Preserved ratio impaired spirometry: clinical, imaging and artificial intelligence perspective

Preserved ratio impaired spirometry (PRISm) is a pulmonary function pattern characterized by a forced expiratory volume in one second (FEV1) to forced vital capacity ratio greater than 0.70, with an FEV1 that is below 80% of the predicted value, even after the use of bronchodilators. PRISm is considered a form of "Pre-Chronic Obstructive Pulmonary Disease (Pre-COPD)" within the broader scope of COPD. Clinically, it presents with respiratory symptoms and is more commonly observed in individuals with high body mass index, females, and those who are current smokers. Additionally, it is frequently associated with metabolic disorders and cardiovascular diseases. Regarding prognosis, PRISm shows considerable variation, ranging from improvement in lung function to the development of COPD. In this article, we review the epidemiology, comorbidities, and clinical outcomes of PRISm, with a particular emphasis on the crucial role of imaging assessments, especially computed tomography scans and magnetic resonance imaging (MRI) technology, in diagnosing, evaluating, and predicting the prognosis of PRISm. Comprehensive imaging provides a quantitative evaluation of lung volume, density, airways, and vasculature, while MRI technology can directly quantify ventilation function and pulmonary blood flow. We also emphasize the future potential of X-ray technology in this field. Moreover, the article discusses the application of artificial intelligence, including its role in predicting PRISm subtypes and modeling ventilation function.