pulmonary ventilation

Question 1

dead space air

Answer 1

some of the air a person breathes never reaches the gas exchange areas but simply fills respiratory passages such as the nose, pharynx, and trache where gas exchange does not occue. this is called dead space air because it is not useful for gas exchange

• 150 ml
• since the dead space is due to the structural arrangement (anatomy) of the airways, often it is referred to as anatomical dead space
• on experience this air js expired first. therefore it is very disadvantageous for removing the expiratory gases from the lungs
• The subject takes a breath of pure O2 and the instantaneous N2 conc. of exhaled air and
  volume of exhaled air are measured. Then a curve is plotted with N2 conc. on vertical from N2 indicates anatomic dead space and is calculated by.

Question 2

physiological dead space

Answer 2

total dead space which includes both the anatomical and alveolar dead space (vol of air in these alveoli is referred to as alveolar dead space)

alveolar is very negligible in most individuals
so anatomical dead space is almost equal with the physiological dead space.
however in people with partially functional or non functional alveoli - PDS may be as much as 10 times the volume of ADS or 1-2 L

Question 3

alveolar ventilation

Answer 3

the vol of air that actually reaches the alveoli per minute

• first dead space vol is subtract from the tidal volume and then multiplied by breathing (respiratory) rate

500-150 x 12
= 350 x 12
= 4200 ml/min

significance:

• even in absence of lung diseases, if ADS is inc then alveolar ventilation dec
• to improve alveolar ventilation, it is imp to inc the depth of breathing than frequency

clinical abnormalities
1) hypoventilation - depression of respiratory centres by diseases or drugs (central hypoventilation) and failure of the ventilatory apparatus
occurs in:
- exacerbation of chronic lung disease - asthma, chronic bronchitis, and emphysema
- depression of respiratory centres
- neuromuscular disorders - weaken the respiratory m eg. myasthenia gravis, poliomyelitis, acute polynephritis Nd tetanus.

hypoxia occurs due to dec o2 supply
hypocapnia - dec co2 removal

hyper ventilation

• due to stimulation kf Respiratory centerz
• excess removal of co2 - respiratory alkalosis

Question 4

maximum voluntary ventilation

Answer 4

mvv is the largest volume of air that an individual can breathe into and out of the lungs in 1 minute with maximum voluntary effort.

volume measured in 10 seconds x 60 secs/10secs
= volume measured in 10 seconds x 6