This may not be the right forum but I bet there are people reading this who are expert.
Regarding health Surveillance for welders and COPD.
Any views on what would constitute a concerning fall in spirometric function?
I plot FEV 1, FVC and FEV1/FVC serially and see people on a downward trend and obviously those that meet the diagnostic criteria for COPD.
It's those on a downward trend I'd like to put some more concrete guidance to. What is a normal age related drop off? What is a suitable sensitive and specific level to use as a warning? I find there isa presumably technique /efort related variation anyway whcih we are working to try to improve.
We needn't get into the debate about does welding really cause COPD or is it only in welders who smoke for now unless anyone is keen.
Occupational Asthma, Specialist, 9/13/2012, 9/8/2017,

As a general rule you need to see a drop in FEV1 of at least 400ml before you can be reasonably sure that the fall is outside the 95% CI for normal workers, the drop can be over 1-5 years, the annual decline required falls with longer follow-up. The best way of validly doing this is to use the Spirola program (free from NIOSH, links in the experts section of this website). Welders may get occupational asthma as well as COPD, it is worth asking about rst-day improvement, if present serial occupational asthma type pef measurements should be done as well (the cause may be chrome for instance in stainless steel welders, but other welders also get occupational asthma).
Abstract Available for The precision of longitudinal lung function measurements: monitoring and interpretation Hnizdo E, Yu L, Freyder L, Attfield M, Lefante J, Glindmeyer HW, The precision of longitudinal lung function measurements: monitoring and interpretation, Occup Environ Med, 2005;62:695-701,
Eva Hnizdo, NIOSH, an author of 'The precision of longitudinal lung function measurements: monitoring and interpretation'

Spirometry Longitudinal Data Analysis (SPIROLA)
Free program to analyse longitudinal spirometry for individuals and groups. Identifies at risk individuals and measures the precision of the data. Very useful for Health Surveillance. Based on published research by Eva Hnizdo et Al.

The "Spirometry Longitudinal Data Analysis (SPIROLA)" link above can be used to download the program that plots fev1 decline and works out whether it is abnormal. The reference above details the method that the program uses.

In a nonsmoker, FEV1 decline rate is approx 30mL/yr. Hankinson's study also shows that the average caucasian male declines faster (+7ml/yr from age 40-80 years) compared to black american males. In smoking populations the FEV1 declines at a rate of about 60mL/yr approx. About 20% of the smokers have rapid decline of 100mL/yr and more. ADV.

Fletcher C, Peto R, Tinker C, Speizer FE. The natural history of chronic bronchitis and emphysema. Oxford: Oxford University Press; 1976.

Hankinson JL, Odenkrantz JR, Fedan KB. Spirometric reference values from a sample of the general U.S. population. Am J Respir Crit Care Med 1999;159:179–87.


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