Document 8OQ3O8GNd1gE9qRMj75VnnQ8e

390 O. A. SANDER oxygen uptake during step-up exercise and (6) the character and duration of dysggg step-up exercise. In another study Motley64 concludes that spirography provides aitre; amount of information on the status of the individual's lungs. He%| impairment of oxygen transport across the pulmonary membrane ma, _ in some .cases with essentially normal spirographic tracings, but the'peifl this group is very low. He concludes that: 1. Spirogram tracings of the three-second timed vital capacity and the ma;*xim'<Wa] capacity have been found: (1) useful screening tests of pulmonary functiofi'iiowc lung function abnormalities even before subjective or roentgenologic changhe:S?I| and (2) suitable tests for annual or pre-employment examinations to detect eusceguB risk individuals who may be exposed to environmental lung irritants in theipiwtii] spirograms are cheap .to run, rapid in measurement (five minutes), and easy^anfi. obtain for permanent records. 3. The reliability of the spirogram data has been' weBfll. with complete pulmonary function studies on a large series of cases with all d'ej$fe|j monary function impairment, and a wide spread of values has been shown betwee and the most abnormal. 4. If the observed measurements of either the three-secohdf capacity or the maximal breathing capacity are reduced more than 15% fromithi the subject should be studied and evaluated further before being allowed furthe|| environmental breathing hazards. "'rilL Motley, Gordon, Lang and Theodos," in studying the impairmlnl monary function in anthracosilicosis, stress the importance of emphpeS. disabling mechanism in this disease. They point out that as the ratifi|8| air to total capacity increases, the maximum breathing capacitvi'andf capacity decrease. They note sharp decrease in the oxygen saturati$l||L blood with mild exercise and feel that this is a very significant mei|^M the evaluation of disability indicating a disproportion between ven|||f perfusion ratios when the consumption of oxygen is increasedsiby|||j|| emphasize that respiratory gas exchange may be normal at rest andi|^ nificant abnormality during exercise. In approximately 30 per C.eptg studied, residual air percentage of total lung volume was withini&cmffil They felt that the dysfunction present in these cases was due to po'bifSil|. that is, inequality between well-ventilated alveoli and perfused!;flvlo|j was no apparent correlation between the roentgenographic stage brsijjfi^ degree of impairment of pu1monary function in many casesKTliev-iSMcl "an accurate,evafijation^oftbe degree of impairment bf'puliBpr^^^ quires a 'bhtter|p)f pflmonaty function; tests1; anW.the.y condf^^^S single test io appraise all cases. This opinion is shared by Comrogd^Ml "there is no single lest by which all aspects of pulmonary function$cah7l>^YttUj -atcidiandtnormffghjmumbemwMch-serves-as^a-^shar-p-defined^iiTie-UctwIyfiiVjpre and pulmonary disability." ,' The expression of residual capacity as a percentage of lotal lung leaping must be interpreted with reference to age. Greifenstein et al.b> have =howWuT ** F. E. Greifenstein, R. M. King, S. S. Latch, and J. H. Comroe J djjyd Ml (1962). . , PULMONARY DUST DISEASES 391 fgwygnpt independent of age, there being a considerable rise in the percentage 'healthy subjects. Gilson and Oldham59 showed normal males,, age jnl|le. average a ratio 12 per cent greater than men age 25. They felt that p&.;changes in normal individuals that are the same as those that occur ^fpSa. They also point out the difficulty of using an absolute ratio in Ippeumoconiosis of the massive fibrotic type where the increased ratio jBfdue to a fall in the vital capacity, the absolute value of the residual Bffijj&&1*S6-on the average smaller than in normal subjects. Motley,50 using S6^ute?;fal;ip of 35 or above as indicative of emphysema, feels that emphysema ^(SnM^iiy.lanj.'RC to TC ratio of over 35) "does not appear to be any more a luralfip'ht'fof the aging process than is hypertension. Many individuals have ^aTyen'Shypertension without complaints over a period of years while actively vq* llheir blood pressure is not considered normal; and the same may be mphysema, because individuals may have residual volumes of 45 per .......... ^ 'ore:of total lung volume without complaints, but this increased residual sflumnei'iLsiuibi'dnp^r.mfa5l 0anmdednowesitrhepsrielisceonstise/mpthheysdeemgareien omf oesmt pehryssoenmsa." as expressed fjlffeiS^WtTM'*i"h-i*`o.i-V''o>oUiv.:rfe\tsiduaml ocnapTairic+ Viti yctiloirtro\ctioal00ca+,pVloacHiptycrrwppasoffoPuTnTdinhtvoSPvTaYIrfty. fwithout any ypu^con'elaition to the stage of silicosis. The maximum breathing capacity also Mn^fghificant difference between the three stages of silicosis, mean values "*^jtp~||or Stage I; 50 for Stage II; and 45 for Stage III. Pelnar10 proposed sbwfeven|ilatory equivalents for oxygen and carbon dioxide simultaneously mrftrftiiw, upd recovery as a basis for disability evaluation |if&S|dl?.work is predicated upon the principle that people with pulmonary SMWSiscas6 are unable to utilize inspired air properly even at rest. Dur- v'it'l?ey are able to improve the utilization of air only poorly or not at ^^Kil-ffiSing the technique of Pelnar on 100 miners,-found no correlation ^ei^cliti jatory equivalents and over-all impairment of'pulmonary function. ftpWifent from the above review of current work-that determination of ,jimStfici:isi8 through the use of function tests is noW1 simple matter. No ag]^le?ti^iiclequate and the problem of the significance^' of 'minimal functional ^Kip^ircmams unanswered. It is also apparent that the area of normal has defined. One must deal not with a razor's edge, But with a u(liy;:0fi^^y! differing individuals.49 For example, the normal'man' can be his predicted normal by as much as 35 per cent. Thus a j^^^^Kimal.breathing capacity is 35 per cent below the'.pfedicted n'or- ^JiTvG^rgTThe'cHnrcahevaluation-of-Klisability-in-siUcoaii^^cio^lfe^iScdrui^- ^^^feb'aipnent of pulmonary function in anthracosilicosis, Arch, .lnd. Hyg. and S2$J2* 6. 532 (1952). . "C. M. Fletcher, J. C. Gilson, and P. Hugh-Jones, The role of periodic' nnuil lan'.ihilhetprevention of coalworkers' pneumoconiosis, Brit. J. Ind. Med.. 8, 534)1 v.&iif. 1