Simon has a couple of other articles on that site that are nice reads as well. His initiative with the UHMS Diving Committee to do summaries (in lay terms) of the peer reviewed work in the literature is one of the best ideas I have seen in a long time. I only hope we have them ready to go later this year.
He is also VERY active as a planner for the
DAN Technical Diving Conference coming up in January. This meeting would not be what it is without his hard work. It is almost full so if any of you are planning to register, now is the time.
As for CO2... I put together my short list of must read papers in a thread on another board along with my reasons behind 'why' these are worth the time. In a quick summary though:
Lanphier and Camporesi describe Lanphier's (1-4) work at NEDU to answer the question 'why don't divers breathe enough?'
1.
Higher Inspired Oxygen (PiO2) at 4 ata (404 kPa) accounted for not more than 25% of the elevation in End Tidal CO2 (etCO2) above values found at the same work rate when breathing air just below the surface.
2.
Increased Work of Breathing accounted for most of the elevation of PACO2 (
alveolar gas equation) in exposures above 1 ata (101 kPa), as indicated by the results when helium was substituted for nitrogen at 4 ata (404 kPa).
3.
Inadequate ventilatory response to exertion was indicated by the fact that, despite resting values in the normal range, PetCO2 rose markedly with exertion even when the divers breathed air at a depth of only a few feet.
CO2 is narcotic (5-6) and it can make nitrogen narcosis worse (6-7). Higher levels of CO2 are bad for CNS Oxygen Toxicity (8). Then there is the effect breathing a higher PiCO2 may have on inert gas elimination (9-10).
There is some VERY cool work going on at Duke dealing with CO2 now (11-14). We always need subjects and since some of you seem to be close to Durham, NC...
References:
1. Lanphier. Nitrogen-Oxygen Mixture Physiology, Phases 1 and 2. NEDU Report 1955-07. RRR ID:
3326
2. Lanphier, Lambertsen, and Funderburk. Nitrogen-Oxygen Mixture Physiology - Phase 3. End-Tidal Gas Sampling System. Carbon Dioxide Regulation in Divers. Carbon Dioxide Sensitivity Tests. NEDU Report 1956-02. RRR ID:
3327
3. Lanphier. NITROGEN-OXYGEN MIXTURE PHYSIOLOGY. PHASE 4. CARBON DIOXIDE SENSITIVITY AS A POTENTIAL MEANS OF PERSONNEL SELECTION. PHASE 6: CARBON DIOXIDE REGULATION UNDER DIVING CONDITIONS NEDU Report 1958-07. RRR ID:
3362
4. Lanphier. Nitrogen-Oxygen Mixture Physiology. Phase 5. Added Respiratory Dead Space (Value in Personnel Selection tests) (Physiological Effects Under Diving Conditions). NEDU Report 1956-05. RRR ID:
3809
5. Henning et. al. Behavioral effects of increased CO2 load in divers. Undersea Biomedical Research 1990. RRR ID:
2540
6. Lanphier EH (ed). Unconscious Diver: Respiratory Control and Other Contributing Factors. 25th Undersea and Hyperbaric Medical Society Workshop. UHMS Publication Number 52WS(RC)1-25-82. Bethesda: Undersea and Hyperbaric Medical Society; 1982; 160 pages. RRR ID:
4278
7. Fothergill et. al. Effects of CO2 and N2 partial pressures on cognitive and psychomotor performance. Undersea Biomedical Research 1991. RRR ID:
2576
8. Natoli and Vann. Factors Affecting CNS Oxygen Toxicity in Humans. MS Thesis (Duke) 1996. RRR ID:
26
9. Anderson et. al. Moderate hypercapnia: cardiovascular function and nitrogen elimination. Undersea Hyperb Med. 1993 Sep;20(3):225-32. RRR ID:
2120
10. Bell et. al. An effect of CO2 on the maximum safe direct decompression to 1 bar from oxygen-nitrogen saturation. Undersea Biomed Res. 1986 Dec;13(4):443-55. RRR ID:
3042
11. Forkner et. al. EFFECT OF INSPIRED PO2 ON HEMODYNAMICS AND GAS EXCHANGE DURING IMMERSED EXERCISE AT 122 FSW. 2006 UHMS Abstract. RRR ID:
3664
12. Cherry et. al. EFFECT OF INCREASED RESPIRATORY RESISTANCE ON CARBON DIOXIDE LEVELS AND HEMODYNAMICS IN THE SUBMERGED EXERCISING DIVER. 2007 UHMS Abstract. RRR ID:
5194
13. Pollock et. al. COMPARISON OF END-TIDAL VERSUS ARTERIAL MEASURES OF CARBON DIOXIDE DURING IMMERSED EXERCISE AT SURFACE AND DEPTH. 2007 UHMS Abstract. RRR ID:
5195
14. Moon et. al. THE EFFECT OF STATIC LUNG LOAD ON HEMODYNAMICS AND GAS EXCHANGE DURING PRONE IMMERSED EXERCISE AT 122 FSW. 2007 UHMS Abstract. RRR ID:
5196
Plenty more where these came from...
