Kandimalla, Mahathi

Breathing is a physiological process that extends beyond gas exchange, linking neural, cardiovascular, glymphatic, and autonomic systems. This narrative review summarizes how breathing-based practices modulate physiological processes in the body and brain, emphasizing their applicability in clinical care. Regulating the pace and depth of breathing, particularly with relaxed exhalation, may engage vagal pathways that lower heart rate and blood pressure and promote a shift toward increased parasympathetic tone relative to sympathetic activity. Neuroimaging studies show that controlled breathing reduces activity in stress-related brain regions while enhancing networks supporting calm attention and emotional steadiness. Changes in breathing depth also influence cerebrospinal fluid movement, though direct evidence of waste clearance in humans is lacking. This review identifies populations requiring caution, including individuals with panic symptoms, significant cardiopulmonary disease, or pregnancy. Clinicians should distinguish between breathing-only and multimodal protocols when interpreting research findings, as combined interventions preclude attribution of benefit to breathing alone. Study design quality, particularly the use of active rather than waitlist controls, should inform how effect sizes are interpreted. Breathing practices are not a replacement for medical treatment but may represent accessible, low-cost adjuncts for stress reduction and cardiovascular regulation.

AbstractBackgroundSleep’s crucial role in maintaining brain health is increasingly recognized, particularly due to the rising prevalence of neurodegenerative diseases. It not only supports cognitive function but also aids in clearing brain metabolic waste through cerebrospinal fluid (CSF) dynamics. During sleep, especially in the non‐rapid eye movement (NREM) phase, CSF flow increases, essential for removing neurotoxic substances like amyloid‐beta proteins. This study explores the link between sleep respiratory patterns and CSF flow promotion.MethodElectroencephalography (EEG), and functional magnetic resonance imaging (fMRI) were simultaneously acquired during sleep from Gu, et al. (n = 29) (Gu et al. 2022). Respiration, measured via a respiratory belt, calculated respiratory volume (RV) as the standard deviation within a 5 second sliding window. EEG data processed delta band power (1‐4Hz) averaged across channels. Parcellated fMRI data using the brain template followed by the calculation of the averaged gray matter (GM) blood‐oxygen‐level‐dependent (BOLD) signal using the GM mask. CSF inflow was manually extracted from the fMRI’s bottom slice at the foramen magnum level. Subsequently, all signals were temporally aligned to the peak of the CSF inflow signal.ResultAt the time of CSF inflow (time = 0 sec. in the Figure 1A‐D), we observed an earlier increase in RV and EEG delta power, followed by changes in the GM BOLD signal (Figure 1). EEG and RV changes preceded the BOLD signal changes, which, in turn, preceded changes in CSF flow. Sensitivity to detect RV involvement during MRI varied with the placement of the respiratory belt, being least sensitive on the chest and more on the abdomen.ConclusionThese findings raise an interesting question on the role respiratory patterns during sleep, particularly in the NREM phase. Speculatively, RV change may influence CSF circulation during NREM sleep (Figure 1E). This enhancement in CSF flow is crucial for the clearance of metabolic waste from the brain, potentially reducing the risk of neurodegenerative diseases. Our findings indicate that respiratory volume may serve as a significant marker for CSF circulation during sleep.