Effect of Cervical and Thoracic Manipulation on Pulmonary Function, Heart Rate Variability, and Blood Pressure in Individuals with Post-COVID-19 Syndrome: An Exploratory and Hypothesis-Generating Study

Background: Post-COVID-19 syndrome (PCS) is associated with persistent pulmonary, autonomic, and hemodynamic impairments. However, the acute effects of spinal manipulation on these systems in adults with PCS remain unclear. Purpose: To investigate the acute effects of combined cervical and thoracic spinal manipulation on pulmonary function, heart rate variability, and blood pressure in adults with PCS. Methods: This exploratory, hypothesis-generating study included 10 adults with PCS randomized to three sequences of spinal manipulation, sham manipulation, and control using a Latin-square crossover design with one-week washouts. Spirometry (FVC, FEV1, and FEV1/FVC) was assessed immediately after each intervention. Blood pressure and heart rate variability indices (RMSSD, SDNN, pNN50, LF, HF, and LF/HF ratio) were recorded at rest and 15, 30, 45, and 60 minutes post-intervention. Friedman/Wilcoxon tests and baseline-corrected sensitivity analyses were performed. Results: No significant differences were observed among conditions for FVC, FEV1, FEV1/FVC (all p>0.70), or the area under the curve of blood pressure, RMSSD, pNN50, HF, and LF/HF ratio (all p>0.27). Differences in SDNN and LF did not survive Bonferroni-corrected comparisons and disappeared after baseline correction, indicating between-session baseline variability rather than intervention effects. Conclusion: A single session of combined cervical and thoracic spinal manipulation did not produce consistent acute improvements in pulmonary function, blood pressure, or heart rate variability in adults with PCS. These physiological variables should not be considered primary indicators of response to an isolated manipulation session.