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PubMed2005

Respiratory mechanics and ventilator waveforms in the patient with acute lung injury.

Acute lung injury/acute respiratory distress syndrome is a syndrome of low respiratory compliance. However, longstanding knowledge of applied respiratory mechanics and refined imaging techniques have shown that this is clearly an oversimplified view. Though the average compliance of the respiratory system is reproducibly low, regional mechanics may vastly differ; lung, airway, and chest wall mechanics may be variably affected; finally, these abnormalities may be very dynamic in nature, being influenced by time, posture, and the way positive-pressure ventilation is applied. Modern mechanical ventilators are equipped to display pressure, flow, and volume waveforms that can be used to measure respiratory compliance, airway resistance, and intrinsic positive end-expiratory pressure. These basic measurements, once the domain of applied physiologists only, are now available to aid clinicians to choose the appropriate ventilator settings to promote lung recruitment and avoid injury during lung-protective ventilatory strategies. High-resolution lung imaging and bedside recording of physiologic variables are important tools for clinicians who want to deliver specialized care to improve the outcome of critically ill patients in acute respiratory failure.

Airway Resistance↗

PubMed1984

Comparison between oscillometric and invasive blood pressure monitoring during cardiac surgery.

We compared values of invasive blood pressure measured intra-arterially with those measured noninvasively with an automated oscillometric monitor. Twenty-eight patients undergoing cardiac surgical procedures under general anesthesia were studied and 552 determinations were made. The two methods of measuring blood pressure correlated within the expected bounds of experimental accuracy and physiological variation. However, the correlation between invasive and noninvasive methods varied, apparently arbitrarily, with time. These disparities could not be explained by a linear combination of physiological variables recorded. Systolic determinations correlated the best and diastolic the least between the invasive and noninvasive methods. In general, the correlation was better for adults than for children, except with diastolic blood pressure.

Aged↗

PubMed1995

Predicting who dies depends on how severity is measured: implications for evaluating patient outcomes.

OBJECTIVE: To determine whether assessments of illness severity, defined as risk for in-hospital death, varied across four severity measures. DESIGN: Retrospective cohort study. SETTING: 100 hospitals using the MedisGroups severity measure. PATIENTS: 11 880 adults managed medically for acute myocardial infarction; 1574 in-hospital deaths (13.2%). MEASUREMENTS: For each patient, probability of death was predicted four times, each time by using patient age and sex and one of four common severity measures: 1) admission MedisGroups scores for probability of death scores; 2) scores based on values for 17 physiologic variables at time of admission; 3) Disease Staging's probability-of-mortality model; and 4) All Patient Refined Diagnosis Related Groups (APR-DRGs). Patients were ranked according to probability of death as predicted by each severity measure, and rankings were compared across measures. The presence or absence of each of six clinical findings considered to indicate poor prognosis in patients with myocardial infarction (congestive heart failure, pulmonary edema, coma, low systolic blood pressure, low left ventricular ejection fraction, and high blood urea nitrogen level) was determined for patients ranked differently by different severity measures. RESULTS: MedisGroups and the physiology score gave 94.7% of patients similar rankings. Disease Staging, MedisGroups, and the physiology score gave only 78% of patients similar rankings. MedisGroups and APR-DRGs gave 80% of patients similar rankings. Patients whose illnesses were more severe according to MedisGroups and the physiology score were more likely to have the six clinical findings than were patients whose illnesses were more severe according to Disease Staging and APR-DRGs. CONCLUSIONS: Some pairs of severity measures assigned very different severity levels to more than 20% of patients. Evaluations of patient outcomes need to be sensitive to the severity measures used for risk adjustment.

Adult↗

PubMed2006

Thermal comfort and the heat stress indices.

Thermal stress is an important factor in many industrial situations, athletic events and military scenarios. It can seriously affect the productivity and the health of the individual and diminish tolerance to other environmental hazards. However, the assessment of the thermal stress and the translation of the stress in terms of physiological and psychological strain is complex. For over a century attempts have been made to construct an index, which will describe heat stress satisfactorily. The many indices that have been suggested can be categorized into one of three groups: "rational indices", "empirical indices", or "direct indices". The first 2 groups are sophisticated indices, which integrate environmental and physiological variables; they are difficult to calculate and are not feasible for daily use. The latter group comprises of simple indices, which are based on the measurement of basic environmental variables. In this group 2 indices are in use for over four decades: the "wet-bulb globe temperature" (WBGT) index and the "discomfort index" (DI). The following review summarizes the current knowledge on thermal indices and their correlates to thermal sensation and comfort. With the present knowledge it is suggested to adopt the DI as a universal heat stress index.

Adaptation, Physiological↗

PubMed1985

The increase of perceived exertion, aches and pain in the legs, heart rate and blood lactate during exercise on a bicycle ergometer.

This study was designed to show the general increase in perceived exertion, perception of aches or pain in the legs, heart rate (HR), and blood lactate, and the covariance between these variables during bicycle ergometer work, and to describe individual differences both within and between power levels by testing a large group (28 male students). Estimates of perceived exertion and feelings of aches or pain in the legs were recorded using Borg's category-ratio scale (CR-10). The subjects were tested with a stepwise increase of power levels with 40 W increments up to a voluntary maximum. Though HR increases fairly linearly with power, the other variables follow positively accelerating functions with exponents of about 1.6-2 for the perceptual variables, and an exponent of about 3 for blood lactate. The results from the 8 most fit subjects could be described in the same way as for the whole group except for blood lactate, where there was a need to include a threshold value (b), that, together with a rest value (a), shows the starting point of the function (R = a + c(W - Wo)n). The data support the idea that a combination of heart rate and blood lactate is a better predictor of perceived exertion and feelings of aches and pain in the legs, than is each of the single physiological variables taken alone.

Adult↗

PubMed1995

Visual display format affects the ability of anesthesiologists to detect acute physiologic changes. A laboratory study employing a clinical display simulator.

BACKGROUND: Anesthesiologists use data presented on visual displays to monitor patients' physiologic status. Although studies in nonmedical fields have suggested differential effects on performance among display formats, few studies have examined the effect of display format on anesthesiologist monitoring performance. METHODS: A computer-based clinical display simulator was developed to evaluate the efficacy of three currently used display formats (numeric, histogram, or polygon displays) in a partial-task laboratory simulation. The subjects' task consisted solely of detecting any changes in the values of the physiologic variables depicted on a simulated clinical display. Response latency and accuracy were used as measures of performance. RESULTS: Thirteen anesthesia residents and five nonmedical volunteers, were enrolled as subjects. Use of either the histogram or polygon displays significantly improved response latencies and allowed greater accuracy compared with the numeric display in the anesthesia residents. Neither response latency nor accuracy improved with additional exposure to these displays. In contrast, display format did not significantly affect response latency or accuracy in the nonmedical volunteers. CONCLUSIONS: The results of this study suggest that graphic displays may enhance the detection of acute changes in patient physiologic status during anesthesia administration. This research also demonstrates the importance of assessing performance on clinical devices by studying actual users rather than random subjects. Further research is required to elucidate the display elements and characteristics that best support different aspects of the anesthesiologist's monitoring tasks.

Adult↗

PubMed1997

Metabolic and biomechanical variables of two incline conditions during distance running.

The purpose of this experiment was to examine the effects of an incline during distance running on selected metabolic and biomechanical variables. Six (4 males, 2 females) trained distance runners (age 27.2 +/- 7.8 yr; VO2max 63.7 +/- 7.5 mL x kg-1 x min-1) performed three 35-min runs at speeds corresponding to each individual's anaerobic threshold. The first run (Control) was performed at 0% grade. The remaining two runs were randomly assigned and included a 5% incline during min 5-15 (Run A) or 20-30 (Run B). Heart rate via telemetry (HR), and oxygen consumption (VO2), minute ventilation (VE), RER, and tidal volume (TV) were measured by indirect calorimetry. High speed videography was used to measure time in support phase, time in swing phase, step length, trunk lean, vertical oscillation of the hip, knee flexion in support, shank angle during toe-off, and ankle flexion at heel strike during the runs. Significant increases (P < or = 0.05) were found during the incline conditions of Run A for VO2 (+18%) HR (+11%), VE (+24%), and RER (+8%) and Run B for VO2 (+19%) HR (+10%), and VE (+25%) compared with the Control. No significant differences (P > 0.05) were noted between Run A and Run B during incline running in the physiological variables. No significant differences (P > 0.05) were observed in any of the biomechanical variables among the runs. These data indicate that the energy expenditure required during incline running is the same regardless of incline location during a 35-min run, and running mechanics are not significantly altered during a 5% incline lasting 10 min. In addition, following a 5% incline for 10 min, runners experience no significant physiological or biomechanical changes during subsequent level running at anaerobic threshold pace.

Adult↗

PubMed1988

Monitoring spinal cord blood flow using hydrogen polarography.

Spinal cord blood flow (SCBF) is an important physiological variable that may undergo changes following cord injury. We measured SCBF in healthy dogs whose cord had been cooled, a technique that is useful for treating spinal cord injured patients. A microcomputerized system developed for efficient recording of SCBF on-line is described in this paper.

Animals↗

PubMed2003

[Impact or physiological factors on some dimensions of health-related quality of life of elder men].

The article presents a fragment of the study exploring relations between various factors and health-related quality of life (HRQOL) of elder men. The aim of this article is to describe predictive influence of physiological variables (arterial blood pressure, body mass index (BMI), forced expiratory volume in 1 second (FEV(1))) on several dimensions of HRQOL assessed by "Rand-36 Health Survey" questionnaire. MATERIAL AND METHODS. The study enroled 575 male outpatients aged 59-78 from seven small towns of Lithuania. The study population was based on the original sample, formerly explored by the staff of the Department of Propedeutics to Internal Medicine, Kaunas University of Medicine. Measures of BMI, FEV(1) and blood pressure came from the baseline investigation carried out in 1983. HRQOL was assessed by means of standardized generic questionnaire. The predictive influence of physiological factors on current scores of HRQOL dimensions was determined by logistic regression analysis, controlling for the influence of sociodemographic, lifestyle and other factors. RESULTS. Physiological factors predicted scores of physical functioning, general health perceptions and emotional wellbeing. Systolic blood pressure >129 mmHg was associated with increased odds of relatively poor emotional status (OR=1.79, p=0.047). Diastolic blood pressure >80 mmHg was associated with a twofold increase in odds of poor physical functioning (OR=2.34, p=0.0013). Body mass index >34.9 kg/m(2) predicted poor physical functioning and worse general health perceptions in older age (OR=1.97, p=0.027 and OR=2.38, p=0.009, respectively). Measures of FEV(1) were associated with scores of physical functioning. 10% increase in FEV(1) was associated with reduction in odds of poor physical functioning by 52% (OR=0.48, p=0.045). CONCLUSIONS. BMI>34.9 kg/m(2) among men in adult age was related to poor physical functioning and worse perceptions of health in older age. Systolic blood pressure >129 mmHg and diastolic blood pressure >80 mmHg were predictive of worse emotional wellbeing and physical functioning, respectively. Higher measures of FEV(1) were associated with better physical functioning in later years.

Age Factors↗

PubMed1999

A comparison of ICU mortality prediction using the APACHE II scoring system and artificial neural networks.

The aim of this study was to compare the ability of artificial neural networks and the Acute Physiology and Chronic Health Evaluation II score to predict mortality in adult intensive care units. The same physiological variables were used in both predictive models to predict hospital mortality from a data set of 8796 patients collected from 26 adult intensive care units in the United Kingdom and Ireland as part of the Intensive Care Society study. The results from the two models were compared with the actual outcome. The overall prediction accuracy and the overall goodness-of-fit of all the models were assessed. Both predictive models showed similar goodness-of-fit and prediction discrimination. The overall predictive and classification performance of the artificial neural network developed matched and in some aspects was better than that of Acute Physiology and Chronic Health Evaluation II.

APACHE↗

PubMed1995

Biochemical and physiological effects in fish exposed to bleached kraft mill effluents.

The studies were performed on perch (Perca fluviatilis) caught outside Husum and Iggesund kraft pulp mills in 1985 and 1987, respectively, and the results were compared to previous observations from 1984 to 1985 in the receiving waters of the Norrsundet kraft pulp mill. The studies revealed that the biochemical and physiological variables, i.e., EROD activity, gonad size, number of lymphocytes, carbohydrate metabolites, and plasma ion composition, can be used as sensitive and reliable indicators of toxic effects on natural populations of fish exposed to conventional chlorine-bleached kraft mill effluents. However; the effects were generally less pronounced and indicated less geographic extension than those seen in perch previously investigated in the receiving waters of the Norrsundet kraft pulp mill. Based on these studies on perch at Husum and Iggesund and the previous studies at Norrsundet it can be concluded that the chlorine-bleached kraft mill effluents cause serious disturbances to vital biochemical and physiological functions, which can affect the health status and presumably also the survival of the fish. Finally, the responses do not reflect the present situation in the receiving waters since all three mills have taken extensive measures for process alterations and discharge reductions after the time of the investigations.

Animals↗

PubMed1983

Social instability and coronary artery atherosclerosis in cynomolgus monkeys.

Epidemiologic research has increasingly implicated psychological factors in the emergence of atherosclerotic coronary heart disease in human beings. The study of behavioral influences on atherogenesis in man, however, is impeded by the difficulty of assessing coronary artery atherosclerosis in asymptomatic individuals and by the fact that significant arterial lesions typically develop only over relatively protracted intervals. Consequently, we have recently attempted development of an appropriate animal model for examining the atherogenic effects of psychosocial variables. In the first of two investigations, an experimental stressor--involving repeated reorganization of socially housed groups of adult, male cynomolgus monkeys (Macaca fascicularis) fed a moderately atherogenic diet--resulted in increased coronary artery atherosclerosis relative to control animals, though only among monkeys which retained dominant social status over the 22 months of the study. In the second investigation, which employed the same experimental procedures among monkeys fed a low cholesterol/low saturated fat diet, periodic social group reorganization similarly led to development of greater atherosclerosis in the coronary arteries. In neither experiment were psychosocial influences on coronary atherogenesis attributable to the concomitant effects of other physiologic variables commonly associated with atherosclerosis (e.g., serum lipids, blood pressure).

Aggression↗

PubMed2005

Monitoring respiration during sleep.

Monitoring of respiration during sleep allows the assessment of physiologic variables that are required to characterize SRBD events. The patency of the upper airway, the pattern of breathing, oxygenation, and ventilation usually can be inferred from simultaneous measurements of airflow, respiratory effort, thoracic volume, and blood gases. As new techniques of respiratory monitoring emerge, the respiratory therapist and sleep technologist must be familiar with the advantages and shortcomings of each modality.

Humans↗

PubMed2001

Vigilance on the civil flight deck: incidence of sleepiness and sleep during long-haul flights and associated changes in physiological parameters.

The study investigated sleepiness and sleep in aircrew during long-haul flights. The objectives were to identify loss of alertness and to recommend a practical approach to the design of an alerting system to be used by aircrew to prevent involuntary sleep. The flights were between London and Miami, covering both day- and night-time sectors, each with a duration of approximately 9 h. The subjects were 12 British Airways pilots. Various physiological variables were measured that could potentially be used to indicate the presence of drowsiness and involuntary sleep: brain electrical activity (electroencephalogram, EEG), eye movements via the electro-oculogram (EOG), wrist activity, head movements and galvanic skin resistance. The EEG and EOG identified sleepiness and sleep, as well as being potential measures on which to base an alarm system. Ten pilots either slept or showed evidence of sleepiness as assessed by the EEG and EOG. Many of the episodes of sleepiness lasted < 20 s, which could mean that the subjects were unaware of their occurrence and of the potential consequences on performance and vigilance. All physiological parameters showed changes during sleep, although only the EEG and EOG were modified by sleepiness. During sleep, skin resistance was increased, and wrist activity and head movements were absent for long periods. The study indicated that the measurement of eye movements (either alone or in combination with the EEG), wrist activity or head movement may be used as the basis of an alarm system to prevent involuntary sleep. Skin resistance is considered to be unsuitable, however, being related in a more general way to fatigue rather than to sleep episodes. The optimal way to monitor the onset of sleep would be to measure eye movements; however, this is not feasible in the flight deck environment at the present time due to the intrusive nature of the recording methodology. Wrist activity is therefore recommended as the basis of an alertness alarm. Such a device would alert the pilot after approximately 4-5 min of wrist inactivity, since this duration has been shown by the present study to be associated with sleep. The possibility that sleep inertia (reduced alertness immediately after awakening from sleep) could follow periods of sleep lasting 5 min needs to be considered. The findings reported here might be applicable to other occupational environments where fatigue and sleepiness are known to occur.

Adult↗

PubMed2004

Semi-quantitative measurements of normal organs with variable metabolic activity on FDG PET imaging.

INTRODUCTION: This study evaluates the variable physiological fluoro-deoxyglucose (FDG) uptake in normal organs and their normal standardised uptake values (SUVs) among the Chinese population. MATERIALS AND METHODS: One hundred Chinese patients were enrolled into the study. There were 52 males and 48 females; their mean age was 53.5 years (range, 13 to 79 years). The SUVs of various organs were obtained from the transaxial views, but coronal and sagittal images were used whenever the exact location was in doubt. If there was further doubt, correlation with computed tomography images was made. RESULTS: The highest FDG uptakes were found in the cerebellum, tonsils, myocardium, liver, spleen, stomach and rectum. CONCLUSION: Knowing the variability of normal FDG accumulation is valuable for proper interpretation of whole-body FDG positron emission tomography (PET) studies.

Adolescent↗

PubMed2006

Physiological effects of pneumoperitoneum in laparoscopic pyloromyotomy.

A retrospective analysis comparing intraoperative physiological variables during laparoscopic and open pyloromyotomies was undertaken during an 18-month period at our institution. Fifty cases were examined (22 laparocopic and 28 open). Operative time, temperature change, end-tidal CO2, heart rate, and blood pressure were examined and compared. No significant differences were found in operative time, temperature change, heart rate, and blood pressure. As anticipated, in laparoscopic procedures there was a statistically significant increase in end-tidal CO2, although none of the end-tidal CO2 values rose above 6 kPa. It is concluded that laparoscopic pyloromyotomies undertaken in small infants with insufflation pressures of 8-10 mm Hg are without significant adverse physiological effects and are no slower to perform than open procedures.

Carbon Dioxide↗

PubMed1996

Mortality predicted by APACHE II. The effect of changes in physiological values and post-ICU hospital mortality.

The contribution of physiological values to the APACHE II score was determined by retrospective analysis of 11348 patients undergoing intensive care. Eleven physiological variables contributed a mean of 8.9 points, 54% of the total APACHE II score. The mortality ratio (observed hospital mortality/hospital mortality predicted by APACHE II) was 1.13. We altered the APACHE II scores and post-intensive care hospital mortality in order to examine the effect on the mortality ratio of these changes. Increasing scores by two or four points decreased mortality ratios to 1.00 and 0.89 respectively: decreasing scores by two or four points to a minimum of zero increased mortality ratios to 1.27 and 1.44 respectively. A 25% increase or decrease in post-intensive care hospital mortality changed mortality ratios to 1.21 and 1.05 respectively. Physiological values vary with the timing of collection and accuracy of recording. Small consistent differences in scores cause potentially important changes in the mortality ratio. Unless data collection and the effect of management before and after intensive care are standardised, using mortality ratios to compare intensive care units is likely to be inaccurate and misleading.

APACHE↗

PubMedDate not supplied

Monitoring the anesthetized patient in the operating room.

In general, monitors used by the anesthesiologist in the operating room provide three basic functions: assessment of machine and patient status to ensure safety; assessment of depth of anesthesia; and determination of physiologic variables. Improved monitoring should reduce risk and improve patient care. Some monitoring techniques are used in only a few specialized procedures, particularly in high-risk patients or for prolonged or difficult surgery. However, many less-sophisticated techniques are used in routine daily practice and require similar philosophies of monitoring. The status of the cardiovascular system is assessed primarily by monitoring the electrocardiogram and blood pressure waveforms. Although desired effects of anesthesia impact the central nervous system, this vital organ system is not routinely monitored. Likewise, widespread monitoring of the respiratory system is not routinely accomplished. Monitoring for anesthesia in the operating room has evolved to some extent in response to what can be accomplished rather than what needs to be done. While the potential for an integrated monitoring system--including all patient and delivery system variables--clearly exists, numerous difficulties preclude its becoming a reality. What is required is the development of an integrated system that can augment the anesthesiologist's sixth sense. Initial efforts toward device interface standardization, configurability, and flexibility must be encouraged to pave the way for the integrated, automated anesthesia delivery system of the future.

Anesthesia↗