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Gender Differences in Diving?
Basically, there are no differences between women and men in diving. However, there are some hormonal and child-bearing differences between men and women that are addressed in some of the articles abstracted below.

Without entering into a debate on these matters, we will present to you the pertinent references that we can find about certain factors that might be important to women divers.

Women in the fast jet cockpit--aeromedical considerations.
Lyons TJ
Aviat Space Environ Med 1992 Sep;63(9):809-18
Armstrong Laboratory, Brooks AFB, TX 78235.

Historically, women have demonstrated the capacity to be successful aviators. A review of the scientific literature between 1966 and 1991 pertinent to the role of women in military aviation revealed only minor differences of questionable operational significance between men and women. Women may be more susceptible to motion sickness, radiation, and decompression sickness than men, but may be more resistant to cold water immersion and altitude sickness. Although men are on the average, larger, stronger, and more aerobically fit than women, there are large variations within each sex and a large overlap between the sexes. Gender differences in work performance, G tolerance, heat stress, and injury rate disappear when allowance is made for size, strength, and fitness. Aeromedical selection criteria can, thus, address individual characteristics without reference to gender. The possibility of fetal damage in the early stages of pregnancy (before diagnosis) appears to be perhaps the biggest single medical concern in allowing women access to all aviation and space careers.

Decompression Sickness in Women Divers
Zwingelberg KM; Knight MA; Biles JB
Undersea Biomed Res 1987 Jul;14(4):311-7 
The comparative incidence of DCS in women has been debated for years. Diving log data from the Naval Diving and Salvage Training Center (NDSTC), Panama City, FL, demonstrate that there is no increased risk of DCS among Navy female divers compared to their male counterparts. Twenty-eight female students were compared to their 487 male classmates on 878 air and helium-oxygen dives between 4.64 and 10.10 ATA (120 to 300 fsw). None of the women experienced DCS while 8 men developed DCS symptoms. The total duration of the dives ranged from 8 min to 2 h and 6 min; bottom times were less than 20 min. Theoretical inert gas supersaturation on these profiles are commensurate with those experienced on 40- to 60-min sport scuba dives.

Semin Perinatol 1996 Aug;20(4):292-302
Diving and pregnancy.
Camporesi EM
Department of Anesthesiology, Hyperbaric Center, SUNY Health Science Center, Syracuse 13210, USA.

Scuba diving during pregnancy has increased in incidence as a result of substantial growth in the number of young females attracted to sport diving. This review summarizes the physiological changes induced by immersion, diving and decompression, on male and female divers. Furthermore, it extends to literature review, in animal models, of the susceptibility of a pregnant animal to diving decompression injury. Publications regarding reports of diving injury in pregnant humans are also reviewed, comprising very recent material from the sport diving community. It is concluded that there is no countraindication to diving for the normal, healthy, nonpregnant female. However, pregnant females should refrain from diving, because the fetus is not protected from decompression problems and is at risk of malformation and gas embolism after decompression disease. It is prudent to advise pregnant patients of the increased risk of diving problems for the fetus during pregnancy. However, should a woman have completed a dive during early pregnancy because she was unaware she was pregnant, the present evidence is not to recommend an abortion, because several normal pregnancies have been documented even if diving is continued. Snorkeling can still be practiced during pregnancy, but scuba diving should be discontinued until after the birth period.

Undersea Biomed Res 1980 Sep;7(3):183-9 
Scuba diving and fetal well-being: a survey of 208 women.
Bolton ME

Scuba diving is an increasingly popular sport among women of childbearing age. It causes physiological changes that are possibly lethal or teratogenic to the fetus. The subject of diving during pregnancy is seldom mentioned in diving courses, however, and few obstetricians are familiar with the physiology of diving. The study employed mailed questionnaires for description and comparison of the extent of diving and obstetric and fetal outcome of 208 women divers, 136 of whom dived during one or more pregnancies. Depths to which these women dived averaged 42.6 ft; 24 women, however, reported dives deeper than 99 ft during the first trimester. I analyzed the prevalence of six specific fetal complications and found that the frequency of birth defects was significantly greater among children from pregnancies during which women dived (P < 0.05) but was within the range for the general population.

Should hyperbaric oxygen be used to treat the pregnant patient for acute carbon monoxide poisoning? A case report and literature review.
Van Hoesen KB; Camporesi EM; Moon RE; Hage ML; Piantadosi CA
Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710.
 JAMA 1989 Feb 17;261(7):1039-43
Carbon monoxide (CO) is the leading cause of death due to poisoning. Although uncommon, CO poisoning does occur during pregnancy and can result in fetal mortality and neurological malformations in fetuses who survive to term. Uncertainty arises regarding the use of hyperbaric oxygen (HBO) as a treatment for the pregnant patient because of possible adverse effects on the fetus that could be induced by oxygen at high partial pressures. While the dangers of hyperoxia to the fetus have been demonstrated in animal models, careful review of animal studies and human clinical experience indicates that the short duration of hyperoxic exposure attained during HBO therapy for CO poisoning can be tolerated by the fetus in all stages of pregnancy and reduces the risk of death or deformity to the mother and fetus. A case is presented of acute CO poisoning during pregnancy that was successfully treated with HBO. Recommendations are suggested for the use of HBO during pregnancy. 

Hyperbaric oxygen treatment for carbon monoxide poisoning in pregnancy: a case report.
Brown DB; Mueller GL; Golich FC
92nd Medical Group SAT, Fairchild AFB, WA 99011-5300.
Aviat Space Environ Med 1992 Nov;63(11):1011-4 
Carbon monoxide (CO) poisoning is one of the most common forms of poisoning in the United States. When CO poisoning occurs in the pregnant patient, it is extremely toxic to the mother and fetus in terms of central nervous system disorders and delayed central nervous system sequelae. Controversy exists in treating the pregnant patient with hyperbaric oxygen (HBO) because of the unknown effects of high partial pressures of oxygen on the fetus. HBO therapy is beneficial in CO poisoning because of its effect of first increasing oxygen concentration and causing a shift in the oxygen dissociation curve from the left to the right. Second, by causing a diminished CO interaction with cytochrome oxidase, HBO allows mitochondria to use oxygen more effectively. Third, HBO may reduce lipid peroxidation which may be responsible for neurological deterioration and delayed central nervous system sequelae. Fourth, decreased CO influence through HBO may reduce changes in the myocardium as a result of CO poisoning, if cardiovascular disease is already present. A case study of successful HBO therapy used during pregnancy is presented and effects of CO on the fetus are discussed. 

 Hyperbaric oxygen therapy for the treatment of acute carbon monoxide poisoning in pregnancy. A case report.
Hollander DI; Nagey DA; Welch R; Pupkin M
Department of Obstetrics and Gynecology, University of Maryland Hospital, Baltimore.
J Reprod Med 1987 Aug;32(8):615-7 
ABSTRACT:  Acute carbon monoxide poisoning occurred in pregnancy. An acute treatment plan involving hyperbaric oxygen administration was employed in place of the more traditional passive approaches usually used during pregnancy. This treatment plan may help circumvent the potentially lethal effect of this gas. 

Anaesthesia 1999 Sep;54(9):891-5
Hyperbaric oxygen therapy in the management of severe acute anaemia in a Jehovah's witness.
McLoughlin PL, Cope TM, Harrison JC
Department of Anasthesia, University Hospital Aintree NHS Trust, Lower Lane, Liverpool L9 7AL, UK.
A case is described in which a Jehovah's Witness patient who refused blood transfusion suffered massive antepartum haemorrhage, her haemoglobin falling as low as 2.0 g.dl(-1). She was treated on an intensive care unit with intermittent positive pressure ventilation and general supportive measures, pulsed hyperbaric oxygen therapy and recombinant human erythropoietin.

: J Reprod Med 1997 May;42(5):309-11 Related Articles, Books, LinkOut

Hyperbaric oxygen treatment during pregnancy in acute carbon monoxide poisoning. A case report.
Silverman RK, Montano J
Department of Obstetrics and Gynecology, State University of New York, Syracuse 13210, USA.
BACKGROUND: Carbon monoxide poisoning in pregnancy is a relatively rare occurrence, with potentially serious complications for both mother and fetus. Controversy regarding treatment during pregnancy exists primarily due to the concern for oxygen toxicity in the fetus. However, rapid oxygen dissociation and prolonged clearance of carbon monoxide in the fetal circulation emphasize the importance of adhering to aggressive treatment protocols. CASE: A 22-year-old employee at an office undergoing repairs on the heating and ventilation systems presented with neurologic symptoms, tachycardia, tachypnea, signs of preterm labor and a carboxyhemoglobin level that was mildly elevated. Fetal monitoring demonstrated a reactive nonstress test with mild to moderate repetitive variable decelerations. The patient underwent hyperbaric oxygen treatment, with complete resolution of her neurologic symptoms, tachycardia and tachypnea as well as fetal variable decelerations. She was additionally treated with intravenous magnesium sulfate tocolysis, with cessation of contractions. The patient subsequently delivered at term; the viable infant had no sequelae of in utero carbon monoxide poisoning. CONCLUSION: This case supports previously published recommendations for treating acute carbon monoxide poisoning during pregnancy with hyperbaric oxygen. As more cases are gathered, a more widely accepted set of standards can be established.

J Gynecol Obstet Biol Reprod (Paris) 1999 May;28(2):118-23 Related Articles, Books, LinkOut

[Pregnancy and scuba diving: what precautions]?
Morales M, Dumps P, Extermann P
Departement de Gynecologie-Obstetrique, Hopitaux universitaires de Geneve.

Scuba diving is a leisure activity increasingly popular amongst women. Many women are concerned about the risks associated with diving and a known or planned pregnancy. In order to advise these young women, we have reviewed the literature concerning women and diving as well as animal studies on the subject. The different international federations and the Undersea and Hyperbaric Medical Society advise against scuba diving for pregnant women or those planning a pregnancy, but no randomized trials or trials provide a solid scientific basis. The fetal circulation is characterized by the exclusion of the pulmonary circulation by 2 right to left shunts. As the lung appears to act as a filter against the progression of micro-bubbles to the main circulation, the fetus may be therefore particularly exposed to gas emboli. However, the placenta could play this role in certain animal species. Nitrox diving appears to be particularly promising, but studies on the subject are still insufficient to recommend it for pregnant women.

Lakartidningen 1999 Feb 17;96(7):749-53 
[Medical aspects of diving--a sport for both women and men].
Gustavsson LL, Hultcrantz E
Mariakliniken, Stockholm.
As interest in scuba diving is increasing in both sexes, doctors need to be aware of the risks encountered when diving and about gender-related differences in these risks. Individuals prone to panic attacks, claustrophobia or reckless risk-taking should avoid diving. In tolerating cold, muscle mass is more important than the amount of subcutaneous fat. The risk of decompression disease seems to be slightly greater among women, probably due to their fat distribution. Pregnant women are recommended not to dive, because the risk of birth defects seems to be greater among those who do, and there is a serious risk of fetal decompression disease. All participants in the sport must be responsible for their own diving safety.

Ginecol Obstet Mex 1995 May;63:202-4 Related Articles, Books, LinkOut
[Scuba diving and pregnancy. A case report and review of the literature].
Sauceda Gonzalez LF, Gavino Gavino F, Ahued Ahued JR, Hernandez Gonzalez Y
Centro Medico Nacional 20 de Noviembre,
The number of women in childbearing age participating in SCUBA dividing is increasing. Some dives during first trimester before pregnancy is confirmed. The preoccupation of both parents, is that the child could have any damage in the embryonal stage. This is a review of the literature and we present one case of a patient 28 years old with one immersion of 25 meters, at 28 days of gestation. The child did not present any congenital deformity at birth and his growth and development in the eighteen months have been normal.

Aviat Space Environ Med 1987 Apr;58(4):370-4 
Women and the hazardous environment: when the pregnant patient requires hyperbaric oxygen therapy.
Jennings RT

Women are now being exposed in increasing numbers to environmental hazards. Normal operations in that environment plus accidents or training procedures may result in conditions such as decompression sickness, air embolus, hyperoxia, or carbon monoxide poisoning occurring in a woman who also happens to be pregnant. This article examines the animal data and human experience in these conditions in both early and late gestation. The risk of these conditions to the mother and fetus is assessed compared to the problems associated with hyperbaric oxygen therapy (HBO) in pregnancy. Suggestions are made regarding the appropriate use of HBO therapy in pregnancy. Further medical investigation is requested.

Am J Obstet Gynecol 1983 May 1;146(1):48-51
Lack of harmful effects from simulated dives in pregnant sheep.
Bolton-Klug ME, Lehner CE, Lanphier EH, Rankin JH

The purpose of the study was to determine if a near-maximum exposure to air at increased atmospheric pressure causes gross fetal malformations, decreased birth weight, or death when administered to pregnant sheep during peak development of the embryo. Twenty-eight timed-pregnant sheep were alternately assigned to a series of 25- or 30-minute exposures at either 4.6 atmospheres absolute or surface pressure between days 12 and 40 of gestation. About day 130 of pregnancy, 11 experimental and eight control fetuses were recovered, weighed, measured, fixed, and examined for defects. No major structural malformations were present. One minor variation, an undescended testis, occurred in a treated fetus. The results indicate that a series of short, marginally tolerated "dives" by pregnant sheep during peak development does not affect fetal health or survival.

Am J Obstet Gynecol 1981 Jul 15;140(6):651-5
Multiple hyperbaric exposures during pregnancy in sheep.
Nemiroff MJ, Willson JR, Kirschbaum TH

Eleven sheep were subjected to hyperbaric comparable to 165 feet of sea water 31 times between the one hundred twelfth and one hundred thirty-seventh days of pregnancy. During 13 dives the maternal and fetal circulations were monitored for bubble formation during decompression. Bubbles were detected by external doppler probes in eight of 12 ewes, but in none of the fetuses. Nine ewes were delivered of normal lambs at term. In one, twin fetuses died during an abnormal labor. The pregnancy of another was terminated by cesarean section after decompression to look for bubbles in the fetal circulation.

Aviat Space Environ Med 1983 Nov;54(11):1040-2 
Fetal development: effects of decompression sickness and treatment.
Gilman SC, Bradley ME, Greene KM, Fischer GJ

Pregnant hamsters were exposed to 7.1 ATA (200 fsw) of compressed air breathing for 40 min. Comparisons were made between three groups of pregnant hamsters: (a) those that developed decompression sickness (DCS); (b) those that did not; and (c) a control (non-divided) group. As reported previously, maternal DCS if untreated resulted in frequent and severe teratogenic effects. Furthermore, fetuses from those females who apparently did not develop DCS were significantly smaller at term than fetuses from the control animals. However, fetuses from females that were treated for DCS did not differ from controls. This suggests that 40-min, 200-fsw dives per se are detrimental to fetal development in hamsters.

J Appl Physiol 1980 May;48(5):776-80
Responses of fetal sheep to simulated no-decompression dives.
Stock MK, Lanphier EH, Anderson DF, Anderson LC, Phernetton TM, Rankin JH

The effect of simulated standard no-decompression dives to 60 and 100 ft of seawater was tested in 12 near term sheep carrying 16 fetuses. In the immediate postdive period there were no significant changes in fetal blood pressure or fetal placental or renal blood flow, but the maternal blood pressure was elevated and the maternal placental blood flow was depressed. Six surgically prepared fetuses were dived to 100 ft. Five died within 20 min of ascent and the sixth suffered severe cardiac arrhythmia and hypotension. At autopsy all fetuses were observed to have massive bubbling in the arterial system and heart. Five fetuses were dived to 100 ft without surgery. Two were alive 3 h later and no bubbles were present at autopsy, and three were born alive at term. With the 60-ft dives, three fetuses were subjected to surgery and all suffered massive bubbling. Two fetuses were dived to 60 ft without surgery; one was alive after 3 h and the other was born alive at term. We conclude that surgery and monitoring result in the formation of postdive gas bubbles that would not otherwise appear.

Menstruation and Decompression Sickness
Aviat Space Environ Med 1990 Jul;61(7):657-9 
Relationship of menstrual history to altitude chamber decompression sickness.
Rudge FW
Division of Hyperbaric Medicine, United States Air Force School of Aerospace Medicine, Brooks Air Force Base, Texas 78235.

Records at the USAF School of Aerospace Medicine, Division of Hyperbaric Medicine, were reviewed to determine the relationship between the incidence of altitude chamber decompression sickness (DCS) in females and menstrual history. The study period spans 11 years, from January 1978 to December 1988. There were 81 records suitable for study. A significant inverse linear correlation was noted between the number of days since the start of last menstrual period and the incidence of DCS. This relationship was noted with both Type I and Type II DCS. Lack of information on the population at risk precluded an analysis of the effects of birth control pills on this phenomenon. The underlying mechanism for the correlation between menstrual cycle and susceptibility to development of DCS is unknown. We conclude that women are at higher risk of developing altitude related decompression sickness during menses, with the risk decreasing linearly as the time since last menstrual period increases.

Aviat Space Environ Med 1992 Jul;63(7):616-8 
Menstrual history in altitude chamber trainees.
Schirmer JU, Workman WT
Armstrong Laboratory, Hyperbaric Medicine Division, Brooks AFB, TX.

Previous studies have determined a higher rate of altitude-induced decompression sickness (DCS) in women than in men. Women are reportedly at higher risk for developing DCS during menses. A study of menstrual history in women completing altitude chamber training without developing DCS has never been accomplished. The purpose of this study was to collect and analyze menstrual history in these women. Thirteen U.S. Air Force Aerospace Physiology Units participated in a USAF-approved survey for 1 year. After completing altitude chamber flights, data on age, day of menstrual cycle (DMC), birth control pill use (BCP), and mean durations of menstrual cycle and menses were collected. There were 508 responses analyzed. There was no differences between mean duration of menstrual cycle and menses in the Yes (Y) and No (N) BCP groups. Y and N BCP groups were equally distributed across the menstrual cycle. Women completing altitude chamber training without developing DCS appear to be evenly distributed across their menstrual cycle, with use of BCPs not affecting their susceptibility to DCS.

Splenic Contraction
J Appl Physiol 1990 Sep;69(3):932-6
Splenic contraction during breath-hold diving in the Korean ama.
Hurford WE, Hong SK, Park YS, Ahn DW, Shiraki K, Mohri M, Zapol WM
Department of Anesthesia, Massachusetts General Hospital, Boston.

Major increases of hemoglobin concentration and hematocrit, possibly secondary to splenic contraction, have been noted during diving in the Weddell seal. We sought to learn whether this component of the diving response could be present in professional human breath-hold divers. Splenic size was measured ultrasonically before and after repetitive breath-hold dives to approximately 6-m depth in ten Korean ama (diving women) and in three Japanese male divers who did not routinely practice breath-hold diving. Venous hemoglobin concentration and hematocrit were measured in nine of the ama and all Japanese divers. In the ama, splenic length and width were reduced after diving (P = 0.0007 and 0.0005, respectively) and calculated splenic volume decreased 19.5 +/- 8.7% (mean +/- SD, P = 0.0002). Hemoglobin concentration and hematocrit increased 9.5 +/- 5.9% (P = 0.0009) and 10.5 +/- 4% (P = 0.0001), respectively. In Japanese male divers, splenic size and hematocrit were unaffected by repetitive breath-hold diving and hemoglobin concentration increased only slightly over baseline (3.0 +/- 0.6%, P = 0.0198). Splenic contraction and increased hematocrit occur during breath-hold diving in the Korean ama.

Pulmonary c apillary blood volume during lower body negative pressure: effect of gender
Gotshall RW, Davrath LR
Aviat Space Environ Med 1998; 69:277-81
Background: The purpose of this study was to examine the changes in pulmonary capillary blood volume (Vc) in men and women during lower body negative pressure (LBNP). Additionally, the components of lung diffusion capacity were measured and evaluated for the effect of gender and LBNP. Methods: There were 6 men and 6 women who underwent a staged LBNP protocol to -40 mm Hg. The diffusion of the lung for carbon monoxide (DLCO) was separated into the diffusion capacity of the membrane (DLM) and the diffusion capacity of blood. Results: During supine rest, DLCO values for men were larger than for women and were 39.8 ± 3.8 and 32.2 ± 2.2 ml · min-1 · mm-1 Hg, respectfully. DLCO decreased equally with each stage of LBNP for men and women. Vc during supine rest was greater for men (131 ± 8 ml) than for women (92.7 ± 7 ml). Vc also declined with each stage of LBNP, and the decline was similar for men and women. DLM did not change with LBNP. Conclusion: The decrease in DLCO with LBNP is due to the reductions in thoracic blood volume in both men and women. These thoracic blood volume changes do not explain the previously reported reduced tolerances to LBNP for women because the reductions in thoracic blood volume were similar for men and women. 

Pelvic blood pooling of men and women during lower body negative pressure.
White DD, Montgomery LD.
Aviat Space Environ Med 1996; 67:555-9.
Introduction: The objective of this study was to investigate possible gender differences in the hemodynamic responses of the lower body during lower body negative pressure (LBNP). Methods: In this study, 17 women (mean age = 56 yrs) and 15 men (mean age = 55 yrs) underwent a 15 min exposure to -50 mm Hg LBNP. A Beckman (BR-100) impedance Plethysmograph was used to measure each subjects leg and pelvic blood flow and pooling during the LBNP test. Results: The women had an 83% greater increase in blood volume in the pelvic region than men as a result of the LBNP exposure. Women and men had similar increases in the leg blood volume as a result of the 15 min exposure to - 50mm Hg LBNP. Conclusions: These results demonstrate that women have greater blood pooling in the pelvic region compared to men when exposed to - 50 mm Hg LBNP. These results should be considered when designing life support equipment for men and women pilots and astronauts, especially the designing of anti-G and Space Shuttle re-entry garments.