Antioxidants may Attenuate Plasma Erythropoietin Decline after Hyperbaric Oxygen Diving.

According to previous studies, plasma erythropoietin (EPO) may decrease after hyperbaric oxygen exposure due to oxidative stress. It is hypothesized that the decrease of EPO can be attenuated by oxygen free radical scavengers.The aim of the present study was to evaluate whether EPO plasma levels can be influenced by oral application of vitamin C and E before repeated hyperbaric oxygen exposure during diving. 16 healthy male police task force divers performed 3 morning dives on oxygen within a regular diving schedule on 3 consecutive days. They were randomized into either the placebo group or the vitamin group, receiving 1 g ascorbic acid and 600 IU D-α-tocopherol orally 60 min before the dive. Blood samples for EPO measurement were taken on days 1, 2, and 3 at T1, T3 and T5 60 min before and at T2, T4 and T6 60 min after each dive, respectively. A moderate decrease of EPO was observed beginning at T3 until T6 in the placebo group. The EPO concentrations in the vitamin group did not show relevant variations compared to baseline. Radical scavenging vitamins C and D may counteract hyperbaric oxygen related mechanisms reducing EPO production in hyperbaric oxygen exposure during diving.

The laryngeal tube - a helpful tool for cardiopulmonary resuscitation in the dental office?

BACKGROUND: Supraglottic airway adjuncts such as the laryngeal tube (LT) have been recommended to be used by cardiopulmonary resuscitation (CPR) first responders.Objective This study aims to evaluate the performance characteristics of dental students and dentists using the LT in comparison to a conventional bag valve mask device (BVM) within manikin CPR training. METHOD: A group of eight dentists and 12 dental students performed randomised crossover CPR training using LT and BVM. Time intervals needed to perform five CPR cycles were recorded, as well as tidal and total gastric inflation volumes. RESULTS: Median tidal volumes 0-1025 ml (median 462.5 ml) were observed using BVM and 100-500 ml (median 237.5 ml) with LT (p = 0.02). Total gastric inflation of 0-2900 ml was measured using BVM, no gastric inflation using LT (p = 0.0005). Time intervals needed to perform five CPR cycles did not differ between BVM (range 87.5-354.5 s, median 112 s) and LT (range 84.7-322.3 s, median 114 s) (p = 0.55). A median delay of 37.6 s (range 0-82.1 s) before starting CPR was observed using LT. CONCLUSIONS: Lower tidal volumes but also lower or even no gastric inflation may be observed when dentists use a laryngeal tube during CPR. Respective training must focus on chest compressions. These must be started before inserting the LT or a different supraglottic airway adjunct and be delivered continuously during insertion. It is recommended to use a supraglottic airway such as an LT only after having been trained in its use.

Peripheral venous or tibial intraosseous access for medical emergency treatment in the dental office?

BACKGROUND: The anterior tibia has been recommended as emergency vascular access site if the intravenous route cannot be used. OBJECTIVE: This study aims to evaluate the peripheral venous and anterior tibial intraosseous puncture as alternatives for dentists, using a human and a cadaver model.Method One group of dental students performed a venipuncture by using a standard catheter device (n = 21) on other students. Another group (n = 24) used the Vidacare EZ-IO intraosseous kit on a cadaver tibia with india ink as a tracer. Success rates as well as the time needed for a successful puncture were recorded. RESULTS: 28.5% of venous and 83.3% of intraosseous punctures were successful. The relative risk of venous cannulation failure was 3.4 (95% CI 1.6-7.2; p = 0.0005). A successful venous access could be performed within 163 ± 23.2 seconds (mean ± SD), a tibial intraosseous access within 30 ± 27.8 seconds (p = 0.0003). CONCLUSIONS: Within the limitation of this study, it can be demonstrated that the chances to perform a successful vascular access for inexperienced dentists may be higher when using the tibial intraosseous route for emergency intravascular medication.

Evaluation of pressure-controlled ventilation concepts during cardiopulmonary resuscitation (CPR) in dental chairs.

BACKGROUND: Infrequent training of lay rescuers in cardiopulmonary resuscitation may lead to stomach inflation during ventilation of the unsecured airway. This is caused by a pressure loss of the lower oesophageal sphincter (LOSP) after onset of cardiac arrest. To minimise the risk of stomach inflation, the SMART BAG® (SB), a disposable flow-limited bag-valve-mask resuscitator, has been designed. Aim The aim of this study was to evaluate the occurrence of stomach inflation by use of SB in comparison to two other ventilation devices with respect to the ventilation capability. METHOD: An Easy Grip® disposable bag-valve-mask resuscitator (EG), an SB and an EG with an interposed T-piece attached to a 0.5 l reservoir bag (EG/R) were compared in a manikin ventilation training setting. Fourteen dentists performed ventilations on a Mini Ventilation Training Analyzer using EG, SB and EG/R with lung compliance (LC) and LOSP being adjusted to 700 ml/kPa and 1.5 kPa (best case) and 500 ml/kPa and 0.5 kPa (worst case) in a randomised order. RESULTS: Sufficient tidal volumes were obtained by use of all the three test devices regardless of LC or LOSP. No statistical differences were detected between the use of SB and EG/R. Using EG led to statistically larger volumes. Stomach inflation could only be avoided using SB and EG/R at a high LOSP regardless of LC. CONCLUSION: Even in the worst case scenario, use of SB and EG/R administered sufficient tidal volumes with a significantly smaller stomach inflation compared to EG. Combination of standard bag-valve devices with a reservoir bag may provide similar protection from gastric inflation as the SMART BAG®.

[Invasive techniques in emergency medicine. IV. Cricothyrotomy in emergency situations]. / Invasive Techniken in der Notfallmedizin IV. Koniotomie im Notarztdienst.

Cricothyrotomy is a very invasive technique to secure the airway in an emergency but is irreplacable when less invasive techniques fail or cannot be instigated under the prevailing circumstances. Various techniques have been reported which can be subdivided into anatomical-surgical preparation or puncture techniques. The preferred strategy is mostly oriented towards the departmental standard procedure which will be decided by the clinical situation. Training for each procedure can be carried out in intensive care departments, and using autopsy material or a manekin. Various methods of cricothyrotomy will be discussed here, and additionally an anatomical preparation and two puncture techniques will be demonstrated in detail.

Leukotriene-B4 concentrations in breathing condensate before and after simulated deep dives.

During diving the respiratory tract is exposed to occupational hazards (increased oxygen partial pressure, pulmonary vessel engorgement during submersion, inert gas micro embolism during decompression). Leukotriene-B4 [LTB4] concentrations in the exhaled breath mirrors the inflammatory activity of the airways if the respiratory tract has been exposed to occupational hazards. In this study LTB4-concentrations in the exhaled breath and spirometry data obtained before and after simulated dives helped to elucidate any contributions by hyperbaric exposure to impaired lung function and to separate effects of ambient pressure from those of submersion and increased oxygen partial pressure. Thirty two healthy subjects carried out dives in a hyperbaric chamber using a cross over design to 600 kPa ambient pressure with and without submersion and a dry exposure to pure oxygen at 120 kPa ambient pressure (durations: 43 min). Pre-dive and four hours after surfacing the exhaled breath was collected non-invasively. Condensate was measured by a standard enzyme immuno-assay for LTB4 in parallel with lung function values (FVC, FEV1, MEF 25-75). Pre-exposure baseline values of LTB4-concentrations and lung function values were in the normal range. Post-exposure values did not differ significantly from the baseline values. The data gave no evidence of any inflammatory activity in the subjects' airways after hyperbaric exposure.

[Emergency cricothyrotomy--puncture or anatomical preparation? Peculiarities of two methods for emergency airway access demonstrated in a cadaver model]. / Notfallkoniotomie--Punktion oder chirurgisch-anatomische Präpariertechnik? Besonderheiten zweier Verfahren zur notfallmässigen Atemwegssicherung dargestellt am anatomischen Präparat.

OBJECTIVES: The aim of the study was a demonstration of peculiarities of two invasive airway management methods performed by anesthesiology residents as a subgroup of emergency physicians. METHODS: During an airway management training seminar,2 groups including 18 anaesthesiology residents and 2 students performed a simulated emergency surgical cricothyrotomy on unfixed cadavers. The more experienced physicians in group 2 started with a puncture technique preceding a blind surgical approach. The time needed to perform each procedure and resulting complications were analyzed. RESULTS: The time taken ranged from 75 to 280 s (median 180 s) in group 1 and from 53 to 255 s (median 73 s) in group 2. The surgical approach caused "bleeding" in 40% (group 1) and 30% (group 2) and damage to the cartilages occurred in 20% and 30%, respectively. Punctures were performed within 10-36 s (median 25 s) and 70% were successful without complications. CONCLUSIONS: Puncture of the cricothyroid membrane can serve as initial emergency approach or as intermediate airway access until a surgical method is available.

Effects of ambient cold and depth on lung function in humans after a single scuba dive.

This study evaluated the subacute respiratory effects of diving, to try to separate the effects of ambient temperature from those of depth. In the first experiment 10 healthy men made a compressed-air dive to 50 m that exposed them to cold. They were compared with 10 matched control subjects who underwent the same dive profile but were exposed to a comfortable temperature. In the second experiment 16 healthy subjects made randomized cold dives to both 50 m and 10 m. Pulmonary function tests were made before, after 1 h, and 24 h after the dives. In the first experiment there was an increase in residual volume (P < 0.05) and a decrease in forced expiratory volume at 1 s (FEV1), in forced vital capacity (FVC) and in mid-expiratory flow at 75% of FVC (MEF75) 1 h after the cold dives (P < 0.05). In the second experiment significant increases in specific airways resistance (sR(AW)) (P < 0.05) and decreases in FEV1 (P<0.01), in MEF75 (P<0.05), and in mid-expiratory flow at 25% of FVC (P<0.05), were obtained after the 50 m-dives, whereas SR(AW) increased after the 10 m-dives (P<0.05). The respiratory pattern observed 1 h after cold dives to 50 m indicated airway narrowing. The changes after cold dives to 10 m, however, were of minor magnitude. Both cold and depth seemed to contribute to the adverse effects of a single compressed-air dive on pulmonary function.

Can eustachian tube ventilatory function impairment after oxygen diving be influenced by application of free radical scavenger vitamins C and E?

OBJECTIVES/HYPOTHESIS: To evaluate the influence of free radical scavenger vitamins C and E on eustachian tube ventilatory function changes related to oxygen dives. STUDY DESIGN: Prospective, randomized, double-blind, placebo-controlled study of middle ear impedance changes of oxygen divers being orally treated with free radical scavenger vitamins C and E. METHODS: Fifteen divers were allocated to two groups. Before diving on oxygen on consecutive days (days 1 and 2), divers in group 1 took a daily dose of 1 g ascorbic acid and 600 International Units d-alpha-tocopherol and divers in group 2 were given placebo. Before diving and 2 and 24 hours after diving on days 1 and 2, middle ear impedance was measured. RESULTS: Impedance decreased overnight after dive 1 (P =.04) but not after dive 2 (P =.31). No impedance differences were found between groups after the dive on day 1 (P =.83). Twenty-four hours after the dive on day 1 and after the dive on day 2, impedance values in both groups were different (P =.02 vs. P =.07), emphasizing slightly more negative pressures in the vitamin group. CONCLUSION: Vitamins C and E did not reduce eustachian tube ventilatory function impairment overnight after the dive on day 1, suggesting no evidence of free radical-mediated toxicity affecting the eustachian tube or middle ear mucosa. Repetitive oxygen dives may cause tissue adaptation suggesting other than antioxidant defense mechanisms.

Respiratory effects of a single dive to 50 meters in sport divers with asymptomatic respiratory atopy.

Increasing popularity of sports diving makes it likely that subjects with allergic respiratory diseases will be involved in diving with self contained underwater breathing apparatus (scuba). The present study evaluated the effects of a single scuba-dive on pulmonary function in subjects with respiratory atopy. Specific airways conductance (sGaw), residual volume (RV), forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), mid expiratory flow at 50% of FVC (MEF50), and transfer factor for carbon monoxide (TLCO) were measured in 9 sport divers with a history of hay fever and 9 matched healthy sport divers (control) before, 3 hours and 24 hours after a wet hyperbaric chamber dive to a depth of 50 m. Airway hyperresponsiveness (AHR) was assessed by methacholine challenge 4 weeks after the dive. Atopic subjects and controls did not differ with respect to anthropometric data, diving experience, and predive lung function. A 3% reduction in FVC was found 24h after the dive (p < 0.05) in both groups, whereas sGaw decreased by 15% 24 h after the dive (p < 0.05) in the subjects with respiratory atopy only. Postdive changes in RV, FEV1, MEF50, and TLCO did not reach level of statistical significance. AHR was obtained in 8/9 subjects with respiratory atopy. We conclude that subjects with atopic sensitization and asymptomatic AHR may be more susceptible to effects of diving on pulmonary function.

Underwater application of nasal decongestants: method for special operations.

A simple method of emergency underwater application of a nasal decongestant in divers to prevent diving-related accidents or even fatalities attributable to sequelae of middle-ear and sinus barotrauma of ascent was evaluated. Eleven military divers had to inject 1 mL of 0.02% methylene blue into a central venous catheter after having inserted the tip between their upper lip and the mask at 1 m depth in a pool. After injection, the head had to be reclined. Blue liquid flowing from a diver's nostril and a "bitter" taste sensation reported immediately after surfacing indicated successful application. All divers were observed to have had blue liquid flowing from the nostril of application, and one diver could not describe the taste. This method of underwater application of nasal decongestants may be useful for emergency prevention in divers, especially during covert operations. Underwater availability of the system in a special kit carried by divers would be required.

Exposure to soda-lime dust in closed and semi-closed diving apparatus.

BACKGROUND: Chronic exposure to hyperbaric hyperoxia and venous gas microembolism have been shown to contribute to the long term health effects of diving, especially diver's lung function. Factors related to special diving equipment may add to these effects. This study was conducted to evaluate possible additional hazards for respiratory function of divers employing closed and semi-closed diving apparatus. METHODS: We analyzed soda-lime dust found in the air-intake loop of a closed-circuit oxygen rebreathing diving apparatus which had passed through the filter screen of the diving apparatus's soda-lime cartridge. The geometrical characteristics were evaluated by scanning electron microscopy. The amount of dust that passed through the screen during a normal dive profile was measured by an artificial airflow through a filter membrane. After dives by subjects using these devices, the pH-value of water condensate in the air-intake hose was measured. RESULTS: There was a relevant amount of residual soda-lime dust found in the air-intake loop. The dust particles showed diameters down to 1 micron and a rounded structure. The total amount of dust averaged 9.6 mg.m-3 of breathing mixture. During diving, the mean pH-value of condensate in the hose is estimated at 8.87 (+/- 0.12). CONCLUSION: There is a relevant exposure to soda-lime dust in divers using closed-circuit rebreathing apparatus. This occupational exposure may contribute to chronic airway inflammation and subsequent development of small airway disease in divers.

Modified closed circuit underwater breathing apparatus LAR VII and laryngeal mask airway as adjuncts for dive buddy artificial ventilation.

This study evaluated the feasibility of using the modified semi-closed circuit underwater rebreathing system (URS) LAR VII in connection with a laryngeal mask airway (LMA) as an expedient ventilatory adjunct in an operational setting. Fourteen combat swimmers, unfamiliar with this equipment, underwent cardiopulmonary resuscitation (CPR) mannequin training using these devices. Eighteen subjects, using a standard AMBU bag for ventilation, served as controls. Thirteen test persons were able to ventilate with the modified URS. Tidal volumes were significantly lower with the LAR VII/LMA than with the AMBU bag (medians, 350 vs. 800 mL). No significant difference was found in total time required for 10 CPR cycles (medians, 78 vs. 68.5 seconds). The median delay between recognition of cardiac arrest and first chest compression, however, was markedly increased with the LAR VII/LMA than with the AMBU bag (medians, 76.5 vs. 14.5 seconds). After proper training, divers might use a modified URS such as the LAR VII for CPR in connection with a LMA. Lower tidal volumes might prevent gastric inflation. Chest compression should be continued during LMA insertion.

Modification of the closed circuit underwater breathing apparatus LAR V makes it suitable for cardiopulmonary resuscitation (CPR).

UNLABELLED: This pilot study was carried out in order to determine whether or not a modified closed circuit underwater oxygen rebreathing device could serve as an adjunct for ventilation during CPR in remote locations. As a control a common self-inflating bag valve ventilation device was used. METHODS: A total of 20 combat divers were enrolled, of whom 18 met the criteria to be included in two-rescuer CPR manikin training. A modified LAR V (Drager, Germany), a closed circuit underwater breathing apparatus, that uses pure oxygen, and a conventional Ambu Mark III bag were used for artificial mask-ventilation in a randomised crossover design. A total of ten cycles of CPR were analysed. RESULTS: Of the divers, 17 were able to ventilate with the modified LAR V. The median tidal volumes were lower with LAR V versus Ambu (725 vs 800 ml; P = 0.04) and median total time required was significantly longer with LAR V versus Ambu (90 vs 68.5 s; P = 0.004). Gastric inflation was associated only with the Ambu. CONCLUSIONS: This modification of the LAR V makes it suitable for CPR performed by military divers when conventional ventilatory devices are not available. It would be necessary, however, to teach the proper use of the modified ventilation mode and to provide repeated training.

Emergency medical training for dental students.

Twenty-four of the thirty-two German universities that have dental schools replied to a questionnaire survey that showed that all the schools responding held lectures on the topic "Medical Emergencies" although this is not mandatory for registration. All of the universities in the former East Germany also offered practical training sessions as part of the curriculum. The proportion of West German universities offering such courses is only 60%. The basic essentials of the theory and practice of emergency medicine should only be taught in courses with mandatory participation.