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Biomedical subjects

J M Patrick

Publications and source records attributed to J M Patrick.

At least 19 recordsLinked to original sources
PubMed1990

A longitudinal study of respiratory changes in normal human pregnancy with cross-sectional data on subjects with pregnancy-induced hypertension.

Respiratory frequency, tidal volume, minute ventilation, oxygen consumption, carbon dioxide production, and end-tidal carbon dioxide tension were measured longitudinally during pregnancy and post partum in 20 normal subjects with a computer-assisted mass spectrometer. Resting tidal volume, minute ventilation, oxygen consumption, and carbon dioxide production increased during pregnancy. End-tidal carbon dioxide tension fell progressively during pregnancy. Respiratory exchange ratio was 0.9 at 36 to 39 weeks' gestation and 0.8 at 5-13 weeks post partum. Respiratory frequency did not change during pregnancy. The increase in minute ventilation is in excess of the increase of carbon dioxide production and the resultant fall in end-tidal carbon dioxide tension reflects a fall in systemic arterial blood carbon dioxide tension. The greater respiratory exchange ratio during late pregnancy as compared with post partum also reflects this hyperventilation during pregnancy. Fourteen subjects with pregnancy-induced hypertension studied cross-sectionally failed to show any difference in the respiratory variables measured when compared with normotensive subjects at a similar length of gestation.

Adult↗
PubMed1989

Spirometric standards of Libyan boys and girls.

Ventilatory capacities of 578 Libyan boys and 527 Libyan girls aged between 12 and 21 years were measured. The data of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were analyzed by logarithmic regressions on age, standing height (stature), sitting height, body mass index and body surface area. The prediction formulae for pulmonary function in Libyan boys and girls were calculated. Standing height (stature) appears to be marginally better than sitting height as an index of body size in explaining the variance in ventilatory capacity of Libyan boys and girls. Libyan boys and girls have a greater proportional leg length than their British counterparts. Their mean values of FVC and FEV1 are lower than those of British children by about 13%. About 10% of Libyan boys are smokers. Below 14 years of age, there were no smokers. A steady rise in number of smokers from the age of 14 years reaching 41% at 21 years of age was observed. No smokers were reported from the Libyan girls. There was no statistically significant difference in the mean FVC or FEV1 between the smokers and nonsmokers.

Adolescent↗
PubMed1988

Effects of focusing attention on breathing with and without apparatus on the face.

In an attempt to identify a cause for the alteration in breathing pattern seen when conventional respiratory apparatus is applied to the face, we have studied the effects of causing the subject to focus attention on breathing by counting breaths in threes for 5 min. We used the respiratory inductance plethysmograph in 18 naive subjects who were unaware that their breathing was being measured. In the control periods, distraction was provided by a recorded story played through head-phones. The experiment was repeated with the rim of a facemask applied to the face. Focusing attention on breathing caused a prolongation of inspiration at a constant mean inspiratory flow, and lengthening of expiration. Tidal volume but not ventilation was increased. The facemask rim caused no significant change. It is concluded that conscious awareness of breathing could account for a major part of the effect of conventional respiratory apparatus.

Adolescent↗
PubMed1987

Validation of a simple mechanical accelerometer (pedometer) for the estimation of walking activity.

A small (28 g) mechanical accelerometer has been tested by subjecting it to controlled bench tests consisting of repetitive vertical oscillations on two designs of test rig. The accelerometer's 3-digit display provided a cumulated score with a maximum of 99.9 units. This score was compared with an independent count of the imposed oscillations and found to be linear with time (r = 0.996) and reproducible on retest (coefficient of variation = +/- 1.5%). The sensitivity ranged from 6.2 to 7.4 units/10,000 oscillations. The response was related to the maximal applied acceleration (calculated from the amplitude and frequency of the oscillations on the assumption that they were sinusoidal) and independent of the amplitude and frequency used. The threshold maximal acceleration was less than 2 m s-2 and the response had reached a plateau at 4 m s-2. During field studies the accelerometer was firmly attached over the hip in a waistband where it responded to the vertical accelerations produced by walking. When compared with an independent count of footsteps from a heel-mounted resistance pad the accelerometer score (after calibration) was not significantly different. The mean difference was (0.29 +/- 0.67, S.D.) 10(3) "steps" in a younger group (n = 8, mean age 39 years) and (0.46 +/- 1.08, S.D.) 10(3) "steps" in an older group of women (n = 6, mean age 65 years). Scores of around 10 X 10(3) "steps" can be expected in a day in moderately active young subjects and 40 X 10(3) "steps" in a week in the elderly. Simultaneously recorded scores from both right and left hips wee not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)

Acceleration↗
PubMed1987

The comparative effects of ICI 118551 and propranolol on essential tremor.

1. The effects of the selective beta 2-adrenoceptor antagonist ICI 118551 on essential tremor, heart rate and blood pressure were compared with those of propranolol. 2. ICI 118551 (150 mg daily for 7 days) and propranolol (120 mg daily for 7 days) were about equally effective in reducing essential tremor (by about 40%) and were more effective than placebo. 3. When compared with the effect of placebo, propranolol reduced blood pressure and exercise heart rate whereas ICI 118551 had no significant effect on blood pressure and produced a small but significant reduction in exercise-induced tachycardia. 4. ICI 118551 may be useful in the management of essential tremor while having fewer cardiovascular side-effects than non-selective beta-adrenoceptor antagonists.

Adrenergic beta-Antagonists↗
PubMed1987

Human orthostatic reflexes after taking temazepam at night.

1. Cardiovascular orthostatic reflexes have been studied at night in 12 healthy male subjects who were given two soft gelatin capsules each containing 0 or 10 mg temazepam at 21.30 h. 2. The changes in heart rate, blood pressure and forearm blood flow on consecutive 5 min exposures to lower body negative pressure (suction) at 30, 40 and 50 mm Hg were measured before and then 1.5 and 9.5 h after giving doses of 10 or 20 mg temazepam in a placebo-controlled double-blind cross-over study. 3. Pre-suction resting values were not affected by temazepam, but 1.5 h after giving the capsules there were significant differences in the responses to suction between the placebo and 20 mg temazepam experiments: the tachycardia after 20 mg temazepam was about one-third greater and the forearm vasoconstriction was about 50% less. The effect of the 10 mg dose was equivocal. No residual effects were detected the next morning. 4. These alterations in orthostatic reflexes soon after the administration of temazepam at night did not impair the maintenance of arterial blood pressure in these healthy subjects.

Adolescent↗
PubMed1987

Effects of aerial thermal fog applications of fenthion on caged pink shrimp, mysids and sheepshead minnows.

Mosquito control applications of fenthion by aerial thermal fog equipment were studied at 2 sites in Collier County, FL, for sprays that occurred on June 20 and 23, 1984. Acute, lethal effects of fenthion deposited in these estuarine habitats were assessed for caged pink shrimp (Penaeus duorarum), mysids (Mysidopsis bahia) and sheepshead minnows (Cyprinodon variegatus). At Site 1, along a bay with substantial dilution and tidal mixing, fenthion concentrations of 1.5 and 0.29 micrograms/liter were measured in samples taken immediately after both sprays. Concentrations decreased to less than or equal to 0.020 microgram/liter 12 h postspray and no mortality was observed for caged pink shrimp and mysids. Site 2 was along a residential canal system that offered limited dilution and mixing. Maximum concentrations were 2.6 and 0.51 micrograms/liter and measurable concentrations (greater than 0.038 microgram/liter) of fenthion persisted at this site for 4 days. Fenthion concentrations in surface waters were toxic to caged pink shrimp and mysids after both sprays. No mortality occurred among caged sheepshead minnows at either site.

Animals↗
PubMed1987

Vital capacity and airflow measured from partial flow-volume curves during 5 degrees head-down tilt.

Ten healthy young males were subjected to 7 min of 5 degrees head-down tilt, during which their forced vital capacity, peak flow rate (from complete flow-volume curves), and MEF 40% and 25% (airflows when 40% and 25% of the vital capacity remains in the lungs) from the partial curves were measured. The values of these variables and the heart rate and blood pressure were not significantly different from the values obtained in the supine position. In view of these findings it is concluded that the increase in the intra-thoracic blood volume, known to occur with 5 degrees head-down tilt used as a model for simulating weightlessness, does not embarrass respiratory mechanics.

Adult↗
PubMed1986

Objective measurements of customary physical activity in elderly men and women before and after retirement.

An objective method for assessing customary physical activity has been described, based on heart rate and footfall signals recorded on magnetic tape using small body-borne recorders. Computer analyses were used to obtain indices of the intensity and duration of periods of physical activity using both biosignals. Threshold values were set for each individual at a heart rate related to a standard walking speed of 4.8 km . h-1 (3 miles per hour). Four activity indices were defined in terms of time spent above this threshold and the intensity of the heart rate elevation above it, applying criteria relating to the duration of periods of activity or the concurrent activation of the walking signal. The choice and validity of these indices are discussed, and results for several groups of subjects presented. Three groups of subjects aged over 60 years were studied before and after retirement: twenty-five were steel-workers and thirty-nine were factory-workers (men and women). Rather low levels of activity were recorded. After one year of retirement the female factory workers showed a significant decrease in activity. In men this was found only after several years of retirement had elapsed.

Aged↗
PubMed1986

Ventilatory drive during face immersion in man.

Four series of experiments have been performed in normal subjects to determine whether face immersion gives rise to a reduction in ventilatory drive. Such a response might be advantageous, like the cardiovascular components of the 'diving response', in prolonging breath-hold diving. In the first series, ventilatory drive was measured indirectly as the maximal voluntary breath-holding time, starting each breath-hold at the same alveolar partial pressures and at the same lung volume. When the face was immersed in cold water, breath-holding times were increased by 14%. The breaking point occurred at a higher alveolar PCO2 and the rate of rise of PCO2 was not affected. Control immersions in warm water had no effect. In the second and third series, subjects lay prone and breathed either air or 5% CO2 through a valve in the bottom of a bowl. Minute ventilation was measured before, during and after 5 min of face immersion in cold water. Transient hypoventilations of 13% and 10% respectively were seen, accompanied by small rises in alveolar PCO2. In control experiments, immersion of the forearm in cold water produced the opposite responses. In the fourth series, a cold wet pack was applied to the face during moderate steady-state exercise. A small irregular hypoventilation was seen, but not in control experiments when a warm pack was applied. Face temperatures fell by about 10 degrees C in these experiments. No material changes were found in the temperatures of the inspired air or of the aural canal. It is concluded that face immersion in cold water causes a modest reduction in ventilatory drive in man. This appears to be a component of the 'diving response'.

Adult↗
PubMed1985

Relative sensitivity of six estuarine fishes to carbophenothion, chlorpyrifos, and fenvalerate.

The acute toxicity (96-hr LC50) of carbophenothion, chlorpyrifos, and fenvalerate to six estuarine fishes was determined in flow-through laboratory tests. The atherinid fishes (Menidia menidia, M. peninsulae, M. beryllina, and Leuresthes tenuis) consistently were among the most sensitive species tested and were similar to each other in their sensitivity to pesticides. The sensitivity of sheepshead minnows (Cyprinodon variegatus) to carbophenothion was the same as that of the atherinids. For fenvalerate, the sheepshead minnow LC50 was an order of magnitude greater than that of the most sensitive atherinid, whereas the LC50 for chlorpyrifos and sheepshead minnows was two orders of magnitude greater. Gulf toadfish (Opsanus beta) were the least sensitive fish tested with carbophenothion and chlorpyrifos and their 96-hr LC50 for fenvalerate ranked between the LC50 for sheepshead minnows and atherinids. Test results were compared to acute toxicity data for other estuarine fishes and invertebrates.

Animals↗
PubMed1985

The effect of a week's beta-adrenoceptor antagonism on daytime heart-rates, subjective responses to exercise, and physical activity in normal subjects.

The effects on heart rate (HR) and physical activity of 1 week's treatment with three different beta-adrenoceptor antagonists (20 mg betaxolol (Lorex); 160 mg propranolol LA; or 100 mg atenolol daily) have been compared with placebo in a double-blind study of 12 normal men. On the fifth day of each treatment a body-borne tape-recorder was worn during waking hours for recording of ECG and footfall signals. Each record was calibrated in terms of the subject's response to laboratory ergometer exercise, and a computer analysis provided objective indices of physical activity. While on beta-adrenoceptor antagonists the subjects perceived standard exercise as significantly harder than on placebo and reported more side-effects (albeit mild and transient). Ambulatory monitoring of HR showed that subjects spent 13% of their waking day at heart rates below 50 beats min-1 while on propranolol, compared with 1% on placebo and 20% on atenolol and betaxolol. On these latter drugs, the group spent as much as 10% of their waking time with HR below 45 beats min-1. The lowest individual heart-rates recorded were below 35 beats min-1. Objective indices of physical activity, such as the duration of periods spent with heart rates above the HR found at 100 W in the ergometer test, showed no differences between the treatments. This negative finding was confirmed by pedometer step counts over the whole week.

Adrenergic beta-Antagonists↗
PubMed1979

Ventilatory pattern following diazepam and lorazepam.

The effect of intravenous diazepam (10 mg) or lorazepam (2 mg) on the ventilatory pattern has been studied in two groups of ten patients prior to elective surgery. Injection of lorazepam was followed by a periodic pattern of ventilation in nine patients.

Adult↗
PubMed1979

The effect of beta-adrenoceptor blockade on factors affecting exercise tolerance in normal man.

1 We have studied the effects of single oral doses of 80 mg propranolol and 100 mg metoprolol on the cardiovascular and respiratory responses to progressive exercise in nine healthy men in double-blind, placebo-controlled experiment. As judged by their effects on exercise heart rate and cardiac output the doses of the two drugs used were equivalent. 2 Beta-adrenoceptor blockade reduced oxygen consumption by 3.5% over the whole work range with an increase in the respiratory exchange ratio of 0.056 units. Carbon dioxide production and exercise ventilation were unchanged. The two drugs had similar effects. Possible mechanisms for these observations are discussed. 3 Perceived exertion during exercise was increased by both the beta-adrenoceptor blocking drugs and this may be of relevance to the symptom of fatigue reported by patients on these drugs. Endurance, assessed as either total work done or maximal work achieved, was reduced by 15%.

Adrenergic beta-Antagonists↗