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Biomedical subjects

C Gaultier

Publications and source records attributed to C Gaultier.

At least 127 records · Page 7Linked to original sources
PubMed1989

[Respiratory disorders during sleep in children].

Respiratory disorders that occur in children asleep are frequent. They are evaluated by studying the respiratory function at each stage of sleep, as determined by neurophysiological criteria, and they must be interpreted on the basis of what is known of respiratory adaptation during sleep in healthy infants. Respiratory disorders during sleep may be due to: (1) obstructive sleep apnoea syndrome caused by an obstruction of the upper airways, most frequently by enlarged tonsils; (2) nocturnal episodes of acute on chronic obstructive lung disease, such as cystic fibrosis, sequelae of viral infection, ciliary dysfunction, broncho-pulmonary dysplasia; (3) nocturnal asthma; (4) alveolar hypoventilation of central origin. The short-or long-term risk of respiratory disorders during sleep is their repercussions on pulmonary circulation and right heart function.

Adolescent↗
PubMed1989

Passive total respiratory system compliance and gas exchange in newborns with hyaline membrane disease.

Passive total respiratory system compliance (CRS) and gas exchange measurements were performed in nine newborns during the course of hyaline membrane disease. None of the subjects presented bronchopulmonary dysplasia at follow-up investigations. Gestational age ranged from 29 to 37 weeks. CRS was measured by the multiple occlusion technique. Gas exchange parameters were the fraction of inspired oxygen concentration (FIO2) and the arterial/alveolar ratio for oxygen (a/AO2 ratio). In each subject four tests were performed: test 1 during the first day of life; test 2 during the second day of life; test 3 between the fourth and the seventh days of life; test 4 after extubation. CRS/BW (CRS normalized for body weight) was not statistically different at tests 1-3, but it significantly increased (P less than 0.001) between tests 3 and 4. FIO2 and a/AO2 ratio presented no statistical difference at tests 1-2 but several significant differences were noted thereafter: FIO2 decreased significantly (P less than 0.001) when results from tests 2 and 3 were tabulated. The a/AO2 ratio increased significantly between tests 2 and 3 (P less than 0.001), and a further significant increase (P less than 0.01) was also noted when results obtained during tests 3 and 4 were compared. A significant relationship existed during the evolution of the disease between CRS/BW and gas exchange parameters (FIO2 and a/AO2 ratio) (P less than 0.01), but gas exchange improved earlier than lung mechanics.

Bronchopulmonary Dysplasia↗
PubMed1989

Breathing pattern during exercise in untrained children.

Breathing pattern during exercise on a cycle ergometer was studied in 18 untrained children aged from 6 to 15 years of age (9 boys, 9 girls). Oxygen uptake, tidal volume, minute ventilation, all normalized for body weight (VO2BW, VT BW, VE BW), respiratory frequency (f), inspiratory (TI) and expiratory (TE) times, ratio TI over total duration of the respiratory cycle (TI/TTOT) and mean inspiratory flow (VT BW/TI) were measured: (1) at rest (W0) and at the highest load (maximal cardiac rate) of an incremental exercise (W1); (2) in steady state conditions, at 50% of W1 (W1/2) and at 2/3 of W1 (W2/3). VO2BW, VT BW, VE BW, TI/TTOT, VT BW/TI increased significantly (P less than 0.01) from W0 to W1. Behaviour of f and TI were different from the latter parameters: f increased and TI decreased significantly from W0 to W1/2 (P less than 0.01) and from W1/2 to W2/3 (P less than 0.01) but remained similar at W2/3 and W1. We observed a relationship between VO2 BW and VT BW/TI, and between VT BW and TI/TTOT at each step of workload. We conclude that untrained children adapt the pattern of breathing during exercise, as at rest, to metabolic demand. However, the increase in f and the decrease in TI are limited at maximal workload.

Adaptation, Physiological↗
PubMed1989

Effects of sleep deprivation on respiratory events during sleep in healthy infants.

This study was designed to determine the effects of sleep deprivation on respiratory events during sleep in healthy infants. Ten unsedated full-term infants (1-6 mo) were monitored polygraphically during "afternoon naps" on a control day and on the day after sleep deprivation. Respiratory events, i.e., central apnea, obstructive apnea and hypopnea, and periodic breathing were tabulated. Results for respiratory events were expressed as 1) indexes of the total number of respiratory events and of specific respiratory events per hour of total sleep (TST), "quiet" sleep (QS) and "active" sleep (AS) times; 2) total duration of total and specific respiratory events, expressed as a percentage of TST, QS, and AS times. After sleep deprivation, significant increases were observed for 1) respiratory event (P less than 0.001), central apnea (P less than 0.05), and obstructive respiratory event (P less than 0.01) indexes; 2) respiratory event time as a percentage of TST (P less than 0.002) and as a percentage of AS time (P less than 0.001); 3) obstructive respiratory event time as a percentage of TST (P less than 0.01), QS (P less than 0.05), and AS times (P less than 0.002). The present study shows that short-term sleep deprivation in healthy infants increases the number and timing of respiratory events, especially obstructive events in AS.

Female↗
PubMed1989

Cholinergic component of histamine-induced bronchoconstriction in newborn guinea pigs.

The magnitude of parasympathetic reflex-mediated bronchoconstriction during histamine infusion was compared in anesthetized paralyzed newborn and adult guinea pigs. The animals were ventilated using a constant-flow ventilator, and the conductance and compliance of the respiratory system were continuously monitored. We found that reactivity to histamine infusion was less in newborns than in adults, because newborns required a larger dose of histamine than adults (300 vs. 125 ng.kg-1.s-1) to produce an equivalent decrease in conductance (42 +/- 13 vs. 42 +/- 15%). Vagal interruption by bilateral cervical vagotomy or muscarinic blockade with atropine (3 mg/kg) significantly reduced the bronchoconstrictor response to histamine in adults. By contrast, neither vagotomy nor atropine significantly changed this response in the newborns. These results indicate the lack of a vagal component in the bronchoconstriction that histamine induced in the newborns. Their relative unresponsiveness to histamine might partly be related to the fact that, in the newborn, histamine mainly acts directly via its airway receptors.

Aging↗
PubMed1989

Sleep-related abdominal muscle behavior during partial or complete obstructed breathing in prepubertal children.

We have evaluated the influence of nonrapid eye movement (NREM), REM sleep, and arousal on abdominal muscle contractions during snoring and/or obstructive apnea in 10 prepubertal children. All children were known habitual snorers and eight had a sleep apnea index above 10. During stage 3-4 non-REM sleep, non-apneic breathing with snoring was always associated with the presence of expiratory abdominal muscle electromyogram (EMG) discharges. During non-REM sleep apneas, abdominal muscle EMG discharges increased from the beginning to the end of each apnea. Termination of non-REM sleep apnea was marked by an "EEG arousal" in 12% of the apneic events and by a "movement arousal" in the other 88%. The highest abdominal muscle EMG discharge was always observed during the arousal response. During "phasic" REM sleep, abdominal muscle EMG discharges were absent during both nonapneic breathing (with or without snoring) and obstructive apneas. All REM sleep apneas ended with a "movement arousal," during which abdominal muscle EMG discharges were observed. Thus, abdominal muscle EMG discharges associated with "arousal" were seen independent of the immediately preceding sleep state.

Abdominal Muscles↗
PubMed1989

Relationship between respiratory pauses and heart rate during sleep in normal premature and full-term newborns.

To investigate the relationship between central respiratory pauses and heart rate, we performed polygraphic recordings in 23 normal newborns (35 to 41 weeks conceptional age). We monitored the electroencephalogram, rapid eye movements, movements of the upper and lower limbs, chin and diaphragmatic electromyogram, electrocardiogram, thoracic and abdominal respiratory movements, air flow and transcutaneous PO2. Heart rate changes were analysed by computer measurement of R-R intervals and by cardiotachography. Respiratory pauses occurring after body movements and those not preceded by movements were studied separately. We analysed 1128 respiratory pauses greater than 3 s duration. No respiratory pause lasted more than 12 s. Independently of age, sleep state and respiratory pause duration, heart rate was significantly lower at the onset of respiratory pause, compared to control periods (selected away from the pause: 10 s before its onset and 20 s after its end). Heart rate slowed still further through the respiratory pause and reverted toward the baseline level after its end. When no movements preceded the respiratory pause, heart rate just before the pause was lower compared to control periods. These findings suggest the existence of simultaneous central commands responsible for both respiratory pause and heart rate deceleration.

Electrophysiology↗
PubMed1989

Technique of on-line analysis of diaphragmatic electromyogram activity in the newborn.

The present study provides an on-line analysis of diaphragmatic electromyographic activity (EMGdi) in newborns. EMGdi was recorded using surface electrodes. EMGdi signals were processed using a microcomputer (Apple IIe). The centroid frequency (Fc) and the high over low (H/L) frequencies ratio of the power spectrum were calculated. Furthermore the model frequency (Fo) was computed by an autoregressive model of the EMG signal. EMGdi analysis was performed in seven healthy spontaneously breathing preterm newborns. Fc ranged from 46-62 Hz. Fc was significantly lower than Fo in four of the seven preterm newborns. The coefficient of variation for Fc was significantly lower than for the H/L ratio (p less than 0.001). The coefficients of variation for Fo and Fc were not significantly different, but the percentage of rejected calculations for Fo was significantly higher than for Fc (p less than 0.01). Therefore, in healthy preterm newborns, Fc appears to be the best index of EMGdi analysis.

Diaphragm↗
PubMed1988

The sustained ventilatory response to hypoxic challenge in the awake newborn piglet with an intact upper airway.

The diphasic ventilatory response to steady-state hypoxia has been reported in anesthetised, intubated newborn piglets. We questioned whether this diphasic response persisted in the awake, spontaneously breathing piglet. Nine piglets, at one day of age, breathing spontaneously through a fitted mask and pneumotachograph were examined, monitoring the minute ventilation. (VE) tidal volume (VT), respiratory frequency (f), mean inspiratory flow (VT/TI), inspiratory time (TI). The piglets were studied in room air, followed by a step change to an FIO2 of 0.12, and a subsequent step-change to an FIO2 of 0.08. For each step-change in the FIO2 there was a decline in VT during hypoxia, but the VE increased significantly throughout the hypoxia through a progressive increase in both f and VT/VI. Thus, the awake newborn piglets were able to sustain the increase in VE during hypoxia. These results differ from previous observations of the diphasic VE response to hypoxia in lightly anesthetised piglets suggesting that the ventilatory response to steady state hypoxia is dependent upon experimental conditions. Further, the finding of a sustained ventilatory response in awake piglets breathing through an intact upper airway differs from previous studies in lambs and kittens suggesting a difference in the level of maturity at birth between the species.

Animals↗
PubMed1988

Passive compliance of total respiratory system in preterm newborn infants with respiratory distress syndrome.

The passive compliance of the total respiratory system (CRS) was measured by the occlusion technique in 34 preterm newborn infants with respiratory distress syndrome. Gestational age ranged from 27 to 33 weeks. Preterm newborn infants were divided into four groups on the basis of clinical criteria. Group 1 consisted of 10 infants tested during the first postnatal days (1 to 3 days) while acutely ill and requiring ventilation and oxygen therapy. After the acute phase of respiratory distress syndrome, two groups were tested: group 2 consisted of nine infants (5 to 22 days of age) who no longer required ventilation, and group 3 consisted of six infants (7 to 28 days of age) who subsequently had bronchopulmonary dysplasia. Group 4 consisted of nine infants older than 1 month of age with confirmed bronchopulmonary dysplasia. Group 1 had significantly lower CRS and CRS normalized for body weight (CRS/BW) than group 2 had (P less than 0.001). In groups 3 and 4 CRS was significantly lower than in group 2 (P less than 0.001), as was CRS/BW (P less than 0.001). There was no significant difference in CRS and CRS/BW values between groups 3 and 4. This cross-sectional study in preterm infants with respiratory distress syndrome suggests that CRS may have predictive value in regard to development of bronchopulmonary dysplasia after the acute phase of respiratory distress syndrome.

Bronchopulmonary Dysplasia↗
PubMed1988

Mechanism of improvement in pulmonary gas exchange during growth in awake piglets.

Previous studies have shown a lower arterial PO2 (PaO2) in infants and young animals than in adults. To investigate the mechanism of this impairment of gas exchange we studied 13 piglets from 12 to 65 days of age. Two days after instrumentation we measured the distribution of ventilation-perfusion ratios (VA/Q) by use of the multiple inert gas technique on awake animals. We showed that PaO2 is lower in young animals, increasing from 72 +/- 11.5 Torr before 2 wk to 102 Torr at 2 mo. This hypoxemia is due to an enlarged alveolar-arterial O2 pressure difference that significantly decreases with age. This impairment in gas exchange is not due to shunting (0.6 +/- 1.3%). Mean dead space (36 +/- 11%) was not related to age. Mean modes of perfusion and ventilation did not differ significantly between age groups. However, the dispersion of perfusion as expressed by its logSD decreased significantly with age, whereas dispersion of ventilation remained constant. Furthermore, in the young animals only, a significant difference was evidenced between measured alveolar-arterial PO2 gradient and the value predicted by the inert gas model. We therefore conclude that the impairment of gas exchange in piglets is due to two mechanisms: VA/Q mismatch and diffusion limitation for O2.

Age Factors↗
PubMed1988

Mild isocapnic hypoxia enhances the bronchial response to methacholine in asthmatic subjects.

We studied the effect of mild isocapnic hypoxia (FIO2 = 15.5%) on lung mechanics, heart rate, circulating plasma catecholamines, and bronchial responsiveness to methacholine in ten asthmatic adults. Hypoxia did not alter lung mechanics (i.e., dynamic pulmonary compliance [CLdyn], pulmonary resistance [RL]) nor did it increase plasma catecholamines, but it significantly increased bronchial responsiveness to aerosolized methacholine, as assessed by the fall in forced expiratory volume in one second (FEV1: 1.2 +/- 0.18 versus 0.9 +/- 0.14 L/s, p less than 0.05), the rise in RL (RL: 19.1 +/- 1.4 versus 8.4 +/- 1 cm H2O/L/s, p less than 0.05), and the steeper slope of the dose-response curve to methacholine. We concluded that the hypoxic characteristic of asthmatic attacks may aggravate airflow obstruction.

Adult↗
PubMed1988

Diaphragmatic and genioglossus electromyographic activity at the onset and at the end of obstructive apnea in children with obstructive sleep apnea syndrome.

We studied the activity of the diaphragm and of the genioglossus at the onset and at the end of obstructive sleep apnea in children. Seven children (mean age 46 months, range 15-87) with obstructive sleep apneas mainly due to enlarged tonsils were tested during natural sleep. We recorded sleep stages (neurophysiological criteria), nasal and buccal air flow (thermistors), thoracoabdominal motion (magnetometers), genioglossus and diaphragm electromyographic activity (EMG) (surface electrodes), and transcutaneous partial pressure of oxygen (Radiometer 44 degrees C). A total of 153 obstructive apneas for the whole group of patients was studied. Compared to the preceding unoccluded breaths, genioglossus and diaphragm EMG data showed that 1) at the onset of obstructive apnea there was no significant decrease in genioglossus and/or diaphragm EMG, contrasting with published data for obese adults, and 2) at the end of obstructive apnea, significant preferential increase in genioglossus EMG, not related to the decrease in transcutaneous partial pressure of oxygen, was found as in obese adults. This study showed that different mechanisms may control the onset of obstructive apnea in children as compared to adults, whereas children and obese adults share the same preferential increase in genioglossus EMG at the end of obstructive apnea.

Child↗
PubMed1988

Effect of maturation on heart rate response to ocular compression test during rapid eye movement sleep in human infants.

Thirty-three premature and full-term infants (31.5-50 wk postconceptional age) free from neurologic and cardiopulmonary disease at time of testing, underwent a standardized ocular compression test during polygraphically controlled rapid eye movement sleep. RR intervals were measured on the ECG before and during ocular compression. RR interval changes during ocular compression were compared to the preceding 60-s mean RR interval in each infant. Results were analyzed relative to gestational age, postnatal age, and postconceptional age. Baseline heart rate during REM sleep decreased with postconceptional age. During ocular compression, there was a significant negative correlation between the longest RR interval or the "latency" variable with postconceptional age. Latency is defined as the time, in milliseconds, from beginning of eyelid pressure to the first measurable RR increase compared to mean control RR + 1 SD. Our results indicate that during rapid eye movement sleep, "baseline heart rate" decreases with maturation, an effect supposedly related to increased vagal activity, whereas the heart rate response on ocular pressure stimulus, a vagally mediated reflex, is significantly influenced and blunted with maturation.

Autonomic Nervous System↗