Incremental Ramp Load Protocol to Assess Inspiratory Muscle Endurance in Healthy Individuals: Comparison with Incremental Step Loading Protocol.

INTRODUCTION: Protocols for obtaíníng the maxímum threshold pressure have been applied wíth límited precision to evaluate ínspiratory muscle endurance. In thís sense, new protocols are needed to allow more relíable measurements. The purpose of the present study was to compare a new incremental ramp load protocol for the evaluation of ínspíratory muscle endurance wíth the most used protocol in healthy indíviduals. METHODS: This was a prospective cross-sectional study carried out ín a síngle center. Nínety-two healthy indíviduals (43 men [22 ± 3 years] and 49 women [22 ± 3 years]) were randomly allocated to perform: (i) íncremental ramp load protocol and (íí) íncremental step loadíng protocol. The sustained pressure threshold (or maximum threshold pressure), maximum threshold pressure/dynamic strength índex ratío, time untíl task faílure, as well as dífference between the mean heart rate of the last five mínutes of baselíne and the peak heart rate of the last 30 seconds of each protocol were measured. RESULTS: Incremental ramp load protocol wíth small íncreases in the load and starting from mínímum values of strength index was able to evaluate the inspiratory muscle endurance through the maxímum threshold pressure of healthy indívíduals. CONCLUSION: The present study suggests that the íncremental ramp load protocol is able to measure maximum threshold pressure in a more thorough way, wíth less progression and greater accuracy in the load stratification compared to the límited incremental step loading protocol and with a safe and expected cardiovascular response in healthy individuals.

Incremental Ramp Load Protocol to Assess Inspiratory Muscle Endurance in Healthy Individuals: Comparison with Incremental Step Loading Protocol

ABSTRACT Introduction: Protocols for obtaining the maximum threshold pressure have been applied with limited precision to evaluate inspiratory muscle endurance. In this sense, new protocols are needed to allow more reliable measurements. The purpose of the present study was to compare a new incremental ramp load protocol for the evaluation of inspiratory muscle endurance with the most used protocol in healthy individuals. Methods: This was a prospective cross-sectional study carried out in a single center. Ninety-two healthy individuals (43 men [22 ± 3 years] and 49 women [22 ± 3 years]) were randomly allocated to perform: (i) incremental ramp load protocol and (ii) incremental step loading protocol. The sustained pressure threshold (or maximum threshold pressure), maximum threshold pressure/dynamic strength index ratio, time until task failure, as well as difference between the mean heart rate of the last five minutes of baseline and the peak heart rate of the last 30 seconds of each protocol were measured. Results: Incremental ramp load protocol with small increases in the load and starting from minimum values of strength index was able to evaluate the inspiratory muscle endurance through the maximum threshold pressure of healthy individuals. Conclusion: The present study suggests that the incremental ramp load protocol is able to measure maximum threshold pressure in a more thorough way, with less progression and greater accuracy in the load stratification compared to the limited incremental step loading protocol and with a safe and expected cardiovascular response in healthy individuals.

Concurrent Validity of the Static and Dynamic Measures of Inspiratory Muscle Strength: Comparison between Maximal Inspiratory Pressure and S-Index.

OBJECTIVE: To verify the concurrent validity between the inspiratory muscle strength (IMS) values obtained in static (maximal inspiratory pressure [MIP]) and dynamic (S-Index) assessments. METHODS: Healthy individuals were submitted to two periods of evaluation: i) MIP, static maneuver to obtain IMS, determined by the Mueller's maneuver from residual volume (RV) until total lung capacity (TLC); ii) and S-Index, inspiration against open airway starting from RV until TLC. Both measures were performed by the same evaluator and the subjects received the same instructions. Isolated maneuvers with differences < 10% were considered as reproducible measures. RESULTS: Data from 45 subjects (21 males) were analyzed and that showed statistical difference between MIP and S-Index values (133.5 ± 33.3 and 125.6 ± 32.2 in cmH2O, respectively), with P=0.014. Linear regression showed r2=0.54 and S-Index prediction formula = 39.8+(0.75×MIP). Pearson's correlation demonstrated a strong and significant association between the measures with r=0.74. The measurements showed good concordance evidenced by the Bland-Altman test. CONCLUSION: S-Index and MIP do not present similar values since they are evaluations of different events of the muscular contraction. However, they have a strong correlation and good agreement, which indicate that both are able to evaluate the IMS of healthy individuals.

Concurrent validity of the static and dynamic measures of inspiratory muscle strength: comparison between maximal inspiratory pressure and s-index

Abstract Objective: To verify the concurrent validity between the inspiratory muscle strength (IMS) values obtained in static (maximal inspiratory pressure [MIP]) and dynamic (S-Index) assessments. Methods: Healthy individuals were submitted to two periods of evaluation: i) MIP, static maneuver to obtain IMS, determined by the Mueller's maneuver from residual volume (RV) until total lung capacity (TLC); ii) and S-Index, inspiration against open airway starting from RV until TLC. Both measures were performed by the same evaluator and the subjects received the same instructions. Isolated maneuvers with differences < 10% were considered as reproducible measures. Results: Data from 45 subjects (21 males) were analyzed and that showed statistical difference between MIP and S-Index values (133.5 ± 33.3 and 125.6 ± 32.2 in cmH2O, respectively), with P=0.014. Linear regression showed r2=0.54 and S-Index prediction formula = 39.8+(0.75×MIP). Pearson's correlation demonstrated a strong and significant association between the measures with r=0.74. The measurements showed good concordance evidenced by the Bland-Altman test. Conclusion: S-Index and MIP do not present similar values since they are evaluations of different events of the muscular contraction. However, they have a strong correlation and good agreement, which indicate that both are able to evaluate the IMS of healthy individuals.

Variabilidade da frequência cardíaca com a mudança postural na insuficiência cardíaca crônica / Heart rate variability in patients with chronic heart failure after postural changes

Introdução: A variabilidade da frequência cardíaca (VFC) é uma alternativa de baixo custo para a avaliação da modulação autonômica cardíaca que é relacionada com os indivíduos com insuficiência cardíaca (IC) crônica devido ao desequilíbrio simpático-vagal característico dessa patologia. Objetivo: Comparar a VFC de pacientes com IC crônica e indivíduos saudáveis na mudança da posição supina para sentado. Métodos: Dezenove indivíduos subdivididos em dois grupos: 10 pacientes com o diagnóstico de IC crônica (GI) com 62 ± 6 anos de idade e nove participantes saudáveis (GC) com 64 ± 5 anos. Os intervalos R-R foram captados através do eletrocardiograma nas posições supina e sentada, por 10 minutos em cada condição. Os dados foram analisados nos domínios do tempo e da frequência. Teste t de Student pareado ou de Wilcoxon foram usados para as comparações intragrupos. Nas comparações intergrupos foi aplicado o teste t não pareado ou de Mann Whitney (p <0,05). Resultados: Os indivíduos com IC crônica apresentaram menores valores do SDNN (sentado 18,4 ± 4,5 vs. 28,4 ± 7,6; supina 23,3 ± 5 vs. 32,1 ± 12,4) e do RMSSD (sentado 12,2 ± 2,6 vs. 20,0 ± 6,8; supina 14,5 ± 4,3 vs. 21,3 ± 10) quando comparados ao controle. Após a mudança postural, verificou-se alteração significativa somente no SDNN do grupo IC crônica (23,3 ± 5 vs. 18,4 ± 4,5). Conclusão: Os indivíduos do grupo IC crônica apresentaram VFC reduzida em comparação a indivíduos saudáveis da mesma idade, porém ainda assim foram capazes de realizar a modulação simpático-vagal após a mudança postural

Introduction: Heart rate variability (HRV) is a low-cost alternative for the evaluation of autonomic cardiac modulation, which is related to individuals with chronic heart failure (CHF) due to the sympathovagal imbalance that is characteristic of this pathology. Objective: to compare HRV in patients with CHF and healthy subjects after transition from a supine to a sitting position. Methods: We recruited 19 subjects, who were divided into two groups: 10 patients with a diagnosis of CHF (IG) aged 62 ± 6 years; and nine healthy participants (CG) aged 64 ± 5 years. The RR intervals were captured by electrocardiogram in the supine and sitting positions, for 10 minutes in each condition. The data were analyzed in the domains time and frequency. The paired Student-t or Wilcoxon tests were used for the intragroup comparisons. For the intergroup comparisons, the unpaired t-test or Mann Whitney tests were used (p<0.05). Results: The individuals with CHF showed lower SDNN values (sitting 18.4 ± 4.5 vs. 28.4 ± 7.6, and supine 23.3 ± 5 vs. 32.1 ± 12.4) and lower RMSSD values (sitting 12.2 ± 2.6 vs. 20.0 ± 6.8; and supine 14.5 ± 4.3 vs. 21.3 ± 10) when compared to the control. After the postural change, a significant change occurred only in the SDNN of the chronic CHF group (23.3 ± 5 vs. 18.4 ± 4.5). Conclusion: The individuals of the CHF group showed reduced HRV compared to healthy individuals of the same age, but were still able to perform sympathetic-vagal modulation after the change in posture