Initially, 571 patients participated in the study. Subjects with less than 24hrs of continuous tracking data were excluded, with 492 patients remaining in the final analysis. As can be seen in Figure 2 a-c, the number of patients decreased throughout the monitoring period due to patients' discharge from the hospital, transfer to intensive care units (ICU), or death. As a result, we have decided to focus our analysis on the first five days (120hrs) after admission. Physiological measurements were recorded continuously every 15 minutes with a total of 3,215,334 measurements. For the raw, unfiltered data, measurements were collected during an average monitoring period of 75.26hrs (range 0-455), with 245.67±226.39 observations (±standard deviation) per patient. The analyzed filtered data included patients with at least 24hrs of tracking, and included observations from the first five days only. Measurements were collected during an average monitoring period of 74.78hrs (range 24-120) per patient (174.89±110.58).
Analysis of baseline parameters
Subject characteristics, along with mean values during the first 2hrs of monitoring (average of 8 measurements) for body temperature, SpO2, RR, heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), cardiac output (CO), cardiac index (CI), and systemic vascular resistance (SVR) for each sub-group are presented in Table 1. The first 2hrs served as a baseline monitoring period for each subject. Men (64% of the recruited patients) had a significantly higher BMI and weighed more than women (p < 0.001). Middle aged patients (men = 70%) had significantly higher weight (p < 0.001) than young (men = 64%), elderly (men = 66%) and >80-year-old (men = 44%) patients, and no differences in weight were detected between the three other age groups. Young patients had significantly (p < 0.01) lower BMI compared to the other groups, and no differences were noted between middle age, elderly, and >80-year-old patients. Patients with normal BMI (men = 56%) were significantly (p < 0.01) younger.
For baseline physiological measurements, an ANOVA analysis revealed a significant (p < 0.01) difference between men and women for body temperature, SpO2, HR, DBP and CO. When analyzing age groups, significant (p < 0.003) interactions were seen for all physiological measures recorded during the first 2hrs of admission. Lastly, only SpO2, RR, CO and CI were significantly (p < 0.01) different between BMI groups upon admission.
Trajectory of physiological vitals over five days from admission
Figure 3 provides an overall description of the nine vital signs in the 130 patients that fully completed five days of continuous monitoring. Overall, within the first 24hrs we found a significant increase in temperature, RR, and SVR, and a significant decrease in SpO2, DBP, CO and CI (p < 0.01 for all). These changes all appeared at the same time. For HR, SBP, CO and CI, the changes appeared in a repetitive pattern.
Further analysis is provided in Figure 4, where we show the results of repeated measures ANOVA tests performed to determine differences between groups during the same timeframe.
Body temperature (Figure 4a): In both males and females, temperature increased during the first 24hrs of monitoring, significantly higher among males (p < 0.001). From the second day, females showed a significant decrease in temperature until the fifth day (p < 0.001), while males' trajectory of temperature remained similar. Across the BMI groups, temperature increased similarly during the first 48hrs. A slight increase was noted in the normal weight group and decrease among the overweight and obese, but by the fifth day there were no differences within the BMI group. In the age group, temperature among the elderly was higher (p < 0.001) during the whole 5 days.
SpO2 (Figure 4b): SpO2 decreased in both males and females during the first 48hrs (p < 0.001 for both), with a higher decrease among males. Starting from 72hrs since admission, and throughout the next two days, females showed a quicker return to the baseline levels, while males remained with lower values (p < 0.03 between sex). Among the BMI sub-groups, similar trajectories were found, with higher SpO2 levels in the normal weight sub-group, a lesser level in the overweight, and the lowest SpO2 levels among the obese. In the age group, the young maintained SpO2 levels throughout the five days of hospitalization with a slight reduction (p = 0.044), while other sub-groups showed dynamic changes with lower SpO2 values.
Respiratory rate (Figure 4c): Within the first 48hrs from admission, RR increased significantly in males, obese patients, and in all age sub-groups (p < 0.01) except the young. At five days after admission, there were no significant differences between sex. During the whole five days of hospitalization, the overweight and obese sub-groups had higher RR as compared to the normal weight sub-group (p < 0.01). The young showed a significant increase (p = 0.044) in RR, and with no significant changes among the other sub-groups.
Heart rate (Figure 4d): During the first 48hrs, HR dropped among men, while increased among women (p < 0.01 and p < 0.01, respectively). From then on, the dynamics of HR behaved in opposite manners between sex, until day 5, in which both showed an increase, with males not reaching the baseline values and females showing a significant increase from baseline (p < 0.01). Young patients showed a mild increase during the first 24hrs, remaining stable until day 5, during which the levels decreased back to baseline levels. Middle aged and elderly had a gradual decrease until day 4, and both increased to levels similar to those at baseline at day five. Patients over 80 years had peak increases at 24 and 48hrs after admission, followed by a sharp decrease to baseline levels in day 3, followed by an increase until the end of day 5. Though patients in the age groups started with the same baseline, after 24hrs the normal weight and obese started to show dynamic decrease until the 5th day, while the overweight had an overall increase.
Systolic Blood Pressure (Figure 4e): SBP showed similar trends among sex, with higher levels among males at day 4 after admission, returning to similar values by day 5. Changes in SBP over five days of hospitalization were significantly different between age groups (p = 0.002). The young showed a decrease in SBP during the first 24hrs, remaining relatively stable during the next three days, followed by an increase in SBP to a level higher than the baseline on day 5. The middle age and the elderly were relatively stable during the five days of monitoring. The over 80 years sub-group had higher SBP values during the whole period, increasing to peak levels by 48hrs, showing a relatively sharp decrease to baseline levels on day 4, and increasing back on day 5. Obese patients showed a decrease trend in SBP until day 4, increasing back to baseline levels on day 5. Normal weight and overweight patients showed a changing pattern with a decrease trend in SBP, both reaching nadir on day 4, and showing increase to baseline levels on day 5.
Diastolic Blood Pressure (Figure 4f): Both sexes showed a decrease in DBP values during the first 4 days, women to a higher extent than men (p < 0.001), and in the fifth day both showed increase with values among women returning to the baseline level. Patients over 80 years showed relatively lower DBP values during the 5 days period, reaching a nadir at day 4 (p < 0.001). The young and elderly showed a decrease trend in the first 3 days (p < 0.01), returning close to baseline levels by day 5. Though the middle age sub-group had the highest DBP levels, they also had a similar trend of decrease until day 4, returning close to baseline level on day 5. Normal weight patients had a sharp decrease during the first 24hrs (p < 0.001), maintaining this level until the 4th day, followed by a sharp increase during the 5th day to baseline levels. Both overweight and obese had a milder decrease during the first 4 days with overweight returning to baseline levels in the 5th day, and the obese returning to a lower level than the baseline (p = 0.02).
Cardiac Output (Figure 4g): Males had a sharp decrease in the first 24hrs (p < 0.01), kept stable in the next 48hrs, followed by a sharp decrease in the 4th day, and an increase in the 5th day to a level below baseline. Females showed dynamic changes reaching peak high levels on each of days one to three, followed by a drop shortly after every peak, followed by a constant increase until reaching the highest peak on day 5 (p < 0.01). Young patients showed stable CO values during the whole five-day period. Middle age and elderly showed a slight decrease during the first 24hrs, followed by a dynamic trend, with middle aged returning to the baseline levels while the elderly did not show significant changes from baseline (p = 0.081). Patients over 80 years had a dynamic pattern of changes with peaks at 24hrs and 48hrs from admission (p < 0.01 and p = 0.02, respectively), followed by lower peaks and increasing again at day 5 after admission. All BMI sub-groups had decreased levels of CO in the first 24hrs.
Cardiac Index (Figure 4h): Both sexes started with the same CI values at baseline. Shortly after, a sharp increase was evident amongst females reaching its peak at 48hrs after admission (p < 0.001), while amongst males a sharp decrease was seen after 24hrs (p < 0.001), maintained until day 4, in which a further decrease was evident, and a moderate increase appeared on day 5, to levels lower than baseline (p < 0.001). Amongst the young, dynamic changes were not statistically significant, with similar values to baseline measured on day 5. Both middle aged and elderly showed decreases within the first 24hrs (p < 0.001 in both). From that moment on, the middle aged showed moderate increase, becoming more pronounced on the 5th day, returning to baseline levels. However, amongst the elderly, further decrease was evident on day 4, increasing slightly on day 5 (p < 0.001). Unlike other age sub-groups, the over 80 years started with a sharp increase in CI during the first 24hrs, followed by a sharp decrease and immediately followed with a higher increase by 48hrs after admission (p < 0.001). This was followed by an unstable decrease over the next two days, and a sharp increase at day 5 (p < 0.001). Normal weight and overweight patients had dynamic non-significant changes in CI, with values similar to the baseline at the end of day 5. However, obese had a lower baseline level of CI, further decreasing during the first 24hrs, and reaching a nadir at day 5 (p < 0.001).
Systemic Vascular Resistance (Figure 4i): Females had a higher SVR value at baseline as compared with males, and during the 5-day period showed consistent decrease until the end of monitoring (p < 0.001). Males started with an increase during the first 24hrs (p < 0.001), and remained relatively stable until day 5. Over 80 years started at a higher level of SVR at baseline, and showed continuous decrease until day 5. Other age sub-groups started at the same baseline, with the middle age showing an increase in the first 24hrs (p < 0.01) followed by continuous decrease until day 5, returning to baseline level. The elderly remained stable until an increase on day 4, returning to baseline levels on day 5. The young showed dynamic decrease until a nadir on day 4, followed by an increase on day 5 back to baseline levels. Normal and obese patients had dynamic changes over the five-day period without significance. Overweight patients showed continuous decrease during the five-day period (p < 0.01).