Emerging Technologies and Trends in Lung Volume Estimation: A Review

Accurate lung volume (LV) estimation is critical for assessing respiratory health and diagnosing conditions such as asthma, chronic obstructive pulmonary disease (COPD), and restrictive lung diseases. While clinical gold-standard tools—spirometry, plethysmography, helium dilution, and arterial blood gas (ABG) analysis—provide reliable data, they are constrained by invasiveness, clinical setting requirements, and the inability to support continuous or ambulatory monitoring. These limitations underscore the demand for wearable, noninvasive technologies capable of enabling real-time, patient-centered respiratory tracking. This systematic literature review (SLR) assesses LV estimation technologies, focusing on wearable and contactless approaches. Studies published between 2014 and 2024 were sourced from IEEE Xplore, Scopus, and PubMed. A structured selection process based on the Angela guidelines was employed, narrowing an initial set of 304 publications to 45 relevant studies. Each study was analyzed based on device type, sensing methodology, measured lung parameters, participant characteristics, activity context, and validation strategies. The review highlights notable progress in wearable respiratory monitoring, particularly through flexible, textile-based, and printable sensor technologies. However, significant gaps persist in the standardization of validation methods, consistency of performance across diverse respiratory activities, and generalizability due to limited participant diversity. Most studies lack longitudinal data necessary for chronic disease monitoring. Future research must prioritize robust validation protocols, inclusive participant sampling, and long-term performance studies in real-world conditions. Addressing these challenges is essential when it comes to advancing wearable lung monitoring from experimental prototypes to clinically viable tools, enhancing early detection, remote monitoring, and personalized respiratory care, which could have far-reaching positive health implications.