Classification of Causes

Another term failure mode inherited from safety engineering is often used to denote an unintended condition of a system. Some would argue that failure mode and cause are synonymous but from time to time they are used in a manner which it subtly different. Consider a failure of the power supply to an application server. The failure modes might be set out as no voltage, voltage too high, voltage too low. To some extent the term implies that each potential failure mode is discrete and that collectively all possible eventualities are addressed (as with this example). 

An analysis of a system s failure modes may determine that some could trigger a hazard - these failure modes are safety-related and are likely to represent causes. In contrast those which would not typically lead to harm will be not safety-related . Depending on the relative degree of risk it may be necessary to justify the reason for a failure mode not being safety-related. 

Note that Failure mode has also been adopted outside of health in the naming of a commonly used formal method for identifying hazards, Failure Mode and Effects Analysis described in Sect. 13.6.1. 

An alternative (or additional) approach to cause classification is to consider the impact on the clinical data which resides within the system - after all it is ultimately the information and how it is used which gives rise to harm. By examining how information is generated and presented we can derive a series of failure modes (or at least categories of failure modes) which have the potential to impact care. Depending on how granular one decides to cast the hazards and causes, the classification system can be used to drive out both. 

Such a classification framework is presented in the following sections. The categories are not based on current standards or wider literature but rather from the author s personal field experience. They are not necessarily mutually exclusive or even complete but they offer a starting point to be used alongside other methods. 

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The development of medical codes has in fact been an international and US success story that shows bureaucracy at its best. The use of medical codes dates as far back as 1893, when a French physician, Jacques Bertillon, introduced the Bertillon Classification of Causes of Death at the International Statistical Institute in Chicago. A number of countries quickly adopted Dr. Bertillon s system, and in 1898, the American Public Health Association (APHA) recommended that the registrars of Canada, Mexico, and the United States also adopt it. The APHA also recommended revising the system every 10 years to ensure that the system remained current with medical practice advances. As a result the first international conference to revise the International Classification of Causes of Death convened in 1900, with revisions occurring every 10 years thereafter. The sixth revision, included morbidity (serious disease) and mortality (fatality) conditions, and its title was modified, to reflect the changes, to Manual of International Statistical Classification of Diseases, Injuries and Causes of Death (ICD). 

The approach to the incident investigation is integrated in three senses. First, it integrates our assumptions about structure of investigated process. Second, it integrates different classifications of causes and shows their interrelations. Third, it integrates two types of incident investigation method. 

These figures show that the highest level of bus accidents as a percentage of total road accidents was in Tanzania, and the highest level of fatalities per bus accident was in Nepal. Three main classifications of causes for bus accidents in Tanzania are shown in Figure 10.3 [20,28]. These classifications are human factors, vehicle condition, and external factors. The percentage breakdowns for these three classifications were 76%, 17%, and 7%, respectively. Clearly, the main cause of bus accidents in Tanzania was human error. 

Free phenol is a major concern in the manufacture of novolac resins. This is true for several reasons. The strongest drivers are probably EPA classification of phenol as a Hazardous Air Pollutant and worker safety concerns. However, free phenol also has significant technical effects on such parameters as melt flow characteristics. In this role, free phenol may undermine the desired effects of a molecular weight design by increasing flow beyond the desired point. Since free phenol is often variable, the effects on flow may also cause variation in product performance from batch to batch. Fig. 18 shows the effects of free phenol on the flow across a series of molecular weights. Free phenol contents between 1 and 10% are commonly seen. In recent years, much work has been aimed at reducing the free phenol. 

The categorization set out in Figure 2.6 is a broad classification of the causes of human failures that can be related to the SRK concepts discussed in the last section. The issue of violations will be addressed later in Section 2.7.1.1. The distinction between slips and mistakes was first made by Norman (1981). 

All important factor in assessing tlie causes and effects of fires is tlie beluivior of a fire s flmne. Knowledge of a flame s spreading rate and heat intensity can reduce fire liazard potentials and fire damage. The classifications of flame behavior are ... 

Having discussed tlie fundamental cliaracteristics of fires in general and tlie different types of fire, we now e.xamine more closely fire accidents tliat occur in process pkuits. Specifically, we review plant fire classifications, sources, causes, damage potentials, and detection and protection systems. 

Median Lethal Dose (LD) The statistically derived single dose of a chemical that can be c.xpected to cause death in 50% of a given population of organisms under a defined set of experimental conditions. This figure has often been used to classify and compare toxicity among chemicals but its value for this purpose is doubtful. One commonly used classification of this kind is as follows ... 

The classification given in Table 1.2 is based on the various forms that corrosion may take, but the terminology used in describing corrosion phenomena frequently places emphasis on the environment or cause of attack rather than the form of attack. Thus the broad classification of corrosion reactions into wet or dry is now generally accepted, and the nature of the process is frequently made more specific by the use of an adjective that indicates type or environment, e.g. concentration—cell corrosion, crevice corrosion, bimetallic corrosion and atmospheric corrosion. 

Soil surveys relating to construction work require samples from at least the depth of excavation water seepage may cause cross-contamination of land. Some guidelines for the classification of contaminated soils are summarized in Table 13.11 some materials are difficult to dispose of safely on land (Table 13.12). 

A classification of the causes of hypoxia is presented in Table II. Only anoxic anoxia (due to decreased ambient oxygen or to respiratory disease) has arterial P02 values decreased (with accompanying decreased venous P02 values). However, hemic, ischemic, and histoxic hypoxia may be present (termed non-ventilatory hypoxia) with normal arterial P02 values. Thus the best evaluation of hypoxia is an analysis of both arterial and venous... 

The classification of a new object u into one of the given classes is determined by the value of the potential function for that class in u. It is classified into the class which has the largest value. A one-dimensional example is given in Fig. 33.15. Object u is considered to belong to K, because at the location of u the potential value of K is larger than that of L. The boundary between two classes is given by those positions where the potentials caused by these two classes have the same value. The boundaries can assume irregular values as shown in Fig. 33.3. 

Urinary incontinence can result from abnormalities within (intrinsic to) and outside of (extrinsic to) the urinary tract. Within the urinary tract, abnormalities may occur in the urethra (including the bladder outlet and urinary sphincters), the bladder, or a combination of both structures. Focusing on abnormalities in these two structures, a simple classification scheme emerges for all but the rarest intrinsic causes of UI. Accurate diagnosis and classification of UI type is critical to the selection of appropriate drug therapy. 

Pneumonia is inflammation of the lung with consolidation. The cause of the inflammation is infection, which can result from a wide range of organisms. There are five classifications of pneumonia community-acquired, aspiration, hospital-acquired, ventilator-associated, and health care-associated. Patients who develop pneumonia in the outpatient setting and have not been in any health care facilities, which include wound care and hemodialysis clinics, have community-acquired pneumonia (CAP). Aspiration is of either oropharyngeal or gastrointestinal contents. Hospital-acquired pneumonia (HAP) is defined as pneumonia that occurs 48 hours or more after admission.1,2 Ventilator-associated pneumonia (VAP) requires endotracheal intubation for at least 48 to 72 hours before the onset of... 

Major breaks in surgical technique may cause the classification of the operation to change and require adjustments in antimicrobial prophylaxis. 

All methods of surface analysis are based on primary particle irradiation of analyzed samples, causing primary flux disturbance or emission of secondary particles from the surface. Table 2 presents a classification of the most popular methods of analysis based on... 

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