Question

1. why choking person can be helped by pushing on the chest?
2. why does a negative pleural pressure cause alveoli to expand?

Answer 1

1. Choking happens when a foreign object such as food lodges in the throat or windpipe (trachea), blocking the air flow.

Pushing on chest or abdominal thrust lift the diaphragm. As a result, a forcefull flow of air from the lungs occurs that create an artificial cough. It helps move air through the windpipe, pushing, and expelling the foreign object out of the windpipe.

2. Pleural membranes are the membranes that cover the lungs. Alveoli are the air sacs present in lungs. When we inhale, air from atmosphere is filled in the lung alveoli.

Firstly, we have to understand that air passively moves from the region of high pressure to the region of low pressure.

During inspiration, due to the contraction of diaphragm and external intercostal muscles (muscles found between ribs), thoracic volume increases.

Increase in thoracic volume causes a decrease in pleural pressure. Thus it creates a negative pressure in pleura. So, lung alveoli try to expand. Thus, pulmonary volume increases resulting in decrease of intra-pulmonary pressure to less than the atmospheric pressure. So, air moves into lungs.