Mechanics of Ventilation

Question 1

What are the four steps of external respiration ?

Answer 1

1. ventilation or gas exchange between the atmosphere and air sacs in the lungs
2. exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries
3. transprot of O2 and CO2 by the blood between the lungs and the tissues
4. exchange of O2 and CO2 between the blood in the systemic capillaries and the tissues cells
   5.

Question 2

what are the non-respiratory functions of respiratory system?

Answer 2

• Smell & Taste
• Vocalisation; speech & singing.
• Route for water loss and heat elimination - inspired air is humidified and warmed by the respiratory airways before it is expired.
• Defense at major portal of entry for pathogens

–Mechanical and chemical defenses

•Mucociliary clearance system

Question 3

what is the pupose of the mucociliary clearance system?

Answer 3

• protects the respiratory system by trapping and removing inhaled viruses and bacteria- toxic and non-toxic particles -
• coordinated wave like movmement of cilia
• 1 cigarette paralyses cilia for several hours

Question 4

what is the main function of the upper airways?

Answer 4

to condition inspired air so by the time it reaches the lower airways it is at body temp and is humidified

Question 5

what is the major funciton of the lower airways?

Answer 5

gas exchange - the lungs are ideally structured for gas exchange- which occurs by diffusion across a membrane -

•Fick’s Law of Diffusion: The greater the surface area and the shorter the distance; the greater the rate of diffusion

Question 6

why is the pleural pressure less thant he pulmonary pressure?

Answer 6

•Why?

–The lungs are stretched and under tension (pulling inwards)

–The chest wall is under tension (pulling outwards) creates a vacuum = negative pressure

*which is why a puncture in the pleural cavity results in a collapse of the lung due to pressure in the cavity

Question 7

describe the 8 events of inspiration

Answer 7

1. Inspiratory muscles contract
2. The diameter of the thoracic cage increases
3. Intrapleural pressure (PPL) becomes more negative
4. Transmural pressure (PTM) increases and causes alveoli to swell or open
5. Intra-alveolar pressure falls relative to atmospheric pressure
6. Air flows down pressure gradient from atmosphere to alveoli
7. Tidal volume (VT) of about 500 mls is added to resting volume or FRC
8. At end of inspiration – no airflow and intra-alveolar pressure = atmospheric pressure.

Question 8

what are the inspiratory msucles?

Answer 8

Question 9

what is the law responsible for respiration?

Answer 9

boyles law - which says that as pressure increases, volume decreases and as volume increases, presure decreases

*at constant temp

Question 10

What is the FEV1?

Answer 10

it is the forced expiratory volume in one second - determined in pulmonary funciton test

FEV1/FVC = 80% for a healthy person

Question 11

using spirometry, how would you distinguish obstructive vs. restrictive lung disease?

Answer 11

FEV1/FVC reduced with obstructive diseases (asthma/COPD)

FEV1 decreased but FEV1/FVC normal or increased in restrictive diseases (lung fibrosis/scoliosis)