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Biomedical subjects

W E Fordyce

Publications and source records attributed to W E Fordyce.

At least 19 recordsLinked to original sources
PubMed1995

Respiratory drive during status epilepticus and its treatment: comparison of diazepam and lorazepam.

In order to examine the respiratory effects of tonic-clonic seizures and their treatment with i.v. diazepam or lorazepam, we utilized a spontaneously breathing piglet seizure model. A tracheostomy, arterial catheter, and epidural electrodes were inserted and pigs were maintained under ketamine anesthesia. After baseline recordings, seizures were induced with a pentylenetetrazol (PTZ) bolus and a 20 min infusion (5-6 mg/kg/min). After 10 min of PTZ infusion, randomly assigned animals received diazepam (D; N = 7; 0.5 mg/kg), lorazepam (L; N = 7; 0.2 mg/kg), or 0.9% saline (C; N = 7; controls) by rapid peripheral vein injection. Minute ventilation (Ve), Pa(CO2), and the pressure change in response to airway occlusion at end-expiration (P0.1) were measured at standard intervals. All groups had comparable increases in respiratory drive during untreated seizures. Changes in Ve and P0.1 were reduced to at or below baseline values in groups D and L, but not C, from 2 to 45 min after treatment (P < 0.05). No significant changes were observed in Pa(CO2) after either intervention. Following anticonvulsants, the cumulative duration of seizures was significantly reduced in L and D groups, compared to C (P < 0.05). We conclude that increases in respiratory drive occur during tonic-clonic seizures induced with PTZ. Amelioration of seizure activity with lorazepam or diazepam results in a reduction in respiratory drive, but not respiratory failure, in this tracheostomized model.

Animals↗
PubMed1995

The role of the upper airway in contributing to respiratory responses during experimental seizures in piglets.

Recent data demonstrating stimulation of respiration during seizures are at odds with the frequent clinical finding of respiratory impairment in patients with generalized seizures. To determine the role of the upper airway in contributing to these clinical observations, a study was performed in 12 weanling piglets. An arterial catheter and epidural electrodes were placed in ketamine-anesthetized piglets. In intact piglets, all airflow was measured through a snug-fitting nasal mask whereas pressure was measured with a subglottic catheter. Tracheostomized piglets had airflow and pressure measured at the trachea. Seizures were induced with i.v. injections of pentylenetetrazol. Peak inspiratory flow resistance was calculated by averaging three epochs of five to seven consecutive breaths. Epochs of greater than 20 s in duration with a tidal volume of < 10 mL were termed apnea. Apnea was considered central when airway pressure was > -2 cm H2O and obstructive when < -10 cm H2O. After 20 min of untreated seizures, intact piglets had significant respiratory and metabolic acidosis, whereas tracheostomized piglets had significant increases in Ve and mild metabolic acidosis. Apnea and obstruction were observed frequently in intact piglets. Resistance was unchanged during seizures in tracheostomized piglets, whereas a nearly 4-fold increase in inspiratory resistance was observed in intact piglets. We conclude that upper airway patency and resistances are important determinants of respiratory responses during generalized seizures in piglets.

Analysis of Variance↗
PubMed1994

The importance of placebo effects in pain treatment and research.

OBJECTIVE: To estimate the importance and implications of placebo effects in pain treatment and research from the existing literature, with emphasis on their magnitude and duration, the conditions influencing them, and proposed explanations. DATA SOURCES: English-language articles and books identified through MEDLINE (1980 through 1993) and PsycLIT (1967 through 1993) database searching, bibliography review, and expert consultation. STUDY SELECTION: Articles were included if they pertained to the review objectives. RESULTS: Placebo response rates vary greatly and are frequently much higher than the often-cited one third. Placebos have time-effect curves, and peak, cumulative, and carryover effects similar to those of active medications. As with medication, surgery can produce substantial placebo effects, and this possibility is commonly overlooked in case series reports on back surgery. Individuals are not consistent in their placebo responses, and a placebo-responder personality has not been identified. Models advanced to explain placebo effects emphasize the role of anxiety, expectations, and learning. CONCLUSIONS: Placebo effects influence patient outcomes after any treatment, including surgery, that the clinician and patient believe is effective. Placebo effects plus disease natural history and regression to the mean can result in high rates of good outcomes, which may be misattributed to specific treatment effects. The true causes of improvements in pain after treatment remain unknown in the absence of independently evaluated randomized controlled trials.

Dose-Response Relationship, Drug↗
PubMed1994

Pain and suffering: what is the unit?

Nonspecific low back pain presents several problems to health care providers. Although the number of patients who are registered as disabled due to low back pain has dramatically increased in recent years, its incidence and severity remain fairly constant. The relationship between perceived backache and subsequent disability is not linear, and other factors may influence a patient's decision to seek help. These factors include the patient's psychological and emotional state, especially his or her past experiences, extant mood and anxiety about anticipated consequences. Physicians should not rely on a simple 'disease model' when treating low back pain but should try to identify the biopsychosocial factors involved and should understand that pain and suffering are not always synonymous.

Disability Evaluation↗
PubMed1992

The effect of graded activity on patients with subacute low back pain: a randomized prospective clinical study with an operant-conditioning behavioral approach.

The aim of this study was to determine whether graded activity restored occupational function in industrial blue-collar workers who were sick-listed for 8 weeks because of subacute, nonspecific, mechanical low back pain (LBP). Patients with LBP, who had been examined by an orthopedic surgeon and a social worker, were randomly assigned to either an activity group (n = 51) or a control group (n = 52). Patients with defined orthopedic, medical, or psychiatric diagnoses were excluded before randomization. The graded activity program consisted of four parts: (1) measurements of functional capacity; (2) a work-place visit; (3) back school education; and (4) an individual, submaximal, gradually increased exercise program, with an operant-conditioning behavioral approach, based on the results of the tests and the demands of the patient's work. Records of the amount of sick leave taken over a 3-year period (ie, the 1-year periods before, during, and after intervention) were obtained from each patient's Social Insurance Office. The patients in the activity group returned to work significantly earlier than did the patients in the control group. The median number of physical therapist appointments before return to work was 5, and the average number of appointments was 10.7 (SD = 12.3). The average duration of sick leave attributable to LBP during the second follow-up year was 12.1 weeks (SD = 18.4) in the activity group and 19.6 weeks (SD = 20.7) in the control group. Four patients in the control group and 1 patient in the activity group received permanent disability pensions. The graded activity program made the patients occupationally functional again, as measured by return to work and significantly reduced long-term sick leave.

Absenteeism↗
PubMed1992

MMPI scale 3 as a predictor of back injury report: what does it tell us?

Items and selected subscales of Scale 3 (Hysteria) of the MMPI were examined to pinpoint personality or emotional factors predictive of back injury reports in an industrial setting. Data were derived from a previous prospective-design study of back pain in volunteer hourly wage employees of an aircraft manufacturing company. After physical examination and completion of questionnaires pertaining to demographic, psychosocial (including the MMPI), and workplace factors, workers were followed for an average of 3 years. Those who subsequently reported back injury were compared with those who did not. In that study three variables predicted report of back injury, one of which was Scale 3 of the MMPI. Individual items, Ornduff et al. subscales of Psychological Denial and Body Concern, and the five Harris-Lingoes (1955) subscales of Scale 3 were analyzed. Three Harris-Lingoes subscales showed significant relationships to the criterion. Hy-3: Lassitude/Malaise; Hy-1: Denial of Social Anxiety; and, marginally, Hy-2: Need for Affection, significantly contributed to prediction effectiveness. Results and implications for the understanding of factors predicting back injury reports and for the medical evaluation of pain and the concept of pain are discussed.

Back Injuries↗
PubMed1992

A longitudinal, prospective study of industrial back injury reporting.

The authors prospectively evaluated 3020 volunteers of the Boeing-Everett plant to assess risk factors that predispose workers to file industrial back injury claims. During four years of follow-up observation, more than 279 subjects reported acute back problems. The effect of the only predictive physical variable was explainable by a history of medical treatment. The most predictive individual factors were (1) job task dissatisfaction and (2) distress as reported on Scale 3 of the Minnesota Multiphasic Personality Inventory (MMPI). This data perhaps explains why the focus on purely physical and injury-related factors has met with little success in dealing with what has become the most expensive orthopedic problem. Clinically, nonphysical factors that significantly impact the reporting of back injuries may also affect patients' responses to medical treatment.

Accidents, Occupational↗
PubMed1991

A prospective study of work perceptions and psychosocial factors affecting the report of back injury.

A longitudinal, prospective study was conducted on 3,020 aircraft employees to identify risk factors for reporting acute back pain at work. The premorbid data included individual physical, psychosocial, and workplace factors. During slightly more than 4 years of follow-up, 279 subjects reported back problems. Other than a history of current or recent back problems, the factors found to be most predictive of subsequent reports in a multivariate model were work perceptions and certain psychosocial responses identified on the Minnesota Multiphasic Personality Inventory (MMPI). Subjects who stated that they "hardly ever" enjoyed their job tasks were 2.5 times more likely to report a back injury (P = 0.0001) than subjects who "almost always" enjoyed their job tasks. The quintile of subjects scoring highest on Scale-3 (Hy) of the MMPI were 2.0 times more likely to report a back injury (P = 0.0001) than subjects with the lowest scores. The multivariate model, including job task enjoyment, MMPI Scale-3, and history of back treatment, revealed that subjects in the highest risk group had 3.3 times the number of reports in the lowest risk group. These findings emphasize the importance of adopting a broader approach to the multifaceted problem of back complaints in industry and help explain why past prevention efforts focusing on purely physical factors have been unsuccessful.

Adult↗
PubMed1991

Behavioral factors in pain.

Pain is reconceptualized in learning-based behavioral terms. Methods to assess behavioral elements of pain and to discuss nonmedical influences on pain with patients as well as behaviorally based tactics for early and long-term management and reactivation are discussed in this article.

Back Pain↗
PubMed1990

A model for evaluation of gas exchange: mouth to mouth ventilation of infants by emergency medical technicians.

We describe a model for evaluating techniques of infant ventilation during resuscitation. The utility of the model is illustrated by testing performance of emergency medical technicians in mouth to mouth ventilation of a model 4 kg infant. Ventilation was generally adequate with mean (+/- S.D.) frequency 22 +/- 9 breaths per minute and tidal volume 40 +/- 13 ml. Gas delivered to the model consisted of PICO2 7 +/- 6 mmHg and FIO2 0.20 +/- 0.007. Assuming normal metabolic rate and respiratory dead space, alveolar gas composition resulting from the simulated resuscitations would be PACO2 = 31 +/- 20 and PAO2 = 110 +/- 19 mmHg. Nine of ten rescuers would have achieved satisfactory PACO2 less than or equal to 50 and PAO2 greater than or equal to 100. However, the rescuers' exhaled oxygen concentration is not adequate to correct hypoxemia if associated with hypoventilation or a wide alveolar to arterial oxygen gradient.

Emergencies↗
PubMed1990

Evaluation of resuscitation proficiency in simulations: the impact of a simultaneous cognitive task.

In order to evaluate the impact of simulation complexity on resuscitation skill performance, 15 pediatric residents were observed in bag-valve-mask ventilation on an infant manikin. Performance was evaluated in a simple exercise in which ventilation was performed as a single isolated task. For each subject, this was compared to performance when a cognitive task involving clinical problem solving was simultaneously presented. Performance was expressed as frequency, tidal volume, and estimated hypothetical alveolar Pco2 in each resuscitation. A correlation was observed (P less than 0.05) between simple and complex resuscitation simulations for each measure of performance. The only subject with inadequate performance in the complex exercise was also identified as deficient in the simple exercise. These observations suggest that an adequate evaluation of performance of some resuscitation skills may be obtained in simple, efficient simulation exercises.

Carbon Dioxide↗
PubMed1989

Learning factors in pain.

The concept of pain is analyzed from the perspective of behavioral science. Distinctions between pain and suffering are drawn and the impact of learning or experience is discussed. Implications for management of pain, exercise and restoration of functional performance, and use of pain-related medications are described.

Behavior↗
PubMed1988

Arterial-end tidal PCO2 equilibration in the cat during acute hypercapnia.

We have studied the problem of pulmonary capillary-alveolar CO2 exchange in the cat during acute hypercapnia. Three cats, anesthetized with xylazine and pentobarbital sodium and prepared with acute tracheostomy and femoral arterial catheter, and three awake cats, prepared with a small tracheal catheter and femoral arterial catheter, were subjected to acute hypercapnia (FICO2 = 0.00, 0.06, and 0.08). During steady states, end tidal PCO2 was determined with an infrared analyzer, and arterial PCO2 was measured with a Radiometer ABL-2 analyzer in simultaneously drawn samples. In vitro studies indicated that our blood sampling techniques resulted in a 6% reduction in PCO2. Blood PCO2 readings were corrected for (1) non-ideal performance of the analyzer as determined by tonometry, (2) 6% reduction due to sampling, and (3) differences between electrode and rectal temperature. Mean arterial-end tidal PCO2 differences were not significantly different from zero in any condition in either group (except for 0.08 CO2 in the awake group when the difference was 2.0 Torr). These findings in the cat agree with the classical view that PCO2 in pulmonary capillary blood approaches PCO2 in alveolar gas. Further, our findings provide evidence that CO2 loss from blood samples is an important technical factor which can cause systematic underestimation of blood PCO2 and, hence, contribute to the observation of negative PCO2 gradients.

Acute Disease↗
PubMed1988

Gain of the ventilatory exercise stimulus: definition and meaning.

The ratio G = delta VE/delta VCO2 where delta VA is change in ventilation and delta VCO2 is change in CO2 production, is often used to quantitate the ventilatory response to exercise and is the overall system gain (G). However, the actual variable of interest often is the gain for the exercise stimulus (GEX). Exercise stimulus refers to a stimulus or group of stimuli other than the mean levels of arterial PO2 (PaCO2), PCO2 (PaCO2), and pH (pHa) that act to increase ventilation during exercise. GEX will be equal to G only if the response to exercise is precisely isocapnic, normoxic, and without metabolic acidosis. A mathematical model was used to examine the relationship between G and GEX when 1) the response to exercise is not strictly isocapnic and 2) when the resting PaCO2 is shifted away from its normal value. It was found that 1) when the exercise response was not strictly isocapnic, G was a poor estimate of GEX and 2) when resting PaCO2 was changed while GEX wa assumed to remain constant, G was a function of the resting PaCO2. However, this dependence of G on resting PaCO2 is a system property that was caused by the nonlinear properties of the gas exchange processes and was not a fundamental property of the controller. It is concluded that G may not always be a good estimate of GEX and may lead to incorrect conclusions concerning the nature of the exercise stimulus.

Carbon Dioxide↗
PubMed1988

Psychological factors in the failed back.

Pain is a complex phenomenon. Lack of understanding of its nature leads to two common mistakes in the failed back, firstly to look for a discrete physical cause and secondly to ascribe pain to psychological causes. This paper explores the nature of pain in the failed back and discusses the implications for treatment.

Back Pain↗
PubMed1987

Hypoxic ventilatory control in the awake cat five years after carotid body resection.

Steady state breathing patterns, alveolar gases, and arterial blood gases and pH were measured during air, acute hypoxia, and acute hyperoxia in four awake cats 5 years after combined carotid body resection (CBR) and aortic depressor nerve section. Steady state breathing patterns and alveolar gases were also measured in these animals following 3 days of hypoxia (PIO2 = 110 Torr). The results show that the awake cat without carotid bodies and aortic depressor nerves hypoventilates during normoxia in relation to intact cats. Acute hypoxia resulted in respiratory acidosis, decreased tidal volume (VT), and decreased breath duration (TTOT). Exposure to hypoxia for three days resulted in no hyperventilation (isocapnia) but increased VT and TTOT from their levels during acute hypoxia. Acute hyperoxia resulted in respiratory alkalosis and increased VT. Moderate degrees of acute inspiratory hypoxia (FIO2 less than 0.12) induced a behavioral 'arousal' in these cats; this is in direct contrast to the lack of response seen shortly after CBR. Presumably, the recrudescence of chemosensitivity via unsectioned aortic chemoreceptor afferents played a key role in the arousal responses. However, there is no evidence in the cat for recrudescent chemoreceptor input to the respiratory control system with measurable steady state effect. We conclude that the peripheral chemoreceptors are essential for normal resting ventilatory control and for acclimation to chronic hypoxia.

Adaptation, Physiological↗