Intra-shift and Inter-shift Dynamics of Stress Index of Regulatory Systems in Medical Personnel of Mobile Emergency Medical Teams in Modern Conditions

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LIST OF ABBREVIATIONS

CI ― confidence interval

COVID-19 ― COronaVIrus Disease 2019

EMS ― emergency medical service

HRV ― heart rate variability

SI ― strain index of regulatory systems

INTRODUCTION

Medical specialists of mobile emergency medical teams (MEMT) are exposed to occupational risk of chronic stress and fatigue associated with peculiarities of their professional activities. The work in the EMS teams is associated with exposure to a combination of stress factors such as unpredictability of working situations and the necessity of taking decisions in conditions of information and time deficit, high level of personal responsibility for life and health of patients, deficit of sleep in 24-hour working regime, high levels of uncertainty and microbiological risks. Chronic occupational stress leads to strain of functional systems of an organism, increases the probability for development of cardiovascular diseases due to change in the balance between the central and autonomic regulation of the cardiovascular system [1]. In the conditions of spread of the new coronavirus infection (COronaVIrus Disease 2019, COVID-19), working rules and conditions of the MEMT changed, the range of occupational hazards expanded [2], which led to adverse alterations in the functional state of the central nervous system of workers [3]. The variability of the functional state of an organism is individual, and on exposure to the same factor, different workers may exhibit opposite reactions to the same loads [4, 5].

The aim of this study was to study the influence of professional activity on the functional condition of an organism of medical workers of mobile emergency medical teams in conditions of COVID-19 pandemic.

MATERIALS AND METHODS

The study was conducted on the base of the city clinical emergency medical setting of Ryazan; it was approved by the Local Ethics Committee of Ryazan State Medical University (Protocol No. 2 of 2019, October 08). The participants gave written informed consent. The sufficiency of the sample size was calculated according to the standard formula of repeated sampling using the method of correction of a small volume of the general totality.

Inclusion criteria were:

- work in the mobile emergency medical teams of the clinical emergency medical setting of Ryazan according to the schedule: three days of work, three days of rest;

- signing of the informed consent;

- age up to 65 years inclusive;

- length of service as a medical worker of a mobile emergency medical team more than 1 year;

- absence of medical contraindications to the 24-hour regime of work and to work in hazardous conditions.

A stringent epidemic situation and the pronounced shortage of personnel of EMC specialists established in the region have led to the actual absence of intervals between calls in teams of all specializations and to their equalization in the structure of the calls served. According to the Ambulance automated information system, the number of calls serviced by one team per shift ranged from 15 to 26 (on average 19.45 ± 3.37), the total time of one call was on average 45.46 ± 15.98 minutes. The workers that participated in the study, were exposed to similar occupational factors and characteristics of the labor process. The sample was being formed from May to October 2021 and included 67 medical workers (21 men and 46 women) of 150 workers of mobile teams that at the time of the study were working at the emergency medical setting according to the work schedules. Of the examined workers, 16 were doctors and 51 paramedics. The average age of the workers who took part in the study was 36.28 ± 2.82 years. The parameters of the functional state of the workers before and after work (n = 45), as well as at the beginning of two consecutive shifts (n = 28), were assessed.

As an objective method of monitoring of fatigue associated with the working activity, heart rate variability (HRV) was analyzed [6]. Cardiointervalometry is widely used in different studies, including the sphere of labor hygiene [7].

HRV was analyzed by the method of short-term (three-minute) photoplethysmography at rest in a sitting position with the installation of a pulse oximeter sensor unit of the NS-Psychotest. Profekstrim device (Russia) on the fourth finger of the non-dominant hand of the subject. Measurements were performed in the period from 7.00 to 8.00 a.m. in accordance with the daily schedule of work shifts at equal time intervals, which corresponded to the time interval of the greatest informative value for the comparative assessment of HRV [8]. As an estimated parameter of the degree of centralization of heart rate control, the strain index of regulatory systems (SI) proposed by R. M. Baevsky, was used [9].

Statistical processing was carried out using Excel 2007 software packages (Microsoft, USA) with the Data Analysis add-in. The normality of the distribution of variables was checked using Kolmogorov–Smirnov test. The comparison of relative values was carried out using Wilson (1927) and ÷2 (Poisson distribution) test; the average values of quantitative variables with normal distribution are represented as Md ± tm (Md is the arithmetic mean of the parameter, expressed in absolute numbers; m is the error of the mean, t is the criterion of reliability for the given sample size). The Student's paired t-test was used to compare dependent variables. The hypothesis was assumed as statistically reliable at p < 0.05.

RESULTS

Since the SI is one of sensitive parameters of centralization of the heart rate, let us consider distribution of workers with different dynamics of the above parameter in the working shift (Table 1).

 

Table 1. Structure of Workers with Different Individual Dynamics of Strain Index of Regulatory Systems during Shift

Group of Workers	Increase in strain index of regulatory systems		Decrease in strain index of regulatory systems
	P (%), 95% CI	Md, t-test	P (%), 95% CI	Md, t-test
Women, n = 34	44.12	85.43	55.88	73.77*
	[28.88; 60.55]	1.72	[39.45; 71.12]	2.97
Men, n = 12	50.00	50.83*	50.00	69.32*
	[25.38; 74.62]	3.25	[25.38; 74.62]	2.52
It total, n = 46	54.35	74.75*	45.65	72.49***
	[40.18; 67.85]	2.47	[32.15; 59.82]	3.81

Notes: * ― р < 0.05; *** ― р < 0.001; CI ― confidence interval; Md ― arithmetic mean value of the parameter expressed in absolute numbers; Р ― a share of examined persons with the specified SI dynamics

 

By the end of the shift, in more than half of the medical workers of the MEMT, a statistically reliable increase in SI by 74.75 units (p = 0.021) was recorded. The physiological study did not reveal any statistically significant differences in the distribution of workers with different dynamics of SI during work shift depending on gender. At the same time, in the analysis of the parameters of individual dynamics of SI during shift among men, statistically significant parameters of increase and decrease in SI were established in equal proportions. As for women, 55.88% of them had a decrease in SI by on average 73.77 (p = 0.010), while in the rest of women its average dynamics was not statistically confirmed.

Since the age has an effect on the adaptation reserves of a human organism [10], let us consider dynamics of SI in the workers of different age groups (Table 2).

 

Table 2. Structure of Workers with Different Individual Dynamics of Strain Index of Regulatory Systems in Different Age Groups during Shift

Group of Workers	Increase in strain index of regulatory systems		Decrease in strain index of regulatory systems
	P (%), 95% CI	Md, t-test	P (%), 95% CI	Md, t-test
Under 30, n = 16	31.25	34.12	68.75	93.25*
	[14.16; 55.60]	1.89	[44.40; 85.84]	2.89
30–39 years, n = 16	75.00*	28.73**	25.00*	75.05
	[50.50; 89.82]	3.76	[10.18; 49.50]	1.93
40 and above, n = 13	61.54	169.18	38.46	32.75
	[35.52; 82.29]	1.93	[17.71; 64.48]	2.28
÷2 = 6.467; р = 0.04 with 2 degrees of freedom

Notes: * ― р < 0.05; ** ― р < 0.01; CI ― confidence interval; Md ― arithmetic mean value of the parameter, expressed in absolute numbers; Р ― a share of examined persons with the specified SI dynamics

 

From the data presented, it follows that in 75% (p < 0.05) of workers aged 30–39 years, SI increased by on average 28.73 (p = 0.003) in the dynamics of the work shift, and only in each fourth worker in this age group a decrease in this parameter was recorded. A similar trend was observed in the older age group (40 years and more), where in 61.54% of workers increase in SI was recorded by the end of the shift. On the contrary, in 68.75% of the subjects under 30, SI significantly decreased by 93.25 (p = 0.016). In general, we can talk about a statistically reliable influence of age on the dynamics of SI according to the results of the work shift (÷2 = 6.467; p = 0.04).

Let us consider the influence of the length of service on SI dynamics according to the results of the work shift (Table 3).

 

Table 3. Structure of Workers with Different Individual Shift Dynamics of Strain Index of Regulatory Systems Depending on Service Length

Group of Workers	Increase in strain index of regulatory systems		Decrease in strain index of regulatory systems
	P (%), 95% CI	Md, t-test	P (%), 95% CI	Md, t-test
0–5 years, n = 14	28.57	19.35*	71.43	110.78*
	[11.72; 54.64]	4.62	[45.35; 88.28]	3.07
6–10 years, n = 12	75.00	54.36*	25.00	42.20
	[46.77; 91.11]	3.24	[8.89; 53.22]	2.98
11 years and above, n = 20	60.00	108.52	40.00	36.01*
	[38.66; 78.12]	1.76	[21.88; 61.34]	3.33
÷2 = 6.069; р = 0.049 with 2 degrees of freedom

Notes: * ― р < 0.05; CI ― confidence interval; Md ― arithmetic mean value of the parameter expressed in absolute numbers; Р ― a share of examined persons with the specified SI dynamics

 

The results of the study evidence a statistically significant effect of length of service in this field on the distribution of subjects with different dynamics of SI (÷2 = 6.069; p = 0.049). With that, there is a clear tendency to decrease in the resistance of the cardiovascular system with increase in the service length, as evidenced by the predominance of workers with increase in SI by the end of the work shift in the groups with service length of 6–10 years and 11 years and more; 75% with average increase by 54.36 (p = 0.012) and 60.00% with average increase by 108.52 (p > 0.05), respectively. On the contrary, in 71.43% of the subjects with the working period up to 5 years inclusive, a decrease in SI by on average 110.78 (p = 0.013) was recorded by the end of the work shift, which may indicate a higher resistance to stress.

The analysis of individual changes in SI of the personnel of the mobile emergency medical teams at the beginning of two consecutive shifts will permit to assess the effectiveness of the rest and of the recovery of the functional state (Table 4).

 

Table 4. Structure of Workers with Different Individual Dynamics of Strain Index of Regulatory Systems at the Beginning of the Consecutive Shifts

Group of Workers	Increase in strain index of regulatory systems		Decrease in strain index of regulatory systems
	P (%), 95% CI	Md, t-test	P (%), 95% CI	Md, t-test
Women, n = 19	57.89	95.05**	42.11	60.59
	[36.28; 76.86]	3.63	[23.14; 63.72]	1.74
Men, n = 9	66.67	35.47*	33.33	102.86
	[35.42; 87.94]	2.07	[12.06; 64.58]	1.49
In total, n = 28	60.71	74.02***	39.29	90.83*
	[42.41; 76.73]	3.92	[23.57; 57.59]	2.43

Notes: * ― р < 0.05; ** ― p< 0.01; *** ― р < 0.001; CI ― confidence interval; Md ― arithmetic mean value of the parameter, expressed in absolute numbers; Р ― a share of examined persons with the specified SI dynamics

 

The study showed that by the beginning of the consecutive shift, 60.71% of medical workers of the mobile emergency medical teams included in the study, showed a significant increase in SI on average by 74.02 at р = 0.001 in comparison with the beginning of the previous shift. This tendency was present in several gender groups. Thus, in 57.89% of women and 66.67% of men, the individual values of SI increased on average by 95.05 (р = 0.011) and 35.47 units (р = 0.002), respectively.

No statistically reliable gender differences were found in the percentage composition of mobile emergency medical teams with differently directed SI in the dynamics of two consecutive shifts. Nevertheless, In the age groups of 30–39 years, 40 years and above, SI increased in 58.33% and 62.50% of subjects by on average 47.36 (p = 0.025) and 97.04 units, respectively (p = 0.029).

A physiological study showed a statistically significant effect of service length on the distribution of workers in groups with different dynamics of SI (÷2 = 7.313; p = 0.026). Thus, in the group of medical personnel with 6–10-year service length, in 88.89% of the subjects a significant in SI increase by on average 58.01 (p = 0.017) was recorded by the beginning of the next shift. A similar tendency was observed in the workers with service length of 11 years or more, 63.64% of which showed an increase in SI by on average 70.04 units (p > 0.05). On the contrary, 75.00% of the subjects with up to 5 years of experience inclusive, showed a decrease in SI by the beginning of the next work shift.

DISCUSSION

The balance between the influence of the sympathetic and parasympathetic divisions of the autonomic nervous system and of central regulatory mechanisms on the work of the heart is manifested by heart rate variability. It was established that in the different stages of professional activity of medical workers of emergency services, there is regress of HRV parameters mediated by parasympathetic nervous system with simultaneous increase in the indices reflecting sympathetic influences and centralization of the regulation of the heart rate [11].

A low level of HRV is associated with a decrease in the functional state of an organism induced by chronic stress and fatigue [4], besides, it can be a marker of cardiovascular pathology [5, 12]. It is established that the greatest negative deviations of parameters of workers of medical emergency services occur during direct fulfilment of their professional duties for rendering medical assistance to patients. At the same time, in the conducted studies, there was noted a sufficient ability of the parameters of the autonomic nervous system of workers to recover in a prolonged scheduled rest [13]. Meanwhile, under constant stressful working conditions, the HRV parameters in the period of non-work recover slowly or even do not recover at all 14]. In this study, a clear tendency was traced to some predominance of individuals with increase in SI at the end of the work shift, which evidences centralization of the heart rate and can be a sign of strain of the functional systems of an organism. Some predominance of the proportion of women with a reliable decrease in SI by the end of the work shift is confirmed by the data of scientific studies that evidence a weaker reaction of the cardiovascular system to stress factors in women in comparison with men [15].

In ageing, the ability of an organism to adaptation declines, which was confirmed in the study of the dependence of HRV parameters on age [10]. The data obtained by us, also show reduction of resistance to load with age of workers, which is manifested by increase in the share of individuals with signs of centralization of the heart rate at the end of the work shift in the older age groups.

The analysis of individual alterations of SI in the personnel of mobile medical emergency teams at the beginning of two consecutive work shifts identified the tendency to predominance of workers with increase in SI by the beginning of the consecutive shift. These parameters may indicate both a non-effective rest, and a stressful effect of work as a factor of danger for individual health in conditions of a pandemic. The conducted physiological study identified the absence of a complete recovery of functional systems during scheduled rest in most part of workers with the service length more than five years. On the contrary, in workers with the working period less than five years, the recovery processes are more effective. A distinct tendency to reduction of the effectiveness of rest among the subjects with increase of the working period was revealed.

CONCLUSIONS

1. Professional activity of the personnel of mobile emergency teams is associated with a high level of strain of the functional systems of an organism, which is manifested by increase in the strain index of regulatory systems by the end of the work shift in the majority of examined individuals .
2. The dynamics of the increase in the strain index of regulatory systems in comparison with the parameters at the beginning of consecutive work shifts in most cases evidences a low effectiveness of recovery of the functional state of an organism of workers in the period of scheduled rest.
3. The service length has the highest influence on increase in the strain of regulatory systems in medical specialists of the medical emergency service, which is an evidence of negative influence of the working conditions of medical personnel of mobile medical emergency teams on the functional state of an organism.

ADDITIONAL INFORMATION

Funding. The research was carried out with the financial support of the Russian Foundation for Basic Research in the framework of scientific project No. 20-313-90005.

Conflict of interests. The authors declare no conflicts of interests.

Contribution of the authors: T. A. Bolobonkina — collection, translation and analysis of material, writing the text; A. A. Dement’yev — research concept and design, editing; N. V. Minayeva — editing, concept of the review; M. M. Lapkin — research design, correction of research methods; P. A. Kulagin — research design, correction of research methods. All authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work.

About the authors

Tatyana A. Bolobonkina

Ryazan State Medical University

Author for correspondence.
Email: bolobonkina@bk.ru
ORCID iD: 0000-0003-1796-6023
SPIN-code: 2251-0350
Russian Federation, Ryazan

Aleksey A. Dement’yev

Ryazan State Medical University

Email: dementiev_a@mail.ru
ORCID iD: 0000-0003-3038-5530
SPIN-code: 3797-9108

MD, Dr. Sci. (Med.), Associate Professor

Russian Federation, Ryazan

Natalya V. Minaeva

Ryazan State Medical University

Email: shatrnat@gmail.com
ORCID iD: 0000-0003-0599-924X
SPIN-code: 2965-2704

MD, Cand. Sci. (Med.)

Russian Federation, Ryazan

Mihail M. Lapkin

Ryazan State Medical University

Email: m.lapkin@rzgmu.ru
ORCID iD: 0000-0003-1826-8307
SPIN-code: 5744-5369

MD, Dr. Sci. (Med.), Professor

Russian Federation, Ryazan

Pavel A. Kulagin

Ryazan State Medical University

Email: zu.pavel@gmail.com
ORCID iD: 0000-0002-5284-0875
SPIN-code: 3623-3309
Russian Federation, Ryazan

References

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