Rev Bras Fisiol exerc 2021;20(3):315-24

doi: 10.33233/rbfex.v20i3.4244

ORIGINAL ARTICLE

Concurrent validity and intrarater reliability of the Glittre ADL-Test in obstructive sleep apnea

Validade concorrente e reprodutibilidade intra-avaliador do teste de AVD-Glittre na apneia obstrutiva do sono

 

José Carlos Nogueira Nóbrega Júnior¹, Armèle Dornelas de Andrade2, Adília Karoline Ferreira Souza3, Maria Inês Remígio de Aguiar2, Rodrigo Pinto Pedrosa4, Maria do Socorro Brasileiro-Santos5, Anna Myrna Jaguaribe de Lima6

 

1Facottur, Olinda, PE, Brazil

2Universidade Federal de Pernambuco, Recife, PE, Brazil

3Universidade Estadual da Paraíba, Campina Grande, PB, Brazil

4Pronto Socorro Cardiológico de Pernambuco (PROCAPE), Universidade de Pernambuco, Recife, PE, Brazil

5Universidade Federal da Paraíba, João Pessoa, PB, Brazil

6Universidade Federal Rural de Pernambuco, Recife, PE, Brazil

 

Received: 30 June 2020; Accepted: 27 January 2021.

Correspondence: Anna Myrna Jaguaribe de Lima, Universidade Federal Rural de Pernambuco, Rua Dom Manuel de Medeiros, s/n, Dois Irmãos, 52171-900 Recife PE

 

José Carlos Nogueira Nóbrega Júnior: carlos_noobrega@hotmail.com

Armèle Dornelas de Andrade: armeledornelas@hotmail.com

Adília Karoline Ferreira Souza: adiliakfsfisio@gmail.com

Maria Inês Remígio de Aguiar: miremigio@yahoo.com.br

Rodrigo Pinto Pedrosa: rppedrosa@terra.com.br

Maria do Socorro Brasileiro-Santos: sbrasileiro@yahoo.com

Anna Myrna Jaguaribe de Lima: anna.myrna@ufrpe.br

 

Abstract

Objective: To evaluate the concurrent validity and intrarater reliability of the Glittre-ADL test to determine exercise capacity in subjects with obstructive sleep apnea (OSA). Methods: Twenty-two (22) subjects with mild to severe OSA (50.7 ± 11.2 years, 32.0 ± 4.0 kg/m2) performed the Glittre-ADL test and the cardiopulmonary exercise testing (CPET). The tests were carried out in two different days, twice a day, and the order was determined by randomization. Results: The maximum HR (HRmax) in the Glittre-ADL test was 130.6 ± 13.3 bpm. Regarding the variables related to CPET, the volunteers had values of maximal oxygen consumption (VO2max) of 25.4 ± 5.3 ml/kg/min, VO2 on the first threshold of 19.4 ± 3.9 ml/kg/min and maximum HR of 161.3 ± 15.2 bpm. A moderate negative correlation was found between the Glittre-ADL test performance time and VO2max (r = -0.424; p = 0.049). Excellent agreement and consistency between measurements was observed in analyzing the test-retest reliability of the total performance time of the Glittre-ADL test (intraclass correlation coefficient (ICC) = 0.865, 95% CI: 0.379-0.965 (p ≤ 0.0001). Conclusion: According to the results of the present study, Glittre-ADL test is reliable and valid for evaluating functional exercise capacity in patients with moderate and severe OSA. Furthermore, it also could be considered as a submaximal clinical exercise tolerance test for this population.

Keywords: obstructive sleep apnea; exercise tolerance; exercise test.

 

Resumo

Objetivo: O objetivo deste trabalho foi testar a hipótese que o teste de AVD-Glittre (TGlittre) tem validade concorrente e reprodutibilidade intra-avaliador em indivíduos com apneia obstrutiva do sono (AOS). Métodos: Foram avaliados 22 indivíduos, de ambos os sexos, com diagnóstico AOS. O TGlittre e o teste de esforço cardiopulmonar (TECP) foram realizados em dois dias diferentes, duas vezes cada, e a ordem era determinada por randomização. Resultados: A FC máxima (FCmáx) obtida no TGlittre foi de 130,6 ± 13,3 bpm e o tempo total para a realização do teste foi de 3,4 ± 0,5 min. Sobre as varáveis analisadas no TECP, foram obtidos os seguintes valores: consumo máximo de oxigênio (VO2máx) = 2,4 ± 5,3 ml/kg/min, VO2 no primeiro limiar = 19,4 ± 3,9 ml/kg/min, FCmáx = 161,3 ± 15,2 bpm e o tempo total de realização do teste foi de 8,3 ± 1,6 min. Uma correlação negativa moderada foi verificada entre o tempo de realização do TGlittre e VO2max (r = -0,424; p = 0,049). Na análise da confiabilidade teste-reteste do tempo total de realização do TGlittre, foi observada uma excelente concordância e consistência entre as medidas (coeficiente de correlação intraclasse (CCI) = 0,865; IC95%: 0,379-0,965 (p ≤ 0,0001). Conclusão: O teste de TGlittre é válido e reprodutível na AOS. Além disso, é um teste de intensidade submáxima, fácil aplicação e baixo custo, que pode ser utilizado em larga escala.

Palavras-chave: apneia obstrutiva do sono; tolerância ao exercício; teste de esforço.

 

Introduction

 

Obstructive sleep apnea (OSA) is characterized by recurrent hypoxia/reoxygenation patterns that cause oxidative stress and muscle injury [1,2,3]. These bioenergetic and structural changes in skeletal muscles are responsible for generalized fatigue and impaired functional exercise capacity in these individuals [3,4]. In addition, OSA may cause respiratory muscle weakness, thus promoting activation of cardiovascular reflexes. The muscle abnormalities that commonly occur in OSA associated with intermittent blood gas disorders compromise the integrity of the cardiorespiratory system, triggering the decline of exercise tolerance [5,6,7,8].

Thus, assessing functional exercise capacity provides important information for the diagnosis and prognosis of cardiopulmonary function through the behavior of metabolic, cardiac, and respiratory systems during the cardiopulmonary exercise testing (CPET) [9]. Despite CEPT is the gold standard to assess exercise tolerance, the cost is high, and it requires specialized and trained personnel. Furthermore, CEPT is a maximum exercise test and could be not well-tolerated in elderly with comorbidities [10]. On the other hand, field tests appear as a less strenuous alternative. In addition to presenting good correlation with the activities of daily life, they are low cost, simply executed and easily reproducible [11,12].

In this context, the Glittre-ADL test has been able to reflect the functional limitations in studies with healthy subjects [13] and those affected by varied conditions such as COPD [14,15], cardiovascular diseases [16] and obesity [17].

Regarding OSA, there are still no reports in the literature on the use of the Glittre-ADL test to determine exercise tolerance in these subjects. Therefore, the objective of this study was to test the hypothesis that the Glittre-ADL test has concurrent validity and reliability in subjects with OSA.

 

Methods

 

Sample

 

This is a cross-sectional study and was approved by the Human Research Ethics Committee of the Federal University of Pernambuco (UFPE) in accordance with the resolution 466/12 CNS (No: 1068362). All volunteers included in the study were informed about the research and signed an informed consent form, designed by the principal investigator.

Volunteers were recruited from the Cardiologic Emergency Hospital of Pernambuco (PROCAPE) based on the evaluation of 428 individual (medical) records. All volunteers underwent a polysomnography (ApneaLink™-Resmed) for OSA diagnosis. Patients aged between 30 years and 65 years, with AHI (=Apnea Hypopnea Index) ≥ 15 events/hour (moderate to severe OSA), without a history of musculoskeletal, pulmonary or cardiac diseases and with BMI ≤ 39.9 kg/m2 were included in the study.

An independent evaluator who did not participate in patient recruitment or in the testing performed the randomization for the test order, using the randomized.com software.

 

Cardiopulmonary exercise test (CPET)

 

To evaluate the functional exercise capacity, CPET was performed using a treadmill ramp protocol (Centurium 300, Micromed, Brazil) and ErgoPCElite® software associated with an electrocardiogram (Micromed Brazil) with twelve derivations. In this protocol, the system suggests the velocity and inclination to be increased, so that the patient reaches their maximum oxygen consumption (VO2max) within 10 minutes. The respiratory variables during exercise were obtained under standard conditions of temperature (18-22ºC), pressure and humidity (50-70%), and collected using a face mask attached to a gas analyzer (Cortex - Metalyzer II - Germany). The patient was instructed not to verbally communicate during the examination, informing their levels of fatigue through manual gestures and requesting the end of the examination only at the moment of exhaustion. The test was considered maximal when the respiratory exchange ratio (R) was ≥ 1.1 [18].

 

Glittre-ADL Test

 

The patients were instructed to walk 10 meters with a backpack (5.0 kg for men and 2.5 kg for women). The circuit consisted of 5 laps starting with the patient sitting on a chair, and upon receiving the command they would get up and walk fast up the middle of the course and go up and down a two-step staircase (17 cm height x 27 cm deep). Then they would continue (walking) until the end of the circuit, where there was a shelf containing three objects (1 kg each) on the highest shelf. They should move them one by one to the middle shelf (waist height), and finally to the lowest shelf (floor height). Next, the objects were replaced on the middle shelf and then on the highest shelf. The patient re-did the course, sitting, getting up and repeating the circuit. Heart rate (Frequency-Polar) and peripheral oxygen saturation (Oximeter-Pulse Oximeter PM 50) were monitored at each lap. Blood pressure and the subjective perception of effort (modified BORG scale) were measured at baseline at the end and after two minutes of recovery [19].

Two Glittre-ADL tests were performed within a maximum interval of one week, and with an interval of at least twenty-four hours between them. The data obtained for the fastest timed test were used for analyzing the physiological responses. The formula used to calculate the estimated HRmax was: HRmax.estimated=208-(0.7x age), described by Tanaka H, Monahan K and Seals D [20].

 

Data analysis

 

Data were analyzed using the SPSS software version 20.0. The Spearman correlation test was used for the concurrent validation of the Glittre-ADL test, and the intraclass correlation coefficient (ICC) and the Bland-Altman method were used for the reliability evaluation. The results were presented as mean and standard deviation, considering p < 0.05 as the level of statistical significance.

 

Results

 

In figure 1 is showed process of recruitment, allocation, follow-up and analysis of the participants.

 

 

Figure 1 - Flow diagram of patient recruitment and progress

 

Twenty-two patients were evaluated (14 males (64%) and 8 females). The anthropometric and clinical characteristics of the sample are shown in Table I. The sample mostly consisted of individuals with OSA classified as severe (59.1%).

 

Table I - Characteristics of the sample

 

n = sample size; M = males; F = females; BMI =body mass index; AHI = apnea-hipopnea index. Data are reported as mean ± standard deviation and percentage

 

A negative and moderate correlation (r = -0.424; p = 0.049) was found in figure 2 between the VO2max obtained on CPET and the performance time for the Glittre-ADL test.

 

 

Figure 2 - Correlation plot between maximal oxygen consumption and Glittre-ADL time test (r = -0,424; p = 0,049)

 

Table II shows the cardiorespiratory responses obtained on the maximum CPET and on the submaximal Glittre-ADL test. The volunteers presented VO2max values of 25.4 ± 5.3 ml/kg/min, VO2 at the first threshold of 19.4 ± 3.9 ml/kg/min and HRmax of 161.3 ± 15.2 bpm. The HRmax was 130.6 ± 13.3 bpm for the Glittre-ADL test and the HRmax (%predicted) for the Glittre-ADL test was 80.9 ± 6.9% of the HRmax obtained on the CPET.

 

Table II - Results of cardiopulmonary exercise testing and Glittre-ADL test

 

CEPT = cardiopulmonary exercise testing; VO2max = maximal oxygen consumption; VO2 = oxygen consumption; HRmax = maximum heart rate; SBPmax = maximum systolic blood pressure; SBPrecovery1’ = systolic blood pressure in the first minute of the recovery; SBPrecovery2’ = systolic blood pressure in the second minute of the recovery; DBPmax = maximum diastolic blood pressure; DBPrecovery1’ = diastolic blood pressure at the first minute of the recovery; DBPrecovery1’ = diastolic blood pressure in the second minute of the recovery. Data are reported as mean and standard deviation

 

In the test-retest reliability for the total time to perform the Glittre-ADL test, the intraclass correlation coefficient (ICC) presented high reliability (0.865, 95% CI = 0.379-0.965, p < 0.0001) (Figure 3).

 

 

Figure 3 - Bland-Altman plot of agreement between test and retest of Glittre-ADL test

 

Discussion

 

This is the first study to assess the concurrent validity and reliability of the Glittre-ADL test in OSA patients. The results showed a moderate negative correlation between the performance time of the Glittre-ADL test and VO2max, showing an association between the direct measurement of functional exercise capacity through the CPET, and the indirect measurement of functional exercise capacity through the Glittre-ADL test. Moreover, the test-retest reliability found of the Glittre-ADL was excellent, showing good agreement and consistency between the intra-rater measurements.

In the present study, the Glittre-ADL test can be considered an alternative to evaluate exercise tolerance, since a moderate concurrent validity was found between the Glittre-ADL test performance time and the VO2max obtained on the CPET. The Glittre-ADL test has already been used to assess exercise capacity in healthy subjects and in diseases such as COPD [14,15], heart failure [16] and obesity [17]. Although all conclude that the Glittre-ADL test may be useful in clinical practice to quantify functional capacity and functional capacity to exercise in these populations, only Karloh et al. [15] have compared their results with direct VO2max measurement.

The study conducted by Reis et al. [13] evaluated the Glittre-ADL test total performance time in a sample of healthy adult subjects and found that the mean time to finish the test was 2.62 ± 0.34 min. In the present study, the time was 3.44 ± 0.54 min. The longer time demanded by patients with OSA for completing the test can be attributed to the systemic repercussions caused by reoccurring episodes of hypoxia/reoxygenation present in the disease. The presence of associated comorbidities such as hypertension and diabetes which may also limit performance on tests that assess functional exercise capacity should also be evaluated. Silva et al. [21] determinated the validity and the reliability of the Glittre-ADL in subjects with Parkinson disease and observed that the time to execute the Glittre-ADL test was 3.69 min (2.96-4.48 min).

In this study, the HRmax obtained during the Glittre-ADL test was 130.6 ± 13.3 bpm, which corresponds to 80.9 ± 6.9% of the HRmax observed on the CPET, characterizing the Glittre-ADL test as a submaximal test in our sample. The evaluation of the exercise tolerance in clinical settings is related to the test type choice. Submaximal tests are low-cost, simple to apply, and it is possible to perform them in regular facilities with easy access to the professional and the patient who needs to perform it, thus better representing the daily activities of the individual [22]. In addition, OSA is a disease commonly associated with cardiovascular comorbidities that may hinder the performance of maximal stress testing by these patients. Thus, submaximal exertion tests appear as a safe alternative for data collection for exercise prescription and follow-up of the evolution in these patients.

Regarding the hemodynamic responses of the Glittre-ADL test in the present study, we can consider that the test promoted a submaximal physiological stress, since systolic (SBP) and diastolic blood pressure (DBP) were moderately elevated during the recovery period. Evaluating subjects with OSA submitted to CPET, Hargens et al. [23] found higher values of systolic (196.9 ± 7.0 mmHg) and diastolic (90.7 ± 3.1 mmHg) blood pressure in the recovery period due to the maximum characteristic of the applied test. In our study, the performance of a submaximal test such as the Glittre-ADL test led to milder SBP and DBP values in the recovery period.

Other submaximal tests have already been used to assess exercise tolerance in subjects with OSA [24,25,26]. Billings et al. [27] used the incremental shuttle walk test (ISWT) to determine exercise capacity in patients with moderate to severe OSA treated with Continuous Positive Airway Pressure (CPAP). They concluded that the ISWT is safe, well-tolerated and easy to apply in this population. Masa et al. [28] used the 6MWT to assess exercise capacity in subjects with severe OSA treated with CPAP for two months. Similarly, Goel et al. [29] also used the 6MWT to assess exercise capacity in subjects with moderate and severe OSA. Both studies using the 6MWT found that this test is indicated to assess functional capacity in individuals with OSA, requiring few resources and without significant risks to the participants.

The present study showed high reliability and excellent agreement between the measurements of the two performed Glittre-ADL tests. When comparing the total test time of both tests, no differences were observed between them, demonstrating that there was no learning effect, and therefore there is only the need to perform a single test for the clinical practice. A study carried out by Santos et al. [30] in patients with chronic obstructive pulmonary disease (COPD) presented similar results with an ICC of 0.97, also indicating high reliability between the measurements. Also, Reis et al. [13] evaluated the Glittre-ADL total time in a sample composed of healthy adults and found an ICC of 0.88 (p < 0.05) between the times of the two Glittre-ADL measurements, corroborating the results obtained in our study.

 

Clinical implications

 

Submaximal field tests are a widely used option in daily clinical practice for the evaluation of exercise capacity. This type of test allows for an efficient and simpler approach, requiring fewer resources when compared to maximum effort tests. They can be performed in any environment with the available space, making it possible to evaluate and obtain data for exercise prescription. In addition to its easy reproduction, the Glittre-ADL test has been used due to being able to efficiently evaluate efforts, generating lower cardiovascular physiological stress, but enough so that we can get an adequate evaluation of the submaximal functional capacity of exercise for individuals with OSA.

In this context, the Glittre-ADL test is an interesting and viable option for assessing exercise tolerance in OSA valid, independent of the associated comorbidities. This kind of test promotes less physiological stress and therefore, can be considered safe and not overloading the subjects.

 

Limitations of the study

 

The limitations of the present study include the absence of subjects with mild OSA, as the study just included patients with moderate and severe OSA. Mild sleep apnea patients could have less effects of hypoxia and the adverse impact on the cardiovascular system and in exercise tolerance of these patients with a low AHI may be less pronounced.

 

Conclusion

 

Therefore, according to the results of the present study, the Glittre-ADL test shows concurrent validity and excellent intrarater reliability in OSA patients.

 

Conflict of interest

No conflict of interest with relevant potential.

 

Financing source

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) – Finance Code 001.

 

Author’s contributions

Conception and design of study: Lima AMJ. Acquisition, analysis and/or interpretation of data: Souza, AKF, Aguiar MIR, Nóbrega-Júnior JCN; Lima AMJ, Brasileiro-Santos MS; Drafting the manuscript: Nóbrega-Júnior JCN, Lima AMJ; Revising the manuscript critically for important intellectual content: Pedrosa RP, Andrade AD, Brasileiro-Santos, MS.

 

References

 

  1. Patel SR. Obstructive sleep apnea. Ann Intern Med 2019;171(11):ITC81-ITC96. doi: 10.7326/AITC201912030 [Crossref]
  2. Sauleda J, Garcia-Palmer FJ, Tarraga S, Maimo A, Palou A, Augusti AGN. Skeletal Muscle changes in patients with obstructive sleep apnoea syndrome. Respir Med 2006;97(7):806-10. doi: 10.1016/S0954-6111(03)00034-9 [Crossref]
  3. Rundo JV. Obstructive sleep apnea basics. Cleve Clin J Med 2019;86(9Suppl1):2-9. doi: 10.3949/ccjm.86.s1.02 [Crossref]
  4. Marillier M, Gruet M, Baillieul S, Wuyam B, Tamisier R, Levy P et al.s. Impaired erebral oxygenation and exercise tolerance in patients with severe obstructive sleep apnea syndrome. Sleep Med 2018;51:37-46. doi: 10.1016/j.sleep.2018.06.013 [Crossref]
  5. Berger M, Kline CE, Cepeda FX, Rizzi CF, Chapelle C, Laporte S, et al. Does obstructive sleep apnea affect exercise capacity and the hemodynamic response to exercise? An individual patient data and aggregate meta-analysis. Sleep Med Rev 2019;45:42-53. doi: 10.1016/j.smrv.2019.03.002 [Crossref]
  6. Vitacca M, Paneroni M, Braghiroli A, Balbi B, Aliani M, Guido P, et al. Exercise capacity and comorbidities in patients with obstructive sleep apnea. J Clin Sleep Med 2020;16(4):531-38. doi: 10.5664/jcsm.8258 [Crossref]
  7. Chien MY, Wu YT, Lee PL, Chang YJ, Yang PC. Inspiratory muscle disfunction in patients with severe obstructive sleep apnoea. Eur Respir J 2010;35(2):373-80. doi: 10.1183/09031936.00190208 [Crossref]
  8. Van Offenwert E, Vrijsen B, Belge C, Troosters T, Buyse B, Testelmans D. Physical activity and exercise in obstructive sleep apnea. Acta Clin Belg 2019;74(2):92-101. doi: /10.1080/17843286.2018.1467587 [Crossref]
  9. Sant´Ana LO, Scartoni FR, Portilho LF, Scudese E, Oliveira CQ, Senna GW. Comparação das variáveis cardiovasculares em idosos ativos em diferentes modalidades físicas. Rev Bras Fisiol Exerc 2019;18(4):186-94. doi: 10.33233/rbfe.v18i4.3232 [Crossref]
  10. American Thoracic Society, American college of chest physicians ATS/ACCP Statement on cardiopulmonary exercise testing. Am J Respir Crit Care Med 2003; 167(2): 211-77. doi: 10.1164/rccm.167.2.211 [Crossref]
  11. Andrade CHSD, Cianci R, Malaguti C, Dal Corso S. O uso de testes do degrau para a avaliação da capacidade de exercício em pacientes com doenças pulmonares crônicas. J Bras Pneumol 2012;38(1):116-24. doi: 10.1590/S1806-37132012000100016 [Crossref]
  12. Pessoa BV, Jamami M, Basso RP, Regueiro EMG, Di Lorenzo VAP, Costa D. Teste do degrau e teste da cadeira: comportamento das respostas metábolo-ventilatórias e cardiovasculares na DPOC. Fisioter Mov 2012;25(1):105-15. http://doi.org/10.1590/S0103-51502012000100011 [Crossref]
  13. Reis CM, Silva TC, Karloh M, Araujo CLP, Gulart AA, Mayer AF. Performance of healthy adult subjects in Glittre ADL-test. Fisioter Pesqui 2015;22(1):41-7. http://doi.org/10.590/1809-2950/13125722012015 [Crossref]
  14. Corrêa KS, Karloh M, Martins LQ, Dos Santos K, Mayer AF. O Teste de AVD-Glittre é capaz de diferenciar a capacidade funcional de indivíduos com DPOC da de saudáveis? Rev Bras Fisioter 2011;15(6):467-73. doi: 10.1590/S1413-35552011005000034 [Crossref]
  15. Karloh M, Karsten M, Pissaia FV, Araujo CLP, Mayer AF. Physiological responses to the Glittre-ADL test in patients with cronic obstructive pulmonar disease. J Rehabil Med 2014;46:88-94. doi: 10.2340/16501977-1217 [Crossref]
  16. Valadares YD, Correa KS, Silva BO, Araujo CCP, Karloh M, Mayer AF. Aplicabilidade de testes de atividade de vida diária em indivíduos com insuficiência cardíaca. Rev Bras Med Esporte 2011;17(5):310-14. doi: 10.1590/S1517-86922011000500003 [Crossref]
  17. Monteiro F, Ponce DA, Silva H, Carrilho AF, Pitta F. Validity and reliability of the Glittre ADL-Test in obese and post-bariatric surgery patients. Obes Surg 2017;27(1):110-14. doi: 10.1007/s11695-016-2244-7 [Crossref]
  18. Silva OB, Filho DC. A new proposal to guide velocity and inclination in the ramp protocol for treadmill ergometer. Arq Bras Cardiol 2003;81:48-53. doi: 10.1590/S0066-782X2003000900004 [Crossref]
  19. Skumlien S, Hagelund T, Bjortuft O, Ryg MA. Field test of functional status as performance of activities of daily living in CODP patients. Respir Med 2006;100:316-23. doi: 10.1016/j.rmed.2005.04.022 [Crossref]
  20. Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol 2001;37(1):153-6. doi: 10.1016/S0735-1097(00)01054-8
  21. Silva D, Corrêa J, Sá M, Normando V, Silva SM., Dal Corso S, et al. Validation and reproducibility of the Glittre activities of daily living test for individuals with Parkinson's disease. Rev Neurol 2019;69(10):395-401. doi: 10.33588/rn.6910.2019217 [Crossref]
  22. Arena R, Myers J, Williams MA, Gulati M, Kligfield P, Balady GJ, et al. Assessment of functional capacity in clinical and research settings: A scientific statement from the American Heart Association Committee on Exercise, Rehabilitation and Prevention of the council on clinical cardiology and the council on cardiovascular nursing. Circulation 2007;116:329-63. doi: 10.1161/CIRCULATIONAHA.106.184461 [Crossref]
  23. Hargens TA, Guill SG, Zedalis D, Gregg JM, Nickols-Richardson SM, Herbert WG. Attenuated heart rate recovery following exercise testing in overweight young men with untreated obstructive sleep apnea. Sleep 2008;31(1):104-10. doi: 10.1093/sleep/31.1.104 [Crossref]
  24. Pływaczewski R, Stokłosa A, Bieleń P, Bednarek M, Czerniawska J, Jonczak, et al. Six-minute walk test in obstructive sleep apnoea. Pneumonol Alergol Pol 2008;76:75-82.
  25. Rami K, William A, Patt B, Roy M, Keding H, Jarjoura D. Cardiac effects of continuous and bilevel positive airway pressure for patients with heart failure and obstructive sleep apnea. Chest 2009;134(6):1162-8. doi: 10.1378/chest.08-0346 [Crossref]
  26. Abdelghani A, Ben Saad H, Ben Hassen I, Ghannouchi I, Ghrairi H, Bougmiza I e cols. Evaluation of the deficiency and the submaximal exercise capacity in obstructive sleep apnea patients. Rev Mal Respir 2010;27:266-74. doi: 10.1016/j.rmr.2010.02.004 [Crossref]
  27. Billings CG, Aung T, Renshaw SA., Bianchi SM. Incremental shuttle walk test in the assessment of patients with obstructive sleep apnea-hypopnea syndrome. J Sleep Res 2013;22:471-7. doi: 10.1111/jsr.12037 [Crossref]
  28. Masa JF, Corral J, Caballero C, Barrot E, Terán-Santos J, Alonso-Álvarez ML, et al. Non-invasive ventilation in obesity hypoventilation syndrome without severe obstructive sleep apnoea. Thorax 2016;71(10):899-906. doi: 10.1136/thoraxjnl-2016-208501 [Crossref]
  29. Goel AK, Talwar D, Jain SK. Evaluation of short-term use of nocturnal nasal continuous positive airway pressure for a clinical profile and exercise capacity in adult patients with obstructive sleep apnea-hypopnea syndrome. Lung India 2015;32:225-32. doi: 10.4103%2F0970-2113.156226 [Crossref]
  30. Santos K, Gulart AA, Munari AB, Cani KC, Mayer AF. Reliability of ventilatory parameters, dynamic hyperinflation, and performance in the Glittre-ADL test in COPD patients. COPD J Chronic Obstr Pulm Dis 2016;13(6):700-5. doi: 10.1080/15412555.2016.1177007 [Crossref]