Introduction
One of the systems affected by aging is the cardiopulmonary system. Aging reduces cardiovascular health, and many cardiac diseases eventually lead to chronic heart failure (CHF). CHF is a condition characterized by impaired cardiac structure and function, wherein the heart cannot pump sufficient blood to meet the body’s needs, resulting in reduced oxygen and nutrient delivery. CHF is one of the most critical conditions in older adults, with its prevalence and incidence increasing with age. Respiratory exercises, including those as adjunctive treatments, have received less attention in this population. Among the latest models of respiratory training for these patients is device-guided slow breathing exercise. Accordingly, this study investigates the effect of routine respiratory exercises and device-guided gradual slow breathing exercises on the quality of life, physical performance, and blood pressure in elderly patients with CHF.

Methods 
This single-blind randomized clinical trial was conducted in 2021–2022 in Mashhad City, Iran. A total of 36 patients with CHF were randomly assigned to the following three groups of 12 using a sealed-envelope method: a control group (mean age: 64.58±3.46 years), a routine breathing exercise group (mean age: 63.67±3.91 years), and a device-guided gradual slow breathing exercise group (mean age: 62.58±2.57 years). The inclusion criteria were having class II and III heart failure based on New York Heart Association (NYHA) classification, aged 60–70 years, heart failure diagnosis for 3–5 years, ejection fraction < 50%, receiving standard medication for at least one month prior to the study, no history of unstable angina or complex ventricular arrhythmias, no myocardial infarction in the past year, no cardiac pacemaker, no bypass surgery or angioplasty in the past six months, no participation in other exercise programs in the past six months, and no history of pulmonary disease, smoking, angina, heart surgery (within the past six months), orthopedic or neurological conditions, or treatment with steroids or chemotherapy. Exclusion criteria included unwillingness to continue, participation in other exercise programs, or disruption of treatment during the study.
The intervention lasted four weeks, with pre- and post-intervention assessments completed. Due to the COVID-19 pandemic, all interventions were conducted at participants’ homes following strict protocols, under the direct supervision of the researcher. Quality of life was measured using the Minnesota living with heart failure questionnaire, physical performance was assessed via the 6-min walk test, and blood pressure was measured using a blood pressure Holter monitor. The data were analyzed using the SPSS software, version 23, employing paired t-tests and one-way analysis of variance.

Results 
No statistically significant differences were observed in demographic variables between the groups pre-intervention (P>0.05). Similarly, no significant changes in hemodynamic variables were noted post-intervention (P>0.05). None of the participants experienced any adverse events during the study. Comparisons of hemodynamic status within each group showed a significant improvement in peripheral oxygen saturation (SPO2) before the 6-min walk test in the gradual slow breathing exercise group (P=0.047). However, no statistically significant differences in SPO2 were observed between the three groups post-intervention (P>0.05).
Mean quality-of-life scores significantly decreased in the routine breathing group (P=0.02) and the gradual slow breathing group (P=0.007). Physical performance scores significantly increased in the routine breathing group (P=0.028) and the gradual slow breathing group (P=0.033). The one-way analysis of variance test showed a statistically significant decrease in quality-of-life scores in the routine breathing group (P=0.026) and a significant increase in physical performance scores in the gradual slow breathing group (P=0.042) compared to the control group.
In NYHA class II patients, both routine breathing exercises (P=0.02) and gradual slow breathing exercises (P=0.007) significantly improved quality-of-life scores. Physical performance scores increased significantly in the gradual slow breathing group (P=0.02) within class II patients. No significant changes were observed in class III patients or other parameters within class II (P>0.05). The one-way analysis of variance on changes in mean scores across the three groups based on NYHA classification showed statistically significant differences only in quality-of-life (P=0.01) and physical performance (P=0.02). Post hoc Bonferroni analysis revealed a significant reduction in quality-of-life scores in the routine breathing group (P=0.015) and a significant increase in physical performance scores in the gradual slow breathing group (P=0.018) compared to the control group in NYHA class II.

Conclusion
No significant changes in blood pressure were observed post-intervention, aligning with Drozdz et al’s [52] findings in 2016 but contrasting with Lachowska et al.’s 2019 study [23]. The discrepancy may be attributed to the differing durations of interventions in the latter study. Respiratory exercises improved quality of life, consistent with findings by Lachowska et al. (2019) [23] and Azambuja et al. (2020) [60] but contrasting with Drozdz et al. (2016) [52]. These differences might stem from the very low fixed breathing rate of 6 breaths/min or differences in participants’ age range.
The exercises also enhanced physical performance and increased the six-minute walking distance, consistent with Lachowska et al. (2019) [23], Kawecka-Jaszcz et al. (2017) [65], and Azambuja et al. (2020) [60]. This improvement highlights the positive impact of these exercises on the functional capacity of patients who often face daily challenges.

Ethical Considerations
Compliance with ethical guidelines
Ethical approval was obtained from the Medical Ethics Committee of Tarbiat Modares University, Tehran, Iran (Code: IR.MODARES.REC.1400.200), and the study was registered in the Iranian Registry of Clinical Trials (IRCT) (Code: IRCT20210426051093N1). After the study, the control group received a 10-session routine respiratory training program over four weeks alongside relevant medical recommendations.

Funding
This project was financially supported by Tarbiat Modares University, Tehran, Iran (Grand No.: 88223).

Authors' contributions
Conceptualization, methodology, review and editing: Roya Ravanbod and Mehdi Rahmati Yami; Supervision and investigation: All authors; Writing the initial draft: Mehdi Rahmati Yami.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The researchers express gratitude to Tarbiat Modares University for financial support, as well as all participants and the following individuals: Physiotherapists Elham Azarmi and Afrooz Etedali, Mehdi Alizadeh Birjandi, Mohammad Sookhtanlou, Saeed Akhlaghi, Farhad Azadi, Majid Shahbazi, Nima Davari, and Hemmat Jamshidi.


References

1. Olshansky SJ, Carnes BA, Cassel CK. The aging of the human species. Scientific American. 1993; 268(4):46-52. [DOI:10.1038/scientificamerican0493-46]
2. Mosallanezhad Z, Salavati M, Hellström K, Sotoudeh GR, Nilsson Wikmar L, Frändin K. Cross-cultural adaptation, reliability and validity of the Persian version of the modified falls efficacy scale. Disability and Rehabilitation. 2011; 33(25-26):2446-53. [DOI:10.3109/09638288.2011.574774]
3. Azarmi E, Azadi F, Mosallanezhad Z, Vahedi M. [Relationship of low back pain and knee pain with dynamic balance of the elderly living in nursing homes in Mashhad, Iran (Persian)]. Salmand. 2023; 18(3):460-73. [DOI:10.32598/sija.2023.774.5]
4. Saboor M. [Elderly’s medical therapy status (Persian)]. Salmand. 2007; 2(1):216-22. [Link]
5. Hosseini S, Keshavarz A, Amin A, Maleki M, Bakhshandeh Abkenar H. [Nutritional status and non-diet associated factors of hospitalized heart-failure elderly patients (Persian)]. Salmand. 2010; 5(2):61-6. [Link]
6. Zeighami Mohammadi S, Asgharzadeh Haghighi S, Falah N. [The prevalence of anemia in elderly with systolic heart failure (Persian)]. Salmand. 2010; 5(2):25-33. [Link]
7. Janjani P, Salehabadi Y, Motevaseli S, Heidari Moghaddam R, Siabani S, Salehi N. [Prevalence of risk factors, reperfusion therapy and mortality due to myocardial infarction (Persian)]. Salmand. 2023; 18(1):78-91. [DOI:10.32598/sija.2022.3091.1]
8. Ahmadi A, Soori H, Mobasheri M, Etemad K, Khaledifar A. [Heart failure, the outcomes, predictive and related factors in Iran (Persian)]. Journal of Mazandaran University of Medical Sciences. 2014;24(118):180-8. [Link]
9. Seyam SH. Study of situation of elderly residents in Guilan elderly nursing home. Journal of Guilan University of Medical Sciences. 2001; 10(39):119-26. [Link]
10. Mohaqeqi Kamal SH, Basakha M. [Prevalence of chronic diseases among the older adults in Iran: Does socioeconomic status matter? (Persian)]. Salmand. 2022; 16(4):468-81. [DOI:10.32598/sija.2022.16.4.767.2]
11. Inamdar AA, Inamdar AC. Heart failure: Diagnosis, management and utilization. Journal of Clinical Medicine. 2016; 5(7):62. [DOI:10.3390/jcm5070062]
12. Ponikowski P, Anker SD, AlHabib KF, Cowie MR, Force TL, Hu S, et al. Heart failure: Preventing disease and death worldwide. ESC Heart Failure. 2014; 1(1):4-25. [DOI:10.1002/ehf2.12005]
13. Groenewegen A, Rutten FH, Mosterd A, Hoes AW. Epidemiology of heart failure. European Journal of Heart Failure. 2020; 22(8):1342-56. [DOI:10.1002/ejhf.1858]
14. Mozaffarian D, Benjamin EJ, Go AS, Arnett DK, Blaha MJ, Cushman M, et al. Heart disease and stroke statistics-2016 update. Circulation. 2016; 133(4):e39-360. [DOI:10.1161/CIR.0000000000000350]
15. Lloyd-Jones DM, Larson MG, Leip EP, Beiser A, D’Agostino RB, Kannel WB, et al. Lifetime risk for developing congestive heart failure. Circulation. 2002; 106(24):3068-72. [DOI:10.1161/01.CIR.0000039105.49749.6F]
16. Dolgin M, New York Heart Association Criteria Committee. Nomenclature and criteria for diagnosis of diseases of the heart and great vessel. Boston: Little, Brown & Co; 1994. [Link]
17. Abbasi A, Asaiesh H, Hosseini SA, Qorbani M, Abdollahi AA, Rouhi G, et al. [The relationship between functional performance in patients with heart failure and quality of life (QOL) (Persian)]. Iranian South Medical Journal. 2010; 13(1):31-40. [Link]
18. Abbasi K, Mohammadi E, Sadeghian H, Gholami Fesharaki M. [Quality of life in patients with heart failure (Persian)]. Iranian Journal of Nursing Research. 2016; 11(2):10-23. [Link]
19. Oerkild B, Frederiksen M, Hansen JF, Simonsen L, Skovgaard LT, Prescott E. Home-based cardiac rehabilitation is as effective as centre-based cardiac rehabilitation among elderly with coronary heart disease: Results from a randomised clinical trial. Age and Ageing. 2010; 40(1):78-85. [DOI:10.1093/ageing/afq122]
20. Achttien R, Staal J, Merry A. KNGF guideline cardiac rehabilitation KNGF clinical practice guideline for physical therapy in patients undergoing cardiac rehabilitation practice guidelines. The Dutch Journal of Physics. 2011; 121(4):1-47. [Link]
21. Price KJ, Gordon BA, Bird SR, Benson AC. A review of guidelines for cardiac rehabilitation exercise programmes: Is there an international consensus? European Journal of preventive cardiology. 2016; 23(16):1715-33. [DOI:10.1177/2047487316657669]
22. van Hateren KJ, Landman GW, Logtenberg SJ, Bilo HJ, Kleefstra N. Device-guided breathing exercises for the treatment of hypertension: An overview. World Journal of Cardiology. 2014; 6(5):277. [DOI:10.4330/wjc.v6.i5.277]
23. Lachowska K, Bellwon J, Narkiewicz K, Gruchała M, Hering D. Long-term effects of device-guided slow breathing in stable heart failure patients with reduced ejection fraction. Clinical Research in Cardiology. 2019; 108(1):48-60. [DOI:10.1007/s00392-018-1310-7]
24. Brook RD, Appel LJ, Rubenfire M, Ogedegbe G, Bisognano JD, Elliott WJ, et al. Beyond medications and diet: Alternative approaches to lowering blood pressure. Hypertension. 2013; 61(6):1360-83. [DOI:10.1161/HYP.0b013e318293645f]
25. Amini M, Gholami M, Aabed Natanzi H, Shakeri N, Haddad H. [Effect of diaphragmatic respiratory training on some pulmonary indexes in older people with chronic obstructive pulmonary disease (Persian)]. Salmand. 2019; 14(3):332-41. [DOI:10.32598/sija.13.10.330]
26. Farahbod M, Masoudi Asl I, Tabibi SJ, Kamali M. [The status of rehabilitation in Iran: Barriers and facilitators (Persian)]. Salmand. 2023; 18(2):218-33. [DOI:10.32598/sija.2023.2535.1]
27. Ramalho SHR, Cipriano Junior G, Vieira PJC, Nakano EY, Winkelmann ER, Callegaro CC, et al. Inspiratory muscle strength and six-minute walking distance in heart failure: Prognostic utility in a 10 years follow up cohort study. Plos One. 2019; 14(8):e0220638. [DOI:10.1371/journal.pone.0220638]
28. Montemezzo D, Fregonezi GA, Pereira DA, Britto RR, Reid WD. Influence of inspiratory muscle weakness on inspiratory muscle training responses in chronic heart failure patients: A systematic review and meta-analysis. Archives of Physical Medicine and Rehabilitation. 2014; 95(7):1398-407. [DOI:10.1016/j.apmr.2014.02.022]

29. Kulur AB, Haleagrahara N, Adhikary P, Jeganathan PS. [Efeito da respiração diafragmática sobre a variabilidade da frequência cardíaca na doença cardíaca isquêmica com diabete (Portuguese)]. Arquivos Brasileiros de Cardiologia. 2009; 92(6):457-63. [DOI:10.1590/S0066-782X2009000600008]
30. Achttien RJ, Staal JB, van der Voort S, Kemps HM, Koers H, Jongert MWA, et al. Exercise-based cardiac rehabilitation in patients with chronic heart failure: A Dutch practice guideline. Netherlands Heart Journal. 2014; 23(1):6-17. [DOI:10.1007/s12471-014-0612-2]
31. Cahalin LP, Arena RA. Breathing exercises and inspiratory muscle training in heart failure. Heart Failure Clinics. 2015; 11(1):149-72. [DOI:10.1016/j.hfc.2014.09.002]
32. Gosselink R, Bott J, Johnson M, Dean E, Nava S, Norrenberg M, et al. Physiotherapy for adult patients with critical illness: Recommendations of the European Respiratory Society and European Society of intensive care medicine task force on physiotherapy for critically Ill patients. Intensive Care Medicine. 2008; 34(7):1188-99. [DOI:10.1007/s00134-008-1026-7]
33. Pathmanathan N, Beaumont N, Gratrix A. Respiratory physiotherapy in the critical care unit. Continuing Education in Anaesthesia Critical Care & Pain. 2014; 15(1):20-5. [DOI:10.1093/bjaceaccp/mku005]
34. Jang MH, Shin MJ, Shin YB. Pulmonary and physical rehabilitation in critically Ill patients. Acute and Critical Care. 2019; 34(1):1-13. [DOI:10.4266/acc.2019.00444]
35. Faul F, Erdfelder E, Buchner A, Lang AG. Statistical power analyses using G*Power 3.1: Tests for correlation and regression analyses. Behavior Research Methods. 2009; 41(4):1149-60. [DOI:10.3758/BRM.41.4.1149]
36. Sadeghi Sherme M, Alavi Zerang F, Ahmadi F, Karimi Zarchi A, Babatabar HD, Ebadi A, et al. [Effect of applying continuous care model on quality of life in heart failure patients (Persian)]. International Journal of Behavioral Sciences. 2009; 3(1):9-13. [Link]
37. Palmer K, Bowles KA, Paton M, Jepson M, Lane R. Chronic heart failure and exercise rehabilitation: A systematic review and meta-analysis. Archives of Physical Medicine and Rehabilitation. 2018; 99(12):2570-82. [DOI:10.1016/j.apmr.2018.03.015]
38. Winkelmann ER, Chiappa GR, Lima CO, Viecili PR, Stein R, Ribeiro JP. Addition of inspiratory muscle training to aerobic training improves cardiorespiratory responses to exercise in patients with heart failure and inspiratory muscle weakness. American Heart Journal. 2009; 158(5):768.e1-7. [DOI:10.1016/j.ahj.2009.09.005]
39. Eskandari S, Heravi-Karimooi M, Rejeh N, Ebadi A, Montazeri A. [Translation and validation study of the Iranian version of Minnesota living with heart failure questionnaire (Persian)]. Payesh. 2015; 14(4):475-84. [Link]
40. Passantino A, Lagioia R, Mastropasqua F, Scrutinio D. Short-term change in distance walked in 6 min is an indicator of outcome in patients with chronic heart failure in clinical practice. Journal of the American College of Cardiology. 2006; 48(1):99-105. [DOI:10.1016/j.jacc.2006.02.061]
41. Yancy CW, Jessup M, Bozkurt B, Butler J, Casey DE, Drazner MH, et al. 2013 ACCF/AHA guideline for the management of heart failure: A report of the American College of Cardiology Foundation/American heart association task force on practice guidelines. Journal of the American College of Cardiology. 2013; 62(16):e147-239. [DOI:10.1016/j.jacc.2013.05.019]

42. Daneshmandi H, Choobineh AR, Rajaee-Fard AR. [Validation of borg’s RPE 6-20 scale in male industrial workers of Shiraz city based on heart rate (Persian)]. Jundishapur Scientific Medical Journal. 2012; 11(1):1-10. [Link]
43. Main E, Denehy L. Cardiorespiratory physiotherapy: Adults and paediatrics. Amsterdam: Elsevier; 2016. [Link]
44. Clark AL. Exercise and heart failure: Assessment and treatment. Heart. 2006; 92(5):699-703. [DOI:10.1136/hrt.2005.073643]
45. Severin R, Phillips SA. Respiratory muscles and chemoreflex sensitivity in heart failure: A breath of fresh air. Canadian Journal of Cardiology. 2017; 33(4):433-6. [DOI:10.1016/j.cjca.2017.02.003]
46. Cahalin LP, Arena R, Guazzi M, Myers J, Cipriano G, Chiappa G, et al. Inspiratory muscle training in heart disease and heart failure: A review of the literature with a focus on method of training and outcomes. Expert Review of Cardiovascular Therapy. 2013; 11(2):161-77. [DOI:10.1586/erc.12.191]
47. Ribeiro JP, Chiappa GR, Neder JA, Frankenstein L. Respiratory muscle function and exercise intolerance in heart failure. Current Heart Failure Reports. 2009; 6(2):95-101. [DOI:10.1007/s11897-009-0015-7]
48. Grossman E, Grossman A, Schein MH, Zimlichman R, Gavish B. Breathing-control lowers blood pressure. Journal of Human Hypertension. 2001; 15(4):263-9. [DOI:10.1038/sj.jhh.1001147]
49. Russo MA, Santarelli DM, O’Rourke D. The physiological effects of slow breathing in the healthy human. Breathe. 2017; 13(4):298-309. [DOI:10.1183/20734735.009817]
50. Zhang Z, Wang B, Wu H, Chai X, Wang W, Peng CK. Effects of slow and regular breathing exercise on cardiopulmonary coupling and blood pressure. Medical & Biological Engineering & Computing. 2017; 55(2):327-41. [DOI:10.1007/s11517-016-1517-6]
51. Ekman I, Kjellström B, Falk K, Norman J, Swedberg K. Impact of device-guided slow breathing on symptoms of chronic heart failure: A randomized, controlled feasibility study. European Journal of Heart Failure. 2011; 13(9):1000-5. [DOI:10.1093/eurjhf/hfr090]
52. Drozdz T, Bilo G, Debicka-Dabrowska D, Klocek M, Malfatto G, Kielbasa G, et al. Blood pressure changes in patients with chronic heart failure undergoing slow breathing training. Blood Pressure. 2016; 25(1):4-10. [DOI:10.3109/08037051.2016.1099800]
53. Bernardi L, Porta C, Spicuzza L, Bellwon J, Spadacini G, Frey AW, et al. Slow breathing increases arterial baroreflex sensitivity in patients with chronic heart failure. Circulation. 2002; 105(2):143-5. [DOI:10.1161/hc0202.103311]
54. Parati G, Malfatto G, Boarin S, Branzi G, Caldara G, Giglio A, et al. Device-guided paced breathing in the home setting: Effects on exercise capacity, pulmonary and ventricular function in patients with chronic heart failure: A pilot study. Circulation Heart Failure. 2008; 1(3):178-83. [DOI:10.1161/CIRCHEARTFAILURE.108.772640]
55. Zaros PR, Pires CE, Bacci M, Moraes C, Zanesco A. Effect of 6-months of physical exercise on the nitrate/nitrite levels in hypertensive postmenopausal women. BMC Women’s Health. 2009; 9(17):1-5. [DOI:10.1186/1472-6874-9-17]

56. Chan JS, Mann LM, Doherty CJ, Angus SA, Thompson BP, Devries MC, et al. The effect of inspiratory muscle training and detraining on the respiratory metaboreflex. Experimental Physiology. 2023; 108(4):636-49. [DOI:10.1113/EP090779]
57. Mahtani KR, Nunan D, Heneghan CJ. Device-guided breathing exercises in the control of human blood pressure: Systematic review and meta-analysis. Journal of Hypertension. 2012; 30(5):852-60. [DOI:10.1097/HJH.0b013e3283520077]
58. Adamopoulos S, Schmid JP, Dendale P, Poerschke D, Hansen D, Dritsas A, et al. Combined aerobic/inspiratory muscle training vs. aerobic training in patients with chronic heart failure: The Vent-HeFT trial: A European prospective multicentre randomized trial. European Journal of Heart Failure. 2014; 16(5):574-82. [DOI:10.1002/ejhf.70]
59. Wang MH, Yeh ML. Respiratory training interventions improve health status of heart failure patients: A systematic review and network meta-analysis of randomized controlled trials. World Journal of Clinical Cases. 2019; 7(18):2760. [DOI:10.12998/wjcc.v7.i18.2760]
60. Azambuja ACM, de Oliveira LZ, Sbruzzi G. Inspiratory muscle training in patients with heart failure: What is new? Systematic review and meta-analysis. Physical Therapy. 2020; 100(12):2099-109. [DOI:10.1093/ptj/pzaa171]
61. Ledwoch J, Franke J, Lubos E, Boekstegers P, Puls M, Ouarrak T, et al. Prognostic value of preprocedural 6-min walk test in patients undergoing transcatheter mitral valve repair-insights from the German transcatheter mitral valve interventions registry. Clinical Research in Cardiology. 2018; 107(3):241-8. [DOI:10.1007/s00392-017-1177-z]
62. Smart NA, Giallauria F, Dieberg G. Efficacy of inspiratory muscle training in chronic heart failure patients: A systematic review and meta-analysis. International Journal of Cardiology. 2013; 167(4):1502-7. [DOI:10.1016/j.ijcard.2012.04.029]
63. Kawecka-Jaszcz K, Bilo G, Drożdż T, Dębicka-Dąbrowska D, Kiełbasa G, Malfatto G, et al. Effects of device-guided slow breathing training on exercise capacity, cardiac function, and respiratory patterns during sleep in male and female patients with chronic heart failure. Polskie Archiwum Medycyny Wewnętrznej. 2017; 127(1):8-15. [DOI:10.20452/pamw.3890]
64. Teng HC, Yeh ML, Wang MH. Walking with controlled breathing improves exercise tolerance, anxiety, and quality of life in heart failure patients: A randomized controlled trial. European Journal of Cardiovascular Nursing. 2018; 17(8):717-27. [DOI:10.1177/1474515118778453]
65. Bernardi L, Spadacini G, Bellwon J, Hajric R, Roskamm H, Frey AW. Effect of breathing rate on oxygen saturation and exercise performance in chronic heart failure. The Lancet. 1998; 351(9112):1308-11. [DOI:10.1016/S0140-6736(97)10341-5]
66. Bilo G, Revera M, Bussotti M, Bonacina D, Styczkiewicz K, Caldara G, et al. Effects of slow deep breathing at high altitude on oxygen saturation, pulmonary and systemic hemodynamics. Plos One. 2012; 7(11):e49074. [DOI:10.1371/journal.pone.0049074]
67. Moreno AM, Toledo-Arruda AC, Lima JS, Duarte CS, Villacorta H, Nóbrega ACL. Inspiratory muscle training improves intercostal and forearm muscle oxygenation in patients with chronic heart failure: Evidence of the origin of the respiratory metaboreflex. Journal of Cardiac Failure. 2017; 23(9):672-9. [DOI:10.1016/j.cardfail.2017.05.003]