This study showed that respiratory/heart rate fluctuations accurately measured using a non-wearable monitor were significantly associated with a dying cancer patient’s death during their final days of life. This finding suggests that continuous measurement of respiratory/heart rates by a non-wearable monitor can warn about death occurrence within several days of the death-day with some accuracy. It will be helpful for family members and care staff to aware imminent death among dying patients at home or in facilities, even in the absence of healthcare professionals at all times.
One of the key findings of this study was the clarification in the change in maximum, minimum, mean, and variance of respiratory and heart rates among dying cancer patients for 2 weeks before death, which were captured by a non-wearable monitor every minute. The maximum and minimum values measured by the monitor were significantly different from those routinely measured by nurses twice a day. In clinical practice, the vital signs of dying patients are unstable, such as a sudden decrease in respiratory rate per minute caused by respiratory disorders/apnea syndrome27,28 and a sudden increase in respiratory rate caused by acidosis.29 This study showed that the use of non-wearable monitors can accurately capture such changes in dying patients, thus the maximum and minimum values are different from those measured by nurses and showed a wide range.
The second important finding of this study was that the changes in maximum respiratory rate and mean heart rate could become warning signs of imminent death in the last 2 weeks of life among dying patients. This is because the maximum respiratory rate and mean heart rate were significantly associated with the occurrence of death within 72 hours. Previous studies that have examined the association between vital signs and prognosis captured vital signs by medical records just once or twice a day or only used the data from hospital admission. 7–11 In addition, no study has investigated the association between death occurrence and continuous measurement of respiratory/heart rates using a non-wearable monitor in dying cancer patients during the last days of life. A previous study showed a statistically significant increase in respiratory rate for the final days before death,30 while another study reported no statistically significant increase.8 This may be attributed to the roughness of data due to the low measurement frequency. In contrast to these previous findings, this study was able to continuously assess respiratory rate and heart rate using a monitor. Therefore, the results of this study suggest that two vital signs (respiratory rate and heart rate) measured by a monitor can warn about the imminent death of dying cancer patients in their last days with some accuracy, without considering the patient’s clinical situation, such as other vital signs (blood pressure, oxygen saturation, and temperature) and symptoms and drug use, captured from medical records widely. Additionally, the mean value of heart rate measured by the monitor did not significantly deviate from the nurse’s measurement, but the maximum/minimum of those deviated considerably between them. These deviations may be a region where the nurse could not observe (such as time zone and temporary change of patient status). This study suggests that continuous clinical observations of the maximum respiratory rate may be important for prognosis. We aim to continue to investigate the pathological conditions of dying cancer patients through measurements using such monitoring devices.
A third important result of this study is the clarification of the percentage of the probability of death within the following 72 hours using the maximum respiratory rate and mean heart rate. Although the percentage of prognosis due to these 2 variables before death varies individually and greatly ranged from 20–80% among patients, this study showed that the maximum respiratory rate and mean heart rate in some patients increased the probability of death within the next 72 hours. Therefore, we would like to increase the number of subjects to improve this accuracy in the future.
A recent review describing the current use of wearable monitors in oncology trials,15 proposed the importance of the potential use of wearable monitors to predict clinical outcomes, such as survival. Another recent review that summarized the ability of vital sign trends to predict clinical deterioration in patients with acute illness indicated that vital signs (i.e., respiratory rate, oxygen saturation, pulse, blood pressure, and temperature) are essential for early detection and timely intervention for preventive outcomes.30 Simultaneously, they also pointed out that several studies captured vital signs from medical records and that the best monitoring system is still unclear.17 Considering these studies, using a non-wearable noninvasive monitor to estimate imminent death of dying patients with some accuracy is considered beneficial. These may have great potential to contribute to future prognostication in advanced cancer, such as at home or in care facilities, in the absence of palliative care professionals at all times.
This study has several limitations. First, the sample size of this study was small, and because of the small sample size, it may not be possible to consider each patient’s clinical status, such as symptoms and drug use, when considering their prognosis. However, without adjusting for these situations, this study showed that the maximum respiratory rate and mean heart rate of dying cancer patients may be able to predict the possibility of death within the subsequent 72 hours. Second, the patients were from a single palliative unit, and monitoring devices used in this study could not measure the patients’ vital signs outside the patients’ beds.
If we are able to aware imminent death of dying cancer patients by measuring vital signs using a non-wearable device with some accuracy, at-home monitoring with few medical professionals will be possible in the future. Additionally, this could lead to the prevention of solitary death in the aging society worldwide, the relief of family’s grief, and the provision of appropriate symptom management by healthcare professionals for patients who cannot express distress close to death, thus contributing to the improvement of their quality of life. In future, we plan to increase the number of subjects and take into consideration the symptoms and drug use of the subjects with the aim of more accurately predicting the prognosis of dying cancer patients.