Enhancing Safety in Hyperbaric Environments through Analysis of Autonomic Nervous System Responses: A Comparison of Dry and Humid Conditions.

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.

Global longitudinal strain assessment of cardiac function and extravascular lung water formation after diving using semi-closed circuit rebreather.

PURPOSE: The aim of the present investigation is to study the relationship of ventricular global longitudinal strain (GLS) and ultrasound lung comets (ULC) formation to establish a link between extravascular pulmonary water formation and cardiac contractile dysfunction. METHODS: This is a prospective observational study including 14 active military divers. The subjects performed two sea dives of 120 min each with a semi-closed SCUBA circuit at 10 m depth. Divers were examined at baseline, 15 min (D1) and 60 min (D2) after diving. The evaluation included pulmonary and cardiac echography (including speckle tracking techniques). Blood samples were drawn at baseline and after diving, assessing hs-TnT and Endothelin-1. RESULTS: ULC were detected in 9 (64.2%) and 8 (57.1%) of the subjects after D1 and D2 respectively. No differences were found in right and left ventricular GLS after both immersions (RV: Baseline: - 17.9 4.9 vs. D1: - 17.2 6.5 and D2: - 16.7 5.8 s-1; p = 0.757 and p = 0.529; LV: Baseline: - 17.0 2.3 vs. D1: - 17.4 2.1 and D2: - 16.9 2.2 s-1; p = 0.546 and p = 0.783). However, a decrease in atrial longitudinal strain parameters have been detected after diving (RA: Baseline: 35.5 9.2 vs. D1: 30.3 12.8 and D2: 30.7 13.0 s-1; p = 0.088 and p = 0.063; LA: Baseline: 39.0 10.0 vs. D1: 31.6 6.1 and D2: 32.4 10.6 s-1; p = 0.019 and p = 0.054). CONCLUSION: In the present study, no ventricular contractile dysfunction was observed. However, increase pulmonary vasoconstriction markers were present after diving.

Fenomeno de Raynaud y buceo / Raynaud's phenomenon and diving

El fenómeno de Raynaud se caracteriza por vasoespasmos episódicos de los dedos las manos y de los pies provocados por exposición al frío o situaciones de estrés. La aparición de estos procesos determina el cambio de coloración de piel. Presentamos el caso clínico de un varón sano de 24 años, alumno de un curso de buceador profesional que durante las fases iniciales del curso; ejercicios de natación en superficie, experimenta una sensación de dolor con cambios de coloración en ambas extremidades superiores e inferiores. Discutimos los posibles diagnósticos ante este cuadro clínico y sobre todo sus implicaciones para la practica del buceo (AU)

Raynaud's phenomenon is characterised by episodic vasospasm of the fingers and toes typically precipitated by exposure to cold or when you are feeling stressed. When this happens, blood can 't get to the surface of the skin and the affected areas turn white and blue. We present a case report of primary Raynaud's phenomenon during a training scuba diving. A healthy 24-year-old Caucasian male made a swimming exercise on surface. After this activity he noted pain and skin discoloration on both legs and arms. A review of the posible diagnoses and fitness to dive in presented herein (AU)

Influencia de las condiciones medio ambientales en la tolerancia al Ocígeno en animales de experimentación / Influence of the environmental conditions in the oxygen toxicity

INTRODUCCIÓN:La toxicidad del oxígeno está condicionada por la presiónp arcial del gas y el tiempo de exposición al mismo, además de otros factores invariables o variables. Nuestro objetivo es determinar el rango de humedad relativa en una atmósfera hiperóxica y normobárica par que la tolerancia al oxígenos sea mayor. MÉTODO: Se realizaron 3 grupos de experimentación que se introdujeron en a cámara con la atmósfera deseada. El grupo 1 respiró oxígeno húmedo (humedad <50%)(n=27). el grupo 2 (humedad <50%)(n=22). el tercer grupo fue el control (humedad ambiental)(n=11). durante todo el experimento se toma registro de la concentración de O2, CO2, humedad, temperatura, flujo, presion de la botella y la sintomatología clínica asociada al consumo de O2. RESULTADOS: Los sujetos del grupo control presentaron una supervivencia media de 103.18+/-40,32 horas, superior a los otros dos grupos siendo el grupo húmedo el que menos supervivencia media presentó con 87,27+/-34,36 horas, siendo estas diferencias significativas (p=0,01). Las lesiones más graves aparecen en el grupo húmedo y seco. CONCLUSIONES:Estos datos indican que humedades relativas comprendidas entre 30%-60% son las óptimas para disminuir el riesgo de presentar un cuadro de intoxicación por oxígeno bajo condiciones de hiperoxia normobárica

INTRODUCTION:The oxygen toxicity is conditioned by the partial pressure of the gas and the time of exposure, besides other invariable or variable factors. Our objective is to determine the interval of relative humidity ina hyperoxic and normobaric atmosphere so that the tolerance of the oxygen is bigger. METHOD: 3 experimentation groups of rats were introduced in the chamber with the normobaric and hyperoxic atmosphere. Group 1 breathed humid oxygen (humidity>50%) (n=27). Group 2 (humidity <50%)(n=22). the third group was the control (environmental humidity)(n=11). the following data were written down. concentration of O2, CO2, humidity, temperature, flow, pressure of the bottle and the clinical symptomatologic which is associated with the consumption of CO2. RESULTS: The average survival of the control group was of 103.18+/-40.32 hours, it´s higher than the other two groups. The humid group has the survival the lowest survive rate of 87.27+/-34.36 hours, these differences are significant (p=0.01). the most serious injuries appeared in the humid and dry groups. CONCLUSIONS: These data indicate that relative humidy between 30%-60% are recommended in order to decrease the risk of an oxygen toxicity ina hyperoxic normobaric atmosphere