A Review of the Role of FEV₁ in the COPD Paradigm

Figures & data

Table 1 Clinical variations between COPD and asthma

	COPD	Asthma
Age of onset	Usually > 40 years	Usually < 40 years, but any age
Smoking history	Often > 20 pack years	Little smoking history
Course of disease	Chronic, progressive	Intermittent
Response to inhaled bronchodilators	Respond; PFTs do not normalize	Respond quickly; some PFTs normalize
Response to corticosteroids	Most nonresponsive	Responsive Improved PFTs

NCAP. J Resp Diseases 2000;(9 Suppl); S1–S21; Doherty DE. AJM1 2004;77(12A):11S–23S.

Figure 1A Source ([36]), permission to reproduce required. “Risks” for various men if they smoke: differences between these lines illustrate effects that smoking, and stopping smoking, can have on FEV₁ in those men who are liable to develop chronic obstructive lung disease if they smoke. “Death” indicates deaths whose underlying cause is irreversible chronic obstructive lung disease, whether the immediate cause of death is respiratory failure, pneumonia, cor pulmonale, or aggravation of other heart disease by respiratory insufficiency. [These data are the composite of several individuals measured at various times (cross-sectional) and not following patients over several years (not longitudinal)]. Although this shows rate of loss of FEV, for one particular susceptible smoker, other susceptible smokers will have different rates of loss, thus reaching ‘disability’ at different ages” ([36]).

Figure 1B The upper dotted line represents the normal decline in those who have not smoked, or in smokers who are not susceptible to the effects of tobacco smoke on lung function decline. The lower dashed line represents an accelerated loss of lung function over time in those ‘susceptible’ smokers. The FEV₁ a susceptible 40 year old smoker was measured at 75% predicted (dotted vertical line). If one extrapolates that level of lung function of this susceptible individual (draw a horizontal line to the curve of a never smoker or one not susceptible to smoking), their ‘Lung Age’ is approximately 74 – equivalent lung function to that of a never smoker (or non-susceptible smoker) when they are 74.

Table 2 Variables and point values used for the computation of the BODE index

	Points on BODE Index
Variable	0	1	2	3
FEV1 (% predicted)+	≥ 65	50–64	36–49	≤ 35
Distance walked in 6 min (m)	≥ 350	250–349	150–249	≤ 149
Modified Medical Research Council Dyspnea Scale++	0–1	2	3	4
Body-mass index (kg/m^2)+++	> 21	≤ 21	–	–

Source:([49]), p. 1007, Table 2, permission to reproduce required.

The cutoff values for the assignment of points are shown for each variable. The total possible values range from 0 to 10 with higher scores indicating a greater risk of death.

+The forced expiratory volume in 1 second (FEV₁) categories are based on stages identified by the American Thoracic Society.

++Scores on the modified Medical Research Council (MMRC) dyspnea scale can range from 0 to 4 indicating that the patient is too breathless to leave the house or becomes breathless when dressing or undressing.

+++The values for body-mass index were 0 or 1 because of the inflection point in the inverse relation between survival and body-mass index at a value of 21.

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