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Biomedical subjects

N Atkins

Publications and source records attributed to N Atkins.

At least 73 records · Page 4Linked to original sources
PubMed1990

Inaccuracy of seven popular sphygmomanometers for home measurement of blood pressure.

Seven models, available commercially for the self-measurement of blood pressure, were subjected to a validation procedure in which three devices of each model were tested by observers who were trained to a high standard of accuracy. The models were the Omron HEM-400C, the Philips HP5308, the Healthcheck 'Cuffless' CX-5 060020, the Nissei Analogue Monitor, the Philips HP5306/B, the Systema Dr MI-150 and the Fortec Dr MI-100. The validation programme had a number of unique features which included assessment of interdevice variability before and after 1 month of home use, and a new form of analysis, which we term 'clinical', based on the likely influence of three grades of device inaccuracy on patient management. In the main validation phase, one device of each model was compared with simultaneous measurements made by two 'blinded' observers using a standard mercury sphygmomanometer (PyMaH Corporation, New Jersey, USA) in the same arm in 85 subjects with a wide range of blood pressures. Three models (the Healthcheck 'Cuffless' CX-5 060020, the Systema Dr MI-150 and the Fortec Dr MI-100) failed the interdevice variability tests and did not reach the main validation test. Two models (the Omron HEM-400C and the Philips HP5306/B) failed on the criteria set down by the American National Standard for Electronic or Automated Sphygmomanometers, as well as the 'clinical' criteria. The remaining two models (the Nissei Analogue Monitor and the Philips HP5308) were acceptable for the measurement of systolic blood pressure by both methods of analysis but failed in the 'clinical' analysis for diastolic blood pressure. The mercury sphygmomanometer was comfortably within the criteria for both methods of analysis.

Blood Pressure Determination↗
PubMed1990

The relative accuracy of simultaneous same arm, simultaneous opposite arm and sequential same arm measurements in the validation of automated blood pressure measuring devices.

With the increasing demand for accurate BP measuring devices there comes also the need for validation. Most validation procedures assess the accuracy of a test device against a known standard, most commonly a mercury sphygmomanometer. The best method for assessing device accuracy is to measure BP simultaneously in the same arm with the test device and a mercury sphygmomanometer. This is not always possible because the deflation mechanism of the test device interferes with the ability of an observer to auscultate the Korotkov sounds accurately. In this study a mathematical method of sequential comparison between the test device and a mercury standard in the same arm is described which is almost as accurate as simultaneous measurement in the same arm.

Adult↗
PubMed1990

The antihypertensive efficacy of ketanserin in the elderly evaluated by ambulatory blood pressure measurement.

To assess the role of the serotonin antagonist ketanserin in the management of hypertension in the elderly, 12 patients with a mean age of 68 years (range 60-79 years) were treated with ketanserin in a randomised double-blind placebo-controlled cross-over trial. Clinic BP, ambulatory BP, renal function, and pharmacokinetics were assessed. The doses of ketanserin used were 40 mg (ten patients) and 20 mg (two patients) twice daily for 8 weeks. Mean clinic sitting BP was reduced from 169 +/- 5/98 +/- 2 on placebo to 155 +/- 5/88 +/- 3 mmHg (NS/P less than 0.05/P less than 0.05) and standing pressure from 168 +/- 6/100 +/- 3 to 157 +/- 5/91 +/- 3 mmHg (NS/P less than 0.01). Mean ambulatory systolic BP was unaffected by active treatment (167 +/- 7 vs 164 +/- 5) while diastolic pressure was lowered from 99 +/- 2 to 94 +/- 2 mmHg (P less than 0.05). This effect appeared to be mainly confined to the first two hours after drug administration. Renal blood flow was unaltered by treatment. The mean plasma half-life of ketanserin was 20.9 +/- 5.5 hours. Side effects were minimal. In conclusion, while ketanserin may be effective as assessed in the clinic, its efficacy on ambulatory monitoring is substantially less impressive.

Aged↗
PubMed1989

The efficacy and duration of action of sustained-release verapamil in essential hypertension.

The blood-pressure (BP)-lowering efficacy of sustained-release verapamil, using both clinic and ambulatory measurements, was assessed in patients with essential hypertension. In study 1, a between-patient comparison, we compared verapamil (n = 12) with propranolol (n = 10). Dosage of each agent was titrated to achieve optimal clinic BP control and this dose was maintained for the duration of the study. Both agents lowered clinic systolic and diastolic BP. Mean daily ambulatory BP was also reduced with propranolol by 23/8 mm Hg and with verapamil by 13/8 mm Hg. The mean percentage reduction of systolic BP was significantly greater with propranolol (p less than 0.01). In study 2 we assessed the duration of action of sustained-release verapamil (240 mg once daily) in 14 patients. Both clinic and mean ambulatory BP were significantly reduced by 17/12 and 16/8 mm Hg, respectively, and this reduction was maintained throughout the day. We conclude that this formulation of sustained-release verapamil is effective in lowering blood pressure in mild-to-moderate hypertension and that once-daily dosage with 240 mg maintains ambulatory BP reduction throughout the dosing interval.

Adult↗
PubMed1988

The antihypertensive efficacy of verapamil in the elderly evaluated by ambulatory blood pressure measurement.

To assess the efficacy, tolerability and pharmacokinetics of verapamil in the elderly, ten patients with blood pressure greater than 160/90 mmHg were studied in a randomized double-blind placebo-controlled cross-over trial. Nine patients aged 75 (+/- 4.9) years completed the study. After titration, doses of verapamil varying from 40 to 120 mg (40 mg in four, 80 mg in one and 120 mg in four patients) twice daily for six weeks were taken. Mean (+/- SEM) clinic lying blood pressure was reduced on verapamil from 187 +/- 6.8/100 +/- 4.1 to 167 +/- 4.6/86 +/- 3.1 mmHg, [P less than 0.001). Mean ambulatory blood pressure was reduced from 174 +/- 1.4/95 +/- 1.0 to 169 +/- 1.3/90 +/- 0.8 mmHg, (P less than 0.01). Lying heart rate was significantly reduced but glomerular filtration rate, renal blood flow and mental function, were not altered by treatment. The mean plasma half-life of verapamil was 6.9 +/- 1.1 hours. Side effects were minimal. We conclude that verapamil is an effective blood pressure lowering agent in the elderly.

Aged↗
PubMed1983

Lectin binding to formalin-fixed paraffin sections.

Lectins are potentially useful tools in histopathology for the identification of carbohydrates and distinguishing cells according to their type, differentiation or function. Conjugated to fluorescent or enzyme labels, lectins are simple to use on fresh tissue but fixation and processing sequesters glycoconjugates and dissolves out fat-linked sugars. We describe here the use of labelled antibodies to lectins to localise sites of lectin binding and increase sensitivity, combined with trypsin and neuraminidase to reveal sequestered carbohydrates. Absorbing lectins with appropriate sugars establishes the specificity of binding and allows lectins to be used as sensitive and specific reagents.

Binding Sites↗
PubMed1982

Assessment of density dependent flow-volume parameters in nonsmokers and smokers. Measurement with spirometry, body plethysmography and respiratory inductive plethysmography.

The purpose of this investigation was to assess the density-dependent flow-volume components of the forced vital capacity using simultaneous spirometry, respiratory inductive plethysmography, and body plethysmography in the detection of small airway disease. The forced vital capacity was measured during air, helium-oxygen and sulfur-hexafluoride breathing to provide a range of gas density influences. Combining flow measured at the mouth with volume referenced to change in alveolar gas volume as measured by body or respiratory inductive plethysmography during helium-oxygen breathing accentuated the differences between nonsmokers and smokers because of the variable degree of alveolar gas compression occurring over the second half of FVC. The volume of isoflow obtained when comparing the helium and oxygen mixture to air also effectively separated nonsmokers from smokers. The utilization of the high density gas mixture, sulfur hexafluoride-oxygen during the FVC maneuver did not provide useful diagnostic information. Therefore, density-dependent flow-volume information using helium as a test gas alone or compared to air with a variety of analyses is a good approach to detection of early lung disease in smokers.

Adolescent↗
PubMed1982

Assessment of time-volume and flow-volume components of forced vital capacity. Measurement with spirometry, body plethysmography and respiratory inductive plethysmography in nonsmokers and smokers.

The purpose of this investigation was to assess the effectiveness of the time-volume and flow-volume components of the forced vital capacity measured by simultaneous spirometry, respiratory inductive plethysmography, and body plethysmography in detecting small airway disease. Spirometry measured the exit of gas from the lungs, whereas body plethysmography measured both the exit of gas and alveolar gas compression. Respiratory inductive plethysmography, which reflected change in thoracic volume, provided semi-quantitative data f both gas exit and alveolar gas compression which generally lay between spirometry and body plethysmography. In nine nonsmokers and 12 smokers (six with small airway disease as defined by abnormal closing volumes and alveolar uniformity), analysis of forced vital capacity revealed that the only test which differentiated nonsmokers from smokers was the higher spirometric estimation of maximum expiratory flow measured at 25 percent VC in nonsmokers. Combining flow measure at the mouth with volume referenced to change in alveolar gas volume as measured by body or respiratory inductive plethysmography did not differentiate nonsmokers from smokers. Moment analysis performed of forced vital capacity with all of the three devices did not distinguish nonsmokers from smokers. The data in this study and a review of other investigations indicate that the time-volume and flow-volume components of the forced vital capacity on air breathing are not very sensitive in detecting early lung disease in smokers.

Adolescent↗
PubMed1980

Rebreathing techniques for pulmonary capillary blood flow and tissue volume.

The variability of three methods of calculating pulmonary capillary blood flow (Qc) and pulmonary tissue plus capillary blood volume (Vt) during rebreathing was assessed in normal humans by using as markers acetylene, ethyl iodide, and dimethyl ether. The methods of analysis were as follows. Method I, the timing of the disappearance curves of the soluble gases was corrected by assuming that the C18O-disappearance curve intercepted at unity at time O. Method II, it was assumed that the acetylene Qc calculated by method I was correct; ethyl iodide and dimethyl ether Vt were solved by an equation using the disappearance slopes of these gases and the acetylene Qc value, thereby avoiding dependence on extrapolated intercept values. Method III, Vt was calculated by solving for a unique value of Qc between pairs of disappearance slopes of acetylene and dimethyl ether, acetylene and ethyl iodide, and ethyl iodide and dimethyl ether. Among the three methods, method I gave the most reproducible values for Vt as determined with acetylene or dimethyl ether. Using method I, both acetylene and dimethyl ether were equally acceptable gases for measurement of Vt; acetylene was a better marker for Qc measurements.

Adult↗
PubMed1980

Non-invasive measurement of ventilation during exercise using a respiratory inductive plethysmograph. I.

The respiratory inductive plethysmograph, a monitor of ventilation that does not require a connection from the airway, was validated against spirometry during moderate exercise using a bicycle ergometer and a treadmill. One hundred seventy-three of 200 breaths during bicycle exercise from 6 young adults and 211 of 242 breaths during treadmill walking were within +/- 20% of the tidal volumes measured by simultaneous spirometry. The respiratory inductive plethysmograph appears to be a useful non-invasive monitor of ventilation during exercise.

Adolescent↗
PubMed1980

Effects of breathing through external dead space on ventilation at rest and during exercise. II.

We used a new non-invasive monitor of ventilation, the respiratory inductive plethysmograph, to determine the effects of breathing through a mouthpiece (with nose clip) and breathing through external dead spaces on ventilation at rest and during exercise. Six normal young subjects were studied during 5-min sequential periods at rest, submaximal exercise on a bicycle at a work load of 800 kgm/min, and recovery. Not surprisingly, the imposition on the respiratory system of breathing through a mouthpiece (with nose clip) and with external dead spaces of 150, 250, and 350 ml produced progressively greater ventilation than natural breathing during rest and submaximal bicycle exercise. However, when the actual tidal volumes were corrected for the increase in ventilation caused by the external dead space, ventilation both at rest and during exercise with mouthpiece breathing still remained higher than natural breathing. These data suggest that breathing through a mouthpiece (with nose clip) and breathing through external dead spaces stimulates ventilation both at rest and during exercise.

Adult↗
PubMed1975

Diffusing capacity, membrane diffusing capacity, capillary blood volume, pulmonary tissue volume, and cardiac output measured by a rebreathing technique.

A rebreathing method for estimating diffusing capacity, membrane diffusing capacity, pulmonary capillary blood volume, pulmonary capillary blood flow, and pulmonary tissue volume consists of rebreathing into a bag for 15 sec while acetylene, (18O)-carbon monoxide, oxygen, and helium are continuously sampled by a mass spectrometer. Because the masses of carbon monoxide and nitrogen are nearly identical at 28, it was necessary to use a stable isotope, C18O, to distinguish this gas with the mass spectrometer. Comparison of the pulmonary capillary blood flow by the rebreathing technique with the simultaneously obtained indicator dilution measurement in anesthetized dogs revealed good agreement. Estimations of pulmonary tissue volume appeared to be quite reproducible and consistent; the values tended to be somewhat smaller and less variable among normal subjects than reported by other investigators. After subtraction of capillary blood volume, tissue volume was 311 plus or minus 73 ml at rest and increased significantly to 352 plus or minus 61 ml at 75 watts of exercise. Pulmonary tissue volume in dogs using the rebreathing method averaged 9.2 ml per kg of body weight, a mean comparable to previously reported estimates using the ether plethysmographic method. The slope of pulmonary capillary blood flow (cardiac output in normal subjects) as a function of oxygen consumption during exercise in normal subjects of 0.0060 times oxygen consumption in milliliter per min was identical to published values. The rebreathing technique provides a rapid, reliable, noninvasive method for estimating pulmonary hemodynamic parameters.

Acetylene↗
PubMed1974

Relationship between frequency dependence of lung compliance and distribution of ventilation.

The previously demonstrated empirical association between frequency dependence of lung compliance and distribution of ventilation, the latter determined by the N(2) washout technique, was confirmed by establishing a mathematical link between the two tests. By assuming a two-compartment system with known compliances and making corrections for Pendelluft and common dead space mixing effects, the ratio of dynamic to static compliance (C(dyn)/C(st)) for any respiratory frequency can be calculated from the compartmental analysis of the N(2) washout at a single respiratory frequency. By using these equations, a good correlation was found between calculated and measured C(dyn)/C(st) in dogs with artificially induced bronchial obstruction and in young smokers or young nonsmokers after carbachol inhalation. A two-compartment N(2) washout was demonstrated in 10 young healthy smokers at one or two respiratory frequencies whereas all 10 normal controls showed a single exponential curve. These findings indicate that the non-invasive N(2) washout test is capable of predicting C(dyn)/C(st) and at the same time gives a direct measure of gas distribution. Further, it appears to be a highly sensitive method for the detection of "small airway disease."

Adult↗