Restriction with Normal Spirometry: A Retrospective Cohort Study

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Diagnostic Imaging

Background:

• Normal spirometry is often assumed to indicate the absence of lung restriction.
• Emerging evidence suggests that lung restriction may be prevalent even with normal spirometry results.
• The clinical implications of lung restriction in patients with normal spirometry remain unclear.

Purpose of the Study:

• To investigate the clinical characteristics associated with lung restriction in patients exhibiting normal spirometry.
• To determine the impact of lung restriction with normal spirometry on patient survival outcomes.

Main Methods:

• Analysis of pulmonary function tests (PFTs), including static and dynamic lung volumes, from 2012-2025.
• Multivariable logistic regression to identify factors associated with restriction in normal spirometry.
• Cox proportional hazards modeling to assess the association between restriction and all-cause mortality, adjusting for key spirometric parameters.

Main Results:

• A significant prevalence of restriction (25.7%) was found among patients with normal spirometry.
• Restriction was more common in older, non-White patients, and those with interstitial lung disease (ILD).
• Restriction was associated with increased all-cause mortality (aHR 1.45) compared to normal spirometry without restriction.

Conclusions:

• Lung restriction in patients with normal spirometry is associated with interstitial lung disease (ILD).
• This condition is linked to a decreased survival rate.
• Clinically significant ventilatory impairments can be present even when spirometry results appear normal.