Nitrox workshop dings - Divers Alert Network

More documents

Recommendations

Info

Rubicon Foundation Archive (http://rubicon-foundation.org)Kerem etal.: Nitrox and CO 2 RetentionScanning Nitrox Divers For Degree Of CO2 RetentionProfessional DiversScreening for CO 2 retention during nitrox breathing is more readily justified in select smallgroups, backed by a hyperbaric physiological research facility. The Israeli Navy opted to test itsconstruction divers, immersed at their current maximal operational depth, using the Ch-richestnitrox mixture, their personal regulators and at a realistic exercise level (1.2-1.4 L O2/min).Specialized equipment required includes a wet pressure chamber and a fast-response CO2analyzer or, better still, a mass spectrometer to accurately measure end-tidal CO2 tension in lieuof the more pertinent arterial tensions.Measurements were also made, at the same exercise level, breathing air at 1 ATA. Thisattempted to isolate the contribution of the third hypoventilation promoter from that of the first(depth related) two and also to devise a much simpler test that may predict the response at theabove-listed conditions. The figure below shows the correlation of exercise end-tidal PCO 2 whilebreathing air at 1 ATA and 40% nitrox at 4 ATA, in 34 professional Navy divers.The 40 torr mark line in the figure is the mean end-tidal PCO2 for several hundred youngnovice divers exercising on 1 ATA air. The 50 torr line marks 2 SD above this mean and thedefined upper limit for end-tidal PCO2 of "non-retainers". The 55 torr (3 SD above the mean)line brackets the defined range of "moderate CO2 retainers", whilst anything above it is definedas an "extreme CO 2 retainer":6560 -3 55 -I50 -46-135 -303035 40—1—45 50 55end-tidal Pco 2 - Air (torr)60 65CORRELATION BETWEEN END-TIDAL Pco 2IN I ATA AIR & IN 4 ATA NITROX83
Rubicon Foundation Archive (http://rubicon-foundation.org)Lang (ed.): DAN Nitrox Workshop, Divers Alert Network, November 2000It will be seen that as a whole, group values tend to lie above the 40 torr mean, during both 1ATA air and, especially, during nitrox breathing at depth. The group mean end-tidal PCO2 wasnot significantly higher with the latter, attesting to the dominance of the depth-unrelatedindividual trait in determining the degree of hypoventilation. Four non-retainers on air becameso on nitrox (3-6) and two went the other way (1-2). For a small select group, this rather highpercent of false negatives in the air-predictor test is unacceptable and the simulation of actualconditions is called for.We had occasion to test 5 of the above subjects again after four years. The comparisonbetween the two time-spaced measurements for both air and nitrox is shown in the figure below.Numbers 1-5 identify air-Nitrox pairs for each of the 5 subjects. The 1 ATA air values for 4subjects (2-5) have maintained their definition (3 non-retainers and one moderate retainer) overthe years. Subject 2, with time, became a moderate retainer on nitrox and subject 1, a veryexperienced diver who of late very rarely dives, has moved from being an extreme retainer onboth mixtures to being a moderate one on nitrox and a non-retainer on air.• 1 ATA AIR• 4 ATA NITROX6OQ.T3£"5.X9•oS100o>55-50-45 -An•3I4•• 4 • 1 535 -35 40 45 50 551994 mixed-expired Pco 2 (torr)4-YEAR REPEAT TEST OF CO2 RETENTIONIN 5 PROFESSIONAL DIVERS84
Page 1 and 2:
Rubicon Foundation Archive (http://
Page 3 and 4:
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36: Rubicon Foundation Archive (http://
Page 85: Rubicon Foundation Archive (http://
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
show all

Nitrox workshop dings - Divers Alert Network

Create successful ePaper yourself

Delete template?

Save as template?