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At least 937 records · Page 52Linked to original sources
PubMed1984

Laser-Doppler measurement of skin blood flow: comparison with plethysmography.

We compared laser-Doppler velocimetry with plethysmographically determined changes in skin blood flow (SkBF) in five studies on four men. Increments in SkBF were induced by raising whole-body skin temperature to 39 degrees C for 50-70 min. We found laser-Doppler blood flow (LDF) to correlate well with total forearm blood flow (FBF) within each study (r = 0.94-0.98), but the relationship varied among studies. Thus the slopes for the LDF vs. FBF relationship varied from 40 to 122 mV X ml-1 X 100 ml X min. The value for LDF at zero FBF, extrapolated from the regression relationships, ranged from 246 to 599 mV above the value for LDF set with the probe on a stationary object. The value for LDF when blood flow to the arm was mechanically occluded ranged from 110 to 230 mV. In a second series, we measured the LDF values from six sites on forearms of each of four normothermic men. There was marked regional variation, with 1.8- to 5.7-fold ranges in LDF within a given subject. Values for LDF during occlusion of the forearm were more consistent within and between subjects. Thus LDF appears to provide a good indicator of the response pattern of SkBF from the region of illuminated skin. However, variability in the relationship to total SkBF (probably arising from variation in the number of perfused capillaries in the small volume of tissue) and uncertainties in the value of LDF at zero SkBF make quantitative use difficult.

Adult↗
PubMed1987

Comparison of calibration methods for respiratory inductive plethysmography in infants.

In infants under the age of 6 mo respiratory inductive plethysmograph (RIP)-calculated tidal volumes (VT) were compared with simultaneously measured volumes using a pneumotachograph (PNT) to 1) assess whether using multiple points (MP) along the inspiratory profile of a breath is superior to using only VT when calculating volume-motion (VM) coefficients, 2) verify the assumption of independent contributions of the abdomen and rib cage to VT, which was accomplished by extending the normal RIP model to include a term representing interaction between these two compartments, and 3) investigate whether VM coefficients are sleep-state dependent. Neither use of multiple points nor inclusion of the interacting term improved the performance of the RIP over that observed using a simple two-compartment model with VT measurements. However, VM coefficients obtained during quiet sleep (QS) were not reliable when used during rapid-eye-movement (REM) sleep, suggesting that coefficients obtained during one sleep state may not be applicable to another state where there is a substantial change in the relative abdominal/rib cage contributions to VT.

Humans↗
PubMed1990

Inductance plethysmography measurement of CPAP-induced changes in end-expiratory lung volume.

The respiratory inductance plethysmograph (RIP) has recently gained popularity in both the research and clinical arenas for measuring tidal volume (VT) and changes in functional residual capacity (delta FRC). It is important however, to define the likelihood that individual RIP measurements of VT and delta FRC would be acceptably accurate (+/- 10%) for clinical and investigational purposes in spontaneously breathing individuals on continuous positive airway pressure (CPAP). Additionally, RIP accuracy has not been compared in these regards after calibration by two commonly employed techniques, the least squares (LSQ) and the quantitative diagnostic calibration (QDC) methods. We compared RIP with pneumotachographic (PTH) measurements of delta FRC and VT during spontaneous mouth breathing on 0-10 cmH2O CPAP. Comparisons were made after RIP calibration with both the LSQ (6 subjects) and QDC (7 subjects) methods. Measurements of delta FRC by RIPLSQ and RIPQDC were highly correlated with PTH measurements (r = 0.94 +/- 0.04 and r = 0.98 +/- 0.01 (SE), respectively). However, only an average of 30% of RIPQDC determinations per subject and 31.4% of RIPLSQ determinations per subject were accurate to +/- 10% of PTH values. An average of 55.2% (QDC) and 68.8% (LSQ) of VT determinations per subject were accurate to +/- 10% of PTH values. We conclude that in normal subjects, over a large number of determinations, RIP values for delta FRC and VT at elevated end-expiratory lung volume correlate well with PTH values. However, regardless of whether QDC or LSQ calibration is used, only about one-third of individual RIP determinations of delta FRC and one-half of two-thirds of VT measurements will be sufficiently accurate for clinical and investigational use.

Functional Residual Capacity↗
PubMed1990

Hypopharyngeal and neck cross-sectional changes monitored by inductive plethysmography.

We present a method to assess cross-sectional area (CSA) changes of the extrathoracic airways (EA) by using an inductive plethysmograph (IP) band placed around the upper part of the neck. Measurements of mouth pressure (Pm) (or flow rate, V) and neck CSA changes during respiratory efforts against a high (or infinite) resistance have shown a highly significant relationship between Pm changes (or V changes, respectively), reflecting CSA changes of the EA and CSA changes of the neck. Simultaneous measurements of CSA of the neck (by IP) and of EA (by computerized tomography) during sustained inspiratory and expiratory efforts against a closed airway showed a high correlation between changes in the former and latter structures. Changes in CSA of the neck were larger with positive than negative transmural pressures, in keeping with the known larger compliance of this airway during expiration. We found this method helpful to assess the behavior of the EA during obstructive apnea episodes, hypopneas, and snoring.

Adult↗
PubMed1993

Evaluation of various models for respiratory inductance plethysmography calibration.

We evaluated one nonlinear and two linear models of the ventilatory system while calibrating the respiratory inductance plethysmograph (RIP) against a pneumotachometer. A calibration method involving voluntary varying rib cage and abdominal contributions to tidal volume in a single body position was utilized. The influence on accuracy of the choice of respiratory phase during calibration was assessed. Both tidal and intratidal volumes were evaluated. Ten adults with no history of respiratory disorders went through RIP calibration and validation in the sitting and supine positions. A linear calibration model, relating lung volume changes from the start of inspiration or expiration to rib cage and abdominal excursions from initiation of respiratory motion, had the best accuracy. The choice of respiratory phase for calibration did not affect accuracy. RIP generally underestimated lung volume at the start of inspiration and overestimated lung volume at the end of inspiration. RIP was more accurate in the supine than the sitting position, probably because of limited spine flexion in the supine position.

Adult↗
PubMed1998

Body composition by air-displacement plethysmography by using predicted and measured thoracic gas volumes.

The BOD POD, a new air-displacement plethysmograph for measuring human body composition, utilizes the inverse relationship between pressure and volume (Boyle's law) to measure body volume directly. The quantity of air in the lungs during tidal breathing, the average thoracic gas volume (Vtg), is also measured by the BOD POD by using a standard plethysmographic technique. Alternatively, the BOD POD provides the use of a predicted Vtg (Vtgpred). The validity of using Vtgpred in place of measured Vtg (Vtgmeas) to determine the percentage of body fat (%BF) was evaluated in 50 subjects (36 women, 14 men; ages 18-56 yr). There was no significant difference between Vtgmeas and Vtgpred (mean difference +/- SE, 53.5 +/- 63.3 ml) nor in %BF by using Vtgmeas vs. Vtgpred (0.2 +/- 0.2 %BF). On an individual basis, %BF measured by using Vtgmeas vs. Vtgpred differed within +/-2.0% BF for 82% of the subjects; maximum differences were -2.9 to +3.0% BF. For comparison, data from 24 subjects who had undergone hydrostatic weighing were evaluated for the validity of using predicted vs. measured residual lung volume (VRpred vs. VRmeas, respectively). Differences between VRmeas and VRpred and in %BF calculated by using VRmeas vs. VRpred were significant (187 +/- 46 ml and 1.4 +/- 0.3% BF, respectively; P < 0.001). On an individual basis, %BF determined by using VRmeas vs. VRpred differed within +/-2.0% BF for 46% of the subjects; maximum differences were -2.9 to +3.8% BF. With respect to %BF measured by air displacement, our findings support the use of Vtgpred for group mean comparisons and for purposes such as screening in young to middle-aged individuals. This contrasts with the use of VRpred in hydrostatic weighing, which leads to significant errors in the estimation of %BF. Furthermore, although the use of Vtgpred has some application, determining Vtgmeas is relatively simple in most cases. Therefore, we recommend that the use of Vtgmeas remain as standard experimental and clinical practice.

Adipose Tissue↗
PubMed2001

Flowmetric comparison of respiratory inductance plethysmography and pneumotachography in horses.

Respiratory inductance plethysmographic (RIP) and pneumotachographic (Pn) flows were compared dynamically in horses with bronchoconstriction. On a breath-by-breath basis, RIP was normalized to inspiratory volume from Pn, and peak [peak of subtracted final exhalation waveform (SFE(max))] and selected area [integral of subtracted final waveform during first 25% of exhaled volume (SFE(int))] differences between RIP and Pn flows during early expiration were measured in three settings: 1) healthy horses (n = 8) undergoing histamine bronchoprovocation; 2) horses with naturally occurring lower airway obstruction (AO) (n = 7); and 3) healthy horses (n = 6) given lobeline. HCl to induce hyperpnea. In setting 1, histamine challenge induced a dose-dependent increase in SFE(max) and SFE(int) differences. A test index of airway reactivity (interpolated histamine dose that increased SFE(max) by 35%) closely correlated (r(s) = 0.93, P = 0.001) with a conventional index (histamine dose that induced a 35% decrease in dynamic compliance). In setting 2, in horses with AO, SFE(max) and SFE(int) were markedly elevated, and their absolute values correlated significantly (P < 0.005) with pulmonary resistance and the maximum change in transpulmonary pressure. The effects of bronchodilator treatment on the SFE(max) and SFE(int) were also highly significant (P < 0.0001). In setting 3, hyperpnea, but not tachypnea, caused significant (P < 0.01) increases in SFE(max) but not in SFE(int). In conclusion, dynamic comparisons between RIP and Pn provide a defensible method for quantifying AO during tidal breathing, without the need for invasive instrumentation.

Airway Resistance↗
PubMed2005

Airway resistance due to alveolar gas compression measured by barometric plethysmography in mice.

We developed a method for measuring airway resistance (R(aw)) in mice that does not require a measurement of airway flow. An analysis of R(aw) induced by alveolar gas compression showed the following relationship for an animal breathing spontaneously in a closed box: R(aw) = A(bt)V(b)/[V(t) (V(e) + 0.5V(t))]. Here A(bt) is the area under the box pressure-time curve during inspiration or expiration, V(b) is box volume, V(t) is tidal volume, and V(e) is functional residual capacity (FRC). In anesthetized and conscious unrestrained mice, from experiments with both room temperature box air and body temperature humidified box air, the contributions of gas compression to the box pressure amplitude were 15 and 31% of those due to the temperature-humidity difference between box and alveolar gas. We corrected the measured A(bt) and V(t) for temperature-humidity and gas compression effects, respectively, using a sinusoidal analysis. In anesthetized mice, R(aw) averaged 4.3 cmH(2)O.ml(-1).s, fourfold greater than pulmonary resistance measured by conventional methods. In conscious mice with an assumed FRC equal to that measured in the anesthetized mice, the corrected R(aw) at room temperature averaged 1.9 cmH(2)O.ml(-1).s. In both conscious mice and anesthetized mice, exposure to aerosolized methacholine with room temperature box air significantly increased R(aw) by around eightfold. Here we assumed that in the conscious mice both V(t) and FRC remained constant. In both conscious and anesthetized mice, body temperature humidified box air reduced the methacholine-induced increase in R(aw) observed at room temperature. The method using the increase in A(bt) with bronchoconstriction provides a conservative estimate for the increase in R(aw) in conscious mice.

Airway Resistance↗
PubMedDate not supplied

Assessment of the peripheral microcirculation using computer-assisted venous congestion plethysmography in post-traumatic complex regional pain syndrome type I.

In complex regional pain syndrome type I (CRPS-I), edema of the affected limb is a common finding. Therefore, the changes in macro- and microcirculatory parameters were investigated to elucidate the underlying pathophysiology. Twenty-four patients with post-traumatic CRPS-I and 25 gender- and age-matched healthy subjects were examined by means of an advanced computer-assisted venous congestion strain-gauge plethysmograph. The recording of the volume response of the forearm to a stepwise inflation of an occlusion cuff placed at the upper arm enabled the calculation of the arterial blood flow into the arm (Q(a)), the vascular compliance (C), the peripheral venous pressure (P(v)), the isovolumetric venous pressure (P(vi); = hydrostatic pressure needed to achieve net fluid filtration) and the capillary filtration capacity (CFC)--an index of microvascular permeability. The study revealed no difference in any of the parameters between the right and left hand of healthy subjects. In CRPS-I patients, however Q(a), P(v), P(vi) and CFC were significantly (p < 0.01/0.001) elevated in the affected arm (Q(a) 11.2 +/- 7.0 ml x min(-1) x 100 ml(-1), P(v) 20.2 +/- 8.1 mm Hg, P(vi) 24.7 +/- 4.2 mm Hg, CFC 0.0058 +/- 0.0015 ml x min(-1) x 100 ml(-1) x mm Hg(-1)) compared to the unaffected arm (Q(a) 4.2 +/- 2.4 ml x min(-1) x 100 ml(-1), P(v) 10.0 +/- 5.1 mm Hg, P(vi) 13.2 +/- 3.7 mm Hg, CFC 0.0038 +/- 0.0005 ml x min(-1) x 100 ml(-1) x mm Hg(-1)) and the values obtained in healthy controls (Q(a) 5.1 +/- 1.3 ml x min(-1) x 100 ml(-1), P(v) 10.4 +/- 4.3 mm Hg, P(vi) 15.7 +/- 3.3 mm Hg, CFC 0.0048 +/- 0.0012 ml x min(-1) x 100 ml(-1) x mm Hg(-1)). Whereas the values in the unaffected arm of CRPS-I patients revealed no difference in Q(a), P(v) and P(vi) but a lower CFC (p < 0.01) compared to those from healthy controls. These results suggest profound changes in both macro- and microvascular perfusion in the affected arm of CRPS-I patients. The high CFC contributes to the edema formation, and combined with the elevated P(vi), they are in agreement with the hypothesis of an inflammatory origin of CRPS.

Adult↗