The current use of wearable sensors to enhance safety and performance in breath-hold diving: A systematic review

Wearable Technology for Monitoring Electrocardiograms (ECGs) in Adults: A Scoping Review

In the rapidly evolving landscape of continuous electrocardiogram (ECG) monitoring systems, there is a heightened demand for non-invasive sensors capable of measuring ECGs and detecting heart rate variability (HRV) in diverse populations, ranging from cardiovascular patients to sports enthusiasts. Challenges like device accuracy, patient privacy, signal noise, and long-term safety impede the use of wearable devices in clinical practice. This scoping review aims to assess the performance and safety of novel multi-channel, sensor-based biopotential wearable devices in adults. A comprehensive search strategy was employed on four databases, resulting in 143 records and the inclusion of 12 relevant studies. Most studies focused on healthy adult subjects (n = 6), with some examining controlled groups with atrial fibrillation (AF) (n = 3), long QT syndrome (n = 1), and sleep apnea (n = 1). The investigated bio-sensor devices included chest-worn belts (n = 2), wrist bands (n = 2), adhesive chest strips (n = 2), and wearable textile smart clothes (n = 4). The primary objective of the included studies was to evaluate device performance in terms of accuracy, signal quality, comparability, and visual assessment of ECGs. Safety findings, reported in five articles, indicated no major side effects for long-term/continuous monitoring, with only minor instances of skin irritation. Looking forward, there are ample opportunities to enhance and test these technologies across various physical activity intensities and clinical conditions.

Comparison between Arterial Blood Gases and Oxygen Reserve Index™ in a SCUBA Diver: A Case Report

Hypoxia and hyperoxia are both worrisome issues potentially affecting SCUBA divers, but validated methods to monitor these two conditions underwater are still lacking. In this experiment, a volunteer SCUBA diver was equipped with a pulse oximeter to detect peripheral oxygen saturation (SpO₂) and a device to monitor the oxygen reserve index (ORi™). ORi™ values were compared with arterial blood oxygen saturation (SaO₂) and the partial pressure of oxygen (PaO₂) obtained from the cannulated right radial artery at three steps: at rest out of water; at -15 m underwater after pedaling on a submerged bike; after resurfacing. SpO₂ and ORi™ mirrored the changes in SaO₂ and PaO₂, confirming the expected hyperoxia at depth. To confirm the potential usefulness of an integrated SpO₂ and ORi™ device, further studies are needed on a broader sample with different underwater conditions and diving techniques.

Wearable and Portable Devices for Acquisition of Cardiac Signals while Practicing Sport: A Scoping Review

Wearable and portable devices capable of acquiring cardiac signals are at the frontier of the sport industry. They are becoming increasingly popular for monitoring physiological parameters while practicing sport, given the advances in miniaturized technologies, powerful data, and signal processing applications. Data and signals acquired by these devices are increasingly used to monitor athletes' performances and thus to define risk indices for sport-related cardiac diseases, such as sudden cardiac death. This scoping review investigated commercial wearable and portable devices employed for cardiac signal monitoring during sport activity. A systematic search of the literature was conducted on PubMed, Scopus, and Web of Science. After study selection, a total of 35 studies were included in the review. The studies were categorized based on the application of wearable or portable devices in (1) validation studies, (2) clinical studies, and (3) development studies. The analysis revealed that standardized protocols for validating these technologies are necessary. Indeed, results obtained from the validation studies turned out to be heterogeneous and scarcely comparable, since the metrological characteristics reported were different. Moreover, the validation of several devices was carried out during different sport activities. Finally, results from clinical studies highlighted that wearable devices are crucial to improve athletes' performance and to prevent adverse cardiovascular events.

Wearable Devices in Diving: Scoping Review

Background

Wearables and their benefits for the safety and well-being of users have been widely studied and have had an enormous impact on the general development of these kinds of devices. Yet, the extent of research into the use and impact of wearable devices in the underwater environment is comparatively low. In the past 15 years, there has been an increased interest in research into wearables that are used underwater, as the use of such wearables has steadily grown over time. However, there has so far been no clear indication in the literature about the direction in which efforts for the design and construction of underwater wearable devices are developing. Therefore, the analysis presented in this scoping review establishes a good and powerful basis for the further development and orientation of current underwater wearables within the field.

Objective

In this scoping review, we targeted wearable devices for underwater use to make a comprehensive map of their capabilities and features and discuss the general direction of the development of underwater wearables and the orientation of research into novel prototypes of these kinds of devices.

Methods

In September 2021, we conducted an extensive search for existing literature on 4 databases and for grey literature to identify developed prototypes and early-stage products that were described and tested in water, could be worn and interacted with (eg, displays, buttons, etc), and were fully functional without external equipment. The studies were written in English, came from peer-reviewed academic sources, and were published between 2005 and 2021. We reviewed each title and abstract. The data extraction process was carried out by one author and verified by another author.

Results

In total, 36 relevant studies were included. Among these, 4 different categories were identified; 18 studies dealt primarily with safety devices, 9 dealt with underwater communication devices, 7 dealt with head-up displays, and 2 dealt with underwater human-computer interaction approaches. Although the safety devices seemed to have gained the most interest at the time of this study, a clear trend toward underwater communication wearables was identified.

Conclusions

This review sought to provide a first insight into the possibilities and challenges of the technologies that have been used in and for wearable devices that are meant for use in the underwater environment. Among these, underwater communication technologies have had the most significant influence on future developments. Moreover, a topic that has not received enough attention but should be further addressed is human-computer interaction. By developing underwater wearables that cover 2 or more of the technology categories that we identified, the extent of the benefits of such devices can be significantly increased in the future.

Breath Tools: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

Running is among the most popular sporting hobbies and often chosen specifically for intrinsic psychological benefits. However, up to 40% of runners may experience exercise-induced dyspnoea as a result of cascading physiological phenomena, possibly causing negative psychological states or barriers to participation. Breathing techniques such as slow, deep breathing have proven benefits at rest, but it is unclear if they can be used during exercise to address respiratory limitations or improve performance. While direct experimental evidence is limited, diverse findings from exercise physiology and sports science combined with anecdotal knowledge from Yoga, meditation, and breathwork suggest that many aspects of breathing could be improved via purposeful strategies. Hence, we sought to synthesize these disparate sources to create a new theoretical framework called “Breath Tools” proposing breathing strategies for use during running to improve tolerance, performance, and lower barriers to long-term enjoyment.

Effects of Water Immersion on the Internal Power of Cycling

PURPOSE

Water immersion adds additional drag and metabolic demand for limb movement with respect to air, but its effect on the internal metabolic power (Ėint) of cycling is unknown. We aimed at quantifying the increase in Ėint during underwater cycling with respect to dry conditions at different pedaling rates.

METHODS

12 healthy subjects (4 females) pedaled on a waterproof cycle ergometer in an experimental pool that was either empty (DRY) or filled with tap water at 30.8 ± 0.6 °C (WET). Four different pedal cadences (fp) were studied (40, 50, 60 and 70 rpm) at 25, 50, 75 and 100 W. The metabolic power at steady state was measured via open circuit respirometry and Ėint was calculated as the metabolic power extrapolated for 0 W.

RESULTS

Ėint was significantly higher in WET than in DRY at 50, 60 and 70 rpm (81 ± 31 vs 32 ± 30 W, 167 ± 35 vs 50 ± 29 W, 311 ± 51 vs 81 ± 30 W, respectively, all p < 0.0001), but not at 40 rpm (16 ± 5 vs 11 ± 17 W, p > 0.99). Ėint increased with the third power of fp both in WET and DRY (R2 = 0.49 and 0.91, respectively).

CONCLUSION

Water drag increased Ėint, although limbs unloading via the Archimedes' principle and limbs shape could be potential confounding factors. A simple formula was developed to predict the increase in mechanical power in dry conditions needed to match the rate of energy expenditure during underwater cycling: 44 fp3 - 7 W, where fp is expressed in hertz.

Baroreflex responses during dry resting and exercise apnoeas in air and pure oxygen

Purpose

We analysed the characteristics of arterial baroreflexes during the first phase of apnoea (φ1).

Methods

12 divers performed rest and exercise (30 W) apnoeas (air and oxygen). We measured beat-by-beat R-to-R interval (RRi) and mean arterial pressure (MAP). Mean RRi and MAP values defined the operating point (OP) before (PRE-ss) and in the second phase (φ2) of apnoea. Baroreflex sensitivity (BRS, ms·mmHg⁻¹) was calculated with the sequence method.

Results

In PRE-ss, BRS was (median [IQR]): at rest, 20.3 [10.0–28.6] in air and 18.8 [13.8–25.2] in O₂; at exercise 9.2[8.4–13.2] in air and 10.1[8.4–13.6] in O₂. In φ1, during MAP decrease, BRS was lower than in PRE-ss at rest (6.6 [5.3–11.4] in air and 7.7 [4.9–14.3] in O₂, p < 0.05). At exercise, BRS in φ1 was 6.4 [3.9–13.1] in air and 6.7 [4.1–9.5] in O₂. After attainment of minimum MAP (MAPmin), baroreflex resetting started. After attainment of minimum RRi, baroreflex sequences reappeared. In φ2, BRS at rest was 12.1 [9.6–16.2] in air, 12.9 [9.2–15.8] in O₂. At exercise (no φ2 in air), it was 7.9 [5.4–10.7] in O₂. In φ2, OP acts at higher MAP values.

Conclusion

In apnoea φ1, there is a sudden correction of MAP fall via baroreflex. The lower BRS in the earliest φ1 suggests a possible parasympathetic mechanism underpinning this reduction. After MAPmin, baroreflex resets, displacing its OP at higher MAP level; thus, resetting may not be due to central command. After resetting, restoration of BRS suggests re-establishment of vagal drive.

Breath holding as an example of extreme hypoventilation: experimental testing of a new model describing alveolar gas pathways

NEW FINDINGS

What is the central question of this study? We modelled the alveolar pathway during breath holding on the hypothesis that it follows a hypoventilation loop on the O₂ -CO₂ diagram. What is the main finding and its importance? Validation of the model was possible within the range of alveolar gas compositions compatible with consciousness. Within this range, the experimental data were compatible with the proposed model. The model and its characteristics might allow predictions of alveolar gas composition whenever the alveolar ventilation goes to zero; for example, static and dynamic breath holding at the surface or during ventilation/intubation failure in anaesthesia.

ABSTRACT

According to the hypothesis that alveolar partial pressures of O₂ and CO₂ during breath holding (BH) should vary following a hypoventilation loop, we modelled the alveolar gas pathways during BH on the O₂ -CO₂ diagram and tested it experimentally during ambient air and pure oxygen breathing. In air, the model was constructed using the inspired and alveolar partial pressures of O₂ ( P I O 2 and P A O 2 , respectively) and CO₂ ( P IC O 2 and P AC O 2 , respectively) and the steady-state values of the pre-BH respiratory exchange ratio (RER). In pure oxygen, the model respected the constraint of P AC O 2 = - P A O 2 + P I O 2 . To test this, 12 subjects performed several BHs of increasing duration and one maximal BH at rest and during exercise (30 W cycling supine), while breathing air or pure oxygen. We measured gas flows, P A O 2 and P AC O 2 before and at the end of all BHs. Measured data were fitted through the model. In air, P I O 2  = 150 ± 1 mmHg and P IC O 2  = 0.3 ± 0.0 mmHg, both at rest and at 30 W. Before BH, steady-state RER was 0.83 ± 0.16 at rest and 0.77 ± 0.14 at 30 W; P A O 2  = 107 ± 7 mmHg at rest and 102 ± 8 mmHg at 30 W; and P AC O 2  = 36 ± 4 mmHg at rest and 38 ± 3 mmHg at 30 W. By model fitting, we computed the RER during the early phase of BH: 0.10 [95% confidence interval (95% CI) = 0.08-0.12] at rest and 0.13 (95% CI = 0.11-0.15) at 30 W. In oxygen, model fitting provided P I O 2 : 692 (95% CI = 688-696) mmHg at rest and 693 (95% CI = 689-698) mmHg at 30 W. The experimental data are compatible with the proposed model, within its physiological range.

Adaptative mechanism of the equilibrative nucleoside transporter 1 (ENT-1) and blood adenosine levels in elite freedivers

PURPOSE

Long static or intense dynamic apnoea-like high-altitude exposure is inducing hypoxia. Adenosine is known to participate to the adaptive response to hypoxia leading to the control of heart rate, blood pressure and vasodilation. Extracellular adenosine level is controlled through the equilibrative nucleoside transporter 1 (ENT-1) and the enzyme adenosine deaminase (ADA). The aim of this study was to determine the control of adenosine blood level (ABL) via ENT-1 and ADA during apnoea-induced hypoxia in elite freedivers was similar to high-altitude adaptation.

METHODS

Ten freediver champions and ten controls were studied. Biological (e.g. ENT-1, ADA, ABL, PaO₂, PaCO₂ and pH) and cardiovascular (e.g. heart rate, arterial pressure) parameters were measured at rest and after a submaximal dry static apnoea.

RESULTS

In freedivers, ABL was higher than in control participants in basal condition and increased more in response to apnoea. Also, freedivers showed an ADA increased in response to apnoea. Finally, ENT-1 level and function were reduced for the free divers.

CONCLUSION

Our results suggest in freedivers the presence of an adaptive mechanism similar to the one observed in human exposed to chronic hypoxia induced by high-altitude environment.