Question

Bill laid on his back sunbathing. Describe how his body posture/position affect his respiration in terms of (1) abdominal breathing (2) lung volume and (3) inspiration.

What forces are involved in passive expiration?

Answer 1

Body posture and respiration

Posture is the way a person holds and positions their body. Respiration is the process of inhaling an exhaling or is the act of breathing. Posture and breathing are related to each other as the bad posture hinders the normal breathing and good posture helps in maintaining a quality respiration.

Supine position ( laying on one's back) and breathing:

1. Abdominal breathing or diaphragmatic breathing : Abdominal breathing can be more easy with supine position. Diaphragm and other muscles of respiration contracts and lungs can expand during inspiration . Abdominal breathing related to exercise is mainly done with supine position or sitting position.

2. lung volume : Functional residual capacity ( FRC)decreases with supine position. Forced expiratory volume ( FEV) is slightly lower than sitting position. DLCO- Diffusing capacity of the lungs for Carbon monoxide is increases in supine position. There is an increase in alveolar blood volume on supine position.

3.inspiration : Upper airway resistance due to reduction in pharynx diameter ( in supine position) and increased intrathoracic blood volume contribute to decrease in FVC ( functional vital capacity) in supine position. Inspiration is easy in standing position than the supine position.

Forces involved in Passive expiration

Expiration is the act or process of breathing out. It is considered as a passive process. Forces involved in a passive expiration are:

* Diaphragm muscle relaxation, that contracted during inspiration, reduces dimensions of thoracic cavity.

* elastic recoil of the lungs,

* Muscles for passive respiration : relaxation of external intercostal muscles lead to depression of ribs and sternum, resulting in reduction of dimensions of thoracic cavity.

Increased pressure in the lungs, after inspiration, become higher than outside; as a result of pressure difference , air moves out of the lungs.( Boyle's law)