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Biomedical subjects

M C Zattara-Hartmann

Publications and source records attributed to M C Zattara-Hartmann.

13 recordsLinked to original sources
PubMed2001

The changes in leg blood flow during and after mild or severe acute hypoxaemia in healthy humans.

The present study examines the leg blood flow changes in resting healthy humans during and after a 10-min period of mild (PaO2=5.60 kPa) or severe hypoxaemia (PaO2=4.53 kPa) induced by breathing hypoxic gas mixtures. A Colour Duplex Scan system allowed to measure the cross-sectional area (CSA) and mean blood flow (Q) in a femoral artery (FA) and a femoral vein (FV) and also in an artery supplying leg muscles (medial gastrocnemius artery, MGA). During the mild as well as the severe hypoxaemia and their recovery periods, no significant variations of Q and CSA occurred in FA and FV. During the mild hypoxaemia and the first 10 min of the recovery period, Q and CSA of MGA increased (maximal changes: +84 and +20%, respectively). By contrast, a marked Q decrease and a reduced CSA were measured in MGA during the severe hypoxaemia (-67 and -60%, respectively). This reduced muscle blood flow was followed by a vasodilatation (CSA increase = +30%), which began 10 min after the hypoxaemia ended and persisted for a further 10-min period. This study shows that the time course of muscle blood flow changes in response to acute hypoxaemia depends on the PaO2 level. Reverse effects were measured during the mild or the severe hypoxaemia, whereas a post-hypoxaemic vasodilatation occurred in all circumstances.

Adult↗
PubMed1999

Changes in airway resistance induced by nasal or oral intermittent positive pressure ventilation in normal individuals.

Nasal intermittent positive-pressure ventilation (nIPPV) is used for the treatment of respiratory failure in patients with neuromuscular disease. The aim of the present study was to demonstrate that nIPPV may activate nose receptors, the consequence of which being reflex changes in lung resistance. The changes in interrupter resistances (Rint) in response to nIPPV were tested before and after local anaesthesia of the nasal mucosa in normal subjects. They were compared to the Rint changes induced by oral intermittent positive-pressure ventilation (oIPPV) in the same individuals. Rint was measured during 10-min periods of nIPPV or oIPPV at a constant rate (15 L x min(-1)), but at two different stroke volumes (0.8 and 1.2 L). Inspired temperature and relative humidity were held constant. nIPPV with 1.2 L (17 mL x kg(-1)) significantly increased the Rint value (+22%). This effect disappeared after nose anaesthesia or after inhalation of a cholinergic antagonist. oIPPV never changed Rint, even though the associated hypocapnia was present and more accentuated than during nIPPV. Adding CO2 to the inspired gas during nIPPV and oIPPV trials suppressed the Rint changes. The present study suggests the existence of a nasopulmonary bronchoconstrictor reflex elicited through the stimulation of nasal mechanoreceptors, their activity being markedly influenced by the changes in expired CO2 concentration.

Adult↗
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

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↗
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

Electrocardiogram changes during positive pressure breathing in rabbits.

Positive pressure breathing produced by mechanical ventilation with an expiratory threshold load (ETL) may modify electrocardiogram (ECG) complexes independently of any recording artefact due to lung volume changes. Anaesthetized, paralyzed rabbits were treated for about 2 h, then killed. In intact then vagotomized animals two situations were studied successively. Firstly, positive inspiratory pressure breathing, and secondly, positive inspiratory plus expiratory pressure breathing by adding ETL to mechanical ventilation. Arterial blood gases were measured and held constant throughout the challenge. Oesophageal pressure, giving indirect measurement of intrathoracic pressure, arterial blood pressure, blood flows in abdominal aorta and inferior vena cava and standard ECG recordings were made at baseline condition during mechanical ventilation, then at the end of a 10-min period of ETL breathing. The ETL breathing decreased arterial blood pressure significantly and reduced arterial and venous blood flows in the same proportion. No change in the duration of ECG complexes was noticed. However, ETL markedly reduced the amplitude of P- and T-waves, but not that of R-wave, an effect significantly accentuated after vagotomy. The ETL breathing increased the T-vector angle, with no associated change in QRS vector angle. The present animal investigations revealed that positive pressure breathing modifies the ECG independently of the consequences of ETL-induced lung volume changes. We speculate that the changes in P- and T-wave amplitude may have resulted from a reduced transmural pressure gradient between the epicardium and endocardium.

Animals↗
PubMed1996

Acute hypoxemia depresses the cardiorespiratory response during phase I constant load exercise and unloaded cycling.

The effects of acute inhalation of hypoxic gas mixtures on minute ventilation (VE), respiratory frequency (fR) and heart rate (HR) were studied in healthy subjects executing constant-load 100 W and 150 W hindlimb exercises (protocol 1) or unloaded (0 W) cycling (protocol 2). Attention was focussed on early changes in variables during phase I of constant load exercise, a period where neurogenic afferents from working muscles play a key role in adaptative cardiorespiratory response as they did also during 0 W cycling. In protocol 1, a 15% O2 gas mixture was used while in protocol 2, 15% and 10% O2 mixtures were tested. Compared to the variations of cardiorespiratory variables measured during room air breathing (normoxia), hypoxemia significantly and markedly depressed the rates of VE and fR changes during phase I exercise but did not affect the changes in HR. Reduced phase I ventilatory response was not accompanied by significant variations in rest values of PaCO2 and pHa associated with the response to hypoxia. The cardiorespiratory response to 0 W cycling was also lowered under hypoxemic conditions, the magnitude of VE and HR changes being inversely proportional to the fall in PaO2 level. Based on electrophysiological animal observations, the present results may be interpreted in terms of inhibitory influences of hypoxemia on proprioceptive muscle afferents.

Acute Disease↗
PubMed1996

Cardiorespiratory response to progressive leg exercise under acute normobaric hypoxia.

There is no clear evidence that the cardiorespiratory response to progressive maximal leg exercise was affected in proportion to the fall in PaO2 as measured from arterialized ear lobe blood. Subjects inhaling room air (rest PaO2 = 81 +/- 1 mmHg) or hypoxic gas mixtures, containing 15% or 10% O2 in N2 (rest PaO2 = 60 +/- 3 and 45 +/- 1 mmHg, respectively), performed leg exercise until exhaustion above the ventilatory threshold, determined from the changes in the ventilatory equivalent for oxygen (VO2VEAT). Acute hypoxemia potentiated the increase in minute ventilation (VE) in response to exercise, but this effect was only found when VE changes were expressed in percent of data collected during the 0 W work load cycling period preceding exercise. Hypoxemia always potentiated the heart rate (HR) response to exercise. These effects of hypoxemia on VE and HR were not proportional to the fall in PaO2. In addition, severe hypoxemia depressed the pressor vascular response to exercise. By contrast, VO2max and VO2VEAT decreased in proportion to hypoxemia and VO2VEAT was also negatively correlated with the peak lactate concentration. It was concluded that severe hypoxemia attenuated the cardiorespiratory response to exercise, whereas its consequences on the metabolic components of exercise (VO2max, VO2VEAT, lactic acid production) seem proportional to the reduced muscle oxygen supply.

Adult↗
PubMed1996

Changes in airway resistance induced by nasal inhalation of cold dry, dry, or moist air in normal individuals.

Nasopulmonary bronchomotor reflexes elicited by mechanical or irritant stimulation of the nose have been described in animals and asthmatic patients. However, few studies were devoted to the consequences of nasal breathing of cold and dry air or of only dry or only moist air on the bronchomotor control in normal individuals. The present study reported changes in interruption resistance (Rint) measured during eupneic breathing of moderately cold (-4 or -10 degrees C) and dry [0.3% relative humidity (RH)] air or of room air at 23 degrees C that is either dry (0.3% RH) or moist (97% RH). Nasal inhalation of cold (-4 degrees C) dry air or of only dry air significantly increased baseline Rint value (17 and 21%, respectively) throughout the 15-min test periods. The response to cold was significantly accentuated when the air temperature was lowered to -10 degrees C (42%). After nasal anesthesia or inhalation of a cholinergic antagonist, cold air did not induce a change in Rint. Nasal inhalation of moist room air had no effect. No Rint changes were measured during oral breathing of the three test agents. It is concluded that the activation of cold receptors or osmoreceptors in the nasal mucosa induces protective bronchoconstrictor responses in normal individuals.

Administration, Inhalation↗
PubMed1995

Increasing background inspiratory resistance changes somatosensory sensations in healthy man.

The central purpose of the study was to investigate if increasing background inspiratory resistance, a circumstance which activated afferents from the lungs and respiratory muscles, modified somatosensory and/or auditory sensations in healthy individuals. Estimation of mechanical stimulations applied on the middle finger (somatosensory sensation) and unilateral sound-pressure stimulations (auditory sensation) was based on the computation of Stevens' power function psi = k.phi n, where psi is the estimate and phi is either the somatosensory stimuli or sound-pressures. This was studied during eupnoeic unloaded ventilation then during a 10-min period of loaded breathing followed by a 10-min recovery period. Loaded breathing significantly lowered the estimate of somatosensory stimuli (decreased n coefficient). This effect persisted during the two first minutes of recovery period. By contrast, loaded breathing did not modify the perception of auditory stimulus. As somesthetic and respiratory afferents, but not auditory afferents, project on the same area in the sensory cortex we suggest the existence of central interactions which could explain observations of the difficulties to execute accurate tasks in patients suffering from obstructive lung disease independently from the alterations in their arterial blood gases.

Acoustic Stimulation↗
PubMed1995

Maximal force and endurance to fatigue of respiratory and skeletal muscles in chronic hypoxemic patients: the effects of oxygen breathing.

The consequences of chronic hypoxemia on maximal force and endurance time to sustained 80% of maximal isometric contraction of two skeletal muscles (adductor pollicis and vastus lateralis) and the diaphragm were studied in patients with chronic obstructive pulmonary disease (COPD). Compared to normal subjects, COPD patients have lower values of Fmax for the two skeletal muscle groups and Pmax (diaphragm). Endurance time was also shorter for the diaphragm and adductor pollicis. Chronic hypoxemia was associated with an accentuation in integrated EMG changes in both low and high frequency bands for adductor pollicis and diaphragm. Inhalation of oxygen enriched gas mixture for a 15-min period increased markedly Fmax and PImax values, prolonged the endurance time to sustained thumb adduction, and reduced the EMG changes in the low frequency band for adductor pollicis. The present observations provide evidence for altered maximal performances of skeletal muscles in chronic hypoxemic patients and also point out the virtues of oxygen breathing in these patients.

Adult↗