Document MGYaXnZvJMDdjw7pZm4QnZ3Nz

408 0. A. SANDER progression of the disease. They use four categories, the first three of,* distinguished chiefly on the basis of the size and extent of the shadotvl last of which indicates the presence of thoracic distortion and emphysema Categories oj Complicated Pneumoconiosis J| Category A. Shadows occupying at least one anterior rib space, formed by the coalescence of more or less circular shadows, more thanijj diameter, with indefinite margins and of uneven density. i'll Category B. Dense shadows, which are more extensive, better defin of more homogeneous density than Category A, but which extend overall three anterior rib spaces. 4S Category C. The same type of shadow as in Category B, extetfMMB more than three anterior rib spaces. `'$111111 Category D. One of the preceding classes of shadows associated TOtMBM distortion of the pulmonary architecture. 8l||||| In the early stages of progressive massive fibrosis, the backgroundfof||1r| pneumoconiosis always can be seen, but as the shadows gTow in e||f||f||| particularly as emphysema develops, the underlying simple pneumocoi|w^^S become completely obscured. Such cases are rare, however, the vast showing evidence of nodulation even after emphysema occurs. The validity of Category 1 has been questioned in this country''b;fc^Ml head shadows can be seen in the chest films of many persons whomever dust_exppsure,,in_in.dusky..lt.has.-appeared-to.many-thatrthis-wasHhc `ttfgtw the late Dr. Homer Sampson liked to call the "Stage of has justified it with controlled studies using seven film readers who hadilurtlM experience in this field. He emphasizes that persons so classified never .area abled. It should be noted also that the Silicosis Board of England doei'-riqg^^ applications for compensation of miners having only a Category 1 rhi^fm8| Gough100 and Heppleston have shown that the pinhead shadowS;"arc||j to focal collections of coal pigment in the peribronchiolar lymphatit'S'^reierr to as coal macules. The mixed type appears to be due to a combiriatii'n^o^ro macules and small silicotic nodules, while the nodular type usuallv'T^uffig d--e--f-i-n-i-te- nodular usinlicwoesilsl.. AInil tohne complicated groups, tnhe ccoonnffluideenntJts-ihljaagdkraf^ .^dfuice.tct.LnEnIr2ngclr6reSn8aixivoL.minoaosasniK//.e-#f1ib1.r.o...s-:i.s, ,--wvhii-Gi-h--i-s-athi--o--u--g1h1t-t1 o-b1e'--tl*i'e!-re'|uii^ofJTl^ bined effect|fcif,;thei't'nbercle bacillus and the coal dust.-Fletcher thmkiwotfl'" aass mmooddiiffyyiinngg ttuiilbieefrccuulloouuss iinnffeeccttiioonn tton tthhe extent +th*at --ma--n--y- --m---in--e--r4s"'6vi fpiildgSljRj died of tuberculosis had they not had coal-dust exposure. It isw'notcwu^ytfr the tuberculosis mortality always has been lower among-,c.qa.ljniaI:fs`Jliau^iufiCi a-H-occupied;"arrd'THth'gd"7nen in Britain. THe~theory that all pro'gfessi've^ii^ fibrosis in coal miners is a modified tuberculosis is strongly sdfportVvliby evidence, but is unproved. -1 .11 ,4j s' i'1^ PULMONARY DUST DISEASES 409 mfeiuQpSBSgJ;md Heppleston108'104 also have shown that a focal type of emphysema ^Bcfcristic finding in coal workers' lungs. At first thiB emphysema was ^hklueto a dilatation of the alveoli immediately adjacent to the coal nJNlpre,detailed recent studies suggest, however, that it is essentially a iSf-fviie'-respiratory bronchioles and that the alveoli are relatively normal. ^^Sesis of the bronchiolar dilation is thought to be a direct effect of the the smooth muscle in the walls of the bronchioles. When such lllplimieB extensive, increase in the dead air space is thought to. impair n||||$py;- capacity of the lungs to the extent where exertion produces ^^^|pt of disabling emphysema is in sharp contrast to that which has ^^Sffija'ccepted in this country. Most disabling emphysema is thought iuffjiopbstruction of the bronchial and bronchiolar airways. Lung funcjp^aiiiijthe beneficial effect of bronchodilator aersol therapy by Motley105 Sffig|prongly suggest that airway obstruction is the principal cause of emphysema. It appears likely that even though there may be a _J||||digree of focal emphysema in a simple pneumoconiosis case, there must ^jflfrpnib'bronchial obstruction to produce breathlessness. As a matter of ,^!?ocht^F!er,-cher and Hugh-Jones have repeatedly stated that miners with iMnncunidconiosis have little or no measurable impairment of lung function ffi^^^effactor is taken into consideration, but workers with progressive veSeSfibrosis may be severely disabled. Death rates from all causes among ^^mmers"im-Wales-showed-that-cases.-of ..simple.pneumoconiosis, have the Sg6|EjS!liftyi rate as all men in England and Wales, while there is an increased ffi@iit^i-a.tc in those with massive fibrosis. This strongly suggests that focal jiflalo'ne- is not a factor in causing right heart strain. Present evidence p^^^mish-'Studies, therefore, seems to indicate that simple coal pneumoesis^i^'Jibc'jl 'emphysema are not physiologically significant unless markedly 'mci'H^Workers with minimal coal-dust deposits and-disabling emphysema 8*S^k^;>q:''separate entities which are .unrelated, and'bther causes for the fer^rmm'be looked for. Im*"stc.hsaiMw.-c*' joj untry there never has been an industry-wide survey in bituminous J^^nT'i'of^the study in a Utah mine by the United States Public Health M^ui|l19.j:]r!0,1'l'This*showed*-a-l0waincidenoe of. airiferaecifiio'oai8''<,'Miper'centl no evidence of any significant degree of emphysema. The fj'|rf-Mnierican studies have been made on miners who think they have dis- ifiEefplekon, The pathological anatomy of simple pneumokoniosis.-ih coal workers, .,M'fmii^66fc,23&r246. U953),. st0> ^ be patnogeneeis ol siHIple''pneumokonio3iB-rn'-coai-workerS7-J--PothoI_ (1954) lev, L. P. Lang, and B. Gordon, Use of intermittent positive pressure breathQmjh^nebulization in pulmonary disease. Am. J. Med., 5, 858^856 (1948). H.' E. Seifert, H. P. Brinton, el al.. Soft coal miners' health and working'' Health Bull. No. 270, 1941. (