Breath Holding - Physiology, Hazards & Community Education by Neal W. Pollock, Ph.D
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 firstname.lastname@example.org 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 finsN.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 swimN.W. Pollock, Ph.D. latest update 03/08/13 N.W. Pollock, Ph.D.
90 90 80 Non-Fatal 80 Non-Fatal 70 Fatal 70 Fatal 60 60Number 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 victims 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 defenseN.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
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.
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 supportN.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 courtesyN.W. Pollock, Ph.D. Terry Maas
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 profileN.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 casesN.W. Pollock, Ph.D. N.W. Pollock, Ph.D.
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 travelN.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, ODonnell 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 email@example.comN.W. Pollock, Ph.D.