Mammography is widely used for the early detection and diagnosis of breast diseases in women. However, breast compression and immobilization during mam- mography usually give a pain to the examinee      . In addition, the radiological technologist often directly grasps the breast and spreads it further in order to obtain the most suitable X-ray images. Therefore, mammography causes not only physical burden but also psychological distress   . The physical burden associated with mammography has been assessed by several subjective and objective methods  -  . As the subjective method, visual analogue scale (VAS)  and McGill pain questionnaire (MPQ)  were used to predict the pain during mammography   . Objective criteria such as muscle activities   , electrical stimulation  and pupil sizes  were related with physical burden during mammography. Psychological distress during mammography has been also investigated by assessing autonomic nervous system function related with heart rate variability (HRV)  . According to this investigation, the sympathetic nerve was active not only during mammography but also before mammography, and moreover, sympathetic activity before mammography was the most dominant. It meant that women undergoing mammography were under stress and they were most stressful when they were waiting to undergo mam- mography in particular.
Several investigators have then reported as to the alleviation of pain and distress associated with mammography      . Patient-controlled compression was tested as a method to alleviate pain  . With this method, one of the breasts was compressed by a radiographer and the other was compressed by the participant. In 71% of the participants, self-compression resulted in significantly less pain than compression by a radiographer without a difference in the adequacy of the image quality and compression of the breast. The usefulness of radiolucent cushions in the pain alleviation during mammography was demonstrated   . However, their use is debatable because of the high cost since these cushions are single-use. For the alleviation of pain and anxiety associated with mammography, effects of listening to a relaxation audiotape before and during mammography were examined  . As a result, they did not reduce subjective reports of anxiety or pain. On the other hand, watching funny video during mammography was effective to relieve the pain  . More feasible schemes for the alleviation of distresses associated with mammography should be developed.
Recently, some investigations suggested that a pet robot provided the human with a good effect, e.g., reduction of stress hormones   , improvement of brain functioning  , and positive psychological effects in social relationships   . A communication robot is further expected to engender mental effects, such as pleasure and relaxation  . Actually, the proportion of the parti- cipants in whom effects on pleasure and relaxing could be recognized tended to be higher in the communication robot group relative to those in the control robot group  . Considering these findings, the communication robot may yield successful effects on the alleviation of distress associated with mammography. Therefore, this study aimed to explore effects of the communication robot on distress reduction in mammography.
2. Materials and Methods
We used HRV to estimate the amount of distress associated with mammography. HRV is the coefficient of variation of the interval between R wave peaks on an electrocardiogram (ECG), and is a tool that represents the balance between the sympathetic and parasympathetic branches of the autonomic nervous system  . Frequency domain analysis was utilized for the variation in the R-R interval of the ECG. Low-frequency (LF: 0.04 - 0.15 Hz) components and high-frequency (HF: 0.16 - 0.42 Hz) components were obtained from the analyzed power spectrum. HF component reflects parasympathetic nerve activity, which is dominant at rest or a relaxed state. On the other hand, LF/HF is associated with sympathetic activity which is dominant at action or a tense state. In addition, heart rate (HR) is influenced by autonomic nervous activity related respiration and circulation and it fluctuates periodically. Thus, HR was also observed in this study. In short, we adopted and measured HR, LF and LF/HF as autonomic nervous indices. As an ECG device, we used Activetracer (GMS Co. AC-301A). This device is able to measure and record HR, HF and LF/HF at regular time intervals.
Experimental design is shown in Figure 1. Volunteers for this study were recruited through poster advertisements in School of Health Sciences, Niigata Uni- versity. There were approximately 500 students in the institution. About 75% of them were female. Nineteen healthy women (21 - 23 years of age) who contacted us were enrolled in this study. They were students at departments of nursing or radiological technology. All of them had not previously experienced mammogra- phy. The participants were given an explanation of the study objectives, methods, and safety, and their informed consent was obtained. This study was conducted from Aug. to Dec. in 2015 with the approval of the Research Ethics Committee of School of Medicine, Niigata University.
The participants were randomly assigned to either an experimental group or a control group. Ten participants were designated as the control group. The other nine participants were designated as the experimental group and talked with a com- munication robot before mammography (Figure 2). As the communication robot, we used PALRO (FUJISOFT Inc., Tokyo, Japan), which was a chatty, comforting
Figure 1. Experimental design. Participants were randomised to either the experimental group or the control group.
Figure 2. Communication robot PALRO with a participant.
EEG data was obtained throughout the experiment that consisted of three min rest phase, ten min communication phase and one min mammography phase. The participants underwent mammography for only medio-lateral oblique (MLO) view of right breast without X-ray irradiation. The degree of pain during mammography was assessed using a VAS immediately after the examination. The experimental group further responded to the VAS for assessment of enjoyment associated with communication with PALRO, and besides, they filled in a questionnaire. The VAS designed for this study is shown in Figure 4. Contents of the questionnaire will be shown in next “Results” section.
Figure 5 illustrates three time-series graphs of mean HR, mean HF and mean LF/HF of the experimental and the control groups. In the experimental group, HR hardly fluctuated during communication with PALRO [Figure 5(a)]. On the other hand, HF decreased gently and LF/HF fluctuated widely during communication with PALRO [Figure 5(b) and Figure 5(c)].
Figure 6 shows three bar charts of mean values of HR, HF and LF/HF in each phase, namely rest phase, communication (comm.) phase and mammography (MMG) phase. The differences in HR, HF and LF/HF between rest phase and mammography phase were statistically significant, respectively (p < 0.01). However, on the differences of HR, HF and LF/HR between rest phase and mammography phase, there were no significant differences between the experimental group and the control group.
Figure 7 indicates mean HF and mean LF/HF of the experimental group. In
Figure 3. Examples of communication words for PALRO (actually Japanese only) [PALRO user manual: http://www.palrogarden.net/palro/main/_userdata/PALRO_usermanual_ALL.pdf].
Figure 4. Visual analogue scale designed for this study.
Figure 7, mammography phase was further divided into positioning and breast compression. In particular, LF/HF was highest at positioning and suddenly
Figure 5. Time-series graphs of autonomic nervous indices. (a) HR, (b) HF, (c) LF/HF. The lines correspond to mean values of all participants’ data for each group. MMG is abbreviation of “mammography”.
decreased at breast compression.
Mean VAS scores for pain and enjoyment were shown in Figure 8. The VAS
Figure 6. Average values of autonomic nervous indices in each phase. (a) HR, (b) HF, (c) LF/HF. **: p < 0.01. The dotted lines indicate normal values of standard measures of HRV (HR: 60 beats/m, HF: 975 ± 203 ms2, LF/HF: 1.5 - 2.0). If the obtained HR is larger than the normal value, the subject may not be at a relaxed state at least. If the obtained HF is larger than the normal value, parasympathetic nerve may be active. If the obtained LF/HF is larger than the normal value, sympathetic nerve may be active.
Figure 7. Changes of mean HF and mean LF/HF in the experimental group. Mammography phase divided into positioning and breast compression.
Figure 8. Mean VAS scores for pain and enjoyment. **: p < 0.01.
scores of pain in the experimental group were significantly smaller than ones in the control group (p < 0.01). Table 1 summarizes responses to the questionnaire. Seven out of nine participants in the experimental group felt relaxed during communication with PALRO.
According to Figure 5, parasympathetic nerve activity of both groups was becoming dominant in rest phase, because HF was increasing and LF/HF was decreasing. This meant that all of participants were exactly close to a relaxed state during three min rest. In communication phase, LF/HF fluctuated widely. This may be due to the participant’s actions for conversation with PALRO. They were involved in communicating with PALRO. That enthusing must be a cause of fluctuation of LF/HF. When the participants were talking to PALRO, LF/HF
Table 1. Summary of responses to the questionnaire in the experimental group.
would become high. In contrast, when they were paying attention to PALRO’s action/talk, LF/HF would become low. According to responses of the questionnaire in Table 1, almost all of them enjoyed the communication with PALRO. Therefore, playing with PALRO would make them excited slightly. That would be why sympathetic activities of them were slightly dominant in communication phase. In mammography phase, we found that participants were in maximum tense state at the beginning of the examination, and their tensions reduced steadily during the examination. Such tendency was similar between the experimental group and the control group.
In Figure 6(a), all values of HR were larger than 60 beats/min that was the standard value of HR at rest in adults  . This meant that participants were a little stimulated state. HRs of the control group were larger than ones of the experimental group in both rest and mammography phases. In Figure 6(b), HF values of both groups in all phases were smaller than 975 ± 203 ms2 that was the normal value of standard measures of HF  . This meant that parasympathetic nervous functions were not active, and therefore participants were never a relaxed state. In Figure 6(c), LF/HF values of both groups in all phases were larger than 1.5 - 2.0 that was the normal value of standard measures of LF/HF  . This meant that sympathetic nervous functions were active and dominant, and therefore, participants were at action or a tense state. These results implied that mammography examinees would be in a kind of mental distress through the whole examination.
The results of statistical-significance test in Figure 6 indicated that communication with PALRO did not affected autonomic nervous functions during mam- mography. However, subjective pain degrees by VAS scores were significantly differrent between the experimental group and the control group, as shown in Figure 8. The experimental group was obviously in low level of subjective physical pain compared with the control group. This result suggested that communication with PALRO could alleviate a pain associated with mammography. Responses to the questionnaire indicated that the majority participants enjoyed communicating with PALRO and relaxed through it. The enjoyment usually inspires laughs and positive motivations. According to a book on pain relief  , positive emotions are associated with better outcomes in people with chronic pain with respect to improvements in their ability to cope with pain and in their social functioning  . Positive emotions also are associated with better responses to treat- ment, reduced disability and impairment of physical functioning, and improved health-related quality of life and coping   . Some investigators have reported that laughter is good medicine for pain   -  . The communication with a robot would produce positive emotions with sometimes laughs and it may relieve the pain associated with mammography.
Patients who are going to undergo mammography in a medical institution are usually forced to have waiting time before the examination. The waiting time must enhance the patient’s anxieties for mammography  . The findings of this study would lead to a wise use of the waiting time. Therefore, the placement of a communication robot in the waiting room or lobby of the medical institution may be recommended in near future.
This study has several limitations. We only employed all the people who contacted us for this study, as the result of our recruitment. The number of subject should further increase for the statistical robustness. An adequate sample size may be determined by power calculation. In this study, we only used PALRO as the communication robot. Recently, several kinds of communication robots except PALRO can be also accessed, such as “Pepper” (Softbank). Using other robot or plural robots may yield more successful knowledge on their effects of distress reduction in mammography. The communication time, ten min in this study, should be optimized to obtain more obvious usefulness of the communication robot on alleviation of anxiety and pain in mammography. These limitations would be overcome in our future work.
We explored effects of a communication robot on distress reduction in mammography. Autonomic nervous activities were observed before and during mammography. Degrees of subjective pain associated with mammography were also assessed. Unfortunately, the communication robot did not help to intensify parasympathetic nerve activities, which became dominant at rest or a relaxed state. On the other hand, the communication robot was useful for relieving subjective pain associated with mammography. In conclusion, communication with a robot before mammography would yield positive emotions and it would be related to the pain alleviation during mammography.
The authors thank Ms. Yuri Toyoda for assisting with experiments and data analysis. This study was supported by JSPS KAKENHI Grant Number 26463372.
Conflict of Interest
The authors declare that they have no conflict of interest.