BackgroundHeart rate variability (HRV) has been used to assess cardiac autonomic activity in critically ill patients, driven by translational and biomarker research agendas. Several clinical and technical factors can interfere with the measurement and/or interpretation of HRV. We systematically evaluated how HRV parameters are acquired/processed in critical care medicine.MethodsPubMed, MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (1996–2016) were searched for cohort or case–control clinical studies of adult (>18 years) critically ill patients using heart variability analysis. Duplicate independent review and data abstraction. Study quality was assessed using two independent approaches: Newcastle–Ottowa scale and Downs and Black instrument. Conduct of studies was assessed in three categories: (1) study design and objectives, (2) procedures for measurement, processing and reporting of HRV, and (3) reporting of relevant confounding factors.ResultsOur search identified 31/271 eligible studies that enrolled 2090 critically ill patients. A minority of studies (15; 48%) reported both frequency and time domain HRV data, with non-normally distributed, wide ranges of values that were indistinguishable from other (non-critically ill) disease states. Significant heterogeneity in HRV measurement protocols was observed between studies; lack of adjustment for various confounders known to affect cardiac autonomic regulation was common. Comparator groups were often omitted (n = 12; 39%). This precluded meaningful meta-analysis.ConclusionsMarked differences in methodology prevent meaningful comparisons of HRV parameters between studies. A standardised set of consensus criteria relevant to critical care medicine are required to exploit advances in translational autonomic physiology.Electronic supplementary materialThe online version of this article (doi:10.1186/s40635-017-0146-1) contains supplementary material, which is available to authorized users.

Performance of both monitors improves as age increases. Our results suggest a need for the development of new monitor algorithms or calibration to better account for the age-specific EEG dynamics of younger patients.

Background The aim of this study was to investigate the effects of listening to Tibetan music on anxiety and endocrine, autonomic, cognitive responses in patients waiting for urologic surgery. Methods Sixty patients waiting for surgery were enrolled to the study. They were randomized in music (M) and control (C) groups. The M group listened to a low-frequency Tibetan music for 30 min (T0–T30) through headphones, and the C group wore headphones with no sound. The State Trait Anxiety Inventory Questionnaire (STAI) Y-1 was administered at T0 and T30. Normalized low (LFnu) and high frequencies (HFnu) of heart rate variability, LF/HF ratio, and galvanic skin response (GRS) data were analyzed at T0, T10, T20, T30, and T35. The salivary α-amylase (sAA) samples were collected at T0, T35, and T45. Results In the M group, the STAI Y-1 score decreased at T30 versus baseline (p < 0.001), sAA levels decreased at T35 versus T0(p=0.004), and GSR remained unchanged. In the C group, the STAI Y-1 score remained unchanged, sAA level increased at T35 versus T0(p < 0.001), and GSR slightly increased at T35 versus baseline (p=0.359). LFnu was lower, and HFnu was significantly higher (T10–T30) in M versus C group. Mean LF/HF ratio slightly reduced in the M group. Conclusions Our results suggest that preoperative listening to relaxing Tibetan music might be a useful strategy to manage preoperative anxiety.