Recreational Dive Planner - Metric
Because it was designed to allow multilevel diving, there is no need to convert actual depths into equivalent sea-level depths in order to the use Recreational Dive Planner at 300 metres above sea level or higher. True False
False. The fact that the Recreational Diver Planner was designed to allow multilevel diving has no bearing on the need to convert altitude depths to equivalent sea level depths.
The tissue compartments considered within a decompression model are related directly to specific tissues of the body. True False
False. This is a very common misconception regarding dive table design. Tissues compartments are simply mathematical concepts. They are not intended to relate one-for-one to actual body tissues. In fact, physiologists who design dive tables prefer the term compartment over tissue as a way of avoiding this misconception. Dividing the body into compartments is just a way of describing and predicting what is likely to occur regarding the decompression status. In fact, no one even knows if any conceptual model used to construct a dive table has any actual physiological basis.
Upon exiting the water a diver using the Recreational Dive Planner determines he is in pressure group J. Another diver who is using the U.S. Navy Tables also determines that he is in group J. Is it likely that the two divers have approximately the same dive profile? Yes No Submit
No The diver cannot transfer tables during a repetitive dive. Although both the Recreational Dive Planner and the U.S. Navy Tables use the term J to define a certain amount of residual nitrogen, these exact amounts differ between the two models. The scenario in question is a classic case of "adding apples and oranges." Once a dive is initiated using a particular dive table, that same dive table must be used for any subsequent repetitive diving.
Because they are based on the same theoretical model, pressure groups may be transferred between the RDP Table and eRDPML. True False
True Although the data is displayed in different ways, the model from which all versions of the Recreational Dive Planner were derived is the same. Therefore, in this case it is possible to transfer the pressure groups between the RDP Table and eRDPML. This, however, cannot be done if the table models differ. For example, although both the Recreational Dive Planner and the U.S. Navy Tables both use alphabetic designations for pressure groups, they cannot be transferred from one table to the other. Pressure groups actually relate to a specific amount of nitrogen tension within the body as defined by the particular model. As the models differ, so might the particular nitrogen tensions.
A single-tissue decompression model does not work for the human body because the amount and time required to absorb gas is dependent upon the type of tissue involved and the amount of blood flow to the tissue. True False
True. A single-tissue decompression model does not work for the human body. Although the human body is made up primarily of water, our tissues are highly complex as compared to simple water. The amount and time required to absorb gas is dependent upon two factors: the type of tissue involved and the amount of blood flow to the tissue. This makes constructing a decompression model for humans far more difficult than describing gas absorption/elimination in water.
While several tissue compartments were used to determine the NDLs for both the Recreational Dive Planner and USN Tables, only one tissue compartment was used to control the gas "washout" during the surface interval. True False
True. In terms of off-gassing, the slowest compartment controls a subsequent dive. While several tissue compartments were used to determine the NDLs for both the Recreational Dive Planner and USN Tables, only one tissue compartment was used to control the gas "washout" during the surface interval. In terms of off-gassing, the slowest compartment controls a subsequent dive. In the case of the Navy Tables, they used the 120-minute compartment. The Recreational Dive Planner uses the 60-minute compartment to calculate nitrogen elimination.
Using the Table or eRDPML, what is the no-decompression limit for a dive to 29 metres? a. 20 minutes b. 29 minutes c. 21 minutes d. 22 minutes
a. 20 min Using the RDP Table or eRDPML, the no-decompression limit for a dive to 29 metres is 20 minutes.
You are to use the eRDPML: A diver exits the water at 1:30 p.m. after a dive to 19 metres for 35 minutes. He reenters the water at 2:20 p.m. for a dive to 17 metres for 25 minutes. How soon could the diver reenter the water for a dive to 15 metres for 38 minutes? a. 33 minutes b. 37 minutes c. 1 hour d. 3 hours
a. 33 When using the eRDPML, if a diver exits the water at 1:30 p.m. after a dive to 19 metres for 35 minutes, he will be in pressure group P.He reenters the water at 2:20 p.m. This means his surface interval is 50 minutes. In 50 minutes a diver in pressure group P changes to pressure group G.If he then returns to 17 metres for 25 minutes, he will then be in pressure group S.To determine the minimum surface interval before the third dive, go to the Surface Interval Mode. Input the pressure group S (after the second dive) and enter the third dive -15 metres for 38 minutes.The required surface interval comes up as 33 minutes. To complete the dive profile, a 33 minute surface interval after the second dive puts the diver in pressure group K before the third dive.
You are to use the eRDPML: A diver exits the water at 10:40 a.m. after a dive to 28 metres for 20 minutes. He reenters the water at 12:20 p.m. for a dive to 19 metres for 27 minutes. How soon could the diver reenter the water for a dive to 17 metres for 30 minutes? a. 37 minutes b. 41 minutes c. 1 hour d. 3 hours
a. 37 minutes Let's review the problem. Using the eRDPML, a dive to 28 metres for 20 minutes yields a pressure group of M. Exiting at 10:40 p.m. and entering again at 12:20 gives the diver a surface interval of 1 hour and 40 minutes (1:40).A diver in pressure group M changes to pressure group B in 1:40.A diver in pressure group B after a dive to 19 metres for 27 minutes will exit in pressure group Q.To determine the minimum surface interval before the third dive, go to the Surface Interval Mode. After entering the pressure group (after the second dive) and the third dive depth and time, you'll get 37 minutes as minimum surface interval. If you did not get that answer, you should review the procedure for finding minimum surface intervals in Section 3 of the eRDPML Instructions for Use booklet.
In constructing the U.S. Navy Tables _____________ tissue compartments were used to determine the NDLs. In determining the NDLs for the Recreational Dive Planner _____________ tissue compartments were used. a. 6/14 b. 6/6 c. 12/12 d. 6/34
a. US Navy Tables used 6 tissue compartments. 14 were used for the RDP In constructing the U.S. Navy Tables, 6 tissue compartments were used to determine the NDLs. In determining the NDLs for the Recreational Dive Planner, 14 tissue compartments were used. The Navy constructed their tables almost entirely without the assistance of computers. This made the task difficult and time consuming. Using fewer compartments meant less development time (although this was still one more than Haldane used in his original model). The Recreational Dive Planner, on the other hand, was entirely computer-generated. The number of compartments used for calculation was not significant in terms of time or difficulty. However, there isn't anything innately better about more compartments. In fact, one decompression model, the Canadian Defense and Civilian Institute for Environmental Medical (DCIEM) Tables, uses only four compartments.
The decompression-related problems encountered when diving at altitude occur because the diver begins his dive a. at an atmospheric pressure less than that at sea level. b. at an atmospheric pressure more than that at sea level. c. with a reduced percentage of nitrogen than that at sea level. d. with a reduced percentage of oxygen than that at sea level.
a. at an atmospheric pressure less than that at sea level. The decompression-related problems encountered when diving at altitude occur because the diver begins his dive at an atmospheric pressure less than that at sea level. The Recreational Dive Planner was designed for use assuming the dive starts at an atmospheric pressure of 1 atm. While some reduction in the atmospheric pressure can be tolerated, the Recreational Dive Planner cannot be used at an altitude above 300 metres without special procedures. One of the most important considerations when diving at altitude is converting the actual depth of the water at altitude to an equivalent sea-level depth. This conversion is then used for dive planning purposes.
A diver exits the water at 10:00 a.m. after a dive to 18 metres for 50 minutes. He has made no previous dives. What is the soonest this diver should board a commercial airliner for his flight home? a. 2:00 p.m. b. 10:00 p.m. c. When he enters pressure group D d. 10:00 a.m. the next day
b. 10 pm In this case the diver has made no previous dives. Therefore, he should wait a minimum of 12 hours before flying. However, remember that whenever possible it is suggested that you wait for an extended time beyond 12 hours before flying.
A diver has been on a diving vacation for a week, during which he made in excess of 20 dives. He exits the water at 12:00 noon. What is the soonest this diver should board a commercial airliner for his flight home? a. 2:00 p.m. b. After 6:00 a.m. the next day c. When he enters pressure group D d. 12:00 noon the next day
b. 6am next day In this scenario the diver has been diving for several days. Therefore, according to the recommendations he should wait for a minimum of 18 hours before flying.
A diver is planning a multilevel dive. He wishes to stay at 34 metres for 10 minutes, then ascend to 22 metres for 12 minutes. What will his pressure group be upon exiting the water? a. Group P b. Group O c. Group I d. The dive cannot be made as planned.
b. O After 10 minutes at 34 meters the diver's ending pressure group is G. Ascending to 22 metres in pressure group G for an additional 12 minutes has the diver exiting in pressure group O.
A diver plans a dive to 30 metres for 20 minutes. Losing track of time, he notices that his bottom time is actually 24 minutes. Which of the following procedures should he institute in this situation? a. Immediately ascend to 5 metres and make a stop for 15 minutes; avoid diving for at least 24 hours. b. Immediately ascend to 5 metres and make a stop for 8 minutes; avoid diving for at least 6 hours. c. Immediately ascend to 5 metres and make a stop for 3 minutes. d. Immediately surface - rest - be monitored for signs of decompression sickness - breathe 100% oxygen and do not dive for at least 24 hours. Submit
b. immediately ascend to 5 meters and make a stop for 8 minutes; avoid diving for 6 hrs. He should immediately ascend to 5 metres and make a stop for 8 minutes; avoid diving for at least 6 hours. The diver has exceeded the no-decompression limit for 30 metres. However, the overstay has been for less than 5 minutes. Incidentally, dives should never be planned to the full limit of the table, and this scenario is one reason why.
Upon surfacing a diver realizes he has dived the following profile: 29 metres for 23 minutes. What is the soonest this diver should board a commercial airliner for his flight home? a. 12 hours after exiting the water b. more than 18 hours after exiting the water c. 24 hours after exiting the water d. Only on the advice of a physician
b. more than 18 hours He should wait more than 18 hours after exiting the water. If possible, the diver should wait longer after a dive requiring decompression — or if a decompression stop has been missed — before flying or driving to altitude.
The U.S. Navy selected the 120-minute tissue compartment to control their "Surface Interval Credit Table" because a. they didn't know other compartments could be used. b. they were designing tables that enabled decompression diving. c. as most of their diving is surface air supplied, a different decompression model had to be used. d. this was the easiest way to account for individual differences in physiology.
b. they were designing tables that enabled decompression diving. The U.S. Navy selected the 120-minute tissue compartment to control their "Surface Interval Credit Table" because they were designing tables that enabled decompression diving. The primary function of the U.S. Navy Tables was to enable safer decompression diving. They also realized with the advent of scuba that provisions were necessary for "repetitive diving." This required consideration of how quickly the diver lost residual nitrogen. To accommodate this the Navy developed a "Surface Interval Credit Table." To avoid having to develop several such tables to be used according to which tissue compartment controlled the previous dive, they chose an easier approach — develop only one table based on a single compartment. Determining which compartment to use was simple. As their tables would provide for decompression diving — even repetitive decompression dives — they had to use the slowest tissue compartment in their model; one which would come into play only during decompression dives. That compartment was the 120-minute compartment, which requires 12 hours to fully in or out gas. This explains why it takes up to 12 hours to fully out-gas when using the U.S. Navy Tables.
A 60-minute tissue compartment requires _____________ to fill or empty completely, while a 120-minute compartment requires _____________. a. 1 hour/2 hours b. 2 hours/4 hours c. 6 hours/12 hours d. 12 hours/24 hours
c. 6hours / 12 hours A 60-minute tissue compartment requires 6 hours to fill or empty completely, while a 120-minute compartment requires 12 hours. The term "half-time" is simply a way of representing what is known as an "exponential relationship." In our discussion of decompression theory it's used to describe how quickly a tissue compartment will fill or empty. For example, a tissue compartment described as having a "5-minute halftime" will fill (or empty) half of the total amount of nitrogen it can hold in five minutes. In five more minutes it will be 75% full; in five more minutes 87.5%; in five more 93.6%; in five more 96.9% and finally in six half-times (30 minutes total) the compartment is considered full (or empty) at 98.4% of its capacity (mathematically it never reaches 100%). Therefore, a 60-minute tissue will completely fill or empty in 6 hours (60 x 6 = 360 mins. or 6 hours). A 120-minute tissue compartment will fill or empty in 12 hours (120 x 6 = 720 mins. or 12 hours).
A diver plans a dive to 35 metres for 13 minutes. Upon surfacing he discovers that he misread his timing device. He was actually at depth for 21 minutes. Which of the following procedures should he institute in this situation? a. Reenter the water and decompress at 5 metres for 15 minutes; avoid diving for 24 hours. b. Reenter the water and decompress at 5 metres for 8 minutes; avoid diving for 6 hours. c. Remain on the surface - rest - be monitored for signs of decompression sickness - breathe 100% oxygen and do not dive for at least 24 hours. d. Immediately seek medical attention and recompression treatment.
c. He should remain on the surface, rest, be monitored for signs of decompression sickness, breathe 100% oxygen, and not dive for at least 24 hours. In this scenario the diver has exceeded his NDL substantially. The scenario in this question is easily avoided by always taking a safety stop at the end of a dive, double checking your decompression status while you wait. If an oversight is discovered the safety stop can then become an emergency decompression stop.
A diver is planning a multilevel dive. He wishes to stay at 34 metres for 5 minutes, then ascend to 24 metres for 22 minutes. What will his pressure group be upon exiting the water? a. Group R b. Group S c. Group K d. The dive cannot be made as planned as it is outside the allowable parameters for a multilevel exposure.
d. The dive cannot be made as planned as it is outside the allowable parameters for a multilevel exposure. Let's review the problem. After a dive to 34 metres for 5 minutes the diver's ending pressure group (EPG) is B. If he then ascends to 24 metres his ML limit for that depth is 20 minutes. Remember, on shallower portions of a multilevel dive the bottom time is limited by the ML limit. In this case, 22 minutes would exceed the ML limit.
During a multilevel dive, a diver spends 10 minutes at a depth of 34 metres. If he then wishes to ascend to 26 metres, what would be his remaining no-decompression time during the shallow portion of the dive? a. 19 minutes b. 21 minutes c. 28 minutes d. The dive cannot be made as planned as it is beyond the parameters allowed for a multilevel exposure.
d. The dive cannot be made as planned as it is outside the allowable parameters for a multilevel exposure. Refer to the table in Section 4 of the eRDPML Instructions for Use booklet.
You are to use the Recreational Dive Planner Table or eRDPML: A diver is planning a series of 3 dives. Assume he will use minimum surface intervals, follow all Recreational Dive Planner rules and dive the following exact profiles: Dive 1 - 24 metres for 26 minutes; Dive 2 - 12 metres for 85 minutes; Dive 3 - 11 metres for 61 minutes. In minutes, approximately how long will the entire dive profile take to complete—from start to finish? a. 201 minutes b. 207 minutes c. 356 minutes d. 362 minutes
d. 362 minutes If you indicated response A, you made two mistakes: First, you did not apply the multiple repetitive dive rule (a three hour surface interval is required between dives 2 and 3). Secondly, you did not account for two required 3-minute safety stops (one after dive 1 and dive 2). If you selected response B you remembered the safety stops, but not the multiple repetitive dive rule. If you selected response C, you remembered the multiple repetitive dive rule, but forgot the required safety stops.
You are to use the Recreational Dive Planner Table or eRDPML: A diver exits the water at 10:45 a.m. after a dive to 24 metres for 21 minutes. At 11:15 a.m. he reenters the water for a 36 minute dive to 18 metres. If he wishes to make a third dive after only a 2 minute surface interval, what is the maximum depth to which he may dive and remain for at least 20 minutes? a. 12 metres b. 15 metres c. 18 metres d. The third dive cannot be made with such a short surface interval.
d. The third dive cannot be made with such a short surface interval. Anytime you are planning a series of three or more dives, be sensitive to the "multiple repetitive dive rule." In this case, a minimum surface interval of 1 hour is required even though a much shorter interval could be derived using the regular table or eRDPML procedure. Remember, this special rule does not apply if you are only making one repetitive dive. As a reminder, the rule states, if you are planning 3 or more dives in one day: Beginning with the first dive, if your ending pressure group after any dive is W or X, the minimum surface interval between all subsequent dives is 1 hour. If your ending pressure group after any dive is Y or Z, the minimum surface interval between all subsequent dives is 3 hours.
The Recreational Dive Planner uses a 60-minute tissue compartment to control its "Surface Interval Credit Table" because a. there are no safety factors built into its design. b. the decompression stops are shorter than the Navy Tables. c. it is a better way to account for individual differences in physiology. d. if divers don't exceed the NDLs the slow 120-minute compartment can be virtually ignored.
d. if divers don't exceed the NDL's the slow 120-minute compartment can be virtually ignored. The Recreational Dive Planner uses a 60-minute tissue compartment to control its "Surface Interval Credit Table" because if divers don't exceed the NDLs, the slow 120-minute compartment can be virtually ignored. When Dr. Ray Rogers developed the conceptual model for the Recreational Dive Planner he realized that recreational (no-decompression) divers almost never get into situations where the 120-minute compartment controlled their decompression status. Only divers exceeding the NDLs are controlled by such a long compartment. Therefore, he could base the Recreational Dive Planner surface credit table on a faster tissue compartment than 120-minutes. The question was which compartment to use. Through computer analysis he determined that a 60-minute compartment was sufficient to control over 98% of all recreational dives. To provide for all possibilities — including extended no-decompression bottom times at shallower depths — the special rule for multiple repetitive dives was developed (WXYZ rule).
