[Tracheal rupture--a rare and dramatic emergency]. / Der Trachealabriss--Ein seltener und dramatischer Notfall.

A tracheal tear requires fast and proper treatment. A 55-year-old man working in a sewage pipe slipped and hit his neck on the edge of a concrete ring. The patient showed the following symptoms: cervical bruising, neck emphysema and increasing dyspnea. After several unsuccessful attempts to intubate the patient, a necklace incision was made immediately at the scene, under the suspected diagnosis of a torn trachea. A finger was used to look for the lower tracheal stump lying in the mediastinum. The lower stump was then intubated. In the hospital, an end-to-end anastomosis of the trachea as well as tracheotomy were performed on the patient. Because of the fracture of the larynx, an endolaryngeal stent was used to stabilize the lumen. Due to an injury to both laryngeal nerves, the patient suffered from dysphagea, whispered speech and dyspnea on minimal exertion as long-term side-effects. A lateralization of the vocal cord was made eight months later. Because of the quick assessment of the situation and proper treatment of the patient at the site of the accident, the patient was able to survive the injury.

[Critical infusion incident caused by incorrect use of a patient-controlled analgesia pump]. / Infusionszwischenfall durch fehlerhafte Anwendung einer PCA-Pumpe.

We report on the case of a 17-year-old male patient who received a PCA pump after nephrectomy for postoperative analgesia. The syringe of the PCA pump was filled with 50 mg morphine and positioned about 25 cm above the heart. Since the piston of the syringe was not bolted while the pump was switched off, an unnoticed accidental evacuation of the whole content of the syringe into the intravenous line of the patient occurred because of gravity. This problem exists not only with PCA pumps, but can happen with syringe pumps in general. The incident, which can only be explained by strongly reduced venous pressure, was detected by chance. No harm resulted for the patient, but under different conditions it could have been lethal. This critical incident was caused by various factors: incorrect application in combination with insufficient experience or training, stress, inadequate handing-over of the patient and a lack of arrangements and instructions for procedures in routine situations. Suggestions for preventing such dangerous critical incidents are made and discussed. In particular, an algorithm for the correct procedure when inserting or changing the syringe of a syringe pump is presented.

[Early contributions from Erlangen to the theory and practice of general anesthesia with ether and chloroform. 2. The animal experiments of Ernst von Bibra and Emil Harless]. / Frühe Erlanger Beiträge zur Theorie und Praxis der Ather- und Chloroformnarkose. Teil 2. Die tierexperimentellen Untersuchungen von Ernst von Bibra und Emil Harless.

Just three months after the first application of sulphuric ether to a patient in german-speaking countries the monography Die Wirkung des Schwefeläthers in chemischer und physiologischer Beziehung was published. In this book Ernst von Bibra and Emil Harless presented their experimental research on the effects of ether on humans and compared it to those on animals. The contents of the book are described. The authors "Theory on the action of ether" will be discussed in the context of contemporary criticism. Their hypothesis affected the discussion on the mechanisms of anaesthetic action up to the twentieth century.

[Disconnections in the breathing system]. / Die diskonnektion im Beatmungssystem.

Modern anaesthesia is considered as relatively safe. Nevertheless, incidents happen which result in harm for the patient. Incidents which cause hypoxia are especially grave. One of the most frequent incidents in anaesthesia and intensive care is of this nature: disconnection in the ventilatory apparatus. DEFINITION. Unintentional separation--partial or complete--of two manually connected components in a ventilatory apparatus. INCIDENCE. About 5% of incidents during narcosis are likely to be caused by disconnections in the ventilatory apparatus. CAUSES. Axially directed force of as little as 15 N may cause disconnection. It may result from active or passive movements of the patient, high pressure in the apparatus or unintentional traction on the breathing hoses. Conically moulded couplings are mostly used for connections. The stability of these so-called taper fit connections is decisively determined by the effort and technique of the user when coupling the two components. On the other hand the use of unsuitable materials may lead to an inadequate connection. Another possibility is damage by mechanical, chemical or thermal influences. Additionally, differences from the standard specifications of the components may occur. MOST COMMON SITES. Disconnections are found predominantly (in around 70% of cases) at the connection between the tube connector and the adapter or Y-piece. This joint represents a weak point, especially during surgical treatment in the head and neck region, when it cannot be controlled and in most cases is not accessible by hand because it is covered. CONSEQUENCES. The consequences of disconnection depend on different factors: relaxation of the patient, depth of narcosis, duration and localization of the disconnection, constitution and current oxygenation of the patient. An undetected disconnection may lead to hypoxia within a few minutes and then to irreversible brain damage and finally death. Serious incidents have been decreased in number in recent years by the application of improved monitoring procedures. DETECTION. Measurements of airway pressure, minute volume and expiratory CO2 by capnography ensure rapid detection of disconnections using appropriate adjustments of alarm limits. A disconnection may not be detected by pulse oximetry before a latent period, i.e. after a significant decrease of the oxygenation saturation of the patient. PREVENTION. Standardized specifications exist for technical dimensions of connectors, but "reliability" of connectors has not yet been defined in terms of technical requirements. Disconnection is currently prevented by application of various mechanical methods and devices, not all of which fulfil the conditions required of an ideal system: (1) Simple and fast connection ("single-handed operation"); (2) connection independent of the torsional angle between the two parts; (3)safe connection which cannot be detached unintentionally; (4) 360 degrees torsion possible after connection; (5) tight connection; (6) fast and easy deliberate disconnection; (7) intentional disconnection possible independent of the torsional angle between the two parts; (8) compatibility with conventional systems; (9) user's comfort and convenience (when ventilating with mask, etc.) as good as with conventional systems. DISCONNECTION OR EXTUBATION? There is a heated debate on the theme "disconnection". Some authors suspect that the development of reliable locking connections could lead to an increased frequency of unwanted extubations. To prevent unwanted extubations with consequent harm to patients, some developers propose a mechanical fuse, i.e. a defined site of fracture with an additional adequate monitoring device for reliable detection of disconnections. CONCLUSIONS. There are many approaches to the "disconnection" problem. In principle the problem requires a fundamental decision for each connection in the breathing system: safe prevention of disconnection (lock connection) or reliable mechanical f

[Measurement of O2 concentration in the fresh gas supply of the Kuhn system]. / O2-Konzentrationsmessung in der Frischgaszufuhr des Kuhn-Systems.

To accomplish the requirement of inspiratory O2-concentration measurement on the Ayre-T-piece modified by Kuhn we developed a special device. It is mounted in the fresh gas hose and then connected to the sensor of the O2-concentration measuring and warning instrument of the circle system.

[Definition of a leak model and derivation of formulas for quantifying the accompanying leak surfaces in the anesthetic system]. / Definition eines Leckagemodells und Herleitung von Formeln zur Quantifizierung der zugehörigen Leckflächen im Narkosesystem.

Our intention was to conceive a simple model for the evaluation of well-defined leakages in the anesthetic breathing system. Utilization of any model requires a formula to calculate the corresponding leakage surfaces. METHOD. The leak is defined as the projection of a circle (radius r) onto the surface of a cylinder (radius R) in which anesthetic gas is flowing. If we remove the leakage surface from the cylinder and flatten it out this produces neither a circular nor an elliptic shape. We will develop an expression for the leakage surface depending on the two radii, r and R, in a two-dimensional coordinate system. RESULTS. Formulas (3), (4) and (5) can be used to compute leakage areas for our model. An analytic solution of the equations is impossible by the application of calculus, but a PC program for numeric integration can yield values with a sufficient degree of accuracy. Some results for well-defined leakages in breathing tubes (R = 11 mm) are shown. These show that the difference between the leakage area and the projected circle (radius r) can practically be neglected for some values of r. CONCLUSION. Leakages in most anesthetic breathing systems cause some gas loss. The main causes are leaking plug connections and screw joints. Damage to the breathing tubes or bellows is less significant. Part of the tidal volume will disperse into the environment via the leak. This might be hazardous for the patient because the breathing volume and inspiratory oxygen concentration are reduced and for the operating team because of air pollution. To examine how such parameters as flow, compliance and resistance cause loss of pressure and volume and variations in gas concentration in the case of leakages an appropriate model of practical use is needed. Application of the formulas derived from our model makes it possible to compare measurements gained from studying the impacts of leakages in cylindrical tubes of different diameters. By experimental research of pressure and volume loss we intend to gather reliable information that will allow us to make proper recommendations for efficient setting of the pressure disconnection alarm.