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AIM: Only a limited number of studies, designed to establish normal values for sleep-related respiratory variables in children, have been reported, and all are non-European. The aim of this study was to expand the knowledge on normative data in children. METHODS: Subjects ranging from 6 to 16 years were recruited and underwent full polysomnography. Only subjects without sleep disordered breathing or other sleep problems as assessed by clinical history were included. RESULTS: Sixty subjects were studied ( = 11.7 +/- 2.6 years; 28 boys; = 118.8 +/- 30.6%). was 0.85 +/- 1.06 (range: 0.0-5.5). was 0.06 +/- 0.16 (range: 0.0-0.9); 11 patients had a total of 31 obstructive apneas. Only five obstructive hypopneas were detected with = 0.08 +/- 0.17 (range: 0.0-0.9). was 1.98 +/- 1.39 (range: 0.1-7.2). was 97.0 +/- 0.6% (range: 96.0-98.0); was 91.8 +/- 2.7% (range: 82.0-96.0); <% of total sleep time with SaO2 >or= 95%> was 98.7 +/- 2.1% (range: 90.8-100.0); was 0.8 +/- 0.9 (range: 0.0-4.9) and was 6.1 +/- 1.8 (range: 2.7-10.9). Snoring was detected in 15 patients (4 overweight subjects), with no difference in patient characteristics and sleep-related respiratory variables between snorers and non-snorers. Subjects in the overweight group (n = 22) had a lower SaO2nadir (90.8 +/- 2.7 vs. 92.4 +/- 2.6; P = 0.01) and a higher ODI (1.3 +/- 1.3 vs. 0.4 +/- 0.4; P = 0.0002) than their normal weight peers. CONCLUSION: Our data are in agreement with other non-European studies, designed to establish normal values in children.
Total respiratory resistance (Rrs) was measured by the application of a sine wave of airflow to the mouth at an oscillation frequency of 10 Hz. The instrument used was the Siemens Siregnost FD5. The Rrs data were correlated with height, age, sex, and weight in 73 patients and 29 healthy subjects. The patients took part in a rehabilitation program for restoration of their locomotion function. Both groups had normal lung function (VC, FEV1) and no signs of pulmonary disease. The only important determining factor for the value of the Rrs was height. The mean Rrs of 102 subjects was 0.29 +/- 0.08 kPa.1-1.s. Other studies gave values between 0.23 +/- 0.05 and 0.32 +/- 0.10 kPa.1-1.s.
Laboratory values taken from more than 13,000 newly admitted patients to the University of Alabama Hospital were analyzed using a percentile ranking system, and histograms for 24 laboratory tests were prepared. The percentile system is a better way to express test results than the classic normal range. The ability to correlate a test result with a clinical problem rises proportional to the degree of deviation from the midrange. Minor deviations frequently are without explanation, even after intensive clinical investigation. Invariably, great deviations are explainable. If one limits the interpretation of results to three ranges--abnormally low, abnormally high, and normal--much of the value of laboratory test interpretation is lost.
A quantitative determination of physiological levels of all-trans-retinoic acid (vitamin A acid) in human serum has been developed. A double-phase extraction of 3.5 ml of serum followed by a specific and sensitive high performance liquid chromatography procedure allowed measurement of levels down to 1 ng/ml. Serum concentrations in 37 fasting volunteers ranged from 2.7 to 4.2 ng/ml and fitted a normal-Gaussian distributional shape with a mean value of 3.5 ng/ml and SD of 0.4 ng/ml, as demonstrated by the Kolmogorov-Smirnov test.
Measurement of blood pressure together with applanation tonometry at the radial artery allows the reproducible assessment of various indexes of arterial stiffness, including the peripheral (PPp) and central pulse pressures (PPc) and the peripheral (Alp) and central augmentation indexes (Alc). We defined preliminary diagnostic thresholds, using the distributional characteristics of these hemodynamic measurements in a reference population. We randomly recruited 870 subjects from 3 European populations. PPp was the average difference between systolic and diastolic blood pressure measured five times at one home visit. For measurement of PPc, Alp and Alc, we used the SphygmoCor device. We selected subjects without hypertension, diabetes, dyslipidemia in need of medical treatment or previous or concomitant cardiovascular disease. The study population included 228 men and 306 women (mean age 34.9 years). All hemodynamic measurements were curvilinearly related to age, and Alp and Alc were lower in men than in women. In men at age 40, the upper 95% prediction bands of the relations of the hemodynamic measurements with age approximated 60 mmHg for PPp, 40 mmHg for PPc, 90% for Alp, and 30% for Alc. For PPc, Alp and Alc, these thresholds must be adjusted for age, leading to lower and higher thresholds at younger and older age, respectively. In addition, in women of any age, the Alp and Alc thresholds must be increased by 10% and 7%, respectively. Pending validation in prospective outcome studies, distributional characteristics of arterial stiffness indexes in a reference population can be used to generate operational thresholds for use in clinical practice.
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OBJECTIVE: To derive a normative database for nerve conduction values of the lateral antebrachial cutaneous nerve (LACN) using a large and varied subject population. DESIGN: Descriptive study. SETTING: Private office or university-based clinic. PARTICIPANTS: Volunteers (n = 213), recruited through advertisements, who met inclusion criteria. MAIN OUTCOME MEASURES: Onset latency, peak latency, baseline-to-peak amplitude, peak-to-peak amplitude, area, rise time, duration, side-to-side differences, and the effects of age, race, sex, height, and body mass index (BMI) were investigated on 213 healthy volunteers between the ages of 19 and 79 years. RESULTS: The mean +/- SD onset latency was 1.7+/-0.2 ms. The 95th and 97th percentile values for onset latency were 2 and 2.1 ms, respectively. Mean peak latency was 2.2+/-0.2 ms. Both the 95th and 97th percentile values for peak latency were 2.5 ms. Mean onset to peak amplitude was 18+/-10 microV. The 5th and 3rd percentile values for onset to peak amplitude were 6 and 5 microV, respectively. Mean peak-to-peak amplitude was 22+/-15 microV. The 5th and 3rd percentile values for peak-to-peak amplitude were 7 and 6 microV, respectively. Mean area was 11+/-7nV-s, mean rise time was 0.5+/-0.1 ms, and mean duration was 1.1+/-0.2 ms. Mean side-to-side difference was 0.1+/-0.2 ms for onset latency, 0.1+/-0.2 ms for peak latency, 1+/-12 microV for onset to peak amplitude, and 0+/-17 microV for peak-to-peak amplitude. Increasing age and BMI were associated with lower mean amplitudes, but did not affect the lower limits of normal. CONCLUSION: These normative values will be useful in electrodiagnostic study of the LACN.
To recognize the highly statistically significant circadian variability of blood pressure in pregnancy is to admit that the diagnosis of gestational hypertension or preeclampsia should be based not just on whether a casual blood pressure value is too high or too low, but rather on more pertinent questions: How long is blood pressure elevated above a given time-varying threshold? What is the excess blood pressure? When does most of the excess occur? Answers to these questions may be obtained by establishing (1) an adequate reference threshold for blood pressure and (2) a proper measurement of blood pressure elevation. Accordingly, we derived time-specified reference standards for blood pressure as a function of gestational age. We analyzed 1408 blood pressure series systematically sampled by ambulatory monitoring for 48 consecutive hours every 4 weeks from the first obstetric visit (usually within the first trimester of pregnancy) until delivery in 235 women with uncomplicated pregnancies. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual to avoid differences among women in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each trimester of pregnancy, in keeping with the trends in blood pressure along gestation previously documented. The method, derived on the basis of bootstrap techniques, does not need to assume normality or symmetry in the data, and therefore, it is highly appropriate to describe the circadian pattern of blood pressure variability. Results not only reflect expected changes in the tolerance limits as a function of gestational age, but also upper limits markedly below the thresholds currently used for diagnosing hypertension in pregnancy. The use of these time-qualified tolerance limits for the computation of a hyperbaric index as a measure of BP excess has already been show to provide high sensitivity and specificity in the early identification of gestational hypertension and preeclampsia.
In a group of 520 clinically healthy men employed in metallurgy, predicted values in the function of age, height and body weight were set up by multiple regression for VC, FEV1 RV, ERV, FRC, RV%TLC and for FEV1%VC in the function of age and for TLC in the function of height. In the tables are given predicted values for VC, FEV1, RV%TLC (based on equations of regression) for 9 intervals of age, height and body weight.
The effect of two methods for standardizing dual-energy X-ray absorptiometry (DXA) measurements on patient classification by the T-score has been determined for a group of over 2000 patients. The methods proposed by the International DXA Standardization Committee and the European Community's COMAC-BME group were used in conjunction with young reference data from the major DXA manufacturers, the COMAC-BME group and the third US National Health and Nutrition Examination Survey (NHANES III). The two standardization techniques produced dissimilar classifications as measured by the kappa statistic (kappa = 0.34-0.90), especially for the femoral neck, with up to 24.3% of patients reclassified from osteopenic to normal and 18.6% reclassified from osteoporotic to osteopenic when the standardization method was changed. Considering the effects of both reference data and standardization techniques together, there was a wide variation of patient classification, with the number of patients classified as osteoporotic varying from 9.6% to 21.1% for the postero-anterior spine L2-4 region and from 2.3% to 27.6% for the femoral neck. The agreement between different classifications ranged widely, from very poor to excellent (kappa = 0.02-0.98). The creation of standardized reference data must be an important priority in order to harmonize patient management using standardized BMD measurements. The choice of standardization technique, however, must be addressed in light of the results presented here.
BACKGROUND: Measurements of blood pressure (BP) together with applanation tonometry at the radial and femoral arteries allow for reproducible assessments of various indexes of arterial stiffness, including peripheral (PP(p)) and central (PP(c)) pulse pressures, peripheral (AI(p)) and central (AI(c)) augmentation indexes, and aortic pulse wave velocity (PWV). In the absence of an outcome-driven and ethnicity-specific reference frame, we defined preliminary diagnostic thresholds for subjects of African descent living in Africa, using the distributional characteristics of these hemodynamic measurements. METHODS: We randomly recruited 347 subjects from a South African population of African origins. The PP(p) was the average difference between systolic and diastolic BP measured five times consecutively at one home visit. For measurement of PP(c), AI(p), AI(c), and PWV, we used a high-fidelity micromanometer interfaced with a laptop computer running the SphygmoCor software. For analyses we selected 185 subjects without hypertension, diabetes, and previous or concomitant cardiovascular disease. RESULTS: Mean age (33.5 years) was similar in 77 men and 108 women. The PP(p), PP(c), AI(p), AI(c), and PWV significantly increased with age. The 95th prediction bands of this relation at age 30 years, approximated to 70 mm Hg for PP(p), 50 mm Hg for PP(c), 100% for AI(p), 40% for AI(c), and 8.0 m/sec for PWV. The aforementioned thresholds would need adjustment by approximately 2.5 mm Hg, 4.0 mm Hg, 10%, 6%, and 1.0 m/sec, respectively, for each decade that age differs from 30 years. CONCLUSIONS: Pending validation in prospective outcome-based studies 70 mm Hg for PP(p), 50 mm Hg for PP(c), 100% for AI(p), 40% for AI(c), and 8.0 m/sec might be considered as preliminary thresholds to diagnose increased arterial stiffness in young adult subjects of African descent.
The purpose of this study was to establish reference ranges for magnetic resonance imaging (MRI) measurements of the adult right ventricle stratified by gender. Cardiovascular MRI is increasingly used for evaluating the right ventricle in congenital and acquired heart disease, but gender-specific normative values are currently unavailable. Study participants included 500 subjects free of clinical cardiovascular disease who were participants in the Multi-Ethnic Study of Atherosclerosis (MESA). All subjects underwent MRI according to a standard protocol. The endocardial margins of the right ventricle were manually contoured on short-axis images, and right ventricular (RV) volumes were calculated using a summation-of-disks method. RV dimensions were measured on 4-chamber gradient-echo images and in the short-axis plane. Except for the ejection fraction, all unadjusted RV parameters were significantly greater in men than in women (p <0.001). In the entire study population, RV volumes and linear dimensions each correlated significantly with height (r = 0.38 to 0.64, p = 0.001 for all) and body surface area (r = 0.41 to 0.64, p = 0.001 for all). Gender differences persisted after adjustment for subject height. After adjustment for body surface area, volumetric variables remained significantly greater (p = 0.001) in men than in women. Even after adjusting for body surface area and height, Chinese participants had significantly lower RV volumes compared with Caucasians. In conclusion, gender-specific normal values for the adult right ventricle by MRI are presented. Cardiovascular MRI measures of RV volumes and linear dimensions differ significantly according to gender and body size. These values will be useful to differentiate RV health from diseases that result in abnormal RV structure and function.
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