Study design
A sequential explanatory mixed-method approach was employed in this study to achieve the research objectives. The initial data collection process consisted of collecting quantitative data, followed by an analysis of the data, and then using the results to collect qualitative data The initial data collection process included the collection of quantitative data, followed by an analysis of the data and the use of the results to further collect qualitative data [27]. Because of the importance of the qualitative part of the research in achieving the research objectives, more weight was given to the qualitative part than to the quantitative part. The reason for using the quantitative part was used at the beginning of the research to obtain an information-rich sample and purposeful selection of participants to enter the qualitative part (participant selection model) and to help design or modify qualitative interview questions [28]. The research project was approved by the Research Ethics Committee of the Asadabad School of Medical Sciences (ethical code IR. ASAUMS. REC.1402.021). All methods were performed in accordance with the guidelines and regulations of the Ethics Committee.
Settings and participants
Quantitative study
The research population for the quantitative study was made up of EMTs who were chosen by census method and worked in emergency bases in Hamadan city (2022). However, the sample size formula was used in a limited population to determine the appropriate number of participants to achieve an acceptable power (80%). This was done by taking into account a relative error of 10% (r = 10%) and a confidence interval of 95% (1-α/2 = 95%), as well as a 22% prevalence of PTSD (p = 22%) found in the study by Iranmanesh et al. As a result, a sample size estimate of 251 people (n) was determined. It should be mentioned that 307 operational technicians were working in the Hamadan emergency bases at the time of the study [29].
$${n}_{0}=\frac{{Z}_{1-\frac{\alpha }{2}}^{2}\left(P\right)\left(1-P\right)}{{\left(rp\right)}^{2}}$$
$$n=\frac{n}{1+\frac{{n}_{0}}{307}}$$
n0: sample size in an infinite population, n: Sample size in a limited population, p: prevalence of PTSD, r: relative error
The criteria for participation in the quantitative study included operational EMT, willingness to participate, more than one year of work experience, and no known neurological or mental illness. In addition, EMTs who had experienced stress outside of work, such as the death of a loved one, in the previous 8 weeks were excluded from the study. In total, 259 EMTs were included in the quantitative analysis
Data collection
The research tool in the quantitative part included a questionnaire with basic information consisting of two parts:1) demographic information, including age, work experience, educational qualification (nurse, emergency medical technician, operating room technician, anesthesia technician), education (postgraduate, bachelor’s, postgraduate, and higher), type of employment (formal, contract, contract, plan), marital status (married, single, separated), base location (city, road, air), number of missions, and number of shifts in the last month); And 2) the Post-Traumatic Stress Questionnaire (PCL-5), a 20-item self-report instrument (on a 5-point Likert scale) designed in 2013 by Weathers et al. developed in accordance with the new DSM-5 criteria, which aims to screen and preliminarily determine the rate of PTSD in EMTs [30].
After the necessary explanations for completing the questionnaires, the researcher gave the technicians basic information and the PCL-5 questionnaires and asked the participants to complete the first part (demographic characteristics) and then the PCL-5 checklist, after which they were given to the researcher. In the quantitative part of this study, the important objective was to identify EMTs with PTSD based on the scores obtained in the qualitative sample selection of the study.
Validity and reliability
Regarding the properties of the instrument (validity and reliability), numerous studies have been conducted in most countries, and almost all studies have indicated the validity and reliability of the PCL-5 for detecting PTSD [31,32,33,34]. The adequacy of the Persian version of this instrument was also evaluated by Sadeghi et al. who reported satisfactory validity and reliability (α = 90.7) of this instrument in identifying individuals with PTSD [30]. In the current study, the dependability of the PCL-5 total score, as measured by the Cronbach’s alpha coefficient, was 89%. For each aspect of aggressive thoughts, avoidance, negative changes in mood or cognition, and changes in arousal and irritability were observed (87%, 88%, 91%, and 90%, respectively), indicating adequate reliability of the instrument.
Settings and participants
Quantitative study
Considering that technicians with rich experience in dealing with prehospital emergencies should be identified and included, the sample selection in the qualitative phase was purposeful and based on the results of the instrument used in this phase. Therefore, a score of 33 was established as the optimal cutoff point for the transient diagnosis of PTSD in technicians [35, 36]. Based on the results of PCL-5, 19 technicians with a score above 33 were selected, of which 17 were interviewed (Fig. 1).
The stages of selecting participants in the quantitative and qualitative stage
Data collection
Qualitative data were collected through semi-structured interviews and face-to-face conversations with the corresponding author, who had 20 years of professional experience in pre-hospital care. The interview questions were designed by a team consisting of three assistant professors of nursing with pre-hospital experience and one assistant professor of clinical psychology. The interview guide included questions related to the research objectives, including describing a stressful workday and identifying specific missions that cause stress (Table 1). The interviews were conducted in the training base and in a separate room outside of the technicians’ working hours to ensure their privacy and confidentiality. The interviews lasted between 40 and 60 min, depending on the condition and willingness of the interviewee.
Trustworthiness
Several measures were taken to ensure the trustworthiness of the data [28]. First, the credibility of the results was ensured by the involvement of three expert supervisors who reviewed and confirmed data collection, analysis, and interpretation. This ensured that the results were valid and reliable. Purposive sampling was used to select participants and key informants with the maximum variation and appropriateness. This approach facilitated the inclusion of diverse viewpoints and ensured the authenticity of the data. To increase dependability, the accuracy of data analysis was verified by three independent researchers with experience in qualitative research who were assistant professors of nursing and clinical psychology. Their expertise and independent review made the analysis more and reduced the risk of bias or errors. Confirmability was ensured by providing transcripts, codes, and categories to the corresponding supervisor, an assistant professor of nursing, and two other faculty members with expertise in qualitative research. Their support of the analysis process adds an external perspective and increases the objectivity of their findings. Finally, transferability was ensured through a detailed explanation of the study characteristics, including the research context, participants, and the process of data collection and analysis. This information enabled further evaluation and assessment of the transferability of the study to other contexts or populations.
By implementing these measures, this study sought to ensure the trustworthiness and rigor of the data, thereby increasing confidence in the results and their potential for future research and practice.
Ethical consideration
In quantitative study participants were fully informed about the purpose and benefits of the study and about their voluntary participation. They were also assured that they could withdraw from the study at any time without prejudice. Written informed consent was obtained from all participants. The privacy and confidentiality of participants’ data was also maintained through the use of hypothetical codes and names. In quantitative part of study, participants in the interview process were treated with utmost respect and dignity. The study’s purpose, interview process, and any potential risks or benefits were thoroughly explained to the participants. They were given the freedom to choose whether or not to participate voluntarily, with the assurance that they could withdraw at any point without facing any negative consequences. Following the interview, a comprehensive debriefing session was conducted to further clarify the study’s objectives, address any inquiries, and offer additional support resources if necessary. If any of the questions caused distress to the participants, the interview was stopped and continued with their permission (Table 2).
Data analysis
Quantitative data analysis
In our study, we used the Persian version of the PCL-5, which demonstrated strong internal consistency with a Cronbach’s alpha of 0.92. To analyze the relationship between the independent variables (demographic factors) and the dependent variable (PCL-5 total score), both binary (univariate) and multivariate linear regression analyses were performed. Multiple linear regression analysis allowed multiple independent variables to be included simultaneously. The best fitting model was choking by examining the accuracy criteria. Collinearity, which refers to the intercorrelation between independent variables, was assessed using the Variance Inflation Factor (VIF). VIF values below 10 and above 0.2 are considered acceptable to avoid collinearity problems. The reliability of the PCL-5 questionnaire was evaluated using the test–retest method. The overall reliability of the questionnaire was 89%. Additionally, the reliabilities for each dimension were 87%, 88%, 91%, and 90%, respectively. These reliability values indicate that the PCL-5 questionnaire is a reliable tool for assessing PTSD symptoms in the present study. All statistical analyses were performed using SPSS version 21, with the significance level set at a 95% confidence interval and a two-tailed p-value of less than 0.05.
Qualitative data analysis
After collecting and analyzing quantitative data, the study proceeded to the qualitative phase using the contractual content method with Graneheim and Ladman’s approach [37]. The analysis units comprised transcribed interviews and observation notes, which were repeatedly read to gain a comprehensive understanding. Semantic units related to the data were summarized and assigned appropriate codes. The obtained codes were compared based on their similarities and differences, and similar codes were placed into categories and subcategories. Finally, themes were extracted by determining the relationships between categories. All coding and analyses were conducted using the MAXQDA10 data analysis software (VERBI Software, Berlin, Germany).
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