Heart rate variability changes as an indicator of decompression-related physiological stress.

Many aspects of the physiological stress related to the exposure to the hyperbaric environment have been studied, but no research has been made to evaluate the impacts of scuba diving on heart rate variability (HRV). We investigated the effects of a simulated dive to 557 KPa (45 meters of salt water) for a 30-minute bottom time on the frequency and time domains estimators of HRV. Electrocardiogram records were obtained with superficial electrodes for 30 minutes before the simulated dive and, subsequently, for one hour after the dive. Each of these time-series was then subdivided into non-overlapping windows of 256 consecutive R-R intervals. A control group was submitted to the same protocol, breathing the same gases used in the simulated dive, while not being exposed to the hyperbaric environment. In the control group we observed a significant increase in SDNN (the square root of the variance of the R-R intervals), RMSSD (the square root of the mean squared differences of successive R-R intervals), and in two bands (high and low) of the power spectrum of frequencies. The subjects in the simulated dive presented only an increase in the low-frequency estimator without any further relevant changes in other estimators of HRV. This study suggests that the low-frequency increase without concomitant high-frequency increase might be an indicator of the physiological stress caused by decompression and that such a dissimilarity in responses might be correlated to the dive-related impairment of the endothelial function.

Proteomic profiling identifies N-acetylmuramoyl-l-alanine amidase as a novel biomarker of sepsis.

AIM: Sepsis is a critical condition that leads to high mortality and is the most common cause of death in intensive care units. Despite exhaustive efforts by the scientific community, a reliable biomarker for diagnosis, evolution and prognosis of sepsis is still lacking. Results & methodology: Here, using high-throughput proteomics, we describe N-acetylmuramoyl-l-alanine amidase as a novel candidate for differentiating infectious and noninfectious inflammatory syndromes. DISCUSSION & CONCLUSION: This is the first description of N-acetylmuramoyl-l-alanine amidase as a biomarker that can be used alone or in conjunction with other biomarkers to facilitate the diagnosis of sepsis in the critically ill.