How to interpret reduced forced expiratory volume in 1 s (FEV₁)/vital capacity ratio with normal FEV₁

Abstract

The aim of the present study was to determine whether the combination of low forced expiratory volume in 1 s (FEV1)/vital capacity (VC) ratio with normal FEV1 represents a physiological variant or a sign of early airflow obstruction.We studied 40 subjects presenting with low FEV1/VC, but FEV1 within the range of normality predicted by European Respiratory Society reference equations, and 10 healthy controls. All subjects completed two questionnaires and underwent comprehensive pulmonary function testing, which included methacholine challenge and single-breath nitrogen wash-out.According to the questionnaires, the subjects were assigned to three groups, i.e. rhinitis (n58), bronchial asthma (n513) and chronic obstructive pulmonary disease (COPD; n512). Subjects with negative responses to questionnaires were assigned to an asymptomatic group (n57). Airway hyperresponsiveness was found in four subjects of the rhinitis group, all of the asthma group, and 10 of the COPD group; in the last two groups, it was associated with signs of increased airway closure and gas trapping. Bronchodilator response to salbutamol was positive in only a few individuals across groups. In the asymptomatic group, no significant functional changes were observed, possibly suggesting dysanaptic lung growth.In subjects with low FEV1/VC and normal FEV1, questionnaires on respiratory symptoms together with additional pulmonary function tests may help to clarify the nature of this pattern of lung function. KEYWORDS: Atopic rhinitis, bronchial asthma, chronic obstructive pulmonary disease, dysanaptic lung growth, methacholine challenge, single-breath nitrogen wash-out T he assumption that a decrease in forced expiratory volume in 1 s (FEV1) and its ratio to vital capacity (VC) below the fifth percentile of the predicted normal value indicates an obstructive pulmonary abnormality is a useful simple approach [1]. However, in some individuals with VC normal or higher than normal, the FEV1/VC ratio may lie below the normal range while the FEV1 is still above the lower limit of normality [2][3][4][5]. Whether this spirometric pattern represents a physiological variant, possibly due to dysanaptic lung growth [6][7][8], or an early sign of airflow obstruction, possibly due to increased airway resistance [9] or loss of elastic recoil [10], is unknown. As the treatment of obstructive pulmonary diseases is based on proper recognition of airflow obstruction [11,12], the interpretation of this functional pattern is of practical relevance.The present study was designed to investigate whether a careful assessment of respiratory symptoms, combined with tests sensitive to abnormalities of airway function, may help to interpret the pattern of low FEV1/VC ratio with normal FEV1. For this purpose, 40 subjects were studied who presented with an FEV1/VC ratio below and an FEV1 above their lower limits of normality according to the European Respiratory Society (ERS) predicting equations [13]. Symptoms were assessed by questionnaires and lung function by addit...

Mechanisms of airway hyper‐responsiveness in asthma: the past, present and yet to come

“…Airway hyper-responsiveness is used as a tool in the diagnosis, classification of severity [8] and management [9,10] of asthma. AHR is useful in those who report symptoms [9], particularly in those with normal baseline lung function as measured by spirometry [11]. The presence of AHR is associated with increased decline in lung function [12], even in those with asymptomatic AHR [13], increased risk for the development of asthma [12] and increased likelihood of the persistence of wheeze from childhood to adulthood [14].…”

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“…On the other hand, a decreased FEV 1 /VC ratio is not always an unquestionable sign of disease. In a study of 1386 subjects undergoing spirometry testing for preventive medicine, a reduced FEV 1 /VC ratio with FEV 1 within or above the normal range was found in about 3% . Of these subjects, 62% had questionnaire responses and additional pulmonary function tests suggestive of an obstructive disorder (asthma or COPD), but the remaining had lung function indistinguishable from a control group of definitely healthy subjects (Fig.…”

“…The phase III slope was significantly increased in 13 subjects with responses to questionnaire suggestive of COPD . Reprinted from B arisione et al . COPD , chronic obstructive pulmonary disease; FEV 1 , forced expiratory volume in 1 s; LLN , lower limit of normal; VC , vital capacity.…”

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