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Schirato et al. | Journal of Clinical and Translational Research 2024; 10(5): 269-282 273

x ' − min( ' )x decompression profile did not exhibit a significant change (i.e.,
, kh
x , kh = max ( 'x h ) min( ' )− h x h (IV) SDNN: 43.39 ± 2.29 – 46.3 ± 3.84; p = 0.21). Both profiles
from 19.09 ± 1.43 to 25.4 ± 3.19 (p = 0.014) in the shallow
Where x is the normalized variable. displayed a significant increase in the RMSSD index, i.e.,
k,h
A confusion matrix was computed to assess the accuracy decompression profile and from 20.62 ± 1.73 to 24.7 ± 2.61
of the algorithm in attributing the results observed for each (p = 0.003) in the deep decompression profile (Figure 1).
volunteer to the respective decompression profile. Both pre-dive baseline SDNN and RMSSD values were not
statistically different between profiles (Figure 2).
3. Results In addition, a comparison between post-dive SDNN and
3.1. HRV RMSSD divided by their pre-dive values (respectively, defined
as SDNN and RMSSD ratios) is displayed in Figure 3. Notably,
An overall increase in variability was observed for both the shallow decompression profile generated higher values,
profiles. For the deep decompression profile, the frequency domain though the difference was not statistically significant.
indicators LF, total LFs (very LF + LF), and HF increased but
were not statistically significant. LF as a fraction of HF and total 3.2. Blood assay
variability, respectively, and HF as a fraction of total variability did Red blood cells, hematocrit, hemoglobin, neutrophils,
not exhibit significant changes. In the time domain, RMSSD was and platelet counts were different between pre- and post-dive
significantly increased in post-dive values. SDNN also displayed a measurements. A statistically significant reduction in red blood
tendency to increase, though not statistically significant (Table 3). cells was observed in the deep decompression profile, while the
The shallow decompression profiles also displayed an overall reduction observed in the shallow decompression profile was
increase in variability. In the frequency domain, HF and LF as not significant (Figure 4).
a fraction of HF demonstrated a significant increase. In the time Similarly, a statistically significant reduction in hemoglobin
domain, SDNN and RMSSD post-dive values significantly was observed in the deep decompression profile, while the
increased (Table 4). reduction in hemoglobin in the shallow decompression profile
The shallow decompression profile resulted in an increase
in post-dive variability, observed from SDNN (i.e., from was not significant (Figure 5).
Both profiles reported platelet count reduction post-dive,
42.66 ± 2.35 to 49.43 ± 4.02; p = 0.039), while the deep
but the reduction was only statistically significant for the deep
decompression profile (Figure 6).
Table 3. Heart rate variability for the deep decompression profile
Meanwhile, the neutrophil count increased post-dive in both
Parameter Pre‑dive Post‑dive p profiles but was only significant in the shallow decompression
LF (ms ) 418.00±77.37 545.01±89.09 0.071 profile (Figure 7).
2
Total LFs (ms ) 176.18±96.73 151.51±132.61 0.060 Finally, post-dive hematocrit values were slightly lower
2
HF (ms ) 77.93±15.74 124.50±21.59 0.696 than pre-dive values in both decompression profiles, but no
2
LF/HF ratio 7.31±1.16 8.79±2.00 0.145 statistically significant differences between pre- and post-dive
LF as a ratio of total variability 0.20±0.02 0.24±0.03 0.059 values or between profiles were observed.
HF as a ratio of total variability 0.03±0.00 0.04±0.01 0.097
RMSSD 20.62±1.73 24.76±2.61 0.003 3.3. Flow cytometry
SDNN (ms) 43.39±2.29 46.31±3.84 0.217 Pre- and post-dive neutrophil-, endothelium-, and platelet-
Note: Data arepresented as mean±standard error. derived MP counts in the deep and shallow decompression
Abbreviations: LF: Low frequency; HF: High frequency; SDNN: Standard deviation
of the normal-to-normal R-R interval; RMSSD: Root mean squared differences of profiles are displayed in Figures 8 and 9, respectively, and detailed
successive R-R intervals. in Tables 5 and 6, respectively. These results are consistent with
the increased post-dive neutrophil count (Figure 7).
Table 4. Heart rate variability for the shallow decompression profile
Parameter Pre‑dive Post‑dive p 3.4. Clustering analysis
LF (ms ) 468.04±67.46 647.86±133.48 0.057 The clustering algorithm was able to distinguish between the
2
Total LFs (ms ) 663.60±88.75 555.03±171.94 0.050 decompression profiles using values from the pre- and post-dive
2
2
HF (ms ) 61.99±9.46 96.15±19.51 0.025 ratios of HRV indicators, blood assay, and MP production with
LF/HF ratio 8.97±1.03 9.59±1.43 0.031 an accuracy of 0.68 (confidence interval [CI]: 0.4817 – 0.8204;
LF as a ratio of total variability 0.25±0.03 0.23±0.03 0.138 p = 0.07). Figure 10 presents the two clusters of results created
HF as a ratio of total variability 0.03±0.00 0.03±0.01 0.232 by the algorithm.
RMSSD 19.09±1.43 25.43±3.19 0.014
SDNN (ms) 42.66±2.35 49.43±4.02 0.039 4. Discussion
Note: Data arepresented as mean±standard error. In recent years, numerous studies have demonstrated that
Abbreviations: LF: Low frequency; HF: High frequency; SDNN: Standard deviation decompression sickness is a multifactorial condition that involves
of the normal-to-normal R-R interval; RMSSD: Root mean squared differences of
successive R-R intervals. the activation of many biochemical pathways, and its mechanisms
DOI: https://doi.org/10.36922/jctr.24.00021