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R Peslin

Publications and source records attributed to R Peslin.

At least 19 recordsLinked to original sources
PubMed1992

Mechanical properties of the upper airway wall in children and their influence on respiratory impedance measurements.

The upper airway wall impedance (Zuaw) may be responsible for a large artifact in the measurement of respiratory system impedance (Zrs) in children. In 17 normal children aged 3.5-13 years Zuaw and Zrs were estimated by varying transrespiratory pressure directly at the mouth (conventional method: Z1) and around the subject's head (head generator method: Z2) from 4 to 32 Hz. Zrs and Zuaw were calculated from Z1 = Zrs.Zuaw/(Zrs+Zuaw) and Z2 = Zrs (1 + Zp/Zuaw), where Zp is the impedance of the pneumotachograph. From the real and imaginary part of Z1, Z2, Zrs, and Zuaw, the corresponding resistance, inertance, compliance and resonant frequency were calculated assuming simple RIC models. No significant difference was found between the mean +/- SE of parameters derived from Zrs (respectively, 6.8 +/- 0.4 cmH2O.L-1.s, 0.034 +/- 0.001 cmH2O.L-1.s2, 10.4 +/- 0.8 m.cmH2O-1, 9.1 +/- 0.3 Hz) and Z2 (6.8 +/- 0.4 cmH2O.L-1.s, 0.038 +/- 0.002 cmH2O.L-1.s2, 10.7 +/- 0.7 ml.cmH2O-1, 8.7 +/- 0.4 Hz). All but the compliance, derived from Z1 were significantly different (P less than 0.01) from those derived from Zrs (5.3 +/- 0.3 cmH2O.L-1.s, 0.008 +/- 0.001 cmH2O.L-1.s2, 11.9 +/- 1.2 ml.cmH2O-1, and 20.3 +/- 1.6 Hz). Respiratory resistance and compliance correlated significantly with height (r = -0.56 and 0.86, respectively), in contrast to upper airway wall resistance (Ruaw) and compliance (Cuaw). Ruaw (8.6 +/- 0.8 cmH2O.L-1.s), Cuaw (1.2 +/- 0.2 m.cmH2O-1), and upper airway wall inertance (0.030 +/- 0.004 cmH2O.L-1.s2) were close to those obtained by direct measurements in adults. The mechanical properties of the upper airway wall are responsible for a significant error in the measurement of Zrs by the conventional method in normal children. Most of the artifact may be corrected for by applying pressure around the child's head.

Biomechanical Phenomena↗
PubMed1992

Evaluation of the multiple linear regression method to monitor respiratory mechanics in ventilated neonates and young children.

A potentially useful method to monitor respiratory mechanics in artificially ventilated patients consists of analyzing the relationship between tracheal pressure (P), lung volume (V), and gas flow (V) by multiple linear regression (MLR) using a suitable model. Contrary to other methods, it does not require any particular flow waveform and, therefore, may be used with any ventilator. This approach was evaluated in three neonates and seven young children admitted into an intensive care unit for respiratory disorders of various etiologies. P and V were measured and digitized at a sampling rate of 40 Hz for periods of 20-48 s. After correction of P for the non-linear resistance of the endotracheal tube, the data were first analyzed with the usual linear monoalveolar model: P = PO + E.V + R.V where E and R are total respiratory elastance and resistance, and PO is the static recoil pressure at end-expiration. A good fit of the model to the data was seen in five of ten children. PO, E, and R were reproducible within cycles, and consistent with the patient's age and condition; the data obtained with two ventilatory modes were highly correlated. In the five instances in which the simple model did not fit the data well, they were reanalyzed with more sophisticated models allowing for mechanical non-homogeneity or for non-linearity of R or E. While several models substantially improved the fit, physiologically meaningful results were only obtained when R was allowed to change with lung volume. We conclude that the MLR method is adequate to monitor respiratory mechanics, even when the usual model is inadequate.

Airway Resistance↗
PubMed1992

Ventilatory dynamics in children and adults during sinusoidal exercise.

The ventilatory response to sinusoidally varying exercise was studied in five adults and seven prepubertal children to determine whether the faster kinetics of ventilation observed in children during abrupt changes in exercise intensity remained more rapid when exercise intensity varied continuously. Each subject exercised on a cycle ergometer first against a constant load and then against a load fluctuating over six different periods ranging from 0.75 to 10 min. The pedal rate was kept constant for all loads. The inspiratory minute ventilation was determined breath-by-breath. Amplitude (A) and phase angle (phi) of the fundamental component and the first harmonics of the ventilatory response were calculated by Fourier analysis for an integer number of waves for each period. From the relationship between A, phi and frequency, dynamic parameters of a first order model with and without delay were compared between adults and children. Firstly we found that the ventilatory time constant was significantly faster in children: 49.7 (SD 9.1) s vs 74.6 (SD 11.1) s (P less than 0.01). Secondly, the change in A and phi with the frequency was not however characteristic of a first order system without delay in most of the subjects (phi greater than 90 degrees for the shorter periods). Thirdly, even when the ventilatory control system was described as a first order model with a positive delay, time constants remained significantly shorter in children: 45.6 (SD 5.7) s vs 67.4 (SD 13) s (P less than 0.01). The ability to increase ventilation faster in children appeared to be a characteristic of the ventilatory control system during exercise independent of the type of drive used.

Adolescent↗
PubMed1992

Changes in inspired gas composition and experimental bronchospasm in the rabbit.

In clinical practice, bronchospasm could be facilitated by hypoxia and by hypercapnia. In this study we assessed the influence of breathing a hypoxic (FIO2 = 0.10) or a hypercapnic (FICO2 = 0.08) gas mixture on the response to nebulized histamine (2% solution for 5 min) in anesthetized, tracheotomized, paralyzed and mechanically ventilated rabbits. Total respiratory resistance (Rrs) and elastance (Ers) were derived by least-square analysis from the relationship between tracheal pressure and flow. Control values of Rrs were larger during hypoxia and hypercapnia than in air while the values of Ers were similar. The absolute change in Rrs after histamine was similar in air and hypoxia, and larger in hypercapnia. The relative change, however, was smaller in hypoxia than in the two other conditions. Ers was also substantially increased by histamine and, contrary to Rrs, remained high 60 min after the aerosol. The results suggest: (1) that both hypoxia and hypercapnia increase airway resistance but do not change tissue properties; (2) that the response to histamine is depressed by hypoxia; (3) that a substantial part of the immediate response, and most, if not all, of the residual response after 60 min is due to changes in lung tissue viscoelastic properties.

Airway Resistance↗
PubMed1992

Respiratory transfer impedance and derived mechanical properties of conscious rats.

A setup is described for measuring the respiratory transfer impedance of conscious rats in the frequency range 16-208 Hz. The rats were placed in a restraining tube in which head and body were separated by means of a dough neck collar. The restraining tube was placed in a body chamber, allowing the application of pseudorandom noise pressure variations to the chest and abdomen. The flow at the airway opening was measured in a small chamber connected to the body chamber. The short-term reproducibility of the transfer impedance was tested by repeated measurements in nine Wistar rats. The mean coefficient of variation for the impedance did not exceed 10%. The impedance data were analyzed using different models of the respiratory system of which a three-coefficient resistance-inertance-compliance model provided the most reliable estimates of respiratory resistance (Rrs) and inertance (Irs). The model response, however, departed systematically from the measured impedance. A nine-coefficient model best described the data. Optimization of this model provided estimates of the respiratory tissue coefficients and upper and lower airway coefficients. Rrs with this model was 13.6 +/- 1.0 (SD) kPa.l-1.s, Irs was 14.5 +/- 1.3 Pa.l-1.s2, and tissue compliance (Cti) was 2.5 +/- 0.5 ml/kPa. The intraindividual coefficient of variation for Rrs and Irs was 11 and 18%, respectively. Because most of the resistance and inertance was located in the airways (85 and 81% of Rrs and Irs, respectively), the partitioning in tissue and upper and lower airway components was rather poor. Our values for Rrs and Irs of conscious rats were much lower and our values for Cti were higher than previously reported values for anesthetized rats.

Airway Resistance↗
PubMed1992

Respiratory mechanics studied by multiple linear regression in unsedated ventilated patients.

Respiratory mechanics during artificial ventilation are commonly studied with methods which require a specific respiratory pattern. An alternative is to analyse the relationship between tracheal pressure (P) and flow (V') by multiple linear regression (MLR) using a suitable model. The value of this approach was evaluated in 12 unsedated patients, mechanically-ventilated for acute respiratory failure, and most with a history of chronic obstructive or restrictive respiratory disease. After correction for the non-linear resistance of the endotracheal tube, the data were analysed with the linear first order model: P = P0 + E.V + R.V' where E and R are total respiratory elastance and resistance, and P0 is the static recoil pressure at end-expiration. After exclusion of the cycles which clearly exhibited muscular activity, a good fit was observed in 25 out of 36 records (relative root-mean-square error less than 10%); the values of E and R were reproducible within cycles, and consistent with the patient's condition and the ventilatory mode. The intrinsic positive end-expiratory pressure (PEEPi), as derived from P0 and the applied PEEP, averaged 1.1 +/- 1.0 hPa. Using more sophisticated models, allowing for mechanical non-homogeneity or non-linearity of R or E, rarely improved the fit and often provided unrealistic data. In several subjects the discrepancy between the data and the first order model was consistent with expiratory flow limitation, which may severely impair the analysis. We conclude that, except in the case of expiratory flow limitation, the method is useful for routine clinical use and better implemented with the simple linear model.

Aged↗
PubMed1992

Within-breath variations of forced oscillation resistance in healthy subjects.

Respiratory resistance (Rrs) was measured by the forced oscillation technique at 10, 20 and 30 Hz in 54 healthy subjects. The sinusoidal pressure oscillations were applied around the head, rather than at the mouth, so as to minimize transmural pressure across extrathoracic airway walls and the corresponding artefact (Peslin et al., J Appl Physiol, 1985, 59, 1790-1795). The flow (V') and volume (V) dependences of Rrs during the respiratory cycle were analysed by least square regression according to: Rrs = K1 + 2.K2.[V']#- K3.V, where K1 and K2 are Rohrer's constants, and where K3 expresses the (negative) volume dependence of Rrs. The analysis was made separately on the inspiratory and expiratory phases. A good fit was usually found between the data and the model, with a root-mean-square error averaging 15% of the mean Rrs at 10 Hz. At all frequencies K2 and K3 were substantially and significantly larger, and K1 slightly lower during expiration than during inspiration. Rrs, K1 and K3 were minimum at 20 Hz, while K2 exhibited a strong positive frequency dependence. The decrease of Rrs from 10 to 20 Hz was entirely explained by the variations of its linear component, and its increase from 20 to 30 Hz was largely due to its flow dependent component. Both the phasic variations and the frequency dependence of the coefficients suggest that the model is purely descriptive and that coefficients K2 and K3 reflect a number of phenomena, including the variations in glottic aperture during the respiratory cycle.

Adult↗
PubMed1979

[Pulmonary function and clinical pattern in homozygous (PiZ) alpha1-antitrypsin deficiency (author's transl)].

A group of 6 males with severe alpha1-antitrypsin deficiency, underwent clinical and pulmonary function evaluation. Findings were compared to those in a group of males with different degrees of airflow obstruction, comparable ages and tobacco consumption, but with normal serum levels of alpha1-antitrypsin. The deficient group was characterized by: (1) a relatively early appearance of symptoms; (2) disturbed lung scans, mostly in the basal zones; (3) radiological evidence, in most cases, of pulmonary emphysema with, in particular, bullae in the lower lung zones; (4) hypoxemia without hypercapnia and a decreased TCO/VA, and (5) a more or less severe reduction of maximal expiratory flows largely, but not exclusively due to a decrease in lung elastic recoil. Clinical and functional parameters did not permit a clear distinction between the deficient and non-deficient groups.

Adult↗
PubMed1979

Comparison of various methods for reading maximal expiratory flow-volume curves.

To determine the best procedure for reading maximal expiratory flow-volume curves 2 sets of 5 curves were obtained one hour apart in 89 subjects and processed digitally according to 8 different methods. Four indices were considered: the forced expiratory flows at 25, 50, and 75 per cent of the forced vital capacity, and the maximal mid-expiratory flow. When selecting the curve yielding the largest forced vital capacity or the largest sum of forced vital capacity and forced expiratory volume in 1 sec, flow values were significantly lower (P less than 0.001) and were often less reproducible than those obtained with most of the other methods. Computing the mean of the indices among the curves with the 2 largest forced vital capacities also provided comparatively low values, but with with better reproducibility. In contrast, maximal flows were probably overestimated by using the highest values among the curves having forced vital capacity or a surface area within 5 per cent of the largest, or when reading the indices on a composite curve obtained by superimposing individual breaths at residual volume. More reproducible and, probably, unbiased data may be drawn from the composite curves obtained by superimposing the breaths either at total lung capacity or on the descending limb.

Adult↗
PubMed1978

[Von Recklinghausen's disease: functional pulmonary changes. 2 case reports].

We report two cases of patients with Von Recklinghausen disease. They exhibited typical cutaneous and diffuse intrapulmonary lesions accompanied by effort dyspnea. Multiple radiological abnormalities were noticed and the pictures showed nodular and interstitial lesions as well as emphysematous areas. Pulmonary function tests revealed more or less marked hypoxemia without hypercapnia, and decreased maximal expiratory flows due, at least in part, to a loss of elastic recoil.

Adult↗
PubMed1978

The respiratory response to inhaled carbon dioxide in man after 3 hours exposure to 3% carbon dioxide.

1. The respiratory response to inhaled 3% and 6% CO2 was measured in 10 normal subjects after a 3 h acclimatization period to 3% CO2 in an environmental chamber. Control studies were carried out after a 3 h period of breathing air in the chamber. 2. At the end of the acclimatization period studies were carried out during 20 min periods breathing 3% CO2, 6% CO2 and air. 3. At 2-min intervals during the studies measurements were made of tidal volume (Vt), breathing frequency (fR), minute ventilation (Ve), viscous pulmonary rate of work (Wp) and total viscous rate of work across the lungs and apparatus (Wt). Blood gas tensions were measured at the end of this period. 4. After acclimatization to 3% CO2 there was a significant shift in the response curves Ve/Pa,CO2 and Wt/Pa,CO2 such that subjects showed higher Pa,CO2 values for given values of Ve or Wt. There was no significant change in the slope of the response curves. 5. No correlation was found between the slope of the response curve after the control period breathing air and the degree of shift of the response curve. 6. There was no difference in respiratory pattern or in pulmonary resistance. 7. Similar results were found in two subjects studied after 24 h acclimatization to 3% CO2 but one subject also showed a significant change in the slope of the Ve/Pa,CO2 curve.

Acclimatization↗
PubMed1978

Breath sounds in the clinical assessment of airflow obstruction.

In a group of 34 inpatients showing varying degrees of airflow obstruction we studied the relationship between breath sound intensity (BSI) and abnormalities of lung function. The BSI was evaluated by chest auscultation to provide a score, in a manner similar to that described by Pardee et al. (1976), and was found to correlate closely with indices of airflow obstruction of their logarithms such as specific conductance (r = 0.759), maximal expiratory flow at 50% of vital capacity (r = 0.790), forced expiratory volume in one second (r = 0.768), and forced expiratory volume to vital capacity ratio (r = 0.860). Correlations with lung volumes, although statistically significant, were weaker. Multiple correlation studies showed that BSI score correlated independently with indices of both airflow obstruction and lung distension. In our experience, BSI score can be useful not only in the detection but also the quantification of airflow obstruction, although its predictive power is impaired in subjects with associated restrictive disorders. It can also fail to detect mild, pure airflow obstruction.

Adult↗
PubMed1977

[Pulmonary mechanics and alveolar exchanges in the elderly with apparently healthy lungs. Preliminary study].

A group of ten elderly subjects who were apparently normal from the cardiac and pulmonary points of view, were selected on criteria of history, clinical findings, radiological and E.C.G. findings, with a view to a study of respiratory function based on two aspects: alveolar exchanges were assessed by measurement of the ductance of carbon monoxide and the elastic properties of the lung together with bronchial permeability. Although alveolar exchanges are little modified, one may note some pulmonary distension, especially in the smokers, together with a reduction in elasticity. The changes in bronchial permeability which affect the peripheral and central airways, are mainly found in smokers. One may determine the respective roles of extrinsic and intrinsic bronchial obstruction in these abnormalities. One may thus consider that, from the pulmonary point of view, the elderly patient faced with a surgical operation should be considered a high risk for respiratory decompensation, especially if he is, or has been, a smoker.

Aged↗
PubMed1976

Modeling of the relationship between volume variations at the mouth and chest.

A model was developed to interpret the difference between volume variations at the mouth and at the chest observed by body plethysmography during inspiration in normal subjects breathing ambient air. The mechanical phenomena were characterized, as usual, by a time constant alpha, the product of airway resistance and alveolar gas compressibility. In contrast to other models, the change in temperature and water vapor pressure of the inspired gas was not considered to be instantaneous but rather a first-order process characterized by a thermal time constant tau. Experimental curves obtained in eight subjects were analyzed by use of parameter estimation techniques. The values of alpha were in agreement with those obtained by conventional plethysmography and tau averaged 63+/-24 ms. The results of additional experiments devised to test the physical meaning of the coefficients and the influence of neglected factors support the validity of the model. It was shown that tau cannot be neglected when breathing air at room temperature.

Humans↗
PubMed1975

Frequency response of the chest: modeling and parameter estimation.

The frequency response of the respiratory system was studied in the range from 3 to 70 Hz in 15 normal subjects by applying sinusoidal pressure variations around the chest and measuring gas flow at the mouth. The observed input-output relationships were systematically compared to those predicted on the basis of linear differential equations of increasing order. From 3 to 20 Hz the behavior of the system was best described by a 3rd-order equation, and from 3 to 50 Hz by a 4th-order one. A mechanistic model of the 4th order, featuring tissue compliance (Ct), resistance (Rt) and inertance (It), alveolar gas compressibility (Cg) and airway resistance (Raw), and inertance (Iaw) was developed. Using that model, the following mean values were found: Ct = 2.08-10(-2)1-hPa-1 (1 hPa congruent to 1 cm of water); Rt = 1.10-hPa-1(-1)-s; It = 0.21-10(-2)hPa-1(-1)-s2; Raw = 1.35-hPa-1(-1)-s; Iaw = 2.55-10(-2)hPa-1(-1)-s2. Additional experiments devised to validate the model were reasonably successful, suggesting that the physical meaning attributed to the coefficients was correct. The validity of the assumptions and the physiological meaning of the coefficients are discussed.

Airway Resistance↗
PubMedDate not supplied

[A diagram to analyse airways patency abnormalities (author's transl)].

The factors contributing to airflow obstruction in chronic respiratory diseases are frequently investigated by measuring an index of airways patency : 1) at various lung volumes, which permits to detect and quantify the obstruction, 2) at different static recoil pressures (Pst) to recognize abnormalities not related to a loss of elastic recoil. A diagram has been developed which facilitates the analysis and permits a more quantitative evaluation of intrinsic and extrinsic factors : the index of airways patency (I) is plotted simultaneously against Pst and against lung volume (expressed in % of predicted TLC), the two abscissae being scaled in such a way that the normal ranges are coincident for the two curves. Then, the distance from the I(Pst) curve to the normal range may be used to estimate the abnormalities due to intrinsic factors, and the distance between the two curves to evaluate extrinsic obstruction. Taking maximum expiratory flows as the index of airways patency, examples are shown to illustrate the use of the diagram.

Airway Obstruction↗