1. DISCLOSURES
BREATH-HOLDING –
This presentation contains discussion of commercial
PHYSIOLOGY, HAZARDS AND 
products and services
COMMUNITY EDUCATION  The speaker has no financial conflicts to disclose
Neal W. Pollock, Ph.D.
Divers Alert Network and
Center for Hyperbaric Medicine and Environmental Physiology
Duke University Medical Center
Durham, NC
National Drowning Prevention Symposium
Fort Lauderdale, FL – March 2013
neal.pollock@duke.edu
N.W. Pollock, Ph.D.
BREATH-HOLD ACTIVITIES AIDA COMPETITIVE BH DISCIPLINES
 Recreational  Static
– resting immersion in controlled water
– play, personal challenge, exploration
 Dynamic
 Competitive – horizontal swim in controlled water (with/without fins)
– underwater hockey, underwater rugby  No Limits
– spearfishing – descent on weighted sled; ascent on lift bag
– freediving  Variable Weight/Ballast
 International Association for the Development of Apnea (AIDA) – descent on weighted sled; ascent pulling up line with kick
» www.aida-international.org
 Constant Weight/Ballast
– vertical self-propelled swimming to max depth and back;
no line assistance (with/without fins)
 Free Immersion
– vertical excursion propelled by pulling on the rope during
descent and ascent; no fins
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D. International Association for the Development of Apnea
APNEA WORLD RECORDS INTERNATIONAL LIFE SAVING FEDERATION
Medical Position Statement – MPS 16
Category Male Female 'Shallow Water Blackout'
Static (min:s) - air (min:s) 11:35 8:23
 Key Points (ILS , 2011)
Static (min:s) - oxygen (min:s)* 22:22
– blackout is caused by excessive hyperventilation (HV)
Dynamic - with fins (ft [m]) 896 (273)1 738 (225)1 – other causes of 'unexplained sudden death' exist
Dynamic - no fins (ft [m]) 715 (218)1 535 (163)1  e.g., swimming exhaustion, seizure, trauma
No Limits (ft [m]) 702 (214) 525 (160)  not listed – sudden cardiac death
Variable Weight (max 35 kg) (ft[m]) 466 (142) 417 (127)  ambiguous – 'diving response,' 'cold shock response'
Constant Weight - with fins (ft[m]) 413 (126) 331 (101) – "prevention is better than cure"
Constant Weight - no fins (ft[m]) 331 (101) 220 (67)  Outstanding Issues
Free Immersion (ft[m]) 397 (121) 289 (88) – confusing terminology
* not AIDA-approved event 1 horizontal swim
N.W. Pollock, Ph.D.
latest update 03/08/13 N.W. Pollock, Ph.D.

2. 90 90
80 Non-Fatal 80 Non-Fatal
70 Fatal 70 Fatal
60 60
Number Number
50 of 50
of
Cases 40 Cases 40
30 30
20 20
10 10
0
0
2004 2005 2006 2007 2008 2009 2010 2011 2012
2004 2005 2006 2007 2008 2009 2010 2011 2012
Year
Year
DAN breath-hold incident case intake: 565 (433 fatal) events DAN breath-hold incident case intake: 565 (433 fatal) events
(01/2004 through 12/2012) (01/2004 through 12/2012)
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
TOP CONCERNS CASE REPORT - 250802
 Hyperventilation-Induced Blackout
 Inadequate Support
 A 14-year-old male was spearfishing with two friends
off a boat anchored in 65 fsw (20 msw). He was
 Medical Health
observed to develop difficulties while nearing the
 Entanglement surface on his ascent and began to sink back down in the
Overrepresented due water. He did not release his weight belt. His
 Animal Interaction
to physical evidence?
 Boat Interaction
companions dived into the water but were unable to
 Pollock et al. (2007; 2008) reach him. A scuba diver later recovered the victim's
body from ~65 fsw (20 msw).
 Problem: hypoxia of ascent?
 Contributing factors: overweighting, inadequate support.
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
MANAGING RISK MANAGING RISK OF BREATH-HOLD
 Ignore  Ignore?
– will inevitably lead to failures – should not - risk long recognized
 Prohibition – Craig (1961a&b)
– requires voluntary compliance and/or enforcement  Prohibition?
– victims will be less prepared for problems – extremely difficult to enforce and probably not valid
breath-hold is part of every respiratory cycle
 Engineering 
– change tools to reduce likelihood and/or magnitude of risk  Engineering
 Education – possible for some equipment
– procedural engineering important for all dives
– greatest flexibility; provide protection for a lifetime
 Education
– best defense
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.

3. Start of breath-hold PRESSURE-VOLUME RELATIONS
100 PCO2 - no HV 100
Depth Pressure Volume Density
80 PCO2 - HV 80 (fsw/msw) (atm) (lbs·in-2) (kPa)
0/0 1 14.7 101.3 1 1x
PCO2 60 60 PO2
urge to breathe (mm Hg) 33 / 10 2 29.4 202.6 1/2 2x
(mm Hg)
40 minimum O2 for 40 66 / 20 3 44.1 303.9 1/3 3x
consciousness 99 / 30 4 58.8 405.2 1/4 4x
20 20 132 / 40 5 73.5 506.5 1/5 5x
PO2
0 0
Time
 Pressure-volumes relationship critical for understanding
the physiological impact of diving
The respiratory drive is highly protective. Pre-breath-hold hyperventilation
increases the risk of hypoxic loss of consciousness (HLOC) by delaying the
urge to breathe. The example above depicts a static breath-hold condition.
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
Start of breath-hold HYPERVENTILATION RISKS
100 100
 Loss of consciousness without warning
descent-ascent – at or near the bottom
80 80
 Apneic Hypoxia ('hypoxic blackout' or 'hypoxic LOC')
PCO2 60 PO2 – likely requires substantial hyperventilation
PCO2 - HV 60
(mm Hg) » Pollock (2008)
(mm Hg)
40 40 – at or near the surface during ascent
descent-ascent  Hypoxia of Ascent (HOA) ('shallow water blackout')
20 20 – requires less hyperventilation for high risk
PO2  Major concern is ostrich mentality
0 0 – i.e., 'renaming' hyperventilation
Time (Vertical Excursion Dive)  e.g., 'work up breathing,' 'breathe up'
Pre-breath-hold hyperventilation increases the risk of hypoxic loss of  How much hyperventilation is too much?
consciousness (HLOC) by delaying the urge to breathe. Decreased ambient – 3-4 maximal ventilatory exchanges is probably safe
pressure during ascent increases the risk (hypoxia of ascent). * Illustration.
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
RESPIRATORY MANIPULATIONS AGGRESSIVE GI AND GE
 Glossopharyngeal Insufflation (GI)  Glossopharyngeal Insufflation (GI)
– aka 'lung packing,' 'air packing' or 'buccal pumping' –  blood pressure
– can add >3 L over normal total lung capacity –  heart rate, dizziness, tunnel vision
 Glossopharyngeal Exsufflation (GE) – blackout, pulmonary barotrauma
– aka 'reverse packing' – Simpson et al. (2003), Jacobson et al. (2006), Loring et al. (2007)
– ~0.2-0.4 L below RV  Glossopharyngeal Exsufflation (GE), 10-20 ft (3-6 m) dives
– enables deep equalization – reversible changes in voice
– simulate deep dive effects – reversible reduction in pulmonary diffusing capacity
– Lindholm et al. (2008)
– irritation and slight congestion in the larynx
– bleeding originating somewhere below the vocal folds
– Lindholm et al. (2008)
From Lindholm, (2006)
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.

4. Glossopharyngeal insufflation (GI; lung packing) prior to dynamic Loss of motor control (LMC) following dynamic pool trial.
pool trial.
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
BREATH-HOLD IMPAIRMENT OPTIMIZING RISK MANAGEMENT
 'Mooglies'  Must understand two key factors
– language production disturbances – risk tolerance is personal
– Ridgway et al. (2006) – personal judgment is subject to 'optimism bias'
 'Samba' Perceived Benefit
– loss of motor control (LMC)
– may include confusion, affected postural control, spasms Acceptable
– Ridgway et al. (2006), Lindholm (2007) Risk
 Blackout Injury Severity
– loss of consciousness (LOC)
– often with no meaningful warning Increasing →
 Relatively few serious incidents in competition  Messaging should accentuate positive reinforcement
– Fitz-Clarke (2006)
– e.g., "do this to be safer" vs. "do this or get hurt"
– likely due to strict disqualification rules and close support
N.W. Pollock, Ph.D.
N.W. Pollock, Ph.D.
BREATH-HOLD SAFETY PROTOCOLS FREEDIVER RECOVERY VEST
Should be applied to self, partner(s) and guarded groups (http://www.oceanicss.com)
 Limit/Control Hyperventilation  Automatic deployment
– equivalent to 1-3 full ventilatory exchanges – user sets maximum time and/or depth
 Defensive Weighting
– neutral buoyancy at 15 fsw (4.5 msw) or deeper
 i.e., so positively buoyant when shallower
 Direct Supervision
– pre- through full 30 s post-dive; ready to protect airway
 Ensure adequate recovery time
– minimum 2:1 surface interval
 Automatic Surfacing Devices
– note: manually-deployed systems not adequate
Photos courtesy
N.W. Pollock, Ph.D. Terry Maas

5. BREATH-HOLD SAFETY PROTOCOLS
 Support Network
– progressive options as appropriate for activities
 buddy system – one-up-one-down
– trio better – one up fresh, one up recovering, one down
 close support surfacing
 surface safety weight systems
 in-water divers
Competitive freediving
descent-ascent profile
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
Surface counter-weight
system deployed to rapidly
lift diver to surface
N.W. Pollock, Ph.D.
BREATH-HOLD SAFETY PROTOCOLS DAN ONLINE INCIDENT REPORTING
 Catch Care  New online system will focus on non-fatal events
– avoid carrying catch on body – facilitating collection of complete case data (Pollock, 2006)
– line caution http://DAN.org/IncidentReport
 Surface Markers
– floats and flags
– bright-colored suits
 Dive Locations
– avoid boat traffic
 Avoid After Compressed Gas Diving
– minimize strain/decompression risk
 Training
– initial and continuing education
– report cases
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.

6. BREATH-HOLDING SAFETY SUMMARY BREATH-HOLDING SAFETY KEY TERMS
 Breath-hold is not the safety hazard  Breath-hold
– excessive hyperventilation is the prime hazard – part of every respiratory cycle; not inherently unsafe
– inadequate support is the second major hazard  Hyperventilation
 Risks are best managed through education and awareness – ventilation in excess of metabolic need
– swimmers, divers, instructors, lifeguards – excessive hyperventilation >3-4 full ventilatory exchanges
 Foster a culture of safety  Apneic Hypoxia
– focus on positive benefits of safety – LOC resulting from excessive HV and little vertical travel
– encourage or build appropriate peer groups  Hypoxia of Ascent
 Incident management – LOC/IMC due to excessive HV compounded by vertical
– airway protection is top priority travel
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
REFERENCES - 1 REFERENCES - 2
 Craig AB Jr. Causes of loss of consciousness during underwater  Lindholm P, Ekborn A, Oberg D, Gennser M. Pulmonary edema and
swimming. J Appl Physiol. 1961; 16(4): 583-6. hemoptysis after breath-hold diving at residual volume. J Appl Physiol
 Craig AB Jr. Underwater swimming and loss of consciousness. JAMA. 2008; 104(4): 912-7.
1961; 176(4): 255-8.  Loring SH, O'Donnell CR, Butler JP, Lindholm P, Jacobson F, Ferrigno
 Fitz-Clarke JR. Adverse events in competitive breath-hold diving. M. Transpulmonary pressures and lung mechanics with glossopharyngeal
Undersea Hyperb Med. 2006; 33(1): 55-62. insufflation and exsufflation beyond normal lung volumes in competitive
 International Life Saving Federation Medical Position Statement – MPS- breath-hold divers. J Appl Physiol. 2007; 102: 841-6.
16 Shallow Water Blackout. 2011; 4 pp.  Pollock NW. Breath-hold diving: performance and safety. Diving Hyperb
 Jacobson FL, Loring SH, Ferrigno M. Pneumomediastinum after lung Med. 2008; 38(2): 18-25.
packing. Undersea Hyperb Med. 2006; 33(5): 313-6.  Pollock NW. Development of the DAN breath-hold incident database. In:
 Lindholm P. Glossopharyngeal breathing and breath-hold diving on Lindholm P, Pollock NW, Lundgren CEG, eds. Breath-hold diving.
empty lungs. In: Lindholm P, Pollock NW, Lundgren CEG, eds. Breath- Proceedings of the Undersea Hyperbaric Medical Society/Divers Alert
hold diving. Proceedings of the Undersea Hyperbaric Medical Network 2006 June 20-21 Workshop. Durham, NC: Divers Alert
Society/Divers Alert Network 2006 June 20-21 Workshop. Durham, NC: Network; 2006: 46-55.
Divers Alert Network; 2006: 96-101.  Pollock NW, Dunford RG, Denoble PJ, Dovenbarger JA, Caruso JL.
 Lindholm P. Loss of motor control and/or loss of consciousness during Annual Diving Report - 2008 Edition. Durham, NC: Divers Alert
breath-hold competitions. Int J Sports Med 2007; 28(4): 295-99. Network, 2008; 139 pp.
N.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
REFERENCES - 3
 Pollock NW, Vann RD, Denoble PJ, Freiberger JJ, Dovenbarger JA,
Nord DA, McCafferty MC, Caruso JL. Annual Diving Report - 2007
Edition. Durham, NC: Divers Alert Network, 2007; 118 pp.
 Ridgway L, McFarland K, Stewart IB, Bulmer AC. 'Sambas', 'Mooglies'
and other acute effects of apnea. In: Lindholm P, Pollock NW, Lundgren
CEG, eds. Breath-hold diving. Proceedings of the Undersea Hyperbaric
Medical Society/Divers Alert Network 2006 June 20-21 Workshop.
Durham, NC: Divers Alert Network; 2006: 39-45.
 Simpson G, Ferns J, Murat S. Pulmonary effects of 'lung packing' by
buccal pumping in an elite breath-hold diver. SPUMS J. 2003; 33: 122-6.
Divers Alert Network
Durham, NC
http://www.diversalertnetwork.org
neal.pollock@duke.edu
N.W. Pollock, Ph.D.