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Peláez-Coca MD, Hernando A, Lozano MT, Bolea J, Izquierdo D, Sánchez C. Heart Rate Variability to Automatically Identify Hyperbaric States Considering Respiratory Component. SENSORS (BASEL, SWITZERLAND) 2024; 24:447. [PMID: 38257541 PMCID: PMC11154234 DOI: 10.3390/s24020447] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 01/04/2024] [Accepted: 01/08/2024] [Indexed: 01/24/2024]
Abstract
This study's primary objective was to identify individuals whose physiological responses deviated from the rest of the study population by automatically monitoring atmospheric pressure levels to which they are exposed and using parameters derived from their heart rate variability (HRV). To achieve this, 28 volunteers were placed in a dry hyperbaric chamber, where they experienced varying pressures from 1 to 5 atmospheres, with five sequential stops lasting five minutes each at different atmospheric pressures. The HRV was dissected into two components: the respiratory component, which is linked to respiration; and the residual component, which is influenced by factors beyond respiration. Nine parameters were assessed, including the respiratory rate, four classic HRV temporal parameters, and four frequency parameters. A k-nearest neighbors classifier based on cosine distance successfully identified the atmospheric pressures to which the subjects were exposed to. The classifier achieved an 88.5% accuracy rate in distinguishing between the 5 atm and 3 atm stages using only four features: respiratory rate, heart rate, and two frequency parameters associated with the subjects' sympathetic responses. Furthermore, the study identified 6 out of 28 subjects as having atypical responses across all pressure levels when compared to the majority. Interestingly, two of these subjects stood out in terms of gender and having less prior diving experience, but they still exhibited normal responses to immersion. This suggests the potential for establishing distinct safety protocols for divers based on their previous experience and gender.
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Affiliation(s)
- María Dolores Peláez-Coca
- Centro Universitario de la Defensa de Zaragoza, 50090 Zaragoza, Spain; (M.T.L.); (J.B.)
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, 50009 Zaragoza, Spain; (A.H.); (C.S.)
| | - Alberto Hernando
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, 50009 Zaragoza, Spain; (A.H.); (C.S.)
| | - María Teresa Lozano
- Centro Universitario de la Defensa de Zaragoza, 50090 Zaragoza, Spain; (M.T.L.); (J.B.)
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, 50009 Zaragoza, Spain; (A.H.); (C.S.)
| | - Juan Bolea
- Centro Universitario de la Defensa de Zaragoza, 50090 Zaragoza, Spain; (M.T.L.); (J.B.)
| | - David Izquierdo
- GTF Group, I3A Institute, University of Zaragoza, 50009 Zaragoza, Spain;
| | - Carlos Sánchez
- BSICoS Group, I3A Institute, University of Zaragoza, IIS Aragón, 50009 Zaragoza, Spain; (A.H.); (C.S.)
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Sánchez C, Hernando A, Bolea J, Izquierdo D, Rodríguez G, Olea A, Lozano MT, Peláez-Coca MD. Enhancing Safety in Hyperbaric Environments through Analysis of Autonomic Nervous System Responses: A Comparison of Dry and Humid Conditions. SENSORS (BASEL, SWITZERLAND) 2023; 23:s23115289. [PMID: 37300016 DOI: 10.3390/s23115289] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/26/2023] [Accepted: 05/31/2023] [Indexed: 06/12/2023]
Abstract
Diving can have significant cardiovascular effects on the human body and increase the risk of developing cardiac health issues. This study aimed to investigate the autonomic nervous system (ANS) responses of healthy individuals during simulated dives in hyperbaric chambers and explore the effects of the humid environment on these responses. Electrocardiographic- and heart-rate-variability (HRV)-derived indices were analyzed, and their statistical ranges were compared at different depths during simulated immersions under dry and humid conditions. The results showed that humidity significantly affected the ANS responses of the subjects, leading to reduced parasympathetic activity and increased sympathetic dominance. The power of the high-frequency band of the HRV after removing the influence of respiration, PHF⟂¯, and the number of pairs of successive normal-to-normal intervals that differ by more than 50 ms divided by the total number of normal-to-normal intervals, pNN50¯, indices were found to be the most informative in distinguishing the ANS responses of subjects between the two datasets. Additionally, the statistical ranges of the HRV indices were calculated, and the classification of subjects as "normal" or "abnormal" was determined based on these ranges. The results showed that the ranges were effective at identifying abnormal ANS responses, indicating the potential use of these ranges as a reference for monitoring the activity of divers and avoiding future immersions if many indices are out of the normal ranges. The bagging method was also used to include some variability in the datasets' ranges, and the classification results showed that the ranges computed without proper bagging represent reality and its associated variability. Overall, this study provides valuable insights into the ANS responses of healthy individuals during simulated dives in hyperbaric chambers and the effects of humidity on these responses.
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Affiliation(s)
- Carlos Sánchez
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain
| | - Alberto Hernando
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain
| | - Juan Bolea
- Departamento de Física, Centro Universitario de la Defensa de Zaragoza, Academia General Militar, 50090 Zaragoza, Spain
| | - David Izquierdo
- GTF Group, I3A Institute, University of Zaragoza, 50018 Zaragoza, Spain
| | - Germán Rodríguez
- Departamento de Ingeniería y Técnicas Aplicadas, Centro Universitario de la Defensa de San Javier, Academia General del Aire, 30729 Murcia, Spain
| | - Agustín Olea
- Centro de Buceo de la Armada de Cartagena, 30205 Murcia, Spain
| | - María Teresa Lozano
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain
- Departamento de Física, Centro Universitario de la Defensa de Zaragoza, Academia General Militar, 50090 Zaragoza, Spain
| | - María Dolores Peláez-Coca
- BSICoS Group, I3A Institute, IIS Aragón, University of Zaragoza, 50018 Zaragoza, Spain
- Departamento de Física, Centro Universitario de la Defensa de Zaragoza, Academia General Militar, 50090 Zaragoza, Spain
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