47. RESPIRATORY DEAD SPACE: MAN 



For purposes of defining dead space, expiratory air is arbitrarily divided into two components: that which is like 

 alveolar air, and that --called dead space- -which is like the inspired air. Dead space can be considered for any 

 inspired or expired gas, CO^ being most often studied. There are many methods for measuring dead space, differ- 

 ing primarily with the way alveolar air is measured or computed. It has not been shown that any two methods give 

 identical results, nor is it known exactly which geometric portion of the lung they measure. Until identical results 

 can be shown, it is best that different methods be identified by different names. For CO2 and O^, dead space is sub- 

 divided by some into two parts; one, the conducting airway from nares to terminal bronchioles, the other, a portion 

 of the tidal volume going to alveoli but wasted because of uneven distribution of blood and gas in the lung. The terms 

 in most common use are: (1) Anatomic Dead Space . Strictly, this is the geometric volume of the conducting 

 airway. The term is used both by those making plaster or other casts of the dead lung airway; and by many whose 

 methods are thought to approximate this volume in vivo , the most widely used of which methods is Fowler's single- 

 breath analysis of gas flow and concentration ( l] . Other terms and methods believed to approximate this anatomic 

 space are grouped in this section under the heading Anatomic. (2) Physiologic Dead Space. This term includes 

 both anatomic and distribution dead space, and indicates the value of alveolar CO2 tension obtained by measuring 

 arterial CO2 tension. Other methods also attempt to include distribution dead space; these are all grouped with the 

 arterial CO^ tension methods under the heading Physiologic. Those marked "Haldane- Priestley" are now felt by 

 most investigators to be too large, because the alveolar tension obtained by a forced lung expiration is too high. 

 Regarding other methods, it is not possible to be certain whether they belong in the Anatomic or Physiologic group. 

 "Alveolar" dead space [ 2] is the difference between the physiologic dead space and the anatomic dead space 

 (Fowler); it is one measure of the distribution dead space. "Parallel" dead space also refers to the distribution 

 dead space, as determined by the isosaturation technique [ 3] . 



Contributor : Severinghaus, J. W. 



References : [ 1] Fowler, W. S., Am. J. Physiol. 154:405, 1948. [2] Severinghaus, .1. W., and Stufpel, M., J.Appl. 

 Physiol. 10:3 3 5, 1957. [3] Pappenheimer, J. R., Fishman, A. P., and Borrero. L. M., ibid 4:855. 1952. 



Part 1: AT REST 

 Values in parentheses conform to estimate "c" of the 95% range (cf Introduction). 



Anatomic 



Contributors : (a) Rossier, P. H., (b) Bateman, J. B.. (c) Fishman, A. P., (d) Kaltreider, N. L., (e) Severinghaus, 

 J. W. 



Reference s: [ l] Hatch, T., Cook, K. M., and Palm, P. E., J. Appl. Physiol. 5:341, 1953. [2] Fowler. W. S.. Am. 

 J. Physiol. 1^:405, 1948. [3) Siebeck, R.. Deut. Arch. klin. Med. |02:390. 1911. [4] Siebeck, R.. Scand. Arch. 

 Physiol. 25:86. 1911. [5] Fishman. A. P.. J. Clin. Invest. 33:469, 1954. [6] Tenney, S. M., and Miller. R. M.. J. 

 Appl. Physiol. 9:321. 1956. (7) DuBois. A. B.. Fowler, R. C, Soffer. A., and Fenn. W. O.. ibid 4:526. 1952. 

 [8] Pappenheimer, J. R., Fishman, A. P.. and Borrero. L. M.. ibid 4:855. 1952. [9] Krogh, A., and Lindhard. 

 J.. J. Physiol. 47:30, 1913-14. [10] Loewy. A., Pflugers Arch. 28:416. 1894. [U] Hurtado. A., Fray, W. W., 

 Kaltreider, N. L., and Brooks. W. D., J. Clin. Invest. 13:169, 1934. [12) Bateman. J. B.. J. Appl. Physiol. 3:143. 

 1950. [13] Birath, G., Acta med. scand., suppl.. 154. 1944. [14] Blickenstorfer, E.. Schweiz. Zschr. Tuberk.. 

 4:Buppl. 1, 1947. [15] Enghoff, H., Upsala lak. foren. forh. 44:191. 1938. (16) Haldane. J. S., and Priestley, 

 J. G.. J. Physiol. 32:240. 1905. [17] De Coster. A., and Denolin. H.. Acta clin. belg. 9:135. 1954. 



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