Lung function and clinical outcome in postpolio patients: a prospective cohort study during 11 years

The object of this investigation was to prospectively study the annual decline in lung function in a cohort of postpolio patients, and to determine the usefulness of initial lung function tests in the prediction of a subsequent poor outcome. Cross-sectional data were analysed in 55 patients from the total cohort of 350 survivors of poliomyelitis in our admission area of 550,000 inhabitants. Longitudinal data (> 5 yrs, average 8.9 yrs) were available for 31 patients. Seventeen of the patients had a poor outcome (13 were started on domiciliary artificial ventilation and five died from respiratory failure; with one overlap). At the time of entry to the study (on average 4.3 years before the poor outcome), these patients had a lower vital capacity (VC) (43 vs 65% of predicted; p < 0.01) and arterial oxygen tension (Pa,O2) (9.9 vs 11 kPa; p < 0.05) and a higher arterial carbon dioxide tension (Pa,CO2) (6.0 vs 5.0 kPa; p < 0.01). They also had a more rapid increase in Pa,CO2 (0.3 vs 0.03 kPa.yr-1; p < 0.01), but the difference in decline in VC (40 vs 30 mL.yr-1) was not significant. Initial VC < 50% of predicted and/or Pa,CO2 > 6 kPa was associated with a poor prognosis. In conclusion, annual decline in vital capacity was not abnormally rapid but annual increase in arterial carbon dioxide tension was higher in patients with a poor outcome. Initial determination of vital capacity and initial and repeated blood gas analysis appear to be useful in identifying high-risk postpolio patients.