First Real-Life Data on the Diving Response in Healthy Children.

Swimming and diving are popular recreational activities, representing an effective option in maintaining and improving cardiovascular fitness in healthy people. To date, only little is known about the cardiovascular adaption to submersion in children. This study was conducted to improve an understanding thereof.

Unlocking the depths: multiple factors contribute to risk for hypoxic blackout during deep freediving.

Purpose: To examine the effect of freediving depth on risk for hypoxic blackout by recording arterial oxygen saturation (SpO) and heart rate (HR) during deep and shallow dives in the sea.

Methods: Fourteen competitive freedivers conducted open-water training dives wearing a water-/pressure proof pulse oximeter continuously recording HR and SpO. Dives were divided into deep (> 35 m) and shallow (10-25 m) post-hoc and data from one deep and one shallow dive from 10 divers were compared.

Underwater pulse oximetry reveals increased rate of arterial oxygen desaturation across repeated freedives to 11 metres of freshwater.

Introduction: Recreational freedivers typically perform repeated dives to moderate depths with short recovery intervals. According to freediving standards, these recovery intervals should be twice the dive duration; however, this has yet to be supported by scientific evidence.

Methods: Six recreational freedivers performed three freedives to 11 metres of freshwater (mfw), separated by 2 min 30 s recovery intervals, while an underwater pulse oximeter measured peripheral oxygen saturation (SpO) and heart rate (HR).

Case Studies in Physiology: Is blackout in breath-hold diving related to cardiac arrhythmias?

Syncope or "blackout" (BO) in breath-hold diving (freediving) is generally considered to be caused by hypoxia. However, it has been suggested that cardiac arrhythmias affecting the pumping effectivity could contribute to BO. BO is fairly common in competitive freediving, where athletes aim for maximal performance.

Corrigendum: Using Underwater Pulse Oximetry in Freediving to Extreme Depths to Study Risk of Hypoxic Blackout and Diving Response Phases.

[This corrects the article DOI: 10.3389/fphys.2021.

First Evaluation of a Newly Constructed Underwater Pulse Oximeter for Use in Breath-Holding Activities.

Studying risk factors in freediving, such as hypoxic blackout, requires development of new methods to enable remote underwater monitoring of physiological variables. We aimed to construct and evaluate a new water- and pressure proof pulse oximeter for use in freediving research. The study consisted of three parts: (I) A submersible pulse oximeter (SUB) was developed on a ruggedized platform for recording of physiological parameters in challenging environments.

Using Underwater Pulse Oximetry in Freediving to Extreme Depths to Study Risk of Hypoxic Blackout and Diving Response Phases.

Deep freediving exposes humans to hypoxia and dramatic changes in pressure. The effect of depth on gas exchange may enhance risk of hypoxic blackout (BO) during the last part of the ascent. Our aim was to investigate arterial oxygen saturation (SpO) and heart rate (HR) in shallow and deep freedives, central variables, which have rarely been studied underwater in deep freediving.

Thermal balance of spinal cord injured divers during cold water diving: A case control study.

Introduction: This study compared the thermal balance of spinal cord injured (SCI) divers and able-bodied (AB) divers during recreational cold-water dives.

Methods: Ten divers (5 AB, 5 SCI) in matched pairs dived in a shallow lake (temperature 6°C) for 30 to 36 min wearing 5 mm 'Long John' neoprene wetsuits. A gastrointestinal temperature radio pill recorded gastro-intestinal temperature (T) prior to, immediately after and at 5, 10, 15, 30, 60, 120 min post-dive.

Diving Into Research of Biomedical Engineering in Scuba Diving.

The physiologic response of the human body to different environments is a complex phenomenon to ensure survival. Immersion and compressed gas diving, together, trigger a set of responses. Monitoring those responses in real time may increase our understanding of them and help us to develop safety procedures and equipment.

User settings on dive computers: reliability in aiding conservative diving.

Introduction: Divers can make adjustments to diving computers when they may need or want to dive more conservatively (e.g., diving with a persistent (patent) foramen ovale).

Decompression management by 43 models of dive computer: single square-wave exposures to between 15 and 50 metres' depth.

Introduction: Dive computers are used in some occupational diving sectors to manage decompression but there is little independent assessment of their performance. A significant proportion of occupational diving operations employ single square-wave pressure exposures in support of their work.

Methods: Single examples of 43 models of dive computer were compressed to five simulated depths between 15 and 50 metres' sea water (msw) and maintained at those depths until they had registered over 30 minutes of decompression.

Heart rate variability during static and dynamic breath-hold dives in elite divers.

The purpose of this study was to assess the differences in cardiac autonomic modulation during maximal static (SA) and dynamic (DA) underwater apneas. Arterial oxygen saturation (SpO(2)), heart rate (HR) and HR variability (SD1 from Poincaré plot and short-term fractal-like scaling exponent, α(1)) were analyzed at the immersed baseline (3 min) and initial, mid- and end-phases (each 30s) of SA and DA in nine elite breath-hold divers. DA and SA lasted 78 ± 8 and 225 ± 20s (mean ± SEM), respectively, and resulted in similar decrements in end-stage SpO(2) (78 ± 3 and 75 ± 3%, p=0.

Solid-state electrolyte sensors for rebreather applications: a preliminary investigation.

Introduction: Recently developed prototypes of zirconium dioxide and NASICON-based micro solid-state electrolyte oxygen (O2) and carbon dioxide (CO2) sensors were tested for their potential suitability in rebreathers. The O2 sensor has a quasi-indefinite lifetime, whilst that of the CO2 sensor is approximately 700 h. This is a preliminary report of a new technological application.

Cardiovascular changes during underwater static and dynamic breath-hold dives in trained divers.

Limited information exists concerning arterial blood pressure (BP) changes in underwater breath-hold diving. Simulated chamber dives to 50 m of freshwater (mfw) reported very high levels of invasive BP in two divers during static apnea (SA), whereas a recent study using a noninvasive subaquatic sphygmomanometer reported unchanged or mildly increased values at 10 m SA dive. In this study we investigated underwater BP changes during not only SA but, for the first time, dynamic apnea (DA) and shortened (SHT) DA in 16 trained breath-hold divers.

Advanced instrumentation for research in diving and hyperbaric medicine.

Improving the safety of diving and increasing knowledge about the adaptation of the human body to underwater and hyperbaric environment require specifically developed underwater instrumentation for physiological measurements. In fact, none of the routine clinical devices for health control is suitable for in-water and/or under-pressure operation. The present paper addresses novel technological acquisitions and the development of three dedicated devices: * an underwater data logger for recording O2 saturation (reflective pulsoxymetry), two-channel ECG, depth and temperature; * an underwater blood pressure meter based on the oscillometric method; and * an underwater echography system.

A novel wearable apnea dive computer for continuous plethysmographic monitoring of oxygen saturation and heart rate.

We describe the development of a novel wrist-mounted apnea dive computer. The device is able to measure and display transcutaneous oxygen saturation, heart rate, plethysmographic pulse waveform, depth, time and temperature during breath-hold dives. All measurements are stored in an external memory chip.

Underwater study of arterial blood pressure in breath-hold divers.

Knowledge regarding arterial blood pressure (ABP) values during breath-hold diving is scanty. It derives from a few reports of measurements performed at the water's surface, showing slight or no increase in ABP, and from a single study of two simulated deep breath-hold dives in a hyperbaric chamber. Simulated dives showed an increase in ABP to values considered life threatening by standard clinical criteria.

Oxygen sensor signal validation for the safety of the rebreather diver.

In electronically controlled, closed-circuit rebreather diving systems, the partial pressure of oxygen inside the breathing loop is controlled with three oxygen sensors, a microcontroller and a solenoid valve - critical components that may fail. State-of-the-art detection of sensor failure, based on a voting algorithm, may fail under circumstances where two or more sensors show the same but incorrect values. The present paper details a novel rebreather controller that offers true sensor-signal validation, thus allowing efficient and reliable detection of sensor failure.

An underwater blood pressure measuring device.

Measurement of arterial blood pressure is an important vital sign for monitoring the circulation. However, up to now no instrument has been available that enables the measurement of blood pressure underwater. The present paper details a novel, oscillometric, automatic digital blood pressure (BP) measurement device especially designed for this purpose.

Novel haptic tool and input device for real time bilateral biomanipulation addressing endoscopic surgery.

In this paper a sensorised polymer microgripper is presented which can be used as a suitable end effector on an endoscopic microinstrument for robot-assisted and possibly teleoperated surgery to enable the operator to receive haptic feedback information on the forces generated during the procedure. A novel tweezers- like haptic input device is also described, which gives the operator the ability to remotely feel these forces generated by grasping operations with the microgripper. This feedback is used to control the amount of force applied in manipulation of tissues during the procedure.