All of the following statement about a normal subject in the erect position are true EXCEPT
Correct Answer: Airway resistance is greater at the apex than at the base
Description: When the thorax is in the erect Position, the pressure generated by the right ventricle is not sufficient to perfuse apical alveoli to the same extent as it perfuses alveoli at the base of the lungs. Approximately IS times more blood flows through the capillaries at the base than at the apex. In addition, while erect, the more negative intrapleural pressure at the apex causes the overstretched alveoli in this region to resist further stretch more strongly; i.e., the compliance of the alveoli is less at the apex than at the base. Consequently, about four times more gas goes to the base than to the apex. Most of the gas exchange in the lungs takes place at the base when the thorax is erect because the base is the place where most of the blood and gas are located. However, there is too much blood for the amount of air at the base; that is, the base has a low ventilation/perfusion ratio (VAIQe). Conversely, there is too much air for the amount of blood at the apex; that is, the apex has a high VA/QC.
The more negative intrapleural pressure at the apex distends airways causing the resistance to flow to be lower at the apex than at the base.
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