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 Table of Contents  
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


Department of Physiology, Rural Medical College, Loni, Maharashtra, India

Date of Submission23-Apr-2020
Date of Decision30-Apr-2020
Date of Acceptance10-May-2020
Date of Web Publication21-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
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdmimsu.jdmimsu_156_20

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  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 1st, 2nd, and 3rd 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 24];15:272-5. Available from: http://www.journaldmims.com/text.asp?2020/15/2/272/304244




  Introduction Top


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 Top


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 Top


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 2nd, 3rd 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 1st 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 2nd 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 3rd trimester of pregnancy

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

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The RHR and HR response to deep breathe (E: I ratio) in pregnant women of the 1st and 3rd trimester when compared it is found that the RHR in 1st trimester is statistically less as compared to 3nd 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 1st trimester and 3rd trimester of pregnancy

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The RHR and HR response to deep breathe (E: I ratio) in pregnant women of the 2nd and 3rd trimester when compared it is found that the RHR in 2nd trimester is statistically less as compared to 3nd 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 2nd and 3rd trimester of pregnancy

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  Discussion Top


RHR response was evaluated in all the pregnant and nonpregnant (control). The mean and standard deviation (SD) of RHR in control, 1st, 2nd, and 3rd 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 1st, 2nd, and 3rd 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 5th week and its increase after 8th 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, 1st, 2nd, and 3rd 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 1st, 2nd and 3rd trimester when compared to nonpregnant (control). There was a statistically significant difference in E: I ratio when 1st trimester was compared with 2nd and 3rd trimester of pregnancy. Hwever, there was no-significant difference between the E: I ratio of 2nd trimester and 3rd 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 Top


Pregnancy was associated with a significant increase in RHR in 1st, 2nd and 3rd 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 1st trimester was compared with the 2nd and 3rd trimester of pregnancy. But there was no such difference observed when 2nd trimester was compared with the 3rd 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.



 
  References Top

1.
Capeless EL, Clapp JF. Cardiovascular changes in early phase of pregnancy. Am J Obstet Gynecol 1989;161:1449-53.  Back to cited text no. 1
    
2.
Ekholm EM, Piha SJ, Antilla KJ, Erkkola RU, Cardiovascular autonomic reflexes in mid pregnancy. Br J Obstet Gynaecol 1993;177-82.  Back to cited text no. 2
    
3.
Pivarnik JM, Lee W, Clark SL, Cotton DB, Spillman HT, Miller JF. Cardiac output responses of primi-gravid women during exercise determined by the direct Fick technique. Obstet Gynecol 1990;75:954-9.  Back to cited text no. 3
    
4.
Stewart Hunter, Stephen C Robson. Adaptation of maternal heart in pregnancy. Br Heart J 1992;68:540-3.  Back to cited text no. 4
    
5.
Heiskanen N, Saarelainen H, Valtonen P, Lyyra-Laitinen T, Laitinen T, Vanninen E, et al. Blood pressure and heart rate variability analysis of orthostatic challenge in normal human pregnancies. Clin Physiol Funct Imaging 2008;28:384-90.  Back to cited text no. 5
    
6.
Ekholm EM, Piha SJ, Erkkola RU, Antila KJ. Autonomic cardiovascular reflexes in pregnancy. A longitudinal study. Clin Auton Res 1994;4:161-5.  Back to cited text no. 6
    
7.
Avery ND, Wolfe LA, Amana CE, Davies GAL. Effect of human pregnancy on cardiac autonomic function above and below ventilatory threshold. J Appl Physiol 2001;90:321-28.  Back to cited text no. 7
    
8.
Watkins PJ, Mackay JD. Cardiac denervation in diabetic neuropathy. Ann Intern Med 1980;92:304-07.  Back to cited text no. 8
    
9.
Sodre MP. Maternal Physiology Changes During Pregnancy [document on the Internet]. Available from: http://www.medstudents.com.br/ginob/ginob5.htm. [Last accessed on 2015 Apr 13].  Back to cited text no. 9
    
10.
Gazioglu K, Kaltreider NL, Rosen M, Yu PN. Pulmonary function during pregnancy in normal women and in patients with cardiopulmonary diseases. Thorax 1970;25:445-50.  Back to cited text no. 10
    
11.
Clapp JF, Seaward BL, Sleamaker RH, HIser J. Maternal physiologic adaptation to early human pregnancy. Am J Obset Gynecol 1988;159:1456-60.  Back to cited text no. 11
    
12.
Shapiro LM. Echocardiographic features of impaired ventricular function in diabetes mellitus. Br Heart J 1982;47:439-44.  Back to cited text no. 12
    
13.
Panja S, Bhowmick K. A study of cardiovascular autonomic function in normal pregnancy. Al Am J Med Sci 2013;6:170-5.  Back to cited text no. 13
    
14.
Phatak MS, Kurhade GA. A longitudinal study of antenatal changes in lung function tests and importance of postpartum exercises in their recovery. Indian J Physiol Pharmacol 2003;47:352-6.  Back to cited text no. 14
    
15.
Kuo CD, Chen GY, Yang MJ, Lo HM, Tsai YS. Biphasic changes in autonomic nervous activity during pregnancy. Br J Anaesth 2000;84:323-9.  Back to cited text no. 15
    
16.
Atkins AF, Watt JM, Milan P, Davies P, Crawford JS. A longitudinal study of cardiovascular dynamic changes throughout pregnancy. Eur J Obstet Gynecol Reprod Biol 1981;12:215-24.  Back to cited text no. 16
    
17.
Walther T, Wessel N, Baumert M, Stepan H, Voss A, Faber R. Longitudinal analysis of heart rate variability in chronic hypertensive pregnancy. Hypertens Res 2005;28:113-8.  Back to cited text no. 17
    
18.
Robson SC, Hunter S, Boys RJ, Dunlop W. Serial study of factors influencing changes in cardiac output during human pregnancy. Am J Physiol 1989;256:H1060-5.  Back to cited text no. 18
    
19.
Ekholm EM, Erkkola RU. Autonomic cardiovascular control in pregnancy. Eur J Obstet Gynecol Reprod Biol 1996;64:29-36.  Back to cited text no. 19
    
20.
Ekholm EM, Erkkola RU, Piha SJ, Jalonen JO, Metsälä TH, Antila KJ. Changes in autonomic cardiovascular control in mid-pregnancy. Clin Physiol 1992;12:527-36.  Back to cited text no. 20
    
21.
Voss A, Malberg H, Schumann A, Wessel N, Walther T, Stepan H, et al. Baroreflex sensitivity, heart rate, and blood pressure variability in normal pregnancy. Am J Hypertens 2000;13:1218-25.  Back to cited text no. 21
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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