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Biomedical subjects

C M Muth

Publications and source records attributed to C M Muth.

At least 19 recordsLinked to original sources
PubMed2007

[Oxygen therapy in diving accidents].

Diving accidents represent a departure from the routine practice of emergency physicians. The incidence of non-fatal diving accidents is reported as 1-2 per 10,000 dives. Apart from adequate intravenous hydration, oxygen is the only medication with a proven effect in the treatment of diving accidents. After a typical diving accident, administration of oxygen at an inspired concentration (F(I)O(2) 1.0) as high as possible is recommended. Many divers bring along their own oxygen administration systems to the diving sites and these are often better suited for the treatment of diving accidents than the oxygen systems of many emergency responders. Pressure regulators supplying low constant flow oxygen, nasal prongs and inhalation masks are inappropriate. When using artificial ventilation bags with face masks, an oxygen flow of at least 15 l/min should be used. Demand regulators are simple to use and able to deliver a F(I)O2 of 1.0. Their ease of use has earned them high marks in the emergency management of diving accidents and their similarity to standard diving equipment has also aided relatively widespread acceptance. Circulation breathing systems are more technologically complex oxygen delivery systems which permit CO2 absorption and re-breathing at low oxygen flow. In contrast to the demand modules, the likelihood of mistakes during their usage is higher. In diving accidents, the administration of normobaric oxygen, already begun in the field, is the most important therapy and should not be interrupted. Presented with an inadequate supplemental oxygen supply, the inspired oxygen concentration should not be decreased, rather the duration of the oxygen administration should be reduced. Hyperbaric oxygen therapy should be the mainstay of further treatment.

Accidents↗
PubMed2005

[Diving fitness for scuba divers--what the primary care physician should know].

The diving fitness medical examination serves to show and reveal medical conditions that are a contraindication for diving or to evaluate the risk of preexisting conditions. For this reason, it should never have the character of a certification given as a matter of courtesy. Fitness to dive is given if the candidate is healthy and when there are no pathological findings. Even with deviations from the norm, diving is still possible, but with restrictions. Important organ systems for the diving fitness examination are the cardiovascular system, the respiratory organs and the ears. In addition, adequate eyesight is important. The German Society of Diving and Hyperbaric Medicine (GTOUM) has drawn up recommendations on the examination of scuba divers to assist the physician (www.gtuem.org).

Diving↗
PubMed2005

[Medical aspects of diving in the tropics].

Scuba diving vacations in tropical surroundings belong to the repertoire of most divers. In addition to carefully making travel plans and taking care of the necessary vaccinations and appropriate malaria prophylaxis, the following points also must be observed. The flight itself affects diving safety. In particular, a too short time interval between diving and the return flight can lead to decompression problems. Because most of the diving areas are reached by ship, many divers need a prophylaxis against motion sickness. Moreover, external otitis occurs more frequently while diving in the tropics. Finally, there is potential danger from the sea inhabitants, primarily from scorpion fishes, Portuguese Man-of-Wars, box jellyfishes as well as cone snails.

Animals↗
PubMed2005

[Injuries caused by pressure differences while diving].

Barotraumas are caused by pressure differences. As described by Boyle's Law, barotraumas develop during the descent phase of diving (and much more rarely during the ascent). The most frequently affected are the ears and paranasal sinuses, in addition to the facial skin and eyes. The most important preventive measure is performing pressure compensation in the affected body cavities. Barotrauma is treated symptomatically.

Athletic Injuries↗
PubMed2005

[Decompression injuries].

A decompression accident occurs during uncontrolled dive ascent with diving equipment. Through the rapid decrease in the surrounding pressure, gas bubbles form in the blood and tissues. Depending upon the mechanism of onset, the decompression illness (DCI) is classified as decompression sickness (DCS) or arterial gas embolism (AGE). The therapy consists of administering, as quickly as possible, 100% oxygen as well as a volume substitution. The treatment is continued in a recompression chamber.

Decompression Sickness↗
PubMed2005

[Problems in the deep: the isopression phase].

Fundamentally, accident mechanisms during the isopression phase of diving are primarily dependent upon the partial pressures of the respiratory gases. An increased nitrogen partial pressure leads to compressed-air intoxication; an increased oxygen partial pressure while diving with oxygen-enriched gas mixtures can trigger an oxygen-induced convulsion. Elevated pCO2 can be provoked by inadequate breathing and/or physical exertion at greater diving depths. Through an adjusted diving behavior and observation of the limits, these problems could be easily avoided.

Acclimatization↗
PubMed2005

Demographics and respiratory illness prevalence of sport scuba divers.

This study aimed to establish epidemiological data on diving habits and outcome of subjects with respiratory diseases who are considered at increased risk for diving injuries. We conducted a cross-sectional demographics and prevalence study by distribution of an anonymous questionnaire with an issue of a widespread sport diving magazine. The questionnaire was designed to obtain medical and diving history data with an emphasis on respiratory diseases and complaints. The investigational population comprised sport scuba divers of any age and gender from Austria, Germany, and Switzerland. Two hundred and twenty-six male and 96 female divers sent completed questionnaires. Of the respondents 8.7 % indicated that they currently have asthma. Two thirds of asthmatics complained about regular dyspnoea. However, only 42.4 % used drugs relieving or controlling their symptoms regularly and 27.3 % used them in a prophylactic manner before diving. Five percent and 4.7 % of all divers reported a history of respiratory disease other than asthma or dyspnoea respectively. The divers with respiratory illness or complaints had logged a total of 17,386 dives. There were no cases of serious diving injuries. Despite the well-known limitations of postal surveys assessing self reported data, this study indicates that there is a population of subjects diving uneventfully with respiratory diseases that are considered medical contraindications to diving. These subjects deserve particular guidance on related risks and disease management.

Adult↗
PubMed2003

Arterial blood gases during diving in elite apnea divers.

Elite apnea divers have considerably extended the limits of dive depth and duration but the mechanisms allowing humans to tolerate the compression- and decompression-induced changes in alveolar gas partial pressures are still not fully understood. Therefore we measured arterial blood gas tensions and acid-base-status in two elite apnea divers during simulated wet dives lasting 3 : 55 and 5 : 05 minutes, respectively. Arterial pO2 followed the compression-(from 13.8/16.9 kPa before the dive to 30 kPa at the start of the bottom time) and decompression-induced (from 13.7/21.0 kPa to 3.3/4.9 kPa immediately after surfacing) variations of ambient pressure, while the arterial pCO2 remained within the physiologic range (3.0/3.9 kPa before diving vs. 5.7/5.9 kPa at the end of the bottom time), probably due to the CO2 storage capacity of the blood. These findings may help to explain why humans can sustain deep and long apnea dives without major increases in respiratory drive.

Acid-Base Equilibrium↗
PubMed2001

[Hyperbaric oxygen therapy in trauma surgery].

Hyperbaric oxygenation is achieved when a patient breathes 100 percent oxygen in an environment of elevated atmospheric pressure. Physiologically, this produces a directly proportional increase in the plasma volume fraction of transported oxygen which is readily available for cellular metabolism. A number of beneficial biochemical, cellular and physiologic effects result which account for the use of hyperbaric oxygen as an adjunctive therapy in the treatment of clostridial myonecrosis, crush injuries, compromised flaps, osteoradionecrosis and chronic problem wounds. Indications, modes of treatment, contraindications, side effects, costs and experimental and clinical results are presented. Overall, these data demonstrate that hyperbaric oxygen is no longer "a therapy in search of diseases". However, more randomized controlled clinical trials are necessary to demonstrate its efficacy.

Contraindications↗
PubMed2001

Administration of 100% oxygen in diving accidents--an evaluation of four emergency oxygen devices.

As the use of oxygen enhances the resorption of gas bubbles in decompression illness, it is recommended and generally accepted that the inspired oxygen concentration in emergency treatment of diving accidents has to be as close to 100% as possible. Therefore, several emergency oxygen devices are offered to the diving community but only with little data in literature on the efficacy of these devices. We tested four emergency oxygen devices with respect to efficacy of oxygen supply and breathing comfort at rest. Nine blinded volunteers had to breathe from the four systems with face mask and mouthpiece as well. Gases were measured with mass spectrometry during a 3 min interval from a capillary port close to the subject. The results showed that none of the systems was able to deliver 100% oxygen all the time, but in three systems inspiratory oxygen values were achieved, although in one system the nitrogen wash-out was slowed due to air contamination during inspiration. The fourth tested system frequently supplied the subjects simply with air while breathing at rest. We conclude from our study that it is difficult to achieve oxygen levels close to 100% in practice. Even in a perfectly working system, the interface between device and subject is a source of entrained air, especially when oxygen breathing has to be performed over a longer period of time. In addition, two of four systems had conceptional problems to supply the subjects with pure O2 during inspiration. None of the tested systems was perfectly designed to serve in such emergencies.

Adult↗
PubMed2001

Diver with decompression injury, elevation of serum transaminase levels, and rhabdomyolysis.

A 43-year-old female recreational scuba diver presented to the emergency department 1 hour after a rapid, uncontrolled ascent. Her presentation included progressing confusion, slow and slurred speech, and complaints of headache and hypesthesia over her forearms and anterior thighs bilaterally. Differential diagnosis included arterial gas embolism and decompression sickness. She underwent recompression therapy with US Navy Table 6 within 120 minutes of her ascent. After recompression therapy, the patient had signs and symptoms consistent with severe rhabdomyolysis, including creatine kinase levels of 36,000 U/L and myoglobinuria.

Adult↗
PubMed2000

Gas embolism.

Explore the source record for details and available documents.

Animals↗
PubMed2000

[Severe diving accidents: physiopathology, symptoms, therapy].

Decompression injuries are potentially life-threatening incidents, generated by a rapid decline in ambient pressure. Although typically seen in divers, they may be observed in compressed air workers and others exposed to hyperbaric environments. Decompression illness (DCI) results from liberation of gas bubbles in the blood and tissues. DCI may be classified as decompression sickness (DCS) or arterial gas embolism (AGE), depending on where the gas bubbles lodge. DCS occurs after longer exposures to a hyperbaric environment with correspondingly larger up-take of inert gas. DCS may be classified into type 1 with cutaneous symptoms and musculoskeletal pain only or type 2 with neurologic and/or pulmonary symptoms as well. AGE usually results from a pulmonary barotrauma, and with cerebral arterial involvement, the symptoms are similar to a stroke. The most important therapy, in the field, is oxygen resuscitation with the highest possible concentration and volume delivered. The definitive treatment is rapid recompression with hyperbaric oxygen therapy. Additional therapeutic measures are discussed.

Animals↗
PubMed1999

[Outcome of hyperbaric oxygen therapy in therapy refractory tinnitus].

Although many studies are available concerning the treatment of sudden deafness using hyperbaric oxygenation, only a few of these deal with tinnitus. The aim of the present study was to evaluate the therapeutic use of hyperbaric oxygenation in cases of tinnitus. A total of 193 patients, having undergone primary intravenous hemorheologic therapy, were treated with hyperbaric oxygenation. Tinnitus was evaluated before, after ten sessions and after 15 sessions using a tinnitus questionnaire. Additionally, an audiometric examination was performed. Measurable improvements of the tinnitus occurred in 22% of the patients, whereas a moderate improvement was seen in 17% of cases. 10.4% showed an excellent improvement and tinnitus disappeared completely in two patients. The improvement rate decreased in those cases where the time from onset of tinnitus exceeded 40 days. In conclusion, hyperbaric oxygenation seems to be a moderately effective additional treatment in the therapy of tinnitus after primary hemorheologic therapy, provided the time from onset of tinnitus is less than 1 month.

Adolescent↗
PubMed1996

The use of countercurrent heat exchangers diminishes accidental hypothermia during abdominal aortic aneurysm surgery.

BACKGROUND: Perioperative hypothermia is common and likely contributes to morbidity, but the efficacy of prophylactic fluid warning has hardly been analyzed systematically. We tested the hypothesis that the use of an infusion/blood warmer, based on the principle of countercurrent heat exchange, reduces incidence and degree of severe hypothermia following aortic surgery. METHODS: In a prospective randomized investigation of patients (n = 50) undergoing elective abdominal aortic aneurysm surgery, all fluids/blood products (approx. 3500 ml) administered intraoperatively were infused either (n = 25) via countercurrent-like heat exchangers (Hotline Level 1 Technologies Inc.) or without (n = 25) taking special precautions (infusions stored at 21 degrees C, blood products heated to 37 degrees C in a water bath). Anaesthesia was standardized using a thiopentone, fentanyl, vecuronium induction sequence, and maintained by isoflurane in N2O/O2. RESULTS: The perioperative decrease of oesophageal temperature (-0.35 degree C +/- 0.4) in the group managed with heat exchangers was significantly smaller (P < 0.0001) than in the control group (-1.5 degrees C +/- 0.54), and oesophageal temperature at the end of surgery was considerably higher (35.1 degrees C +/- 0.45 vs. 34.2 degrees C +/- 0.7; P < 0.0001). Furthermore, while postoperative hypothermia below 34.5 degrees C was observed in 16 patients (incidence: 64%) of the control group, it occurred in only 2 patients (incidence: 8%) managed with heat exchangers (P < 0.001). CONCLUSIONS: The efficacy of fluid/blood warmers has hitherto only been evaluated in bench tests. Our results demonstrate that the use of heat exchangers alone, while not completely preventing hypothermia, markedly reduces the incidence of severe perioperative hypothermia, and lessens its degree during abdominal aortic aneurysm surgery.

Aged↗
PubMed1994

Exercise effects on central venous nitrogen tensions after simulated non-decompression dives.

In five subjects we examined the effect of exercise on the pattern of central venous (right atrial) N2 tensions (PVN2) after ascent from simulated non-decompression dives. The dives consisted of exposure to air at 3 bar for 20 min with 10 min of exercise (workload 75 W) at depth to achieve near-complete N2 saturation of the muscles. After the dive the subjects rested or, on another day, exercised for 30 min (workload 100 W) starting 10 min after completing the ascent. Blood samples taken every 10 min until the 60th min and 90 min after the dive were analyzed for PVN2 using a manometric Van Slyke apparatus. The amount of N2 eliminated was estimated from the PVN2 by adapting the Fick principle. Immediately after the ascent, PVN2 were 950 +/- 39 and 942 +/- 27 mmHg, respectively, in the rest and experiment series. In the rest experiments PVN2 continuously decreased to 606 +/- 8 mmHg 90 min after the dive, remaining significantly higher (P < 0.05) than before the dive. Exercise caused the PVN2 to increase beyond the corresponding levels of the rest experiments (P < 0.05 at 20 and 30 min exercise). After the exercise PVN2 rapidly declined, reaching predive levels 60 min after the ascent. Exercise increased N2 elimination to 970 +/- 143 ml, whereas it had been 311 +/- 61 ml (P < 0.05) in the corresponding phase of the rest experiments. We conclude that if extensive supersaturation and bubble formation can be avoided, such as probably was the case in our shallow non-decompression dives, exercise after the ascent accelerates N2 elimination.

Adult↗
PubMed1993

A case of breath holding and ascent-induced circulatory hypotension.

We report a case of transient circulatory depression due to inadvertent apnea of a subject during decompression from a stimulated dive. The dive consisted of exposure to air at 5 bar and subsequent decompression stops. Arterial blood pressure and a lead II ECG were recorded continuously. During decompression from 1.6 to 1.3 bar, the subject inadvertently held his breath. Arterial pressure fell rapidly from 120/80 to 60/53 mmHg within 20 s. Recognizing that the subject held his breath, one of the supervisors ordered him to resume breathing, and arterial blood pressure was restored rapidly. This circulatory depression was probably due to reduced stroke volume such as described for the syncope of ascent: with the subject retaining his breath, the expanding lung volume increased intrathoracic pressure resulting in impaired venous return.

Atmosphere Exposure Chambers↗