Differences in Respiratory Muscle Strength Measures in Well-Nourished and Malnourished Hospitalized Patients

Objective indicators of nutritional status are essential for accurate identification of malnutrition. Previous research has indicated an association between measures of respiratory muscle strength (RMS) and nutritional status. Measurement of RMS-including maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and sniff nasal inspiratory pressure (SNIP)-may provide evidence to support the assessment of nutritional status in hospitalized patients.

The purpose of this study was to determine whether there was a difference in MIP, MEP, and SNIP between well-nourished and malnourished hospitalized patients.

A cross-sectional study was conducted.

Patients were screened for eligibility criteria on admission by means of electronic medical records in general medical or surgical units at a tertiary care hospital in Chicago, IL, from January 2016 to January 2017. A total of 140 patients were included for analysis.

The primary outcome was detection of differences in measures of RMS between malnourished and well-nourished hospitalized patients. Nutritional status was assessed using subjective global assessment and Academy of Nutrition and Dietetics/American Society for Parenteral and Enteral Nutrition (Academy/ASPEN) criteria recommended to identify malnutrition. The MIP, MEP, and SNIP measures were obtained and reported as absolute values (expressed in centimeters of water) and percent of predicted values.

Independent t tests or Mann-Whitney U tests were used to determine differences in RMS measures between patients assessed as well nourished and those assessed as malnourished, depending on normality.

Compared with well-nourished patients, malnourished patients identified by subjective global assessment criteria had significantly lower absolute SNIP (73.7±28.7 vs 59.5±27.1 cm H₂O, P=0.004) and percent of predicted SNIP (78.6%±26.3% vs 64.8%± 30.0% predicted, P=0.006). Similarly, compared with well-nourished patients when Academy/ASPEN guidelines were used, malnourished individuals had significantly lower absolute SNIP (76.5±28.6 vs 58.3±26.3 cm H₂O, P<0.001), percent of predicted SNIP (81.4%±26.4% vs 63.5%±28.7% predicted, P<0.001), absolute MIP (83.5±34.6 vs 71.1±33.6 cm H₂O, P=0.05), and absolute MEP (108.7±36.6 vs 94.2±39.9 cm H₂O, P=0.04).

Differences in RMS between well-nourished and malnourished patients were observed when SNIP measures were used. However, there were no differences in MIP and MEP measures. Further research is needed to build on the findings from this study.