Comparison of Laryngeal Mask Airway Seal Between Anesthesiologists and Individuals Without Previous Airway Experience.

BACKGROUND: Tracheal intubation is the gold standard for airway management in emergency medicine, but more difficult to apply for inexperienced individuals than laryngeal mask airway (LMA). OBJECTIVE: The aim of our study was to investigate if inexperienced individuals are able to secure the airway with the help of LMA after a short introduction. A second aim was to evaluate Thiel-fixed specimens against unfixed ones. METHODS: In a body donor model, LMA application was evaluated between medical students without previous airway experience and anesthesiologists by comparing the sealing of the larynx using a water column applied to the esophagus. RESULTS: LMAs were successfully applied in 46 out of 55 (83.6%) attempts by medical students and in 30 out of 39 (76.9%) attempts by anesthesiologists. Among medical students, 14.1% of all LMA applications were primarily leaky, compared with 18.8% in anesthesiologists. Esophageal sealing was better in Thiel-fixed specimens (leakage 10.9%) compared with unfixed specimens (leakage 22.9%). Our data showed no significant difference between anesthesiologists and medical students in terms of sealing of LMA. Therefore, we conclude that medical students without previous airway experience can quickly learn to apply LMA sufficiently and thus, achieve aspiration protection similar to anesthesiologists. CONCLUSION: Medical students without previous airway experience can successfully insert LMAs after a short introduction. Thiel-fixed specimens are suitable for studies as well as for training in LMA application.

Analysis of tourniquet pressure over military winter clothing and a short review of combat casualty care in cold weather warfare.

Cold weather warfare is of increasing importance. Haemorrhage is the most common preventable cause of death in military conflicts. We analysed the pressure of the Combat Application Tourniquet® Generation 7 (CAT), the SAM® Extremity Tourniquet (SAMXT) and the SOF® Tactical Tourniquet Wide Generation 4 (SOFTT) over different military cold weather clothing setups with a leg tourniquet trainer. We conducted a selective PubMed search and supplemented this with own experiences in cold weather medicine. The CAT and the SAMXT both reached the cut off value of 180mmHg in almost all applications. The SOFTT was unable to reach the 180mmHg limit in less than 50% of all applications in some clothing setups. We outline the influence of cold during military operations by presenting differences between military and civilian cold exposure. We propose a classification of winter warfare and identify caveats and alterations of Tactical Combat Casualty Care in cold weather warfare, with a special focus on control of bleeding. The application of tourniquets over military winter clothing is successful in principle, but effectiveness may vary for different tourniquet models. Soldiers are more affected and impaired by cold than civilians. Military commanders must be made aware of medical alterations in cold weather warfare.

Editorial on the Research Topic of Sports Training and the Promotion of Physical Health.

Sport activities are a deciding factor in maintaining or achieving physical health [...].

Initial Treatment of High-Altitude Pulmonary Edema: Comparison of Oxygen and Auto-PEEP.

BACKGROUND: Improvement of oxygenation is the aim in the therapy of high-altitude pulmonary edema (HAPE). However, descent is often difficult and hyperbaric chambers, as well as bottled oxygen, are often not available. We compare Auto-PEEP (AP-Pat), a special kind of pursed lips breathing, against the application of bottled oxygen (O2-Pat) in two patients suffering from HAPE. METHODS: We compare the effect of these two different therapies on oxygen saturation measured by pulse oximetry (SpO2) over time. RESULT: In both patients SpO2 increased significantly from 65-70% to 95%. Above 80% this increase was slower in AP-Pat compared with O2-Pat. Therapy started immediately in AP-Pat but was delayed in O2-Pat because of organizational and logistic reasons. CONCLUSIONS: The well-established therapies of HAPE are always the option of choice, if available, and should be started as soon as possible. The advantage of Auto-PEEP is its all-time availability. It improves SpO2 nearly as well as 3 L/min oxygen and furthermore has a positive effect on oxygenation lasting for approximately 120 min after stopping. Auto-PEEP treatment does not appear inferior to oxygen treatment, at least in this cross-case comparison. Its immediate application after diagnosis probably plays an important role here.

Effects of Acute Exposure and Acclimatization to High-Altitude on Oxygen Saturation and Related Cardiorespiratory Fitness in Health and Disease.

Maximal values of aerobic power (VO2max) and peripheral oxygen saturation (SpO2max) decline in parallel with gain in altitude. Whereas this relationship has been well investigated when acutely exposed to high altitude, potential benefits of acclimatization on SpO2 and related VO2max in healthy and diseased individuals have been much less considered. Therefore, this narrative review was primarily aimed to identify relevant literature reporting altitude-dependent changes in determinants, in particular SpO2, of VO2max and effects of acclimatization in athletes, healthy non-athletes, and patients suffering from cardiovascular, respiratory and/or metabolic diseases. Moreover, focus was set on potential differences with regard to baseline exercise performance, age and sex. Main findings of this review emphasize the close association between individual SpO2 and VO2max, and demonstrate similar altitude effects (acute and during acclimatization) in healthy people and those suffering from cardiovascular and metabolic diseases. However, in patients with ventilatory constrains, i.e., chronic obstructive pulmonary disease, steep decline in SpO2 and V̇O2max and reduced potential to acclimatize stress the already low exercise performance. Finally, implications for prevention and therapy are briefly discussed.

Rapid ascents of Mt Everest: normobaric hypoxic preacclimatization.

BACKGROUND: Acclimatization to high altitude is time consuming. An expedition to Mt Everest (8848 m) requires roughly 8 weeks. Therefore it seems very attractive to reach the summit within 3 weeks from home, which is currently promised by some expedition tour operators. These rapid ascent expeditions are based on two main components, normobaric hypoxic training (NHT) prior to the expedition and the use of high flow supplemental oxygen (HFSO2). We attempted to assess the relative importance of these two elements. METHODS: We evaluated the effect of NHT on the basis of the available information of these rapid ascent expeditions and our experiences made during an expedition to Manaslu (8163 m) where we used NHT for preacclimatization. To evaluate the effect of an increased O2 flow rate we calculated its effect at various activity levels at altitudes of 8000 m and above. RESULTS: So far rapid ascents to Mt Everest have been successful. The participants carried out 8 weeks of NHT, reaching sleeping altitudes = 7100 m and spent at least 300 h in NH. At rest a flow rate of 2 l O2/min is sufficient to keep the partial pressure of inspired oxygen (PIO2) close to 50 mm Hg even at the summit. For ativities of ~80% of the maximum rate of oxygen consumption (VO2max) at the summit 6 l O2/min are required to maintain a PIO2 above 50 mm Hg. DISCUSSION: NHT for preacclimatization seems to be the decisive element of the offered rapid ascent expeditions. An increased O2 flow rate of 8 l/min is not mandatory for climbing Mt Everest. CONCLUSIONS: Preacclimatization using normobaric hypoxica (NH) is far more important than the use of HFSO2. We think that NHT will be widely used in the future. The most effective regimen of preacclimatization in NH, the duration of each session and the optimal FIO2 are still unclear and require further study.

The correct measurement of oxygen saturation at high altitude.

BACKGROUND: Compared to measurements at sea level, measurement of oxygen saturation by pulse oximetry (SpO2) at altitude differs fundamentally because of the cyclical course of SpO2, caused by periodic breathing. Therefore, the determination of a representative SpO2 value is difficult. In the literature, recommendations for a standardized measurement procedure are missing; different studies measure SpO2 in different ways. KEY QUESTION: Does the visually determined SpO2 value correlate with the actual average of the measurement interval? METHODS: Four participants of an expedition (6013 m; Pakistan), familiar with pulse oximetry at altitude, wrote down the representative value of the measurement interval of 3 min (SpO2visual) according to their individual observation. The used pulse oximeter saved the value for SpO2 every 4 s. Based on this, the calculated mean (SpO2memory) was compared to SpO2visual after finishing the expedition (128 measurements > 2500 m). RESULTS: The spread of the single values within the measurement interval is high (in single cases up to 17%-points) in case of insufficient acclimatization. With increasing acclimatization, the measured values stabilize. SpO2visual differs only marginally (- 0.4%-points; ± 0.8) compared to SpO2memory. CONCLUSIONS: The correct pulse oximetric determination of SpO2 at high altitude requires a standardized measurement procedure; the investigator is familiar and trained. Anyway, the measurements have to be done in the continuous mode of the pulse oximeter over a sufficient timeframe (3 SpO2-fluctuation cycles; 2-3 min). We recommend to record the maximum and the minimum value of the measurement interval and to use a pulse oximeter device with memory function.

Challenges of Military Health Service Support in Mountain Warfare.

INTRODUCTION: History is full of examples of the influence of the mountain environment on warfare. The aim of this article is to identify the main environmental hazards and summarize countermeasures to mitigate the impact of this unique environment. METHODS: A selective PubMed and Internet search was conducted. Additionally, we searched bibliographies for useful supplemental literature and included the recommendations of the leading mountain medicine and wilderness medicine societies. RESULTS: A definition of mountain warfare mainly derived from environmental influences on body functions is introduced to help identify the main environmental hazards. Cold, rugged terrain, hypoxic exposure, and often a combination and mutual aggravation of these factors are the most important environmental factors of mountain environment. Underestimating this environmental influence has decreased combat strength and caused thousands of casualties during past conflicts. Some marked differences between military and civilian mountaineering further complicate mission planning and operational sustainability. CONCLUSIONS: To overcome the restrictions of mountain environments, proper planning and preparation, including sustained mountain mobility training, in-depth mountain medicine training with a special emphasize on prolonged field care, knowledge of acclimatization strategies, adapted time calculations, mountain-specific equipment, air rescue strategies and makeshift evacuation strategies, and thorough personnel selection, are vital to guarantee the best possible medical support. The specifics of managing risks in mountain environments are also critical for civilian rescue missions and humanitarian aid.

Oxygen saturation increases over the course of the night in mountaineers at high altitude (3050-6354 m).

BACKGROUND: Blood oxygen saturation (SpO 2 ) is frequently measured to determine acclimatization status in high-altitude travellers. However, little is known about nocturnal time course of SpO 2 (SpO 2N ), but alterations in SpO 2N might be practically relevant as well. To this end, we describe the time-course of SpO 2N in mountaineers at high altitude. METHODS: SpO 2N was continuously measured in ten male mountaineers during a three-week expedition in Peru (3,050-6,354m). Average SpO 2N of the first (SpO 2N1 ) and second half (SpO 2N2 ) of an individual's sleep duration was calculated from 2h intervals of uninterrupted sleep. Heart rate oscillations and sleep dairies were used to exclude periods of wakefulness. SpO 2 was also measured at rest in the morning. RESULTS: SpO 2N significantly increased from SpO 2N1 to SpO 2N2 . The magnitude of this increase (ΔSpO 2 ) was reduced with time spent at altitude. On night 1 (3,050m) SpO 2 increased from 83.4% (N1) to 86.3% (N2). At the same location on night 21, SpO 2 increased from 88.3% to 90.1%, which is a relative change of 4.7% and 2.0%, respectively. This pattern of increase in SpO 2N was perturbed when individual acclimatization was poor or altitude was extreme (5630m). SpO 2N was significantly lower than SpO 2 at rest in the morning. CONCLUSIONS: This study is the first to demonstrate an increase of SpO 2 during the night in mountaineers at high altitude (3,050-6,354m) with high consistency between and within subjects. The magnitude of ΔSpO 2N decreased as acclimatization improved, suggesting that these changes in ΔSpO 2 between nights might be a valuable indicator of individual acclimatization. In addition, the failure of any increase in SpO 2N during the night might indicate insufficient acclimatization. Even though underlying mechanisms for the nocturnal increase remain unclear, the timing of SpO 2N measurement is obviously of utmost importance for its interpretation. Finally our study illustrates the detailed effects of ventilatory acclimatization over several weeks.

Injuries, Medical Conditions, and Changes in Blood Levels in German Special Operations Forces Selection.

BACKGROUND: Medical conditions often develop during military training. The aim of this study was to compile medical conditions and injuries sustained during a 5-day military exercise, compare them with incidences at similar civilian events, and subsequently identify differences between those who finished the exercise (Finishers) and those who did not (Nonfinishers) to identify preventable causes for not finishing and to reduce unnecessary health risks. METHODS: Fifty-one soldiers had their blood parameters (creatine kinase [CK], aspartate transaminase [AST], alanine transaminase [ALT], gamma-glutamyl transferase [GGT], C-reactive protein [CRP], leukocytes, sodium), weight loss, and body temperature determined after the exercise. Additionally, the injuries and conditions that led the Nonfinishers to drop out were recorded. RESULTS: The main reasons why Nonfinishers did not complete the exercise were physical exhaustion and minor injuries. After exercise, the Finishers showed only slightly increased incidence of hyponatremia, higher levels of CK, and significantly higher levels of AST, ALT, and CRP, and body weight loss. The Nonfinishers? results were significant for an elevated leukocyte count and lower mean temperatures. CONCLUSION: The specifics of military training did not influence the kind or the number of exertion-related medical conditions compared to similar civilian events. Both Finishers and Nonfinishers are at risk of developing exertion-related medical conditions such as rhabdomyolysis and hyponatremia. However, plain water did not increase the risk of exertional hyponatremia. Leukocytosis found in the Nonfinisher group could have been due to acute excessive exertion and, therefore, may be an indicator of general systemic fatigue. This could be used to differ between physical and psychological reasons for not finishing.

Improvement in altitude performance test after further acclimatization in pre-acclimatized soldiers.

The Altitude Performance Test is a measure designed to assess an individual's degree of acclimatization to reduce the risk of acute mountain sickness during high-altitude activities. The aim of this study was to investigate the hypothesis that test results will improve in pre-acclimatized soldiers after several days of further acclimatization. The Altitude Performance Test consists of an uphill run at high altitude. The event is timed and performed with continuous oxygen saturation (SpO2) monitoring. The individual's time and lowest SpO2 measurement are recorded. This test was performed on the first day of arriving at 11,060 ft, and after 9 days at the same location. The 37 male soldiers were all pre-acclimatized before arrival. The sleeping altitude remained constant at 11,060 ft, and the daytime altitudes increased up to a maximum of 15,775 ft. Test results improved significantly after a further 9 days of acclimatization (time, -11 s; SpO2, +5%-points; p ≤ 0.001). This is remarkable because all soldiers were pre-acclimatized and showed only minor acute mountain sickness symptoms during the entire stay. This indicates that the acclimatization process is not finished after amelioration of altitude symptoms. The demonstrated improvement in physical performance could prove very important, particularly during military missions performed at high altitude.

Decrease of asymmetric dimethylarginine predicts acute mountain sickness.

INTRODUCTION: Each year, 40 million tourists worldwide are at risk of getting acute mountain sickness (AMS), because they travel to altitudes of over 2500 m. As asymmetric dimethylarginine (ADMA) is a nitric oxide synthase (NOS) inhibitor, it should increase pulmonary artery pressure (PAP) and raise the risk of acute mountain sickness and high-altitude pulmonary edema (HAPE). With this in mind, we investigated whether changes in ADMA levels (Δ-ADMA) at an altitude of 4000 m can predict an individual's susceptibility to AMS or HAPE. METHODS: Twelve subjects spent two nights in a hypobaric chamber, the first night without exposure to altitude conditions and the second night at a simulated altitude of 4000 m. At identical time points during both nights (after 2, 5, and 11 hours), we determined ADMA serum levels, PAP by Doppler echocardiography and estimated hypoxia related symptoms by Lake Louise Score (LLS). RESULTS: Contrary to our initial hypothesis, subjects with a marked increase in ADMA at 4000 m showed PAP levels below the critical threshold for HAPE and were not affected by AMS. By contrast, subjects with a decrease in ADMA suffered from AMS and had PAP levels above 40 mmHg. After 2 hours of hypoxia we found a significant relationship between Δ-PAP t(2) (Spearmans ρ = 0.30, p ≤ 0.05) respectively Δ-ADMA t(2) (ρ = -0.92, p ≤ 0.05) and LLS. CONCLUSION: After 2 hours of hypoxia, the Δ-ADMA (positive or negative) can predict an LLS of >5 with a sensitivity of 80% and a specificity of 100% and can help assess the risk of an increase in PAP to more than 40 mmHg and thus the risk of HAPE (ϕ coefficient: 0.69; p ≤ 0.05).

Changes of hematocrit and hemoglobin concentration in the cold Himalayan environment in dependence on total body fluid.

INTRODUCTION: The organism is exposed to a considerable hypoxic stress at high altitude, and the well-known polyglobulia is an effective strategy to sustain oxygen delivery to the tissue at reduced saturation of hemoglobin. In general, an increasing erythropoiesis is thought to be the reason, although this increase of red blood count can be observed after a short time of altitude exposure and the parameters are expressed as water-depending concentrations. Therefore, the influence of water distribution on hemoglobin (Hb) and hematocrit (Hct) values during a long-term exposure at high altitude was investigated. MATERIALS AND METHODS: Measurements were performed in 12 mountaineers before, during, and either 7/8 or 11/12 days after a Himalaya expedition (26-29 days at 4,850 to 7,600 m altitude). Arriving at 4,850 m an initial increase of Hb and Hct was followed by a short decrease during the first week and a continuous increase during the further stay. RESULTS: In maximum, 131.3% (Hb) and 117.4% (Hct) of the starting point were reached during the fourth week at altitude after the attempt to reach the summit of Broad Peak (8,047 m). Parallel the dehydration in the beginning turned to a hyperhydration at the end of the stay (D(2)O method). DISCUSSION: Erythropoietin rose only temporarily at altitude (max. +11 +1 mU/ml serum). Upon return, Hb and Hct normalized within a few days whereas hemoglobin mass (initially 881+ 44 g, CO-Hb method) was still increased by 13% (p < 0.01). CONCLUSION: In conclusion, a hemoconcentration effect (dehydration) is the reason of the initial peak of Hb and Hct. The further increase can only partially be explained by an absolute increase of Hb and Hct caused by stimulated erythropoiesis. A shift of intravasal fluid to the interstitial space is the other main reason of the observed changes in red blood count.

Testing individual risk of acute mountain sickness at greater altitudes.

The assessment of an individual's degree of acclimatization to altitude is difficult. This is particularly applicable to military operations that have to be performed at altitude. This study describes a new and simple test that allows for the determination of an individual's risk for high-altitude illness at higher altitudes. The prediction is based on the lowest oxygen saturation (SaO2) found during an uphill run at high altitude (11,060 ft [3,371 m]), combined with the time needed to complete the run. The test results were compared against the severity of high-altitude symptomatology on the summit of Mont Blanc (15,762 ft [4,808 m]). The main outcome was the significant correlation between time as well as SaO2 and the severity of high-altitude symptomatology on the summit of Mont Blanc. The newly developed performance test allows, at a "safe" altitude, the prediction of an individual's risk of developing high altitude illness if they continue to ascend. It allows the determination of the best acclimatized subjects within a group, for example, before a military mission at greater altitude.

Auto-PEEP in the therapy of AMS in one person at 4,330 m.

BACKGROUND: The human organism is exposed to considerable hypoxic stress at high altitudes. Our intention was to investigate if a special breathing pattern with expiration against the resistance of pursed lips leads to an elevation in oxygen saturation (SaO(2)). For the first time ever, oxygen saturation was measured continuously during the initial situation, during self-performed positive end-expiratory pressure breathing (auto-PEEP) itself, and during observation afterwards. MATERIALS AND METHODS: The investigation was performed on a 33-year-old male suffering from high-altitude illness (Lake Louise Score, 9) after a 4-day rapid ascent from 350 m to 4,330 m during an expedition to Mount McKinley (6,198 m). SaO(2) was measured continuously at 4-s intervals. After a rest of 1.5 h in a dorsal recumbent position with a slightly elevated (about 15 degrees ) upper body, the patient used a wristwatch to breathe according to a special time pattern (inspiration 2 s, expiration 8 s against the resistance of pursed lips). After 30 min, breathing was then allowed without any restrictions, and the inspiration/expiration ratio was approximately 1:1. RESULTS: There was a relatively sharp rise in SaO(2) from an average of 62% to 85% within only 5 min after auto-PEEP began. This was followed by a comparable rise to values of 95% at the end of the auto-PEEP period. During normal breathing, SaO(2) decreased slowly within half an hour to values of about 70% and remained at this level. The person reported relief in symptoms and no exhaustion. Vertigo-an indication of hypocapnia caused by hyperventilation-was not observed. DISCUSSION: The 30% rise in SaO(2) and the improved saturation level after auto-PEEP are remarkable. Elevated intra-thoracal pressure may lead to a reopening of collapsed alveoli in addition to an improved gradient of alveolar-capillary pressure. In addition, a pressure-induced displacement of interstitial fluid resulting in a reduced diffusion distance may lead to improved alveolar-capillary diffusion. This would explain the slower rise in SaO(2) after 10 min of auto-PEEP and the elevated level of SaO(2) compared to the initial level before auto-PEEP. CONCLUSION: As a result of the substantial and lasting improvement in SaO(2) in combination with relief in AMS symptoms and its easy use, auto-PEEP (30 min every 2 h) can be a useful therapy option in the event of high-altitude-induced hypoxia and AMS.

EEG, ECG and oxygen concentration changes from sea level to a simulated altitude of 4000m and back to sea level.

In order to describe how high altitude affects the body during a one night stay at 4000m experiments were performed in a hypobaric chamber and compared to a study on Dachstein (mountain in Austria, 2700m). Ten subjects had to perform a reaction time task at different altitudes. The EEG and ECG were recorded simultaneously. Additionally, the oxygen saturation of the blood was measured at different altitudes and the subjects filled out a Lake Louise questionnaire that describes the degree of altitude mountain sickness (AMS). After elevation from 134m to 4000m in the hypobaric chamber heart-rate increased from 68.9bpm to 81.6bpm, RMSSD (root mean square of squared differences of adjacent heart beat intervals) decreased from 54.3ms to 33.3ms, the LF/HF ratio increased from 2.5 to 3.9 and oxygen saturation decreased to 82.7% after 11h at 4000m altitude. The Lake Louise Score (LSS) reached 3.4 after one night at 4000m. EEG beta activity between 14Hz and 18Hz was attenuated at 4000m and also after return to 134m. The results indicate that the subjects were not able to adapt to 4000m within 12h in the hypobaric chamber. Even after 1h after the return to 134m all parameters are still affected from the night at 4000m altitude. ECG and EEG changes are in line with results obtained at 2700m height at Dachstein.