Closed-circuit oxygen diving in the U.S. Navy.
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Diving↗
Biomedical subjects
F K Butler
Publications and source records attributed to F K Butler.
Tactical medicine training for SEAL mission commanders.
The Tactical Combat Casualty Care (TCCC) project initiated by the Naval Special Warfare Command and continued by the U.S. Special Operations Command has developed a new set of combat trauma care guidelines that seek to combine good medical care with good small-unit tactics. The principles of care recommended in TCCC have gained increasing acceptance throughout the Department of Defense in the 4 years since their publication, and increasing numbers of combat medical personnel and military physicians have been trained in this concept. Because casualty scenarios in small-unit operations typically present tactical as well as medical problems, however, it has become apparent that a customized version of this course suitable for small-unit mission commanders is a necessary addition to the program. This paper describes the development of a course in tactical medicine for SEAL mission commanders and its transition into use in the Naval Special Warfare community.
Curriculum↗
Orbital hemorrhage following face-mask barotrauma.
A 41-yr-old female recreational diver suffered an orbital hemorrhage following face-mask barotrauma This case illustrates the potential for significant orbital injury to occur as a result of face-mask barotrauma Barotraumatic orbital hemorrhage is an unusual disorder, but recognition of this entity is important for diving physicians. The signs and symptoms should not be mistaken for decompression sickness or arterial gas embolism. Patients with barotraumatic orbital hemorrhage require emergency referral to an ophthalmologist so that potentially vision-threatening ocular complications may be identified and treated. Barotrauma may result in several different types of cranial neuropathies and should be recognized as another possible cause for neurologic deficits following a dive.
Adult↗
The U.S. Navy decompression computer.
The U.S. Navy has recently approved the Cochran NAVY decompression computer (DC) for use in Naval Special Warfare diving. This action represents the first approval of a diver-worn DC for use in the U.S. Navy. This paper reviews the development and testing of both the decompression algorithm and the hardware chosen for the Navy's DC. The decompression software in the Cochran NAVY is the VVAL 18 algorithm developed at the Navy Experimental Diving Unit (NEDU) by Captain Ed Thalmann. A discussion of the relative conservatism of the VVAL18 algorithm in comparison to the U.S. Navy Standard Air Tables and the basis for the differences between the two is provided. The initial guidelines establishing DC diving practice for the Navy SEAL community are outlined as are plans for future research efforts in U.S. Navy DC diving.
Algorithms↗
Tactical management of urban warfare casualties in special operations.
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Accidents, Aviation↗
Screening for oxygen sensitivity in U.S. Navy combat swimmers.
The United States Naval Special Warfare Community uses oxygen tolerance testing to screen Navy combat swimmer candidates for sensitivity to the toxic effects of hyperbaric oxygen (HBO2). Between 1976 and 1997, 6,250 oxygen-tolerance tests were performed at the Naval Special Warfare Center and Naval Special Warfare Group One. Our review of these data found only six episodes of O2 toxicity for an incidence of 0.096%, an incidence considerably lower than the rate of 1.9% reported in an earlier review using data from the Naval Safety Center. Additionally, we reviewed data from the Naval Safety Center from 1986 to 1997 and found only one episode of O2 toxicity among 157,930 LAR V dives. Many factors other than individual sensitivity to HBO2 may contribute to the occurrence of O2 toxicity episodes during combat swimmer operations. The authors conclude that O2 tolerance testing of U. S. Navy SEAL candidates is not a useful screening test and recommend discontinuation of this test.
Diving↗
The eye at altitude.
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Aerospace Medicine↗
Hyperoxic myopia in a closed-circuit mixed-gas scuba diver.
A myopic shift occurred in a closed-circuit mixed-gas scuba diver using a 1.3 atm abs constant partial pressure of oxygen in a nitrogen-oxygen mix. This change was noticed after approximately 18 days of diving with a mean dive time of 4.04 h each day. The observed myopic shift was due to hyperoxic myopia, one sign of lenticular oxygen toxicity, and resolved over a 1 mo. period after diving was completed. On a subsequent drive trip, a myopic shift was found in both the index diver as well as two other divers breathing the same gasmix on similar profiles. Diving communities should be aware of the risk of both lenticular and pulmonary oxygen toxicity when conducting intensive diving at oxygen partial pressures in the 1.3-1.6 atm abs range.
Atmospheric Pressure↗
Infraorbital hypesthesia after maxillary sinus barotrauma.
We report a case of a diver who suffered an episode of maxillary sinus barotrauma that presented with decreased sensation over the cutaneous distribution of the infraorbital nerve after an ascent which produced facial pain and crepitus. This case illustrates a potential confusion between a decompression sickness etiology and a barotraumatic etiology for the observed sensory deficit. The clinical features of this case were most consistent with a barotraumatic etiology for the findings noted. The anatomy of the trigeminal nerve and previous reports of cranial nerve deficits following barotrauma are reviewed.
Barotrauma↗
Tactical combat casualty care in special operations.
U.S military medical personnel are currently trained to care for combat casualties using the principles taught in the Advanced Trauma Life Support (ATLS) course. The appropriateness of many of the measures taught in ATLS for the combat setting is unproven. A 2-year study to review this issue has been sponsored by the United States Special Operations Command. This paper presents the results of that study. We will review some of the factors that must be considered in caring for wounded patients on the battlefield with an emphasis on the Special Operations environment. A basic management protocol is proposed that organizes combat casualty care into three phases and suggests appropriate measures for each phase. A scenario-based approach is needed to plan in more detail for casualties on specific Special Operations missions, and several sample scenarios are presented and discussed.
Airway Obstruction↗
Preliminary results of photorefractive keratectomy in active-duty United States Navy personnel.
PURPOSE: To evaluate the safety, efficacy, and quality of vision after photorefractive keratectomy (PRK) in active-duty military personnel. METHODS: Photorefractive keratectomy (6.0-mm ablation zone) was performed on 30 navy/marine personnel(-2.00 to -5.50 diopters [D]; mean, -3.35 D). Glare disability was assessed with a patient questionnaire and measurements of intraocular light scatter and near contrast acuity with glare. RESULTS: At 1 year, all 30 patients had 20/20 or better uncorrected visual acuity with no loss of best-corrected vision. By cycloplegic refraction, 53% (16/30) of patients were within +/- 0.50 D of emmetropia and 87% (26/30) were within +/- 1.00 D. The refraction (mean +/- standard deviation) was +0.45 +/- 0.56 D (range, -1.00 to 1.63 D). Four patients (13%) had an overcorrection of more than 1 D. Glare testing in the early (1 month) postoperative period demonstrated increased intraocular light scatter (P<0.01) and reduced contrast acuity (with and without glare, (P<0.01). These glare measurements statistically returned to preoperative levels by 3 months (undilated) and 12 months (dilated) postoperatively. Two patients reported moderate to severe visual symptoms (glare, halo, night vision) worsened by PRK. One patient had a decrease in the quality of night vision severe enough to decline treatment in the fellow eye. Intraocular light scatter was increased significantly (>2S D) in this patient after the procedure. CONCLUSIONS: Photorefractive keratectomy reduced myopia and improved the uncorrected vision acuity of all patients in this study. Refinement of the ablation algorithm is needed to decrease the incidence of hyperopia. Glare disability appears to be a transient event after PRK. However, a prolonged reduction in the quality of vision at night was observed in one patient and requires further study.
Adult↗
Altitude retinopathy on Mount Everest, 1989.
The authors studied prospectively the incidence of and risk factors for high altitude retinal hemorrhages among 14 members of the 1989 American Everest Expedition. All subjects had comprehensive eye examinations and fundus photography performed at sea level before the expedition and again at the Mt. Everest Base Camp after 6 weeks of exposure to altitudes between 5300 and 8200 meters. Asymptomatic intraretinal hemorrhages were found in five eyes of four climbers. An additional eye of one of these climbers had a central retinal vein occlusion with vitreous hemorrhage, which reduced visual acuity to counting fingers. Higher baseline intraocular pressure and use of nonsteroidal anti-inflammatory drugs were found to be significant risk factors for development of altitude retinopathy.
Acclimatization↗
Decompression sickness presenting as optic neuropathy.
Decompression sickness (DCS) is a systemic disorder caused by an abrupt decrease in the ambient atmospheric pressure to which an individual is exposed. A previously healthy 23-year-old male parachutist developed optic neuropathy after a series of multiple repeated hypobaric exposures; his symptoms improved promptly with recompression and hyperbaric oxygen therapy. We believe this to be the first reported case of DCS presenting as optic neuropathy.
Adult↗
Visual reaction time performance preceding CNS oxygen toxicity.
The visual reaction time performance of divers experiencing CNS oxygen toxicity was assessed during the development of closed-circuit 100% oxygen breathing diving schedules at the U.S. Navy Experimental Diving Unit. Divers repeatedly performed the visual reaction time test of the Performance Measurement System (PMS) during multiple excursion dives. Each diver wore a Draeger LAR V UBA and performed moderate work on an underwater bicycle ergometer while engaged in the reaction time test. A single subject, repeated measures design was used. Six divers experienced 7 episodes of CNS oxygen toxicity while engaged in the visual reaction time test. Two episodes were preceded by a slowing and increase in variability of reaction time. Five episodes were not preceded by changes in reaction time performance. Other objective and subjective symptoms of toxicity experienced by the divers did not appear to be correlated with reaction time performance. Thus, the PMS visual reaction time test was not reliable method of detecting CNS oxygen toxicity in this study.
Adult↗
Progressive ulnar palsy as a late complication of decompression sickness.
We report an unusual case of decompression sickness in which a progressive ulnar palsy developed 22 days after the onset of neurological decompression sickness. The initial symptoms of numbness and paresthesias of the hand were treated with recompression therapy, resulting in only partial relief. The patient subsequently developed weakness of the left hand, which increased in severity until the institution of repeated daily hyperbaric oxygen treatments. A total of seven treatments resulted in partial resolution of the patient's signs and symptoms. Recovery was complete within four months.
Adult↗
The application of positron emission tomography to the study of panic disorder.
Positron emission tomography was used to study eight patients with panic disorder who were vulnerable to lactate-induced panic, eight patients with panic disorder who were not vulnerable to lactate-induced panic, and 25 normal control subjects. Patients who were vulnerable to lactate-induced panic had several abnormalities in the resting, nonpanic state: an abnormal hemispheric asymmetry of parahippocampal blood flow, blood volume, and oxygen metabolism; abnormally high whole brain metabolism; and abnormal susceptibility to episodic hyperventilation. A hypothetical model for the neurobiology of panic disorder, involving the abnormal parahippocampal region and its afferent and efferent connections, is proposed.
Adult↗
Screening for oxygen intolerance in U.S. Navy divers.
All U.S. Navy diving candidates are screened for their tolerance to hyperbaric oxygen by taking an oxygen tolerance test (OTT). During a recent experimental oxygen dive series at the U.S. Navy Experimental Diving Unit, three divers were noted to be reproducibly oxygen sensitive. These three divers were then given additional OTTs to see if any evidence of central nervous system oxygen toxicity would be detected by these multiple tests. The additional OTTs did not produce any signs or symptoms of oxygen toxicity in these already proven susceptible divers. A subsequent review of the records of the Naval Safety Center yielded a total of 1347 OTTs from 1 January 1972 to 31 December 1981. A review of diving accidents reported during this period revealed that 26 episodes of oxygen toxicity were noted during OTTs for a derived failure rate of 1.9%. Analysis of oxygen toxicity episodes encountered during operational Navy diving for this period found that 9 episodes of nonconvulsive oxygen toxicity were seen in mixed gas diving and 3 episodes of nonconvulsive oxygen toxicity were noted in closed circuit oxygen diving. Conclusions from this paper are: Screening for oxygen intolerance is complicated by intraindividual variation in oxygen tolerance; U.S. Navy diving using 100% oxygen during the period studied has had an acceptable safety record according to the data on record at the Naval Safety Center; the OTT as currently administered by the U.S. Navy does not identify all individuals who are relatively susceptible to oxygen toxicity; those individuals who do fail the OTT are unusually susceptible to oxygen toxicity; and because of the need to continue to identify these unusually susceptible individuals, the OTT should continue to be administered to U.S. Navy diver candidates.
Adult↗
A blitz of bends: decompression sickness in four students after hypobaric chamber training.
This paper reports three cases of type II and one case of type I decompression sickness occurring in a group of nine vigorously active US Army parachutists who took a hypobaric chamber HALO (high altitude-low opening) training flight to a maximum altitude of 9,908.5 m (32,500 ft). After the cases of decompression sickness were diagnosed and treated, the aviator mask regulators were checked and found to be functioning properly; the oxygen supply was analyzed and found to be pure. All cases fully recovered after treatment on US Navy Diving Table 6 and have returned to full military duty. This HALO training profile is not in use with either the US Navy or the US Air Force and should probably be considered unsafe for future use in training.
Adult↗