Elderly subjects
The largest study of elderly subjects is probably that of Enright et al. (reference below). The table below lists the predicted values and 5th percentile in that study and those using regression equations applied in the present study.
| predicted | 5th percentile | |||||||||
| Enright | this study | Enright | this study | |||||||
| FEV1%FVC | 65 yr | 85 yr | 65 yr | 85 yr | 65 yr | 85 yr | 65 yr | 85 yr | ||
| male | 74.7 | 68.8 | 75.5 | 71.9 | 63.0 | 57.1 | 63.6 | 60.0 | ||
| female | 76.6 | 71.7 | 76.8 | 73.0 | 67.3 | 62.4 | 64.6 | 60.8 | ||
| FVC (L) | ||||||||||
| male 178 cm | 4.38 | 3.97 | 4.64 | 4.07 | 3.26 | 2.85 | 3.57 | 3.00 | ||
| female 168 cm | 3.29 | 2.63 | 3.90 | 3.31 | 2.65 | 1.99 | 3.16 | 2.57 | ||
| FEV1 (L) | ||||||||||
| male 178 cm | 3.24 | 2.69 | 3.54 | 2.91 | 2.40 | 1.85 | 2.68 | 2.05 | ||
| female 168 cm | 2.52 | 1.87 | 2.60 | 2.06 | 2.04 | 1.39 | 1.95 | 1.41 | ||
There is little difference in the lower 5th percentiles for FEV1%FVC. Mild airway obstruction tends to be found slightly earlier in elderly women when using the criteria of Enright c.s.
The predicted FVC in males and females, and the FEV1 in males, is higher with the present prediction equations
than with those due to Enright et al. The difference
also holds for the lower limits (5th percentiles).
By using FEV1%FVC rather
than FEV1 in assessing
the severity of airway obstruction, one is relatively insensitive
to the choice of reference values. When applied to the populations
studied by Enright et al., with the exception of
FEV1 in females, the
system adopted in the SpirXpertsoftware tends
to identify more people with a low FEV1 or FVC.
Study
of elderly subjects:
Enright PL, Kronmal RA, Higgins M,
Schenker M, Haponik EF. Spirometry reference values for
women and men 65-85 years of age. Cardiovascular Health
Study. Am Rev Respir Dis 1993; 147: 125-133.