Biological basis of the behavior of sick animals

The study of pain in awake animals raises ethical, philosophical, and technical problems. We review the ethical standards for studying pain in animals and emphasize that there are scientific as well as moral reasons for keeping to them. Philosophically, there is the problem that pain cannot be monitored directly in animals but can only be estimated by examining their responses to nociceptive stimuli; however, such responses do not necessarily mean that there is a concomitant sensation. The types of nociceptive stimuli (electrical, thermal, mechanical, or chemical) that have been used in different pain models are reviewed with the conclusion that none is ideal, although chemical stimuli probably most closely mimic acute clinical pain. The monitored reactions are almost always motor responses ranging from spinal reflexes to complex behaviors. Most have the weakness that they may be associated with, or modulated by, other physiological functions. The main tests are critically reviewed in terms of their sensitivity, specificity, and predictiveness. Weaknesses are highlighted, including 1) that in most tests responses are monitored around a nociceptive threshold, whereas clinical pain is almost always more severe; 2) differences in the fashion whereby responses are evoked from healthy and inflamed tissues; and 3) problems in assessing threshold responses to stimuli, which continue to increase in intensity. It is concluded that although the neural basis of the most used tests is poorly understood, their use will be more profitable if pain is considered within, rather than apart from, the body's homeostatic mechanisms.

Animal Models of Nociception

This paper is one of several in this Special Issue of the International Journal of Hyperthermia that discusses the current state of knowledge about the human health risks of hyperthermia This special issue emanated from a workshop sponsored by the World Health Organization in the Spring of 2002 on this topic It is anticipated that these papers will help to establish guidelines for human exposure to conditions leading to hyperthermia This comprehensive review of the literature makes it clear that much more work needs to be done to clarify what the thresholds for thermal damage are in humans This review summarizes the basic principles that govern the relationships between thermal exposure (temperature and time of exposure) and thermal damage, with an emphasis on normal tissue effects Methods for converting one time-temperature combination to a time at a standardized temperature are provided as well as a detailed discussion about the underlying assumptions that go into these calculations There are few in vivo papers examining the type and extent of damage that occurs in the lower temperature range for hyperthermic exposures (eg 39-42 degrees C) Therefore, it is clear that estimation of thermal dose to effect at these thermal exposures is less precise in that temperature range In addition, there are virtually no data that directly relate to the thermal sensitivity of human tissues Thus, establishment of guidelines for human exposure based on the data provided must be done with significant caution There is detailed review and presentation of thermal thresholds for tissue damage (based on what is detectable in vivo) The data are normalized using thermal dosimetric concepts Tables are included in an Appendix Database which compile published data for thresholds of thermal damage in a variety of tissues and species This database is available by request (contact MWD or PJH), but not included in this manuscript for brevity All of the studies reported are for single acute thermal exposures Except for brain function and physiology (as detailed in this issue by Sharma et al) one notes the critical lack of publications examining effects of chronic thermal exposures as might be encountered in occupational hazards This review also does not include information on the embryo, which is covered in detail elsewhere in this volume (see article by Edwards et al) as well as in a recent review on this subject, which focuses on thermal dose

Basic principles of thermal dosimetry and thermal thresholds for tissue damage from hyperthermia

Preface. Nomenclature. 1 Introduction to Fire. 1.1 Fire in History. 1.2 Fire and Science. 1.3 Fire Safety and Research in the Twentieth Century. 1.4 Outlook for the Future. 1.5 Introduction to This Book. 2 Thermochemistry. 2.1 Introduction. 2.2 Chemical Reactions. 2.3 Gas Mixture. 2.4 Conservation Laws for Systems. 2.5 Heat of Formation. 2.6 Application of Mass and Energy Conservation in Chemical Reactions. 2.7 Combustion Products in Fire. 3 Conservation Laws for Control Volumes. 3.1 Introduction. 3.2 The Reynolds Transport Theorem. 3.3 Relationship between a Control Volume and System Volume. 3.4 Conservation of Mass. 3.5 Conservation of Mass for a Reacting Species. 3.6 Conservation of Momentum. 3.7 Conservation of Energy for a Control Volume. 4 Premixed Flames. 4.1 Introduction. 4.2 Reaction Rate. 4.3 Autoignition. 4.4 Piloted Ignition. 4.5 Flame Speed, Su. 4.6 Quenching Diameter. 4.7 Flammability Limits. 4.8 Empirical Relationships for the Lower Flammability Limit. 4.9 A Quantitative Analysis of Ignition, Propagation and Extinction. 5 Spontaneous Ignition. 5.1 Introduction. 5.2 Theory of Spontaneous Ignition. 5.3 Experimental Methods. 5.4 Time for Spontaneous Ignition. 6 Ignition of Liquids. 6.1 Introduction. 6.2 Flashpoint. 6.3 Dynamics of Evaporation. 6.4 Clausius-Clapeyron Equation. 6.5 Evaporation Rates. 7 Ignition of Solids. 7.1 Introduction. 7.2 Estimate of Ignition Time Components. 7.3 Pure Conduction Model for Ignition. 7.4 Heat Flux in Fire. 7.5 Ignition in Thermally Thin Solids. 7.6 Ignition of a Thermally Thick Solid. 7.7 Ignition Properties of Common Materials. 8 Fire Spread on Surfaces and Through Solid Media. 8.1 Introduction. 8.2 Surface Flame Spread - The Thermally Thin Case. 8.3 Transient Effects. 8.4 Surface Flame Spread for a Thermally Thick Solid. 8.5 Experimental Considerations for Solid Surface Spread. 8.6 Some Fundamental Results for Surface Spread. 8.7 Examples of Other Flame Spread Conditions. 9 Burning Rate. 9.1 Introduction. 9.2 Diffusive Burning of Liquid Fuels. 9.3 Diffusion Flame Variables. 9.4 Convective Burning for Specific Flow Conditions. 9.5 Radiation Effects on Burning. 9.6 Property Values for Burning Rate Calculations. 9.7 Suppression and Extinction of Burning. 9.8 The Burning Rate of Complex Materials. 9.9 Control Volume Alternative to the Theory of Diffusive Burning. 9.10 General Considerations for Extinction Based on Kinetics. 9.10.1 A demonstration of the similarity of extinction in premixed and diffusion flames. 9.11 Applications to Extinction for Diffusive Burning. 10 Fire Plumes. 10.1 Introduction. 10.2 Buoyant Plumes. 10.3 Combusting Plumes. 10.4 Finite Real Fire Effects. 10.5 Transient Aspects of Fire Plumes. 10.5.1 Starting plume. 10.5.2 Fireball or thermal. 11 Compartment Fires. 11.1 Introduction. 11.2 Fluid Dynamics. 11.3 Heat Transfer. 11.4 Fuel Behavior. 11.5 Zone Modeling and Conservation Equations. 11.6 Correlations. 11.7 Semenov Diagrams, Flashover and Instabilities. 12 Scaling and Dimensionless Groups. 12.1 Introduction. 12.2 Approaches for Establishing Dimensionless Groups. 12.3 Dimensionless Groups from the Conservation Equations. 12.4 Examples of Specific Correlations. 12.5 Scale Modeling. Appendix. Flammability Properties. Archibald Tewarson. Index.

Fundamentals of Fire Phenomena

The extent of thermal destruction of tissue by visible and near-infrared lasers is governed by heat deposition in the tissue, heat transfer, and temperature-dependent rate reactions. Often the thermal response has been analyzed by linear models with constant coefficients that presume exponential absorption of the laser irradiation with depth. However, for weakly absorbing tissues, light scattering dominates the optical properties. These properties may be altered by thermal damage of the tissue. Also, thermal properties for tissue vary with temperature and water content. Typical therapeutic laser irradiations vaporize water in the tissue causing sharp increases in temperature beyond 100°C, and continued irradiation causes ablation of the tissue. Models for all these events are discussed.

The thermal response of laser irradiated tissue

Sites on the volar surfaces of the forearms of human subjects were blackened with India ink and exposed to thermal irradiances of from 50 to 400 mcal/cm2 sec. The exposure time and skin temperature...

Relationship between pain and tissue damage due to thermal radiation.

: Thermal protection rating systems for fabrics, based on pain and blister effects in human skin, are considered in terms of: (1) precise evaluations applicable to any known temperature-time pattern, and (2) simple laboratory procedures to provide a universally useful standard rating system The first system which is more comprehensive is difficult and requires computer operations routinely; the second, described in detail, offers a rating system which is simple, directly related to pain and blister parameters, and may be understood by the uninitiated as well as those knowledgeable in the field

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Method and rating system for evaluation of thermal protection.

: Prediction of dermal injury resulting from exposure to thermal energy of any given intensity and duration depends entirely upon the resultant skin temperature-time history. Means are now available for assessing heat transfer by low temperature radiation, convection and conduction to the bare skin and through thin protective coverings of known physical properties. However, thermal effects of nuclear detonations constitute a special problem because much of the radiation lies in the visible range where the optical properties of the skin and its coverings, if any, greatly influence the heating pattern. Blackening of the skin eliminates effects due to its optical properties but enhances the ever-present variations in the thermal 'constants' of the skin. The present report describes the utilization of a mathematical equation and computer techniques for extracting these variations from empirical data obtained at relatively low levels of radiation (<0.5 Cal/sq cm sec.), and applying extrapolations of these values in calculations of temperature-time histories at higher levels of irradiance where empirical data are lacking. This procedure is subject to validation by experimentation within a limited range of exposures. If validation is achieved in the blackened skin then the entire system may be utilized in the determination of optical properties of unblackened skin.

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Mathematical model of skin exposed to thermal radiation.

Heat is transferred through fabrics by convection, conduction, and radiation and, under certain circumstances, by vaporization. Each mode is subject to different physical principles, but the effect of the total heat absorbed by underlying skin is the same: If the resultant skin temperature rise is sufficiently high and maintained sufficiently long, injury results. The extent of injury is predicted under certain controlled conditions, and these conditions may be used to disclose protection principles appropriate to each mode of transfer.

Alice M. Stoll

Papers

Relationship between pain and tissue damage due to thermal radiation.

Method and rating system for evaluation of thermal protection.

Mathematical model of skin exposed to thermal radiation.

Heat transfer through fabrics as related to thermal injury.

Study of thermocouples as skin thermometers.