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Thread: Real limits of PO2

  1. #11
    Resident bibliophile Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs's Avatar
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    Natoli Thesis

    Quote Originally Posted by ScubaDadMiami  View Original Post
    I was just wondering if anyone has anything with more specific material on the subject.
    Sorry for the delay... I missed this thread and thanks to Benthic for pointing me to it. This is a thesis written by my former boss at Duke. It has some nice references as well as answers to the CO2 and O2 tox question. There are others but this is a nice starting point.

    Factors Affecting CNS Oxygen Toxicity in Humans
    Natoli and Vann, 1996
    RRR ID: 123456789/21

    Abstract:
    The onset time of central nervous system (CNS) oxygen toxicity symptoms is reduced by elevated oxygen partial pressure, inspired CO2, immersion, and work. This project investigated the effects of these factors in humans on ventilatory response to CO2, brain cortical oxygenation, and the occurrence of symptoms of CNS oxygen toxicity. Relative changes in cerebral oxygenation from a baseline were measured by near-infrared (NIR) spectroscopy. Ventilatory response was measured during CO2 rebreathing in a computer- controlled, closed-circuit breathing apparatus. The results of this study suggest that inspired C02 is a potent instigator of CNS oxygen toxicity, more potent than oxygen alone or in combination with immersion and work. Thirty-three of the 35 CNS oxygen toxicity symptoms reported, including a convulsion, involved breathing inspired C02 at a Pio2 of 2.80 ATA. Most (31) symptoms were reported while the inspired CO2 was 7.0% -7.5%. Hyperoxia, Pio2= 1.75 or 2.80 ATA, leads to increased cerebrovascular oxygenation despite vasoconstriction. Inspired CO2 reversed vasoconstriction and increasing cerebral oxygenation further. Subjects with symptoms consistent with oxygen toxicity did not show a CO2-induced vasoconstrictive reversal despite increased cerebral oxygenation. This result is contrary to previous findings (Lambertsen 1955) where inspired C02 caused symptoms of CNS oxygen toxicity while increasing cerebral blood flow and increasing cerebral oxygenation. This disparity is most likely due to the difference in the cerebral oxygenation measurements made. NIRS measures regional physiology while cerebral blood flow and blood sampling measurements are global physiological measurements. Ventilatory response to CO2 did not correlate well with symptom incidence but the subject who convulsed had the lowest ventilatory response to CO2 with a Pio2 of 0.21 ATA. The subject who convulsed also had the largest increase in cytochrome a,a3 oxidation with inspired Cog. The combination of the low ventilatory response to CO2 with increased cerebral oxygenation resulting in an oxygen seizure supports the hypothesis that susceptibility to CNS oxygen toxicity may be related to CO2 retention as a result of depressed ventilatory response to CO2 (Lanphier 1975). Facial immersion lead to increased cerebrovascular blood volume and cytochrome a,a3 oxidation at both 0.21 and 2.80 ATA Pio2 and with both positive and negative static lung loads.

    As for high pO2's, it is hard to beat Ken Donald's work "Oxygen and the Diver" (if you can find a copy).

  2. #12
    Nicholas Smith Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo has a reputation beyond repute Abbo's Avatar
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    Re: Real limits of PO2

    Kenneth Donald: Oxygen & the Diver. Prices quoted on Amazon range from $495 (+P&P) up to $1,040.55 (+P&P). I'm feeling a little too inpecunious for that right at the moment. It's a pity there isn't a Wiki facility on Rebreatherworld: the subject keeps coming up.

  3. #13
    Resident bibliophile Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs is a name known to all Gene_Hobbs's Avatar
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    libraries

    Quote Originally Posted by Abbo  View Original Post
    Kenneth Donald: Oxygen & the Diver. Prices quoted on Amazon range from $495 (+P&P) up to $1,040.55 (+P&P). I'm feeling a little too inpecunious for that right at the moment. It's a pity there isn't a Wiki facility on Rebreatherworld: the subject keeps coming up.
    WorldCat lists the book in 23 libraries workwide.

    UHMS members have access to the copy in the Duke University Medical Center Library.

    Other libraries (listed twice in the DB):
    US,CA
    ALIBRIS ALBRS
    US,FL
    BARRY UNIV FBC
    US,HI
    UNIV OF HAWAII AT MANOA HUH
    US,MA
    HARVARD UNIV, MED SCH, COUNTWAY LIBR HMS
    US,MA MARINE BIOLOGICAL LAB/WOODS HOLE OCEANOG MBW
    US,OH BAKER & TAYLOR BAKER
    CA,QC
    CONCORDIA UNIV LIBR CDN
    Ireland
    TRINITY COL, DUBLIN ERD
    South Africa SABINET SZT
    South Africa SANDF Z6Q
    South Africa
    SOUTH AFRICA NAVAL REF LIBR Z6O
    South Africa
    UNIV STELLENBOSCH-MED LIBR Z8Q
    United Kingdom
    BRIDGEND LIBR AND INFO SRV UKBRD
    United Kingdom
    BRITISH LIBR UKM
    United Kingdom
    BRITISH LIBR BRI
    United Kingdom
    CAMBRIDGE UNIV CUD
    United Kingdom
    KENT CNTY COUNCIL ARTS & LIBR UKKCC
    United Kingdom
    UNIV OF OXFORD

    and

    US,CA
    UNIV OF CALIFORNIA, SAN DIEGO CUS
    US,MD
    NATIONAL LIBR OF MED NLM
    US,MD
    US NAVAL ACAD UNA
    US,SD
    UNIV OF SIOUX FALLS

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