Dead space

Examples of Dead space in the following topics:

• Pressure Changes During Pulmonary Ventilation

  • It is defined as $VA=(Tidal Volume-Dead Space Volume)* Respiratory Rate$
  • It is defined as $VD=DeadSpaceVolume*Respiratory Rate$.
  • This is most apparent in changes of the dead space volume.
  • Breathing through a snorkeling tube and having a pulmonary embolism both increase the amount of dead space volume (through anatomical versus alveolar dead space respectively), which will reduce alveolar ventilation.
  • Differentiate among the types of pulmonary ventilation: minute, alveolar, dead space

• Functional Anatomy of the Respiratory System

  • It is defined as tidal volume minus dead space (the space in the lungs where gas exchange does not occur) times the respiratory rate.
  • Dead Space Ventilation (VD): The amount of air per unit of time that doesn't reach the alveoli.
  • It is defined as volume of dead space times the respiratory rate.
  • Dead space is any space that isn't involved in alveolar gas exchange itself, and it typically refers to parts of the lungs that are conducting zones for air, such as the trachea and bronchioles.
  • Feedback mechanisms increase the ventilation rate in such a case, but if dead space becomes too great, they won't be able to counteract the effect.

• Alveoli

  • The alveoli consist of an extremely thin epithelial layer and an extracellular matrix (a fluid space made of collagen and elastin that contains no cells); it is surrounded by many capillaries, the tiniest type of blood vessel.
  • The alveoli are the site of alveolar ventilation, and are not normally considered dead space.
  • However, alveoli that are injured and can no longer contribute to gas exchange become alveolar dead space.
  • Physiological dead space is the sum of normal anatomical dead space and alveolar dead space, and can be used to determine the rate of ventilation (gas exchange) in the lungs.
  • When any type of dead space increases, the rate of ventilation in the lungs will decrease.

• Trachea

  • The trachea is also considered a part of normal anatomical dead space (space in the airway that isn't involved in alveolar gas exchange) and its volume contributes to calculations of ventilation and physiological (total) dead space.
  • It is not considered alveolar dead space, a term that refers to alveoli that don't partake in gas exchange due to damage or lack of blood supply.

• Bronchi and Subdivisions

  • The bronchi and bronchioles are considered anatomical dead space, like the trachea and upper respiratory tract, because no gas exchange takes place within this zone.
  • Like the trachea, the bronchi and bronchioles are part of the conducting zone, so they moisten and warm air and contribute to the volume of anatomical dead space.

• Blood Supply to the Lungs

  • This results in an increase in aveolar dead space and decreased perfusion, (leading to shortness of breath and chest pain) and can be fatal if not treated in time by fibrinolytics (medications that dissolve the clot).

• Chemoreceptor Regulation of Breathing

  • A more detailed example would be that if a person breathes through a long tube (such as a snorkeling mask) and has increased amounts of dead space, feedback will increase ventilation.

• Lungs

  • The pleural cavity is the fluid-filled space between the parietal and visceral pleura, and provides room for the lung to expand during inhalation.
  • Too low perfusion (and a higher ratio) indicates alveolar dead space, while too low ventilation (and a lower ratio) indicates a shunt, which is a lack of air supply relative to perfusion.

• Dystocia and Cesarean Section

  • A cesarean section is a surgical procedure in which one or more incisions are made through a mother's abdomen (laparotomy) and uterus (hysterotomy) to deliver one or more babies; or, rarely, to remove a dead fetus.
  • The classical incision involves a midline longitudinal cut in the uterus, which allows a larger space to deliver the baby.

• Distribution of Lymphatic Vessels

  • This fluid is mainly water from plasma that leaks into the intersitial space in the tissues due to pressure forces exerted by capillaries (hydrostatic pressure) or through osmotic forces from proteins (osmotic pressure).
  • When the pressure for interstitial fluid in the interstitial space becomes large enough it leaks into lymph capillaries, which are the site for lymph fluid collection.
  • In comparison to cardiovascular capillaries, lymphatic capillaries are larger, distributed throughout connective tissues, and are also "blinded", meaning that they have a dead end which completely prevents backward flow of lymph.