Diving Physiology Respiratory Problems

Sources Joiner, J.T. (ed.) NOAA Diving Manual - Diving for Science and Technology, Fourth Edition. Best Publishing Company, Flagstaff, AZ.

Oxygen Toxicity There are two types of oxygen toxicity for which divers must be concerned: –CNS Oxygen Toxicity (Central nervous system) –Whole-Body Oxygen Toxicity

CNS Oxygen Toxicity CNS oxygen toxicity can occur at the high end of PO 2 exposures (typically above 1.6 atm) The end result may be an epileptic-like convulsion not damaging in itself, but could result in drowning

CNS Oxygen Toxicity Susceptibility is highly variable from person to person and even from day to day in a given individual

CNS Oxygen Toxicity Susceptibility is increased by factors that cause an increase in internal PCO 2 such as exercise, breathing dense gas, or breathing against resistance Immersion, dramatic changes in temperature, and physical exertion also increase susceptibility

CNS Oxygen Toxicity Signs and Symptoms are easily remembered with the acronym CONVENTID

CNS Oxygen Toxicity CON – Convulsion V – Visual disturbance, including tunnel vision E – Ear ringing N – Nausea T – Tingling, twitching or muscle spasms, especially of the face and lips I – Irritability, restlessness, euphoria, anxiety D – Dizziness, dyspnea

CNS Oxygen Toxicity The use of air breaks to reduce or postpone CNS oxygen toxicity incidence is common practice in hyperbaric treatments

CNS Oxygen Toxicity The concept of air breaks has been extended to diving situations where supplemental oxygen or high oxygen content mixtures are used for decompression In these types of exposures a five minute air break every 20 minutes is recommended

CNS Oxygen Toxicity The use of oxygen exposure limits for single dive exposures and exposure to high PO 2 during a 24-hour period have been found to be effective in preventing CNS oxygen toxicity

CNS Oxygen Toxicity It should be noted that these limits like those associated with dive tables do not guarantee safety if adhered to Exceeding the limits may not produce a problem, but does increase the risk

CNS Oxygen Toxicity The NOAA Oxygen Exposure Limits should be used to determine your dive time limits for a given PO 2 NOAA Oxygen Exposure Limits PO 2 (atm) Maximum Single Exposure (minutes) Maximum per 24 hr (minutes) Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ

CNS Oxygen Toxicity The chart shows the maximum single dive exposure and the accumulated daily limits at a given PO 2 NOAA Oxygen Exposure Limits PO 2 (atm) Maximum Single Exposure (minutes) Maximum per 24 hr (minutes) Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ

CNS Oxygen Toxicity If more than one dive is planned to the maximum single dive exposure of a PO 2 of 1.6, a surface interval of at least 90 minutes is advised NOAA Oxygen Exposure Limits PO 2 (atm) Maximum Single Exposure (minutes) Maximum per 24 hr (minutes) Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ

CNS Oxygen Toxicity If one or more dives using a PO 2 less than 1.6 reach or exceed the maximum single exposure limit, the diver should spend a minimum of two hours at a normoxic PO 2 (normal oxygen, air) NOAA Oxygen Exposure Limits PO 2 (atm) Maximum Single Exposure (minutes) Maximum per 24 hr (minutes) Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ

CNS Oxygen Toxicity If the Maximum 24- hour Limit is reached in a 24-hour period the diver must spend a minimum of 12 hours at normoxic PO 2 before diving again NOAA Oxygen Exposure Limits PO 2 (atm) Maximum Single Exposure (minutes) Maximum per 24 hr (minutes) Credit: Permission granted by Best Publishing Company (NOAA Diving Manual 4th Ed.) Flagstaff, AZ

Whole-Body Oxygen Toxicity Whole-Body oxygen toxicity is a slow developing condition resulting from exposure to above normal PO 2, generally at levels below those causing CNS toxicity but above a PO 2 of 0.5 atm

Whole-Body Oxygen Toxicity Whole-Body oxygen toxicity is of little concern to divers doing no-stop dives, even when breathing oxygen-enriched mixtures (nitrox), but it may be seen during intensive diving operations or long oxygen treatments in a hyperbaric chamber

Whole-Body Oxygen Toxicity Signs and Symptoms: –Pulmonary irritation resulting in chest pain or discomfort, coughing, inability to take a deep breath without pain or coughing, development of fluid in the lungs, and a reduced vital capacity

Whole-Body Oxygen Toxicity Signs and Symptoms: –Non-pulmonary symptoms include skin numbness and itching, headache, dizziness, nausea, effects on the eyes, and a dramatic reduction of aerobic capacity during exercise

Whole-Body Oxygen Toxicity The risk of developing Whole-Body Oxygen Toxicity is unlikely when using nitrox Procedures have been developed for managing this risk when the diver will be conducting many dives over more than a three day period, and where exposures get lengthy

Whole-Body Oxygen Toxicity REPEX Oxygen Exposure Chart for Tolerable Multiple Day Exposures Exposure Days OTU Average Dose OTU Total Dose As required The REPEX method uses the single dose Oxygen Tolerance Unit (OTU) to track extended operational exposures

Whole-Body Oxygen Toxicity REPEX Oxygen Exposure Chart for Tolerable Multiple Day Exposures Exposure Days OTU Average Dose OTU Total Dose As required The total for a given exposure period is given in the third column

Whole-Body Oxygen Toxicity OTU Calculation Table PO 2 (atm) OTU Per Minute PO 2 (atm) OTU Per Minute PO 2 (atm) OTU Per Minute The OTU Calculation Table provides Per Minute OTU units for a range of PO 2 s