Biomedical subjects

G M Davis

Publications and source records attributed to G M Davis.

At least 19 recordsLinked to original sources

PubMed1992

Clinical information systems: 25-year history and the future.

Clinical information Systems have not advanced rapidly enough to meet the growing needs for clinical data. This is due primarily to the industry's past focus on financial information processing. Pressure is increasing for clinical data to support health-care professionals in the delivery of patient care, and in the establishment and monitoring of quality of care indicators. This article summarizes the history of clinical systems, and presents key issues regarding future clinical information systems.

Clinical Medicine↗

PubMed1991

Left-side displacement of the abomasum in dairy cows at pasture.

The presentation of approximately 40 dairy cows affected with left-side displacement of the abomasum (LDA) per annum in a cattle practice in East Gippsland, Victoria provided an opportunity to conduct a survey and case-control study of the disease in a grazing environment. The study, involving 37 dairy cows at pasture, revealed significant differences from the pattern of the disease occurring in the northern hemisphere where cows in older age groups, of larger frame size, higher production and fed high grain rations are at increased risk. Affected cows were diagnosed over a 10-month period and represented approximately 0.06% of the dairy cow population. Most cases were diagnosed in the early lactation period. Evidence for a genetic predisposition was suggested by the discovery that one sire generated a disproportionately large number (9) of the cows with LDA. Although affected cows were average producers in their herds, being a member of a high-producing herd was a significant risk factor.

Abomasum↗

PubMed1990

Cardiorespiratory and perceptual responses to arm crank and wheelchair exercise using various handrims in male paraplegics.

The purpose of the present study was to determine the effects of 10-in [0.25-m] versus 16-in [0.41-m] wheelchair handrims on cardiorespiratory and psychophysiological exercise responses during wheelchair propulsion at selected velocities. Fifteen male paraplegics (27.0 +/- 5.5 yrs) performed three discontinuous exercise tests (ACE = arm crank ergometer; WERG = wheelchair roller ergometer) and two 1600-m performance-based track trials (TRACK) under simulated race conditions. There were no significant differences in HR, VO2, VE, HLa, or category-ratio ratings of perceived exertion (RPE) using different handrims during wheelchair propulsion at 4 km.h-1. In contrast, at 8 km.h-1 subjects demonstrated a 13% lower steady state VO2 (p less than .05) using the 10-in handrims, coincident with a 23% lower VE. Steady state HR during WERG at 8 km.h-1 using the 10-in (124.4 +/- 3.9 b.min-1) or 16-in (130.6 +/- 4.6 b.min-1) handrims were not significantly different. There were also no significant differences between ACE or WERG conditions during maximal effort for VO2 or VE. However, HRpeak during ACE was 7% higher than HRpeak during WERG16 (183 +/- 15 b.min-1 vs. 171 +/- 12 b.min-1, p less than .05), and whole blood HLa during ACE was also significantly higher (by 2.3-2.5 mmol; p less than .05) compared to WERG. There were no significant differences for HR, performance time, or RPE between trials using different handrim diameters during the 1600-m event.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Survival and fertility after uterine prolapse in dairy cows.

Sixty-eight cases of uterine prolapase in pastured dairy cows were treated in 2 consecutive spring calving seasons in East Gippsland, Victoria. Fifty cows survived (73.5%). Of 43 cows available for followup, 36 (84%) conceived in the mating period following the prolapse, taking 10 d longer to conceive than herd mates that calved on the same day. Three of the 36 cows (8%) that conceived, aborted, this occurring in the middle trimester of pregnancy. No prolapses occurred at the following calving but one case had suffered uterine prolapse 2 years previously. The conclusions drawn from these observations are that cows with uterine prolapse have a good chance of surviving if treated, that treatment is cost-effective, that uterine prolapse is unlikely to reoccur and treated cows have a good chance of conceiving. The veterinarians involved in this investigation were reasonably accurate in their ability to predict long term survival but not as good in predicting ability to conceive again.

Age Factors↗

PubMed1990

Strength training for wheelchair users.

Sedentary adult males with spinal lesions, all habitual wheelchair users, were allocated to exercise (n = 11) and control (n = 4) groups. A Cybex II dynamometer was used to assess peak power, average power, total work and muscular endurance for elbow flexion/extension, shoulder flexion/extension and shoulder abduction/adduction at five angular velocities, on recruitment and after eight and 16 weeks of forearm ergometer training (three days/week). Small sub-groups of the exercised subjects were assigned to high or low intensity endurance effort (70 or 40 per cent of maximal oxygen intake) and long or short training sessions (40 or 20 minutes per session). Despite the aerobic nature of the activity, gains of average power were registered by the two muscle groups most involved in the ergometer task (shoulder extension and elbow flexion). In keeping with current theories of training, gains were largest with prolonged, high intensity activity at angular velocities approximating those adopted during training.

Adolescent↗

PubMed1990

Cardiovascular responses to arm cranking and FNS-induced leg exercise in paraplegics.

Twelve spinal cord-injured males performed arm-crank exercise (ACE) with and without concurrent functional neuromuscular stimulation (FNS) of paralyzed leg muscles to investigate the hypothesis that FNS would augment cardiovascular performance during submaximal ACE. Six men who exhibited vigorous isometric contractions of thigh and calf muscles were classed as "responders" to FNS (R), and the remaining subjects with poor or nonexistent contractions served as "nonresponder controls" (C). Steady-state heart rate and oxygen uptake during ACE at 30, 60, and 90 W were not appreciably different from the ACE + FNS condition. However, cardiac outputs in R were augmented by 30% during FNS at rest (from 4.9 to 6.4 l/min), by 18% during 30-W ACE + FNS (from 8.6 to 10.1 l/min), and by 28% during 90-W ACE + FNS (from 12.1 to 15.6 l/min). Similarly, resting stroke volumes were increased by 18% (9 ml) and by 23% (19 ml) at 60 W during FNS in the R group. Calculated total peripheral resistance was reduced at rest and during 90-W ACE + FNS by approximately 24%. In contrast, no alterations of circulatory hemodynamics were observed for C subjects. These data indicate that FNS-induced contractions of paralyzed leg muscles augment venous return to aid central cardiovascular control during upper-body submaximal exercise in paraplegics.

Adult↗

PubMed1990

A very low dead space pneumotachograph for ventilatory measurements in newborns.

In premature and full-term neonates, technical limitations hamper the measurements of pulmonary mechanics. Current commercially available pneumotachographs (PNT) either increase the dead space, causing hyperventilation, or increase resistance, thus altering the mechanics of breathing. We modified a previously described low dead space PNT for infants to increase the linear range and frequency response. The mean resistance of the new PNT was 2.44 cmH2O.1-1.s compared with 2.65 cmH2O.1-1.s for the Fleisch no. 0 PNT. The added dead space over the standard endotracheal connector was 0.6 ml compared with 4.7 ml for the Fleisch PNT. Like the Fleisch PNT, the flow resistance was linear from 0 to 15 l/min. In response to a sinusoidal waveform, the new PNT had a phase angle of 21 degrees at 5 Hz and 50 degrees at 16 Hz compared with 19 degrees and 43 degrees, respectively, for the Fleisch PNT. The change in attenuation for both systems was zero until 20 Hz. In summary, the new PNT is lightweight and provides accuracy and low resistance with a very small dead space.

Airway Resistance↗

PubMed1990

Digital clubbing due to secondary hyperparathyroidism.

Five patients in our dialysis population had digital changes suggestive of clubbing in association with severe secondary hyperparathyroidism. All had parathyroidectomies between June 1986 and December 1987. They represented 0.6% of the patients in our dialysis population and 17.8% of our patients who required operative management of secondary hyperparathyroidism. The clubbing was occasionally painful, and the digits were tender in response to palpation. Parathyroidectomy yielded excessive amounts of hyperplastic parathyroid tissue in each case. Postoperatively, the symptoms were relieved, when present, and the digital changes were stabilized. We believe that these findings are associated with severe secondary hyperparathyroidism and should be looked for in dialysis patients with renal osteodystrophy.

Adult↗

PubMed1989

Prognostic factors for recovery from coxo-femoral dislocation in cattle.

Details were recorded of 47 cases of coxo-femoral dislocation observed in cattle over 1 year. Treatment was successful in 20/47 (42.6%) cases using a method of closed reduction. Factors that most strongly influenced the prognosis were identified. The most useful single prognostic factor was whether the cow was able to stand before reduction. Other factors that also had a strong positive influence on the prognosis were: age less than 3y, bodyweight less than 400kg and duration of dislocation less than 12h. Nineteen unsuccessful cases were examined at the knackery. Four were found to have a fracture of the proximal femur. The coxo-femoral joint was carefully dissected in the other 15 cases and there was no evidence of hip dysplasia. A seasonal incidence of dislocations, which coincides with the calving and mating periods, was demonstrated during the survey and from practice records for the previous 3 years.

Age Factors↗

PubMed1989

Liquid-filled esophageal catheter for measuring pleural pressure in preterm neonates.

The precise measurement of esophageal pressure (Pes) as a reflection of pleural pressure (Ppl) is crucial to the measurement of lung mechanics in the newborn. The fidelity of Pes as a measurement of Ppl is determined by the occlusion test in which, during respiratory efforts against an occlusion at the airway opening, changes in pressure (delta Pao) (Pao is assumed to be equal to alveolar pressure) are shown to be equal to changes in Pes (delta Pes). Eight intubated premature infants (640-3,700 g) with chest wall distortion were studied using a water-filled catheter system to measure Pes. During the occlusion test, all patients had a finite region of the esophagus where delta Pes equaled delta Pao, which corresponded to points in the esophagus above the cardia but below the carina. In conclusion, even in the presence of chest wall distortion, a liquid-filled catheter with the tip between the cardia and carina can provide an accurate measurement of Ppl, even in the very small premature infant with chest wall distortion.

Catheterization, Peripheral↗

PubMed1988

The sustained ventilatory response to hypoxic challenge in the awake newborn piglet with an intact upper airway.

The diphasic ventilatory response to steady-state hypoxia has been reported in anesthetised, intubated newborn piglets. We questioned whether this diphasic response persisted in the awake, spontaneously breathing piglet. Nine piglets, at one day of age, breathing spontaneously through a fitted mask and pneumotachograph were examined, monitoring the minute ventilation. (VE) tidal volume (VT), respiratory frequency (f), mean inspiratory flow (VT/TI), inspiratory time (TI). The piglets were studied in room air, followed by a step change to an FIO2 of 0.12, and a subsequent step-change to an FIO2 of 0.08. For each step-change in the FIO2 there was a decline in VT during hypoxia, but the VE increased significantly throughout the hypoxia through a progressive increase in both f and VT/VI. Thus, the awake newborn piglets were able to sustain the increase in VE during hypoxia. These results differ from previous observations of the diphasic VE response to hypoxia in lightly anesthetised piglets suggesting that the ventilatory response to steady state hypoxia is dependent upon experimental conditions. Further, the finding of a sustained ventilatory response in awake piglets breathing through an intact upper airway differs from previous studies in lambs and kittens suggesting a difference in the level of maturity at birth between the species.

Animals↗

PubMed1988

Measurement of pulmonary mechanics in the newborn lamb: a comparison of three techniques.

Although recent interest in neonatal respiratory mechanics has led to the development of a plethora of techniques for measuring lung compliance and resistance, a critical appraisal of the limitations of these techniques in the newborn has not been performed to date. We evaluated three techniques of measuring respiratory mechanics in the newborn lamb, with the reference method (method 1) being the Mead-Whittenberger technique using flow, volume, and esophageal pressure (Pes) by water-filled catheter, and the other two methods entailing the measurement of mouth pressure (Pm) during airway occlusion (method 2 using end-expiratory occlusion; method 3 using end-inspiratory occlusion). Each technique was evaluated during eupnea and tachypnea in intubated and nonintubated newborn lambs. We found that the use of Pes for the measurement of resistance and compliance gave the most reliable results during both eupnea and tachypnea in both the intubated and nonintubated subjects. The airway occlusion techniques that use Pm to derive resistance and compliance (methods 2 and 3) gave more variable results under all conditions of testing. Method 2 was the least precise method of measurement with a variability of greater than 30% compared with a variation of less than 20% for method 1. For all three methods, it was found that the number of breaths needed for reproducible measurements of mechanics was four to six during eupnea and seven to nine during tachypnea.

Airway Resistance↗

PubMed1988

Direct measurement of static chest wall compliance in animal and human neonates.

The measurement of pulmonary mechanics has been developed extensively for adults, and these techniques have been applied directly to neonates and infants. However, the compliant chest wall of the infant frequently predisposes to chest wall distortion, especially when there is a low dynamic lung compliance (CL,dyn). We describe a technique of directly measuring the static chest wall compliance (Cw,st), developed initially in the newborn lamb and subsequently applied to the premature neonate with chest wall distortion. The mean CL,dyn in seven intubated newborn lambs in normoxia was 2.45 +/- 0.41 ml.cmH2O-1.kg-1, whereas Cw,st was 11.81 +/- 0.25 ml.cmH2O-1.kg-1. These values did not change significantly in seven animals breathing through a tight-fitting face mask or with hypercapnia-induced tachypnea. For the eight premature infants the mean CL,dyn was 1.35 +/- 0.36 ml.cmH2O-1.kg-1, whereas the mean Cw,st was 3.16 +/- 1.01 ml.cmH2O-1.kg-1. This study shows that, under relaxed conditions when measurements of static compliance are performed, the chest wall is more compliant than the lung. The measurement of Cw,st may thus be used to determine the contribution of the respiratory musculature in stabilizing the chest wall.

Animals↗

PubMed1988

Cardiorespiratory fitness in highly active versus inactive paraplegics.

Maximum and submaximum arm crank exercise performances were assessed in male paraplegics (PARA) with the purpose of comparing cardiovascular responses among individuals of highly active (A, N = 15) vs inactive (I, N = 15) lifestyles. The A PARAs (average VO2 peak during arm cranking 2.24 l.min-1) demonstrated a significantly higher maximal cardiorespiratory fitness compared to I subjects (average VO2 peak 1.56 l.min-1). During graded arm exertion, at exercise intensities approximating 45%, 57%, and 70% of VO2 peak, the active subjects developed cardiac outputs (assessed via CO2-rebreathing) ranging from 9.07 to 11.21 l.min-1; a 34-44% advantage relative to their inactive counterparts (6.30-8.36 l.min-1). Similarly, exercise stroke volumes for A (76-80 ml) were 38-45% higher than for I paraplegics (55-56 ml). Although both groups demonstrated a distinctive circulatory hypokinesis during arm cranking, the immediate pattern of cardiovascular response was dissimilar for the highly active versus inactive subjects. The former demonstrated a predominantly "central" adaptation to steady-state arm exercise (exhibiting normal stroke volumes and arteriovenous O2 extractions for spinal cord-injured subjects), while the latter displayed markedly reduced stroke volumes concomitant with abnormally large peripheral arteriovenous oxygen extractions for a given oxygen uptake.

Adolescent↗

PubMed1987

Sleep deprivation and cardiorespiratory function. Influence of intermittent submaximal exercise.

The effects of 64 h of sleep deprivation upon cardiorespiratory function was studied in 11 young men (VO2max = 55.5 ml kg-1 min-1, STPD). Six subjects engaged in normal sedentary activities, while the others walked on a treadmill at 28% VO2max for one hour in every three; eight weeks later, sleep deprivation was repeated with a crossover of subjects. Immediate post-deprivation measurement of VO2max showed a small but statistically significant decrease (-3.8 ml min-1 kg-1, STPD), with no difference between exercise and control trials. The final decrement in aerobic power was not due to a loss of motivation, as 88% (21 of 24) of post-deprivation tests still showed a plateau of VO2max; in addition, terminal heart rates (198 vs 195 beats min-1), respiratory exchange ratios (1.14 vs 1.15) and blood lactate levels (12.1 vs 11.8 mmol l-1) were not significantly different after sleep deprivation. The decrease in VO2max was associated with a lower VEmax (127 vs 142 l min-1, BTPS) and a substantial haemodilution (13%). Physiological responses to sub-maximal exercise showed persistence of the normal diurnal rhythm in heart rate and oxygen consumption, with no added effects due to sleep deprivation. However, ratings of perceived exertion (Borg scale) increased significantly throughout sleep deprivation. The findings are consistent with a mild respiratory acidosis, secondary to reduced cortical arousal and/or a progressive depletion of tissue glycogen stores which are not altered appreciably by moderate physical activity.

Adult↗

PubMed1987

Cardiac effects of short term arm crank training in paraplegics: echocardiographic evidence.

The cardiac responses of male paraplegics to upper-body endurance training have been studied by M-mode echocardiography and CO2-rebreathing determination of cardiac output. Data for nine exercised subjects are compared with 5 controls. After 16 weeks of arm ergometer exercise, heart rates of trained individuals were 9 bt X min-1 lower during isometric handgrip effort (30% of MVC for 3 min), with a substantial decrease of rate pressure product (20%; p less than 0.05). In contrast (possibly because of greater anticipation) the control subjects developed a larger rate-pressure product with repetition of the standard isometric effort. Despite a significant increase of VO2 peak (19% and 31% after 8 and 16 weeks, respectively; p less than 0.05), echocardiographic LV mass, dimensions and indices of LV performance were unchanged by training, either at rest or during the isometric handgrip. Stroke volumes were significantly increased by 12-16% after training, both in isometric and in rhythmic work; at the highest intensity of arm ergometry, there was also a suggestion of increased cardiac output. We conclude that a short period of arm training is insufficient to induce cardiac hypertrophy, an increase of stroke volume with a decreased rate-pressure product but no change in echocardiographic indices of LV performance implies an improved myocardial efficiency. Possible explanations are a greater strength of the trained arms, and some increase of pre-loading (due to an increase of venous tone and more effective operation of the muscle pump after training).

Adult↗

PubMed1987

Pulmonary and chest wall mechanics in the control of respiration in the newborn.

Although the respiratory system is not fully developed at birth, the human newborn infant has flexible strategies to sustain breathing and defend blood gas homeostasis in both health and disease conditions. Initially the thresholds for chemoreceptor response to PO2 and PCO2 closely mimic those of the fetus, but the threshold resets to sustain ventilation adequate for blood gas homeostasis appropriate to the extrauterine milieu. The muscles of respiration have been "trained" in utero and effectively assume the function of the respiratory pump, despite their marginal reserve against fatigue. The pliable chest wall is functionally stabilized by the tonic activity of the intercostal muscles, thereby allowing effective ventilation. Finally, expiration is prolonged by the postinspiratory activity of the diaphragm and laryngeal braking as a means of maintaining an elevated lung volume and augmenting FRC. The ventilatory response of the newborn to respiratory disease is limited. The magnitude of the VE response is smaller than that of the adult, and is characterized by an increase in the respiratory rate and a limited increase in the VT. The poor effort reserve of the muscles, especially the diaphragm, predisposes the newborn to muscle fatigue and ventilatory failure. To avoid fatigue, recruitment of accessory muscles occurs, along with laryngeal braking of expiration, thereby decreasing the work of the diaphragm, recruiting new alveoli by an auto-PEEP effect, increasing the FRC volume, and improving gas exchange by an increase in the pulmonary surface area. These mechanisms help to avoid muscle exhaustion and facilitate adequate gas exchange in the presence of lung disease. We do not know precisely the postconceptual age at which the newborn is sufficiently developed to adopt these various defensive strategies of breathing, but the presence of tachypnea and grunting in 28-week-old premature infants suggests that long before term the human infant is capable of remarkable variation in the defense of breathing.

Biomechanical Phenomena↗

PubMed1985

Muscle strength and aerobic power--a study of lower-limb disabled males.

The relationship between arm strength and aerobic power (VO2 peak) was examined in 35 lower-limb disabled males. Equations related predicted VO2 peak to simple measurements of isokinetic and/or static strength. Covariance analysis (ANCOVA) showed that after allowance for level of habitual activity and lesion level there was a highly significant relationship between VO2 peak and simple strength measurements (greater for isokinetic than for static data). The findings suggest that in the wheelchair-bound the extent to which arm strength is developed has more impact upon cardiovascular performance than does the anatomical level of the lesion.

Adolescent↗