Predictive equations for respiratory muscle strength by anthropometric variables

Maximal Respiratory Pressure Reference Equations in Healthy Adults and Cut-off Points for Defining Respiratory Muscle Weakness

INTRODUCTION

Maximal inspiratory and expiratory pressures (PImax/PEmax) reference equations obtained in healthy people are needed to correctly interpret respiratory muscle strength. Currently, no clear cut-off points defining respiratory muscle weakness are available. We aimed to establish sex-specific reference equations for PImax/PEmax in a large sample of healthy adults and to objectively determine cut-off points for respiratory muscle weakness.

METHODS

A multicentre cross-sectional study was conducted across 14 Spanish centres. Healthy non-smoking volunteers aged 18-80 years stratified by sex and age were recruited. PImax/PEmax were assessed using uniform methodology according to international standards. Multiple linear regressions were used to obtain reference equations. Cut-off points for respiratory muscle weakness were established by using T-scores.

RESULTS

The final sample consisted of 610 subjects (314 females; 48 [standard deviation, SD: 17] years). Reference equations for PImax/PEmax included body mass index and a squared term of the age as independent variables for both sexes (p<0.01). Cut-off points for respiratory muscle weakness based on T-scores ≥2.5 SD below the peak mean value achieved at a young age were: 62 and 83cmH2O for PImax and 81 and 109cmH2O for PEmax in females and males, respectively.

CONCLUSION

These reference values, based on the largest dataset collected in a European population to date using uniform methodology, help identify cut-off points for respiratory muscle weakness in females and males. These data will help to better identify the presence of respiratory muscle weakness and to determine indications for interventions to improve respiratory muscle function.

Correlation and Predicted Equations of MIP/MEP from the Pulmonary Function, Demographics and Anthropometrics in Healthy Thai Participants aged 19 to 50 Years

Objective:

To identify the correlations and possible predicted equations of maximal inspiratory (MIP) and expiratory mouth pressure (MEP) values from pulmonary function test (PFT), demographics, and anthropometrics.

Methods:

This study involved 217 healthy participants (91 males and 126 females) aged 19 to 50 years. The PFT (forced vital capacity; FVC, forced expiratory volume in 1 second; FEV1, maximal mid-expiratory flow; MMEF, and peak expiratory flow; PEF) was performed by spirometry, whereas MIP and MEP were evaluated by a respiratory pressure meter. Pearson correlation and multiple linear regression, with the stepwise method, were used for statistical analysis.

Results:

The MIP and MEP had a significant positive correlation with weight, height, body mass index (BMI), and waist circumference. MIP had a significant positive correlation with FVC (%) and PEF (L/s and %), as well as a negative correlation with FEV1/FVC (ratio and %) and MMEF (%). Whereas, MEP showed a significant positive correlation with PEF (L/s and %) and negative correlation with FEV1/FVC (ratio and %) and MMEF (L/s). Finally, the predicted MIP and MEP equations were 103.988−97.70 × FEV1/FVC + 31.292 × Sex (male = 1 and female = 0) + 0.662 × PEF (%) and 47.384 + 3.603 × PEF (L/s)−9.514 × MMEF(L/s) + 30.458 × Sex (male = 1 and female = 0) + 0.534 × PEF (%), respectively.

Conclusion:

The respiratory muscle strengths can be predicted from the pulmonary function test, and gender data.

Correlação da força muscular respiratória com medidas antropométricas e nível de atividade física em adultos da atenção primária

RESUMO O objetivo deste estudo foi correlacionar a força muscular respiratória com as medidas antropométricas e o nível de atividade física de indivíduos adultos da atenção primária. Trata-se de um estudo transversal, realizado em uma unidade básica de saúde, onde foram incluídos indivíduos de ambos os sexos e com idade superior a 18 anos. A força muscular respiratória foi analisada pela pressão inspiratória máxima (PImáx) e pressão expiratória máxima (PEmáx), por meio do manovacuômetro, onde valores pressóricos acima de 80% em relação ao predito foram considerados normais. Utilizou-se balança mecânica, estadiômetro e fita métrica para mensuração das principais medidas antropométricas: índice de massa corporal (IMC), circunferência de pescoço (CP), circunferência abdominal (CA), circunferência de quadril (CQ), relação cintura-quadril (RCQ) e o índice de adiposidade corporal (IAC). O nível de atividade física foi determinado pelo questionário internacional de atividade física (IPAQ), onde os indivíduos foram categorizados como sedentário, irregularmente ativo A, irregularmente ativo B, ativo ou muito ativo, sendo realizada também a estimativa dos equivalentes metabólicos (MET) alcançados. Foram avaliados 110 indivíduos adultos (78,1% do sexo feminino; 51,9±12,3 anos), e com porcentagem em relação ao predito (%) de PImáx de 96,3±32,4% e 98,9±27,3% de PEmáx. A %PImáx apresentou fraca correlação com o IAC (r=0,23; p=0,01) e com a CQ (r=0,20; p=0,03), e a %PEmáx com o IMC (r=0,26; p<0,01) e IAC (r=0,30; p<0,01). Não houve diferença dos valores médios de %PImáx (p=0,61) e %PEmáx (p=0,54) entre as categorias do IPAQ, além de não existirem correlações (p>0,05) com os MET estimados. Em adultos da atenção primária, a força muscular respiratória apresentou fraca correlação com IMC, CQ e IAC, porém sem correlação com o nível de atividade física.

Predictive equations of maximum respiratory mouth pressures: A systematic review

BACKGROUND

Maximum inspiratory (Pimax) and expiratory (Pemax) mouth pressures are commonly used to detect respiratory muscle weakness resorting to predictive equations established for healthy people. There are several predictive equations, but they are widespread in the literature. This study aimed to review the existent predictive equations of maximum inspiratory (Pimax) and expiratory (Pemax) mouth pressures for adults. Additionally, we aimed to identify which ones were generated based on international standards.

METHODS

A systematic review of predictive equations of Pimax and Pemax for healthy adults was conducted. A comprehensive search was performed of Cochrane Library, EBSCO, PubMed, Scopus and Web of Science to identify studies that presented at least one equation for Pimax or Pemax developed for healthy adults. The quality of studies was assessed by two reviewers with the Quality Assessment of Diagnostic Accuracy Studies (Quadas-2).

RESULTS

Risk of bias was high in 8 of the 20 studies included. Forty-two Pimax and 34 Pemax equations were found, mostly using the variables age (n=39), weight (n=20) and height (n=8). These equations explained 3 to 96% of the Pimax/Pemax variance. They were developed with individuals from 11 countries (Portugal not included). Twelve Pimax and eight Pemax equations complied with international standards.

CONCLUSIONS

This review gathered the predictive equations that have been developed for both Pimax and Pemax, however most were generated from unstandardized procedures. Future studies should explore the suitability of these equations for populations for which specific ones are not available, such as the Portuguese population, and develop new equations if necessary.