Variations in heart rate during rest and deep breathe in pregnant and nonpregnant women in rural area

Balasaheb B Vikhe; Smita Jagannath Mokal; Muktpal M Bhalerao; Ramachandra G Latti

doi:10.4103/jdmimsu.jdmimsu_156_20

ORIGINAL ARTICLE

Year : 2020 | Volume : 15 | Issue : 2 | Page : 272-275

Variations in heart rate during rest and deep breathe in pregnant and nonpregnant women in rural area

Balasaheb B Vikhe, Smita Jagannath Mokal, Muktpal M Bhalerao, Ramachandra G Latti
Department of Physiology, Rural Medical College, Loni, Maharashtra, India

Date of Submission	23-Apr-2020
Date of Decision	30-Apr-2020
Date of Acceptance	10-May-2020
Date of Web Publication	21-Dec-2020

Correspondence Address:
Dr. Smita Jagannath Mokal
Department of Physiology,Rural Medical College, Pravara Institute of Medical Sciences (Deemed to be university), Loni - 413 736, Maharashtra
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jdmimsu.jdmimsu_156_20

Abstract

Introduction: Pregnancy is associated with various physiological changes. There is an increase in heart rate (HR) due to increase volume overload or decrease baroreceptor sensitivity. It occurs mainly due to changes in the autonomic activity. The aim of the study was to assess the HR response during rest and deep breath in pregnant women in the different trimester and to compare with nonpregnant women. Material and Methods: In this case-control observational study, after the approval of the institutional ethics committee and board of research committee a total of 160 women aged from 20 to 25 years without any recent history of respiratory diseases were selected. One hundred and twenty participants were pregnant (case group) and 40 were nonpregnant (control group). The case group was equally divided into three trimesters. Resting HR (RHR) and HR response to deep breathing (E: I ratio) were measured in both the study group by automatic “Cardiac Autonomic Neuropathy Analyzer” Statistical analyses were performed by One-way analysis of variance between the study groups and P < 0.05 was taken as significant. Results: Pregnancy is associated with a significant increase in RHR in 1^st, 2^nd, and 3^rd trimester of pregnancy as compared to nonpregnant (control). In all trimesters of pregnancy, there was a significant decrease in HR during deep breathing as compared to nonpregnant women. Conclusion: These observed changes possibly reflect decreased vagal baroreflex control of the heart.

Keywords: Autonomic, baroreflex, deep breathing, pregnancy, resting heart rate

How to cite this article:
Vikhe BB, Mokal SJ, Bhalerao MM, Latti RG. Variations in heart rate during rest and deep breathe in pregnant and nonpregnant women in rural area. J Datta Meghe Inst Med Sci Univ 2020;15:272-5

How to cite this URL:
Vikhe BB, Mokal SJ, Bhalerao MM, Latti RG. Variations in heart rate during rest and deep breathe in pregnant and nonpregnant women in rural area. J Datta Meghe Inst Med Sci Univ [serial online] 2020 [cited 2021 Jan 16];15:272-5. Available from: http://www.journaldmims.com/text.asp?2020/15/2/272/304244

Introduction

Pregnancy is associated with various physiological and metabolic changes. Increase in heart rate (HR) and stroke volume results in an increased cardiac output (CO) during pregnancy.^[1],[2] It is found that the HR of a pregnant woman steadily increases throughout the pregnancy. In the last trimester of pregnancy, there can be an increase of 10–20 beats in HR from the resting HR (RHR).^[3] This adaptive changes occur during pregnancy may be due to changes in autonomic control mechanisms. Gestational hormones, increase levels of circulating prostaglandins, increase heat production in the pregnant women leads to a decline in systemic vascular resistance. As pregnancy advances, there is aortocaval compression by the enlarged gravid uterus, it comprises venous return and CO and leads to increased sympathetic nervous activity and low parasympathetic activity. In pregnancy, a rise in HR starts between 2 to 5 weeks and continues well into the third trimester.^[4] An increase in the HR during pregnancy is due to increase in plasma volume.^[5] This altered HR response may be a consequence of physiological adaptation to volume overload and a decreased baroreflex sensitivity.^[6] In normal pregnancy the HR variability (HRV) to Valsalva maneuver, deep breathing test, was found to be significantly lower.^[2] Valsalva maneuver suggests cardiac parasympathetic tone was reduced in resting-state during mid-pregnancy.^[7] The HR response to deep breathing is regarded as one of the sensitive test of autonomic nervous function.^[8] The rise in HR during pregnancy is necessary for the pregnant woman as well as expected for proper baby growth.^[9] The autonomic functions test is a noninvasive method. It has the advantage of having minimal risk to the mother and the fetus. The study was carried out to assess the HR response during rest and deep breathe (parasympathetic tests) in pregnant women in different trimester and to compare with nonpregnant women.

Material and Methods

This case-control observational study was carried out in a tertiary Hospital. The study was carried out for 2 years, from May 2014 to May 2016, after the approval of the institutional ethics committee and board of research committee.

The study participants were taken from the rural area and rural tertiary hospital. A total of 160 women aged from 20 to 25 years without any recent history of respiratory diseases were selected. 120 participants were pregnant (case group) and 40 were nonpregnant (control group). The case group was equally divided into three trimesters. A written consent was obtained from all the willing participants (pregnant and nonpregnant women) before the start of the study. Pregnant women visiting the rural hospital for routine antenatal care checkup were included in the study. Participants both pregnant and nonpregnant women free from any systemic illness which can affects cardiovascular function, for example, Congestive cardiac failure, hypertension and able to complete the tests for cardiovascular autonomic activity were included in the study. Participants with a history of addiction to tobacco, alcohol and history of any type of long-term medication that will affect cardiovascular autonomic functions were excluded. The following anthropometric data i.e., name, age (years), height (cm), weight (kg), gestational age, were obtained. RHR and HR response to deep breathing (E: I ratio) were measured in pregnant women and healthy nonpregnant women. The RHR and E: I ratio were measured by automatic “Cardiac Autonomic Neuropathy Analyzer” Statistical analyses were done by One-way analysis of variance between the study groups and P < 0.05 was taken as significant.

Assessment of cardiovascular autonomic activity (parasympathetic tests)

Resting heart rate

Procedure

The participant was relaxed, lying down comfortably and the HR was recorded for 1 min in lead II of electrocardiogram (ECG).^[2] Normal RHR is 60–90 beats/min.

Heart rate response to deep breathing (E: I ratio)

E: I ratio is the ratio of HR during expiration and inspiration.

Procedure

The participant was relaxed, lie down comfortably on the bed and was asked to take deep breaths slowly in and out, approximately at 6 breaths per minute, i.e., 5 s inspiration and 5 s expiration for 1 min while the ECG recording continued. E: I ratio >1.20 is normal. E: I ratio ≤1.20 is abnormal.^[10]

Ethical Clearance

Ethical approval for this study (PMT/PIMS/RC/2013/26) was provided by the Ethical Committee of Pravara Institute of Medical Sciences (Deemed to be university), on 04/04/2013.

Results

Age and height when compared between pregnant women in all three trimesters and nonpregnant women, there is no significant difference observed. There is a significant difference seen in the 2^nd, 3^rd trimester of pregnant women with nonpregnant women when weight was compared as shown in [Table 1].

Table 1: Comparison of anthropometric parameters between nonpregnant and pregnant women (all trimester of pregnancy)

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The RHR is statistically less and HR response to deep breathe (E: I ratio) is more in nonpregnant women as compared with pregnant women in the first trimester, as shown in [Table 2].

Table 2: Comparison of mean±standard deviation values of parasympathetic tests in nonpregnant and 1^st trimester of pregnancy

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The RHR is less and HR response to deep breathe (E: I ratio) is more statistically in nonpregnant women as compared with pregnant women in the second trimester, as shown in [Table 3].

Table 3: Comparison of mean±standard deviation values of parasympathetic tests in nonpregnant and 2^nd trimester of pregnancy

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The RHR is less and HR response to deep breathe (E: I ratio) is more statistically in nonpregnant women as compared with pregnant women in the third trimester, as shown in [Table 4].

Table 4: Comparison of mean±standard deviation values of parasympathetic tests in nonpregnant and 3^rd trimester of pregnancy

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The RHR and HR response to deep breathe (E: I ratio) in pregnant women of 1^st and 2^nd when compared it is found that the resting RHR in 1^st trimester is statistically less as compared to 2^nd trimester and the E: I ratio is statistically more as shown in [Figure 1].

Figure 1: Comparison of parasympathetic tests (resting heart rate and E: I ratio) between 1^st and 2^nd trimester of pregnancy

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The RHR and HR response to deep breathe (E: I ratio) in pregnant women of the 1^st and 3^rd trimester when compared it is found that the RHR in 1^st trimester is statistically less as compared to 3^nd trimester and the E: I ratio is statistically more as shown in [Figure 2].

Figure 2: Comparison of Parasympathetic tests (resting heart rate and E: I ratio) between 1^st trimester and 3^rd trimester of pregnancy

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The RHR and HR response to deep breathe (E: I ratio) in pregnant women of the 2^nd and 3^rd trimester when compared it is found that the RHR in 2^nd trimester is statistically less as compared to 3^nd trimester, but there is no significant difference seen in E: I ratio as shown in [Figure 3].

Figure 3: Comparison of Parasympathetic tests (resting heart rate and E: I ratio) between 2^nd and 3^rd trimester of pregnancy

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Discussion

RHR response was evaluated in all the pregnant and nonpregnant (control). The mean and standard deviation (SD) of RHR in control, 1^st, 2^nd_, and 3^rd trimesters were 77.09 ± 6.24, 82.77 ± 11.01, 88.56 ± 9.84, and 95.06 ± 16.13, respectively. RHR showed a significant (P < 0.05) increase in 1^st, 2^nd_, and 3^rd trimester when compared to nonpregnant (control). The increase in HR in all the three trimester of pregnant women as compared to nonpregnant women may be attributed to a significant decrease in vagal baroreflex in pregnant women. The findings of the present study are similar to earlier studies. Stewart in his study of adaptation of the maternal heart in pregnancy found a rise in HR starts between two to 5 weeks and continues well into the third trimester.^[4] HR increased by approximately 15% in the 5^th week and its increase after 8^th week to a maximum of approximately 85–90 beats per minute.^[11],[12] HRV and baroreflex sensitivity are reduced in pregnancy in comparison with nonpregnant state.^[13],[14]An increased HR during pregnancy is mediated by the lower level of parasympathetic/vagal discharge.^[15] Our results showed a similar significant rise in all trimesters. Similar changes in HR were obtained when studied in the left lateral position.^[16] Thomas Walther found an increase in HR in pregnant women during the second half of pregnancy.^[17] Robson reported increase in HR synchronously by 10–15 beats per minute in pregnancy, so the CO begins to rise.^[18] Ekholm and Erkkola observed that pregnancy imposes a good deal of functional strain on the cardiovascular system, many important and reversible changes take place in the cardiovascular dynamics of the body during normal pregnancy.^[19]

The response of HR to deep breathing was recorded in all the pregnant and nonpregnant (control). Mean and SD of control, 1^st, 2^nd_, and 3^rd trimesters are 1.42 ± 0.22, 1.27 ± 0.14, 1.21±0.09, and 1.17 ± 0.11, respectively. E: I ratio showed a significant decline in the 1^st, 2^nd and 3^rd trimester when compared to nonpregnant (control). There was a statistically significant difference in E: I ratio when 1^st trimester was compared with 2^nd and 3^rd trimester of pregnancy. Hwever, there was no-significant difference between the E: I ratio of 2^nd trimester and 3^rd trimester (P > 0.05). The finding of the present study is in conformity with earlier studies, which showed that there is decrease in HR response during deep breathing as gestational age advances.^[16] A study done by Ekholm EMK evaluated HR response to deep breathing at 22–29 weeks of gestational age in 60 pregnant women and 62 nonpregnant women. HR response was significantly reduced (P < 0.001) in the pregnant group than in controls.^[19] Ekholm et al evaluated autonomic function by deep breathing test in 90 healthy pregnant women and 90 nonpregnant women. The E: I ratio was significantly lower (P < 0.05) in pregnant women.^[20] The basis of our findings may be at multiple levels of neuraxis. The response is primarily due to fluctuation in parasympathetic output to the heart, which is hypothesized to be decreased in pregnancy.^[11] It may be due to reduced baroreceptor sensitivity, impaired vagal afferents to the brain and impaired ability of the brain stem to properly recognize the different signal.^[21]

Conclusion

Pregnancy was associated with a significant increase in RHR in 1^st, 2^nd and 3^rd trimester of pregnancy as compared to nonpregnant (control). The RHR showed significant difference when the various trimester groups were compared with one another. These observed changes possibly reflect decreased vagal baroreflex control of the heart. In the study a significant decrease in E: I ratio was observed. In all trimesters of pregnancy, there was a significant decrease in HR during deep breathing. There was a significant difference in E: I ratio when 1^st trimester was compared with the 2^nd and 3^rd trimester of pregnancy. But there was no such difference observed when 2^nd trimester was compared with the 3^rd trimester of pregnancy. These observed changes possibly reflect decreased activity at multiple levels of neuraxis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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