Abstract
Background
heart rate variability (HRV) is an important part of cardiovascular response to stress. Literature about the utility of HRV to predict intubation and invasive mechanical ventilation (IMV) need in Covid-19 patients is scarce. We analysed if HRV metrics could be used to identify, in the first 24 hours from admission in the intensive care unit (ICU), those patients who were going to need IMV during their stay.
Methods
we conducted a prospective single-centre observational study. Adult patients admitted in the ICU with respiratory failure due to RT-PCR-confirmed SARS-CoV-2 but not under IMV were included. Electrocardiogram (EKG) was recorded at least for 15 minutes at 500 Hz during a stable sitting condition, in the morning time. Power spectrum was obtained using wavelets. We also analysed non-linear HRV dynamics.
Results
27 patients were included. We found no differences in HRV metrics between groups. However, in the linear regression model for ICU length-of-stay (ICU LOS), we found that DFA⍺2 (OR -64.16; 95% CI: -3.497–0.832, P = 0.013), Fi02 (OR 0.37; 95% CI: 0.032–0.71, P = 0.033) and temperature (OR 16.02; 95% CI: 3.537–28.5, P = 0.014) were associated with longer ICU LOS. When performing bivariate correlation in patients lately intubated (Spearman`s test, n = 15), only DFA⍺2 was correlated (r -5.11, p = 0.05) with ICU LOS.
Conclusion
We found that HRV on ICU admission did not discriminate patients that might require IMV. DFA⍺2 was the HRV variable with the strongest association with ICU LOS along with other easy-to-collect clinical variables. These results could be helpful for newer prognostication tools.