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The South Pacific Underwater Medicine Society (SPUMS) diving medical for recreational scuba divers was last reviewed in 2011. From 2011 to 2019, considerable advancements have occurred in cardiovascular risk assessment relevant to divers. The SPUMS 48th (2019) Annual Scientific Meeting theme was cardiovascular risk assessment in diving. The meeting had multiple presentations updating scientific information about assessing cardiovascular risk. These were distilled into a new set of guidelines at the final conference workshop. SPUMS guidelines for medical risk assessment in recreational diving have subsequently been updated and modified including a new Appendix C: Suggested evaluation of the cardiovascular system for divers. The revised evaluation of the cardiovascular system for divers covers the following topics: 1. Background information on the relevance of cardiovascular risk and diving; 2. Defining which divers with cardiovascular problems should not dive, or whom require treatment interventions before further review; 3. Recommended screening procedures (flowchart) for divers aged 45 and over; 4. Assessment of divers with known or symptomatic cardiovascular disease, including guidance on assessing divers with specific diagnoses such as hypertension, atrial fibrillation, cardiac pacemaker, immersion pulmonary oedema, takotsubo cardiomyopathy, hypertrophic cardiomyopathy and persistent (patent) foramen ovale; 5. Additional cardiovascular health questions included in the SPUMS guidelines for medical risk assessment in recreational diving; 6. Updated general cardiovascular medical risk assessment advice; 7. Referencing of relevant literature. The essential elements of this guideline are presented in this paper. [ABSTRACT FROM AUTHOR]

Introduction: While otic barotrauma (OBT) is a common condition experienced by divers, data related to military divers is limited. This study aimed to determine the incidence of OBT in Canadian armed forces (CAF) shallow-water diver (SWD) students trained through the Fleet Dive Unit (Atlantic) (FDU[A]) between 2011-2015. Methods: A retrospective cohort evaluation was performed. The study group consisted of all SWD candidates who embarked on an SWD course through FDU(A) between 2011-2015. A total of 241 subjects comprised the final data analysis. Results: A total of 56 individuals (23.2%) suffered 60 instances of OBT, yielding an incidence density rate of 8.68 per 1,000 person-days on course. A total of 73 diving days (10.44 per 1,000 planned person-course days, or 4.87 diving days per course) were lost due to OBT. Of the reported OBT cases, 18% resulted in cessation of training, 72% in temporary removal from diving. There was no statistically significant association between sex, history of environmental allergies, previous dive qualification, age or rank and the development of OBT. Conclusion: This study reveals that OBT is prevalent among CAF SWD candidates, with operational impact due to missed diving days. This study is limited, and further prospective study is recommended. [ABSTRACT FROM AUTHOR]

Background: The risk factors of pulmonary edema induced by diving in healthy subjects are not well known. The aim of the present study was to assess the parameters contributing to the increase in extravascular lung water after diving. Methods: This study was carried out in a professional diving institute. All divers participating in the teaching program from June 2012 to June 2014 were included in the study. Extravascular lung water was assessed using the detection of ultrasound lung comets (ULC) by chest ultrasonography. Clinical parameters and dive profiles were recorded using a questionnaire and a dive computer. Results: One-hundred six divers were investigated after 263 dives. They used an open-circuit umbilical supplying compressed gas diving apparatus in 202 cases and a self-contained underwater breathing apparatus in 61 cases. A generalized linear mixed model analysis was performed which demonstrated that the dive induced a significant increase in ULC score (incidence rate ratio: 3.16). It also identified that the predictive variable of increased extravascular lung water after the dive was the exercise intensity at depth ( z = 3.99, p < 0.0001). The other parameters studied such as the water temperature, dive profile, hyperoxic exposure, or anthropometric data were not associated with the increase in extravascular lung water after the dive. Conclusions: In this study, the exercise intensity was the main contributor to the increase in extravascular lung water in healthy divers. To improve the prevention of immersion pulmonary edema, the exercise intensity experienced during the dive should thus be adapted to the aerobic fitness level of the divers. [ABSTRACT FROM AUTHOR]

We discuss the case of an experienced diver who ran out of air during his final ascent while scuba diving. He lost consciousness rapidly after surfacing and despite immediate cardiopulmonary resuscitation, could not be revived. On arrival at the emergency department he was noted to have copious amounts of blood in his upper airway and had developed extensive subcutaneous emphysema. Large amounts of air were observed in the central circulation following a postmortem computerized tomography scan as well as pneumomediastinum, a small right-sided hemothorax, and extensive subcutaneous emphysema. We discuss several potential pathophysiological mechanisms that might explain these findings. Finally, we end with a recommendation for an expedient whole-body postmortem computerized tomography scan and autopsy by a suitably qualified pathologist in the investigation of all dive-related fatalities, where possible. [ABSTRACT FROM AUTHOR]

A neoprene wetsuit is widely used to reduce thermal dispersion during diving. Recent observations have pointed out that elastic recoil of the wetsuit might have significant compressive effects, able to affect water and electrolyte homeostasis during both dry and immersed conditions. The aim of this study was to evaluate the possible cardiovascular and respiratory effects of the neoprene wetsuit in dry conditions in a sample of experienced divers. Twenty-four (24) healthy divers were evaluated by Doppler-echocardiography and by spirometry in basal conditions and while wearing a full neoprene wetsuit. During wetsuit conditions, we observed a significant decrease in heart rate (-5%; p<0.05) and cardiac output (-12%; p<0.05), and a significant increase in total peripheral resistances (15%; p<0.05). Moreover, a significant reduction of right ventricular early diastolic filling was observed (-15%; p<0.05). As concerns pulmonary function, a significant reduction of vital capacity (-2%; p<0.001) and expiratory reserve volume (-25%; p<0.001), and a significant increase of inspiratory capacity (9%; p<0.001) and tidal volume (25%; p<0.05) were observed. These data support the hypothesis that neoprene elastic recoil, possibly due to a compression exerted on chest, might affect systemic circulation (decreasing cardiac output and impairing right ventricular filling) and respiratory function. [ABSTRACT FROM AUTHOR]

Hypertension is one of the most common chronic diseases in the world: in the United States, it affects one-third of the adult population. Most cases are primary hypertension -- with no identified cause -- and significantly increase risk for cardiovascular disease and stroke. At NASA's Neutral Buoyancy Laboratory (NBL), there is a cadre of professional divers who provide underwater support during extravehicular activity training (EVAs, commonly referred to as "spacewalks") for astronauts. The NBL occupational health program requires regular "work-site" physical exams, including blood pressure checks, on at least a weekly basis. Although some blood pressures measured during such regular checks were elevated, the diagnosis and management of blood pressure was outside the scope of that occupational medicine program. As a result, there was no protocol to analyze and manage asymptomatic elevated blood pressure if and when it warranted physician follow-up. We therefore analyzed the blood pressure data from all divers in 2015, vetted the worksite physical and developed a referral pathway to ensure divers have access to effective management of their blood pressure while minimizing impact of such a program on daily operations. [ABSTRACT FROM AUTHOR]

Introduction: Exposure to the confined hyperbaric, hyperoxic environment of the saturation chamber poses a number of unique physiological challenges to divers. Appropriately tailored training, nutrition and health programs may help support the body to cope with and overcome these challenges. Aim: To describe the self-reported habits and attitudes of saturation divers toward issues related to health, lifestyle, nutrition and physical activity. Methods: A questionnaire was developed to elicit information related to four key areas: 1) respondent demographics; 2) physical activity habits and attitudes; 3) nutritional attitudes; and 4) general lifestyle and health information. Results: Respondents (n = 89/45%) reported a generally healthy lifestyle, including high physical activity levels while onshore, low tobacco use and alcohol intakes within U.K.-recommended guidelines. Responses to in-chamber items demonstrated reduced physical activity, disrupted sleep and distorted taste and smell perception. In addition, lethargy, headaches and musculoskeletal stiffness/ soreness were reported as frequent symptoms following a period of time spent in saturation. Conclusion: Results of this study provide an insight into the self-reported practices and attitudes of saturation divers and appear to indicate a generally healthy lifestyle in the respondents. Some themes emerged which may impact on diver health and performance while in saturation. The results of this report may help provide a platform to generate hypotheses for further research and facilitate development of appropriately tailored nutrition and training-based strategies for saturation divers. [ABSTRACT FROM AUTHOR]

The purpose of the present field study was to explore diving patterns and heart rate of elderly Korean women divers (haenyeo) while breath-hold diving in cold seawater. We hypothesized that the decreasing rate in heart rate of elderly haenyeos during breath-hold diving was greater and total diving time was shorter than those of young haenyeos from previous studies. Nine haenyeos participated in a field study [68 ± 10 yr in age, ranged from 56 to 83 yr] at a seawater temperature of 10 to 13 °C. Average total diving time including surface swimming time between dives was 253 ± 73 min (155-341 min). Total frequency of dives was 97 ± 28 times and they dived 23 ± 8 times per hour. All haenyeos showed diving bradycardia with a decreased rate of 20 ± 8% at the bottom time (101 ± 20 bpm) when compared to surface swimming time (125 ± 16 bpm) in the sea. Older haenyeos among the nine elderly haenyeos had shorter diving time, less diving frequencies, and lower heart rate at work (p<0.05). These reductions imply that haenyeos voluntarily adjust their workload along with advancing age and diminished cardiovascular functions. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the study was to assess changes in subarachnoid space width (sas-TQ), the marker of intracranial pressure (ICP), pial artery pulsation (cc-TQ) and cardiac contribution to blood pressure (BP), cerebral blood flow velocity (CBFV) and cc-TQ oscillations throughout the maximal breath hold in elite apnoea divers. Non-invasive assessment of sas-TQ and cc-TQ became possible due to recently developed method based on infrared radiation, called near-infrared transillumination/backscattering sounding (NIR-T/BSS). Methods: The experimental group consisted of seven breath-hold divers (six men). During testing, each participant performed a single maximal end-inspiratory breath hold. Apnoea consisted of the easy-going and struggle phases (characterised by involuntary breathing movements (IBMs)). Heart rate (HR) was determined using a standard ECG. BP was assessed using the photoplethysmography method. SaO2 was monitored continuously with pulse oximetry. A pneumatic chest belt was used to register thoracic and abdominal movements. Cerebral blood flow velocity (CBFV) was estimated by a 2-MHz transcranial Doppler ultrasonic probe. sas-TQ and cc-TQ were measured using NIR-T/BSS. Wavelet transform analysis was performed to assess cardiac contribution to BP, CBFV and cc-TQ oscillations. Results: Mean BP and CBFV increased compared to baseline at the end of the easy phase and were further augmented by IBMs. cc-TQ increased compared to baseline at the end of the easy phase and remained stable during the IBMs. HR did not change significantly throughout the apnoea, although a trend toward a decrease during the easy phase and recovery during the IBMs was visible. Amplitudes of BP, CBFV and cc-TQ were augmented. sas-TQ and SaO2 decreased at the easy phase of apnoea and further decreased during the IBMs. Conclusions: Apnoea increases intracranial pressure and pial artery pulsation. Pial artery pulsation seems to be stabilised by the IBMs. Cardiac contribution to BP, CBFV and cc-TQ oscillations does not change throughout the apnoea. [ABSTRACT FROM AUTHOR]

Objectives: Our main aim was to study the long-term neuropsychological effects of non-saturation diving. Further, we aimed to investigate whether neuropsychological performance was predictive of subsequent diving accidents and diving status. Methods: In this prospective longitudinal study, we enrolled 50 male diving students (mean age 25.3 years) at a diving school and followed them up six and 12 years later (43 and 37 divers, respectively). At each wave of the study, divers completed a comprehensive neuropsychological test battery and answered questionnaires on cumulative number of dives, incidents of decompression illness (DCI) and professional diver status. Results: At the 12-year follow-up, the divers reported a median number of 455 (range 40-5,604) cumulative dives. Cumulative number of dives was not associated with any adverse neuropsychological effects. However, divers with an incident of DCI performed worse in a memory test (Benton Visual Retention Test) and reported slightly more neuropsychiatric symptoms (Q 16). Diver students who performed well on a blindfolded memory test (tactual performance test) had an increased likelihood of becoming a professional diver 12 years later. Conclusions: The main findings in the present study support the view that asymptomatic non-saturation divers who have dived under controlled conditions do not have an increased risk of impaired nervous system function, at least not to an extent that can be detected with neuropsychological tests while they still are relatively young. The observed associations between a history of DCI and impaired results in a memory test and reporting of neuropsychiatric symptoms may be due to a nervous system effect caused by DCI. The diver students' ability of problem-solving while they were blindfolded was predictive of their likelihood of becoming a professional diver 12 years later. [ABSTRACT FROM AUTHOR]

Self-contained underwater breathing apparatus ( SCUBA) diving is regularly associated with numerous asymptomatic changes in cardiovascular function. Freshwater SCUBA diving presents unique challenges compared with open sea diving related to differences in water density and the potential for dive locations at altitude. The aim of this study was to evaluate the impact of freshwater trimix diving at altitude on human cardiovascular function. Ten divers performed two dives in consecutive days at 294 m altitude with the surface interval of 24 h. Both dives were at a depth of 45 m with total dive time 29 and 26 min for the first and second dive, respectively. Assessment of venous gas embolization, hydration status, cardiac function and arterial stiffness was performed. Production of venous gas emboli was low, and there were no significant differences between the dives. After the first dive, diastolic blood pressure was significantly reduced, which persisted up to 24 h. Left ventricular stroke volume decreased, and heart rate increased after both dives. Pulse wave velocity was unchanged following the dives. However, the central and peripheral augmentation index became more negative after both dives, indicating reduced wave reflection. Ejection duration and round trip travel time were prolonged 24 h after the first dive, suggesting longer-lasting suppression of cardiac and endothelial function. This study shows that freshwater trimix dives with conservative profiles and low venous gas bubble loads can result in multiple asymptomatic acute cardiovascular changes some of which were present up to 24 h after dive. [ABSTRACT FROM AUTHOR]

Tissue nitrogen (N2) exchange is primarily dependent on circulation, which may be modified by body thermal status. Thermal effects on uptake and washout of N2 have not been systematically investigated earlier. In the present study of eight subjects, N2 was washed out in thermally neutral ambient conditions (TN; skin temperature (Ts) = 33.69 ± 0.84°C), then washed in during either TN, cool (Ts 30.25 ± 4.15°C) or warm (Ts = 35.81 ± 0.82°C) conditions. It was then washed out during various combinations of those conditions. N2 exchange was monitored during 125 minutes of breathing a normoxic oxygen/ argon mixture (Phase I) followed by room air for 125 minutes of N2 reloading (Phase II; no N2 recording) and then 125 minutes N2 washout (Phase III) in order to determine the amount of N2 taken up during Phase II. Cool conditions reduced cardiac output, while warm conditions increased it compared to TN. Among the five Phase I TN recordings in the eight subjects (i.e., 40 control experiments) the N2 yield averaged 857.2 ± 15.3 mL. The reloaded N2 volume in Phase II was significantly smaller during the cool condition (8%, p ≤ 0.05) and significantly larger (22%, p ≤ 0.05) during the warm. The N2 washed out in 125 minutes was significantly less during cold (6%, p ≤ 0.05) and greater during warm conditions (18%, p ≤ 0.05). These observations are consistent with previously reported circulatory changes in cool and warm conditions and effects of thermal status on venous gas bubble dynamics and incidents of decompression sickness. [ABSTRACT FROM AUTHOR]

The article explores the journalistic coverage of the public crisis that developed following the publication of Yediot Aharonot's investigative report about the diving practices of Israel's sea commandos in the polluted Kishon River. The coverage of the Kishon diving crisis is probed via two complementing research trajectories. The first trajectory looks at the construction of the newsworthiness of the Kishon diving crisis in comparison to two similar crises while addressing the interpretations provided by various involved factors. The second trajectory explores the various frames through which the Kishon diving crises were narrated. The article's concluding section discusses the complex interrelations between newsworthiness and framing. [ABSTRACT FROM PUBLISHER]

Highlights: [•] The early phase of pulmonary oxygen toxicity (POT) is considered to be reversible. [•] Oxygen divers are at risk of developing pulmonary oxygen toxicity. [•] To keep divers in the reversible phase of POT monitoring is required. [•] Decreases in vital capacity or diffusing capacity for CO are most used monitor methods. [•] Novel techniques should be tested as potential biomarkers for future monitoring. [ABSTRACT FROM AUTHOR]

The article investigates the alcohol consumption and attitudes to drinking alcohol among recreational divers in Great Britain. Results revealed the likelihood of older divers to exceed the recommended weekly alcohol units as compared to younger divers, as well as the association of binge drinking to younger divers. A number of respondents admitted diving when considering themselves unfit to drive a car, while others reported witnessing a diving incident attributed to alcohol.

The article presents a study that examined the effect of conservative decompression practices in managing decompression sickness (DCS) among divers with and without vascular right-to-left shunt (r/l shunt). Patent foramen ovale (PFO) causes r/l shunt and is a risk factor for DCS. It discusses the risk management of PFO and previous PFO-DCS studies. The results indicated that conservative dive profile reduce the risk of recurrent DCS independent of the presence of r/l shunt in divers.

The article presents a study on risk factors associated with rapid ascent and buoyancy control among recreational divers. Dive and diver information were reportedly obtained and depth/time loggers attached to recreational divers. The article states that a loss of buoyancy control was the main risk factor for making a rapid ascent and that research is needed to determine if the latter is due to buoyancy control loss, lack of ascent rate reference or failure to appreciate potential consequences.

The article reports on a postal survey of fitness-to-dive opinions of diving doctors (DD) and general practitioners (GP) to determine consensus with published standards. A survey on fitness to dive of 20 "real-life" applicants with potentially relevant medical conditions was reportedly undertaken. The article states that concordance between DDs and GPs was generally high, but was low between these groups and published recommendations when there is a relevant medical condition.

The article presents a study correlating Diver Health Survey (DHS) score with probability of decompression sickness (pDCS) among occupational dive guides and instructors. Divers' dive profiles were recorded and the pDCS for each dive calculated using the LE1 probabilistic model. The results showed that there was no significant association between DHS score and pDCS, and that using DHS for monitoring occupational divers' daily decompression stress remains unproven.

The diving response is the sequence of cardiovascular, respiratory and metabolic adjustments produced by apnoea and further strengthened by cooling of the facial area and/or hypoxia. This study aimed at comparing the cardiovascular response to diving of trained divers with that of a control group. In this order, 14 trained divers were compared with 14 non-divers. By means of impedance cardiography and continuous monitoring of arterial pressure, hemodynamic data were collected during three different experimental sessions. Each session included a cycle-ergometer exercise against a workload of 0.5 W kg of body mass, pedalling in a steady-state condition. During exercise, each subject randomly accomplished 40 s of breath-hold exercise with face immersion (test A) or in air (test B). A control exercise test with normal breathing (test C) was also performed. Divers showed a faster onset of bradycardic response (ANOVA, P < 0.01) and a faster adjustment in systemic vascular resistance ( P < 0.001 for divers vs. controls) than did non-divers. Moreover, cardiac output decreased only in divers during the first phase of test A ( P < 0.01 for divers vs. controls). The most striking findings were that divers showed a more rapid cardiovascular adjustment with respect to controls, in particular in heart rate and systemic vascular resistance; moreover, with continued apnoea, a delayed increase in myocardial performance and stroke volume occurred and obscured the cardiovascular effects of the diving response. [ABSTRACT FROM AUTHOR]

Abstract: Deep diving is defined as diving to depths more than 50m of seawater (msw), and is mainly used for occupational and military purposes. A deep dive is characterized by the compression phase, the bottom time and the decompression phase. Neurological and neurophysiologic effects are demonstrated in divers during the compression phase and the bottom time. Immediate and transient neurological effects after deep dives have been shown in some divers. However, the results from the epidemiological studies regarding long term neurological effects from deep diving are conflicting and still not conclusive. Prospective clinical studies with sufficient power and sensitivity are needed to solve this very important issue. [Copyright &y& Elsevier]

The article presents a research about the possible effects of Trimix Self-Contained Underwater Breathing Apparatus (SCUBA) diving to cardiopulmonary function of divers. Participants include seven divers where they used Trimix, consisting of oxygen, helium, and nitrogen mixtures on their six dives. In addition, these divers have plunged the seawater's depth from 55 to 80 meters. These participants underwent assessment for their blood levels of their N-terminal part of pro-brain natriuretic peptide (NT-proBNP) before and after they dived. The results include extravascular lung water (EVLW) accumulation, pulmonary arterial pressure (PAP) increase, and cardiopulmonary strain. Moreover, researchers concluded that these divers are more likely to acquire pulmonary edema.

The article presents the results of a study on the factors affecting the performance of divers in competitive apnea diving. According to the author, the key factors include work economy, local tissue energy and oxygen stores, and the anaerobic capacity of the muscles. She explains that the high level of lactate after dynamic competition dives suggests a high anaerobic component and muscle hypoxia could affect muscle work and swimming distance. She also describes safety measures during pool competitions.

The article presents the results of a study on the effect of varying the concentrations of exhaled nitric oxide on military divers using three different types of dive. According to the authors, all values of exhaled nitric oxide concentrations, a biological marker, fell within the normal range in closed circuit rebreather dive, semi-closed circuit rebreather dive, and compressed air dive. They explain that a difference of more than four parts per billion (ppb) is considered to be of biological significance.

The article discusses a study that analyzes the relationship of right-to-left shunts (RLSs) and neurological decompression sickness (DCS) among professional divers. A comparison of RLS prevalence in five case-control studies was conducted among 654 divers with neurological DCS history and those who do not have DCS. The study revealed that neurological DCS gained low incidence based on meta-analysis, which indicates that the risk of neurological DCS caused by RLS is potentially small. It also notes that results of the study showed the need for transcranial Doppler in RLS screening and quantification.

This study was to elucidate the physiological effects of dynamic apneas, as performed as a discipline in breath-hold diving for recreational or competitive purposes. Therefore, cardiovascular and respiratory effects of apneas with simultaneously initiated exercise were investigated in ten trained breath-hold divers. They performed maximum duration apneas with face immersion (26 degrees C) under rest and exercise (40 W, 80 W and 120 W) on a cycle ergometer in the laboratory. Apneic time, heart rate (HR), mean arterial pressure (MAP), arterial oxygen saturation and O2 (.VO2) and CO2 exchange were measured. All end-apnea heart rates were lower than corresponding control values. Higher workloads increased the initial rise in HR and delayed the onset of bradycardia. After an initial drop, MAP rose to 150% of control towards the end of apnea. Apneic .VO2 was reduced by 25% during exercise and by 40% during resting apneas compared to eupneic control values. It was concluded that magnitude and time course of diving bradycardia depend on work intensity. Higher workloads delay the onset and attenuate HR reduction, presumably due to increased sympathetic activity. It was also found that apnea with simultaneously initiated exercise has an O2 conserving effect compared to eupneic exercise. Although aimed to be a realistic approach to breath-hold diving, the study has certain methodological limitations in terms of body-immersion (hydrostatic pressure effects) and body-cooling effects due to conduction of the experiments in a laboratory set-up. [ABSTRACT FROM AUTHOR]

Breath-holding induces cardiovascular responses, notably bradycardia and peripheral vasoconstriction, which are known collectively as the diving response. This response is oxygen-conserving, i.e. an augmented response attenuates arterial oxygen desaturation, and is enhanced by apnoea training. To test this hypothesis, we compared heart rate (HR) and arterial oxygen saturation (SaO2) in breath-hold divers (BHD) and non-divers (ND). Nine BHD and nine healthy ND performed two static apnoeas (for 30 s and 45 s) and two dynamic apnoeas (for 30 s and 45 s) while swimming underwater at 0.7 m·s-1. The pool temperature was 26°C. The apnoeas were performed at 60% of forced vital capacity. Heart rate (HR) and SaO2 were recorded before breath-holding and at its end and are expressed in % change from rest values (ΔHR and ΔSaO2). Comparisons between BHD and ND showed that ΔSaO2 were lower in divers after both static apnoeas for 30 s and 45 s(-2.8% vs. -5.5%; -3.2% vs. 6.3%; p < 0.05, respectively) and dynamic apnoeas (-6% vs. -10.1%: -7.2% vs. - 12.3%; p < 0.05, respectively). The change in HR did not differ between the two groups and negative linear relations were found between ΔHR and ΔSaO2 in both divers and ND (r=0.66 and 0.61, respectively; p < 0.001). Moreover, the slope was lower for the divers (- 0.785 vs. - 0.1429; p < 0.001). Our results suggest that apnoea training explained the greater oxygen conservation seen in the divers in both static and dynamic conditions. [ABSTRACT FROM AUTHOR]

The article presents the results of a study on the effectiveness of drinking system for divers (DSFD). According to the authors, the DSFD allows the diver to drink while in the water using a suction pipe embedded in the microphone unit in the oronasal mask. They add that divers who tested the drinking system claimed that the system was easy to operate and clothing did not affect their diving. They indicate that DSFD is very effective in maintaining body fluid balance in divers.