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Biomedical subjects

Y Jammes

Publications and source records attributed to Y Jammes.

At least 55 records · Page 3Linked to original sources
PubMed1998

Does norepinephrine modify the effects of inhaled nitric oxide in septic patients with acute respiratory distress syndrome?

UNLABELLED: Hypoxia-related pulmonary vasoconstriction enhanced by norepinephrine could be deleterious in patients with the acute respiratory distress syndrome (ARDS) and sepsis. A prospective study compared the effects of nitric oxide on cardiorespiratory parameters, including the evaluation of right ventricular function in patients with ARDS and sepsis who were receiving or not receiving norepinephrine. METHODS: During a 15-month period, 27 patients with ARDS and sepsis were prospectively investigated (group 1: 15 patients not receiving norepinephrine; group 2: 12 patients receiving norepinephrine). Right ventricular ejection fraction was measured by thermodilution. After baseline measurements, nitric oxide was administered at increasing inspiratory concentrations. RESULTS: The ratio of oxygen tension in arterial blood to the fractional concentration of oxygen in inspired gas increased in the two groups. After logarithmic transformation of the data, an analysis of variance was performed that did not show any difference between the two groups. A dose-dependent decrease in mean pulmonary arterial pressure was observed in the two groups. This decrease and the increase in right ventricular ejection fraction induced by inhaled nitric oxide were more marked when patients received norepinephrine (P < 0.0001). CONCLUSION: Norepinephrine did not influence the beneficial effects of inhaled nitric oxide administered to patients with ARDS and sepsis on oxygenation.

Acute Disease↗
PubMed1998

Respective and combined effects of prone position and inhaled nitric oxide in patients with acute respiratory distress syndrome.

Inhaled nitric oxide (NO) and prone position (PP) are two of the new therapeutics proposed in the setting of acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate the hemodynamic and respiratory effects of NO and prone position in patients with ARDS. Fourteen patients, sedated, paralyzed, and ventilated using volume-control mode, were prospectively investigated. All patients had a radial artery catheter, a pulmonary artery catheter, and a 3-F fiberoptic thermistor catheter advanced via the femoral artery into the descending aorta. The protocol consisted of seven phases: baseline measurements in supine position, SP (T0); SP + NO (T1); baseline 2 in SP (T2); PP without NO (T3); NO + PP (T4); SP + NO (T5); and PP + NO (T6). Inhaled NO (T1) induced an increase in PO2/FI(O2) (from 128 +/- 44 to 180 +/- 75 mm Hg, p < 0.004). Prone position (T3) resulted in an increase in PO2/FI(O2) (193 +/- 83 mm Hg, p < 0.003 versus T0). The association of NO with PP (T4) resulted in a significant improvement in PO2/FI(O2) (261 +/- 98 mm Hg) when compared with T0, T1, and T3. Analysis of variance showed a significant and additive effect of NO and PP on both PO2/FI(O2) (p < 0.000) and shunt fraction (QS/QT) (p < 0.01). Since the association of NO with PP presents additive effects on oxygenation, this association can be proposed for the treatment of ARDS.

Administration, Inhalation↗
PubMed1998

Modifications of afferent activities from Tibialis anterior muscle in rat by tendon vibrations, increase of interstitial potassium or lactate concentration and electrically-induced fatigue.

Although previous experiments with a partially similar objective have been described in dogs, cats and rabbits, the purpose of this study was to identify and characterize mechanosensitive and chemosensitive muscle afferents in the anaesthetized rat since it is a widely used laboratory animal. The peroneal nerve innervating the tibialis anterior muscle was studied. Measurement of conduction velocities from compound action nerve potentials evoked by peripheral nerve stimulation allowed identification of group I-II (10.79+/-1.02 m/s), group III (2.96+/-0.58 m/s) and group IV (0.46+/-0.07 m/s) afferent fibers. Computation of the different compound potential areas showed that afferents I and II arising from spindles and tendon organs represented 9.65+/-2.2%, whereas afferents III and IV arising from free nerve endings in muscle represented 90.35+/-2.2% (III, 46.66+/-2.71% and IV, 43.69+/-2.52%). Action potentials were recorded from teased nerve filaments. Mechanical tendon vibrations (10 to 90 Hz) were used to activate mechanoreceptors. Peak increase in afferent discharge (fimpulses) was measured at 50 Hz (n = 12/19 units) or 70 Hz (n = 7/19 units). Intra-arterial bolus injections of different concentrations of potassium chloride (KCl: 1 to 20 mM) or lactic acid (LA: 0.5 to 3 mM) elicited marked activation of III and IV afferents (n = 124). Enhancement of fimpulses was not proportional to the increase in [KCl] or [LA]. Activation of afferents plateaued when [KCl] was equal or greater than 5 mM while fimpulses peaked, then decreased, when [LA] was 1 mM. Muscle fatigue induced by direct electrical muscle stimulation (EIF) markedly activated group III-IV (n = 17/18) afferents (176.9+/-29.7% of control) which persisted for the 3 minutes of recovery from fatigue. Maximal fimpulses increases in response to LA (+67%) and KCl (+46.9%) injections and to EIF (+76.9%) were similar. This procedure for characterizing the functional properties of sensory nerve endings in a skeletal muscle may be used to assess further changes in sensory muscle paths in experimental rodent pathophysiological systems.

Afferent Pathways↗
PubMed1997

Influence of respiratory afferents upon the proprioceptive reflex of skeletal muscles in healthy humans.

Relationships between respiratory afferents and the motor drive to skeletal muscles are well documented in animals, but human data are scarce. Tonic vibratory response (TVR) elicited by mechanical tendon vibrations were explored in an arm (extensor digitorum, ED) and a leg (vastus lateralis, VL) muscle, in healthy subjects. Tendon vibrations were delivered during unloaded breathing and after 10 breathing cycles while the subject breathed through an inspiratory or expiratory resistive load in order to activate respiratory afferents. Inspiratory loaded breathing significantly enhanced TVR in ED and VL muscles whereas the effects of expiratory loading depended on the vibrated muscle (increased TVR in ED; decreased TVR in VL). These results suggest that inspiratory muscle afferents activated during inspiratory loading facilitate the gamma motor drive to arm and leg muscles whereas the activation of pulmonary vagal afferents during expiratory loading can exert a facilitating or suppressive influence on the gamma motor drive, depending on the limb muscle group.

Adult↗
PubMed1997

GABA(B) receptor blockade reduces resistive loading-induced hypoventilation in anesthetized rabbits.

We hypothesized that hypoventilation induced by resistive loaded breathing may result in part from the inhibition of central respiratory-related structures by gamma-aminobutyric acid (GABA), through the stimulation of GABA(B) receptors. In that case, ventilatory depression should be minimized by GABA(B) receptor blockade. To test this assumption, the ventilatory effects of a GABA(B) receptor antagonist (CGP 35348) were evaluated in two groups of urethane anesthetized rabbits, breathing either through an inspiratory resistive load (IRL group) or not (Control group). CGP 35348 did not modify baseline ventilation in the Control group. On the other hand, it partially reversed IRL-induced hypoventilation through a higher respiratory rate and central inspiratory drive. These data suggest that, unlike GABA(A) receptors, GABA(B) receptors would not play a part in eupneic breathing, but that they could participate in the hypoventilation resulting from an acute increase in the work of breathing.

Anesthesia, General↗
PubMed1997

Fatigue-induced changes in group IV muscle afferent activity: differences between high- and low-frequency electrically induced fatigues.

Recordings of group IV afferent activity of tibialis anterior muscle were performed in paralysed rabbits during runs of electrically induced fatigue produced by direct muscle stimulation at a high (100 Hz, high-frequency fatigue HFF) or a low rate (10 Hz, low-frequency fatigue LFF). In addition to analysis of afferent nerve action potentials, muscle force and compound muscle action potentials (M waves) elicited by direct muscle stimulation with single shocks were recorded. Changes in M wave configuration were used as an index of the altered propagation of membrane potentials and the associated efflux of potassium from muscle fibers. The data show that increased group IV afferent activity occurred during LFF as well as HFF trials and developed parallel with force failure. Enhanced afferent activity was significantly higher during LFF (maximal delta f(impulses) = 249 +/- 35%) than HFF (147 +/- 45%). No correlation was obtained between the responses of group IV afferents to LFF or to pressure exerted on tibialis anterior muscle. On the other hand, decreased M wave amplitude was minimal with LFF while it was pronounced with HFF. Close correlations were found between fatigue-induced activation of group IV afferents and decreases in force or M wave amplitude, but their strength was significantly higher with LFF compared to HFF. Thus, electrically induced fatigue activates group IV muscle afferents with a prominent effect of low-frequency stimulation. The mechanism of muscle afferent stimulation does not seem to be due to the sole increase in extracellular potassium concentration, but also by the efflux of muscle metabolites, present during fatiguing contractions at low rate of stimulation.

Action Potentials↗
PubMed1997

Correlation between muscle metabolism and changes in M-wave and surface electromyogram: dynamic constant load leg exercise in untrained subjects.

In untrained subjects exercising on a cycle at constant work loads presented at a sub- or suprathreshold level, reduced M wave amplitude with lengthening of duration was measured in vastus lateralis muscle during and after suprathreshold exercise. M wave changes were correlated with increased blood lactate concentration. At the two work load levels, the increase in root mean square of EMG was rapidly closely adjusted to that of oxygen consumption, confirming the reality of adaptative reflex mechanisms in leg muscles during cycling.

Adult↗
PubMed1997

Functional consequences of acute and chronic hypoxia on respiratory and skeletal muscles in mammals.

Reduced oxygen supply to contracting muscles affects not only the metabolic paths but also modifies the gain of sensorimotor reflex loops initiated from the activation of specialized nervous endings that detect the changes in muscle metabolism and membrane outflow of potassium. Large differences are found between skeletal muscles and the diaphragm with respect to their sensitivity to acute or chronic hypoxia. The diaphragm tolerates much more hypoxemia than do skeletal muscles, namely those constituted by a large proportion of slow twitch oxidative fibers. Acute hypoxemia or ischemia accentuates the inhibitory influences exerted by the afferent paths from muscle metaboreceptors. This adaptative response may be responsible for enhanced muscle wisdom phenomenon during fatiguing contractions under hypoxic conditions. Prolonged and severe chronic hypoxemia markedly reduces muscle force generation by skeletal muscles and their endurance to fatigue. Restoration of normal PaO2 levels in these individuals immediately improves maximal muscle performance, perhaps through more efficient excitation-contraction coupling. Recent data on the consequences of hypoxia on muscle metabolism and the associated changes in sensorimotor control strongly suggest that local acidosis cannot entirely explain all electromyogram changes found during and after fatiguing exercise.

Acute Disease↗
PubMed1997

Hyperbaric-induced enhancement of noradrenaline-evoked contraction in rat thoracic aorta.

The aim of this study was to investigate the effects of a high ambient pressure of He on vascular contraction induced by noradrenaline and to distinguish the effects of ambient pressure per se from those of increased pressure of inert gas. Rings of thoracic aorta were isolated from male Wistar rats. Isometric tension was measured in preparations exposed to 7.1 MPa (absolute pressure) of He. Dose-response curves for noradrenaline and contractions elicited by 120 mM KCl were compared with time-matched experiments performed at atmospheric pressure. The same protocol was also carried out under 7.1 MPa of N2. At the high pressure of He, the contraction elicited by noradrenaline was increased with no change in the response to K(+)-evoked depolarization. The tension developed in response to noradrenaline also increased under 7.1 MPa of N2 but the effects were less marked than during the He experiments. Moreover, the response to KCl was reduced in this circumstance. Hyperbaric conditions enhance the noradrenaline-induced contraction of rat aorta in vitro. This effect probably results from an action of pressure per se on activation of adrenoceptors. However, the hyperbaric-induced increase in vascular smooth muscle contraction is partially counteracted by high pressures of inert gases (N2, but also probably He), which impair the efficiency of the contractile machinery.

Adrenergic alpha-Agonists↗
PubMed1997

Nasal eupnoeic inhalation of cold, dry air increases airway resistance in asthmatic patients.

The aim of this study was to establish a relationship between bronchial hyperreactivity to carbachol and reflex bronchomotor response to the activation of cold receptors in the nose, and also to examine whether any differences exist between asthmatic patients with or without symptoms of rhinitis. The changes in interrupting resistance (Rint) induced by nasal eupnoeic inhalation of cold (-5 degrees C) dry air were measured in 22 normal subjects and in 18 asthmatic patients (nine of whom had asthma with rhinitis and nine without) with bronchial hyperreactivity to carbachol. In normal individuals, nasal cold air challenge induced a significant increase in Rint (+31%). This was also the case in asthmatic patients (asthma with rhinitis +49%; asthma alone +40%), but the increase was not significantly larger than for normal individuals. The magnitude of Rint increase induced by nasal cold air breathing was correlated with the sensitivity to carbachol (defined as the dose inducing a 50% increase in specific airway conductance (D50)) in asthmatic patients with symptoms of rhinitis. These observations suggest that airway hyperreactivity is associated with enhanced bronchoconstrictor response to the activation of nasal cold receptors, particularly when rhinitis is present.

Administration, Inhalation↗
PubMed1997

Doppler-echocardiography study of cardiac function during a 36 atm (3,650 kPa) human dive.

To determine the influence of a saturation dive on cardiac function, Doppler-echocardiographic measurements were compared at sea level and during a 36 atm (3,650 kPa) He-O2 dive (gas density: 7 g/liter) in four healthy men. Left ventricular systolic function was studied from time motion measurements. Transmitral flow (E:A ratio) and isovolumetric relaxation time were used to assess left ventricular diastolic function. Cardiac output was derived from systolic pulmonary and aortic valvular flows. Cardiac output decreased 4.4 +/- 0.8 vs. 5.9 +/- 1.2 liter/min at sea level) whereas stroke volume, left ventricular ejection fraction, atria and ventricular diameters remained unchanged. Thus, the decrease in cardiac output was attributed to bradycardia (56 +/- 8 vs. 73 +/- 9 beats/min at sea level) which probably resulted from the slight hyperoxia (PI(O2), 0.4 atm). We found no evidence of left ventricular diastolic dysfunction. nor did we find valvular regurgitation or pulmonary hypertension. We conclude that Doppler-echocardiography can be used safely to investigate cardiac function during human saturation dives. Our results suggest that a 36 atm He-O2 dive does not modify cardiac or systolic and diastolic function except for a slight decrease in cardiac output correlated to bradycardia.

Adult↗
PubMed1996

Reflex relationships between the cervical esophagus and the respiratory system in cats.

The present study focused on reflex relationships between the esophagus and the respiratory system in cats, namely the changes in airway tone and pulmonary circulation elicited by mechanical or acid (pH 2) stimulation of esophageal afferents. One-minute of sustained distension of the cervical esophagus increased tracheal pressure (PTr), decreased pulmonary artery pressure (PPA) and to a higher extent pulmonary blood flow (QPA) and lowered arterial blood pressure (Pa). This was associated with significant variations in arterial blood gases (increased PaO2 and decreased PaCO2). Acid stimulation of the cervical esophagus caused a marked increase in PTr and a modest fall in QPA. In both circumstances, cervical bivagotomy abolished PTr changes, whereas the changes in pulmonary hemodynamics but not in Pa were then accentuated. Further cervical sympathectomy suppressed the vascular response. These observations show the existence of reflex influences of esophageal afferents on the control of airway tone and pulmonary vascular resistance. The vagus nerve is the efferent arm of the bronchomotor reflex whereas modulation of the sympathetic control of pulmonary circulation seems to be responsible for the changes in pulmonary hemodynamics.

Animals↗
PubMed1996

Cardiorespiratory response to bicuculline during resistive loaded breathing in anesthetized rabbits.

We hypothesized that hypoventilation induced by resistive loaded breathing may result in part from an increase in gamma-aminobutyric acid (GABA) concentration in the central nervous system. Accordingly, ventilatory depression should be minimized by GABA receptor blockade. The effects of subseizure doses of the GABAA receptor antagonist bicuculline on the cardiorespiratory variables and cortical activities were evaluated in two groups of urethane anesthetized rabbits, breathing either through an inspiratory resistive load (IRL) or not. Bicuculline induced cardiorespiratory changes which consisted mainly of an augmented respiratory rate, through shortening of expiratory duration, and of bradycardia. Bicuculline effects did not significantly differ between both groups and were accompanied by high amplitude delta rhythmic cortical activities. These data show that GABAA receptors may exert a tonic depressive effect on the respiratory circuit and suggest that endogenous GABA release is not augmented by an acute increase in the work of breathing.

Airway Obstruction↗
PubMed1996

Assessment of an airway-to-pulmonary circulation reflex in cats.

In anesthetized, mechanically ventilated cats we studied the effects on pulmonary circulation of sustained distension or increased air flow stream in an isolated, innervated upper airway segment constituted by the cervical trachea, the larynx and the pharynx. Direct and averaged pulmonary artery pressures and blood flows were measured. In intact cats, sustained distension as well as increased air flow stream in the upper airway segment induced significant, marked increase in pulmonary artery pressure with concomitant decrease in blood flow. No change in heart rate occurred. Section of the superior laryngeal nerves (SLNs), which denervated the tracheolaryngeal segment but not the epipharynx, markedly reduced and delayed the pulmonary vascular response to mechanical stimulation of the upper airways. The response was not found after cervical bivagotomy. The present observations demonstrate the existence of an airway-to-pulmonary circulation reflex, largely mediated through SLNs afferent pathways, the vagus nerve constituting the efferent arm of the reflex.

Air Pressure↗
PubMed1996

Resistive loaded breathing changes the motor drive to arm and leg muscles in man.

Breathing through inspiratory or expiratory resistive loads activates respiratory afferents. In healthy individuals, we explored the recruitment of motor units in arm (adductor pollicis, AP and biceps branchialis, BB) and leg (vastus lateralis, VL) muscle groups during voluntary contractions sustained at 80% of maximal force. Quantitative EMG analysis consisted of measurement of energies in high (EH) and low (EL) frequency bands. EH and EL changes were measured at constant time, i.e. 10 and 20 s after the onset of plateau contraction. The resistive load was added to the inspiratory or the expiratory circuit for 10-min periods. Its value was high but not enough to induce changes in blood gases and blood pressure. Compared to muscle contractions performed during non-loaded breathing periods, inspiratory loading did not affect BB and VL contractions, whereas it induced significant changes in AP contraction, characterized by enhanced variations in EL value measured at 10 s. Expiratory loading affected solely the VP contraction. Then, EH decreased at 10 and 20 s while it increased always when VP contractions were executed during non-loaded breathing. Expiratory loading elevated the functional residual capacity (FRC), but the load-induced changes in VL contraction persisted when subjects adjusted their FRC to the control level. These data suggest that respiratory afferents influence the skeleto-motor drive. Thus, viscero-somatic reflex may be present in patients with severe obstructive pulmonary disease.

Adult↗
PubMed1996

Combined electromyography--31P-magnetic resonance spectroscopy study of human muscle fatigue during static contraction.

Metabolic changes measured by 31P-magnetic resonance spectroscopy and surface electromyograms were simultaneously recorded during isometric contraction of forearm flexor muscles sustained at 60% of maximal force until exhaustion. Throughout the fatigue trial, energy in the low-frequency (L) band continuously increased whereas energy in the high-frequency (H) band first increased and fell only prior to exhaustion. PCr content decreased linearly. Intracellular pH (pHi) transiently increased during the first 22 s of trial. The triggering of acidosis was associated with critical PCr values (35-70% of initial content) and decreased electromyogram (EMG) energy in the H band. Linear relationships were only found between energy in the L band, pHi, and PCr content. The interindividual variability of metabolic and EMG changes was high despite standardized conditions of contraction. Maximal PCr consumption was correlated with the maximal pHi decrease measured at the end of the trial. Overall, there was no correlation between H/L EMG ratio and changes in muscle metabolism.

Adult↗