Long-wave infrared imaging for respiratory rate measurement in a patient with amyotrophic lateral sclerosis: A case report

Respiratory monitoring is important in amyotrophic lateral sclerosis patients as progressive respiratory muscle weakness often leads to respiratory failure. We performed single-case feasibility evaluation of long-wave infrared imaging for noncontact respiratory rate estimation in a hospitalized amyotrophic lateral sclerosis patient and compared it with red-green-blue camera-based optical flow analysis and electrocardiogram-derived respiration. Respiratory rate was assessed using four methods: (a) manual counting as the ground truth; (b) long-wave infrared; (c) red-green-blue; and (d) single-lead electrocardiogram under three lighting conditions (regular, dim, and dark) with three 1-min trials per condition. Estimation accuracy was evaluated using mean absolute error relative to manual counting. Long-wave infrared imaging demonstrated the highest accuracy across all lighting conditions, with mean absolute errors of 1.67, 0.33, and 2.33 breaths per min, respectively. Red-green-blue-based estimation performed moderately well under regular and dim lighting but showed reduced accuracy in darkness, including one failed trial. Electrocardiogram-derived respiration showed the lowest accuracy and greatest variability across conditions. The limitations of the present study include its single-case design and absence of objective flow-based respiratory reference signals. However, this study demonstrates the feasibility and illumination robustness of long-wave infrared-based noncontact respiratory rate estimation in a hospital environment and supports further investigation of this approach for respiratory monitoring in amyotrophic lateral sclerosis patients.