Small Airways Obstruction Syndrome

doi:10.1378/chest.116.1.231

Chest

Volume 116, Issue 1, July 1999, Pages 231-233

https://doi.org/10.1378/chest.116.1.231 Get rights and content

Study objectives

To clarify the significance of a functional lung pattern characterized by a decreased vital capacity (VC) and an increased residual volume (RV), but with a normal FEV₁/VC ratio.

Setting

A university teaching hospital.

Subjects

Patients with bronchial asthma, pulmonary emphysema, and small airways disease, and older subjects.

Measurements

Measurements of static and dynamic lung volumes, diffusing capacity of the lung for carbon monoxide (as measured by the single-breath method), nitrogen slope of the alveolar plateau, and closing volume (as measured by the single-breath O₂ test).

Conclusion

A functional pattern characterized by a decreased VC and FEV₁and increased RV, but with a normal FEV₁/VC ratio and total lung capacity, reflects an obstructive impairment of small airways.

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Cited by (71)

Lung Function Testing in Chronic Obstructive Pulmonary Disease
2020, Clinics in Chest Medicine
Citation Excerpt :
These assertions, however, should be tempered with practicalities: (a) repeating spirometry on a short-term basis is not a trivial task in most health care systems and (b) the risk of false positive or false negative results of any diagnostic test is always judged by the physician on an individual basis: clinical history, dyspnea severity, and likelihood of an alternative diagnosis in those at risk for COPD (Box 4). As mentioned, the FEV1/FVC ratio may remain within the normal range even after considerable small airway pathologic condition has occurred.51 It has been argued that defining a fixed time denominator “to correct” FEV1 would decrease variability of the ratio.
Is the Slow Vital Capacity Clinically Useful to Uncover Airflow Limitation in Subjects With Preserved FEV<inf>1</inf>/FVC Ratio?
2019, Chest
FVC may underestimate the slow vital capacity (SVC) due to early closure of the small airways at low lung volumes in the forced maneuver. It remains unclear whether using SVC instead of FVC in the FEV₁/vital capacity (VC) ratio increases the yield of spirometry in detecting airflow limitation or, alternatively, leads to a false-positive finding for obstruction.
This study included 13,893 adult outpatients with FEV₁/FVC and total lung capacity at or above the lower limit of normal. A cluster of clinical and physiological variables defined the probability of airway disease and dysfunction, respectively.
The prevalence of “discordance” (preserved FEV₁/FVC but low FEV₁/SVC) was 20.4%: discordant subjects had lower mid-expiratory flows, higher airway resistance, worse gas trapping, and ventilation distribution abnormalities than “concordant” subjects (both ratios preserved) (P < .05). Regardless of sex, age < 60 years, BMI > 30 kg/m², and FEV₁ > 70% predicted were associated with discordance (P < .001). Discordant subjects with preserved FEV₁/FVC but low FEV₁/SVC were four times more likely to be diagnosed with an obstructive airway disease by a respirologist compared with those with preserved FEV₁/SVC and FEV₁/FVC. The only exception was in the elderly subgroup with discordance (age > 70 years): only 10% of these subjects were subsequently diagnosed with an airway disease (P > .05).
Using SVC instead of FVC in the FEV₁/VC ratio enhances the yield of spirometry in detecting mild airflow obstruction in younger and obese subjects. The FEV₁/SVC ratio, however, should be used with caution in elderly subjects with preserved FEV₁/FVC because a low value may represent a false-positive finding for airflow limitation.
Longer duration of asthma is significantly associated with increased RV/TLC ratio
2017, Respiratory Medicine
Although FEV1/FVC ratio has been shown to be negatively associated with longer duration of asthma; an association between RV/TLC ratio and longer duration of asthma has not been explored.
Patients with established asthma for more than a year and met inclusion and exclusion criteria were recruited. Data obtained by questionnaire after informed consent was obtained, Pulmonary function tests and laboratory results were collected through chart review. Correlation and multiple linear regressions were used to analyze the data.
Among the 93 subjects, 61 were women. The mean age of patients was 58 ± 15 years, and the mean duration of asthma was 21 ± 18 years. The ethnic composition included: Caucasians 64%, Hispanics 28% and other groups 8%. The FEV1/FVC ratio was not significantly associated with duration of asthma (R2 = 0.15, p = 0.05). However, the RV/TLC ratio was significantly associated with duration of asthma (R2 = 0.46, p < 0.001).
RV/TLC ratio may be a better indicator than FEV1/FVC ratio to detect airway obstruction related to longer duration of asthma. Lung volume measurements should be done in addition to spirometry to detect changes related to airway obstruction in patients with longer duration of asthma.
FVC deterioration, airway obstruction determination, and life span in Ataxia telangiectasia
2015, Respiratory Medicine
Citation Excerpt :
Moreover, a decline in FVC ≥ 10% within 6 or 12 months showed a poor prognosis with idiopathic pulmonary fibrosis [22–24]. The decrease in FVC (%predicted) was formerly attributed to the presence of weak respiratory muscles, chest wall abnormality, and the significant amount of air that can remain trapped in the presence of severe scoliosis [25–27]. Although VT/FVC ratio is not included in the standardized interpretation of spirometry, our findings imply that the VT/FVC ratio may be an important marker in an AT patient's life span, since it increases in a stepwise manner for ∼5 years and then again ∼2-years prior to death.
Forced vital capacity (FVC) values decrease with progress of the disease in Ataxia telangiectasia (AT).
To study the effect of this process on airway obstruction determination and life span in AT.
Clinical data and yearly best spirometry maneuvers were collected retrospectively from 37 AT patients (196 spirometry tests) during 5.4 ± 1.8yrs (initial age 4–21 y). Twelve patients were walking (7 of them had recurrent respiratory system infections); 25 subjects were confined to wheelchair, of them 8 patients were towards end-stage lung disease. Spirometry indices included Forced Vital Capacity (FVC), mid-expiratory-flow (FEF25-75), and tidal volume (VT). We calculated FEF25-75/FVC and VT/FVC ratios.
FVC declined from 67 ± 8 while walking to 19 ± 6 %predicted values. FEF25-75 values that were elevated (116 ± 23 %predicted) while walking, decreased to 69 ± 27 %predicted at end-stage where 7 patients responded to bronchodilators. VT/FVC ratio was 0.25 ± 0.06 while walking, increased to 0.35 once on wheelchairs, and further increased to 0.57 ± 0.19 at end-stage disease. FEF25–75/FVC ratio was 2.54 ± 0.70 above normal (∼1.0) increasing to 4.16 ± 0.75 at end stage. A sharp elevation was seen in FEF25–75/FVC ratio when FEV1 was still ∼45 %predicted and 2-years prior to death.
Having a low baseline-FVC (60% predicted) artificially raises FEF25-75 values, so FEF25-75 of “mild obstruction” values may indicate severe airway obstruction in AT subjects. VT/FVC and FEF25-75/FVC ratios may therefore assist in revealing higher than normal breathing effort. The results further suggest adding VT/FVC and FEF25-75/FVC ratios to pulmonary function assessments in patients with AT.
Société de Pneumologie de Langue Française. Guidelines for clinical practice. Management of COPD. Update 2012: Pulmonary function tests
2014, Revue des Maladies Respiratoires
Lessons from the world trade center disaster: Airway disease presenting as restrictive dysfunction
2013, Chest
Citation Excerpt :
Thus, detection of distal airway disease was dependent on detecting heterogeneity of airflow distribution rather than increased airway resistance.41,42 Stănescu43 extended this syndrome to the “nonspecific” pattern of lung dysfunction, wherein VC is reduced but FEV1/VC and TLC remain within normal limits. RV was increased, indicating AT, and the term “small airway obstructive syndrome” was coined.
The present study (1) characterizes a physiologic phenotype of restrictive dysfunction due to airway injury and (2) compares this phenotype to the phenotype of interstitial lung disease (ILD).
This is a retrospective study of 54 persistently symptomatic subjects following World Trade Center (WTC) dust exposure. Inclusion criteria were reduced vital capacity (VC), FEV₁/VC > 77%, and normal chest roentgenogram. Measurements included spirometry, plethysmography, diffusing capacity of lung for carbon monoxide (Dlco), impulse oscillometry (IOS), inspiratory/expiratory CT scan, and lung compliance (n = 16).
VC was reduced (46% to 83% predicted) because of the reduction of expiratory reserve volume (43% ± 26% predicted) with preservation of inspiratory capacity (IC) (85% ± 16% predicted). Total lung capacity (TLC) was reduced, confirming restriction (73% ± 8% predicted); however, elevated residual volume to TLC ratio (0.35 ± 0.08) suggested air trapping (AT). Dlco was reduced (78% ± 15% predicted) with elevated Dlco/alveolar volume (5.3 ± 0.8 [mL/mm Hg/min]/L). IOS demonstrated abnormalities in resistance and/or reactance in 50 of 54 subjects. CT scan demonstrated bronchial wall thickening and/or AT in 40 of 54 subjects; parenchymal disease was not evident in any subject. Specific compliance at functional residual capacity (FRC) (0.07 ± 0.02 [L/cm H₂O]/L) and recoil pressure (Pel) at TLC (27 ± 7 cm H₂O) were normal. In contrast to patients with ILD, lung expansion was not limited, since IC, Pel, and inspiratory muscle pressure were normal. Reduced TLC was attributable to reduced FRC, compatible with airway closure in the tidal range.
This study describes a distinct physiologic phenotype of restriction due to airway dysfunction. This pattern was observed following WTC dust exposure, has been reported in other clinical settings (eg, asthma), and should be incorporated into the definition of restrictive dysfunction.

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Chest

Opinions/HypothesesSmall Airways Obstruction Syndrome

Study objectives

Setting

Subjects

Measurements

Conclusion

Am J Med

Chest

Chest

Lung function testing: selection of reference values and interpretative strategies

Am Rev Respir Dis

Clinical tests of respiratory function

The relations between structural changes in small airways and pulmonary-function tests

N Engl J Med

Early detection of chronic bronchitis and pulmonary emphysema

Lung volumes and forced ventilatory flows: standardization of lung function tests: European Community for Steel and Coal; Official Statement of the European Respiratory Society

Eur Respir J

Opinions/Hypotheses
Small Airways Obstruction Syndrome