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Physiology

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Respiration

Question
4 out of 15
 

Physiological dead space is increased by all except (AIIMS MAY 2009)



A Artificial airway
B Neck extension

C Upright position
D Ipratropium

Ans. A

a. Since gaseous exchange in the respiratory system occurs only in the terminal portions of the airways, the gas that occupies the rest of the respiratory system is not available for gas exchange with pulmonary capillary blood this volume is called as anatomic dead space (150ml) Q.

b. When alveolar dead space (i.e.all the air in the alveoli that is not participating in gas exchange) is included in the total measurement of dead space, this is called the physiologic dead spaceQ, in contradistinction to the anatomic dead space.

c. In a normal person, the anatomic and physiologic dead spaces are nearly equal because all alveoli are functional in the normal lung. Q

Dead space is decreased by

  1. supine postionQ
  1. neck fully flexedQwith depressed chin
  1. low lung volumesQ
  1. TracheostomyQ&endotracheal intubationQ(Artificial airway).

Dead space increased by

  1. endotracheal intubation with tubeQ(increased mechanical DS due to tube volume)
  1. standing positionQ (due to hypoperfusion of apical alveoli)
  1. emphysema Q
  1. neck extension Q
  1. Ipratropium (Bronchodilation)

So we can see that only artificial airway (considering only tracheostomy&endotracheal intubationno tube which will add mechanical Dead space) involves decrease in the Physiological dead space
Note: Depression of the jaw with flexion of the neck produced a mean decrease in the dead space of 31.4 ml while a protrusion of the jaw with extension of the neck increases the dead space by 39.7 ml.

Respiration Flashcard List

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