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PubMed2006

Entropy indices vs the bispectral index for estimating nociception during sevoflurane anaesthesia.

BACKGROUND: It is now possible to acquire and process raw EEG and frontal EMG signals to produce two spectral-entropy-based indices (response entropy and state entropy) reflective of analgesic and hypnotic levels during general anaesthesia (with the Datex-Ohmeda S/5 Entropy Module, Datex-Ohmeda, Helsinki, Finland). However, there are no data available on the accuracy of the Entropy Module in estimating nociception during sevoflurane anaesthesia. METHODS: Forty female patients were enrolled in the present study. Each patient was allocated randomly to one of four end-tidal sevoflurane concentration (ET(sev)) groups (1.3, 1.7, 2.1 or 2.5%). A BIS Sensor (Aspect Medical Systems, Newton, MA) and an Entropy Sensor (Datex-Ohmeda) were applied side-by-side to the forehead. The bispectral index (A-2000 BIS Monitor, version 3.4, Aspect Medical Systems), response entropy, state entropy and patient movement were observed after electrical stimulation (20, 40, 60 and 80 mA, 100 Hz, 5 s) and after skin incision during sevoflurane anaesthesia (1.3, 1.7, 2.1 or 2.5%). Accuracy of the EEG variables in differentiating the intensity of electrical stimulation was estimated by the prediction probability (P(K)) values. RESULTS: Response entropy and state entropy [median, (range)] before skin incision were significantly lower in patients who did not move [29 (15-41) and 24 (14-41)] than in those that did [38 (24-53) and 37 (24-52)], but there was no significant difference in BIS. All EEG variables increased significantly (P<0.0001 for all) with increases in the intensity of electrical stimulation. The difference between response entropy and state entropy increased with increases in the electrical stimulation (P<0.0001). However, no EEG variables could differentiate the intensity of the electrical stimulations accurately because of low P(K)-values (P(K)<0.8). CONCLUSION: Noxious stimulation increased the difference between response entropy and state entropy. However, an increase in the difference does not always indicate inadequate analgesia and should be interpreted carefully during anaesthesia.

Adult↗

PubMed2005

Spectral entropy monitoring is associated with reduced propofol use and faster emergence in propofol-nitrous oxide-alfentanil anesthesia.

BACKGROUND: This multicenter study evaluated the effect of a new depth of anesthesia-monitoring device based on time-frequency-balanced spectral entropy of electroencephalogram monitoring (GE Healthcare Finland, Helsinki, Finland) on consumption of anesthetic drugs and recovery times after anesthesia. METHODS: The study was a prospective, randomized, single-blind study performed in six hospitals in Finland, Sweden, and Norway. After institutional review board approval and written informed consent from each patient, the patients were randomly allocated to anesthesia with entropy values either shown (entropy group) or not shown (control group). Anesthesia was maintained with propofol, nitrous oxide, and alfentanil. In the entropy group, propofol was given to keep the state entropy value between 45 and 65, and alfentanil was given to keep the state entropy-response entropy difference below 10 units and heart rate and blood pressure within +/-20% of the baseline values. The control group patients were anesthetized to keep heart rate and blood pressure within +/-20% of the baseline values. Statistical methods included Mann-Whitney U test and unpaired t tests. RESULTS: A total of 368 patients were studied. In the entropy group, entropy values were higher during the whole operation and especially during the last 15 min (P < 0.001). Consequently, propofol consumption was smaller in the entropy group during the whole anesthesia period (P < 0.001) and especially during the last 15 min (P < 0.001). This shortened the time delay in the early recovery parameters in the entropy group. CONCLUSION: Entropy monitoring assisted titration of propofol, especially during the last part of the procedures, as indicated by higher entropy values, decreased consumption of propofol, and shorter recovery times in the entropy group.

Adult↗

PubMed2006

Entropy is more resistant to artifacts than bispectral index in brain-dead organ donors.

OBJECTIVE: To evaluate the usefulness of entropy and the bispectral index (BIS) in brain-dead subjects. DESIGN AND SETTING: A prospective, open, nonselective, observational study in the university hospital. PATIENTS AND PARTICIPANTS: 16 brain-dead organ donors. INTERVENTIONS: Time-domain electroencephalography (EEG), spectral entropy of the EEG, and BIS were recorded during solid organ harvest. MEASUREMENTS AND RESULTS: State entropy differed significantly from 0 (isoelectric EEG) 28%, response entropy 29%, and BIS 68% of the total recorded time. The median values during the operation were state entropy 0.0, response entropy 0.0, and BIS 3.0. In four of 16 organ donors studied the EEG was not isoelectric, and nonreactive rhythmic activity was noted in time-domain EEG. After excluding the results from subjects with persistent residual EEG activity state entropy, response entropy, and BIS values differed from zero 17%, 18%, and 62% of the recorded time, respectively. Median values were 0.0, 0.0, and 2.0 for state entropy, response entropy, and BIS, respectively. The highest index values in entropy and BIS monitoring were recorded without neuromuscular blockade. The main sources of artifacts were electrocauterization, 50-Hz artifact, handling of the donor, ballistocardiography, electromyography, and electrocardiography. CONCLUSION: Both entropy and BIS showed nonzero values due to artifacts after brain death diagnosis. BIS was more liable to artifacts than entropy. Neither of these indices are diagnostic tools, and care should be taken when interpreting EEG and EEG-derived indices in the evaluation of brain death.

Artifacts↗

PubMed2005

Performance of entropy and Bispectral Index as measures of anaesthesia effect in children of different ages.

BACKGROUND: Entropy and Bispectral Index (BIS) have been promoted as EEG-based anaesthesia depth monitors. The EEG changes with brain maturation, but there are limited published data describing the characteristics of entropy in children, and some data suggest that BIS is less reliable in young children. The aim of this study was to compare the performance of entropy as a measure of anaesthetic effect in different age groups. The performance of entropy was compared with BIS. METHODS: Fifty-four children receiving a standard sevoflurane anaesthetic for cardiac catheter studies were enrolled. The entropy and BIS were recorded pre-awakening and at 1.5%, 2% and 2.5% steady-state end-tidal sevoflurane concentrations. For analysis children were divided into four age groups: 0-1 yr, 1-2 yr, 2-4 yr and 4-12 yr. RESULTS: The pre-awakening values were obtained in 46 children. The median pre-awakening values for entropy and BIS varied significantly across ages with the values being lowest in the 0-1 yr age group (response entropy: 45 vs 84, 87 and 89, P=0.003; state entropy: 36 vs 78, 74 and 77, P=0.009; BIS: 56 vs 78, 76.5 and 72, P=0.02). Values were recorded at all three sevoflurane concentrations in 48 children. Compared with older groups, the 0-1 yr age group had the least significant difference in BIS and entropy when compared among different sevoflurane concentrations. The calculated sevoflurane concentrations to achieve mid-scale values of entropy and BIS were highest in the 1-2 yr age group, lower in the 0-1 yr age group and progressively lower in the 2-4 and 4-12 yr age groups. CONCLUSIONS: For both entropy and BIS the measure of anaesthetic effect was significantly different for children aged <1 yr compared with older children. There was no difference in performance of entropy and BIS. Both should be used cautiously in small children.

Aging↗

PubMed2026

Tissue-Level Transcriptomic Entropy Reveals Organ-Specific Aging Patterns and Predicts Cancer Progression.

Although aging and cancer share complex molecular mechanisms, distinguishing causative factors from byproducts remains challenging. Here, we investigated the role of tissue transcriptomic entropy-a measure of transcriptional disorder-in aging and cancer processes by analyzing RNA-sequencing data from over 25,000 samples from human and mouse tissues. We found that entropy changes during aging are highly tissue-specific, with some tissues showing increased entropy while others exhibit decreased or stable entropy levels. Moreover, transcriptomic entropy strongly correlates with age-related processes, showing positive associations with proliferation, cellular senescence, somatic mutation burden, and cellular reprogramming, whereas it negatively correlates with stemness. In cancer, we observed that primary tumors generally display higher entropy than normal tissue, with its levels further increasing in metastatic stages. Cancer treatment modulated entropy patterns in multiple contexts, with changes suggesting a role for transcriptional complexity in tumor plasticity and therapy resistance. Elevated entropy levels predicted poor survival outcomes in multiple cancer types, suggesting its potential as a prognostic marker. Furthermore, differential expression analysis revealed that entropy-associated genes are enriched in developmental processes and depleted in metabolic pathways, indicating a possible link to cellular dedifferentiation. Finally, we found increased entropy in various age-related disorders beyond cancer, suggesting that transcriptomic entropy may be a common feature in age-related diseases. Our findings establish transcriptomic entropy as a fundamental parameter in aging and cancer progression, offering new insights into disease mechanisms.

Humans↗

PubMed2004

Entropy and bispectral index during anaesthesia in children.

Entropy is a new EEG based technology developed as a measure of depth of anaesthesia. The Entropy algorithm quantifies the degree of disorder in the EEG. During anaesthesia the disorder of the EEG, or entropy, falls. Entropy is independent of absolute frequency or amplitude of the EEG. This may make it suitable for paediatric anaesthesia. In this prospective observational blinded study we recorded the Entropy and Bispectral Index in 23 children undergoing general anaesthesia with isoflurane and nitrous oxide, supplemented with peripheral nerve blockade. We recorded Entropy at several times during anaesthesia, pre-awakening and 1-minute post-awakening. Entropy pre-awakening and 1 minute after awakening was compared to a value during anaesthesia in three age groups; less than one-year-old (infants), one to five years (toddlers) and five to twelve years (children). The correlation between BIS and Entropy was also calculated. Entropy post-awakening was higher than during anaesthesia for all age groups. Entropy pre-awakening was higher than during anaesthesia for the children and toddlers. This was not as apparent in infants. There was a strong correlation between BIS and Entropy for children and toddlers. The correlation was less for infants. This study demonstrates that, in children, Entropy is lower during anaesthesia when compared to awake values. Further evaluation in the paediatric population is worthwhile.

Algorithms↗

PubMed2002

[Maximum entropy principle and population genetic equilibrium].

A general mathematic model of population genetic equilibrium was constructed based on the maximum entropy principle. We proved that the maximum entropy probability distribution was equivalent to the Hardy-Weinberg equilibrium law. A population reached genetic equilibrium when the genotype entropy of the population reached the maximal possible value. In information theory, the entropy or the information content is used to measure the uncertainty of a system. In population genetics, we can use entropy to measure the uncertainty of the genotype of a population. The agreement of the maximum entropy principle and the hardy-Weinberg equilibrium law indicated that random crossing is an irreversible process, which increases the genotype entropy of the population, while inbreeding and selection decrease the genotype entropy of the population. In animal or plant breeding, we often use selection and/or inbreeding to decrease the entropy of a population, and use intercrossing to increase the entropy of the population. In this point of view, breeding is actually regulating the entropy of population. By applying the basic principle of informatics in population genetics, we revealed the biological significance of the genotype entropy and demonstrated that we can work over population genetic problems with the principles and methods of informatics and cybernetics.

Animals↗

PubMed2000

Binding of small organic molecules to macromolecular targets: evaluation of conformational entropy changes.

The conformational entropy is the largest unfavorable effect that must be overcome during protein folding and binding. Accurate predictions of protein stability and binding affinity require a precise way of evaluating conformational entropy changes. Previously we implemented a computational approach aimed at estimating conformational entropy changes in peptides (D'Aquino et al., Proteins 1996;25:143-156; Lee et al., Proteins 1994;20:68-84). Here we extend this approach to estimate conformational entropy changes in molecules of pharmaceutical interest. Calculations were carried out for a set of 36 small organic molecules containing one dihedral angle and different functional groups around the central bond. Entropy changes were calculated for these molecules as the difference between the entropy of the free molecule and the entropy of the molecule when it is constrained to occupy a particular range of dihedrals, as in the bound state. Entropy changes for binding of larger molecules can be estimated assuming additivity on a per bond basis. Thus, the results presented here provide an initial toolbox of conformational entropy values in the form of a lookup table that can be used in the estimation of entropy changes associated with binding processes of more complex molecules. To facilitate their use, the values were parameterized in terms of the number and type of atoms neighboring each specific dihedral. Both methods, lookup table and parameterized equation, provide a very fast way of evaluating conformational entropy changes, making them suitable for fast screening algorithms.

Alanine↗

PubMed2005

Time-dependent entropy evolution in microscopic and macroscopic electromagnetic relaxation.

This paper is a study of entropy and its evolution in the time and frequency domains upon application of electromagnetic fields to materials. An understanding of entropy and its evolution in electromagnetic interactions bridges the boundaries between electromagnetism and thermodynamics. The approach used here is a Liouville-based statistical-mechanical theory. I show that the microscopic entropy is reversible and the macroscopic entropy satisfies an theorem. The spectral entropy development can be very useful for studying the frequency response of materials. Using a projection-operator based nonequilibrium entropy, different equations are derived for the entropy and entropy production and are applied to the polarization, magnetization, and macroscopic fields. I begin by proving an exact theorem for the entropy, progress to application of time-dependent entropy in electromagnetics, and then apply the theory to relevant applications in electromagnetics. The paper concludes with a discussion of the relationship of the frequency-domain form of the entropy to the permittivity, permeability, and impedance.

Journal Article↗

PubMed2005

[Comparison of the bispectral index and spectral entropy in gynecological surgery].

OBJECTIVES: Spectral entropy quantifies variations in cortical electrical activity measured by electroencephalography and frontal activity measured by electromyography. The aim of this study, in the context of general anesthesia, was to compare bispectral index values with the two components of spectral entropy: state entropy and response entropy. MATERIAL AND METHODS: Sixteen women (ASA I-II) undergoing gynecological surgery were enrolled. The bispectral index was maintained between 40 and 50 for all patients. Both sensors, for monitoring the bispectral index and spectral entropy, were placed on each patient. Simultaneous readings were recorded at the following moments: operating room arrival, induction, relaxation, intubation, switching on the vaporizer, start of surgery, traction of the intestinal mesenteries and maneuvering of the electric scalpel, switching off the vaporizer, end of surgery, during cough, extubation, and eye opening. The data sets were subjected to analysis of variance, and the intraclass correlation coefficient (ICC) was used to analyze agreement. RESULTS: Differences between mean values of the bispectral index, state entropy and response entropy were observed at operating room arrival, intubation, and induction. Differences when the patient awakened from anesthesia were observed only between the bispectral index and response entropy, on the one hand, and state entropy on the other. There was no agreement (ICC<0.7) upon operating room arrival, maneuvering the electric scalpel, or awakening from anesthesia. CONCLUSION: The bispectral index, state entropy, and response entropy show good agreement during recordings that reflect the effects of anesthesia. The differences observed at baseline and upon awakening can be attributed to frontal electromyographic activity. Distinguishing cortical electrical activity from frontal electromyographic activity may provide additional information in these situations.

Anesthesia, General↗

PubMed1996

The magnitude of the backbone conformational entropy change in protein folding.

The magnitude of the conformational entropy change experienced by the peptide backbone upon protein folding was investigated experimentally and by computational analysis. Experimentally, two different pairs of mutants of a 33 amino acid peptide corresponding to the leucine zipper region of GCN4 were used for high-sensitivity microcalorimetric analysis. Each pair of mutants differed only by having alanine or glycine at a specific solvent-exposed position under conditions in which the differences in stability could be attributed to differences in the conformational entropy of the unfolded state. The mutants studied were characterized by different stabilities but had identical heat capacity changes of unfolding (delta Cp), identical solvent-related entropies of unfolding (delta Ssolv), and identical enthalpies of unfolding (delta H) at equivalent temperatures. Accordingly, the differences in stability between the different mutants could be attributed to differences in conformational entropy. The computational studies were aimed at generating the energy profile of backbone conformations as a function of the main chain dihedral angles phi and phi. The energy profiles permit a direct calculation of the probability distribution of different conformers and therefore of the conformational entropy of the backbone. The experimental results presented in this paper indicate that the presence of the methyl group in alanine reduces the conformational entropy of the peptide backbone by 2.46 +/- 0.2 cal/K. mol with respect to that of glycine, consistent with a 3.4-fold reduction in the number of allowed conformations in the alanine-containing peptides. Similar results were obtained from the energy profiles. The computational analysis also indicates that the addition of further carbon atoms to the side chain had only a small effect as long as the side chains were unbranched at position beta. A further reduction with respect to Ala of only 0.61 and 0.81 cal/K. mol in the backbone entropy was obtained for leucine and lysine, respectively. beta-branching (Val) produces the largest decrease in conformational entropy (1.92 cal/K.mol less than Ala). Finally, the backbone entropy change associated with the unfolding of an alpha-helix is 6.51 cal/K.mol for glycine. These and previous results have allowed a complete estimation of the conformational entropy changes associated with protein folding.

Alanine↗

PubMed2004

Time-frequency balanced spectral entropy as a measure of anesthetic drug effect in central nervous system during sevoflurane, propofol, and thiopental anesthesia.

BACKGROUND: Time-frequency balanced spectral entropy of electroencephalogram (EEG) and frontal electromyogram (FEMG) is a novel measure of hypnosis during anesthesia. Two Entropy parameters are described: Response entropy (RE) is calculated from EEG and FEMG; and State Entropy (SE) is calculated mainly from EEG. This study was performed to validate their performance during transition from consciousness to unconsciousness under different anesthetic agents. METHODS: Response entropy, SE [S/5 Entropy Module, M-ENTROPY (later in text: Entropy), Datex-Ohmeda Division, Instrumentarium Corp., Helsinki, Finland] and BIS (BIS XP, A-2000, Aspect Medical Systems, Newton, MA) data were collected from 70 patients; 30 anesthetized with propofol 2 mg kg-1, 20 with sevoflurane inhalation, and 20 with thiopental 5 mg kg-1. Loss and regaining of consciousness (LOC, ROC) was tested every 10 s, and sensitivity, specificity, and prediction probability (Pk) were calculated. Behavior of the indices was studied. RESULTS: Sensitivity, specificity, and Pk values for consciousness were high and similar for all indices. During regaining of consciousness after propofol bolus, RE, SE, and BIS values recovered by 81 +/- 22%, 75 +/- 26%, and 59 +/- 18% (mean +/- SD), respectively, from the minimum relative to their baseline. After thiopental bolus, RE, SE, and BIS values recovered by 86+/-21%, 88 +/- 13%, and 63 +/- 14%, respectively. The relative rise was higher in RE and SE compared with BIS (P < 0.01). During deep levels of hypnosis, RE and SE decreased monotonously as a function of burst suppression ratio, while BIS showed biphasic behavior. On average, RE indicated emergence from anesthesia 11 s earlier than SE, and 12.4 s earlier than BIS. CONCLUSIONS: All indices, RE, SE, and BIS, distinguished excellently between conscious and unconscious states during propofol, sevoflurane, and thiopental anesthesia. During burst suppression, Entropy parameters RE and SE, but not BIS, behave monotonously. During regaining of consciousness after a thiopental or propofol bolus, RE and SE values recovered significantly closer to their baseline values than did BIS. Response entropy indicates emergence from anesthesia earlier than SE or BIS.

Adolescent↗

PubMed2005

The influence of a muscle relaxant bolus on bispectral and datex-ohmeda entropy values during propofol-remifentanil induced loss of consciousness.

Studies investigating the influence of muscle relaxants on the bispectral index have yielded contradictory results. In our prospective, randomized, double-blind experiments, patients received a fixed target concentration of remifentanil along with a target-controlled infusion of propofol, titrated until loss of consciousness. Two minutes after loss of consciousness, the study group received a bolus injection of atracurium, whereas the control group received a placebo. The following variables were recorded: bispectral index, spectral edge frequency, electromyographic activity, state entropy, and response entropy provided by the Datex-Ohmeda Entropy monitor. Similar values were obtained in both groups at loss of consciousness. Placebo administration induced a decrease in bispectral index (P < 0.002), spectral edge frequency (P < 0.05), electromyographic activity (P < 0.02), state entropy (P < 0.05), and response entropy (P < 0.01) compared with the values measured at loss of consciousness. Atracurium administration induced a decrease in bispectral index (P < 0.0001), spectral edge frequency (P < 0.01), electromyographic activity (P < 0.0001), state entropy (P < 0.0001), and response entropy (P < 0.0001) values. Decreases in bispectral index (P < 0.05), electromyographic activity (P < 0.0001), and response entropy (P < 0.01) were larger after atracurium than placebo injection. In lightly anesthetized patients, myorelaxant administration decreases bispectral index and response entropy, but not state entropy values.

Adult↗

PubMed2006

Pharmacokinetic-pharmacodynamic modeling the hypnotic effect of sevoflurane using the spectral entropy of the electroencephalogram.

Spectral entropy is a new electroencephalogram (EEG)-derived parameter that may be used to model the pharmacokinetic-pharmacodynamic (PKPD) effects of general anesthetics. In the present study we sought to derive a PKPD model of the relationship between sevoflurane concentration and spectral entropy of the EEG. We collected spectral entropy data during increasing and decreasing sevoflurane anesthesia from 20 patients. The first cycle consisted of induction and lightening phases with no supplemental medications. An effect-site compartment and inhibitory E(max) model described the relation between sevoflurane concentration and spectral entropy. PKPD parameters were derived from the full cycle and separately from the increasing and decreasing stages. The second anesthetic cycle consisted of a redeepening phase only and included airway manipulation and routinely administered adjunctives. PKPD data obtained from the first cycle were used to predict second cycle entropy changes. There was a consistent relationship between effect-site sevoflurane concentration and spectral entropy (median absolute weighted residual = 11.6%). For complete first-cycle response entropy (mean +/- sd): T1/2 K(eo) = 2.4 +/- 1.5 min, gamma = 5.9 +/- 2.3, EC50 = 1.7 +/- 0.3. We found significant differences between gamma values when the sevoflurane concentration was increasing (61.1 +/- 55.2) compared with the decreasing part of the cycle (5.7 +/- 2.8). Above an effect-site concentration of 3%, spectral entropy of the EEG is unresponsive to further increases in sevoflurane concentration. The effect-compartment inhibitory E(max) model accurately describes the relation between sevoflurane concentration and spectral entropy of the EEG. Spectral entropy decreases with increasing sevoflurane concentrations up to 3%. The steepness of the dose-response curve varies between phases of increasing and decreasing anesthetic concentrations.

Adolescent↗

PubMed1992

Entropies of coding and noncoding sequences of DNA and proteins.

The entropies of protein coding genes from Escherichia coli were calculated according to Boltzmann's formula. Entropies of the coding regions were compared to the entropies of noncoding or miscoding ones. With nucleotides as code units, the entropies of the coding regions, when compared to the entropies of complete sequences (leader and coding region as well as trailer), were seen to be lower but with a marginal statistical significance. With triplets of nucleotides as code units, the entropies of correct reading frames were significantly lower than the entropies of frameshifts +1 and -1. With amino acids as code units, the results were opposite: Biologically functional proteins had significantly higher entropies than proteins translated from the frameshifted sequences. We attempt to explain this paradox with the hypothesis that the genetic code may have the ability of lowering information content (increasing entropy) of proteins while translating them from DNA. This ability might be beneficial to bacteria because it would make the functional proteins more probable (having a higher entropy) than nonfunctional proteins translated from frameshifted sequences.

Amino Acids↗

PubMed1998

RNA bulge entropies in the unbound state correlate with peptide binding strengths for HIV-1 and BIV TAR RNA because of improved conformational access.

For the binding of peptides to wild-type HIV-1 and BIV TAR RNA and to mutants with bulges of various sizes, changes in the DeltaDelta G values of binding were determined from experimental K d values. The corresponding entropies of these bulges are estimated by enumerating all possible RNA bulge conformations on a lattice and then applying the Boltzmann relationship. Independent calculations of entropies from fluctuations are also carried out using the Gaussian network model (GNM) recently introduced for analyzing folded structures. Strong correlations are seen between the changes in free energy determined for binding and the two different unbound entropy calculations. The fact that the calculated entropy increase with larger bulge size is correlated with the enhanced experimental binding free energy is unusual. This system exhibits a dependence on the entropy of the unbound form that is opposite to usual binding models. Instead of a large initial entropy being unfavorable since it would be reduced upon binding, here the larger entropies actually favor binding. Several interpretations are possible: (i) the higher conformational freedom implies a higher competence for binding with a minimal strain, by suitable selection amongst the set of already accessible conformations; (ii) larger bulge entropies enhance the probability of the specific favorable conformation of the bound state; (iii) the increased freedom of the larger bulges contri-butes more to the bound state than to the unbound state; (iv) indirectly the large entropy of the bound state might have an unfavorable effect on the solvent structure. Nonetheless, this unusual effect is interesting.

Animals↗

PubMed1990

Effects of exercise and chills on entropy production in human body.

Entropy flows and changes of entropy content for naked subjects in the respiration calorimeter in exercise and chills are calculated from the energetic data given by Hardy et al. (1938, J. Nutr. 16, 477) and Du Bois (1939, Bull. N.Y. Acad. Med. 15, 143). By use of these values, entropy productions in the human body in exercise and chills are estimated. The entropy production in mild exercise is 1.5-2.4 times as great as that in basal conditions. The entropy production in violent exercise is six to eight times as great as that before exercise. The entropy production in chills in cold environments is about twice as large as that in basal conditions. The entropy production in a malarial chill is about four times of that in normal subjects. These increases in entropy production will be due to the increase in heat production within the body. It seems that there is a parallel between energy and entropy viewpoints for human physiology.

Cold Temperature↗

PubMed1991

Entropy principle for human development, growth and aging.

Entropy productions within nude subjects in respiration calorimeters are calculated from the corresponding energetic data obtained by Du Bois et al. (1952, J. Nutr. 48, 257-293.). The entropy production for men is constant at environmental temperatures from 24-34 degrees C. The metabolic entropy production comprises 98.6% of the total entropy production. The entropy production for women shows a minimum at 30 degrees C (the middle of the neutral zone), a small rise in the cold zone and a trend toward a rise in the warm zone; the average entropy production for women is 8.7% smaller than that for men. The entropy production rises from 0-2 years of age, and decreases rapidly from 2-25 years of age and then gradually to 85 years of age. The entropy production does not seem to achieve a minimum or a level in the lives of men and women. Based on these results, a three-stage hypothesis of entropy production in human life is proposed.

Aged↗