Prediction of Normal Spirometric Values for Adults Incapable of Standing: Results

The data on height were first analyzed as the H/S ratio. The data for one man and two women were rejected because their ratios were greater than 3.8 standard deviations from the mean. The man and one woman had sitting heights within 1 SD of the sample means but were the shortest man and woman for standing height. This could indicate incomplete development of long bones. The remaining womans standing height was within 1 SD of the sample mean, but the sitting height was abnormally large. This would most likely result from an error in transcription. The statistics on physical characteristics were calculated for the remaining 103 men and 93 women and are summarized in Table 1.

The H/S ratio was tested for age dependence by fitting age and H/S to a simple linear regression equation and evaluating the age coefficients using a one-sample f-test. The resulting equations are as follows: for men,
H/S = 1.8846 + 0.00073A (1)
where the correlation coefficient (r) = 0.1612, and the standard error of the estimate (SEE) = 0.0492; and for women,
H/S = 1.8186 + 0.00135A (2)
where r = 0.2646, and SEE = 0.0518. The levels of significance (p value) for the slopes are 0.10 for men and 0.01 for women, with the upper level of significance equal to 0.05.
The standing height was then fitted into a multiple linear regression equation against age and sitting height. The resulting equations are as follows: for men,
H = 21.1492 – 0.0037A + 1.3459S (3)
where r = 0.7874, and SEE = 1.5723; and for women,
H = 19.7789 +0.0192A+ 1.2754S (4)
where r = 0.7759, and SEE = 1.5497.
The values for SEE were calculated from the residuals (differences between the observed and predicted standing heights in inches) of each method of prediction and are listed in Table 2. The predicted standing heights are calculated as follows: (1) sitting height is multiplied by the fixed ratio for the individuals sex (Table 1); (2) the H/S ratio is calculated by substituting the individuals age into the H/S regression equation (equation 1 or 2) for the individuals sex and solving for the ratio; the individuals standing height is then estimated by multiplying his or her sitting height by the H/S ratio; (3) the individuals age and sitting height are substituted into the regression equation (equation 3 or 4) appropriate for their sex, and the equation solved for standing height. The values for SEE (Table 2) indicate that the multiple regression equations are more accurate in estimating standing height and that a statistically significant age dependence in H/S ratio exists for women; however, the actual differences in the estimated values between the three methods are small (0.3-inch maximum SEE) and may be the result of the limited accuracy of measuring standing and sitting heights.
Spirometric prediction equations using the subjects age, sex, observed spirometric values, and sitting height were developed. These equations are listed in Table 3.
Table 1—Physical Characteristics of Population

Group	No.	Age, yr	Standing Height, In	Sitting Height, In	S/H Ratio
Men	103	58 ±11	69 ±3	36 ± 1	1.93 ±0.05
Women	93	57 ±10	64 ±2	34 ±2	1.90 ±0.05

Table 2—Comparison of Values for SEE

Group	Fixed H/S Ratio	Age-Variable H/S Ratio	S and Age Regression*
Men	1.78	1.76	1.57
Women	1.85	1.78	1.55

Table 3—Sitting Height Spirometric Prediction Equations

Group and Equation	r Value	SEE
Men
FVC (L) = 0.1836S – 0.0399A + 0.4222	0.6645	0.6644
FEV* (L) = 0.1181S -0.0401A +1.4370	0.7268	0.4980
FEF200-1200 (L/sec) = 0.1094S –	0.5551	1.7767
0.1021A+ 9.47811*
FEF25-75% (L/sec) = 0.0182S-	0.5484	0.9274
0.0546A + 5.5467
FEV₁/FVC% = 95.633 – 0.2723S – 0.2503A	0.3793	6.4030
Women		‘
FVC (L) = 0.1756S – 0.0293A – 0.9539	0.6675	0.5069
FEVi (L) = 0.1340S – 0.0239A – 0.8136	0.6872	0.3799
FEF200-1200 (L/sec) = 0.2569S –	0.4683	1.1683
0.0374A-1.5970
FEF25-75% (L/sec) = 0.1322S –	0.4675	0.6937
0.0250A-0.7273
FEV₁/FVC% = 63.698 + 0.4109S – 0.1148A	0.2858	4.9346

Category: Health

Tags: adults incapable of standing, physical characteristics, Pulmonary Function