Respiratory Function Analysis in Patients with Chronic Pain: An Umbrella Review and Meta-Analysis of Pooled Findings

Background: The main aim of this umbrella review was to assess the respiratory function in patients with chronic pain (CP), including patients with chronic neck pain (CNP), chronic low back pain (CLBP), and fibromyalgia syndrome (FMS). Methods: We searched in PubMed, PEDro, EMBASE, CINAHL, and Google Scholar (4 February 2023). The outcome measures were respiratory muscle strength (MIP/MEP) and pulmonary function (VC, MVV, FVC, FEV1, FEV1/FVC ratio, FEV25-75, and PEF). This review was previously registered in the international prospective register of systematic reviews, PROSPERO (CRD42023396722). The methodological quality was analyzed using AMSTAR and ROBIS scales, and the strength of the evidence was established according to the guidelines advisory committee grading criteria. To compare the outcomes reported by the studies, we calculated the standardized mean differences and the corresponding 95% confidence interval for the continuous variables. Results: Four systematic reviews with and without meta-analysis were included, from which a total of 15 primary studies were extracted. Five meta-analyses were carried out, using analyses by subgroup according to the type of CP. The meta-analyzing variables were MIP, MEP, MVV, FEV1, and FVC. Conclusions: Overall, patients with CP have decreased respiratory muscle strength with a moderate quality of evidence. Regarding the pulmonary function, patients with CNP showed a diminished VC, PEF, MVV, FEV1, and FVC, while FEV25-75 and the FEV1/FVC ratio were conserved with a limited to moderate quality of evidence. Finally, patients with FMS and CLBP only showed a decrease in MVV with a limited quality of evidence.