Assessment of Noninvasive Measurement Techniques and Histologic Findings in a Mouse Model of LPS-Induced Acute Lung Injury

Studies involving rodent models of acute lung injury infrequently use oxygen saturation to characterize lung injury, even though it is the principal standard by which physiologic lung dysfunction is measured in humans. Assessing the clinical progression of lung injury in rodent models presents challenges due to their small size and limited ability to correlate physiologic outcomes with human disease. Furthermore, traditional methods for assessing lung injury rely on invasive techniques, including leukocyte quantification in lung tissue, analysis of bronchoalveolar lavage fluid, and histopathologic evaluation, most of which require euthanasia and preclude longitudinal assessments in the same animal. While body weight is a commonly used indicator of morbidity, additional noninvasive metrics such as pulse oximetry, heart rate, and respiratory rate may offer deeper insights into host responses. Here, we used the MouseOx Plus in conscious mice with a lipopolysaccharide (LPS)-induced lung injury to monitor cardiopulmonary parameters and determine whether there is a correlation between peak hypoxemia, body weight, and heart rate with the severity of the lung injury as defined by histologic assessment. We also evaluated the use of anesthesia to immobilize animals for collecting cardiopulmonary data, as is commonly done, and found that arterial saturation measurements were not significantly different in awake compared with anesthetized animals. However, body weight recovery was significantly decreased in anesthetized groups on days 4-5. Together, these data support the use of conscious pulse oximetry as a refinement method that noninvasively increases the rigor of the clinical data collected in mice with LPS-induced lung injury.