Maximal Static Respiratory and Sniff Pressures in Healthy Children: A Systematic Review and Meta-Analysis.

RATIONALE: Respiratory muscle strength in children can be assessed by maximal inspiratory (MIP), expiratory (MEP), and sniff nasal inspiratory pressures (SNIP). However, previous studies involved small cohorts of healthy children and reported wide reference ranges.

OBJECTIVES: To perform a systematic review to summarize existing reference ranges for MIP, MEP, and SNIP tests in healthy children and to conduct a meta-analysis to develop comprehensive prediction equations.

DATA SOURCES: Five databases were searched for relevant studies from database inception to May 29th, 2017.

DATA EXTRACTION: Study inclusion was limited to publications that evaluated MIP, MEP, and SNIP values in healthy children aged 18 years or younger. Studies were also excluded if testing methodology differed greatly from the 2002 American Thoracic Society Statement on Respiratory Muscle Testing. Requests for raw data were made to authors via email.

SYNTHESIS: A total of 18 studies including 3,509 children were systematically reviewed. Diagnostic accuracies of the included studies were assessed using the QUADAS-2 tool, which revealed a high risk of bias for flow and timing and for applicability that may influence the generalizability of our findings. All 18 studies evaluated respiratory pressures in children in seated position. MIP tests were conducted from residual volume, MEP from total lung capacity, and SNIP from functional residual capacity. The MIP and MEP values in three age groups for boys and girls were summarized using meta-analysis based on individual participant data from 5 studies containing 1,709 healthy children. Further analyses showed MIP and MEP were significantly greater in boys than girls (p<0.0001). In both sexes, MEP values were always greater than MIP values (p<0.05). Multivariable random effects models were then performed to establish sex-specific prediction equations. These equations found age, height, and weight to be significant predictor variables. Only 2 studies with SNIP values from healthy children were included in the review but were not part of the meta-analysis.

CONCLUSION: We summarized the available reference ranges for MIP, MEP, and SNIP tests from existing literature, especially for three age groups, and developed prediction equations that can be used in pulmonary function laboratories to aid clinicians. Existing literature on SNIP test is limited and future studies are encouraged to explore its use in children.