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  • 1. Blogg, S. Lesley
    et al.
    Mollerlokken, Andreas
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Observed decompression sickness and venous bubbles following 18-msw dive profiles using RN Table 112017In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 44, no 3, p. 211-219Article in journal (Refereed)
    Abstract [en]

    The venous bubble load in the body after diving may be used to infer risk of decompression sickness (DCS). Retrospective analysis of post-dive bubbling and DCS was made on seven studies. Each of these investigated interventions, using an 18 meters of sea water (msw) air dive profile from Royal Navy Table 11 (Mod Air Table), equivalent to the Norwegian Air tables. A recent neurological DCS case suggested this table was not safe as thought. Two-hundred and twenty (220) man-dives were completed on this profile. Bubble measurements were made following 219 man-dives, using Doppler or 2D ultrasound measurements made on the Kisman-Masurel and Eftedal-Brubakk scales, respectively. The overall median grade was KM/EB 0.5 and the overall median maximum grade was KM/EB 2. Two cases of transient shoulder discomfort ("niggles") were observed (0.9% (95% CL 0.1% 3.3%)) and were treated with surface oxygen. One dive, for which no bubble measurements were made, resulted in a neurological DCS treated with hyperbaric oxygen. The DCS risk of this profile is below that predicted by models, and comparison of the cumulative incidence of DCS of these data to the large dataset compiled by DCIEM [1, 2], show that the incidence is lower than might be expected.

  • 2. Blogg, S.L.
    et al.
    Gennser, Mikael
    Swedish Defence Research Agency.
    Loveman, G.A.M.
    Seddon, F.M.
    Thacker, J.C.
    White, M.G.
    The effect of breathing hyperoxic gas during simulated submarine escape on venous gas emboli and decompression illness2003In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 30, no 3, p. 163-174Article in journal (Refereed)
    Abstract [en]

    Raised internal pressure in a distressed submarine rapidly increases the risk of decompression sickness (DCS) following submarine escape. The hypothesis that breathing a hyperoxic gas during escape may reduce the risk of DCS was tested using goats. Shallow air saturation and simulated submarine escape dives were carried out either singularly or in combination (saturation, escape, or saturation followed by escape) using air or 60% / 40% oxygen (O2) / nitrogen (N2) mixture as breathing gas during the escapes. Post-surfacing, animals were observed for signs of DCI and O2 toxicity. Precordial Doppler ultrasound was used to score venous gas emboli (VGE) using the Kisman Masurel (KM) scale. Following escape from 2.5 MPa, the rate at which VGE disappeared in the hyperoxic group (n = 8) was significantly faster(p < 0.05) than the air group (n = 7). One case of pulmonary barotrauma with arterial gas embolism occurred in the air group, but no cases of DCS were observed. After saturation at 0.18 MPa followed by escape from 2.5 MPa, DCS occurred in four of 15 animals in the air group and in two of 16 animals in the hyperoxic group. The rate of disappearance of VGE was significantly faster (p < 0.01) in the hyperoxic group. O2 toxicity was not discernible in any of the animals.

  • 3.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Ericsson, Mikael
    Larsson, Agneta
    Lindholm, Peter
    Investigation of a demand-controlled rebreather in connection with a diving accident2011In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 38, no 1, p. 61-72Article in journal (Refereed)
    Abstract [en]

    This paper describes the examination of a Halcyon RB80 semi-closed underwater breathing apparatus used in a diving accident in 2007. The apparatus was supplied with trimix (oxygen, nitrogen and helium) containing 31% oxygen. The duration of the dive was 105 minutes at 28 meters' average depth in fresh water, with a 19-minute oxygen decompression stop at 6 meters. Upon surfacing the diver experienced seizures and signs of severe neurological deficits. The apparatus was tested with regard to the oxygen fraction drop from the supply gas to the breathing loop - i.e., the oxygen fraction inhaled by the diver (FiO2) was investigated. The FiO2 was measured and found to be lower than the value stated on the manufacturer's web page at the time of the accident. This investigation suggests that during the dive, the actual FiO2% was 17.9-25.3%, which is considerably lower than the FiO2% used for decompression calculations (30%). The underestimation of FiO2 resulted in too short and/or too few decompression stops during ascent. The low FiO2 would also put a diver at risk of hypoxia at shallow depths. It is concluded that inadequate information on the performance of the rebreather was a major contributing factor to this accident.

  • 4.
    Frånberg, Oskar
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Measurement and modeling of oxygen content in a demand mass ratio injection rebreather2015In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 42, no 6, p. 573-592Article in journal (Refereed)
    Abstract [en]

    Mechanical semi-closed rebreathers do not need oxygen sensors for their functions, thereby reducing the complexity of the system. However, testing and modeling are necessary in order to determine operational limits as well as the decompression obligation and to avoid hyperoxia and hypoxia. Two models for predicting the oxygen fraction in a demand constant mass ratio injection (DCMRI) rebreather for underwater use were compiled and compared. The model validity was tested with an IS-MIX, Interspiro AB rebreather using a metabolic simulator connected to a breathing machine inside a water-filled pressure chamber. The testing schedule ranged from 0.5-liter (L) to 3-liter tidal volumes, breathing frequencies from five to 25 breaths/minute and oxygen consumptions from 0.5 L/minute to 4 L/minute. Tests were carried out at surface and pressure profiles ranging to 920 kPa(a) (81 meters of sea water, 266 feet of sea water). The root mean squared error (RMSE) of the single-compartment model was 2.4 percent-units of oxygen for the surface test with the 30% dosage setting but was otherwise below 1% unit. For the multicompartment model the RMSE was below 1% unit of oxygen for all tests. It is believed that these models will aid divers in operational settings and may constitute a helpful tool when developing semi-closed rebreathing apparatuses.

  • 5.
    Gennser, Mikael
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Loveman, Geoff
    Seddon, Fiona
    Thacker, Julian
    Blogg, S. Lesley
    Oxygen and carbogen breathing following simulated submarine escape2014In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 41, no 5, p. 387-392Article in journal (Refereed)
    Abstract [en]

    Escape from a disabled submarine exposes escapers to a high risk of decompression sickness (DCS). The initial bubble load is thought to emanate from the fast tissues; it is this load that should be lowered to reduce risk of serious neurological DCS. The breathing of oxygen or carbogen (5% CO2, 95% O-2) post-surfacing was investigated with regard to its ability to reduce the initial bubble load in comparison to air breathing. Thirty-two goats were subject to a dry simulated submarine escape profile to and from 240 meters (2.5 MPa). On surfacing, they breathed air (control), oxygen or carbogen for 30 minutes. Regular Doppler audio bubble grading was carried out, using the Kisman Masurel (KM) scale. One suspected case of DCS was noted. No oxygen toxicity or arterial gas embolism occurred. No significant difference was found between the groups in terms of the median peak KM grade or the period before the KM grade dropped below III. Time to disappearance of bubbles was significantly different between groups; oxygen showed faster bubble resolution than carbogen and air. This reduction in time to bubble resolution may be beneficial in reducing decompression stress, but probably does not affect the risk of fast-tissue DCS.

  • 6. Larsson, Agneta
    et al.
    Uusijärvi, Johan
    Frånberg, Oskar
    KTH, School of Technology and Health (STH), Environmental Physiology.
    Eksborg, Staffan
    Lindholm, Peter
    Nitrox permits direct exit for attendants during extended hyperbaric oxygen treatment2012In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 39, no 1, p. 605-612Article in journal (Refereed)
    Abstract [en]

    Background: Intermittent breathing of oxygen-enriched air, nitrox (1:1 air:oxygen, 60.5%O-2), for attendants in multiplace hyperbaric chambers should enable treatment protocols (HOPAN hyperbaric oxygen protocol attendants' nitrox) of up to 200 minutes at 2.8 atmospheres absolute (ATA), while retaining the option of a direct decompression and exit.Methods: HOPAN with cycles of 15 minutes of nitrox breathing followed by 10 minutes of chamber air for attendants were occasionally used from 2007-2009. HOPAN vs. LTP (local treatment protocols) were evaluated via an anonymous enquiry among attendants; patients' medical records were followed six months post-HBO2 treatment (HBO2T).Results: 88 HOPANs, with 59 chamber attendants assisting 30 patients, were documented. HOPAN duration ranged from 55-167 minutes (median 140 minutes). 31/59 attendants answered the enquiry. Perceived comfort of each protocol (HOPAN vs. LTP) by attendants was reported as equal. Symptoms, both minor (parestesias) and severe (joint pain), were reported in connection with LTP, while only one occurrence (mild joint pain) was reported in connection with HOPAN. No complications were documented among the attendants or the patients. It is suggested that nitrox breathing for chamber attendants provide flexible HBO2T for patients at 2.8 ATA for up to 200 minutes within no-decompression limits, facilitating future studies of HBO2T dosage.

  • 7. Lindholm, P.
    et al.
    Nordh, J.
    Gennser, Mikael
    Swedish Defence Research Agency.
    The heart rate of breath-hold divers during static apnea: effects of competitive stress2006In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 33, no 2, p. 119-124Article in journal (Refereed)
    Abstract [en]

    Breath-hold divers compete with regard to depth, time and/or distance. The present observations were carried out on athletes performing static apnea where they perform one breath-hold for as long a duration as possible with the body and face immersed in water. Heart rate was measured on eight competitors participating in the Swedish Championship in static apnea 2001, both during the competition and during a separate training session using the Polar NV system. The duration of apneas during the competition ranged from 3 minutes 27 seconds to 5 minutes 33 seconds. The divers exhibited significantly faster heart rates prior to and during the first 90 seconds of apnea in connection with competition, than during training. One subject experienced a loss of motor control during the competition. We suggest that mental stress in humans, caused here by a competitive situation, leads to an increase in the heart rate during apnea.

  • 8. Mekjavić, I. B.
    et al.
    Passias, T.
    Sundberg, C. J.
    Eiken, Ola
    Karolinska Institutet.
    Perception of thermal comfort during narcosis1994In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 21, no 1, p. 9-19Article in journal (Refereed)
    Abstract [en]

    We examined the perception of thermal comfort in six male subjects immersed in water at 28 degrees C (study I) and 15 degrees C (study II), breathing either room air (AIR) or a normoxic mixture containing 30% N2O (N2O). Immersions were terminated if esophageal temperature (Tes) decreased by 2 degrees C from resting levels or to 35 degrees C. At regular intervals, subjects rated their perception of thermal comfort on a 21-point scale (thermal comfort vote, TCV; +10 = very, very hot, 0 = neutral, -10 = very, very cold). For similar decreases in Tes from resting preimmersion values (mean +/- SD = -0.90 degrees +/- 0.13 degrees C and -0.92 degrees +/- 0.15 degrees C during the AIR and N2O trials in study I, and -0.90 degree +/- 0.22 degree C and -0.89 degree +/- 0.27 degree C during the AIR and N2O trials in study II), subjects perceived the immersions as less cold during the N2O trials. The median TCVs for the AIR condition of -5 in study I and -7.75 in study II, were significantly lower than those reported by the subjects for the respective N2O conditions (1.75 in study I and -5.5 in study II). It is concluded that behavioral adjustments required for maintaining thermal balance may be diminished during narcosis due to the altered perception of thermal discomfort. Assuming that the effect of inert gas narcosis on thermoregulatory responses is similar to that of N2O, then combined with the significant attenuation of heat gain mechanisms by anesthetic gases, the attenuation of the perception of thermal comfort may represent a significant factor in the etiology of hypothermia observed in compressed air divers.

  • 9. Ostlund, A
    et al.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Environmental Physiology (Closed 20130701).
    Demetriades, AK
    Linnarsson, D
    Arterial baroreflex control during mild-to-moderate nitrous oxide narcosis.1999In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 26, no 1, p. 15-20Article in journal (Refereed)
    Abstract [en]

    We hypothesized that light-to-moderate inert gas narcosis might play a role in bradycardia in divers by altering sensitivity or response dynamics of arterial baroreflexes. Carotid-cardiac and carotid-mean arterial pressure (MAP) baroreflex response curves were generated by applying multiple levels of neck pressure and suction. Seven healthy volunteers were studied during air breathing (control) and during inhalation of 39% nitrous oxide (N2O). Baseline (pre-stimulus) heart rate (HR) and MAP were not altered by N2O. Range, threshold level, saturation level, and delay of responses did not differ between conditions. For hypertensive stimuli, sensitivity of responses did not differ between air control and N2O inhalation, but for hypotensive stimuli, maximal response gain for HR tended to be reduced with N2O inhalation (P = 0.054). Our results speak against inert gas narcosis as a primary mechanism for hyperbaric bradycardia, but it remains possible that an attenuation of tachycardic responses to hypotensive stimuli plays a role.

  • 10.
    Rodríguez-Zamora, Lara
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Engan, Harald K.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Norwegian Heart & Lung Patient Org, Norway.
    Lodin-Sundström, Angelica
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Schagatay, Fanny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Ecotechnology and Sustainable Building Engineering.
    Iglesias, Xavier
    Univ Barcelona, INEFC Barcelona Sports Sci Res Grp, Barcelona, Spain.
    Rodriguez, Ferran A.
    Univ Barcelona, INEFC Barcelona Sports Sci Res Grp, Barcelona, Spain.
    Schagatay, Erika
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Blood lactate accumulation during competitive freediving and synchronized swimming2018In: Undersea & Hyperbaric Medicine, ISSN 1066-2936, Vol. 45, no 1, p. 55-63Article in journal (Refereed)
    Abstract [en]

    A number of competitive water sports are performed while breath-holding (apnea). Such performances put large demands on the anaerobic system, but the study of lactate accumulation in apneic sports is limited. We therefore aimed to determine and compare the net lactate accumulation (NLA) during competition events in six disciplines of competitive freediving (FD) and three disciplines of synchronized swimming (SSW). The FD disciplines were: static apnea (STA; n = 14) dynamic apnea (DYN; n = 19) dynamic apnea no fins (DNF; n = 16) constant weight (CWT; n = 12) constant weight no fins (CNF; n = 8) free immersion (FIM; n =10) The SSW disciplines were solo (n = 21), duet (n = 31) and team (n = 34). Capillary blood lactate concentration was measured before and three minutes after competition performances, and apneic duration and performance variables were recorded. In all nine disciplines NLA was observed. The highest mean (SD) NLA (mmol.L-1) was found in CNF at 6.3 (2.2), followed by CWT at 5.9 (2.3) and SSW solo at 5 (1.9). STA showed the lowest NLA 0.7 (0.7) mmol.L-1 compared to all other disciplines (P < 0.001). The NLA recorded shows that sports involving apnea involve high levels of anaerobic activity. The highest NLA was related to both work done by large muscle groups and long apneic periods, suggesting that NLA is influenced by both the type of work and apnea duration, with lower NLA in SSW due to shorter apneic episodes with intermittent breathing.

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