Objectives: Several equations for calculating maximal inspiratory pressure (MIP) have been validated for the Brazilian population; however, none exist for maximal dynamic inspiratory muscle pressure (S-Index). Methods: This cross-sectional study was conducted at two centers following approval by the institutional ethics committee. Healthy Brazilian adults were sequentially randomized to assess either the MIP or S-Index. Pulmonary function (spirometry), peripheral muscle strength (handgrip strength of the dominant upper limb - HGdUL), and physical activity level (IPAQ) were also evaluated. The S-Index and MIP values were reported as absolute values and compared using the Wilcoxon paired test. Multiple linear regression was used to develop reference equations. Lower limits of normality (LLNs) were stratified by sex and age using Z-scores, providing cut-off points to define inspiratory muscle weakness via the S-Index Deviation Score (SDS). Results: The final sample comprised 214 eutrophic volunteers, 50% men, with a mean age of 43.1 ± 15.0 years. The median MIP was significantly higher than the median S-Index (97.2 [96.7-112.0] vs. 92.5 [80.0-105.0] cmH2O; p<0.001). The predicted equation for the S-Index, which used age, sex, and HGdUL as predictors, was: S-Index = 69.72 + 10.765×sex (men = 1; women = 0) - 0.211×age + 0.797×HGdUL. Additionally, the LLNs and cut-off points for ventilatory muscle weakness by sex and age group were established. Conclusions: This study provides the first reference values for the S-Index in healthy, eutrophic Brazilian adults, including LLNs and cut-off points for diagnosing ventilatory muscle weakness.

Keywords: Respiratory muscle strength; S-Index; Respiratory muscle assessment.

Objective: To establish reference values and prediction equations for the strength index (S-Index), in order to meet the growing demand for clinical application and diagnostic understanding of maximal dynamic inspiratory pressure. Methods: This was a prospective study of 120 healthy subjects between 18 and 80 years of age. The S-Index, measured from RV to TLC after at least eight reproducible maximal maneuvers with a < 10% difference, was obtained. The MIP was also measured, and differences between S-Index and MIP values were analyzed. A multiple linear regression model estimating the S-Index value was based on clinically significant independent variables. For model cross-validation and diagnostic accuracy, we used a separate sample of COVID-19 survivors to compare the observed and predicted S-Index values. Results: The S-Index strongly correlated with the FEV1 and FVC. However, sex, age, weight, and height retained their significance in all final models, collectively explaining 62% of the variation in the observed values. The performance of the prediction equation was satisfactory in suggesting differences between COVID-19 survivors with an MIP < 80 cmH2O and those with an MIP = 80 cmH2O. For both sexes, the S-Index exhibited the potential for ruling out, rather than confirming, inspiratory muscle weakness. If below the lower limit of normal, further evaluation is important, especially in men. Conclusions: To our knowledge, this is the first set of reference equations for the S-Index based on a healthy adult population across various age groups in Brazil. Its potential as an adjunct index in evaluating inspiratory muscle strength was also explored for the first time.

Keywords: Maximal respiratory pressures; Muscle strength; Respiratory muscles.

Objective: The objectives of this study were to determine reference values for sniff nasal inspiratory pressure (SNIP) and to propose reference equations for the population of Brazil. Methods: We evaluated 243 healthy individuals (111 males and 132 females), between 20 and 80 years of age, with an FVC and FEV1/FVC ratio > 80% and > 85% of the predicted value, respectively. All of the subjects underwent respiratory muscle strength tests to determine MIP, MEP, and SNIP. Results: We found that SNIP values were higher in males than in females (p < 0.05) and that SNIP correlated negatively with age, for males (r = −0.29; p < 0.001) and for females (r = −0.33; p < 0.0001). Linear regression also revealed that age influenced the predicted SNIP, for males (R2 = 0.09) and females (R2 = 0.10). We obtained predicted SNIP values that were higher than those obtained for other populations. Conclusions: We have devised predictive equations for SNIP to be used in adults (20-80 years of age) in Brazil. These equations could help minimize diagnostic discrepancies among individuals.

Keywords: Respiratory Muscles; Respiratory Function Tests; Reference Values; Linear Models.

Objective: One of the major issues in the use of spirometry is the evaluation of the values obtained in comparison with standardized reference values. Such reference values should be determined by studying populations similar to the population in which they are intended to be used. Considering the anthropometric differences among races and the effect of regional issues, such as climate and air quality, it is recommended that these standards be set and used regionally. The objective of this study was to measure the spirometric values in residents of the Mazandaran province in Iran, as well as to determine which standardized reference values most closely correlate with the values obtained and to devise predictive equations for the target population. Methods: This was a cross-sectional study of 1,499 volunteers, from whom demographic and anthropometric data were collected. After having been instructed in the correct procedure, each volunteer underwent spirometry. From each volunteer, we obtained three spirometry curves that met the acceptability criteria established by the American Thoracic Society. The test with the highest values of FEV1 and FVC was employed in the analysis. Results: We observed significant correlations between the measured values and the reference values, for both genders. The strongest correlations were with the European Respiratory Society reference values and with the 18-20 year age bracket. The predictive equations devised were based on the regression coefficients obtained and the demographic data collected. Conclusions: Our results show that the European Respiratory Society standard is the most appropriate standard for use in the population studied.

Keywords: Spirometry/statistics  numerical data; Climate effects; Reference values; Iran.

Objective: To establish reference values for the Unsupported Upper Limb EXercise (UULEX) test, which measures peak arm exercise capacity, in healthy adults in Brazil. Methods: This was a cross-sectional study, involving presumably healthy individuals ≥ 30 years of age who completed questionnaires and underwent spirometry. All of the individuals underwent two UULEX tests 30-min apart. The outcome measure was the maximum time (in min) to completion of the test. Results: We included 100 individuals between 30 and 80 years of age. The mean test completion time was 11.99 ± 1.90 min among the women and 12.89 ± 2.15 min among the men (p = 0.03). The test completion time showed statistically significant correlations with age (r = −0.48; p < 0.001), gender (r = 0.28; p = 0.004), body mass index (BMI, r = −0.20; p = 0.05), and height (r = 0.28; p = 0.005). Linear regression analysis showed that the predictors of UULEX completion time were age (p = 0.000), BMI (p = 0.003), and gender (p = 0.019), which collectively explained 30% of the total variability. The mean UULEX completion time was 6% lower for the women than for the men. Conclusions: The present study was able to establish reference values for the UULEX test in healthy adults in Brazil. The values were influenced by age, gender, and BMI.

Keywords: Reference values; Exercise test; Upper extremity

Objective: To determine reference values for the six-minute pegboard and ring test (6PBRT) in healthy adults in Brazil, correlating the results with arm length, circumference of the upper arm/forearm of the dominant arm, and the level of physical activity. Methods: The participants (all volunteers) performed two 6PBRTs, 30 min apart. They were instructed to move as many rings as possible in six minutes. The best test result was selected for data analysis. Results: The sample comprised 104 individuals, all over 30 years of age. Reference values were reported by age bracket. We found that age correlated with 6PBRT results. The number of rings moved was higher in the 30- to 39-year age group than in the > 80-year age group (430.25 ± 77.00 vs. 265.00 ± 65.75), and the difference was significant (p < 0.05). The 6PBRT results showed a weak, positive correlation with the level of physical activity (r = 0.358; p < 0.05) but did not correlate significantly with any other variable studied. Conclusions: In this study, we were able to determine reference values for the 6PBRT in healthy adults in Brazil. There was a correlation between 6PBRT results and age.

Keywords: Upper extremity; Physical endurance; Exercise tolerance; Exercise test.

Objective: To develop regression equations for predicting six-minute and incremental shuttle walk distances (6MWD and ISWD, respectively), based on demographic characteristics, anthropometric variables, and grip strength. Methods: We evaluated 6MWD and ISWD in 98 healthy adults. Height, weight, and grip strength were also assessed. Using data from 90 of the participants (40 males; 60 ± 9 years of age), we devised linear equations adjusted for age, gender, height, and weight, and we developed alternate models that included grip strength. We prospectively applied the equations in the 8 remaining participants (4 males; 59 ± 10 years), who had been randomly separated from the initial sample. Results: Age, gender, height, and weight collectively explained 54.5% and 64.9% of the variance in 6MWD and ISWD, respectively, whereas age, height, weight, and grip strength collectively explained 54.4% and 69.0% of the respective variances. There was no significant difference between the measured and predicted 6MWD using equations with and without grip strength (14 ± 57 vs. 13 ± 67 m). Similar results were observed for ISWD (25 ± 104 vs. 25 ± 93 m). Conclusions: Grip strength is a determinant of ISWD and 6MWD; however, it could not improve the power of equations adjusted by demographic and anthropometric variables. The validity of our models including grip strength should be further evaluated in patients with skeletal muscle dysfunction.

Keywords: Walking; Exercise; Reference Values; Exercise test.

Objective: To compare MIP and MEP determined in healthy subjects with those predicted using the equations proposed in another study, and, if necessary, to suggest new equations for MIP and MEP to be used in the Brazilian population. Methods: The study sample comprised 60 healthy males and 60 healthy females, 20-80 years of age (20 subjects per ten-year age bracket). Maximal respiratory pressures were determined following a standardized protocol. Results: Regarding MIP, the measured values were significantly lower than those predicted for both males (31%) and females (24%). There were no significant differences between measured and predicted MEP in either gender. We found that age presented the greatest power to predict MIP and MEP in both genders. New equations were proposed. Conclusions: The previously proposed equations were unable to predict MIP and MEP for all of the subjects in our sample. Therefore, the results of this study can facilitate the prediction of respiratory muscle strength in healthy adult subjects in Brazil. Further studies, involving subjects from different regions of the country, could lead to the development of better tables or equations for maximal respiratory pressures in the Brazilian population.

Keywords: Respiratory muscles; Muscle strength; Reference values.

Objective: To develop regression equations for six-minute walk distance (6MWD) in healthy adults (20-80 years of age) in Brazil. Methods: We included 132 volunteers (66 males) without respiratory disease, cardiac disease, or comorbidities that affect ambulation. The volunteers completed three six-minute walk tests. Prior to and at the end of each test, we obtained SpO2 and maximal HR, as well as the Borg scale scores for sensation of dyspnea and lower limb fatigue. The data included in the final analysis were derived from the test with the greatest 6MWD. Results: The mean 6MWD values were 566 ± 87 m and 538 ± 95 m in males and females, respectively (p = 0.08). The 6MWD was greater in taller individuals and decreased in parallel with increases in age or body index mass (BMI). The best adjusted model was the quadratic model. We derived the following equation (valid for both genders): 6MWD = 511 + stature2 (cm) × 0.0066 − age2 × 0.030 − BMI2 × 0.068. This equation explained 55% of the variance in 6MWD. Conclusions: Reference values explaining a high proportion of the variance were derived by a quadratic regression model in healthy adults (of a wide range of ages) in Brazil. Keywords: Reference values; Exercise test; Walking.

Keywords: Reference values; Exercise test; Walking.

Objective: Physiologically, VC can vary according to gender, age, body weight and posture, as well as ethnic and anthropometric characteristics. In addition, various diseases can alter VC. In order to measure VC, it is necessary to motivate the patient, to make the instructions understandable, to provide clear information and to have a capable examiner. The objective of this study was to determine the impact that positive reinforcement during spirometry has on the measurement of VC in healthy volunteers. Methods: A randomized clinical trial involving 105 healthy volunteers, randomly allocated to one of two groups: control and intervention. In both groups, VC was assessed as baseline (VC1) and again 15 days later (VC2). Positive reinforcement was provided only to patients in the intervention group and only during the determination of VC2. Results: There were no significant differences between the groups regarding the baseline characteristics. Females predominated in both groups. There was an increase in VC2 in both groups (p < 0.01), and VC2 was higher in the intervention group than in the control group (p < 0.01). Conclusions: These findings demonstrate the importance of using the behavioral strategy in combination with traditional practice in order to obtain better results. The use of positive reinforcement during the determination of VC has proven to be an effective, simple and easily applied strategy.

Keywords: Vital capacity; Reinforcement, verbal; Respiratory function tests.

Objective: Few studies have evaluated the variability of the perception of dyspnea in healthy subjects. The objective of this study was to evaluate the variability of the perception of dyspnea in healthy subjects during breathing against increasing inspiratory resistive loads, as well as to assess the association between the level of perception of dyspnea and the level of physical activity. Methods: This was a cross-sectional study involving healthy individuals 16 years of age or older. Subjects underwent inspiratory resistive loading testing, in which the level of perception of dyspnea was quantified with the modified Borg scale. We also determined body mass indices (BMIs), assessed maximal respiratory pressures, performed pulmonary function tests, applied the international physical activity questionnaire (IPAQ)-long form, and conducted six-minute walk tests (6MWTs). The level of perception of dyspnea was classified as low (Borg score < 2), intermediate (Borg score, 2-5), or high (Borg score > 5). Results: We included 48 healthy subjects in the study. Forty-two subjects completed the test up to a load of 46.7 cmH2O/L/s. The level of perception of dyspnea was classified as low, intermediate, and high in 13, 19, and 10 subjects, respectively. The level of perception of dyspnea was not significantly associated with age, gender, BMI, IPAQ-long form score, maximal respiratory pressures, or pulmonary function test results. Conclusions: The scores for perceived dyspnea induced by inspiratory resistive loading in healthy subjects presented wide variability. The perception of dyspnea was classified as low in 31% of the subjects, intermediate in 45%, and high in 24%. There was no association between the level of perception of dyspnea and the level of physical activity (IPAQ or six-minute walk distance).

Keywords: Dyspnea; Respiratory function tests; Exercise test.

The aim of the study was to evaluate the performance of sniff nasal inspiratory pressure (SNIP) and MIP in individuals with spinal cord injury. We evaluated 26 patients with spinal cord injury. Mean FVC in those with tetraplegia was 52 ± 19% of predicted, compared with 78 ± 23% of predicted in those with paraplegia (p < 0.05). In contrast, the percentage of predicted SNIP was lower in those with tetraplegia than in those with paraplegia (p < 0.05). In all participants, SNIP correlated significantly with the level of the injury (r = 0.489; 95% CI: 0.125‑0.737). The impact that the greater discriminatory power of SNIP has on the diagnosis of impaired pulmonary function in spinal cord-injured patients should be investigated further.

Keywords: Spinal cord injuries; Respiratory function tests; Respiratory muscles; respiratory paralysis.

Objective: To derive reference values for healthy white Brazilian adults who have never smoked and to compare the obtained values with reference values derived by Crapo and by Neder. Methods: Reference equations by quantile regressions were derived in 122 men and 122 women, non-obese, living in seven cities in Brazil. Age ranged from 21 to 92 years in women and from 25 to 88 years in men. Lung function tests were performed using SensorMedics automated body plethysmographies according ATS/ERS recommendations. Lower and upper limits were derived by specific equations for 5 and 95 percentiles. The results were compared to those suggested by Crapo in 1982, and Neder in 1999. Results: Median values for total lung capacity (TLC) were influenced only by stature in men, and by stature and age in women. Residual volume was influenced by age and stature in both genders. Weight was directly related to inspiratory capacity and inversely with functional residual capacity and expiratory reserve volume in both genders. A comparison of observed TLC data with values predicted by Neder equations showed significant lower values by the present data. Mean values were similar between data from present study and those derived by Crapo. Conclusion: New predicted values for lung volumes were obtained in a sample of white Brazilians. The values differ from those derived by Neder, but are similar to those derived by Crapo.

Keywords: Pulmonary volumes; Pulmonary function tests; Reference values; Pulmonary plethysmography

Objective: To investigate four parameters defining maximal respiratory pressures and to evaluate their correlations and agreements among those parameters for the determination of MIP and MEP. Methods: This was a cross-sectional study involving 49 healthy, well-nourished males and females. The mean age was 23.08 ± 2.5 years. Measurements were carried out using a pressure transducer, and the estimated values for the parameters peak pressure (Ppeak), plateau pressure (Pplateau), mean maximal pressure (Pmean), and pressure according to the area (Parea) were determined with an algorithm developed for the study. To characterize the study sample, we used descriptive statistics, followed by repeated measures ANOVA and Bonferroni post hoc test or by the Friedman test and the Wilcoxon post hoc test, as well as by Pearson's or Spearman's correlation coefficients, depending on the normality of the data. The agreement between the variables was assessed with Bland  Altman plots. Results: There were significant differences among all of the parameters studied for MIP (Ppeak = 95.69 ± 27.89 cmH2O; Parea = 88.53 ± 26.45 cmH2O; Pplateau = 82.48 ± 25.11 cmH2O; Pmean = 89.01 ± 26.41 cmH2O; p < 0.05 for all) and for MEP (Ppeak = 109.98 ± 40.67 cmH2O; Parea = 103.85 ± 36.63 cmH2O; Pplateau = 98.93 ± 32.10 cmH2O; Pmean = 104.43 ± 36.74 cmH2O; p < 0.0083 for all). Poor agreement was found among almost all of the parameters. Higher pressure values resulted in larger differences between the variables. Conclusions: The maximal respiratory pressure parameters evaluated do not seem to be interchangeable, and higher pressure values result in larger differences among the parameters.

Keywords: Respiratory system; Muscle strength; Respiratory function tests.

Objective: To evaluate the electromyographic activity (EA) of sternocleidomastoid (SCM) and scalene muscles during and after the use of expiratory positive airway pressure (EPAP) in patients with COPD. Methods: This was a clinical single-blind trial involving 13 healthy subjects as controls and 12 patients with stable COPD. At baseline, we determined EA during spontaneous respiration, lung function parameters, and respiratory muscle strength. Subsequently, EPAP at 15 cmH2O was applied by means of a face mask for 25 min, during which the EA of the SCM and scalene muscles was recorded every 5 min. A final record was obtained 10 min after the mask removal. Results: We found that the behavior of the EA of SCM and scalene muscles was comparable between the controls and the COPD patients (p = 0.716 and p = 0.789, respectively). However, during the use of EPAP, both muscles showed a trend toward an increase in the EA. In addition, there was a significant decrease in the EA of the SCM between the baseline and final measurements (p = 0.034). Conclusions: The use of EPAP promoted a significant reduction in the EA of the SCM in the controls and in the patients with stable COPD. However, this did not occur regarding the EA of the scalene muscle.

Keywords: Electromyography; Respiratory muscles; Pulmonary disease, chronic obstructive; Positive-pressure respiration.

Objective: To develop reference equations for the Glittre Activities of Daily Living test (Glittre ADL-test) on the basis of anthropometric and demographic variables in apparently healthy individuals. A secondary objective was to determine the reliability of the equations in a sample of COPD patients. Methods: This was a cross-sectional study including 190 apparently healthy individuals (95 males; median age, 54.5 years [range, 42-65]; median FEV1 = 97% [range, 91-105.2]; and median FVC = 96% [range, 88.5-102]) recruited from the general community and 74 COPD patients (55 males; mean age, 65 ± 8 years; body mass index [BMI] = 25.9 ± 4.7 kg/m2; FEV1 = 36.1 ± 14.1%; and FVC = 62.7 ± 16.1%) recruited from a pulmonary rehabilitation center. Results: The mean time to complete the Glittre ADL-test was 2.84 ± 0.45 min. In the stepwise multiple linear regression analysis, age and height were selected as Glittre ADL-test performance predictors, explaining 32.1% (p < 0.01) of the total variance. Equation 1 was as follows: Glittre ADL-testpredicted = 3.049 + (0.015 × ageyears) + (−0.006 × heightcm). Equation 2 included age and BMI and explained 32.3% of the variance in the test, the equation being as follows: Glittre ADL-testpredicted = 1.558 + (0.018 × BMI) + (0.016 × ageyears). Conclusions: The reference equations for the time to complete the Glittre ADL-test were based on age, BMI, and height as independent variables and can be useful for predicting the performance of adult individuals. The predicted values appear to be reliable when applied to COPD patients.

Keywords: Activities of daily living; Exercise test; Reference values.

Objective: To clarify whether, in healthy individuals, practicing yoga can modify maximal inspiratory pressure and spirometric indices when compared with the practice of aerobic exercise. Methods: A controlled clinical trial. A total of 31 healthy volunteers were allocated to practice aerobic exercise (n = 15) or to practice yoga (n = 16). Those in the first group served as controls and engaged in aerobic exercise for 45-60 minutes, twice a week for three months. Those in the second group practiced selected yogic techniques, also in sessions of 45-60 minutes, twice a week for three months. Forced vital capacity, forced expiratory volume in one second and maximal inspiratory pressure were measured before and after the three months of training. Results: No significant alterations were seen in the spirometric indices. A slight, although not significant, improvement in maximal inspiratory pressure was seen in both groups. However, there was a significant difference, seen in both genders, between the absolute delta (final value minus baseline value) of maximal inspiratory pressure for the group practicing yoga and that obtained for the group engaging in aerobic exercise (males: 19.5 cm H2O versus 2.8 cm H2O, p = 0.05; females: 20 cm H2O versus 3.9 cm H2O, p = 0.01). Conclusion: Neither yoga nor aerobic exercise provided a statistically significant improvement in maximal inspiratory pressure after three months. However, the absolute variation in maximal inspiratory pressure was greater among those practicing yoga.

Keywords: Yoga; Exercise; Respiratory muscles; Respiratory function tests; Maximal voluntary ventilation; Spirometry; Inspiratory capacity/physiology

Objective: To determine whether inspiratory muscle training can increase strength and endurance of these muscles in quadriplegic patients. Methods: Eight quadriplegic patients (7 males and 1 female) with injury to the lower cervical spine (segments C4-C7) were submitted to inspiratory muscle training with a threshold inspiratory muscle trainer adjusted to 30% of MIP. The training sessions were carried out with the patients in a sitting position, 5 days a week for 8 weeks. Endurance time, MIP, MEP and FVC were determined at baseline, week 4 and week 8. Results: In comparison with the mean baseline value, there was an increase in MIP, measured in the sitting position, at weeks 4 and 8 (−83.0 ± 18.9 cmH2O vs. −104.0 ± 19.4 cmH2O and −111.3 ± 22.7 cmH2O). There was an increase in MEP, also in the sitting position, at week 4 (from 36.8 ± 8.1 to 42.6 ± 8.8 cmH2O). There was an improvement in FVC at week 4 (from 2.1 ± 0.8 to 2.5 ± 0.6 L, representing an increase of 24 ± 22%). Although there was an increase in endurance (sitting) at week 8, the difference was not significant in comparison with the baseline value (29.8 ± 21.0 vs. 35.9 ± 15.5 min, an increase of 173 ± 233%). Conclusions: Quadriplegic patients can benefit from training at low loads (30% of MIP), which can improve inspiratory muscle strength, FVC and expiratory muscle performance.

Keywords: Respiratory mechanics; Quadriplegia; Breathing exercises.

Objective: To establish reference values for cellularity in induced sputum samples collected from healthy adults. Methods: Induced sputum samples were obtained from 88 healthy adult never-smokers (39 males). The mean age was 36 years (range, 18-68 years). The participants had been residing in the city of Florianópolis, Brazil (a medium-sized non-industrial city) for at least two years. After the samples had been processed, we obtained total and differential cell counts. Results: The mean total cell count was 4.8 ± 4.2 × 106 cells/g. There was a predominance of macrophages (mean, 77.5 ± 14.7%) and neutrophils (mean, 23.4 ± 14.3%). Eosinophils were virtually absent (mean, 0.1 ± 0.3%). Lymphocytes and bronchial epithelial cells were scarce. Neither age nor atopy had any effect on the total or differential cell counts. Conclusions: In the induced sputum of this healthy adult population, macrophages and neutrophils predominated. However, the proportion of neutrophils was lower than that reported in previous studies, which suggests that reference values might vary depending on geographic location.

Keywords: Sputum; Reference values; Brazil.