From May 2019 to February 2020, a randomized headphones-controlled single-blind trial of patients undergoing elective heart valve replacements was conducted at Fujian Medical University Union Hospital in Fuzhou (China). This study was registered in the Chinese Clinical Trial Registry (Registration date:10/04/2019; Number: ChiCTR1900022408).
The experimental group
Music therapy was delivered by binaural headphones to the patients three times 2 h after extubation, the second day after transfer to the general ward, and 1 day before discharge in the morning) by two senior experienced researchers. The subjects underwent the same soft music treatment (15 min) while laying in a recumbent position and wearing binaural headphones after a 30-min rest.
The control group
The control group received binaural headphones for the same three repetitions without any music and also after a 30-min rest.
Participants in the research underwent elective cardiac valve replacement surgical procedures. Inclusion criteria included being: (1) age ≥ 18 years; (2) eager to participate; (3) conscious; and (4) able to answer questions on pain, sleeplessness, and anxiety. Exclusion criteria included conditions putting the patient at higher risk of adverse outcomes, such as: (1) body mass index (BMI) > 35 kg/m2); (2) pulmonary artery pressure > 50 mmHg; (3) right ventricular failure; (4) ejection fraction (EF) of ≤ 35%; and (5) intubation for longer than 24 h. Participants who exhibited vision and hearing deficits or underwent emergency surgeries were excluded.
The reasoning behind the exclusion criteria was supported by several earlier research that revealed individuals with low EFs had significantly worse postsurgical findings than subjects with elevated EFs . Furthermore, the risk of postoperative complications was raised by right ventricular failure , intubation > 24 h, BMI > 35 kg/m2,  and pulmonary artery pressure > 50 mmHg.  In order to reduce the impact of increased postoperative complications such as acute kidney injury, low cardiac output syndrome and increased intubation duration on assessment of pain, anxiety and vital signs,
The Human Ethical Committee of Fujian Medical University Union Hospital approved the study (Approval Number: 2019KY019, date: 2019-01-31).
Participants were informed of the research protocol, and that enrollment was completely optional. Additionally, there would be no consequences if they decided to stop participating in the study at any point during it. Before commencing the experiment, all subjects submitted their informed consent.
The relevant sample size was calculated using the G*Power 3 software  to determine whether music therapy may reduce pain intensity. To detect a mean difference in pain intensity scores of 1.5 points (SD = 2.0)  shortly after music treatment, a total sample size of 86 patients was needed, with a two-sided significance level of 0.05, a power of 0.90 in a repeated measure between-factors context, considering a 10% dropout rate. 86 individuals (43 in the intervention group and 43 in the control group) were finally examined for this research.
Individuals were randomly placed into the control or experimental groups using a computer-generated list of randomly generated numbers. The group assignments were hidden from the participants. They were only told which of the two groups they would be placed in and that both groups would receive a treatment that involved wearing binaural headphones.
The demographic characteristics regarding the study participants were recorded at the time of admission. The participants' baseline sleep quality was obtained by averaging preoperative three measurements of the RCSQ (Richards-Campbell Sleep Questionnaire) score. The vital signs (respiration rate [RR], heart rate [HR], diastolic blood pressure [DBP], and systolic blood pressure [SBP]) were also obtained via ECG monitor and arterial or cuff manometer by averaging three measured results at four corresponding time points respectively.
The preintervention pain level and the pain level after the treatment between the two groups were compared using a VAS (visual analogue scale)  for pain quantification. The scale runs from 0 to 10, with 0 representing no pain and 10 being the most severe suffering achievable. A clinically significant variation is defined as a 20% or greater change . Individuals can select an expression ranging from "no hurts" to "hurts the worst" to best reflect their discomfort level. Among the five frequently used pain scales for patients after cardiovascular surgery, a study found that VAS had the highest response rate, the most reliable, and the easiest to comprehend .
The STAI (state-trait anxiety inventory) was utilized to determine the secondary outcome: anxiety level, which was established by comparing the anxiety levels before and after the treatment. The STAI is a popular method of evaluating anxiety. It has 20 items for state anxiety, each graded on a 4-point scale ranging from "1 = almost never" to "4 = very usually." Higher scores indicate higher anxiety levels; mild anxiety runs from 20 to 39, moderate anxiety ranges from 40 to 59, and increased anxiety ranges from 60 to 80 . Internal consistency coefficients for the STAI have varied between 0.86 and 0.95, and test–retest composite reliability has varied between 0.65 and 0.75.  Additionally widely utilized in Chinese populations,  STAI has been used in numerous investigations. At each time point, vital signs (RR, HR, DBP, and SBP) were also recorded.
The feeling of pain intensity and degree of anxiety are both highly correlated with inadequate sleep . The RCSQ (Richards-Campbell Sleep Questionnaire) was also applied to assess baseline sleep quality . The RCSQ is a six-item visual analogue scale created to measure how severely sick patients perceive their sleep quality. The scale assesses noise, overall quality of sleep, time awake, number of waking, sleep start delay, and perceptions of sleep depth. The scale ranges from 0 to 100, with 100 representing a good night's sleep and 0 representing a bad night for the individual. This sample's validity study revealed a whole-scale Cronbach alpha of 0.90. RCSQ is also used expansively in Chinese populations .
Both the experimental and control groups received binaural headphones from the senior, experienced researchers. Three-morning sessions of binaural headphone delivery were administered to the experimental group (2 h after extubation, the second day following transfer to the general ward, and 1 day before discharge). 15 min of music therapy using a binaural headphones was performed with the participants lying in a recumbent position after a 30-min rest. Since it has been discovered that melodious music with calming rhythms can have a calming effect and cause individuals to feel good , the same low-key music with approximately 60–80 beats per minute was made available . In addition, before we designed the music genre, we considered that different music styles might have different effects on pain and anxiety of patients after cardiac surgery . Therefore, to avoid confusion of different music types, the same type of music was selected to be transferred to the MP3 players before the intervention, with binaural headphones connected, and volume was regulated by participants.
The patient and setting were properly set up for the intervention (a performance place where mobile phones were switched off, the door was closed, and distractions were removed). The researchers made an effort to avoid disturbing the participants . The control group was given the same setting and identical pre- and post-testing procedures as the experimental group, except for soft music intervention. The study identified the participants' vital signs before the session after measuring their awareness and emotional condition (noticeable symptoms of delirium, anger, depression, etc., are considered unsuitable for intervention). Pain, anxiety levels and vital signs were recorded four times: before, and ten minutes after three corresponding musical therapy sessions. After all data had been collected, a survey was conducted to collect participants' opinions about the music intervention. Before the intervention, the RCSQ was utilized to obtain a baseline measure of the participants' sleep quality.
The Shapiro–Wilk test was employed for data distribution assessment. Continuous data were provided as means ± standard deviations. The student t-tests were carried out for inter-group studies for normally distributed data. Data with non-normal distribution are provided as medians and percentiles (interquartile range between the 25th and 75th percentiles) and analyzed via the non-parametric Mann–Whitney U test. Repeated measures of analysis of variance (RENOVA) with posthoc tests were employed to analyze pain, anxiety, SBP, DBP, HR, and RR within groups. Measurements from RCSQ were used as a covariate since research has shown that participants' pain intensity and anxiety level are severely impacted by deprived sleep quality during the preoperative and postoperative periods . Both the chi-squared test and Fisher's exact test were used to analyze categorical variables. Statistical significance was defined as a p-value < 0.05.