Walking with controlled breathing improves exercise tolerance,anxiety,and quality of life in heart failure patients: A randomized controlled trial

Research design and participants

This randomized, controlled trial consisted of four repeated measurement time points (baseline, Week 2, Week 4, and Week 12). A convenience sample of patients with heart failure was consecutively recruited from the cardiology ward of the 1000-bed Cheng Hsin General Hospital in Taiwan. Participants in the WwB group were given a structured intervention about walking and breathing for 12 weeks; those in the control group received usual care for heart failure during the same study period. A randomization procedure was performed offsite by two registered nurses who hold master’s degrees and were not involved in this study. Permuted-block randomization, with every block comprising four participants, was used to achieve balanced numbers in the two groups. The randomization was based on computer-generated random sequences that were separately placed in opaque, sealed envelopes to ensure random allocation and concealment of the participants’ identities. Patients were asked to draw an envelope that determined assignment into either the WwB or the control group.

Participants included in this study were aged ⩾20 years, were diagnosed as having heart failure (International Classification of Diseases, Ninth Revision, Clinical Modification code 428.0) and classified in the New York Heart Association (NYHA) class I–III range by cardiologists in the study hospital, were able to communicate, and could ambulate. Exclusion criteria were long-term use of oxygen or breathing apparatus, regular dialysis, limb movement disorders, and serious conditions such as aortic balloon pump placement and severe arrhythmia, which were all confirmed by the cardiologists. Effect size determined from one previous study; ²⁰ however, this study conservatively use a lower value of effect size because of the severity of heart failure and the intervention period. On the basis of the primary outcome of a 6-minute walk distance (6MWD) with a 0.3 effect size and an 80% power at 5% significance determined using four repeated measurement times and G-power software, a minimum of 90 participants (45 in each group) were required. Figure 1 presents the flowchart for the research design and participant allocation.

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Figure 1.

Flow chart of research design and participants.

Intervention

The WwB intervention consisted of a warm-up, main course, and cool-down, performed twice daily in the morning and afternoon, for 12 consecutive weeks. To begin the intervention, a warm-up was performed for five minutes before walking and included stretching the head and neck, turning the shoulders forward and backward, shaking the hands, and lifting each foot. Abdominal deep breathing patterns were designed and taught; inhalation and exhalation times were targeted at a 1:2 ratio, and breathing rates were allowed to decrease to <10 times per min before walking would begin. Then, the WwB main course was performed for 15 min. In the hospital, participants walked in the corridors of the cardiology ward, accompanied by a researcher while continuing the abdominal breathing patterns. To maintain walking intensity, the rating of perceived exertion was used as a controlling principle. The goal was to hold the rating of perceived exertion between 12 and 13, indicating that a patient is using little effort to breathe but is becoming slightly tired. ²¹ Finally, a cool-down movement was performed for five minutes. Participants slowed their walking speed, stopped walking, and returned to their normal breathing rate.

All participants received the usual hospital care, including routine medications and guidance about diet, daily activity, weight control, and water restrictions. In addition to the usual care, the intervention group practiced WwB. Participants in the WwB group began interventions when they finished the acute phase and were becoming stable without the use of intravenous infusion of inotropic agents. For safety and as the standard required by the study hospital, heart rate, blood pressure, and oxygen saturation were assessed in patients before and after the WwB intervention to ensure stable conditions. During WwB, signs and symptoms of discomfort and falls or other accidents were documented by the researchers. After patients were discharged, they continued engaging in WwB in places that were near and suitable for walking. An exercise diary was designed for the participants to use at home, which could record their daily practices. Weekly phone calls were also made to confirm WwB intervention performance. 6MWD and physiological factor data were collected at the baseline, Week 2, Week 4, and Week 12 during the WwB intervention. In addition, the Multidimensional Assessment of Interoceptive Awareness (MAIA) scale, Hospital Anxiety and Depression Scale (HADS), and EuroQol 5-Dimensions (EQ-5D) scale questionnaires were used to collect data at the baseline and Week 12.

Ethical consideration

Ethical approvals were obtained from the institutional review board of the study hospital (CHGH-IRB No. (411) 102-58-2). Written informed consent was obtained from all participants after they received a full explanation of the study. Participants were free to withdraw at any time during the study without affecting their care. Data remained confidential at all times.

Instruments

The demographic and clinical characteristics monitored included age, sex, education, marital status, smoking, diabetes diagnosis, time to diagnosis of heart failure, heart failure functional class, left ventricular volume injection, and cardiovascular medications. The primary outcome was exercise tolerance measured by the 6MWD test. Participants walked the 160 m long cardiology ward corridor, and the longest distances walked were measured at six minutes. If participants had cold sweats, pallor, difficulty breathing, chest tightness, dizziness, or other symptoms during the test, the test was immediately stopped. The 6MWD test is a simple and safe method assessing movement. An increase or decrease of ⩾50 m represents a significant change. ²² The reliability and validity of the 6MWD test have been tested, and good agreement was found in patients undergoing cardiac rehabilitation. ²³

Physiological factors included heart rate, blood pressure, and oxyhemoglobin saturation. Heart rate was measured using a stethoscope (Littmann Class II; 3M, St Paul, Minnesota, USA), specifically recording precordial auscultation in the apical pulse. The normal range of heart rate was 60–100 beats per min. Blood pressure was measured by a mercury sphygmomanometer (Model N-300, Rudolf Riester GmbH, Germany) that was certified by the Bureau of Standards, Inspection, and Metrology Correction. The normal ranges of systolic and diastolic blood pressures were 120–139 over 80–89 mm Hg, respectively. Oxyhemoglobin saturation (SpO₂) was examined by a pulse oximeter (Model 9560, Nonin, USA) on the left index finger. The normal percentage of the hemoglobin that carries oxygen is between 90–100%.

Interoceptive awareness was measured by the MAIA scale. ¹² The 32-item MAIA scale is categorized into eight scales: Noticing, Not Distracting, Not Worrying, Attention Regulation, Emotional Awareness, Self-Regulation, Body Listening, and Trusting. Each item is scored on a six-point scale ranging from zero (“never”) to five (“always true”), with higher scores indicating greater self-awareness. The MAIA has nee reported to have good reliability and validity.^12,24 Cronbach’s alpha measures of internal consistency at pre- and post-test were determined to be 0.89 and 0.90, respectively.

Negative moods were measured by the HADS, ²⁵ which assesses the mood disorder severity through 14 questions, seven for anxiety and seven for depression. Anxiety and depression scores are recorded separately, and each score ranges between 0–21 points (with higher scores indicating higher degrees of depression or anxiety). Scores of <7 points do not indicate anxiety or depression; 8–10 points indicate borderline cases; and ⩾11 points indicate a tendency toward anxiety or depression. Cronbach’s alpha was determined to be 0.77 for anxiety and 0.63 for depression in this study.

Health-related QoL was measured by the EQ-5D scale including two parts. ²⁶ The EQ-5D Index has the five dimensions, namely mobility, self-care, usual activities, pain/discomfort, and anxiety/frustration; scoring ranges from one point (the best situation) to three points (the worst situation). The EQ-5D is a visual analog scale (VAS) that uses a total length of 20 cm in a vertical ruler from point 0 (the worst health status) to 100 (the best health status). EQ-5D has been extensively used to assess patients with cardiovascular disorders. ²⁷ Cronbach’s alpha of the EQ-5D was 0.75 in this study.

Statistical analysis

Data were analyzed using SPSS 20.0 for Windows (IBM, Chicago, Illinois, USA). Categorical variables are reported as the number of samples and percentages, and continuous variables are reported as means and standard deviations (SDs). The 6MWD data violated the assumption of normal distributions; therefore, the differences in the effects between the groups at repeated measurements were analyzed using the generalized estimating equation (GEE) method. A robust estimate of variance in the GEE models and an exchangeable working correlation structure were used to determine the between-group differences; time was treated as a categorical variable that was represented by three dummy-coded variables. Control variables were time-dependent physiological factors and time-independent interoceptive awareness that was the score that changed between the baseline and Week 12. The t-test was used to analyze the effects of anxiety, depression, QoL, and interoceptive awareness between the two groups. This study considered a value of p<0.05 to be statistically significant.

Limitations

This study has a few limitations. First, the convenience sample of patients with heart failure was recruited from one hospital, which may limit the generalizability of the study findings. Second, due to the nature of the WwB intervention, a blinded study was not possible. Third, a detection bias could have been introduced because the same researcher who performed the intervention also collected the study data. Fourth, young, male participants with heart failure were included in this study, who may find it easier to practice the WwB intervention. Therefore, the generalizability of the study findings to female individuals is limited. Finally, patient medication data were not collected at the baseline; therefore, the actual risk of confounding results due to the differences in medications taken among the groups during the intervention period remains unclear.