Oxygen Treatment Tables are more effective and, therefore, preferable over Air
Treatment Tables. Treatment Table 4 can be used with or without oxygen but
should always be used with oxygen if it is available.
Symptoms During Decompression and Surface Decompression (Recompression
Chamber Available). If symptoms of decompression sickness occur in the
water during decompression, follow the flowchart in Figure 21-3. After
completing recompression treatment, observe the diver for at least 6 hours. If any
symptoms recur, treat as a recurrence of Type II symptoms. As an option, the onsite
Diving Supervisor may elect not to recompress the diver 10 feet in the water,
but to remove the diver from the water when decompression risks are acceptable
and treat him in the chamber. When this is done, the surface interval should be 5
minutes or less, with the diver always treated as having Type II symptoms.
Treatment During Surface-Supplied HEO2 and MK 16 Operations.
Treatment of
decompression sickness arising in the water in specific operational environments
is presented in Volume 3 for surface-supplied helium-oxygen dives and Volume 4
for MK 16 diving operations.
Treatment of Symptoms During Sur-D Surface Interval.
If surface decompression
procedures are used, symptoms of decompression sickness may occur during
the surface interval. Because neurological symptoms cannot be ruled out during
this short period, the symptomatic diver is treated as having Type II symptoms,
even if the only complaint is pain.
Treating for Exceeded Sur-D Surface Interval. If the prescribed surface interval
is exceeded but the diver remains asymptomatic, the diver is treated with Treatment
Table 5, or Treatment Table 1A if no oxygen is available. If the diver
becomes symptomatic, the diver is treated as if Type II symptoms were present.
Any symptoms occurring during the chamber stops of Surface Decompression
Tables are treated as recurrences in accordance with Figure 21-6.
Recompression Treatments When Oxygen Is Not Available. If no oxygen is
available, select the appropriate Air Treatment Table in accordance with Figure
21-10, Figure 21-14, Figure 21-15, and Figure 21-16.
Use Table 1A if pain is relieved at a depth less than 66 feet. If pain is relieved at a
depth greater than 66 feet, use Table 2A. Table 3 is used for treatment of serious
symptoms where oxygen cannot be used. Use Table 3 if symptoms are relieved
within 30 minutes at 165 feet. If symptoms are not relieved in less than 30 minutes
at 165 feet, use Table 4.
Descent/Ascent Rates for Air Treatment Tables. The Air Treatment Tables (1A,
2A, 3, and 4 using air) are used when no oxygen is available. They are not as
effective as the Oxygen Treatment Tables. The descent rate is 20 feet per minute;
the ascent rate is not to exceed 1 foot per minute.
Treatment at Altitude. Before starting a recompression therapy, zero the chamber
depth gauges to adjust for altitude. Then use the depths as specified in the treatment
table. There is no need to “Cross Correct” the treatment table depths.
Recompression Treatments When Oxygen Is Available.
Use Oxygen Treatment
Tables 5, 6, 6A, 4, or 7, according to the flowcharts in Figure 21-4, Figure
21-5, and Figure 21-6. The descent rate is 20 feet per minute. Upon reaching treatment
depth not to exceed 60 fsw, place the patient on oxygen. For depth deeper
than 60 fsw, use treatment gas if available. Additional guidelines for each treatment
table are given below.
Treatment Table 5. Treatment Table 5 may be used for the following:
-
Type I (except for cutis-marmorata) symptoms when a
complete neurological examination has revealed no abnormality
-
Asymptomatic omitted decompression of shallow surfacing (20 fsw or less)
-
Asymptomatic omitted decompression of rapid ascent (from deeper than 20 fsw) if the missed decompression is less than 30 minutes
-
Asymptomatic divers who have exceeded surface interval limits following a Sur-D dive
-
Treatment of resolved symptoms following in-water recompression
-
Follow-up treatments for residual symptoms
-
Carbon monoxide poisoning.
-
Gas gangrene.
Performance of Neurological Exam at 60 fsw.
After arrival at 60 fsw a neurological exam shall be performed (see Appendix
5A) to ensure that no overt neurological symptoms (e.g., weakness, numbness,
incoordination) are present. If any abnormalities are found, the stricken
diver should be treated using TreatmentTable 6.
Extending Oxygen Breathing Periods on Treatment Table 5. Treatment
Table 5 may be extended by two oxygen breathing periods at 30 fsw. Air
breaks are not required prior to an extension, between extensions, or prior
to surfacing. In other words, the Diving Supervisor may have the patient
breathe oxygen continuously for 60 minutes at 30 fsw and travel to the
surface while breathing oxygen. If the Diving Supervisor elects to extend
this treatment table, the tender does not require additional oxygen
breathing than currently prescribed.
When Use of Treatment Table 6 is Mandatory.
Treatment Table 6 is mandatory if:
?Type I pain is severe and immediate recompression must be instituted before
a neurological examination can be performed, or
A complete neurological examination cannot be performed, or
Any neurological symptom is present.
These rules apply no matter how rapidly or completely the symptoms resolve
once
recompression begins.
Complete Relief after 10 Minutes. If complete relief of Type I
symptoms is not
obtained within 10 minutes at 60 feet, Table 6 is required.
Musculoskeletal Pain Due to Orthopedic Injury. Symptoms of
musculoskeletal
pain that have shown absolutely no change after the second oxygen breathing
period at 60 feet may be due to orthopedic injury rather than decompression
sickness.
If, after reviewing the patient’s history, the Diving Medical Officer feels
that
the pain can be related to specific orthopedic trauma or injury, Treatment
Table 5
may be completed. If no Diving Medical Officer is on site, Treatment Table 6
shall be used.
NOTE Once recompression to 60 feet is done, Treatment Table 5 shall be used
even if it was decided symptoms were probably not decompression
sickness. Direct ascent to the surface is done only in emergencies.
Treatment Table 6. Treatment Table 6 is used for the following:
-
Type I symptoms where relief is not complete within 10 minutes at 60 feet
or
where a neurological exam is not complete
-
Type II symptoms
-
Cutis marmorata
-
Severe carbon monoxide poisoning, cyanide
poisoning, or smoke inhalation
-
Arterial gas embolism
-
Symptomatic uncontrolled ascent
-
Asymptomatic divers with omitted decompression
greater than 30 minutes
-
Treatment of unresolved symptoms following
in-water treatment
-
Recurrence of symptoms shallower than 60 fsw.
Treating Arterial Gas Embolism. Arterial gas
embolism is treated by initial compression to 60 fsw. If symptoms are
improved within the first oxygen breathing period, then treatment is
continued using Treatment Table 6. Treatment Table 6 may be extended for two
oxygen breathing periods at 60 fsw (20 minutes on oxygen, then 5 minutes on
air, then 20 minutes on oxygen) and two oxygen breathing periods at 30 fsw
(15 minutes on air, then 60 minutes on oxygen, then 15 minutes on air, then
60 minutes on oxygen). If there has been more than one extenstion, the
tenders’ breathing period is extended 60 minutes at 30 feet.
Treatment Table 6A. Arterial gas embolism or severe decompression
symptoms are treated by initial compression to 60 fsw. If symptoms improve,
complete Treatment Table 6. If symptoms are unchanged or worsen, assess the
patient upon descent and compress to depth of relief (significant
improvement), not to exceed 165 fsw. Once at the depth of relief, begin
treatment gas (N2O2, HeO2) if available. Stay there for 30 minutes. A
breathing period of 25 minutes on treatment gas, interrupted by 5 minutes of
air, is recommended at depth to simplify time keeping. The patient may
remain on treatment gas during ascent from treatment depth to 60 fsw since
the PO2 will continually decrease during ascent. Decompress to 60 fswat a
travel rate not to exceed 3 ft./min. Upon arrival at 60 fsw, complete
Treatment Table 6. Consult with a Diving Medical Officer at the earliest
opportunity. The Diving Medical Officer may recommend a Treatment Table 4.
Treatment Table 6A may be extended for two oxygen breathing periods at 60
fsw and two oxygen breathing periods at 30 fsw. If deterioration is noted
during ascent to 60 feet, treat as a recurrence of symptoms (Figure 21-6).
Treatment Table 4. If a shift from Treatment Table 6A to Treatment
Table 4 is contemplated, a Diving Medical Officer shall be consulted before
the shift is made. Treatment Table 4 is used when it is determined that the
patient would receive additional benefit at depth of significant relief, not
to exceed 165 fsw. The time at depth shall be between 30 to 120 minutes,
based on the patient’s response.
Recurrence of Symptoms. If deterioration is
noted during ascent to 60 feet, treat as a recurrence of symptoms (Figure
21-6).
Oxygen Breathing Periods. If oxygen is available, the patient should begin
oxygen breathing periods immediately upon arrival at the 60-foot stop. Breathing
periods of 25 minutes on oxygen, interrupted by 5 minutes of air, are recommended
because each cycle lasts 30 minutes. This simplifies timekeeping.
Immediately upon arrival at 60 feet, a minimum of four oxygen breathing periods
(for a total time of 2 hours) should be administered. After that, oxygen breathing
should be administered to suit the patient’s individual needs and operational
conditions (paragraph 21-5.5.6). Both the patient and tender must breathe oxygen
for at least 4 hours (eight 25-minute oxygen, 5-minute air periods), beginning no
later than 2 hours before ascent from 30 feet is begun. These oxygen-breathing
periods may be divided up as convenient, but at least 2 hours’ worth of oxygen
breathing periods should be completed at 30 feet.
Treatment Table 7. Treatment Table 7 is considered an heroic measure for
treating non-responding severe gas embolism or life-threatening decompression
sickness. Committing a patient to a Treatment Table 7 involves isolating the
patient and having to minister to his medical needs in the recompression chamber
for 48 hours or longer. Experienced diving medical personnel shall be on scene.
Considerations. A Diving Medical Officer shall be consulted before shifting to a
Treatment Table 7 and careful consideration shall be given to life support capability
(paragraph 21-5.6). In addition, it must be realized that the recompression
facility will be committed for 48 hours or more.
Indications. Treatment Table 7 is an extension at 60 feet of Treatment Tables 6,
6A, or 4 (or any other nonstandard treatment table). This means that considerable
treatment has already been administered. Treatment Table 7 is not designed to
treat all residual symptoms that do not improve at 60 feet and should never be used
to treat residual pain. Treatment Table 7 should be used only when loss of life may
result if the currently prescribed decompression from 60 feet is undertaken.
Consultation with NEDU or NDSTC. Because it is difficult to judge whether a
particular patient’s condition warrants Treatment Table 7, additional consultation
from either NEDU or NDSTC must be obtained. Telephone numbers are listed in
Appendix 1C.
Time at Depth. When using Treatment Table 7, a minimum of 12 hours should be
spent at 60 feet, including time spent at 60 feet from Treatment Table 4, 6, or 6A.
Severe Type II decompression sickness and/or arterial gas embolism cases may
continue to deteriorate significantly over the first several hours. This should not be
cause for premature changes in depth. Do not begin decompression from 60 feet
for at least 12 hours. At completion of the 12-hour stay, the decision must be made
whether to decompress or spend additional time at 60 feet. If no improvement was
noted during the first 12 hours, benefit from additional time at 60 feet is unlikely
and decompression should be started. If the patient is improving but significant
residual symptoms remain (e.g., limb paralysis, abnormal or absent respiration),
additional time at 60 feet may be warranted. While the actual time that can be
spent at 60 feet is unlimited, the actual additional amount of time beyond 12 hours
that should be spent can only be determined by a Diving Medical Officer (inconsultation with on-site supervisory personnel), based on the patient’s response
to therapy and operational factors. When the patient has progressed to the point of
consciousness, can breathe independently, and can move all extremities, decompression
can be started and maintained as long as improvement continues. Solid
evidence of continued benefit should be established for stays longer than 18 hours
at 60 feet. Regardless of the duration at the recompression below 60 feet, at least
12 hours must be spent at 60 feet and then Table 7 followed to the surface. Additional
recompression below 60 feet in these cases should not be undertaken unless
adequate life support capability is available.
Decompression. When using Treatment Table 7, tenders breathe chamber atmosphere.
Chamber oxygen should be kept above 19 percent
and carbon dioxide below 1.5 percent surface equivalent (sev) (11.4 mmHg) (paragraph
21-5.6.4). Decompression on Treatment Table 7 is begun with an upward
excursion at time zero from 60 to 58 feet. Subsequent 2-foot upward excursions
are made at time intervals appropriate to the rate of decompression:
Depth
Rate
Time Interval
58-40 feet 3
ft/hr 40 min
40-20 feet 2
ft/hr 60 min
20-4
feet 1 ft/hr 1 20 min
Preventing Inadvertent Early Surfacing. Upon arrival at 4 feet, decompression
should be stopped for 4 hours. At the end of 4 hours at 4 feet, decompress to the
surface at 1 foot per minute. This procedure prevents inadvertent early surfacing.
Time Intervals. The travel time between subsequent steps is considered as part of
the time interval for the next shallower stop. The time intervals shown above begin
when ascent to the next shallower stop has begun.
Oxygen Breathing. On a Treatment Table 7, patients should begin oxygen
breathing periods as soon as possible at 60 feet. Oxygen breathing periods of 25
minutes on 100 percent oxygen, followed by 5 minutes breathing chamber atmosphere,
should be used. Normally, four oxygen breathing periods are alternated
with 2 hours of continuous air breathing. In conscious patients, this cycle should
be continued until a minimum of eight oxygen breathing periods have been administered
(previous 100 percent oxygen breathing periods may be counted against
these eight periods). Beyond that, oxygen breathing periods should be continued
as recommended by the Diving Medical Officer, as long as improvement is noted
and the oxygen is tolerated by the patient. If oxygen breathing causes significant
pain on inspiration, it should be discontinued unless it is felt that significant
benefit from oxygen breathing is being obtained. In unconscious patients, oxygen
breathing should be stopped after a maximum of 24 oxygen breathing periods
have been administered. The actual number and length of oxygen breathing
periods should be adjusted by the Diving Medical Officer to suit the individual
patient’s clinical condition and response to oxygen toxicity (paragraph 21-5.5.6.2).
Sleeping, Resting, and Eating. At least two tenders should be available when
using Treatment Table 7, and three may be necessary for severely ill patients. Not
all tenders are required to be in the chamber, and they may be locked in and out as
required following appropriate decompression tables. The patient may sleep
anytime except when breathing oxygen deeper than 30 feet. While asleep, the
patient’s pulse, respiration, and blood pressure should be monitored and recorded
at intervals appropriate to the patient’s condition. Food may be taken at any time
and fluid intake should be maintained as outlined in paragraph 21-5.5.7.
Ancillary Care. Patients on Treatment Table 7
requiring intravenous and/or drug therapy should have these administered in
accordance with paragraph 21-5.5.7 and paragraph 21-5.5.7.1.
Life Support. Before committing to a Treatment Table 7, the life-support considerations
in paragraph 21-5.6 must be addressed. Do not commit to a Treatment
Table 7 if the internal chamber temperature cannot be maintained at 85°F (29.4°C)
or less (paragraph 21-5.6.5).
Abort Procedures. In some cases, a Treatment Table 7 may have to be terminated
early. If extenuating circumstances dictate early decompression and less than 12
hours have elapsed since treatment was begun, decompression may be accomplished
using the appropriate 60-foot Air Decompression Table as modified
below. The 60-foot Air Decompression Tables may be used even if time was spent
between 60 and 165 feet (e.g., on Table 4 or 6A), as long as at least 3 hours have
elapsed since the last excursion below 60 feet. If less than 3 hours have elapsed, or
if any time was spent below 165 feet, use the Air Decompression Table appropriate
to the maximum depth attained during treatment. All stops and times in the
Air Decompression Table should be followed, but oxygen-breathing periods
should be started for all chamber occupants as soon as a depth of 30 feet is
reached. All chamber occupants should continue oxygen-breathing periods of 25
minutes on 100 percent oxygen, followed by 5 minutes on air, until the total time
breathing oxygen is one-half or more of the total decompression time.
If more than 12 hours have elapsed since treatment was begun, the decompression
schedule of Treatment Table 7 shall be used. In extreme emergencies, the abort
recommendations (paragraph 21-8) may be used if more than 12 hours have
elapsed since beginning treatment.
Treatment Table 8. Treatment Table 8 is an adaptation of a Royal Navy Treatment
Table 65 mainly for treating deep uncontrolled ascents (see Volume 3) when
more than 60 minutes of decompression have been missed. Compress symptomatic
patient to depth of relief not to exceed 225 fsw. Initiate Treatment Table 8
from depth of relief. The Table 8 schedule from 60 feet is the same as Treatment
Table 7.
Treatment Table 9. Treatment Table 9 is a hyperbaric oxygen treatment table
using 90 minutes of oxygen at 45 feet. This table is recommended by the Diving
Medical Officer cognizant of the patient’s medical condition. Treatment Table 9 is
used for the following:
-
Residual symptoms from AGE/DCS
-
Carbon monoxide or cyanide poisoning
-
Smoke inhalation
-
Medical hyperbaric oxygen therapy
This table may also be recommended by the cognizant Diving Medical Officer
when initially treating a severely injured patient whose medical condition
precludes long absences from definitive medical care.
Tending the Patient. When conducting a recompression treatment, at least one
qualified tender shall be inside the chamber (Figure 21-1). The inside tender shall
be familiar with all treatment procedures and the signs, symptoms, and treatment
of all diving-related disorders.
DMO or DMT Inside Tender. If it is known before the treatment begins that
involved medical aid must be administered to the patient, or if the patient is
suspected of suffering from arterial gas embolism, a Diving Medical Technician or
Diving Medical Officer should accompany the patient inside the chamber.
However, recompression treatment must not be delayed.
Use of DMO. If only one Diving Medical Officer is present, the Medical Officer’s
time in the chamber should be kept to a minimum because effectiveness in
directing the treatment is greatly diminished when inside the chamber. If periods
in the chamber are necessary, visits should be kept within no-decompression limits
if possible.
Patient Positioning. Inside the chamber, the tender ensures that the patient is
lying down and positioned to permit free blood circulation to all extremities. The
tender closes and secures the inner lock door and pressurization begins at 20 fpm.
Equalizing During Descent. Descent rates may have to be decreased as necessary
to allow the patient to equalize; however, it is vital to attain treatment depth in a
timely manner for a suspected arterial gas embolism patient.
Inside Tender Responsibilities. During the early phases of treatment, the inside
tender must monitor the patient constantly for signs of relief. Drugs that mask
signs of the illness should not be given. Observation of these signs is the principal
method of diagnosing the patient’s illness. Furthermore, the depth and time of
their relief designates the treatment table to be used. The inside tender is also
responsible for:
-
Releasing the door latches (dogs) after a seal is
made.
-
Communications with outside personnel.
-
Providing first aid as required by the patient.
-
Administering treatment gas to the patient at
treatment depth.
-
Providing normal assistance to the patient as
required.
-
Ensuring that sound attenuators for ear protection
are worn during compression and ventilation portions of recompression
treatments.
Oxygen Breathing and Toxicity During Treatments. During prolonged treatments
on Treatment Tables 4, 7, or 8, pulmonary oxygen toxicity may develop.
Acute CNS oxygen toxicity may develop on any oxygen treatment table. Refer to
paragraph 19-2.4 for further discussion of oxygen toxicity during in-water dives.
Central Nervous System Oxygen Toxicity. When employing the oxygen treatment
tables, tenders must be particularly alert for the early warning signs of CNS
oxygen toxicity. The warning signs can be remembered readily by using the
mnemonic VENTIDC (Vision, Ears, Nausea, TwitchingTingling, Irritability,
Dizziness, Convulsions). For additional information, refer to paragraph 19-2.4.2.
Procedures in the Event of Oxygen Toxicity. At the first sign of CNS oxygen
toxicity, the patient should be removed from oxygen and allowed to breathe
chamber air. Oxygen breathing may be restarted 15 minutes after all symptoms
have subsided. If symptoms of CNS oxygen toxicity develop again, interrupt
oxygen breathing for another 15 minutes. If CNS oxygen toxicity develops a third
time, contact a Diving Medical Officer as soon as possible to modify oxygen
breathing periods to meet requirements
Interruptions Due to Oxygen Toxicity. CNS oxygen toxicity is unlikely in resting
individuals at depths of 50 feet or shallower and very unlikely at 30 feet or shallower,
regardless of the level of activity. However, patients with severe Type II
decompression sickness or arterial gas embolism symptoms may be abnormally
sensitive to CNS oxygen toxicity. Convulsions unrelated to oxygen toxicity may
also occur and may be impossible to distinguish from oxygen seizures.Figure Figure 21-8, and Figure 21-9 explain how to handle interruptions in oxygen
breathing on Treatment Tables 5, 6, and 6A. Treatment Tables 4, 7, and 8 do not
require compensatory lengthening or alteration if oxygen breathing must be interrupted.
If an oxygen convulsion occurs, discontinue oxygen and keep the patient
from harm. Inserting an airway device or bite block is unnecessary while the
patient is convulsing; it is not only difficult but may cause harm if attempted.
Pulmonary Oxygen Toxicity. Pulmonary oxygen toxicity is unlikely to develop
on Treatment Tables 5, 6, or 6A. On Treatment Tables 4, 7, or 8, the large amounts
of oxygen that may have to be administered may result in end-inspiratory discomfort,
progressing to substernal burning and severe pain on inspiration. Substernal
burning is normally cause for discontinuing oxygen breathing in patients who are
responding well to treatment. However, if a significant neurological deficit
remains and improvement is continuing (or if deterioration occurs when oxygen
breathing is interrupted), oxygen breathing should be continued as long as considered
beneficial or until pain limits inspiration. If oxygen breathing must be
continued beyond the period of substernal burning, or if the 2-hour air breaks on
Treatment Tables 4, 7, or 8 cannot be used because of deterioration upon the
discontinuance of oxygen, the oxygen breathing periods should be changed to 20
minutes on oxygen, followed by 10 minutes breathing chamber air. The Diving
Medical Officer may tailor the above guidelines to suit individual patient response
to treatment.
Ancillary Care and Adjunctive Treatments. Drug therapy should be administered
only after consultation with a Diving Medical Officer. Chamber tenders shall be
adequately trained and be capable of administering prescribed treatments. Always
ensure patients are adequately hydrated. Fully conscious patients may be given
fluid by mouth to maintain adequate hydration. One to two liters of water, juice, or
non-carbonated drink, over the course of a Treatment Table 5 or 6, is usually sufficient.
Patients with Type II symptoms, or symptoms of arterial gas embolism,
should be considered for IV fluids. Stuporous or unconscious patients should
always be given IV fluids, using large-gauge plastic catheters. If trained personnel
are present, an IV should be started as soon as possible and kept dripping at a rate
of 75 to 100 cc/hour, using isotonic fluids (Lactated Ringer’s Solution, Normal
Saline) until specific instructions regarding the rate and type of fluid administration
are given by qualified medical personnel. Avoid solutions containing only
Dextrose (D5W) as they may contribute to edema as the sugar is metabolized. In
some cases, the bladder may be paralyzed. The victim’s ability to void shall be
assessed as soon as possible. If the patient cannot empty a full bladder, a urinary
catheter shall be inserted as soon as possible by trained personnel. Always inflate
catheter balloons with liquid, not air. Adequate fluid is being given when urine
output is at least 0.5cc/kg/hr. A gauge of proper hydration is a clear colorless
urine.
Steroids. There is no consensus on the usefulness of adjunctive therapy, other
than IV fluids. The most frequently recommended adjunctive therapy is dexamethasone
(Decadron), based on the following reasons:
-
It decreases tissue swelling (edema)
-
It decreases tissue inflammation
-
It decreases leaking of blood vessels
-
It helps prevent histamine release
General opinion is that spinal cord and brain edema cause many late-appearing
neurologic problems in DCS. Research suggests that dexamethasone is not useful
during treatment of AGE. In this case steroids may be useful but their efficiency
has not been proven. They do not become effective, however, for 4 to 6 hours after
intravenous introduction. Therefore, administer these drugs early in the treatment.
Do not delay recompression while preparing these drugs. For cerebral edema, the
initial recommended dose is 30 mg/kg IV bolus, followed by a constant infusion of
5.4 mg/kg/hr of methylprednisolone. Continue infusion for 23 hours. No benefit
has been documented if steroid treatment was not started within 8 hours of
symptoms.
Lidocaine. Several studies suggest that Lidocaine used in antiarrhymic doses
(loading dose 1.5 mg/kg drip rate 1 mg/min) may be useful. Its mechanism of
action for treating DCS has been hypothesized as:
-
Reduction of cerebral metabolic rate
-
Preservation of cerebral blood flow
-
Reduction leukocyte adherence to damaged endothelium
NOTE Steroids or other drugs can be used only upon
the prescription by and under supervision of a Diving Medical Officer.
Sleeping and Eating. The only time the patient should be kept awake during
recompression treatments is during oxygen breathing periods at depths greater
than 30 feet. Travel between decompression stops on Treatment Tables 4, 7, and 8
is not a contra-indication to sleeping. While asleep, vital signs (pulse, respiratory
rate, blood pressure) should be monitored as the patient’s condition dictates. Any
significant change would be reason to arouse the patient and ascertain the cause.
Food may be taken by chamber occupants at any time. Adequate fluid intake
should be maintained as discussed in paragraph 21-5.5.7.
Recompression Chamber Life-Support Considerations. The short treatment tables
(Oxygen Treatment Tables 5, 6, 6A; Air Treatment Tables 1A and 2A) can be
accomplished easily without significant strain on either the recompression
chamber facility or support crew. The long treatment tables (Tables 3, 4, 7, and 8)
will require long periods of decompression and may tax both personnel and hardware
severely.
Minimum Manning Requirements. The minimum team for conducting any recompression
operation shall consist of three individuals. In case of emergency, the
recompression chamber can be manned with two individuals.
1. The Diving Supervisor is in complete charge at the
scene of the operation, keeping individual and overall times on the
operation, logging progress,
and communicating with personnel inside the
chamber.
2. The Outside Tender is responsible for the operation of gas supplies,
ventilation, pressurization, and exhaust of the chamber.
3. The Inside Tender is familiar with the diagnosis and treatment of divingrelated sicknesses.
Optimum Manning Requirements. The optimum team
for conducting recompression operations consists of four individuals:
1. The Diving Supervisor is in complete charge at the scene of the
operation.
2. The Outside Tender #1 is responsible for the operation of the gas supplies,ventilation, pressurization, and exhaust of the chamber.
3. The Outside Tender #2 is responsible for keeping individuals’ and overalltimes on the operation, logging progress as directed by the Diving
Supervisor,and communicating with personnel inside the chamber.
4. The Inside Tender is familiar with the diagnosis and treatment of divingrelated sicknesses.
Additional Personnel. If the patient has symptoms of serious decompression sickness
or arterial gas embolism, the team will require additional personnel. If the
treatment is prolonged, a second team may have to relieve the first team. Patients
with serious decompression sickness and gas embolism would initially be accompanied
inside the chamber by a Diving Medical Technician or Diving Medical
Officer, if possible. However, treatment should not be delayed to comply with this
recommendation.
Required Consultation by a Diving Medical Officer. A Diving Medical Officer
shall be consulted, if at all possible, before committing the patient to a Treatment
Table 4, 7, or 8. The Diving Medical Officer may be on scene or in communication
with the Diving Supervisor.
Oxygen Control. All treatment schedules listed in this chapter are usually
performed with a chamber atmosphere of air. To accomplish safe decompression,
the oxygen percentage should not be allowed to fall below 19 percent. Oxygen
may be added to the chamber by ventilating with air or by bleeding in oxygen
from an oxygen breathing system. If a portable oxygen analyzer is available, it can
be used to determine the adequacy of ventilation and/or addition of oxygen. If no
oxygen analyzer is available, ventilation of the chamber in accordance with paragraph
21-5.6.6 will ensure adequate oxygenation. Chamber oxygen percentages as
high as 25 percent are permitted. If the chamber is equipped with a life-support
system so that ventilation is not required and an oxygen analyzer is available, the
oxygen level should be maintained between 19 percent and 25 percent. If chamber oxygen goes above 25 percent, ventilation with air should be used to bring the
oxygen percentage down.
Carbon Dioxide Control. Ventilation of the chamber in accordance with paragraph
21-5.6.6 will ensure that carbon dioxide produced metabolically does not
cause the chamber carbon dioxide level to exceed 1.5 percent SEV (11.4 mmHg).
Carbon Dioxide Monitoring. Chamber carbon dioxide should be monitored with
electronic chamber carbon dioxide monitors. Monitors generally read CO2
percentage once chamber air has been exhausted to the surface. The CO2 percent
reading at the surface 1 ata must be corrected for depth. To keep chamber CO2
below 1.5 percent SEV (11.4 mmHg), the surface CO2 monitor values should
remain below 0.8 percent with chamber depth at 30 feet, 0.54 percent with
chamber depth at 60 feet, and 0.25 percent with the chamber at 165 feet. If the
CO2 analyzer is within the chamber, no correction to the CO2 readings is
necessary.
Carbon Dioxide Scrubbing. If the chamber is equipped with a carbon dioxide
scrubber, the absorbent should be changed when the partial pressure of carbon
dioxide in the chamber reaches 1.5 percent SEV (11.4 mmHg). If absorbent cannot
be changed, supplemental chamber ventilation will be required to maintain
chamber CO2 at acceptable levels. With multiple or working chamber occupants,
supplemental ventilation may be necessary to maintain chamber CO2 at acceptable
levels.
Carbon Dioxide Absorbent. CO2 absorbent may be used beyond the expiration
date, when used in a recompression chamber scrubber unit, when the recompression
chamber is equipped with a CO2 monitor. When employed in a
recompression chamber that has no CO2 monitor, CO2 absorbent in an opened but
resealed bucket may be used until the expiration date on the bucket is reached.
Pre-packed, double-bagged canisters shall be labeled with the expiration date from
the absorbent bucket.
Temperature Control. If possible, internal chamber temperature should be maintained
at a level comfortable to the occupants. Cooling can usually be
accomplished by chamber ventilation in accordance with paragraph 21-5.6.6. If
the chamber is equipped with a heater/chiller unit, temperature control can usually
be maintained for chamber occupant comfort under any external environmental
conditions. Usually, recompression chambers will become hot and must be cooled
continuously. Chambers should always be shaded from direct sunlight. The
maximum durations for chamber occupants will depend on the internal chamber
temperature as listed in Table 21-4. Never commit to a treatment table that will
expose the chamber occupants to greater temperature/time combinations than
listed in Table 21-4 unless qualified medical personnel who can evaluate the tradeoff
between the projected heat stress and the anticipated treatment benefit are
consulted. A chamber temperature below 85°F (29.4°C) is always desirable, no
matter which treatment table is used.
Patient Hydration. Successful treatment of decompression sickness depends upon
adequate hydration. Thirst is an unreliable indicator of the water intake necessary
to compensate for heavy sweating, and isolation of the patient within the recompression
chamber makes it difficult to assess his overall fluid balance. By
providing adequate hydration and following the temperature/time guidelines in
Table 21-4, heat exhaustion and heat stroke can be avoided. If the chamber
temperature is above 85°F (29.4°C), tenders should monitor patients for signs of
thermal stress. If the chamber temperature is above 85°F, chamber occupants
should drink approximately one liter of water hourly; below 85°F they should
drink an average of one-half liter hourly. Clear colorless urine in patients and
tenders is a good indication of adequate hydration.
Chamber Ventilation. Ventilation is the usual means of controlling oxygen level,
carbon dioxide level, and temperature. Ventilation using air is required for chambers
without carbon dioxide scrubbers and atmospheric analysis. A ventilation rate
of two acfm for each resting occupant, and four acfm for each active occupant,
should be used. Chamber ventilation procedures are presented in paragraph
22-5.4. These procedures are designed to assure that the effective concentration of
carbon dioxide will not exceed 1.5 percent SEV (11.4 mmHg) and that, when
oxygen is being used, the percentage of oxygen in the chamber will not exceed 25
percent.
Access to Chamber Occupants. Recompression treatments usually require access
to occupants for passing in items such as food, water, and drugs and passing
out such items as urine, excrement, and trash. Never attempt a treatment longer
than a Treatment Table 6 unless there is access to inside occupants. When doing a
Treatment Table 4, 7, or 8, a double-lock chamber is mandatory because additional
personnel may have to be locked in and out during treatment.
Tenders. For Type I decompression sickness, one qualified inside tender
is required. For Type II decompression sickness, medical personnel may have to
be locked into the chamber as the patient’s condition dictates. If one Diving
Medical Officer is on site, the Medical Officer should lock in and out as the
patient’s condition dictates, but should not commit to the entire treatment unless
absolutely necessary. Once committed to remain in the chamber, the Diving
Medical Officer will not be able to aid the treatment as well and consultation with
other medical personnel becomes more difficult.
Oxygen Breathing. During treatments, all chamber occupants may breathe 100
percent oxygen at depths of 45 feet or shallower without locking in additional
personnel. Tenders should not fasten the oxygen masks to their heads, but should
hold them on their faces. When deeper than 45 feet, at least one chamber occupant
must breathe air.
Table 4. On Table 4, tenders are required to breathe oxygen for 2 hours before
leaving 30 feet and for 2 additional hours during decompression from 30 feet to
the surface.
21-5.6.8.1.2 Table 5. On Table 5, oxygen should be breathed by the tender during the final 30-
minute ascent to the surface. If the tender has had a previous hyperbaric exposure,
an additional 20 minutes of oxygen breathing is required at 30 feet prior to ascent.
(See Table 21-6.)
Table 6. For an unmodified Table 6 or when there has been only a single extension
at 60 or 30 feet, the tender breathes 100 percent oxygen for the final 30
minutes at 30 feet and during ascent to the surface. If there has been more than one
extension, oxygen breathing is done for the last 60-minute period at 30 feet and
during ascent to the surface. If the tender has had a dive/hyperbaric exposure
within the past 12 hours, an additional 60-minute oxygen period at 30 feet is
required. (See Table 21-6.)
Table 6A. For an unmodified Table 6A or when there has been only a single
extension at 60 or 30 feet, the tender breathes 100 percent oxygen for the final 60
minutes at 30 feet and during ascent to the surface. If there has been more than one
extension, oxygen breathing is done for 90 minutes at 30 feet and during ascent to
the surface. If the tender has had a dive/hyperbaric exposure within the past 12
hours, an additional 60-minutes of oxygen at 30 feet is required. (See Table 21-6.)
Table 9. On Table 9, the tender breathes 100 percent oxygen during the last 15
minutes at 45 feet and during ascent to the surface, regardless of the ascent rate
used.
Tending Frequency. Normally, tenders should allow a surface interval of at least
12 hours between consecutive treatments on Tables 1A, 2A, 3, 5, 6, and 6A, and at
least 48 hours between consecutive treatments on Tables 4, 7, and 8. If necessary,
however, tenders may repeat Treatment Tables 5, 6, or 6A within this 12-hour
surface interval if oxygen is breathed at 30 feet and shallower as outlined above.
Minimum surface intervals for Tables 1A, 2A, 3, 4, and 7 shall be strictly
observed.
Loss of Oxygen During Treatment. Loss of oxygen-breathing capability during
oxygen treatments is a rare occurrence. However, should this occur, the following
should be done:
If repair can be effected within 15 minutes:
Maintain
depth until repair completed.
After O2 is restored, resume
treatment at point of interruption.
If repair can be effected after 15 minutes but before 2
hours:
Maintain depth until repair
completed
After O2 is restored: If
original table was Table 5, 6, or 6A, complete treatment on Table 6 schedule
with maximum number of O2 extensions.
Compensation. If Table 4, 7, or 8 is being used, no compensation in decompression
is needed if O2 lost. If decompression must be stopped because of worsening
symptoms in the affected diver, then stop decompression. When oxygen is
restored, continue treatment from where it was stopped.
Switching to Air Treatment Table. If O2 breathing cannot be restored in 2 hours
switch to comparable air Treatment Table at current depth for decompression if 60 fsw or shallower. Rate of ascent must not exceed 1 fpm between stops. If an
increase in treatment depth deeper than 60 feet is needed, use Treatment Table 4.
Use of High-Oxygen Mixes. High-oxygen N2O2/HeO2 mixtures may be administered
during treatment when 100 percent oxygen cannot be tolerated. The
premixed gases shown in Table 21-5 may be used over the depth range of 0-225 fsw.
High-oxygen mixtures can be used for treating patients at depth when no significant
improvement was made at 60 fsw. High-oxygen mixtures may also be used
for patients experiencing pulmonary oxygen toxicity at 60 fsw and shallower.
Ideally, the ppO2 of the treatment gas used should be 1.5 to 2.8 ata. Using nitrogen
as the background gas is an acceptable practice for treating DCS/AGE. Recent
studies suggest that using helium as the background gas may be more beneficial.
Using HeO2 reduces the amount of nitrogen dissolved in the patient’s tissue and
facilitates the off-gassing of nitrogen.
Treatment at Altitude - Tender Consideration.
Divers serving as inside tenders during hyperbaric treatments at altitude
are performing a dive at altitude and therefore require more decompression
than at sea level. Tenders locking into the chamber for brief periods should
be managed according to the Diving At Altitude procedures (paragraph 9-12).
Tenders remaining in the chamber for the full treatment table must breathe
oxygen during the terminal portion of the treatment to satisfy their
decompression requirement. The additional oxygen breathing required at
altitude on TT5, TT6, and TT6A is given below. The requirement pertains both
to tenders equilibrated at altitude and to tenders flown directly from sea
level to the chamber location. 
