PO2 Time limits calculation and planning tarek omar/ tek tribe TDI#5060 PADI#601728 :PO2 Time limits calculation and planning tarek omar/ tek tribe TDI#5060 PADI#601728


Introduction :Introduction Oxygen is essential to life - without it we would not survive. However, when the partial pressure is less than .16 or over 1.6 that can lead to severe complication including death. In this session you will learn how to use O2 safely, and about the risks associated with its misuse.


Agenda :Agenda Oxygen Limits For Life Support System Hyperoxia Signs & symptoms of CNS oxygen toxicity Predisposition Tracking CNS Oxygen exposure Pulmonary and whole body oxygen toxicity


Vocabulary :Vocabulary Hypoxia- experience when the partial pressure drops to .16 ata or below. Initially pulse rate and blood pressure will increases. A small increases in respiration rate may occur. Than symptoms typical of brain function impairment will appear with problem in: concentration, think clearly, fine control of muscle, perform delicate tasks, than confusion, faulty judgment, emotional instability, and muscle function impairment. At .12 ata most individuals will lose their ability to function, and the progress of Hypoxia will eventually will kill the cell. Brain tissue cells are the most susceptible to it effects. Unconsciousness usually occurs at about 0.10 ata, and permanent brain damage and death will probably result below .10 ata. Hyperoxia- is a an abnormal condition resulting from an increases in oxygen supplied to buddy tissue. This can lead to convulsion and death. CNS- Central Nervous System


Topic OneOxygen Limits For Life Support System :Topic OneOxygen Limits For Life Support System .10 Unconsciousness .12 Serious sign of Hypoxia .16 Begin minor signs of Hypoxia .21 Normal environment ( Normal ) .35 Normal saturation exposure .50 Maximum saturation exposure 1.40 Max. exposure heavy exertion exposure / decompression 1.50 Max. technical Nitrox Exposure / Max. recommended exposure 1.60 Max. exposure - recreational divers 2.00 USN exceptional exposure working limit 2.40 60/40 Nitrox therapy gas @ 6 ATA 2.50 Decompression for Op diving ( Max. ) 2.80 100% Oxygen @ 2.8 ATA 3.00 50/50 Nitrox Therapy gas @ 6 ATA CNS O2 TOXICITY PULMONARY O2 TOXICITY


Hyperoxia :Hyperoxia The same gas require to sustain life can be a lethal poison under sufficiently elevated partial pressure. Unfortunately, many recreational divers have developed a rather apathetic attitude with regard to numerical value limit. Many diver perceive that if they can handle Nitrogen narcosis than they will be able to handle Oxygen. However, O2 is not as forgiving as nitrogen - the values are real!


Slide 7:Overt manifestation of CNS oxygen toxicity include a diversity of sign and symptoms ranging from apprehension to convulsion. The diver may experience minor symptoms, but the time interval between recognition of these symptoms and onset of convulsions may be too short to allow the diver to take a correction measure. Of even a greater concern is the fact that minor symptoms do not always precede the onset of convulsions. This can happen even at lower pressure provide that the exposure time is sufficiently long.


Slide 8:Convulsion are the most serious consequence of CNS oxygen toxicity and may occur without being proceeded by any other symptom. During it the diver loses consciousness and the brain sends uncontrolled nerve impulses to the muscles. At the height of the seizure, all muscles are stimulated simultaneously and the body locks into stiffness. Consequence of convulsion underwater are extremely serious with drowning being the primary danger.


There had been only TWO documented cases of divers staying alive after underwater convulsion-do not become a statistic! :There had been only TWO documented cases of divers staying alive after underwater convulsion-do not become a statistic!


Signs & symptoms of CNS oxygen toxicity :Signs & symptoms of CNS oxygen toxicity Con Convulsions V Visual symptoms including dazzle and constriction of visual field (tunnel vision ) E Ear related symptoms including ringing of ears (tinnitus ) and auditory hallucinations N Nausea and spasmodic vomiting T Twitching that usually first appears in the lips and other facial muscles. This is the most common and well-defined symptom I Irritability and behavioral changes including anxiety, confusion, apprehension and depression D Dizziness or vertigo


Predisposition :Predisposition The rate of developing of oxygen toxicity can be accelerated by many reasons: Production and retention of carbon dioxide due to exercise, inadequate ventilation, insufficient carbon dioxide removal in closed-circuit scuba Thermal stress Certain drug such as adrenocortical hormones, dextroaphetamin, einephrin, insulin, norepinephrine, paraquat, hyperthyroidism, vitamin E deficiently, and pseudoephedrin (Sudafed )


Topic Two Tracking CNS Oxygen Exposure :Topic Two Tracking CNS Oxygen Exposure For routine no-stop diving, oxygen time may be based on the oxygen partial pressure at the maximum dive depth and the NOAA oxygen exposure time limits. In technical diving, were two or more gas mixtures are used and extensive time is spent on high oxygen mixture at decompression depth, cumulative oxygen exposure must be tracked.


% CNS = ---------------------- x 100 :% CNS = ---------------------- x 100 Time at Depth NOAA Single Exposure Time at PO2 for specific Depth Using this technique you calculate the percentage of oxygen time used at each depth. The sum of these values is your oxygen exposure for the dive.


Example :Example Diver uses EAN 30 for 40 minutes dive to 100fsw. Decompression is 15 minutes at 10 fsw using EAN 50 Depth PO2 Time at NOAA %CNS (fsw ) Depth Time 90 1.12 50 10 0.65 10 TOTAL


Example :Example Diver uses EAN 30 for 40 minutes dive to 100fsw. Decompression is 12 minutes at 10 fsw using EAN 50 Depth PO2 Time at NOAA %CNS (fsw ) Depth Time 90 1.12 50 210 23.8% 10 0.65 12 570 2.1% TOTAL 25.9%


Slide 16:As a general rule, Time of Exposure is taken as Dive Bottom Time ( ignoring the ascent ) and the oxygen load need to be calculated at the decompression stops if an elevated FO2 (gas switch ) is employed. Minimum Surface Interval: If % CNS is less than 80% - 2 hours If % CNS of 2 or more dive in 24 hours is less than 80 % - 12 hours


Topic threePulmonary and whole body oxygen toxicity :Topic threePulmonary and whole body oxygen toxicity Breathing oxygen at elevated pressures for extremely long duration can induce pulmonary oxygen toxicity This can happen at saturation dives, hyperoxic decompression from deep or long dive, and during extended exposures in the treatment of injured diver. Exposures of 3-6 hours at PO2 of 2 ATA have produce this symptoms.


Topic threePulmonary and whole body oxygen toxicity :Topic threePulmonary and whole body oxygen toxicity Pulmonary toxicity can cause considerable lung damage including interstitial and alveolar edema and intra-alveolar hemorrhage and cell destruction. Unit of Pulmonary Toxic Does (UPTD ) is used to estimate and track pulmonary or whole body oxygen effects. One UPTD is defined as the degree of the toxicity incurred by berating 100% oxygen at a pressure of 1 ATA for one minute.


Slide 19:The accepted limit for treatment with 100% oxygen at 1.0 ATA in a 24 hour period is: 24 x 60 min/hr x 1 UPTD/min = 1440 UPTD During an air 60 min dive to 124 fsw accumulation will be 60 UPTD Same dive based on EAN 32 accumulation will be 111 UPTD


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