Venous occlusion plethysmography vs. Doppler ultrasound in the assessment of leg blood flow kinetics during different intensities of calf exercise.

PURPOSE: It has recently been shown that venous occlusion plethysmography (VOP) can successfully assess the rate of increase in leg blood flow (LBF) (LBF kinetics) responses during calf exercise, but there is lack of data supporting its validity. METHODS: Using Doppler ultrasound (DU) as a criterion standard technique, we tested the hypothesis that VOP would provide similar estimates of LBF kinetics responses as DU during calf plantar-flexion exercise at a range of different intensities. Ten healthy men performed repeated intermittent calf plantar-flexion contractions (3 s duty cycles, 1 s contraction/2 s relaxation) at 30, 50 and 70% maximum voluntary contraction (MVC) on different days. RESULTS: Resting LBF values were significantly (P < 0.05) larger for DU than VOP but the overall mean LBF responses during exercise were not different (P > 0.05) between DU and VOP (30% MVC: 330 ± 78 vs. 313 ± 92 ml/min; 50% MVC: 515 ± 145 vs. 483 ± 164 ml/min; 70% MVC: 733 ± 218 vs. 616 ± 229 ml/min). LBF kinetics analyses revealed that the end-amplitude at the highest intensity (70% MVC) was significantly higher when measured by DU compared with VOP, but all other kinetics parameters were not different between VOP and DU. CONCLUSIONS: Given that these slight differences in amplitude observed during exercise can be explained by differences in vascular regions which the two techniques assess, our results suggest that VOP can accurately assess LBF kinetics responses during calf plantar-flexion exercise at intensities between 30 and 70% MVC.

Assessment of problematic sexual interests with the penile plethysmograph: an overview of assessment laboratories.

Phallometric testing, or penile plethysmography (PPG), is an objective measure of sexual arousal for males. While extensive research on the reliability and validity of PPG has promoted its reputation as the "gold standard" of objective measurement of sexual arousal, there is a lack of standardization of stimulus sets and interpretation of results between sites. This article describes the laboratory protocol employed for PPG at the Royal Ottawa Mental Health Centre's Sexual Behaviours Clinic (SBC) in Ottawa, Ontario, as well as those used by the Sexual Behaviors Clinic and Lab (SBCL) in the Community and Public Safety Psychiatry Division (CPSPD) of the Department of Psychiatry and Behavioral Sciences at Medical University of South Carolina (MUSC) in Charleston, South Carolina. The need for standardization in both testing protocol and stimuli use across sites are highlighted.

Using eye tracking to identify faking attempts during penile plethysmography assessment.

Penile plethysmography (PPG) is considered the most rigorous method for sexual interest assessment. Nevertheless, it is subject to faking attempts by participants, which compromises the internal validity of the instrument. To date, various attempts have been made to limit voluntary control of sexual response during PPG assessments, without satisfactory results. This exploratory research examined eye-tracking technologies' ability to identify the presence of cognitive strategies responsible for erectile inhibition during PPG assessment. Eye movements and penile responses for 20 subjects were recorded while exploring animated human-like computer-generated stimuli in a virtual environment under three distinct viewing conditions: (a) the free visual exploration of a preferred sexual stimulus without erectile inhibition; (b) the viewing of a preferred sexual stimulus with erectile inhibition; and (c) the free visual exploration of a non-preferred sexual stimulus. Results suggest that attempts to control erectile responses generate specific eye-movement variations, characterized by a general deceleration of the exploration process and limited exploration of the erogenous zone. Findings indicate that recording eye movements can provide significant information on the presence of competing covert processes responsible for erectile inhibition. The use of eye-tracking technologies during PPG could therefore lead to improved internal validity of the plethysmographic procedure.

Non-invasive assessment of cardiac output at rest and during exercise by finger plethysmography.

AIMS: We sought to determine the accuracy of finger plethysmography using pulse waveform analysis with brachial calibration for measurement of cardiac output during submaximal exercise by comparing it against an acetylene (C2H2) uptake technique. METHODS: The study included 24 healthy volunteers (12 males, age 35 ± 8 years). Testing was performed on an upright cycle ergometer using an incremental protocol. Cardiac output measurements were performed at rest and during sub-maximal exercise using a single breath C2H2 uptake technique and continuously using finger plethysmography with brachial calibration. RESULTS: Valid results at rest and during sub-maximal exercise were achieved in 20 of 24 participants. Cardiac output at rest was 5.3 ± 1.1 and 5.2 ± 1.2 l min(-1) for finger plethysmography and C2H2, respectively, P = 0.712. Mean difference between techniques was -0.1 ± 0.5 l min(-1). Cardiac output during submaximal exercise was 10.2 ± 2.3 and 10.3 ± 2.1 l min(-1) for finger plethysmography and C2H2, respectively, P = 0.898. Mean difference between techniques was 0.1 ± 1.5 l min(-1). The overall correlation between finger plethysmography and C2H2 data obtained during rest and exercise was r(2) = 0.872, P<0.0001. Mean rise in cardiac output during exercise was 4.9 ± 1.5 (finger plethysmography) and 5.1 ± 1.5 l min(-1) (C2H2), P = 0.64. CONCLUSION: Finger plethysmography determined cardiac output values both at rest and during sub-maximal exercise are comparable with those obtained using a single breath C2H2 uptake technique.

An assessment of pulmonary function testing and ventilatory kinematics by optoelectronic plethysmography.

New advances in computer processing and imaging have allowed the development of innovative techniques to assess lung function. A promising methodology is optoelectronic plethysmography (OEP). OEP evaluates ventilatory kinematics through the use of infrared imaging. Markers are placed, and images read on the chest, back and abdomen of subjects. Currently, this system is used mainly in research settings, but in the future may have broad applicability to patient populations such as very young children, patients with neuromuscular disease and patients who cannot be tested with classical spirometry testing. This paper presents the history and development of OEP, along with a summary of the OEP methodology, a discussion of research findings and results to date, as well as application and limitations.

Blood pressure assessment during resistance exercise: comparison between auscultation and Finapres.

OBJECTIVES: The objective of this study was to test whether the auscultatory method and Finapres provide similar readings for blood pressure response during two resistance exercise protocols of different intensities, and to gain some insight into whether auscultation can be used to monitor cardiovascular stress during resistance exercise. METHODS: Fourteen patients performed six and 15 maximum repetitions (six and 15, respectively) of one-leg knee extension on different days. Blood pressure (BP) was measured simultaneously with the two methods at rest and during the last repetition of the protocols. RESULTS: Neither the systolic blood pressure (SBP) nor the diastolic blood pressure (DBP) differed between methods, both at rest and at six maximum repetitions. Conversely, Finapres recorded higher systolic blood pressure at 15 maximum repetitions (168.8+/-21.7 mmHg) than auscultation (147.0+/-14.5 mmHg; P<0.001). In addition, the blood pressure values obtained by both methods in each exercise protocol (six and 15 maximum repetitions, respectively) were ranked in tertiles and also treated by the gamma (gamma) nonparametric correlation. We observed a high probability for patients to be ranked on the same tertile regardless of the method used, at both six maximum repetitions (SBP=0.80, DBP=0.97) and 15 maximum repetitions (SBP=0.88, DBP=0.92). High association between methods was also observed by simple regression when measurements taken at rest and at each intensity were analyzed altogether for both SBP (r=0.95, r adjusted=0.89) and DBP (r=0.79, r adjusted=0.62). CONCLUSION: Auscultation provides lower BP values than Finapres, especially at the end of a set including 15 maximum repetitions. The former, however, seems appropriate to assess the relative cardiovascular stress imposed by different protocols of resistance exercise.

Comparison of two plethysmography systems in assessment of forearm blood flow.

Venous occlusion plethysmography is widely used to assess forearm blood flow (FBF). We compared the established Hokanson system (HEC4) with a newly developed Filtrass 2001 system (F2001). The HEC4 uses mercury-in-Silastic strain gauges, whereas F2001 detects volume changes with a nonmercury linear displacement device. The aim of this study was to evaluate the new F2001 against the HEC4 in terms of repeatability and systematic bias. Ten subjects were studied on 4 separate days in random order using either the HEC4 on both arms, the F2001 on both arms, the HEC4 on the right arm with the F2001 on the left, or the F2001 on the right arm and the HEC4 on the left. Stroop's colored word conflict test and postocclusive hyperemia were used to increase FBF, and lower body negative pressure was used to lower FBF. Stroop's colored word conflict test and lower body negative pressure increased (24.6 +/- 1.5%, n = 240, P < 0.0001) and decreased (18.7 +/- 0.8%, n = 240, P < 0.0001) FBF, respectively. Postocclusive hyperemia after occlusion times of 5, 8, and 13 min substantially increased FBF by 390 +/- 86, 756 +/- 217, and 851 +/- 132%, respectively. Repeatability was not different between the devices (0.10 +/- 2.37 vs. -0.47 +/- 1.92 l/min, n = 125, P > 0.05), and there was no systematic bias. The F2001 is a newly developed plethysmography system that does not utilize mercury and is suitable for assessing changes of FBF in physiological studies.

Within- and between-laboratory precision in the measurement of body volume using air displacement plethysmography and its effect on body composition assessment.

OBJECTIVE: To determine and compare the extent of within- and between-laboratory precision in body volume (BV) measurements using air displacement plethysmography (ADP), the BOD POD body composition system, and to interpret any such variability in terms of body composition estimates. DESIGN: Repeated test procedures of BV assessment using the BOD POD ADP were reproduced at two laboratories for the estimation of precision, both within and between laboratories. SUBJECTS: In total, 30 healthy adult volunteers, 14 men (age, 19-48 y; body mass index (BMI), 19.7-30.3 kg/m2) and 16 women (age, 19-40 y; BMI, 16.3-35.7 kg/m2), were each subjected to two test procedures at both laboratories. Two additional volunteers were independently subjected to 10 repeated test procedures at both laboratories. MEASUREMENTS: Repeated measurements of BV, uncorrected for the effects of isothermal air in the lungs and the surface area artifact, were obtained using the BOD POD ADP, with the identical protocol being faithfully applied at both laboratories. Uncorrected BV measurements were adjusted to give estimates of actual BV that were used to calculate body density (body weight (BWt)/actual BV) from which estimates of body composition were derived. The differences between repeated BV measurements or body composition estimates were used to assess within-laboratory precision (repeatability), as standard deviation (SD) and coefficient of variation; the differences between measurements reproduced at each laboratory were used to determine between-laboratory precision (reproducibility), as bias and 95% limits of agreement (from SD of the differences between laboratories). RESULTS: The extent of within-laboratory methodological precision for BV (uncorrected and actual) was variable according to subject, sample group and laboratory conditions (range of SD, 0.04-0.13 l), and was mostly due to within-individual biological variability (typically 78-99%) rather than to technical imprecision. There was a significant (P<0.05) bias between laboratories for the 10 repeats on the two independent subjects (up to 0.29 l). Although no significant bias (P=0.077) was evident for the sample group of 30 volunteers (-0.05 l), the 95% limits of agreement were considerable (-0.68 to 0.58 l). The effects of this variability in BV on body composition were relatively greater: for example, within-laboratory precision (SD) for body fat as % BWt was between 0.56 and 1.34% depending on the subject and laboratory; the bias (-0.59%) was not significant between laboratories, but there were large 95% limits of agreement (-3.67 to 2.50%). CONCLUSION: Within-laboratory precision for each BOD POD instrument was reasonably good, but was variable according to the prevailing conditions. Although the bias between the two instruments was not significant for the BV measurements, implying that they can be used interchangeably for groups of similar subjects, the relatively large 95% limits of agreement indicate that greater consideration may be needed for assessing individuals with different ADP instruments. Therefore, use of a single ADP instrument is apparently preferable when assessing individuals on a longitudinal basis.

The role of strain gauge plethysmography in the assessment of patients with suspected deep vein thrombosis.

Suspicion of deep vein thrombosis (DVT) is a common reason for medical referral to hospital. Clinical signs and symptoms are notoriously unreliable, hence there is the need for objective testing. Strain gauge plethysmography (SGP) has been marketed as a technique for excluding lower limb DVT. We therefore set out to evaluate this screening tool. Over a 2 year period, 437 consecutive patients referred with suspected DVT were assessed using both plethysmography and Doppler ultrasound. When the two techniques were compared, plethysmography was found to have a negative predictive value of 90%. We conclude that strain gauge plethysmography has a role in the screening of patients with suspected DVT but should not be used as the sole method in patient assessment.

Accuracy of nasal cannula pressure recordings for assessment of ventilation during sleep.

Nasal prong pressure monitoring (PNOSE) is utilized to assess ventilation during sleep. However, it has not been rigorously validated against the gold standard of face-mask pneumotachography (VFM). Therefore, we compared PNOSE with VFM in 20 patients with suspected sleep apnea during nocturnal polysomnography, and analyzed factors affecting accuracy of PNOSE-derived variables. Patients rated their nasal obstruction on a visual analog scale. Mean +/- SE apnea/hypopnea index (AHI) by VFM was 24.0 +/- 5.1 h(-1). The bias (mean difference) and limits of agreement (+/- 2 SD) of AHI derived from PNOSE, and square root-transformed PNOSE, a measure proposed as a surrogate of airflow, were +3.9 (+/- 4.6), and -0.9 (+/- 9.0) h(-1). Subjective scores of nasal obstruction before polysomnographies did not herald inaccuracy of AHI from PNOSE. Square root-transformed PNOSE closely tracked pneumotachographic airflow over 10 breaths (r(2) among signals 0.88 to 0.96) but the relationship among these signals was highly variable if comparisons were extended over an entire night. Compared with face-mask pneumotachography, nasal pressure monitoring provides accurate AHI for clinical purposes even in patients perceiving nasal obstruction. Square-root transformation provides near linear nasal pressure/airflow relationships over a short time but is not essential for estimation of AHI.

Digital pulse volume recording: an essential test for the assessment of arteritis in diabetic patients.

The high incidence of medial calcification in the distal arteries of lower extremities in diabetic patients is responsible for most of the errors made in measuring ankle-pressure index. Because digital arteries are rarely calcified, digital pulse volume recording has been proposed as a specific and complementary test. Between March 1993 and March 1996, this test was performed in addition to ankle-pressure index in 66 diabetic patients. The ankle-arm index was overestimated and erroneous in 89.4% of cases. Digital arteries were calcified in 74% of cases and diabetic neuropathy present in 53% of cases. Assessment of the severity of arteritis by digital pulse volume recording (category 1 to 5) has led to better prevention and treatment. It is an essential test for the assessment of arteritis in diabetics, but also for the prediction of success of a surgical procedure: distal amputation, lumbar sympathectomy and arterial reconstruction.

Accuracy of heart rate assessment in atrial fibrillation.

OBJECTIVE: To determine the most accurate technique to measure the heart rate during atrial fibrillation by use of three counting intervals, 15, 30, and 60 seconds, and two methods, apical and radial pulse measurement. DESIGN: A quasi-experimental, repeated measures factorial design was used to determine absolute error (amount of error ignoring direction of error) between heart rates obtained from six randomly ordered pulse measurements taken of one man in chronic atrial fibrillation by the 94 nurses in the sample and the heart rate recorded by simultaneous electrocardiographic (ECG) and plethysmographic (pleth) recordings. SUBJECTS: Nurses in four groups comprised the sample; registered nurses (N = 29), licensed practical nurses (N = 23), nursing students (N = 21), and registered nurses with advanced degrees who are clinical specialists and in faculty positions. RESULTS: The heart rate of the man varied from 57 to 111 beats/min (mean 81 beats/min). The mean absolute error rates for the six measurements ranged from 8 beats/min to 20 beats/min, all considered to be important when a 10% error was used as the criteria for clinical significance. The apical method was significantly more accurate than the radial method regardless of whether the ECG or pleth standard was used (ECG--F1.90 = 72.91, p less than 0.0001; pleth--F1.144 = 4.68, p = 0.036). The 60-second counting interval was significantly more accurate regardless of the standard (ECG--F2.180 = 5.19, p = 0.006; pleth--F2.88 = 3.95, p = 0.02). CONCLUSIONS: Atrial fibrillation occurs in 2% to 4% of people over 60 years of age and is one of the most difficult dysrhythmias to count. Accurate counts are important when making clinical decisions, yet measurement of heart rate in this study was quite inaccurate. The 60-second count and the apical method were the most accurate statistically, although differences in counting interval error rates were not clinically significant.

Antepartum assessment of the maternal peripheral venous system with light reflection rheology.

The noninvasive detection of deep venous thrombosis (DVT) in pregnancy is a significant problem. The Hemodynamics AV-1000 uses light reflection rheology in superficial capillaries to detect DVT but has not been evaluated adequately in pregnancy. Four hundred one pregnant women in the second and third trimesters were studied with the AV-1000; none had symptoms of DVT or thrombophlebitis, and all had uncomplicated pregnancy outcomes. AV-1000 reflection curves were related to maternal age, gestational age, weight gain, Quetelet index and device sensitivity settings. No statistically significant differences in test outcomes were found for any variable. The high incidence of abnormal (25%) and inadequate (19%) tracings, coupled with an overall specificity of 45%, suggests that the system would not be useful in distinguishing patients with DVT from normal ones and could lead to excessive follow-up testing.

Critical assessment of jacket plethysmographs for use in young children.

In infants and very young children changes in thoracic gas volume (Vtg) during tidal breathing and during intermittent positive-pressure lung inflations have been estimated from pressure changes within double-layered rubber jackets covering the thorax and abdomen. In vitro and in vivo assessments demonstrated the linearity of these jackets over the range of volume changes found in these young subjects during respiratory function tests, and the small intrajacket background pressure (2.5 cmH2O) had minimal effects on resting lung volume and lung mechanics. These jackets can be used to monitor tidal volume in quiet subjects, and if an intermittent positive-pressure inflation technique is used static compliance can be accurately measured. The hysteresis of natural rubber and the direct contact of the recording system with the subject renders it unsuitable for the measurement of lung mechanics during tidal breathing and for the estimation of Vtg during airway occlusions.