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Biomedical subjects

C Gaultier

Publications and source records attributed to C Gaultier.

At least 91 records · Page 5Linked to original sources
PubMed1993

Vagal and chemoreceptor influences on abdominal muscle activity in awake lambs during hypoxia.

The ventilatory response to hypoxia is a complex phenomenon involving several control mechanisms. We designed this study to examine the dynamic control of abdominal muscle expiratory electromyogram (EMG) activity during room-air breathing and hypoxia and then to analyze the relative contribution of the chemoreceptors and vagal afferents. We studied 12 11- to 22-day-old awake nonsedated lambs, six intact and six vagotomized. To assess the dynamic influence of peripheral chemoreceptors on abdominal muscle expiratory activity, we performed transient testing of peripheral chemoreceptor function (pure O2 and N2 inhalation, KCN injection). To assess the influence of central chemoreceptor afferents, we compared results obtained during hypocapnic and isocapnic 15-min hypoxic runs (fractional concentration of inspired O2 0.08) in each lamb. We also compared results obtained in intact and vagotomized lambs so that the importance of vagal afferents could be assessed. We consistently observed abdominal muscle expiratory EMG activity in each lamb, whether intact or vagotomized, during baseline room air breathing; further recruitment was observed during hypoxia. We also consistently observed abdominal muscle expiratory recruitment during hypocapnic hypoxia in each lamb, although it was significantly less marked than during isocapnic hypoxia. Our transient testing of peripheral chemoreceptor function showed, furthermore, that peripheral chemoreceptor afferents dynamically modulate abdominal muscle expiratory activity. Thus, during hypoxia in 11- to 22-day-old awake nonsedated lambs, increased afferent information from peripheral chemoreceptors forcefully enhances abdominal muscle expiratory activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1993

Influence of pulmonary blood flow on gas exchange in piglets.

We previously reported that O2 diffusion was limited in piglets. To test the hypothesis of an inadequacy between diffusion and perfusion in piglets (< 4 wk) vs. older pigs (> 8 wk), we compared in these two age groups the effect of an increase (by opening an arteriovenous fistula) or a decrease (by inflating a balloon in the inferior vena cava) in cardiac output (Q) on gas exchange and on the O2 equilibration coefficient D/Q beta [ratio of the diffusion capacity of O2 (D) to the product of Q and the capacitance coefficient of blood (beta)]. In piglets but not in older pigs, a decrease in Q improved the alveolar-arterial Po2 difference (P < 0.05) and D/Q beta (P < 0.05), whereas an increase in Q had the opposite effect. Changes in the alveolar-arterial O2 difference and D/Q beta were linearly correlated with Q (r = 0.75, P < 0.01 and r = 0.88, P < 0.01, respectively). We suggest that the impaired O2 diffusion in piglets was due to inadequate diffusion-perfusion equilibrium of O2.

Aging↗
PubMed1993

Asynchronous chest wall movements during non-rapid eye movement and rapid eye movement sleep in children with bronchopulmonary dysplasia.

The aim of this study was to assess whether age-related changes in thoracic shape modify patterns of thoracoabdominal asynchrony (TAA) or applicability of phase angle analysis during sleep in young children with increased respiratory loads. We assessed TAA during polysomnographic monitoring in 14 young children (mean age 32 months, range 19 to 46; mean weight 12.5 kg, range 9.3 to 17) with severe bronchopulmonary dysplasia (BPD). Of the patients 10 were severely enough affected to require tracheostomy. We measured asynchrony of rib cage (RC) and abdominal (AB) movements at midinspiration and the corresponding phase angle from oscillographic recordings during both non-REM and REM sleep. We measured the amplitude of "paradoxical" displacement of either RC or AB during inspiration and expressed this as a percentage of the total displacement of the compartment. Of 9 children who manifested early inspiratory AB paradox during non-REM sleep, 7 showed a figure eight on the Konno-Mead diagram. The magnitude of abdominal paradox during non-REM sleep was significantly positively correlated with age (n = 14, r = 0.68; p < 0.01). Phase angle was significantly negatively correlated with dynamic lung compliance (n = 14, r = -0.66; p < 0.01). During REM sleep, expiratory abdominal muscle activity was abolished and all patients with abdominal paradox "converted" to an open loop with RC paradox during inspiration. Graphic assessment of the Lissajous figure on the Konno-Mead diagram indicated when midinspiratory phase angle analysis did not reflect the severity of TAA and can be used to infer patterns of respiratory muscle recruitment. We conclude that young children manifest patterns of TAA that differ from the early inspiratory RC paradox commonly observed in infants. Comparison of RC-AB loops between non-REM and REM sleep in the same child can assess increased thoracic inspiratory efforts and expiratory muscle activity as potential mechanisms for abdominal paradox, as distinct from diaphragm ineffectiveness.

Abdomen↗
PubMed1993

Sleep state organization in premature infants of less than 35 weeks' gestational age.

To assess sleep organization in premature infants of < 35 wk gestational age (w GA), we performed polygraphic recordings in 24 neurologically normal neonates (eight per group): artificially ventilated 27-30 and 31-34 w GA infants and nonventilated 31-34 w GA infants. Sleep states were defined by concordance of EEG and rapid eye movement criteria. Uninterrupted active sleep periods of > 13 min and quiet sleep periods of > 5 min were observed in all babies, except in one 33 w GA ventilated infant. Intervals from the beginning of recording to the 1st quiet sleep period varied from 0 to 63 min and intervals to the beginning of the longest sleep cycle varied from 5 to 84 min. Nonventilated 31-34 w GA infants had longer sleep cycles (p < 0.02), principally because of longer active sleep periods. However, percentages of different states in the cycles were similar in all groups. When body movements were required for state definition, amounts of active and quiet sleep diminished and the percentage of indeterminate sleep was augmented significantly. In conclusion, our study demonstrated that 1) sleep state differentiation is present as soon as 27 w GA; and 2) artificial ventilation, performed in a highly specialized neonatal intensive care unit, does not modify sleep organization of neurologically normal premature infants. We hypothesize that this "earlier" sleep state differentiation, compared with previous data, may be related to improvements in neonatal intensive care over recent years.

Electroencephalography↗
PubMed1993

[Risk factors for gastroesophageal reflux in chronic asthma].

In order to study risk factors for gastroesophageal reflux (RGO), we have analysed the clinical particulars, the spirometry and the different therapies of chronic asthmatics with and without RGO. RGO has been studied using 24 hour pH manometry in 53 patients suffering from chronic asthma. 70% of these patients had RGO, defined as oesophageal pH below 4, for 4.2% or more of the total time. The only predictive factor for the presence of RGO (log regression) was the dose of theophylline (P is equal to 0.02) whose average dose was higher in cases of RGO (9.1 plus or minus 2.3 mg/kg against 6.3 plus or minus 1.7 mg/kg, P is less than 0.03). Although the severity of the asthma and the spirometric parameters were similar. On the other hand, the severity of RGO, assessed as the percentage of the total time passed with a pH below 4 or correlated (multiple regression) with longevity of the disease (P is equal to 0.02) and the dose of theophylline (P is equal to 0.001). These results suggest that the treatment with theophylline and the duration of the asthma could constitute risk factors for RGO in chronic asthma.

Adolescent↗
PubMed1992

Dose-related bronchodilator response to aerosolized salbutamol (albuterol) in ventilator-dependent premature infants.

We used a placebo-controlled standardized protocol to define the dose-response relationship to the beta-adrenergic bronchodilator salbutamol (albuterol) in 10 ventilator-dependent premature infants at a postnatal age of 13.3 +/- 4.9 days. Passive respiratory system resistance and compliance were measured at baseline and 10 minutes after administration of salbutamol via a metered-dose inhaler and spacer device. Salbutamol caused a significant dose-related response with a 33% mean decrease in respiratory system resistance (p less than 0.05) and a 67% mean increase in respiratory system compliance (p less than 0.001). In seven and six patients, respectively, 100 micrograms of salbutamol caused significant improvement in resistance and compliance; 200 micrograms was required in the remainder, but one patient had no improvement in compliance. Oxygen saturation increased linearly with the increase in compliance. In 7 of the 10 infants, the duration of action of 200 micrograms of salbutamol on the following day was 3 hours. We conclude that bronchodilator treatment may be useful in the management of ventilator-dependent neonates with respiratory distress syndrome.

Aerosols↗
PubMed1992

Clinical and therapeutic aspects of obstructive sleep apnea syndrome in infants and children.

Sleep related increases in respiratory resistive loads in infants and children may or may not be associated with complete obstruction, i.e. obstructive apneas. Nevertheless, important clinical symptoms, both nocturnal and diurnal, may be present and should be taken into consideration. A thorough investigation must be performed to select the most appropriate therapy.

Airway Resistance↗
PubMed1992

Cardiac, respiratory, and arousal responses to an esophageal acid infusion test in near-term infants during active sleep.

This study was designed to determine the cardiac, respiratory, and arousal responses to an esophageal acid infusion test in near-term infants free from neurological, gastroesophageal, and cardiopulmonary disease at time of testing during active sleep. Eight infants (gestational age 28-37.5 weeks, postconceptional age 36-40 weeks) were tested. Using standardized procedures and timing, we compared the cardiac, respiratory and arousal responses during a control period and during distal esophageal saline and acid infusion periods. The duration of each of these periods was 5 min. The pH of the acid infusion was 2.2. We found that this mild distal esophageal acid infusion test induced significant prolongation of the interval between successive electrocardiogram R waves compared with control and saline infusion periods (806.5 +/- 145.7 ms, 478.8 +/- 49.4 ms, and 468.8 +/- 37.2 ms, respectively; p less than 0.01) and of the duration of the respiratory cycle (2.9 +/- 0.7 s, 1.5 +/- 0.3 s, and 1.5 +/- 0.2 s, respectively; p less than 0.01). Esophageal acid infusion elicited significant electroencephalogram (EEG) arousal responses. The number of the EEG arousals was significantly increased during the acid period as compared with control and saline infusion periods (2.9 +/- 1.4, 0.5 +/- 0.5, and 0.4 +/- 0.5, respectively; p less than 0.01). Total arousal duration was significantly increased during acid as compared with control and saline infusion periods (42 +/- 17.5 s, 4.5 +/- 5.1 s, and 3.5 +/- 5.0 s, respectively; p less than 0.01). We conclude that distal esophageal acid stimulation elicits significant cardiac, respiratory, and EEG arousal responses in near-term infants during active sleep.

Administration, Oral↗
PubMed1992

Neonatal pattern of breathing during active and quiet sleep after maternal administration of meperidine.

The aim of this study was to reappraise the effects of maternal meperidine administration on breathing pattern during the first hours of life taking into account the state of alertness. Because breathing instability is more pronounced during active sleep, we hypothesized that meperidine administration might create a greater risk for respiratory instability during active sleep, the prominent sleep state in newborns. We studied eight full-term, healthy newborns whose mothers had received a continuous i.v. infusion of meperidine (81 +/- 9 mg) that was terminated 5.5 +/- 2.1 h before delivery. These infants were compared with a control group of eight full-term newborns whose mothers did not receive any opioids. In both groups, all babies were delivered vaginally after a normal labor and had Apgar scores of 9 or 10 at 1 and 5 min. Neonatal gastric secretion and maternal venous and umbilical venous blood were sampled at delivery for determination of meperidine concentration. From 60 to 300 min after delivery, behavioral sleep states and thoracic and abdominal movement as well as transcutaneous arterial oxygen saturation (SaO2) were monitored continuously. The number of apneic spells lasting more than 3 s during 100 min of recording and the percentage of time with SaO2 below 90% in each sleep state were recorded. During quiet sleep, all respiratory variables were similar in both groups. During active sleep, there were significantly more apneic episodes (37.1 +/- 25.1 versus 11.2 +/- 13.9) and a higher percentage of time with SaO2 less than 90% (14.3 +/- 16.7% versus 1.3 +/- 1.5%) in the meperidine group than in the control group (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1992

Accuracy of respiratory inductive plethysmography during wakefulness and sleep in patients with obstructive sleep apnea.

To assess the accuracy of the respiratory inductive plethysmograph (RIP) during sleep in obese patients with obstructive sleep apnea (OSA), we monitored 13 patients with OSA during wakefulness and nocturnal sleep with simultaneous measurements of tidal volume from RIP and integrated airflow. Patients wore a tightly fitting face mask with pneumotachograph during wakefulness and sleep. Calibrations were performed during wakefulness prior to sleep and compared with subsequent wakeful calibrations at the end of the study. Patients maintained the same posture during sleep (supine, 11; lateral, two) as during calibrations. There were no significant differences in calibrations before sleep and after awakening. The mean error in 13 patients undergoing RIP measurements of tidal volume during wakefulness was -0.7 +/- 3.4 percent while that during sleep was 2.1 +/- 14.9 percent (p < 0.001). The standard deviation (SD) of the differences between individual breaths measured by RIP and integrated airflow was 9.8 +/- 5.5 percent during wakefulness and 25.5 +/- 18.6 percent during sleep (p < 0.001). During both wakefulness and sleep, errors in RIP tidal volume were not significantly correlated with body mass index. In 12 patients with at least 10 percent time in each of stages 1 and 2 sleep, SD was greater in stage 2 sleep compared with wakefulness and stage 1 (p < 0.001). In three patients who manifested all stages of sleep, SD was greater in REM sleep than in wakefulness and all stages of non-REM sleep (p < 0.001). In three patients who manifested all stages of sleep, SD was greater in REM sleep than in wakefulness and all stages of non REM sleep (p < 0.001). This was associated with paradoxic motion of the rib cage in two patients during REM. We conclude that, despite increased errors in individual breath measurements during sleep, more marked during stages 2 and REM sleep, RIP is clinically useful to measure ventilation quantitatively in obese patients with sleep apnea. The criterion of a decrease of 50 percent in tidal volume assessed by RIP is appropriate to define hypopneas in such patients.

Adult↗
PubMed1992

Accuracy of measurements of HbF with OSM3 in neonates and infants.

The accuracy of the Radiometer OSM3 oxymeter for measurement of fetal haemoglobin (HbF) in infants was investigated, and compared to one of the standard reference methods using alkali electrophoresis of haemoglobin. Blood samples of 37 infants with different gestational (27-41 weeks) and postnatal (1-198 days) ages were analysed. The two methods gave very close results but a significant mean difference (range -4.5-16.5%). However, agreement between the two methods was judged clinically acceptable (95% limits of agreement -7.5-15.5%). A rapid determination of HbF percentage, using OSM3, is an important determinant for correct assessment of oxygen saturation in newborn infants in intensive care units.

Electrophoresis↗
PubMed1992

[5-Fluoro (3H) pyrimidine-4-ones: synthesis, reactivity and pharmacological properties].

Fourteen fluoro pyrimidine-4-ones, four fluoro bispyrimidine-4-ones and two fluoro pyrimidine-4-ones with fused ring have been prepared. The reactivity of the carbonyl group of two pyrimidine-4-ones phosphorus oxychloride was studied. The 4-chloro pyrimidines reacted with ammonia or morpholine giving 4-substituted pyrimidines. Eight compounds are evaluated for their anti-inflammatory and anti-convulsivant properties: they were found to be weakly active against oedema and three of them protected rats form tonic convulsions.

Animals↗
PubMed1991

Hypoxia-induced bronchial responsiveness in awake sheep: role of carotid chemoreceptors.

Hypoxia enhances bronchial responsiveness in sheep and dogs and we recently reported a similar effect in asthmatic subjects. Activation of a reflex arc due to stimulation of peripheral chemoreceptors has been suggested to explain this finding. We evaluated the contribution of carotid body chemoreceptors to hypoxia-induced bronchial responsiveness in conscious sheep. Incremental concentrations of aerosolized methacholine were given to each of seven sheep ventilated successively (in a random order) with a normoxic and a hypoxic gas mixture (15% O2 in N2), both before and after peripheral surgical chemodenervation. Hypoxia alone did not affect lung mechanics in intact or chemodenervated animals. Bronchial responsiveness to methacholine was significantly increased by hypoxia in intact sheep, as compared to chemodenervated sheep. We conclude that hypoxia has a stimulating effect on bronchial responsiveness in awake sheep similar to that seen in human patients with asthma. This increased responsiveness may be mediated by hypoxic stimulation of carotid body chemoreceptors, which in turn may influence the nervous control of airway calibre.

Airway Resistance↗
PubMed1991

Abdominal muscle activity during CO2 rebreathing in sleeping neonates.

Comparison of the abdominal muscle response to CO2 rebreathing in rapid-eye-movement (REM) and non-REM (NREM) sleep was performed in healthy premature infants near full term. Eight subjects were studied at a postconceptional age of 40 +/- 1.6 (SD) wk (range 38-43 wk) during spontaneous sleep. Sleep stages were defined on the basis of electrophysiological and behavioral criteria, and diaphragmatic and abdominal muscle electromyographic activity was recorded by cutaneous electrodes. The responses to CO2 were measured by a modified Read rebreathing technique. The minute ventilation and diaphragmatic and abdominal muscle electromyographic activities were calculated and plotted against end-tidal CO2 partial pressure. Both the ventilatory and diaphragmatic muscle responses to CO2 decreased from NREM to REM sleep (P less than 0.05). Abdominal muscles were forcefully recruited in response to CO2 rebreathing during NREM sleep. In REM sleep, abdominal muscle response to CO2 was virtually absent or decreased compared with NREM sleep (P less than 0.05). We conclude that 1) the abdominal muscles are recruited during NREM sleep in response to CO2 rebreathing in healthy premature infants near full term and 2) the abdominal muscle recruitment is inhibited during REM sleep compared with NREM sleep, and this REM sleep-related inhibition probably contributes to the decrease in the ventilatory response to CO2 rebreathing in REM sleep.

Abdomen↗