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PubMed2005

Noninvasive assessment of lung volume: respiratory inductance plethysmography and electrical impedance tomography.

OBJECTIVE: Respiratory inductance plethysmography (RIP) and electrical impedance tomography (EIT) are two monitoring techniques that have been used to assess lung volume noninvasively. METHODS: RIP uses two elastic bands around the chest and abdomen to assess global changes in lung volume. In animal models, RIP has been shown to detect changes in lung mechanics during high-frequency oscillatory ventilation and has the potential to quantify lung volumes noninvasively. EIT measures regional impedance changes with 16 electrodes around the patient's chest, each of them injecting and receiving small currents. Impedance changes have been correlated with volume changes in animal models and in humans. In a recent animal model, EIT was shown to be capable of tracking lung volume changes during high-frequency oscillatory ventilation. CONCLUSION: The promise of monitoring techniques such as RIP and EIT is that they will guide lung protective ventilation strategies and allow the clinician to optimize lung recruitment, maintain an open lung, and limit overdistension. EIT is the only bedside method that allows repeated, noninvasive measurements of regional lung volumes. In the future, it will be important to standardize the definitions of alveolar recruitment and ultimately demonstrate the superiority of EIT-guided ventilator management in providing lung protective ventilation.

Animals↗
PubMed1997

Evaluation of respiratory inductive plethysmography: accuracy for analysis of respiratory waveforms.

OBJECTIVE: To assess the accuracy of respiratory inductive plethysmography (RIP) waveforms to those obtained with whole body plethysmograph (BP) as this device gives a plethysmographic signal and a pneumotachograph (PNT). DESIGN: Randomized controlled trial. SETTING: Physiologic laboratory in a university hospital. PARTICIPANTS: Eleven subjects from the laboratory staff. INTERVENTIONS: This study was achieved during four consecutive periods in subjects breathing spontaneously and through different added resistive loads. Using the least square method calibration, two RIP waveforms, VRIP.BP(t) and VRIP.PNT(t), were simultaneously calculated with coefficients obtained from BP and from PNT volume waveforms, respectively VBP(t) and VPNT(t). For each recording, to compare volume waveforms, we calculated their differences in term of distances, DRIP-BP and DRIP-PNT, between the normalized RIP volume signal (respectively, VRIP.BP[t] and VRIP.PNT[t]) and its normalized reference (respectively, VBP[t] and VPNT[t]). We also calculated the distance DPNT-BP between the two normalized references VBP(t) and VPNT(t). RESULTS: No significant effect of load or time on the distance occurred. Including all the recordings, the mean distance DRIP-BP (3.4+/-1.1%) appears significantly lower than both the mean distance DRIP-PNT (4.5+/-1.3%; p<0.04) and the mean distance DPNT-BP (4.6+/-0.9%; p<0.008). For each period or load level, DRIP-BP appears to be lower than DRIP-PNT and DPNT-BP. CONCLUSION: The RIP seems reasonably accurate for analysis of respiratory waveform while subjects subsequently breathe against resistive loads.

Adult↗
PubMed2003

Detection of speaking with a new respiratory inductive plethysmography system.

The LifeShirt system, a garment with integrated sensors connected to a handheld computer, allows recording of a wide variety of clinically important cardiorespiratory data continuously for extended periods outside the laboratory or clinic. The device includes sensors for assessment of physical activity and posture since both can affect physiological activation and need to be controlled. Speaking is another potential confounding factor in the interpretation of physiological data. Auditory speech recording is problematic because it can pick up sources other than the person's voice (external microphone) or is obtrusive (throat microphone). The abdominal and thoracic calibrated respiratory inductive plethysmography (RIP) sensors integrated in the LifeShirt system might be an adequate alternative for detecting speech. In a laboratory experiment we determined respiratory parameters indicative of speech. Eighteen subjects were instructed to sit quietly, write, and speak continuously, for 4 min each. Nine parameters were derived from the RIP signals and averaged over each minute. In addition, nine variability parameters were computed as their coefficients of breath-by-breath variation. Inspiratory/expiratory time (IE-ratio) best distinguished speaking from writing with 98% correct classification at a cutoff criterion of 0.52. This criterion was equally successful in distinguishing speaking from sitting quietly. Discriminant analyses indicated that linear combinations of IE-ratio and a variety of other parameters did not reliably improve classification accuracy across tasks and replications. These results demonstrate the high efficacy of RIP-derived IE-ratio for speech detection and suggest that auditory recording is not necessary for detection of speech in ambulatory assessment.

Adult↗
PubMed1982

Mechanical plethysmography and Doppler ultrasound. Diagnosis of deep-venous thrombosis.

Two hundred eighty-one patients were available for follow-up after undergoing bilateral lower-extremity venous laboratory evaluations for possible deep-venous thrombosis. Because of a recognized difficulty with such a clinical diagnosis, the use of Doppler ultrasound and mechanical plethysmography with air-filled cuffs was carefully studied. Eighty-three of the 281 patients had confirmatory results from venography or fibrinogen scan of the symptomatic or more-symptomatic leg, and these 83 patients were used to determine accuracy. The complete evaluation as performed was accurate in 70% of the patients with suspected deep-venous thrombosis. The Doppler examination alone was accurate in 71% of the patients, and the maximum venous outflow measurement was accurate in 67% of the patients. This study indicates a continuing need for venography or fibrinogen scanning for the diagnosis of deep-venous thrombosis.

Adolescent↗
PubMed1982

Suspected deep vein thrombosis. Management by impedance plethysmography.

Controversy exists as to whether patients suspected of having deep vein thrombosis (DVT) can be studied safely without venography, with its attendant expense, inconvenience, and potential risk. We used impedance plethysmography (IPG) in 1,464 consecutive patients suspected of having DVT, with 96% of these patients with normal IPGs, there were no fatal pulmonary emboli (PE). The incidence of nonfatal PE was 1%. In 284 outpatients suspected of having DVT, but discharged without treatment because of normal IPGs, only one patient returned with subsequent symptoms of DVT (0.4%). Noninvasive testing with IPG is a safe and highly cost-effective alternative to venography for routine management of patients suspected of DVT.

Adolescent↗
PubMed1984

Noninvasive evaluation of chronic venous insufficiency. Use of foot mercury strain-gauge plethysmography.

Twenty-seven patients (40 extremities) with chronic venous insufficiency and 30 controls (60 extremities) were studied using noninvasive measurements of foot volume (foot mercury strain-gauge plethysmography [FMSGP]). Tests were performed with exercise (sitting) and with elevation (Trendelenburg), with and without tourniquets, to evaluate muscle pump efficiency and valvular competence. Empiric venous sufficiency indexes were calculated for exercise and for Trendelenburg's test. Test results were compared with invasive ambulatory venous pressure (AVP) data (13) and with ascending and retrograde venography (25). Distinctive plethysmographic patterns revealed the insufficiency was saphenous (four), calf perforators (14), saphenous plus perforators (seven), and deep venous (15), including occlusion (four). Correlation with AVP and venography was good but FMSGP was more discriminating, providing precise anatomical information, better reproducibility, and distinguishing poor muscle pump function from regurgitation. Patients accept FMSGP well. Repeated postoperative data are readily obtained for evaluation of surgical procedures.

Chronic Disease↗
PubMed1996

Occlusion maneuver to detect the relative contribution of the rib cage and abdomen to tidal volume using respiratory inductive plethysmography in infants.

Respiratory inductive plethysmography (RIP) records movements of the rib cage (RC) and abdomen (AB). A calibration procedure is needed to determine their relative contribution to tidal volume. We evaluated the hypothesis that the relative contribution of the RC and AB could be defined from respiratory efforts made during a brief occlusion of the airways in 10 infants aged 6.5-19 months, who were studied in quiet sleep. Six occlusions were performed during tidal breathing, with and without a pneumotachograph (PNT) and face mask in place. We analyzed the periods of occluded respiratory effort when RC and AB were in opposite directions (paradoxical movements), plotting RC vs. AB and performing a least-squares linear regression to estimate the ratio of the coefficients of AB/RC. Multiple linear regression of AB and RC over tidal volume during about 100 seconds of tidal breathing provided a reference standard. A ratio of 1 means that AB and RC make equal contributions to tidal volume. The feasibility of the occlusion maneuver was poor; only 51% of occlusions with PNT and 54% without led to a paradoxical movement with a good fit (r > 0.9). The mean coefficient of variation (range) was 9.35% (3.9-15.3%) with PNT and 12.1% (2.5%-26.3%) without it. The accuracy was very poor, with the mean AB/RC value being 0.94 with occlusions and 2.39 with multiple linear regression. The mean difference was 1.45 (SD 0.80), yielding 95% confidence limits for the difference of 0.12-3.01. We concluded that, due to its very poor accuracy and feasibility, the occlusion technique is not a useful method to calibrate RIP in infancy.

Abdomen↗
PubMed1997

Assessment of tidal volume over time in preterm infants using respiratory inductance plethysmography, The CHIME Study Group. Collaborative Home Infant Monitoring Evaluation.

Non-invasive techniques for monitoring ventilation in infants are widely used in short-term laboratory-studies but have not been evaluated in routine clinical settings. To determine whether respiratory inductance plethysmography (RIP) can provide reproducible measurements of tidal volume (VT) in premature infants over an extended period of time, we monitored respiration in eight healthy preterm infants over 4.9 +/- 1.0 hours (mean +/- SD). The algebraic sum (Sum) of rib cage (RC) and abdominal (AB) motion signals (obtained by RIP) was calculated and presented over the entire recording period as percent of an initial 5 minute calibration period. VT was simultaneously measured with a nasal mask pneumotachometer with infants in prone and supine positions during active and quiet sleep. Infants were studied in the morning (AM) and again in the afternoon (PM). Between these studies they were returned to the nursery wearing the RIP in a continuous record mode. For all patients there was a significant linear relationship between VT (in mL measured by pneumotachometer) and Sum (in % of calibration value, RIP). Neither the slope of the relationship (0.074 +/- 0.03 in AM vs. 0.071 +/- 0.02 in PM), nor its variability as measured by standard error of the estimate (SEE) (2.3 +/- 0.5 in AM vs. 2.5 +/- 0.8 in PM) changed significantly from AM to PM. The relationship between VT and Sum, as well as the variability of that relationship, was not altered by position, asynchrony of RC and AB, respiratory rate, or percent RC contribution to Sum. We conclude that RIP produces consistent measurements of respiratory effort over 5 hours in healthy preterm infants without need for recalibration and is not affected by routine care.

Female↗
PubMed1999

Bronchial challenge with carbachol in 3-6-year-old children: body plethysmography assessments.

Several studies of airway responsiveness in young children (3-6 years old) have been reported, but few have attempted measurements of airway resistance by body plethysmography. Therefore, we decided to study nonspecific bronchial responsiveness following cumulative doses of inhaled carbachol in 44 children with clinical asthma (CA group), 44 children with chronic cough (CC group), 38 children with wheezy bronchitis in the first 2 years of life (WB group), and 40 controls. Specific airway resistance (sRaw) was measured in a body plethysmograph, and specific airway conductance (sGaw=1/sRaw) was calculated. Two parameters were used to assess individual bronchial responses: 1) PD100 (the dose of carbachol which induced a 100% increase in sRaw), and 2) bronchial reactivity (BR), i.e., the slope of the log-dose sGaw response to carbachol. Significant differences were observed in PD100 and BR between the control group and the three groups of young patients (P < 0.001). Moreover, PD100 of the CA group was significantly lower than in the CC group (83.1 +/- 7.8 microg vs. 108.0 +/- 10.2 microg, respectively, P < 0.05), but was similar to the WB group PD100 (94.4 +/- 8.5 microg). BR in the CA group was significantly higher than in both the CC and WB groups (0.127 +/- 0.009 cm H2O-L.sec(-1) x log microg(-1) vs. 0.073 +/- 0.006 cm H2O(-1) x sec(-1) x log microg(-1) and 0.082 +/- 0.006 cm H2O(-1) x sec(-1) x log microg(-1), respectively, P < 0.001). Repeatability and coefficients of variation were always acceptable. Continuous SaO2 monitoring in some children of the CA group demonstrated the safety of the method, which is proposed as a technique in future studies.

Asthma↗
PubMed1999

Tidal breathing parameters in young children: comparison of measurement by respiratory inductance plethysmography to a facemask pneumotachograph system.

The ratio of expiratory time at tidal peak flow to total expiratory time (t(ptef)/t(e)) correlates with conventional measures of airway obstruction. It is usually assessed using a facemask and pneumotachograph system which may be poorly tolerated in young children and hence limits the usefulness of this technique. We therefore determined in young asthmatic children the accuracy of t(ptef)/t(e), using an uncalibrated respiratory inductance plethysmograph (RIP), and compared the results with those from a facemask-pneumotachograph system. We also assessed whether age influenced the agreement between measurements using the two devices. Forty-seven children aged between 1 month and 12 years were recruited: 39 were inpatients recovering from an acute wheezy episode, and 8 were recruited from the asthma clinic. All were receiving bronchodilators. Tidal breathing parameters t(ptef)/t(e), the duty cycle (t(i)/t(tot)), and respiratory rate were initially measured using the Respitrace alone and then simultaneously with both the Respitrace and the facemask-pneumotachograph system. Eight children did not tolerate the facemask, and in two others it was impossible to analyze the Respitrace trace due to artefacts. In the remaining 37 children, the reliability coefficients and coefficients of variation of the two techniques were similar. Similar values of t(i)/t(tot) and respiratory rate were obtained using the two devices. The mean t(ptef)/t(e) obtained using the Respitrace was lower than with the facemask-pneumotachograph system (P < 0.01), although this was age group-dependent (P < 0.05), as the difference was less apparent in the 1 to 2-year-old children than in other age groups. Application of the facemask-pneumotachograph system did not significantly influence the results obtained using the Respitrace. We conclude that uncalibrated respiratory inductance plethysmography can measure tidal breathing parameters as reliably as a facemask-pneumotachograph system in young asthmatic children, and is better tolerated than the pneumotachograph system. The results obtained using the two devices are not interchangeable.

Age Factors↗
PubMed2000

Interrupter technique versus plethysmography for measurement of respiratory resistance in children with asthma or cystic fibrosis.

The purpose of the present study was to compare measurements of respiratory system resistance by the interrupter method (Rrsint) with those of airway resistance by plethysmography (Raw) in nonobstructed children with asthma or cystic fibrosis (ratio of forced expiratory volume in 1 sec to vital capacity, FEV(1)/VC >/=80% with a forced expiratory flow rate between 25-75% of forced vital capacity, FEF(25-75) >/=75% of normal values) and in obstructed children with the same diseases (FEV(1)/VC <80% and/or FEF(25-75) <75% of normal values). Eighty-one children (47 asthmatics and 34 suffering from cystic fibrosis) aged 5-18 years (mean 11.2 +/- SD 3.4 years) were included in the study. For the overall group, we observed generally lower values for Raw (4.7 +/- 2. 8 cmH(2)O.L(-).s) than for Rrsint20 (extrapolation of the mouth pressure during occlusion to 40 ms after interruption) (5.6 +/- 1.7 cmH(2)O.L(-1).s) (P < 0.02), or for Rrsint40 (extrapolation of the mouth pressure during occlusion to 60 ms after interruption) (6.6 +/- 2.2 cmH(2)O.L(-1).s) (P < 0.001), but there was no difference between Rrsint20 and Raw in the obstructed subgroup. Moreover, we observed a correlation between the difference (Rrsint20 - Raw) expressed in percentage of predicted values and the degree of obstruction estimated by FEV(1)/VC (r = 0.56, P < 0.001). The differences between the specific resistances (sRrsint20 - sRaw, sRrsint40 - sRaw) were also correlated with the severity of the obstruction (r = 0.65, P < 0.001 and r = 0.57, P < 0.001, respectively). We observed also that the tendency to underestimate resistance by Rrsint in obstructed children was not the same in children with asthma and cystic fibrosis. We conclude that the tendency of Rrsint, as measured with our method, to underestimate airway obstruction appears to increase in proportion to the severity of the airway obstruction.

Adolescent↗
PubMed1997

Simultaneous determination of muscle perfusion and oxygenation by interleaved NMR plethysmography and deoxymyoglobin spectroscopy.

A novel approach is presented that combines NMR-plethysmography and NMRS of deoxymyoglobin in real-time, using line-by-line interleaved acquisitions of both gradient echo images during venous occlusion and of the N-delta proton signal of myoglobin's proximal F8 histidine. This method allowed simultaneous measurement of peripheral regional perfusion and skeletal muscle oxygen content. During reactive hyperaemia, using our combined NMRI-NMRS protocol, we explored the relationship between muscle reoxygenation (myoglobin resaturation half-time, y in s) and reperfusion (x in ml/100 g tissue/min) and found it to be highly significant (y = 70.83x-0.94; r2 = 0.70; F = 64.40; p = 9.73 x 10(-9). We also demonstrated that at low flow, muscle perfusion was a rate-limiting factor to reoxygenation. Making certain hypotheses, muscle oxygen extraction was derived from perfusion and myoglobin resaturation rate. Muscle oxygen extraction during early post-ischemic recovery (0.78 +/- 0.11, 0.79 +/- 0.09 and 0.72 +/- 0.05 at 0, 60 and 100 Torr counter-pressure, respectively) was shown to be independent of perfusion and maximum at each step of the protocol in most volunteers but also to display significant variability among subjects in this supposedly normal population sample.

Adult↗
PubMed1979

Ambulatory calf volume plethysmography in the assessment of venous insufficiency.

Ambulatory calf volume plethysmography has been used to study venous insufficiency in 50 lower limbs. The results demonstrate that it is possible to determine the presence of venous insufficiency and differentiate between normal limbs, limbs with superficial venous insufficiency only, limbs with deep venous insufficiency and limbs with deep venous insufficiency and occlusion by determining the ambulatory volume change and maximum venous outflow or venous volume.

Female↗
PubMed1990

Correspondence between forced oscillation and body plethysmography during bronchoprovocation with carbachol in children.

We compared dose-response curves obtained with the forced oscillation technique (FOT) and with body plethysmography during bronchoprovocation in children. In 40 stable asthmatic children (age, 5-16 yr) we performed challenges with doubling concentrations of inhaled carbachol (0.15-10 mg/mL) until specific airway resistance SRaw had increased by 100% (PC100SRaw). The FOT-response was assessed by total respiratory system resistance (Rrs, cmH2O.1(-1).s) and reactance (Xrs, cmH2O.1(-1).s) from 8 to 26 Hz, expressed as mean Rrs (Rrs), mean Xrs (Xrs), Rrs at 8 Hz (Rrs8), and mean slope of Rrs (dRrs/df). Dose-response curves were analyzed for threshold concentrations (TC) causing a 3 SD change from baseline and sensitivity indices (SI) defined as differences between baseline and postchallenge values (at PC100SRaw) divided by baseline SD. Median TC of Rrs8, Rrs, Xrs, dRrs/df, and SRaw was 0.21, 0.30, 0.34, 0.41, and 0.42 mg/mL, respectively, indicating a slightly higher sensitivity for FOT. Median SI values of SRaw and Xrs (12.0 and 8.2; difference n.s.) were significantly higher than those of the other parameters. Multiple regression analysis revealed only the absolute change of Xrs (delta Xrs), baseline Rrs and age as significantly (P less than 0.001) correlated with the percentage change of SRaw (delta %SRaw). Best correlation (r = 0.86) with delta %SRaw was found for the function: FOT score = -102.5 X delta Xrs X exp(-0.196 X Rrs + 0.038 X age). Provocative concentrations estimated by this FOT score differed from PC100SRaw by less than one (two) concentration steps in 34 (40) out of 40 children.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1992

Validation of respiratory inductance plethysmography ("Respitrace") for the measurement of tidal breathing parameters in newborns.

INTRODUCTION: The ratio of the time to reach peak (maximum) tidal expiratory flow (Tme) to total expiratory time (Te) is smaller in infants who later develop lower respiratory tract disease. In previous studies infants have been sedated and flow measured using a pneumotachograph with face-mask. These methodological factors are known to affect tidal breathing, and the frequent need for sedation limits the use of the technique to relatively small studies. The aim of this study was to validate uncalibrated respiratory inductance plethysmography (Respitrace) to measure Tme/Te in unsedated newborns. METHODS: Nineteen normal term infants were studied during quiet sleep. Agreement between Tme/Te measured directly using a pneumotachograph and with Respitrace was assessed in 15 infants. Repeatability of the Respitrace technique was assessed in 10 infants. RESULTS: The mean Tme/Te for the 19 infants using Respitrace was 0.46 (S.D. 0.14). The mean difference between Tme/Te obtained using Respitrace and that measured with a pneumotachograph was 0.014; 95% of Respitrace readings were between -0.042 and 0.070 of the pneumotachograph values. The mean difference between repeat Respitrace values was 0.02 with 95% of the second measurements within 0.066 of the first. CONCLUSIONS: These results indicate that Respitrace can be used to determine Tme/Te accurately.

Evaluation Studies as Topic↗
PubMed1995

Functional residual capacity (FRC) measurements by plethysmography and helium dilution in normal infants.

Comparative measurements of functional residual capacity (FRC) made by plethysmography (FRCpleth) and by helium dilution (FRCHe) were obtained on 27 infants and young children without known pulmonary disease (14 males, 13 females; 4 weeks-26 months; mean age 32.2 weeks) while under chloral hydrate sedation. Clinical histories, clinical examinations, and pulmonary functions were normal for all members of the group. FRCpleth, whether measured near end expiration (EE) or near end inspiration (EI), and corrected to mean expiratory levels of at least 3 breathing cycles, was consistently and significantly greater than FRCHe. Comparative values for mean (+/- standard deviation) were FRCpleth EE, 182.0 (+/- 79.7) mL and FRCpleth El, 171.8 (+/- 77.4) mL vs. FRCHe, 154 (+/- 72.2) mL, P < 0.0001 and P < 0.005, respectively. Normalizing values by weight, FRCpleth EE was 23.8 mL/kg (+/- 5.3) vs. FRCHe, 20.2 (+/- 4.7) mL/kg, mean (+/- standard deviation). The difference between FRCpleth and FRCHe, expressed as FRCpleth - FRCHe/FRCpleth x 100, was 9% for occlusions at end inspiration and 16% for occlusions at end expiration. The following equations describe our FRC results in relation to length: In (FRCHe) = 2.74 x ln (length) - 6.53 r2 = 0.781 slope = 2.74 +/- 0.29 SE Y intercept = 6.53 +/- 1.12 SE ln (FRCPleth EI) = 2.69 x ln (length) - 6.21 r2 = 0.752 slope = 2.69 +/- 0.31 SE Y intercept = 6.21 +/- 1.29 SE The difference between FRCpleth and FRCHe was more marked when occlusions were performed at end expiration than at end inspiration.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1995

Respiratory inductive plethysmography in the evaluation of lower airway obstruction during methacholine challenge in infants.

Respiratory inductive plethysmography (RIP) is a simple technique for an objective, noninvasive assessment of thoracoabdominal asynchrony, which in turn is an indirect measure of airway obstruction. We evaluated different indices of asynchrony obtained by RIP before and after methacholine-induced airway obstruction. Bronchial obstruction was elicited by progressive doubling concentrations of methacholine until a > 15% fall in the transcutaneous oxygen tension (PtcO2) had developed. Maximal expiratory flow rates at functional residual capacity (FRC) (VmaxFRC) was obtained by the squeeze technique before and after the challenge. Fifteen infants with a history of wheezing were studied after sedation. Thoracoabdominal movements were recorded with RIP bands placed around either the upper or the lower ribcage (RC) and around the abdomen (AB). An inspiratory asynchrony index (IAI) and an expiratory asynchrony index (EAI) were calculated as determined by the lag of RC relative to AB at start of inspiration and of expiration, respectively. The total time in asynchrony (TTA: the percentage of time in which the RC and the AB signals were in opposite direction) and phi (an angle derived from a Lissajous loop) were also calculated. All subjects responded to the challenge. The median fall in PtcO2 following methacholine challenge was 23.6% and in VmaxFRC was 43%. A large scatter of baseline values was found for all indices with the exception of TTA. There was no correlation between TTA and age, length, or VmaxFRC. The IAI and EAI with the RC band in the upper position were the most sensitive indices, both within subjects (65% of the subjects had a significant change in IAI and 80% in EAI) and for the group as a whole (median values increased for IAI, P = 0.007, and for EAI, P = 0.017). TTA and phi were less sensitive, and a great discrepancy was observed between the two measurements. Poor results were obtained with the RC band in the lower position. No correlations were found between the changes in IAI and EAI, with the RC band around the lower chest and VmaxFRC. We conclude that IAI and EAI, measured with the RC band in the upper position and another band around the abdomen, can detect changes in thoracoabdominal asynchrony in most infants. The usefulness of assessing IAI and EAI in infants with acute lower airway obstruction needs to be determined.

Abdomen↗
PubMed1979

Measurement of forearm blood flow by venous occlusion plethysmography: influence of hand blood flow during sustained and intermittent isometric exercise.

The requirement for using an arterial occlusion cuff at the wrist when measuring forearm blood flows by plethysmography was tested on a total of 8 subjects at rest and during and after sustained and intermittent isometric exercise. The contribution of the venous effluent from the hand to the forearm flow during exercise was challenged by immersing the arm in water at 20, 34, and 40 degrees C. Occlusion of the circulation to the hand reduced the blood flow through the resting forearm at all water temperatures. There was an inverse relationship between the temperature of the water and the proportion in the reduction of forearm blood flow upon inflation of the wrist-cuff, ranging from 45 to 19% at 20 degrees to 40 degrees C, respectively. However, during sustained isometric exercise at 10% of the subjects maximum voluntary contraction (MVC) there was no reduction in the measured forearm flow when an arterial occlusion cuff was inflated aroung the wrist. Similarly, there was no alteration in the blood flow measured 2 s after each of a series of intermittent isometric contractions exerted at 20% or 60% MVC for 2 s whether or not circulation to the hand was occluded nor of the post-exercise hyperemia following 1 min of sustained contraction at 40% MVC. These results indicate that a wrist-cuff is not required for accurate measurement of forearm blood flows during or after isometric exercise.

Forearm↗