Biomedical subjects

F Marchal

Publications and source records attributed to F Marchal.

At least 109 records · Page 6Linked to original sources

PubMed1993

Effects of dopamine on the carotid chemosensory response to hypoxia in newborn kittens.

In a previous study, it has been shown that bolus injections of dopamine could either stimulate or inhibit the carotid chemosensory discharge in the kitten (Marchal et al., 1992a). To further characterize dopaminergic mechanisms in the carotid body during development, the effects of a continuous infusion of dopamine on carotid chemosensory activity in air, hypoxia (8% O2 in N2) and hyperoxia (100% O2) were studied in ten anesthetized, paralyzed and artificially ventilated kittens, aged 1 to 21 days and in three adult cats. One carotid sinus nerve was prepared for recording the activity of a single or a few chemosensory afferents. In the kittens, the immediate effect of dopamine at the onset of infusion (10 micrograms/kg/min) was an inhibition of the discharge in five kittens, a progressive excitation in four and no change in one. Four minutes after the onset of dopamine infusion, there was a significant increase in chemosensory activity both in room air (from 4.5 +/- 0.8 impulse/sec to 8.8 +/- 1.4 impulse/sec, mean +/- SEM, P < 0.05) and in hypoxia (from 24.6 +/- 3.7 impulse/sec to 33.4 +/- 5.3 impulse/sec, P < 0.05) but not in hyperoxia (0.5 +/- 0.2 impulse/sec vs 0.7 +/- 0.3 impulse/sec). The adult cats received four successive dopamine infusions at the rate of 2.5, 5, 7.5 and 10 micrograms/kg/min, in an attempt to establish a dose-response relationship. The effects of dopamine infusions were consistent within, but variable between, cats. The onset of dopamine infusion was associated with an inhibition of the discharge in two cats, at all infusion rates. In one of them, chemosensory activity returned quickly to control and the response to hypoxia was enhanced. In the other cat, the inhibition of the discharge persisted for the duration of the infusion, and the response to hypoxia was inhibited. In the third cat, dopamine had no effect on the chemosensory discharge. The patterns of chemosensory responses evoked by dopamine are qualitatively similar in kittens and cats, but the excitatory type of response appear to be more readily elicited in the kitten.

Action Potentials↗

PubMed1993

Effects of doxapram on carotid chemoreceptor activity in newborn kittens.

Doxapram is a respiratory stimulant which acts on peripheral chemoreceptors and central respiratory neurons in a dose-dependent fashion in the adult cat. In the newborn, the mechanisms of action of doxapram are still unclear. To evaluate the effects of doxapram on the carotid chemosensory discharge and its relationship with dopaminergic mechanisms in the carotid body, two groups of kittens less than 13 days old, anesthetized, artificially ventilated and paralyzed, were prepared for the recording of a single or a few chemosensory afferents of the carotid sinus nerve. The chemosensory activity was recorded under five conditions of inspired gas mixtures (21 and 8% O2 in N2, 100% O2, 5 and 10% CO2 in O2). Group 1 (n = 9) received only doxapram and group 2 (n = 8) was pretreated with haloperidol (1 mg/kg), a dopamine D2-receptor blocker, before receiving doxapram. Doxapram significantly stimulated the discharge rate of the carotid chemoafferents under all conditions of inspired gas. The chemosensory discharge was increased by haloperidol, and was raised further after doxapram by an amount similar to group 1. For instance, in normoxia, the activity increased from 2.9 +/- 0.4 to 7.5 +/- 0.9 impulse/s (mean +/- SEM, p < 0.01) in group 1 and from 3.8 +/- 0.6 to 9.1 +/- 1.0 impulse/s (p < 0.01) in group 2. These results indicate that the mechanisms of response of carotid chemoreceptor to doxapram are developed in the newborn kitten and doxapram acts independent of the dopaminergic mechanisms in the carotid body.

Animals↗

PubMed1993

Traumatic paramediastinal air cyst: report of two cases and review of the literature.

Two cases of traumatic paramediastinal air cyst are presented with a review of the literature. This rare condition affects young people and usually occurs on the left side of the chest. Its course is spontaneously benign. Although they are usually easily diagnosed on chest roentgenograms, these cysts may sometimes be difficult to differentiate from other more serious traumatic lesions. Computed tomography (or a contrast swallow roentgenogram in some instances) can elucidate doubtful cases.

Adult↗

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

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

Carotid chemoreceptor response to natural stimuli in the newborn kitten.

The activities of carotid chemoreceptors at three levels of inspired PO2 (55, 145 and 690 Torr) and at two levels of inspired PCO2 (35 and 70 Torr in O2) were studied in 28 anesthetized, mechanically ventilated kittens aged 0-17 days. A biphasic response to hypoxia was found in 46% of them: the chemosensory activity increased to a peak within 30 sec after the initial response to hypoxia and thereafter declined slowly to a stable value. The steady-state single-fiber chemosensory activity at an inspired PO2 of 55 Torr was significantly lower in kittens less than 10 days old (mean +/- SE: 5.8 +/- 0.6 impulses.sec-1) than in the older ones (8.8 +/- 1.3 impulses.sec-1, P less than 0.03). The response curves to arterial PO2 were hyperbolic in both groups but the curve for the younger kittens was displaced to the left of the curve for the older ones. The response to hypercapnia was a progressive increase in chemosensory activity with little evidence of rapid or slow adaptation. The response to hypercapnia was significantly stronger in the older kittens than in the young ones. It is concluded that, in the kitten, the carotid chemoreceptor response to hypoxia may be biphasic. The responses to hypoxia and hypercapnia are already developed but are weak at birth and continue to develop further during the first weeks of postnatal life.

Animals↗

PubMed1992

Dual responses of carotid chemosensory afferents to dopamine in the newborn kitten.

The effects of dopamine and of dopamine D2 receptor blocker haloperidol on the activity of carotid chemoreceptors were studied in 24 anesthetized, paralyzed and artificially ventilated newborn kittens aged 0-17 days. Single or few fiber preparations of chemoreceptors were made from one carotid sinus nerve. The responses of the chemosensory afferents to intravenous injections of dopamine (5-50 micrograms.kg-1) were studied in kittens breathing air and 8% O2 in N2. The effects of haloperidol on the chemosensory activity in air or 100% O2 and on the chemosensory response to hypoxia were studied. Dopamine inhibited the chemosensory discharge in 25/44 studies in normoxia. Of the 9 studies performed in hypoxia, dopamine was excitatory in 5 or had no effect in 4 (P < 0.05 vs normoxia). Inhibition of the chemosensory discharge was observed in 24/37 studies performed in kittens aged more than 3 days and was predominantly excitatory in 6/7 studies in kittens aged 0-3 days (P < 0.01). One minute after haloperidol, the chemosensory discharge had increased significantly in all experiments. The biphasic pattern of chemosensory response to hypoxia (Marchal et al., Respir. Physiol. 87: 183-193, 1992) was not changed by haloperidol. The steady-state chemosensory activity was significantly increased after haloperidol, respectively from 3.9 +/- 0.7 impulses.sec-1 to 9.8 +/- 1.2 impulses.sec-1 in air, and from 13.1 +/- 1.4 impulses.sec-1 to 17.8 +/- 2.4 impulses.sec-1 in hypoxia (mean +/- SEM, P < 0.03). It is concluded that the dopaminergic mechanisms are active in the carotid body of the kitten, and the observed responses to dopamine and haloperidol are qualitatively similar to those reported in the adult cat.

Action Potentials↗

PubMed1991

Viscoelastic properties of rabbit lung during growth.

Viscoelasticity of air-filled isolated lungs of 1-120 day old rabbits was studied at a mean transpulmonary pressure (P1) of 0.65 kPa by measuring: (1) their stress relaxation (SR) following step volume changes (delta V) corresponding to 5% of the vital capacity; (2) their resistance (R1) and elastance (E1) during sinusoidal cycling at 11 frequencies (f) ranging from 0.01 to 0.65 Hz. SR data were analyzed by least-square regression using Hildebrandt's logarithmic model (Hildebrandt, J. (1970) J. Appl. Physiol. 28: 365-372): delta P1/delta V = A - B.log(t) where A is an index of elastance, and B/A is a measure of viscoelasticity. Coefficients A and B were also obtained from R1 and E1 according to: R1 = B/9.2 f and E1 = A + 0.25 B + B.log(2 pi f). Elastance corrected for lung weight increased by 40% between day 1 and days 3-7, and decreased thereafter to reach 30% of its initial value in 120 day old rabbits. B/A ratios also demonstrated an initial rise, followed by a progressive decrease. Values of B/A computed from R1 and E1 were similar to those derived from SR data in 1 day old rabbits, but were 20-30% larger in older animals, which indicates the presence of an additional rate-independent dissipation during flow. Total internal dissipation during cycling varied little with frequency; it was largest in 3-7 day old animals where it represented 20% of the stored elastic energy.

Animals↗

PubMed1991

Respiratory mechanics in spontaneously breathing term and preterm neonates.

The compliance (Crs), resistance (Rrs) and passive time constant (tau rs) of the respiratory system were determined by the single-breath method (sb) in 24 healthy term and preterm newborns. In 22 of them, Crssb was compared to the slope of the pressure-volume curve determined by the multiple occlusion technique (mo), which is not dependent on the assumption of a linear flow-volume relationship. Crssb and Rrs correlated significantly with body weight (kg): Crssb = 0.56 x kg + 1.22 (r = 0.67); Rrs = -20.1 x kg + 134.6 (r = -0.68). No difference in Crs and Rrs between prone and supine positions was found. tau rs was not significantly different between premature (0.21 +/- 0.06 s) and full-term infants (0.21 +/- 0.05 s). Crssb was significantly higher than Crsmo in premature babies (2.27 +/- 0.41 ml.cm H2O-1 vs. 1.98 +/- 0.47 ml.cm H2O-1. This difference may be explained by a continuous braking of expiratory airflow after release of the occlusion, or more likely, by a difference in the lung volume at which Crssb and Crsmo are measured. However, the difference between Crssb and Crsmo (approximately 15%) is in the same range as the intrasubject variability, and is meaningless compared to the alterations of respiratory mechanics observed during neonatal ventilatory disorders. Therefore, the single-breath method appears to be a suitable and noninvasive method to measure respiratory mechanics in nonintubated prematures.

Airway Resistance↗

PubMed1991

Thoracic gas volume at functional residual capacity measured with an integrated-flow plethysmograph in infants and young children.

Thoracic gas volume (TGV) was measured with an integrated flow plethysmograph in 15 infants aged 2-34 months. End-expiratory (TGVe) and end-inspiratory (TGVi) airway occlusions were compared, after correction of TGV for the occluded volume above functional residual capacity (FRC). The relationship between pressure at the airway opening (Pao) and volume displaced from the box during airway occlusion (Vg) was studied numerically by: 1) an algorithm including a correction for the drift of Vg and linear regression analysis (LR); and 2) Fourier analysis of the signals (FFT). TGVe was significantly higher than TGVi (256 vs 237 ml, 20.4 (square root of residual variance; p less than 0.002). The correlation coefficient of the Pao-Vg relationship was slightly but significantly higher for TGVi than for TGVe: 0.9968 (0.9937-0.9995) vs 0.9947 (0.9840-0.9990) (means and range). No difference was observed between LR and FFT, although the intra-individual coefficient of variation was lower for LR than FFT: 5.2% (1.6-11.3) vs 7.9% (1.9-21.0) (means and range). Model simulations suggested that the difference between TGVe and TGVi could be mainly attributed to gas compression in the instrumental deadspace and upper airway wall motion and/or to uneven distribution of alveolar and pleural pressure associated with chest wall distortion.

Airway Resistance↗

PubMed1989

Measurement of ventilatory mechanical impedance in infants using a head pressure generator.

Two methods of measuring ventilatory mechanical impedance (Z) by forced oscillations between 6 and 20 Hz were compared in 24 infants aged 2 to 49 months: 1) the application of pressure oscillations at the airway opening (Z1); and 2) the application of pressure oscillations around the head (Z2). The latter has been recently proposed to minimize the influence of compliant upper airway walls (Peslin et al., J Appl Physiol. 1985, 59:1790-1795). Ventilatory resistance and compliance (Rsb, Csb) were also obtained with the single breath method. The real part of Z1 (R1) was markedly lower than that of the corresponding Z2 (R2), at any frequency. R1 exhibited a systematic negative frequency dependence, in contrast with R2. At any frequency, the slope of the regression equation on Rsb was closer to unity for R2 than for R1. The imaginary part of Z1 (X1) was negative over the whole frequency interval, and negative values of inertance were derived from X1. X2 was negative at low and positive at high frequencies. Resonant frequency (mean +/- SD = 10.5 +/- 3.5 Hz) was always reached with Z2 and correlated negatively with body weight (r = -0.61). Inertance estimated from X2 was positive and correlated negatively with body height (r = -0.66). The compliance derived from Z1 (C1 = 3.35 +/- 2.32 10(-3) L.cm H2O-1) was not significantly different from that derived from Z2 (C2 = 2.99 +/- 2.02 10(-3) L.cm H2O-1). The marked difference observed between Z1 and Z2 is related to the importance of the upper airway shunt and may be explained by inaccuracies of both methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Evaluation of the effect of heparin and tetracycline on the cohesion of the dermal-epidermal junction.

In an attempt to demonstrate the effect of tetracycline or heparin therapy on the dermo-epidermal junction, the suction blister time was measured at the beginning and at the end of the study in 18 female Sprague-Dawley hairless rats, using the suction blister method. Suction blister time was defined as the time taken for the first sign of a vesicle to appear in the hole in the diaphragm of a suction chamber. 200 IU heparinate calcium was administered daily for 6 days in 6 rats. Six other rats received 27.5 mg tetracycline chlorhydrate daily for 6 days. The others did not receive any drug. Significant statistical differences in suction blister time before and after administration of the drugs were found in the heparin group (p less than 0.05), and in the tetracycline group (p less than 0.05), compared with the control group. Heparin and tetracycline were found to increase suction blister time significantly. These results suggest an increased cohesion in the dermo-epidermal junction due to heparin and tetracycline.

Animals↗

PubMed1988

Mechanics of the ventilatory system in sedated infants: forced oscillations versus single-breath method.

The real--Re(Z)--and imaginary--Im(Z)--parts of the ventilatory system impedance were measured between 6 and 30 Hz in 18 normal infants and in 19 with airway obstruction. The intercept (R0) and slope (S) of the Re(Z)-frequency function, as well as inertance (I) and compliance (C) estimated from Im(Z), were compared with ventilatory system resistance (Rrs) and compliance (Crs) (single-breath method). R0 correlated significantly with Rrs (r = 0.86), although the slope of the regression equation was significantly lower than 1 (P less than 0.01). Negative frequency dependence of Re(Z) was observed in all subjects and a significant correlation was found between S and Rrs (r = -0.80). "Inertance" was negative in 20 subjects and correlated negatively with Rrs (r = -0.61). C correlated with Crs (r = 0.64) and with 1/Rrs (r = 0.85). The ratio of C to Crs (mean +/- SD = 0.168 +/- 0.082) also correlated with 1/Rrs (r = 0.51). The main characteristics of the total impedance/frequency function could be simulated with a model featuring the upper airway wall (Zuaw) in parallel with the ventilatory system (Zrs). It is suggested that the differential change in Zuaw and Zrs with growth accounts for the marked frequency dependence of Re(Z) as well as the inaccurate estimation of both I and C in this population.

Airway Resistance↗

PubMed1988

Measurement of ventilatory system resistance in infants and young children.

The mechanics of the ventilatory system were studied in 29 sleeping infants and young children by the analysis of a passive expiration following an end-inspiratory airway occlusion ('single breath' method). The ventilatory system time constant (tau rs) to compliance ratio yielded the value of ventilatory system resistance (Rrs). The calculated ventilatory system compliance correlated well with the slope of the quasi static pressure-volume curve (r = 0.97). The allometric relationship between Rrs and height (Rrs = 81.9.10(3).Ht (cm)-1.76, r = -0.82) is in agreement with forced oscillation measurements during the first year of life (Wohl et al., 1969). tau rs was found to increase significantly over the first months of life (P less than 0.01).

Airway Resistance↗

PubMed1988

[Fetal respiratory movements].

In the human species, foetal breathing movements are detectable from the fifteenth week of gestation and their incidence increases until the start of the third trimester. Over the last 10 weeks, breathing movements are present for 30% of the time. These are contemporaneous with body and ocular movements, suggesting an association between breathing movements and paradoxical sleep, as has been seen in the foetal lamb. These phases of activity alternate with phases of foetal immobility during which breathing movements are often absent. The incidence of foetal movements rises in the late post-prandial period, under the effect of maternal hyperglycaemia. After the establishment of regular uterine contractions, foetal breathing movements disappear, perhaps under the effect of prostaglandins E2 and/or a reduction in placental blood flow. Maternal hypercapnia leads to a rise in foetal breathing movements, which corresponds in the animal to the paradoxical sleep state. In the foetal lamb, hypoxaemia is accompanied by a cessation of breathing movements coinciding with a passage to quiet sleep. It is probable that the human foetus produces a similar reaction to hypoxaemia. During quiet sleep an inhibition of the respiratory centres would exist, disappearing during paradoxical sleep. Alcohol and certain anaesthetic agents lead to an inhibition of foetal breathing movements. The effect of tobacco remains controversial. The role of foetal breathing movements in pulmonary maturation is discussed in the human species.

Blood Glucose↗

PubMed1988

Assessment of thoracic gas volume by low-frequency ambient pressure changes in children.

The validity of a new method for measuring thoracic gas volume (TGV) was studied in 69 children, 4-16 yrs old, including twelve normal children and 57 children with an obstructive (n = 38) or restrictive (n = 19) respiratory disease. The method consisted of applying very slow (0.05 Hz) sinusoidal variations of ambient pressure around the body (delta Pam = 40 cmH2O peak to peak) and studying the relationship between delta Pam and the resulting gas displacement at the mouth (Vaw): TGVapc = PB.delta Vaw/delta Pam.cos phi, where PB is barometric minus alveolar water vapour pressure and phi the phase angle between Pam and Vaw. Functional residual capacities derived from TGVapc (FRCapc) were compared to the values obtained by plethysmography (FRCplet) and by helium dilution (FRCdil). FRCapc did not differ significantly from FRCplet in either the entire group (1.75 +/- 0.62 l vs 1.79 +/- 0.45 l) or in the patient subgroups. However, with the new method a trend to slightly lower FRCs was seen in patients with the most obstruction (p less than 0.05). FRCdil was significantly lower than both FRCapc and FRCplet (p less than 0.001), particularly in children with obstruction. Significant correlations were found between the three methods (p less than 0.001). On the other hand, the method investigated requires that the subject breathe very regularly for a period of several minutes. This was rarely achieved, so that the reproducibility of the measurements was unacceptably low. At present, the method cannot be recommended for routine use in 4-16 yr old children.

Adolescent↗

PubMed1987

[Treatment of patent ductus arteriosus in premature infants by indomethacin].

Over a 4-year period, 63 premature babies presenting with patent ductus arteriosus were treated with indomethacin at two different dosage levels (0.1 and 0.2 mg/kg). For all infants the permanent closure rate was 68% (56% with 0.1 mg/kg and 75% with 0.2 mg/kg - n.s.) and the positive response rate (i.e. permanent and transient closure) 84%. There was no difference between the two dosages in the incidence of side-effects, particularly on diuresis, and in mortality and morbidity rates; the overall mortality rate was 31%. Pharmacokinetic studies performed in 51 cases did not show any difference related to indomethacin dosage. The changes observed after 2 or 3 doses resulted from improvement in haemodynamics. This study confirms the effectiveness of indomethacin in the treatment of patent ductus arteriosus and suggests an advantage for the 0.2 mg/kg dose.

Diuresis↗

PubMed1987

Measurement of ventilatory system compliance in infants and young children.

Ventilatory system compliance (Crs) was measured in 32 sedated sleeping infants and young children aged 3-54 months breathing spontaneously through a face mask. Airways were occluded during expiration at different lung volumes above FRC and the corresponding airway pressure was measured. A pressure-volume relationship was then calculated by the least square method. To ensure the presence of the Breuer-Hering inspiratory inhibitory reflex, the percent increase of occluded expiratory time relative to the preceding unoccluded breath was calculated in 28 subjects where several end inspiratory occlusions had been maintained up to the next inspiratory effort. This index ranged from 4 to 100% and correlated negatively with age (r = -0.50, P less than 0.01). Crs ranged from 4.5 to 21.8 ml/cm H2O and correlated best with height (H) (Crs = 5.36 X 10(-4) H2.27, r = 0.94).

Air Pressure↗