2.6 Data Extraction and Analysis
A tool was developed to guide the extraction of data from the studies (Polit & Beck, 2010). Data extraction is the essential process of reading and re-reading each study, to identify data to enable its quality appraisal and to answer the research question (Bettany-Saltikov, 2012). The data extraction tool used for this review is provided, completed, in Appendices 6 and 7. To ensure the tool was efficient and accurate, it was piloted on a number of the studies excluded during the full-text screening, and refined, prior to being used for the final data extraction.
2.7 Quality Appraisal and Data Analysis
Each of the six studies selected for the review were critically appraised. This involves a process of determining the methodological quality of the study (LoBiondo-Wood et al., 2019) and, therefore, its value in answering the research question. There are a variety of frameworks which can be used to guide critical appraisal (Moule & Goodman, 2009); however, the framework used for this review was that developed by the Critical Skills Appraisal Programme for randomised controlled trials (CASP, 2018). The completed critical appraisal is presented in Appendix 8.
The data from the studies was analysed using two broad processes. Quantitative analysis was undertaken, where relevant – for example: the pre- and post-intervention systolic and diastolic blood pressures from the participants in each study were pooled and averaged. Qualitative analysis was also undertaken, where relevant – for example, information relating to the effects of acupuncture on hypertension was organised into similar ‘themes’, or ideas, for reporting.
3.0 Findings and Critical Review
3.1 General Characteristics of the Selected Studies
3.1.1 Trial Location and Participants
As noted, six randomised controlled trials were selected for inclusion in this systematic review (Macklin et al., 2006; Flachskampf et al., 2007; Yin et al., 2007; Kim et al., 2012; Zheng et al., 2016; Zheng et al., 2018). These studies were conducted in the United States (Macklin et al., 2006), Germany (Flachskampf et al., 2007), South Korea (Yin et al., 2007; Kim et al., 2012) and China (Zheng et al., 2016; Zheng et al., 2018). The studies included an average of 147 participants, ranging from 30 patients (Zheng et al., 2016) to 428 patients (Zheng et al., 2018).
3.1.2 Trial Definition of Hypertension
Each of the trials included participants with diagnosed hypertension. In most of the trials (n=5, 83.3%), hypertension was diagnosed when a patient’s systolic blood pressure was ≥140mmHg, and/or their diastolic blood pressure was ≥90mmHg (Macklin et al., 2006; Flachskampf et al., 2007; Kim et al., 2012; Zheng et al., 2016; Zheng et al., 2018). Half of the trials (n=3, 50.0%) also specified an upper ‘acceptable’ limit on the systolic and diastolic blood pressure (Macklin et al., 2006; Kim et al., 2012; Zheng et al., 2018), perhaps to ensure the participants’ safety. It is important to note that one study also included patients with pre-hypertension: a systolic blood pressure of ≥120mmHg and/or a diastolic blood pressure of ≥89mmHg (Yin et al., 2007).
Half of the trials (n=3, 50.0%) only included patients with essential hypertension (Yin et al., 2007; Zheng et al., 2016; Zheng et al., 2018). ‘Essential hypertension’ is hypertension due to an undetermined, idiopathic cause (Bolivar et al., 2013). The other three trials also included people with secondary hypertension (Macklin et al., 2006; Flachskampf et al., 2007; Kim et al., 2012).
All six of the studies selected for inclusion reported participants’ average baseline systolic and diastolic blood pressures. Across all the trials, the average baseline systolic blood pressure for patients in the intervention group was 140.6mmHg, ranging from 131.0mmHg (Flachskampf et al., 2007) to 149.6mmHg (Mac
