Dead space

Jump to navigation Jump to search

WikiDoc Resources for Dead space

Articles

Most recent articles on Dead space

Most cited articles on Dead space

Review articles on Dead space

Articles on Dead space in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Dead space

Images of Dead space

Photos of Dead space

Podcasts & MP3s on Dead space

Videos on Dead space

Evidence Based Medicine

Cochrane Collaboration on Dead space

Bandolier on Dead space

TRIP on Dead space

Clinical Trials

Ongoing Trials on Dead space at Clinical Trials.gov

Trial results on Dead space

Clinical Trials on Dead space at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Dead space

NICE Guidance on Dead space

NHS PRODIGY Guidance

FDA on Dead space

CDC on Dead space

Books

Books on Dead space

News

Dead space in the news

Be alerted to news on Dead space

News trends on Dead space

Commentary

Blogs on Dead space

Definitions

Definitions of Dead space

Patient Resources / Community

Patient resources on Dead space

Discussion groups on Dead space

Patient Handouts on Dead space

Directions to Hospitals Treating Dead space

Risk calculators and risk factors for Dead space

Healthcare Provider Resources

Symptoms of Dead space

Causes & Risk Factors for Dead space

Diagnostic studies for Dead space

Treatment of Dead space

Continuing Medical Education (CME)

CME Programs on Dead space

International

Dead space en Espanol

Dead space en Francais

Business

Dead space in the Marketplace

Patents on Dead space

Experimental / Informatics

List of terms related to Dead space

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


Overview

In physiology, dead space is air that is inhaled by the body in breathing, but does not partake in gas exchange.

In adults, it is usually in the range of 150 mL.[1]

Understanding dead space

Not all the air we breathe in is able to be used for the exchange of oxygen and carbon dioxide. About a third of every resting breath is exhaled exactly as it came into the body.

Because of dead space, taking deep breaths more slowly (e.g. ten 500 mL breaths per minute) is more effective than taking shallow breaths quickly (e.g. twenty 250 mL breaths per minute). Although the amount of gas per minute is the same (5 L/min), a large proportion of the shallow breaths is dead space, and does not allow oxygen to get into the blood.

Dead space can be enlarged (and better envisaged) by breathing into a long tube. Even though one end of the tube is open to the air, when one inhales, it is mostly the carbon dioxide from expiration. Using a snorkel increases a diver's dead space in the airways.

Components

Dead space can be divided into two components: "anatomic" and "physiologic".[2]

Anatomical dead space

Anatomical dead space is the gas in the conducting areas of the respiratory system, such as the mouth and trachea, where the air doesn't come to the alveoli of the lungs.

It is normally equal in milliliters to your body weight in pounds. A 150 lb (68 kg) male would have an anatomical dead space of about 150 mL. 1 mL per lb or 2.2 mL per kilogram of body weight. This is the same conversion of kilograms to pounds, except the final unit is in mL. This is about a third of the resting tidal volume (450-500 mL).

Anatomic dead space is the volume of the conducting airways. It may be measured by Fowler's Method, a nitrogen washout technique.[3][4][5] It increases with an increase in tidal volume and is dependent on posture.

Physiological dead space

The physiological dead space is equal to the anatomical dead space plus the alveolar dead space.[6]

Alveolar dead space is the area in the alveoli that does get air to be exchanged, but there is not enough blood flowing through the capillaries for exchange to be effective.[7] It is normally very small (less than 5 mL) in healthy individuals. It can increase dramatically in some lung diseases.

Physiologic dead space can be measured by Bohr's method.[8][9]

An equation and example are provided below:

<math> V_\mathrm{D} = V_\mathrm{T} \,\frac{P_\mathrm{a\,CO_2}-P_\mathrm{E\,CO_2}}{P_\mathrm{a\,CO_2}} </math>
<math> V_\mathrm{D} = 0.5\,\frac{0.056-0.040}{0.056} = 0.143 \ \mathrm{L} </math>

See also

References

  1. http://www.ccmtutorials.com/rs/mv/strategy/page16.htm
  2. Essentials of Human Physiology by Thomas M. Nosek. Section 4/4ch3/s4ch3_16.
  3. http://www.med.mun.ca/surgery/presentations/LungVentilation/LungVentilation.htm#AnatomicDeadSpace
  4. Essentials of Human Physiology by Thomas M. Nosek. Section 4/4ch3/s4ch3_17.
  5. Heller H, Könen-Bergmann M, Schuster K (1999). "An algebraic solution to dead space determination according to Fowler's graphical method". Comput Biomed Res. 32 (2): 161–7. PMID 10337497.
  6. Essentials of Human Physiology by Thomas M. Nosek. Section 4/4ch3/s4ch3_18.
  7. Essentials of Human Physiology by Thomas M. Nosek. Section 4/4ch3/s4ch3_20.
  8. Essentials of Human Physiology by Thomas M. Nosek. Section 4/4ch3/s4ch3_18.
  9. Klocke R (2006). "Dead space: simplicity to complexity". J Appl Physiol. 100 (1): 1–2. PMID 16357075. article

External links


Template:WikiDoc Sources