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Acute effects of ECT on the cerebral circulation in man. A computerized study by cerebral impedance plethysmography.
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Systolic time-interval evaluation by thermistor plethysmography during uninterrupted dynamic stress test in normals and in patients with coronary artery disease.
18 patients with coronary artery disease (CAD) and 21 normal subjects underwent a triangular bicycle exercise test. Systolic time intervals (STI) were calculated at rest and every 2 min during exercise. Under resting conditions, STI were similar in the two groups. During exercise, the ejection time index (ETI), i.e. left ventricular ejection time (LVET) corrected for HR, rose significantly more in CAD patients, as compared to normals. Pre-ejection period (PEP) was also differently affected by exercise in CAD patients, who showed a more shortened PEP (p less than 0.001) in the early stage of dynamic stress. PEP/LVET ratio, which in the control group decreased continuously, in CAD patients fell during exercise at lower work loads (p less than 0.001), whilst rose during strenuous exercise. Finally, significant differences (p less than 0.001) were found in the percent change (% delta) PEP/LVET ratio between the two groups during the early phase of exercise, in which no superimposition of single values was present. Therefore, this last parameter seems the most reliable to differentiate clearly CAD patients from normal subjects, but its use must be limited at early exercise.
[Whole body plethysmography. Methodological problems and practice in the determination of the intrathoracic gas volume and respiratory resistance in spontaneous breathing].
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[Critical considerations on the methodological basis of whole body plethysmography].
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[Evaluation of whole body plethysmography curves by means of a special slide rule].
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Comparing measurements of nasal resistance by body plethysmography and by rhinomanometry.
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[Ergometric body plethysmography (author's transl)].
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Bronchial inhalation challenge by plethysmography in asthmatic children.
A new technique for breath-by-breath controlled bronchial inhalation test is described, using the body plethysmographic method. The values of airway resistance (Raw) and of thoracic gas volume at resting expiratory level (TGV) have been compared to the data of total pulmonary flow resistance (R1), measured with the intraesophageal catheter method, and of functional residual capacity (FRC). The dynamic lung compliance (C1 dyn) was calcualted, too; the mechanical parameters of breathing (R1; Raw; C1 dyn) have been investigated on the same breathing cycles before, during and after respiratory challenges in symptom-free asthmatic children. Regarding the breath-to-breath variation of the parameters, a respiratory challenge is usually considered as positive, if the R1 or Raw values increase 100% or more. Out of 39 assays, "positive" challenges were observed in 14 casis regarding R1 values and in 11 cases regarding Raw values. "Doubtful" tests - i.e. +50% less than or equal to R1 or Raw less than 100% - were observed in 5 assays regarding R1 and in 7 cases regarding Raw. A decrease of more than 40% of C1 dyn was observed in 12 out of the 19 'positive' or 'doubtful-positive' challenges; the largest spontaneous breath-to-breath variation being +/- 25%. Such a decrease of C1 dyn is suggested as a sign of peripheral bronchial obstruction. An increase of more than 25% of TGV was observed in 11 out of 19 assays, considered "positive" or "doubtful-positive". A correlation being observed between C1 dyn decrease and TGV increase this latter parameter is suggested to be an additional sign of bronchial obstruction. Beside the practical problem of the interpretation of a respiratory challenge, these results are discussed from the phatophysiological point of view.
Muscle blood flow during exercise in intermittent claudication. Validation of the 133-xenon clearance technique: clinical use by comparison to plethysmography and walking distance.
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Volume-pressure analysis of reflex changes in forearm venous function. A method by mental arithmetic stress and radionuclide plethysmography.
Mental arithmetic stress is known to cause forearm arterial dilation, but the venous responses, including possible changes in the volume-pressure relation, have not been defined. Hence, 10 apparently normal subjects, eight men and two women, mean age 46 +/- 9 years, were studied before and during mental arithmetic stress. Changes in forearm venous volume were estimated with 99mTc blood pool scintigraphy. Group variability of this measurement technique was 1.8 +/- 2.3%. A brachial blood pressure cuff was used to obtain venous occluding pressures of 0, 10, 20, and 30 mm Hg. Mental arithmetic stress increased group systolic and diastolic blood pressure from 126 +/- 12 to 152 +/- 20 mm Hg and from 83 +/- 8 to 93 +/- 15 mm Hg, respectively (p less than 0.001). Heart rate increased from a mean of 75 +/- 15 to 85 +/- 17 beats/min (p less than 0.01). There was no evidence of interaction between or nonlinearity of the volume-pressure plots. Linear regression then yielded the equations V = 99.8 + 0.96P before and V = 86.3 + 0.96P during mental arithmetic stress, which represents a 13.5 +/- 1.6% decrease in forearm vascular volume (p less than 0.001). We conclude that 1) a linear relation exists between forearm venous volume and pressure at physiologic pressures before and during mental arithmetic stress; 2) mental arithmetic stress causes forearm venoconstriction; and 3) such venoconstriction takes place by a parallel shift in the volume-pressure relation (i.e., a shift in unstressed venous volume).
Assessment of the human splanchnic venous volume-pressure relation using radionuclide plethysmography. Effect of nitroglycerin.
BACKGROUND: No method exists to assess human splanchnic venous function, the most important region in terms of vascular capacity. METHODS AND RESULTS: We studied 25 stable patients without heart failure or hypertension to develop a method to assess the splanchnic venous volume-pressure (V-P) relation and to determine the effect of nitroglycerin (GTN). We used blood pool scintigraphy to assess changes in regional splanchnic vascular volume (SVV) and low levels of continuous positive airway pressure (CPAP) to passively alter venous pressure and thus, SVV. We postulated that the relation between SVV and the CPAP used would reflect the capacitance of the splanchnic venous bed and that changes in the position of this relation would provide a relative measurement of any change in capacitance. In 12 patients (group 1), the splanchnic vascular V-P curves were recorded before and 2, 9, and 20 minutes after 0.6 mg sublingual GTN; in eight patients (group 2), recordings were made at similar times before and after sublingual administration of placebo; in five patients (group 3), the hemodynamic effects of CPAP were assessed by means of right and left cardiac catheterization. Right atrial and femoral venous pressures increased (p < 0.001) and cardiac output fell (p < 0.05) during CPAP. There was an apparently linear relation between CPAP and SVV (r = 0.74-0.98); SVV increased an average of 7.4 +/- 2.2% (p < 0.001) by 12 cm H2O CPAP: The splanchnic vascular V-P curves were reproducible with minimal variability in SVV (+/- 2%, p > 0.2) in group 2. After administration of GTN, the splanchnic vascular V-P curve shifted away from the pressure axis in a parallel fashion by an average of 9.4 +/- 5.4% (p < 0.001). CONCLUSIONS: We have developed a reproducible noninvasive technique that may be used to assess human splanchnic venous V-P relations. We have demonstrated for the first time in humans that GTN exerts its dilatory effect by increasing the unstressed splanchnic venous volume.
Venous occlusion pressure plethysmography in the human upper limb.
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Noninvasive measurement of airway responsiveness in allergic mice using barometric plethysmography.
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Airway resistance as measured by body plethysmography versus measurements of expiratory flow rate.
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Use of closed circuit television and dual trace oscilloscopy to facilitate body plethysmography measurements.
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On line determination of lung volumes by plethysmography and digital computer.
This report describes a method of obtaining lung volumes on line with a minicomputer and whole body plethysmograph. The results of this approach were compared with standard methodology for a wide range of values and found to be in good agreement. This system can be readily implemented using standard hardware and laboratory techniques. Its advantages are its accuracy ,rapidity of data analysis, and retrieval; through the latter it allows for an assessment of such factors as variability of subject performance.
Calibration of respiratory induction plethysmography (Respitrace) in infants.
To determine whether the recently increased sensitivity of the variable frequency oscillator and the use of separate rib cage and abdominal transducers made calibration of the Respitrace system easier, we performed 106 different calibration procedures against a pneumotachygraph in 36 normal infants, 41 using 2 separate periods of quiet sleep, 49 using quiet and REM sleep, and 16 using 2 separate periods of REM sleep. When the calibration was done using 2 separate periods of quiet sleep, or using periods of quiet and REM sleep, a change of at least 50% in the amplitudes of both the abdominal and rib cage signals between the 2 sleep periods, gave accurate calibration factors in 92%, compared with only 30% when the amplitude of either signal changed by less than 50%. Calculation of the calibration factors can be done either by the least squares method or by solving simultaneous equations with no significant difference between the results.