, the following were required for each section (trachea and main bronchi):
landmarks; basic structural anatomy; and important relations (major vessels; major nerves;
major structures).
Marks were also allocated for innervation, and blood supply and venous drainage of the
trachea.
Most unsuccessful answers did not address a number of these areas. Overall, the answers
were better for tracheal anatomy compared to bronchial anatomy.
A structured approach to anatomy questions works well and this was again the case (i.e.
relations / blood supply / etc.

Question 17

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

Closing capacity is the x

It can also be defined as x

Answer 17

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

Closing capacity is the maximal lung volume at which airway closure can be detected in the dependent parts of the lungs
It can also be defined as the volume at which transition from Phase III to Phase IV occurs during an inert gas washout measurement.

Question 18

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

• Closing capacity is composed of x

Answer 18

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

• Closing capacity is composed of residual volume (RV) and closing volume.

Question 19

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

Closing capacity is altered by:

Answer 19

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

Closing capacity is altered by:
Expiratory air flow: (higher flow = higher CC)
Expiratory effort (more effort = higher CC)
Small airways disease, eg. asthma or COPD
Increased pulmonary blood volume, eg in CCF
Decreased pulmonary surfactant
Parenchymal lung disease, eg. emphysema
Age (increasing age = increased closing capacity)
At age 44, supine FRC is lower than closing capacity
At age 66, erect FRC is lower than closing capacity

Question 20

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

Closing capacity can be measured by:

Answer 20

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

Closing capacity can be measured by:

1Gas bolus measurement, where a subject inhales a small bolus of tracer gas, starting at RV
2Resident gas method, where a subject inhales a TLC of oxygen, starting from RV
Both methods produce a graph of gas concentration over volume, which has four distinct phases.

Question 21

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

1Gas bolus measurement,

Answer 21

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

1Gas bolus measurement, where a subject inhales a small bolus of tracer gas, starting at RV

Question 22

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

2Resident gas method,

Answer 22

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

2Resident gas method, where a subject inhales a TLC of oxygen, starting from RV

Question 23

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

The significance of closing capacity is:

Answer 23

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

The significance of closing capacity is:
Higher CC decreases the effect of pre-anaesthetic preoxygenation
Higher CC increases dependent atelectasis
It is responsible for the age-related decrease in oxygenation, because of shunt
It aggravates lung injury through cyclic atelectasis

Question 24

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

examiner comment

Answer 24

2019 aug
7 Define closing capacity (10% of marks). Describe the factors that alter it (30% of
marks), its clinical significance (30% of marks) and one method of measuring it

College Answer
Many candidates confused the factors that affect closing capacity (CC) with factors which affect functional residual capacity (FRC). Some candidates confused airway closure with expiratory flow limitation secondary to dynamic airway compression.

A good answer would have included the following:

Small airway closure occurs because the elastic recoil of the lung overcomes the negative intrapleural pressure keeping the airway open. Thus, airway closure is more likely to occur in dependant parts of the lung where airways are smaller. Normally closing capacity is less than FRC in young adults but increases with age. Closing capacity becomes equal to FRC at age 44 in the supine position and equal to FRC at age 66 in the erect position. Closing capacity is increased in neonates because of their highly compliant chest wall and reduced ability to maintain negative intrathoracic pressures. In addition, neonates have lower lung compliance which favours alveolar closure. Closing capacity is also increased in subjects with peripheral airways disease due to the loss of radial traction keeping small airways open.

The consequences of airway closure during tidal breathing include shunt and hypoxaemia, gas trapping and reduced lung compliance. In addition, cyclic closure and opening of peripheral airways may result in injury to both alveoli and bronchioles. Closing volume (CV) may be measured by the single breath nitrogen washout test or by analysis of a tracer gas such as xenon during a slow exhaled vital capacity breath to residual volume. Residual volume (RV) cannot be measured directly but is calculated as follows: the FRC is measured using one of three methods: helium dilution, nitrogen washout or body plethysmography. The expiratory reserve volume (ERV) may be measured using standard spirometry. Using the measured FRC and ERV we may calculate RV from the equation:

RV = FRC – ERV. Then CC = RV + CV..

note: as you age, does FCR decrease or closing capacity increase??

Question 25

i just keep forgetting

what is the dependent part of the lung

Answer 25

The lowest part of the lung in relation to gravity is called the dependent region. In the dependent region smaller alveolar volumes mean the alveoli are more compliant (more distensible) and so capable of more oxygen exchange.

• Wikipedia

Question 26

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is respiratory compliance??

Answer 26

deranged

• Respiratory compliance is defined as the change in lung volume per unit change in transmural pressure gradient. It is usually about 100ml/cm H2O.
• Static compliance is defined as the change in lung volume per unit change in pressure in the absence of flow. It is composed of:
  o Chest wall compliance (usually 200ml/cm H2O.
  o Lung tissue compliance (also usually cm H2O.)

Question 27

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is static compliance??

Answer 27

deranged

• Respiratory compliance is defined as the change in lung volume per unit change in transmural pressure gradient. It is usually about 100ml/cm H2O.
• Static compliance is defined as the change in lung volume per unit change in pressure in the absence of flow. It is composed of:
  o Chest wall compliance (usually 200ml/cm H2O.
  o Lung tissue compliance (also usually cm H2O.)

Question 28

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is Chest wall compliance?

Answer 28

deranged

• Respiratory compliance is defined as the change in lung volume per unit change in transmural pressure gradient. It is usually about 100ml/cm H2O.
• Static compliance is defined as the change in lung volume per unit change in pressure in the absence of flow. It is composed of:
  o Chest wall compliance (usually 200ml/cm H2O.
  o Lung tissue compliance (also usually cm H2O.)

Question 29

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is Lung tissue compliance?

Answer 29

deranged

• Respiratory compliance is defined as the change in lung volume per unit change in transmural pressure gradient. It is usually about 100ml/cm H2O.
• Static compliance is defined as the change in lung volume per unit change in pressure in the absence of flow. It is composed of:
  o Chest wall compliance (usually 200ml/cm H2O.
  o Lung tissue compliance (also usually cm H2O.)

Question 30

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is Dynamic compliance?

Answer 30

deranged

• Dynamic compliance is defined as the change in volume divided by change in pressure, measured during normal breathing, between points of apparent zero flow at the beginning and end of inspiration. Its components are:

o Chest wall compliance
o Lung tissue compliance
o Airway resistance (which makes it frequency-dependent)

Question 31

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is Dynamic compliance?

Answer 31

deranged

• Dynamic compliance is defined as the change in volume divided by change in pressure, measured during normal breathing, between points of apparent zero flow at the beginning and end of inspiration. Its components are:

o Chest wall compliance
o Lung tissue compliance
o Airway resistance (which makes it frequency-dependent)

Question 32

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

3 things that make up dynamic compliance??

Answer 32

deranged

o Chest wall compliance
o Lung tissue compliance
o Airway resistance (which makes it frequency-dependent)

Question 33

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what is Specific compliance?

Answer 33

deranged

• Specific compliance is compliance that is normalized by a lung volume, usually FRC. It is used to compare compliance between lungs of different volumes (eg. child and adult)
  Factors which affect compliance can be divided into chest wall factors and lung factors:

Question 34

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

Factors which affect compliance can be divided into ??

Answer 34

deranged

Factors which affect compliance can be divided into chest wall factors and lung factors:

Question 35

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what increases lung compliance

Answer 35

deranged

Increased lung compliance

Lung surfactant
Lung volume: compliance is at its highest at FRC
Posture (supine, upright)
Loss of lung conective tissue associated with age
Emphysema

Question 36

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what increases lung compliance

Answer 36

deranged

Increased lung compliance

Lung surfactant
Lung volume: compliance is at its highest at FRC
Posture (supine, upright)
Loss of lung conective tissue associated with age
Emphysema

Question 37

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what decreases lung compliance

Answer 37

deranged

Decreased static lung compliance

1Loss of surfactant (eg. ARDS)

2Decreased lung elasticity
-Pulmonary fibrosis
-Pulmonary oedema

3Decreased functional lung volume
-Pneumonectomy or lobectomy
-Pneumonia
-Atelectasis
-Small stature

4Alveolar derecruitment
5Alveolar overdistension

Question 38

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

what Decreases dynamic lung compliance

Answer 38

deranged

Decreased dynamic lung compliance

Increased airway resistance (eg. asthma)
Increased air flow (increased resp rate)

Question 39

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

Increased chest wall compliance

Answer 39

deranged

Increased chest wall compliance

Ehler-Dahlos syndrome and other connective tissue diseases associated with increased connective tissue elasticity
Rib resection
Cachexia
Flail segment rib fractures
Open chest (eg clamshell)

Question 40

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

decreased chest wall complance

Answer 40

deranged

Decreased chest wall compliance

Structural abnormalities
-Kyphosis / scoliosis
-Pectus excavatum
-Circumferential burns
-Surgical rib fixation

Functional abnormalities
-Muscle spasm, eg. seizure or tetanus

Extrathoracic influences on chest/diaphragmatic excursion
-Obesity
-Abdominal compartment syndrome
-Prone position

Question 41

2019 aug - Explain respiratory compliance and outline the factors that affect it.

2017 march Briefly describe the factors that affect lung compliance

examiners comments

Answer 41

2019 aug - Explain respiratory compliance and outline the factors that affect it.

Answers were generally well structured. Better answers described lung and chest wall compliance and the pressures which are used to calculate compliance. Better answers displayed an understanding of dynamic, static and specific compliance and provided a reasonably comprehensive list of the physiological factors affecting chest and lung compliance.

2017 march 14 Briefly describe the factors that affect lung compliance

This question was generally well answered with good structure.

Question 42

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

How is lung compliance measured?

Answer 42

deranged

• Supersyringe method:*
• Constant flow method:
• Multiple occlusions methods
• Limitations of all methods of measuring static compliance:
• Measurement of dynamic compliance
• Measurement of volume
• Measurement of pressure

Question 43

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

• Supersyringe method:

Answer 43

deranged

• Supersyringe method:
  o Static compliance is measured by inflating the lung in volume increments, usually 100ml
  o Time (~23-3 seconds) is allowed for gas pressure to equilibrate between units with different time constants
  o This is the gold standard for measuring static compliance
  o The disadvantage is the time it takes to perform (minutes) and the need to disconnect the patient from the ventilator

Question 44

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

• Constant flow method:

Answer 44

deranged

• Constant flow method:
  o A low inspiratory flow (as low as 1.7L/min) is administered over 10-15 seconds
  o A low expiratory flow is then controlled to observe the expiratory pressure change
  o Because the flow is low, airway resistance is said to contribute minimally
  o This method has a tendency to underestimate inspiratory compliance and overestimate expiratory compliance
  o The advantage is that one does not need to disconnect the patient from the ventilator

Question 45

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

• Multiple occlusions methods

Answer 45

deranged

• Multiple occlusions methods
  o During normal ventilator function, breath occlusions are repeated at different volumes, with normal breaths in between.
  o The advantage is that there is no need to discontinue normal ventilation, and that the process can easily be automated.

Question 46

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

*Limitations of all methods of measuring static compliance:

Answer 46

deranged

• Limitations of all methods of measuring static compliance:
  o All methods usually require the patient to be sedated and paralysed
  o There is the possible escape of gas into the pulmonary circulation, which gradually decreases the lung volume during measurement
  o Changes in gas pressure associated with increased humidity and temperature are ignored

Question 47

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

• Measurement of dynamic compliance

Answer 47

deranged

• Measurement of dynamic compliance
  o Occurs during normal ventilator function, and makes no attempt to correct for pressure produced by airway resistance
  o Usually automated and integrated into modern ventilator function

Question 48

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

• Measurement of volume

Answer 48

• Measurement of volume

o Volume in modern ventilators is measured by measuring flow recordings over time, and reconstructing volume from these
o Volume can also be measured directly by the supersyringe method
o Some older ventilators (eg. piston models) measured volume directly as a part of their normal function.

Question 49

2014 march What is lung compliance and how is it measured?

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

examiners comments

Answer 49

2014 march 15 What is lung compliance and how is it measured?

There was a good understanding of the definitions of compliance but many candidates failed
to clearly demonstrate an understanding of the difference between static and dynamic
compliance. Many candidates had little knowledge of how compliance is measured. It was
expected that descriptions of methods to measure static and dynamic compliance would be
provided. There were frequent errors in descriptions that were provided.

2011 august - Define lung compliance (30% marks). Describe how is it measured (70% marks).

This is a core area of physiology that relates to everyday Intensive Care practice, thus it was
expected that more than the observed number of candidates would have scored well. Candidates
performed poorly purely from a lack of sufficient knowledge. Easy marks were to be gained
purely by mentioning that compliance is defined by ∆V/∆P, the ∆P being the gradient from
alveolar – intrapleural, normal values, static and dynamic compliance. Good answers would then
include a mention of how static and dynamic compliance is measured (specifically how volume
and pressures are measured.

Question 50

2007 AUG 13 - Briefly describe the factors that affect lung compliance

answer is a repeat

so this is just examiner comments

Answer 50

Main points/concepts expected in answer.
* Surfactant * increases lung compliance * decreases surface tension at alveolar air -water- interface *prevents small alveoli from collapsing *accounts for most of hysteresis in intact lung
* Lung elastic recoil * lung compliance changes in disease states
* Lung volume * lung compliance greatest around FRC * lung compliance reduced at low and high lung volumes * gravitational effects on regional lung compliance
* Pulmonary blood volume * pulmonary venous congestion reduces lung compliance
* Lung size * specific compliance = lung compliance / FRC
* Dynamic lung compliance * influenced by airways resistance * lung compliance measured during normal breathing * less than static lung compliance * frequency dependence