Grading the Severity of Obstruction in the Presence of a Restrictive Ventilatory Defect

doi:10.1378/chest.122.4.1365

Chest

Volume 122, Issue 4, October 2002, Pages 1365-1369

https://doi.org/10.1378/chest.122.4.1365 Get rights and content

Study objectives

No recommendation currently exists for grading the severity of airway obstruction in the presence of additional restriction. The grading of airway obstruction is currently based on the FEV₁ (American Thoracic Society [ATS] recommendations), while prior recommendations by the Intermountain Thoracic Society (ITS) graded the severity of obstruction based on the FEV₁/FVC ratio. The objective was to compare the grading of airway obstruction using the percent predicted FEV₁ (ATS) with a confidence interval-based system (ITS), with particular focus on pulmonary functions in patients having both airway obstructions and restrictions.

Design

Retrospective analysis.

Setting

Tertiary medical center.

Patients

A retrospective analysis of 21,499 patient pulmonary function tests (PFTs) was performed. The predicted values of Crapo and coworkers were used.

Measurements and results

The distribution of the severity of the obstruction was compared using the ATS and ITS methods for PFTs with normal, increased, or decreased total lung capacity (TLC). Analysis was performed using the χ² method. Of the 21,499 PFTs that were analyzed, TLC was measured in 28% (5,962 PFTs). In this cohort, 44% (2,619 PFTs) gave evidence of obstruction. Of these, 147 PFTs demonstrated additional restriction. While the ATS criteria graded 133 of these PFTs (90%) as being severe, the ITS criteria graded only 4 PFTs (3%) as severe (the severity distribution between the methods was significantly different [p < 0.01]).

Conclusions

In view of the possible overestimation of the severity of obstruction in PFTs with concurrent restriction using the percentage of predicted FEV₁ values, consideration should be given to grading the severity of obstruction on the basis of the FEV₁/FVC ratio in this specific subset of PFTs.

Section snippets

Materials and Methods

The Cedars Sinai Medical Center is a tertiary referral center serving predominantly Medicare, health maintenance organizations, Medi-Cal, and privately funded patients. The studies were performed in a fully equipped (SensorMedics Corporation; Yorba Linda, CA) pulmonary function laboratory. The equipment remained unchanged for the study period, the equipment and techniques conformed to ATS criteria.⁴

A retrospective analysis was performed on a computerized database of all PFTs meeting the ATS

Results

Database analysis revealed 21,499 PFTs, with 50.5% performed on men and 49.5% on women. The mean age in men was 59.5 years, and in women it was 59.2 years. The mean height in men was 68.3 inches, and in women it was 62.9 inches.

TLC was measured in 5,962 of the above PFTs (both by means of helium dilution and plethysmography). Of these studies, the results of 2,619 PFTs (43.9%) gave evidence of obstruction, of which 512 (19.5%) were graded as revealing severe obstruction using the ITS grading

Discussion

Pulmonary function tests have become a part of routine health examinations, providing objective and quantifiable measures of lung function. They are used to evaluate and monitor diseases that affect heart and lung function, to monitor the effects of environmental, occupational, and drug exposures, and to assess the risks of surgery.³ The interpretation of lung function testing is based on the relationship of the measured values to the reference values.

PFTs may be used to assess the causes of

References (11)

American Thoracic Society
Lung function testing: selection of reference values and interpretive strategies
Am Rev Respir Dis
(1991)
AH Morris et al.
Clinical pulmonary function testing: a manual of uniform laboratory procedures
(1984)
RO Crapo
Pulmonary function testing
N Engl J Med
(1994)
RO Crapo et al.
Reference spirometric values using techniques and equipment that meet ATS recommendations
Am Rev Respir Dis
(1981)
RO Crapo et al.
Lung volumes in healthy nonsmoking adults
Bull Eur Physiopathol Respir
(1982)

There are more references available in the full text version of this article.

Cited by (12)

Mixed Ventilatory Defects in Pulmonary Sarcoidosis: Prevalence and Clinical Features
2020, Chest
Citation Excerpt :
These findings were robust in patients with biopsy results, in both life-long nonsmokers and current/former smokers, and applied equally to recently diagnosed patients and to those with long-standing sarcoidosis. The limitations of traditional methods for evaluating airflow obstruction in patients with concurrent restriction have previously been explored in patient cohorts with a variety of restrictive disorders.9,16 In both cohorts, FEV1 values were adjusted against TLC values in the quantification of the severity of airflow obstruction, to quantify FEV1 reduction ascribable to airflow obstruction.
In cohort studies of pulmonary sarcoidosis, abnormal ventilatory patterns have generally been subdivided into restrictive and obstructive defects. Mixed ventilatory defects have largely been overlooked in pulmonary sarcoidosis, as total lung capacity has seldom been taken into account in historical series.
This study evaluated the prevalence of mixed disease in pulmonary sarcoidosis and its clinical associations.
In patients with pulmonary sarcoidosis (N = 1,110), mixed defects were defined according to American Thoracic Society/European Respiratory Society criteria. Clinical data, pulmonary function variables, and vital status were abstracted from clinical records. Chest radiographs were evaluated independently by two experienced radiologists.
The prevalence of a mixed ventilatory defect was 10.4% in the whole cohort, rising to 25.9% in patients with airflow obstruction. Compared with isolated airflow obstruction, mixed defects were associated with lower diffusing lung capacity for carbon monoxide levels (50.7 ± 16.3 vs 70.8 ± 18.1; P < .0001), a higher prevalence of chest radiographic stage IV disease (63.5% vs 38.3%; P < .0001), and higher mortality (hazard ratio, 2.36; 95% CI, 1.34-4.15; P = .003). These findings were reproduced in all patient subgroup analyses, including patients with a histologic diagnosis, a clinical diagnosis, incident disease, and prevalent disease.
Mixed disease is present in approximately 25% of patients with pulmonary sarcoidosis and airflow obstruction and is associated with lower diffusing lung capacity for carbon monoxide levels, a higher prevalence of stage IV disease, and higher mortality than seen in a pure obstructive defect. These observations identify a distinct phenotype associated with a mixed ventilatory defect, justifying future studies of its clinical and pathogenetic significance.
Grading the severity of obstruction in mixed obstructive-restrictive lung disease
2011, Chest
Citation Excerpt :
Despite apparent agreement that overestimation of the degree of obstruction occurs in the presence of restriction, no consensus has emerged on how to better grade the severity of obstruction in these patients. The approach presented by Balfe and colleagues3 proposed using ITS criteria6 to grade obstruction based on the FEV1/FVC ratio, and indeed, this approach lowered the severity grade in most subjects. In fact, it showed a complete reversal in the distribution of severity grades to predominantly mild obstruction, which perhaps went too far and underestimated the true degree of obstruction.
The severity of obstructive pulmonary disease is determined by the FEV₁ % predicted based on the American Thoracic Society/European Respiratory Society (ATS/ERS) guidelines. In patients with coexisting restrictive lung disease, the decrease in FEV₁ can overestimate the degree of obstruction. We hypothesize that adjusting the FEV₁ for the decrease in total lung capacity (TLC) results in a more appropriate grading of the severity of obstruction.
We examined a large pulmonary function test database and identified patients with both restrictive (TLC < 80% predicted) and obstructive (FEV₁/FVC < the lower limit of normal) lung disease. FEV₁ % predicted was adjusted for the degree of restriction by dividing it by TLC % predicted. We compared the distribution of severity grading between adjusted and unadjusted values according to ATS/ERS criteria and determined how the distribution of severity would change based on asthma and COPD guidelines.
We identified 199 patients with coexisting restrictive and obstructive lung disease. By ATS/ERS grading, the unadjusted data categorized 76% of patients as having severe or very severe obstruction and 11% as having mild or moderate obstruction. The adjusted data classified 33% with severe or very severe obstruction and 44% with mild or moderate obstruction. Of the corrected values, 83% resulted in a change to less severe obstruction by ATS/ERS guidelines, and 44% and 70% of patients, respectively, would be reclassified as having less severe obstruction by current asthma and COPD guidelines.
This method results in a more appropriate distribution of severity of obstruction, which should lead to more accurate treatment of obstruction in these patients.
FEV<inf>1</inf>/FVC Severity Stages for Chronic Obstructive Pulmonary Disease
2023, American Journal of Respiratory and Critical Care Medicine
The Role of FEV1/FVC in the Prediction of Acute Exacerbation of COPD
2023, Research Square
Airflow obstruction categorization methods and mortality
2018, Annals of the American Thoracic Society
The physiological basis and clinical significance of lung volume measurements
2017, Multidisciplinary Respiratory Medicine

View all citing articles on Scopus

View full text

Chest

Clinical InvestigationsGrading the Severity of Obstruction in the Presence of a Restrictive Ventilatory Defect

Study objectives

Design

Setting

Patients

Measurements and results

Conclusions

Section snippets

Materials and Methods

Results

Discussion

Lung function testing: selection of reference values and interpretive strategies

Am Rev Respir Dis

Clinical pulmonary function testing: a manual of uniform laboratory procedures

Pulmonary function testing

N Engl J Med

Reference spirometric values using techniques and equipment that meet ATS recommendations

Am Rev Respir Dis

Lung volumes in healthy nonsmoking adults

Bull Eur Physiopathol Respir

Clinical Investigations
Grading the Severity of Obstruction in the Presence of a Restrictive Ventilatory Defect