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Biomedical subjects

P C O'Brien

Publications and source records attributed to P C O'Brien.

At least 361 records · Page 20Linked to original sources
PubMed1976

A test for randomness.

A procedure is proposed for studying the hypothesis that a sequence of dichotomous random variables are independent and identically (randomly) distributed. The procedure is relatively sensitive to departures from randomness involving multiple clustering. An application to testing for Schwann cell disease is discussed. The distrubution of the sample coefficient of variation from an exponential distribution, a useful statistic in testing randomness for a continuous model, is also studied.

Biometry↗
PubMed1975

Computer interpretation of Frank vectorcardiogram in normal infant: Longitudinal and cross-sectional observations from birth to 2 years of age.

The evolution of the Frank vectorcardiogram (VCG) was studied from longitudinal observations (60 normal infants) and from cross-sectional observations (231 normal infants) from birth to two years of age. Age specific normal values for the Cartesian coordinates of 14 vectors including maximal QRS-T and timed vectors in the horizontal and frontal plane were determined with both methods of analysis. In longitudinally followed infants the most significant involution of right ventricular forces occurred between the newborn period and 7-14 weeks of age. These changes included disappearance of clockwise horizontal loop rotation and a leftward shift of maximal and terminal forces as well as a rightward shift of initial vectors. Longitudinal observations were useful for prediction of the normal Frank VCG in the 7 to 14-week-old infant from values observed in the newborn period and for prediction of the horizontal loop rotation throughout infancy. Cross-sectional data showed a wider range of normal values than longitudinal data in the same 7 to 14-week-old infants, but age specific normal values were well reflected between 4 and 24 months of age from cross-sectional data.

Age Factors↗
PubMed1975

Uremic neuropathy. III. Controlled study of restricted protein and fluid diet and infrequent hemodialysis versus conventional hemodialysis treatment.

The effect of a treatment schedule of restricted protein and fluid intake and of infrequent hemodialysis (schedule 1) as compared to a conventional hemodialysis treatment schedule (schedule 2) on the presence and severity of peripheral neuropathy has been studied in a small group of patients using a crossover design. Using the neurologic evaluation and quantitative assessment of cutaneous sensation and of nerve conduction as indices of peripheral nerve function, we have not demonstrated any worsening of peripheral nerve function from markedly curtailing the frequency of hemodialysis and modifying the diet. Because of the small size of the study, the preponderance of patients receiving the test treatment schedule first, and the possibility that nerve function slowly worsens with time, it is not possible to say with certainty that the test or the control treatment schedule might adversely affect peripheral nerve function. If such an effect is present it would appear to be small.

Adult↗
PubMedDate not supplied

Evaluation of three methods for estimating fetal weight.

Three ultrasonic methods for estimating fetal weight (Campbell, Warsof, and Shepard) were compared in 124 singleton pregnancies. Fetal abdominal circumference was obtained by use of a map measurer and from diameter measurements and the equation for the circumference of a circle. Campbell's formula for estimating fetal weight was superior between 2,000 and 4,000 g, whereas Shepard's method was slightly better below 2,000 g and over 4,000 g. Hence, varied fetal anthropometric characteristics make it mandatory that several methods be evaluated by each institution before one is selected. With the methods of Campbell and Shepard, use of diameter measurements and the equation for the circumference of a circle resulted in a more accurate estimated fetal weight than when a map measurer was used.

Adult↗
PubMedDate not supplied

Lumbar motoneurons of man: I) number and diameter histogram of alpha and gamma axons of ventral root.

The numbers of large and intermediate diameter myelinated fibers of 17 ventral lumbar (L3, L4 and L5) spinal roots (vsr) of man (ages 17-81 years) have been evaluated using the improved methods of histologic processing and morphometry now available, semi-automatic methods of measurement and programmed calculation and plotting. A population of small diameter myelinated fibers as found in thoracic (T11) vsr, which are presumed to be preganglionic sympathetic fibers, were essentially absent from L3, L4 and L5 roots. On the average, there were 5716 (70%) large diameter fibers and 2625 (30%) intermediate diameter fibers in the L3 ventral spinal root. Comparable figures for L4 vsr were 4900 (70%) and 2152 30%) and for L5 vsr were 5043 (75%) and 1559 (25%). On the assumption that these lumbar roots contain few if any small diameter myelinated pre-ganglionic sympathetic axons, the large diameter fibers correspond to alpha motoneuron axons and the small diameter fibers to gamma motoneuron axons. With age, a decrease in the number of myelinated fibers was estimated to be 350 fibers per decade (approximately 5% per decade).

Adolescent↗
PubMedDate not supplied

Dynamic changes of nasal resistance.

Fifty human subjects were studied and evaluated utilizing posterior rhinomanometry techniques. The main purpose of the investigation was to study the physiologic dynamic range of nasal resistance so that the data might serve as a baseline, not only for evaluation and diagnosis of pathologic states but also for the assessment of nasal responses to various physiologic, drug-induced, or pathologic challenges. Analysis was divided into two parts: first, the evaluation of the average resistance and average change in resistance for each patient, and second, determination of the maximal amount of change to be expected over 15-minute periods in a healthy subject. These studies give the investigator an idea of the magnitude of change that one might expect in normal physiologic situations, based on the 50 subjects that allowed 1,272 observations for justification of the concept of percent change in nasal resistance and not the value of nasal resistance alone. We concluded that the physiologic change in nasal resistance in a normal individual during a 15-minute interval should be less than 53% of the previous observation of nasal resistance. A change greater than 53% suggests a significant change that cannot be attributed to physiologic variability.

Adolescent↗
PubMedDate not supplied

Vibratory and cooling detection thresholds compared with other tests in diagnosing and staging diabetic neuropathy.

Increasingly more tests are being used to detect and characterize diabetic polyneuropathy, but their value in setting minimal criteria for the diagnosis of neuropathy and for staging severity remains inadequately studied. In 180 diabetics, we compared the percentage of patients with test abnormalities and associations among test results, evaluating neuropathic symptoms [neuropathy symptom score (NSS) and neuropathy scale of neuropathy symptom profile (NNSP)], deficits [neurologic disability score (NDS) and vibratory (VDT) and cooling (CDT) detection thresholds], or nerve dysfunction [nerve conduction (NC)]. The percentage of patients that were abnormal varied considerably depending on criteria for abnormality and the tests used. Abnormality (greater than or equal to 3 SD of 1 or more parameters) of NC of one or more of four nerves occurred in 80%, of two or more in 69%, of three or more in 46%, and of four in 21%. Similarly, for other tests, the rate of abnormality decreased with use of increasingly stringent criteria. Setting the criteria for abnormal NC at abnormality of two or more nerves, NSS at greater than or equal to 1, NDS at greater than 6, NNSP at greater than or equal to 97.5th percentile, and at greater than or equal to 95th percentile for the other tests, NC was abnormal in 69%, NSS in 54%, NDS in 48%, NNSP in 47%, VDT in 44%, and CDT in 35%. Abnormality of any two or more of the six tests evaluated occurred in 64% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗