By Ray Wright, Advanced Medical Engineering · 2026-08-17
Medical surveillance spirometry on South African mines: a report the medical officer can defend
On a mine, a spirometry result is not a number for today. It is one point on a line that will be read at the exit medical, in a compensation claim and possibly in an inquiry years later. This article is about producing that point so it still holds up then.
Where spirometry sits in the mine surveillance cycle
The Mine Health and Safety Act (29 of 1996) requires an occupational-hygiene programme that identifies exposure and a medical-surveillance programme matched to it, run under a designated occupational medical practitioner. For respiratory hazards (silica dust, coal dust, platinum-group and other metal dusts, diesel particulate, welding fume) the medical side is built around three examinations:
- Initial (baseline) before exposure begins: the reference against which every later test is judged. If the baseline is a grade-E session, every later comparison is weakened.
- Periodic at the frequency the risk assessment sets, typically annually for dust-exposed workers: looking for a decline in FEV1 or FVC beyond what age explains, and for a new obstructive or restrictive pattern.
- Exit when the worker leaves: the record that travels with the worker into the compensation system and must be kept for decades.
Spirometry is only one part of the lung-health picture next to chest radiography and clinical history, but it is the part that is most sensitive to how it was done on the day. That is why the quality of the recording matters more here than in almost any other setting.
What makes a lung-function record defensible
| Element | Why it matters years later |
|---|---|
| All efforts, not just the best values | A reviewer needs to see the flow-volume and volume-time curves of every blow, with the acceptability flags. Best-values-only reports cannot be re-graded. |
| ATS/ERS 2019 session grade (A to F) | The grade says how much the numbers can be trusted. A grade on the header stops a poor session being treated as evidence of decline. |
| Reference equations named | GLI-2012 or GLI Global 2022, stated on the page. Percent-predicted without the equation named is not reproducible. |
| Calibration record for that day | The 3-litre syringe check with pass/fail and the ambient conditions used for BTPS. An inquiry will ask whether the instrument was checked that morning. |
| Operator and device identity | Who ran the test, on which sensor, with which software version. Reports should carry it automatically. |
| Comparison with baseline | The change since baseline in litres and in z-score, not only the absolute value, so a real decline is visible and an artefact is not mistaken for one. |
| Exportable and durable | PDF for the file, CSV for the occupational-health system, stored locally and backed up. Reports locked inside one vendor's cloud are a risk to the record. |
Reading decline correctly
Healthy adults lose FEV1 slowly with age. A worker whose FEV1 z-score is falling faster than the reference population, or who has crossed the lower limit of normal since baseline, is the person the programme exists to find. Two things defeat that reading: poor sessions (which look like decline) and changing reference equations between years (which shift the percent-predicted without the lungs changing). Fix both by grading every session and by keeping the equation constant, or by comparing z-scores computed under the same equation across years.
Silicosis and coal-dust programmes
Silica exposure produces a mainly restrictive or mixed pattern late in the disease; spirometry is not a screening test for early silicosis, radiography is. What spirometry adds is the functional record: whether the worker's ventilatory capacity is falling, whether an obstructive component (often smoking-related, sometimes dust-related) is present, and whether the worker remains fit for the job's physical demands. In the coal sector the same applies for coal workers' pneumoconiosis and chronic bronchitis. In both, the value of the test is realised at the exit examination and in the compensation process, which is why record quality is the whole game.
Practical points for the mine clinic
- Book spirometry before shift, not after: fatigue and dust exposure during the shift depress results.
- Withhold bronchodilators as protocol requires and record it; record smoking, TB history and HIV status where the programme captures them, because they change interpretation.
- Use single-use filters and mouthpieces; TB prevalence makes this non-negotiable.
- Do the 3-litre calibration check every morning and print the certificate monthly for the file.
- Aim for grade A or B sessions; repeat rather than sign a grade-E result as evidence of change.
- Assume the network will fail. Software must complete the test and store the record with no connection.
How SpiroWright is built for this
SpiroWright stores every effort with its curves and ATS/ERS 2019 flags, prints the A to F session grade on the report, names the reference equation (GLI-2012 or race-neutral GLI Global 2022) with z-scores and LLN, logs the daily 3-litre and motor calibration with a verdict and printable certificate, compares against baseline and history, exports one-page and full reports as HTML, PDF, PNG and CSV, records HIV, TB and pack-year fields, and runs offline-first on any Windows laptop. Pricing is per test with no licence, which suits surveillance volume: see pricing in rands and the occupational-health page.
This article describes good practice and the structure of the MHSA framework in general terms. Codes of practice, mandatory frequencies and reporting requirements are set per mine by the risk assessment and the relevant regulations and guidance; the mine's occupational medical practitioner is the authority on the programme.
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