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Biomedical subjects

R L Pimmel

Publications and source records attributed to R L Pimmel.

At least 19 recordsLinked to original sources
PubMed1979

Forced oscillatory respiratory parameters following papain exposure in dogs.

Respiratory mechanics were studied in nine intubated dogs before and after exposure to aerosolized papain under conditions known to produce emphysemalike lesions. Forced oscillatory resistance (RFO), compliance (CFO), and inertance (IFO) were computed from impedance data obtained at transrespiratory pressures of -10, 0 (FRC), +10, and +20 cmHWO. Dynamic compliance during tidal breathing (CTB) was also measured at FRC. After papain exposure CTB and CFO increased by 25% (P less than 0.05) at FRC and at +10 cmH2O. There were no consistent changes in RFO or IFO at FRC. However, RFO showed a greater dependency on transrespiratory pressure, which suggests that the elastic properties of airways may also have been affected by papain. Measurements made in open-chested papain-exposed animals showed that about 17% of total RFO and 20% of total elastance were attributable to the chest wall. Forced oscillatory impedance data are sensitive to experimental changes in lung mechanics and provide useful estimates of standard respiratory parameters.

Airway Resistance↗
PubMed1979

Respiratory impedance and derived parameters in young children by forced random noise.

The frequency dependence of total respiratory impedance during spontaneous breathing was measured repeatedly in 16 children (3--5 yr old) over a 3-mo period using forced random noise and spectral analysis. Total respiratory resistance, compliance, and inertance, which were calculated fromthe impedance data using regression analysis with a second-order model, had overall mean values +/- SD of 5.61 +/- 0.49 cmH2O.l-1.s, 403 +/- 1.04 ml.cmH2O-1, and 0.0120 +/- 0.0024 cmH2O.l-1.s2, respectively. Linear regression analysis showed that resistance and compliance correlated with either height or forced vital capacity with r values in the range 0.77--0.89. Analysis of measurement variability suggested that resistance measurements had, on the average, a coefficient of variation of 15%; corresponding values for compliance and inertance measurements were 25%.

Airway Resistance↗
PubMed1979

Fractionating respiratory resistance in young children.

Total respiratory resistance (Rrs) and the fraction of this resistance located peripherally, (Fp) were measured in a group of children (3--5 yr old). The technique used forced random noise to characterize the frequency dependence of effective resistance and an algorithm to compute Rrs and Fp from these data. The overall mean value +/- SD for Fp was 0.534 +/- 0.070; the mean value of 0.464 for the six children near 5 yr of age was significantly different (P less than 0.001) from the mean value of 0.576 found in the younger children. The overall mean value +/- SD for Rrs was 16.9 +/- 5.8 cmH2O.l-1.s; individual values appeared to be correlated with height. These results agree with previous reports indicating that children have a larger fraction of respiratory resistance in the periphery than do adults.

Airway Resistance↗
PubMed1979

Detection of respiratory mechanical dysfunction by forced random noise impedance parameters.

Respiratory mechanical parameters were computed from forced random noise impedance data in normal adults (group 1), asymptomatic smokers (group 2), and patients with obstructive pulmonary disease (group 3). Mean values for all derived parameters were significantly different (p less than 0.025) for group 3. Mean values of resonant frequency, the ratio of low-frequency (5 to 9 Hz) resistance to high-frequency resistance (15 to 19 Hz), and conductance normalized by height, were significantly different (p less than 0.05) between groups 1 and 2. This approach appears to yield respiratory mechanical parameters that are sensitive to mechanical alterations induced by early pulmonary disease. The rapid, noninvasive, and effort-independent nature of this approach make it especially useful for epidemiologic studies and for studies of "noncooperative" subjects.

Forced Expiratory Volume↗
PubMed1979

Forced expiratory spirometric parameters derived by feature-extraction techniques.

Spirometric data from 200 patients seen in the pulmonary function laboratory were analyzed retrospectively. Using standard criteria, the spirometric patterns of the subjects were classified as indeterminate, normal, restrictive, or obstructive; obstruction was further classified as mild, moderate, severe, or very severe. A formal feature-extraction technique was used to define 2 new parameters. These were linear combinations of the 5 standard spirometric parameters and explained 94% of the variation in the original parameters. The derived parameters provided better separation of the various classes than the combination of the normalized forced vital capacity and the ratio of the forced expiratory volume in 1 s to the forced vital capacity.

Forced Expiratory Flow Rates↗
PubMed1979

The effects of early pneumonectomy on the remaining pulmonary parenchyma.

To determine the age-related response of the remaining pulmonary parenchyma to lung resection, a matched set of 24 purebred beagle dogs underwent pneumonectomy at 6 to 10 weeks of age (group I) or at 1 year of age (group II). Eight unoperated adult beagles served as controls (group III). One year after pneumonectomy, pulmonary hemodynamics in group I were the same as those in older animals shortly after pneumonectomy and in normal control animals. Functional residual capacity, total lung capacity, single breath diffusing capacity for carbon monoxide, and static lung compliance were measured in all three groups while anesthetized and intubated. Lung volumes and diffusion capacity for carbon monoxide in group I did not differ significantly from those of control animals. Group I animals did have a lower lung compliance than the control group, but significantly greater than the group II adult pneumonectomy dogs. The adult pneumonectomy dogs (group II) had significantly lower values for lung volumes, diffusion capacity, and compliance when compared to the control group. Arterial blood gases were not significantly different among the groups. It is concluded that beagles undergoing early pneumonectomy have an increase of alveoli beyond the normal complement in the remaining lung with concomitant remodeling of the pulmonary capillary bed resulting in normal lung volumes, diffusing capacity, and gas exchange.

Age Factors↗
PubMed1978

Estimating central and peripheral respiratory resistance.

An analytic approach for fractionating total respiratory resistance into central (Rc) and peripheral (Rp) components is presented. In the analysis, linear regression equations relating the logarithm of the measured total resistance to the logarithm of frequency are derived for data spanning the frequency range 1-16 Hz. The computed slope and intercept are used to obtain estimates of the fraction of the resistance in the periphery (Fp) and of Rp and Rc. Data from anesthetized, closed-chested dogs in a control state and with an external resistor (1.37 cmH2O.1-1.s) were used to test the approach. Mean values +/- SE's for control data were: Fp = 0.400 +/- 0.039, Rp = 1.37 +/- 0.16 cm H2O.1-1.s, and Rc = 1.98 +/- 0.10 cmH2O.1-1.s. Mean values of Rp obtained with and without added resistance were not significantly different (P less than 0.1). The increase in the mean values of Rc represented 85% of the value of the added resistance but was significantly different from the known value of the external resistance (P less than 0.05). These data suggest that it may be possible to fractionate total respiratory resistance into central and peripheral components using the frequency dependence of forced oscillatory resistance.

Airway Resistance↗
PubMed1978

Spirometric changes in normal children with upper respiratory infections.

Recent evidence that certain uncomplicated upper respiratory infections induce pulmonary function abnormalities in adults prompted a prospective study in children, in whom such infections occur more frequently. In a longitudinal study, 55 children 2.5 to 11 years of age were observed for a mean duration of 2 years. Spirometry and lung volume studies were obtained routinely every 3 months, during each upper respiratory infection, and 4 weeks after illnes, providing data for 617 "well" and 237 "illness" observations. After grouping of data by sex and age (less than 84 of greater than 84 months), each spirometric parameter was analyzed using linear regression with individual identification, height, and clinical status (normal versus upper respiratory illness) as independent variables. Adjusted mean values of forced vital capacity, 1-sec forced expiratory volume, peak expiratory flow, maximal mid-expiratory flow, and expiratory flow at 50 per cent of the forced vital capacity all decreased during upper respiratory illness. The data suggest that lower respiratory tract involvement without signs or symptoms of lower airway or alveolar disease occurs with upper respiratory illnesses of varied etiologic origin in childhood.

Body Height↗
PubMed1977

Respiratory parameter estimation using forced oscillatory impedance data.

The frequency dependency of the magnitude and phase angle of total respiratory impedance was measured in apneic dogs at functional residual capacity during forced oscillation by a special electronics unit. Regression analysis of these data yielded estimates of total respiratory resistance (RFO), inertance (IFO), and compliance (CFO). After correcting for the effects of the endotracheal tube, mean control values (+/-SE) of RFO, IFO, and CFO for the clinically normal dogs were 1.30+/-0.10 cmH2O-1-1-s, 0.0114+/-0.0022 cmH2O-1-1-s2, and 0.0306+/-0.0009 1-cm H2O-1, respectively. Estimates obtained with added resistance, a less dense gas, and abdominal weighting were consistent with predicted effects. In four dogs with mild respiratory symptoms, mean RFO was significantly elevated with no change in IFO or CFO. Independent measurements of resistance and compliance during tidal ventilation correlated well with RFO (r=0.87) and CFO (r=0.80), but RFO and CFO were, on the average, 71% of the tidal breathing values. Thus, the method provides precise estimates of RFO, IFO, and CFO, and allows detection of small changes in these parameters.

Airway Resistance↗
PubMed1977

Estimating Va/Q distributions from inert gas data with an enforced smoothing algorithm.

The accuracy of a noniterative smoothing algorithm without a nonnegativity constraint for estimating continuous Va/Q distributions from inert gas retentions was evaluated. Simulated retention measurements computed from three assumed distributions were processed by the algorithm. Original and recovered distributions were compared with the root-mean-square (rms) difference. With noise-free retentions, the rms differences were minimum with zeta = 0 (no smoothing). With simulated 3% noise, the minima occurred when 0.01 less than zeta less than 0.10. Seven trials with independent simulated errors showed a large variation in the recovered distribution and the rms difference. All recovered distributions were qualitatively different from the originals especially at low and high Va/Q values. Negative fractional flows existed in all distributions that were not grossly different from the originals. We believe that this method which did not include a nonnegativity constraint, is inappropriate for processing inert gas retentions.

Humans↗
PubMed1976

Effects of anesthesia level and stimulus characteristic on the amplitude and latency of the somatosensory evoked response in monkeys.

The effect on the somatosensory evoked response (SER) of the level of anesthesia, and the effect of the site, intensity, duration, and frequency of the stimulus on the amplitude and latency of various components of the SER were studied in 8 Rhesus monkeys. Peroneal nerve stimulation produced similar patterns over both sides of the head, with a slightly larger amplitude over the contralateral cortex. With ulnar nerve stimulation, significantly different patterns were observed over the contralateral and ipsilateral cortex; however, the former still had a slightly larger amplitude. The latency of the various components in the SER's was not influenced by the level of anesthesia or by the intensity, duration, or frequency of the stimulus. As the level of anesthesia decreased, there was a general increase in amplitude of the SER's with peroneal nerve stimulation and no consistent change with ulnar nerve stimulation. The amplitudes of the SER increased with the increase in stimulus intensity or duration, and with a decrease in stimulus frequency.

Afferent Pathways↗