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Gennser, Mikael
Publications (3 of 3) Show all publications
Silvanius, M., Mitchell, S. J., Pollock, N. W., Franberg, O., Gennser, M., Linden, J., . . . Gant, N. (2019). The performance of 'temperature stick' carbon dioxide absorbent monitors in diving rebreathers. Diving and Hyperbaric Medicine, 49(1), 48-56, Article ID PMID 30856667.
Open this publication in new window or tab >>The performance of 'temperature stick' carbon dioxide absorbent monitors in diving rebreathers
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2019 (English)In: Diving and Hyperbaric Medicine, ISSN 1833-3516, Vol. 49, no 1, p. 48-56, article id PMID 30856667Article in journal (Refereed) Published
Abstract [en]

Introduction: Diving rebreathers use canisters containing soda lime to remove carbon dioxide (CO2) from expired gas. Soda lime has a finite ability to absorb CO2. Temperature sticks monitor the exothermic reaction between CO2 and soda lime to predict remaining absorptive capacity. The accuracy of these predictions was investigated in two rebreathers that utilise temperature sticks. Methods: Inspiration and rEvo rebreathers filled with new soda lime were immersed in water at 19 degrees C and operated on mechanical circuits whose ventilation and CO2-addition parameters simulated dives involving either moderate exercise (6 MET) throughout (mod-ex), or 90 minutes of 6 MET exercise followed by 2 MET exercise (low-ex) until breakthrough (inspired PCO2 [PiCO2] = 1 kPa). Simulated dives were conducted at surface pressure (sea-level) (low-ex: Inspiration, n = 5; rEvo, n = 5; mod-ex: Inspiration, n = 7, rEvo, n = 5) and at 3-6 metres' sea water (msw) depth (mod-ex protocol only: Inspiration, n = 8; rEvo, n = 5). Results: Operated at surface pressure, both rebreathers warned appropriately in four o five low-ex tests but failed to do so in the 12 mod-ex tests. At 3-6 msw depth, warnings preceded breakthrough in 11 of 13 mod-ex tests. The rEvo warned conservatively in all five tests (approximately 60 minutes prior). Inspiration warnings immediately preceded breakthrough in six of eight tests, but were marginally late in one test and 13 minutes late in another. Conclusion: When operated at even shallow depth, temperature sticks provided timely warning of significant CO2 breakthrough in the scenarios examined. They are much less accurate during simulated exercise at surface pressure.

Place, publisher, year, edition, pages
Hypercapnia, Monitoring, Technical diving, Soda lime, Equipment
National Category
Health Sciences
urn:nbn:se:kth:diva-249823 (URN)10.28920/dhm49.1.48-56 (DOI)000463069300008 ()30856667 (PubMedID)2-s2.0-85062856026 (Scopus ID)

QC 20190423

Available from: 2019-04-23 Created: 2019-04-23 Last updated: 2019-04-23Bibliographically approved
Gennser, M., Blogg, S. L., Eiken, O. & Mekjavic, I. B. (2018). Indices of Increased Decompression Stress Following Long-Term Bed Rest. Frontiers in Physiology, 9, Article ID 442.
Open this publication in new window or tab >>Indices of Increased Decompression Stress Following Long-Term Bed Rest
2018 (English)In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 9, article id 442Article in journal (Refereed) Published
Abstract [en]

Human extravehicular activity (EVA) is essential to space exploration and involves risk of decompression sickness (DCS). On Earth, the effect of microgravity on physiological systems is simulated in an experimental model where subjects are confined to a 6 degrees head-down bed rest (HDBR). This model was used to investigate various resting and exercise regimen on the formation of venous gas emboli (VGE), an indicator of decompression stress, post-hyperbaric exposure. Eight healthy male subjects participating in a bed rest regimen also took part in this study, which incorporated five different hyperbaric exposure (HE) interventions made before, during and after the HDBR. Interventions i-iv were all made with the subjects lying in 6 degrees HD position. They included (C1) resting control, (C2) knee-bend exercise immediately prior to HE, (T1) HE during the fifth week of the 35-day HDBR period, (C3) supine cycling exercise during the HE. In intervention (C4), subjects remained upright and ambulatory. The HE protocol followed the Royal Navy Table 11 with 100 min spent at 18 m (280 kPa), with decompression stops at 6 m for 5 min, and at 3 m for 15 min. Post-HE, regular precordial Doppler audio measurements were made to evaluate any VGE produced post-dive. VGE were graded according to the Kisman Masurel scale. The number of bubbles produced was low in comparison to previous studies using this profile [Kisman integrated severity score (KISS) ranging from 0-1], and may be because subjects were young, and lay supine during both the HE and the 2 h measurement period post-HE for interventions i-iv. However, the HE during the end of HDBR produced significantly higher maximum bubble grades and KISS score than the supine control conditions (p < 0.01). In contrast to the protective effect of pre-dive exercise on bubble production, a prolonged period of bed rest prior to a HE appears to promote the formation of post-decompression VGE. This is in contrast to the absence of DCS observed during EVA. Whether this is due to a difference between hypo- and hyperbaric decompression stress, or that the HDBR model is a not a good model for decompression sensitivity during microgravity conditions will have to be elucidated in future studies.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2018
bed rest, extravehicular activity, decompression sickness, venous gas emboli, space simulation
National Category
urn:nbn:se:kth:diva-232766 (URN)10.3389/fphys.2018.00442 (DOI)000439071300001 ()2-s2.0-85050226774 (Scopus ID)
Swedish National Space Board, 151-12

QC 20180803

Available from: 2018-08-03 Created: 2018-08-03 Last updated: 2018-08-06Bibliographically approved
Grönkvist, M., LaPelusa, M., Gennser, M. & Machado-Moreira, C. A. (2018). Postural and Daily Variations in the Single-Breath Diffusion Capacity of the Lungs for Carbon Monoxide. Paper presented at International Conference of the American-Thoracic-Society, MAY 18-23, 2018, San Diego, CA. American Journal of Respiratory and Critical Care Medicine, 197
Open this publication in new window or tab >>Postural and Daily Variations in the Single-Breath Diffusion Capacity of the Lungs for Carbon Monoxide
2018 (English)In: American Journal of Respiratory and Critical Care Medicine, ISSN 1073-449X, E-ISSN 1535-4970, Vol. 197Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
National Category
Respiratory Medicine and Allergy
urn:nbn:se:kth:diva-239834 (URN)000449980302298 ()
International Conference of the American-Thoracic-Society, MAY 18-23, 2018, San Diego, CA

QC 20181217

Available from: 2018-12-18 Created: 2018-12-18 Last updated: 2018-12-18Bibliographically approved

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