Propranolol's potential to increase survival time in a disabled submarine.
BACKGROUND
While awaiting rescue from a disabled submarine, survivors will likely endure an atmosphere of rising CO2 that will result in CO2 toxicity once the available emergency CO2 scrubbing materials are exhausted. Propranolol is a beta-blocker that may increase survival time by reducing metabolic CO2 production (VCO2). The purpose of this study was to determine if propranolol reduces resting VCO2 in healthy men.


METHODS
Eight healthy men completed a counterbalanced, randomized, placebo-controlled, double-blinded crossover study in which each subject received propranolol (40 mg twice daily) or placebo (lactose pill twice daily) over 72 h. The alternate condition was separated by a minimum 96-h washout period. Resting VCO2, oxygen consumption (VO2), ventilation (VE), respiration rate (RR), respiratory exchange ratio (RER), mean arterial pressure (MAP), heart rate (HR), and cardiac output (Q) were measured each morning and afternoon.


RESULTS
When compared to placebo, propranolol significantly reduced VCO2 (-6.5%), MAP (-3.6%), HR (-10.4%), and Q (-8.2%); however, there were no significant differences in VO2, RR, VE, or RER.


CONCLUSIONS
These results show that 40 mg of propranolol taken twice daily reduces resting VCO2 in healthy men and suggests that this treatment strategy may increase survival time in a disabled submarine scenario.
Naval Submarine Medical Research Laboratory, Groton, CT, USA. seth.reini@med.navy.mil
Seth A
SA
Reini
David M
DM
Fothergill
Heath G
HG
Gasier
Wayne G
WG
Horn
D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D002245:Carbon Dioxide / Q000378:metabolism*; D002302:Cardiac Output / Q000187:drug effects / Q000502:physiology; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008889:Military Personnel; D009326:Naval Medicine; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011433:Propranolol / Q000627:therapeutic use*; D011659:Pulmonary Gas Exchange / Q000187:drug effects / Q000502:physiology; D012123:Pulmonary Ventilation / Q000187:drug effects / Q000502:physiology; D056152:Respiratory Rate / Q000187:drug effects / Q000502:physiology; D012767:Ships
D000319:Adrenergic beta-Antagonists; D002245:Carbon Dioxide; D011433:Propranolol