Document oDzvwk6r117n6ELmGJk6MxYmo

386 0. A. SANDEB roentgenographic changes present? Does he have complicating tubeffjflljl other infection? Is he incapacitated or disabled 'by his condition? Theip|l these questions are usually answered by the examining physician. The'J-reara lem is the third question. Is the man disabled? An incorrect ansWeVwiiilgj injustice to employee or employer. In the past, attempts to solve problem in silicosis were based chiefly upon the clinical approach and|i^n graphic studies. For obvious reasons, clinical appraisal of a given pulmonary disability is limited to objective signs and principally tp'Tli!)sewa1 at rest and during the performance of exercise tests. Roentgenographic^sum? addition to determining the stage or extent of disease, were used to?!Sec^^^ presence or absence of emphysema. Currently, physicians are eageily accepl the objective assistance offered by pulmonary function .tests. The us#o`f|t^^ accurate aids must be accompanied by knowledge of their limitatibhsfP'nl^ major unsolved problems is the degree of dysfunction beyond which allvfmjMcn will be disabled. Do individuals with simple nodular silicosis have mdre^oi^ffl emphysema than persons in the general population without silicosis^ftE^fflji that satisfactory answers must await lung function testing of largeVgnn^nS people with and without silicosis. b. Pathologic Physiology and General Principles. Based upon rec.enmgy cant studies,49-62 the following simple classification of the types offpiifttforfSTSl sufficiency is useful: (?) ventilatory pulmonary insufficiency, whichf^i^^^OT with defective air movement into and out of the lungs; (2) distribii|i'^^^ w-hich-is-coneerned--with-al-veolar--yentilation-and-perfusion--re'MWSmpf diffusion difficulty, which is concerned with passage of carbon dioxide between capillary and alveolus; (4) circulatory insufficiency, whicil;]0, with reduction in the absolute size and distensibility of the bed. Ventilatory insufficiency.58 Silicosis may interfere with pultn^iirl&peuin tion in several ways. By simple proliferation, it may encroach uponfl would normally be occupied by functioning lung tissue. Fibrous fajBwreih^i|mM goes shrinkage may give rise to overdistension of adjacent norm'fifciu^^TOi The degree to which the involved portions of the lung can be expandSSjpijjj limited. It is possible that by suitable location it may also limit 'tff^exp^^M -of-interposedlnoEmat-'lung-tissuev-There-may-be-inteffdreirc^nul'hHni^S^H " fright; Disability evaluation in industrial pulmonary diseas.1e/,5 J'Am '1$ftgr7By.UHK 141, 1^18-1^22* (19) :"J " Mb'tley, The use of pulmonary function tests for disability evaluation rt|ndar^m^ronmpn|mu.ary 4ise_MeJ Djseases of the Coumand, Clinical and physiologic features of some types of pulmonary diseases ment of alveolar-capillary diffusion, Am. J. Med., 11, 667-685 (1951). "'''`.'fflpi "K, L. Riley, Pulmonary gas exchange, Am. J. Med., 10, 210-219 (19311 "G. W. Wright and G. F. Filley, Pulmonary fibrosis and respiratory-,fum-tibu^SyTfi Med., io, 642 (1951). jilt t'/vVfy PXILMONAEY OUST DISEASES 387 SgBBEjjfe -degree to which airways are enlarged both as to diameter and inspiratory phase of respiration. There may be narrowing of PffiirWf*the -smaller airways of a spastic50 or permanent type such as to ^^^^gi|htory obstruction with the development of the characteristic pattern ^ffl|S|le)emphysema. These abnormalities are evidenced by reduction of total maximum breathing capacity. ^ma^mn-^'difficulty. Silicosis may interfere with even distribution of ||pi|_am6ng the millions of lung alveoli by:54 m^j^^M-imitation'of lung distensibility. Obstruction of air passages either by spasm50 or fibrosis. of elasticity. ^^^i|^|l)ution results in overventilation of some alveoli and underventila- ^^^^may affect the distribution of venous blood among the capillaries S^intpired air among the alveoli. This concept visualizes the distribution Kisjhd^ing-blood and gas components.52-55 Uneven blood distribution results some alveoli and underperfusion of others. Effective shunting fffi^i^tery blood away from diseased and improperly functioning alveoli ^^^^M^'functioning ones may act as a beneficial compensatory mechaffi^'rriportance of this phenomenon has been inadequately appreciated.58 EccTnufiUL-s-' suitable for analyzing the relationship of volume and speed of olaiveolar size and ventilation have not as yet been fully explored.58 ^^^^ii^-ewEtyv-I-n-add:iti0B-tG-distuEbances..in_the.ability..oLthe respira- raaratust-'tb'.move air into and~ out of- th* e l'ungs, t h1 ere is evid.1e--n----c---e--K410'5A1_ to ^^ffliBihe cases of silicosis there may be interference with the direct 'rjjtteii'x vgeii' and carbon dioxide between the blood and the alveolus. ProTOMofifM|connective tissue supporting the alveolar vascular bed may not tlie-'distance that must be traversed by each..molecule of gas but M&cfflS^^ghe character of the medium. Under theseicircumstances (alveo- . even though the pressures of oxygen*and carbon dioxide ^'(fl^in^.tRe alveoli may be normal, the venous blood brought to the completely oxygenated. Since carbon .^jpjude passes through g^'ljnuim'd^a^y'membrane easier than oxygen, the transfer of oxygen will ^S|^liei'and*to:-ar-greater'extent4than..that.:o:.:caiilB:Qn;idiQ3ddgI5!:!?.'.Jt is remember .that the effect of a localized diffusion difficulty may nTnized'-ior'-nullified if there are enough other areas of normal functioning mfly be shunted.58-54 g,cigncp.._In the normal .individual the pulmonary circula7^^"hV'lbw-nreR8urR (2r/9rtHd-nxte'em^istensifirHty^It- ^^^ilnterpretation of commonly used pulmonary function tests, Am. J. Med., ;CB. Gordon, L. P. Lang, and P. A. Theodos, Impairment of pulmonary.-' ilieosia, Arch. Ind. Hyg. and Occupational Med., 1, 133-159 (1950). mife b-