Fig. 2: Modeling the path from respiration to CSF net flow.
From: Human cerebrospinal fluid net flow enhanced by respiration during the awake state
a To assess causality and evaluate unique contributions, we performed structural equation modeling and multivariate regression. Results indicated that in the FM (T = 20, NT = 25) CSF net flow is influenced by both mechanical (SSS) and autonomic (HR) pathways, whereas in the LV (T = 19, NT = 23) CSF dynamics were primarily driven by the mechanical SSS pathway. The lines represent β-values, which are standardized regression estimates from the multivariate analysis, with FM shown in pink and LV in light green. b, c Inhale length and diaphragm displacement, identified as key respiratory features from the SEM modeling, were examined for correlations with CSF mean speed, CSF displacement, and CSF net flow in the FM and LV. In the FM, both inhale length and diaphragm displacement strongly correlated with CSF displacement and CSF net flow. Specifically, inhale length correlated with CSF displacement (T: p < 0.0001; NT: p < 0.0001) and CSF net flow (T: p = 0.002; NT: p < 0.0001), as well as diaphragm displacement correlated with CSF displacement (T: p = 0.0004; NT: p < 0.0001) and CSF net flow (T: p = 0.0015; NT: p = 0.0018). In the LV, inhale length correlated with CSF displacement (T: p = 0.0001; NT: p < 0.0001) and CSF net flow (T: p = 0.0101; NT: p = 0.0043), whereas diaphragm displacement correlated only with CSF displacement (T: p = 0.1713; NT: p = 0.0004). These correlations support the SEM modeling with FM and LV differential pathways linking respiratory features to CSF dynamics. Linear regression analyses were performed using Pearson’s correlation with two-sided tests. Pearson’s correlation analyses were conducted separately in T (light blue) and NT (gray). Source data are provided as a Source Data file. A.U. arbitrary unit, Chest chest displacement, CSF cerebrospinal fluid, DB deep breathing, Dia diaphragm displacement, Dis CSF displacement, FM foramen magnum, HR HR displacement, Lung lung area change during one respiratory cycle, LV lateral ventricle, MaxFlow rate CSF maximum flow rate, MeanPV mean difference between peak and valley velocity, NT non-trained, RB regular breathing, SSS superior sagittal sinus, T trained.
