SESSION 5: PULMONARY VENTILATION

Question 1

what changes occur in the thoracic cavity ? (muscle action)

Answer 1

• increase/decrease in anterior posterior diameter - rib cage
• increase/decrease in inferior-superior diameter - diaphragm

Question 2

what muscles are involved in inspiration?(5)

Answer 2

-Diaphragm (phrenic nerve)
-external intercostals (ant rami of thoracic spinal nerves T1-T11)
- Sternocleidomastoid (accessory nerve)
- scalenus (C3-C8)
- anterior serratus (long thoracic nerve)

Question 3

define tidal volume

Answer 3

• volume of air inspired or expired with each normal breath (500ml)

Question 3

quiet breathing: explain what happens in quiet inspiration(4)

Answer 3

• it is an active process of 2 seconds
• increase in superior-inferior diameter : diaphragm contracts
• moved down 1,5 cm
• phrenic nerve involved (C3-5)

Question 4

what happens in quiet expiration?

Answer 4

• passive process of 3 seconds
• elastic recoil: diaphragm relaxes
  ( the elastic recoil compresses lungs and expels air)

Question 5

what happens in forced inspiration?

Answer 5

• it is an active process (exercise)
• increase in superior-inferior diameter (diaphragm contracts)-moves down 7,5 cm
• increase in anterior-posterior diameter (external intercostals and neck muscles involved)
  -3000ml

Question 6

what happens in forced expiration?

Answer 6

• active process (coughing, singing)
• decrease in superior-inferior diameter
• decrease in anterior-posterior diameter
• 1100ml
• EXPIRATORYRESERVE VOLUME = 1100ml

Question 7

define Boyle’s law

Answer 7

relationship between pressure and volume

“THE PRESSURE (P) OF A MASS OF GAS AT A CONSTANT TEMPERATURE IS INVERSELY PROPORTIONAL TO ITS VOLUME (V).”

Question 8

what Three different pressure considerations is important in ventilation ?

Answer 8

1. Atmospheric (barometric) pressure
2. Alveolar pressure (intrapulmonary pressure) - pressure within the alveoli
3. Pleural pressure (intrapleural/intrathoracic pressure) – pressure (slightly negative pressure) within the pleural cavity in between 2 pleural layers

Question 9

describe the alveolar pressure changes during inspiration and expiration

Question 10

describe the pleural pressure changes during inspiration and expiration

Question 11

what is meant by transpulmonary pressure?

Question 12

what is meant by compliance of the lung

Answer 12

THE EXTENT TO WHICH THE LUNGS EXPAND FOR EACH UNIT INCREASE IN TRANSPULMONARY PRESSURE.
* EVERY TIME TRANSPULMONARY PRESSURE INCREASES WITH 1 CM WATER, LUNG VOLUME INCREASES WITH 200 ML AIR.
* IF ELASTICITY IS HIGH, COMPLIANCE IS LOW, AND VICE VERSA.

Question 13

what determines compliance

Answer 13

• 1/3 ELASTIC FORCES OF LUNG TISSUE (ELASTIN, COLLAGEN).
• 2/3 ELASTIC FORCES CAUSED BY THE SURFACE TENSION BETWEEN THE AIR IN THE ALVEOLI AND THE LAYER OF FLUID LINING THE ALVEOLI.

Question 14

what is the function of surfactant?
briefly describe it’s production and what it consists of

Question 15

what is LaPLace law?

Answer 15

• the pressure inside the alveoli is inversely proportional to its radius
• when alveoli are small, alveolar pressure increases

Question 16

what happens in premature babies when there is a lack of surfactant?
how is this treated?

Answer 16

• the alveoli will collapse
• the alveoli will be small (decreased radius) which will lead to an increase in alveolar pressure - increased work of breathing
• this leads to Respiratory distress syndrome in baby
• Treatment: continuous positive airway pressure (CPAP), fetal and maternal glucocorticoids, synthetic surfactant

Question 17

name 3 functions of surfactant

Question 18

what is meant by work of breathing

Question 19

what determines work of breathing

Question 20

respiratory rate in adults and neonates?

Answer 20

• adults: 12 per minute
• neonates: 40 per minute

Question 21

what is minute respiratory volume

Answer 21

total volume of air a person breathe in one minute
= VT x RR
= 500ml x 12
= 6L/min
* young adult male

Question 22

alveolar ventilation: Va

Answer 22

Alveolar Ventilation (VA) = (Tidal Volume - Dead Space Volume) × Respiratory Rate
VA= (VT - VD) x RR
= (500-150) x 12

Question 23

anatomic dead space?

Answer 23

150ml in adult
Anatomic dead space refers to the portion of the respiratory system where air flows during inhalation and exhalation but does not participate in gas exchange with the bloodstream. This includes the conducting airways such as the trachea, bronchi, and bronchioles.

Question 24

alveolar dead space

Answer 24

0ml in adults
- due to poor pulmonary circulation despite good ventilated - wasted ventilation
-it’s the volume of air within the alveoli that does not contribute to oxygenation of the blood or removal of carbon dioxide.

Question 25

physiologic dead space

Answer 25

anatomic + alveolar dead space = 150ml

Question 26

DEFINE FEV1 AND FVC

Answer 26

FEV1 : forced expiratory volume in first second after max inspiration
FVC: forced expiratory vital capacity
* normal ratio = 80%
abnormal= less than 80%

Question 27

abnormalities in maximum expiratory flow: constricted lungs vs obstructed lungs

Answer 27

1. Constricted lungs
   - lung fibrosis/ TB/ silicosis
   - kyphosis/scoliosis/ fibrotic pleurisy
   - reduce residual volume (RV)
   - reduce total lung capacity (TLC)
   - reduced MEF
   - reduced FEV1
   - difficult in and out - less in , less out
2. Obstructed lungs
   - asthma/ emphysema
   - increase RV and TLC but expiration is compromised
   - reduced MEF
   - reduced FEV1

Question 28

functional residual volume

Answer 28

Expiratory reserve volume + residual volume
- Amount of air that remains in lungs at end of normal expiration (2500ml)

Question 29

inspiratory capacity

Answer 29

Tidal volume + inspiratory reserve volume
- Amount of air (3500ml) a person can breathe in
- Begins at normal expiratory level and distends lungs to maximum amount

Question 29

vital capacity

Answer 29

Inspiratory reserve volume + tidal volume + expiratory reserve volume
- Maximum amount a person can expel from lungs
after first filling lungs to maximum extend and then
expiring maximum extend (4600ml)

Question 30

total lung capacity

Answer 30

Vital capacity + residual volume
- Maximum volume to which lungs can be expanded
with greatest possible effort (5800ml)