Dead space (physiology)

The dead space is the space of the respiratory system, which is not involved in pulmonary gas exchange, however, the propagation of the inspired gas mixture used. The dead space serves some fundamentally important conditioning processes during inspiration (breathing in ). Then the inhaled air is heated to a physiological temperature in the dead space at the same time the inspired air was saturated with water, so that a relative humidity of 100% is achieved. There are two different types of dead spaces:

Anatomical dead space

For anatomical dead space include the nose or the mouth, the throat, the trachea and the bronchi. In them remains per breath about 30% (about 0.15 l) of the inspired air. The anatomical dead space can be further increased by the airway is extended by a snorkel or tube, for example. When a tracheostomy after laryngectomy, however, the dead space volume is lowered.

Functional dead space

As functional dead space is defined as the sum of the anatomical dead space, and the regions of the lung ( physiological dead space) which is not supplied with blood or are no longer in a position by damage to, the exchange of oxygen in the blood (and vice versa of CO2 in the exhaled air ) participate. In healthy vote of functional and anatomic dead space are largely the same as usually all areas of the lungs in gas exchange. Classically, it comes as part of a pulmonary embolism in an increase in functional dead space because lung sections are behind the closure ( pulmonary artery or branches) while still ventilated but not perfused.

Size of the dead space

Calculating the size of the dead space is possible by means of the drilling formula:

Denote the fact

  • The partial pressure of the air sacs ( alveoli )
  • The partial pressure of the exhaled air,
  • The tidal volume, so the volume stroke each breath, with an average human, this value is about 0.5 liters, as well as with
  • The volume of the dead space (english dead space ).

Example calculation:

  • Breathing
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