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.

Divers who wish to prolong their time underwater while carrying less equipment often use devices called rebreathers, which recycle the gas expired after each breath instead of discarding it as bubbles. However, rebreathers’ need to replace oxygen used by breathing creates a failure mechanism that can and frequently does lead to hypoxia, loss of consciousness, and death. The purpose of this study was to determine whether a pulse oximeter could provide a useful amount of warning time to a diver with a rebreather after failure of the oxygen addition mechanism. Twenty-eight volunteer human subjects breathed on a mixed-gas rebreather in which the oxygen addition system had been disabled. The subjects were immersed in water in four separate environmental scenarios, including cold and warm water, and monitored using pulse oximeters placed at multiple locations. Pulse oximeters placed on the forehead and clipped on the nasal ala provided a mean of 32 s (±10 s SD) of warning time to divers with falling oxygen levels, prior to risk of loss of consciousness. These devices, if configured for underwater use, could provide a practical and inexpensive alarm system to warn of impending loss of consciousness in a manner that is redundant to the rebreather.

Hypoxia is one of the main problems an underwater diver may have to face. The probability of experiencing hypoxia is related to the type of dive and the equipment used. Hypoxia in diving is a potentially fatal event for the diver, as it can lead to the loss of brain functions and consequently to the loss of breathing control, all in the absence of specific premonitory symptoms. It is a risk that may be encountered more frequently by divers who use a closed-circuit rebreather (CCR). For those who use this type of equipment, hypoxia is usually the most frequent cause of death [1]. Our study was aimed at the detection of peripheral oxygen saturation in order to identify, in the future, a preclinical hypoxic condition. We combined the use of pulse oximetry with two forehead sensors on an underwater diver subject who was using an electronic closed-circuit rebreather (ECCR). Despite the known limits of this method and the preliminary status of these findings [2], the recorded data show a clear validity in the use of pulse oximetry in immersion for the detection of peripheral oxygen saturation. In the future, the pulse oximeter could become part of the instrumentation of the diver who uses CCR gear. The device could easily be implemented in these rebreathers. The possibility of being able to perform a basic instrumental analysis means that the diver can become more quickly aware of imminent hypoxia, characterized by the absence of clearly identifiable warning symptoms, and can put in place all the correct procedures for an emergency ascent, avoiding serious consequences.

Lipedema is a chronic and progressive connective tissue disorder characterized by symmetric accumulation of adipose tissue, predominantly in the lower limbs, often associated with pain, easy bruising, and reduced response to lifestyle interventions. Despite increasing recognition, the condition remains frequently misdiagnosed or mistaken for obesity or lymphedema. To investigate the role of lymphoscintigraphy in the diagnostic and therapeutic management of patients with clinically confirmed lipedema and assess its potential utility in detecting associated lymphostatic disorders. A retrospective observational study was conducted on 108 patients clinically diagnosed with lipedema between January 2019 and August 2023. Among them, 31 patients underwent lymphoscintigraphy due to suspected mixed pathology or surgical candidacy. Data on lymphatic involvement were collected and analyzed to determine correlations with clinical staging. In 58% of the selected cases, lymphoscintigraphy revealed no detectable lymphatic abnormalities. Of these, approximately 70% showed latent compensatory lymphatic patterns. The remaining 39% had confirmed alterations of the superficial and/or deep lymphatic system, suggesting a mixed clinical picture (lipo-lymphedema) with potential surgical contraindications. Lymphoscintigraphy is not essential for routine diagnosis of lipedema, which remains clinical. However, it is valuable in identifying cases with coexisting lymphostatic components and guiding surgical decisions. These findings support a multidisciplinary and individualized approach to diagnosis and treatment.

Background/Objectives: Heart rate variability (HRV) analysis is a valuable noninvasive tool to evaluate autonomic nervous system activity, especially under environmental stress. Diving, which combines immersion, hyperbaric exposure, and altered respiratory gas dynamics, presents a unique physiological challenge. This single-subject case study aimed to assess autonomic modulation during and after a closed-circuit rebreather (CCR) dive using comprehensive HRV analysis. Methods: A healthy male diver underwent continuous RR interval monitoring before, during, and after a CCR dive using the MCM100 military device. HRV parameters were evaluated across time-domain, frequency-domain, and nonlinear domains. Data processing was performed using the Kubios software, and statistical comparison between phases were carried out using paired-sample tests in SPSS. Results: During the dive, HRV indices showed a significant decrease in RMSSD (p < 0.01), SDNN (p < 0.05), and SD1 (p < 0.01) compared to the baseline, indicating marked parasympathetic withdrawal. A concurrent increase in the LF/HF ratio (p < 0.05) suggested sympathetic predominance. In the post-dive phase, parasympathetic indices such as RMSSD and SD1 improved relative to the dive phase (p < 0.05) but remained below baseline. Nonlinear measures, including SD2/SD1 ratio and sample entropy, also varied significantly across phases. Conclusions: This case study demonstrates significant autonomic shift associated with a CCR dive, characterized by acute parasympathetic withdrawal and a partial recovery post-dive. HRV profiling may offer a sensitive, noninvasive approach for monitoring stress and recovery dynamics in professional divers.