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Biomedical subjects

G Benchetrit

Publications and source records attributed to G Benchetrit.

At least 19 recordsLinked to original sources
PubMed1999

Breathing pattern in patients with Parkinson's disease.

The improvement in motor performance resulting from levodopa administration in patients with Parkinson's disease (PD) provides the opportunity to investigate ventilatory changes brought about by the disease. The aim of this study has been to investigate these changes in order to specify the mechanisms of the impairment in breathing in PD. Breathing patterns at rest were investigated in 11 patients with idiopathic PD both before (OFF) and after (ON) administration of levodopa at a dose improving their motor performance by at least 30%. Airflow (Fleisch head mounted on a mask), rib cage and abdomen movements (inductance plethysmography) were recorded in the OFF condition 1 h after subjects woke up. Subjects then received levodopa and a new set of recordings was obtained 1 h later, in the ON condition. Breath-by-breath processing of recordings was carried out, and tidal volume (VT), inspiratory (TI) and expiratory (TE) durations were measured. The main finding was a lengthening of TI resulting in a decrease in ventilation and in VT/TI, and an increase in TI/TTOT in the ON compared to the OFF condition. In the ON condition abnormal rib cage-abdomen plots patterns were found in four out of six subjects. A hypothesis on the effect of PD on breathing is proposed on grounds of normal diaphragmatic activity but impaired activity of the other respiratory muscles and more specifically the intercostal muscles.

Aged↗
PubMed1999

New statistical method for detection and quantification of respiratory sinus arrhythmia.

A statistical method with the advantages of 1) enabling graphical representation of within-respiratory cycle heart rate variations, 2) detecting the presence of respiratory sinus arrhythmia (RSA) in a moving window, and 3) providing breath-by-breath RSA amplitude and phase obtained from the fitting of a sinusoid to the instantaneous relative heart rate is presented.

Adolescent↗
PubMed1998

Effects of resistive loading on the pattern of breathing.

In order to determine changes in breathing patterns brought about by resistive loading, ventilation was recorded in 11 healthy subjects with four linear resistances (3.57, 5.75, 8.76 and 13.13 cmH2O L(-1) sec) added in a random order throughout the entire breath. At steady state, a breath-by-breath analysis of airflow was used to quantify the pattern of breathing in terms of respiratory variables: TI, TE, Tt, VT, VT/TI, TI/Tt, and by taking TI, TE, VT all together (TRIAD) and also the shape of the entire airflow profile quantified by harmonic analysis (ASTER). Group analysis using ANOVA showed significant changes in all variables. There were increasing changes with increasing loads in all variables, the smallest changes being in TI/Tt. Within to between-individual comparisons between two loads showed that only TI/Tt and the ASTER were more similar within than between-individuals for all comparisons. It was concluded that at steady state mechanisms of load compensation come into play inducing changes in the pattern of breathing proportional to the loads while maintaining some of the individual characteristics.

Adaptation, Physiological↗
PubMed1998

Blood flow vs. venous pressure effects on filtration coefficient in oleic acid-injured lung.

On the basis of changes in capillary filtration coefficient (Kfc) in 24 rabbit lungs, we determined whether elevations in pulmonary venous pressure (Ppv) or blood flow (BF) produced differences in filtration surface area in oleic acid-injured (OA) or control (Con) lungs. Lungs were cyclically ventilated and perfused under zone 3 conditions by using blood and 5% albumin with no pharmacological modulation of vascular tone. Pulmonary arterial, venous, and capillary pressures were measured by using arterial, venous, and double occlusion. Before and during each Kfc-measurement maneuver, microvascular/total vascular compliance was measured by using venous occlusion. Kfc was measured before and 30 min after injury, by using a Ppv elevation of 7 cmH2O or a BF elevation from 1 to 2 l . min-1 . 100 g-1 to obtain a similar double occlusion pressure. Pulmonary arterial pressure increased more with BF than with Ppv in both Con and OA lungs [29 +/- 2 vs. 19 +/- 0.7 (means +/- SE) cmH2O; P < 0. 001]. In OA lungs compared with Con lungs, values of Kfc (200 +/- 40 vs. 83 +/- 14%, respectively; P < 0.01) and microvascular/total vascular compliance ratio (86 +/- 4 vs. 68 +/- 5%, respectively; P < 0.01) increased more with BF than with Ppv. In conclusion, for a given OA-induced increase in hydraulic conductivity, BF elevation increased filtration surface area more than did Ppv elevation. The steep pulmonary pressure profile induced by increased BF could result in the recruitment of injured capillaries and could also shift downstream the compression point of blind (zone 1) and open injured vessels (zone 2).

Animals↗
PubMed1998

In vivo quantitation of epithelial lining fluid in dog lung.

We used an original saturation bronchoalveolar lavage (SBAL) technique (Eur. Respir. J. 1995;8[Suppl. 19]398S) to quantitate lung epithelial lining fluid volume (VELF) in dogs in two separate experiments: control and after oleic-acid-induced injury. We confirmed the hypothesis that 99mTc-DTPA, infused at constant plasma activity, reaches equilibrium with epithelial lining fluid after 90 min. We performed eight sequential lavages 215 min after beginning the infusion of 99mTc-DTPA. 99mTc-DTPA activity (Qn) in the lavage fluid increased linearly with time, suggesting transport from the plasma into the alveoli during lavage. We extrapolated Qn to time zero (Q0), when 99mTc-DTPA was not affected by lavage. VELF was calculated from: VELF = Q0/Cp, (Cp: 99mTc-DTPA mean plasma activity). 125I-albumin was used as a nondiffusible alveolar indicator to measure the fluid volume present in the lavaged segment (Vt,n). Vt,n plateaud for n >= 4. VELF/Vt,n(n = 5,8) was 1.7 +/- 0.4 and 25.0 +/- 4.4% (p < 0.05) in control and injury experiments, respectively. SBAL allowed reliable measurements of VELF and detection of alveolar edema fluid in the injured lung.

Albumins↗
PubMed1997

Chlorine gas induced acute lung injury in isolated rabbit lung.

This study was designed to investigate the pathogenesis of chlorine gas (Cl2) induced acute lung injury and oedema. Isolated blood-perfused rabbit lungs were ventilated either with air (n=7) or air plus 500 parts per million (ppm) of Cl2 (n=7) for 10 min. Capillary pressure, measured by analysing the pressure/time transients of pulmonary arterial, venous and double (both arterial and venous) occlusions, was unchanged in both groups. In Cl2-exposed lungs, the fluid filtration rate increased from -0.228+/-0.25 to 1.823+/-1.23 mL min(-1) x 100 g(-1) (p<0.001) and the filtration coefficient increased from 0.091+/-0.01 to 0.259+/-0.07 mL x min(-1) x cmH2O(-1) x 100 g(-1) (p<0.001). No changes were observed in the control lungs. The extravascular lung water/blood-free dry weight ratio was 8.6+/-1.6 in the Cl2 group and 4.0+/-0.5 in the control group (p<0.001), confirming that the increase in lung weight was related to accumulation of extravascular fluid. Although the alveolar flooding by oedema is explained, in part, by the Cl2-induced epithelial injury, our results suggest that Cl2 exposure induces acute lung injury and oedema due to an increased microvascular permeability.

Animals↗
PubMed1997

Evaluation of respiratory inductive plethysmography: accuracy for analysis of respiratory waveforms.

OBJECTIVE: To assess the accuracy of respiratory inductive plethysmography (RIP) waveforms to those obtained with whole body plethysmograph (BP) as this device gives a plethysmographic signal and a pneumotachograph (PNT). DESIGN: Randomized controlled trial. SETTING: Physiologic laboratory in a university hospital. PARTICIPANTS: Eleven subjects from the laboratory staff. INTERVENTIONS: This study was achieved during four consecutive periods in subjects breathing spontaneously and through different added resistive loads. Using the least square method calibration, two RIP waveforms, VRIP.BP(t) and VRIP.PNT(t), were simultaneously calculated with coefficients obtained from BP and from PNT volume waveforms, respectively VBP(t) and VPNT(t). For each recording, to compare volume waveforms, we calculated their differences in term of distances, DRIP-BP and DRIP-PNT, between the normalized RIP volume signal (respectively, VRIP.BP[t] and VRIP.PNT[t]) and its normalized reference (respectively, VBP[t] and VPNT[t]). We also calculated the distance DPNT-BP between the two normalized references VBP(t) and VPNT(t). RESULTS: No significant effect of load or time on the distance occurred. Including all the recordings, the mean distance DRIP-BP (3.4+/-1.1%) appears significantly lower than both the mean distance DRIP-PNT (4.5+/-1.3%; p<0.04) and the mean distance DPNT-BP (4.6+/-0.9%; p<0.008). For each period or load level, DRIP-BP appears to be lower than DRIP-PNT and DPNT-BP. CONCLUSION: The RIP seems reasonably accurate for analysis of respiratory waveform while subjects subsequently breathe against resistive loads.

Adult↗
PubMed1996

The effects of breathing pattern training on ventilatory function in patients with COPD.

The purpose of this study was to assess the effects of a particular breathing pattern training (BPT) on forced expiratory volume during the first second (FEV1) and forced vital capacity (FVC) in patients with chronic obstructive pulmonary disease (COPD). The subjects adjusted each breath to a target breath displayed on a video screen, by using visual feedback. This target was chosen in an individual sample recorded at rest. We used a randomized, controlled group design. Twenty patients with stable COPD, FEV1 less than 1.5 liters, undergoing a traditional rehabilitation program were randomly assigned to the BPT group or to the control group. Each BPT subject underwent 30-35 training sessions spread out over four weeks, in addition to the traditional program. FEV1 and FVC were performed before and after this program. ANOVAs showed that FEV1 and FVC significantly improved in BPT subjects, with a mean percent increase of 22% and 19%, respectively. Corresponding changes in controls were not significant. This study showed short-term increases in FEV1 and FVC in COPD patients practicing BPT in addition to respiratory rehabilitation, in comparison with controls. Further studies should incorporate outcome data to clarify the mechanisms and the duration of this effect.

Aged↗
PubMed1996

Voluntary control of breathing pattern in asthmatic children.

15 asthmatic children and 15 healthy children were trained to adjust their breathing pattern to a target pattern displayed on a video screen by using visual feedback. The error scores in the two groups were not significantly different. These data did not support the hypothesis that voluntary control of respiratory muscles is impaired in asthmatics.

Asthma↗
PubMed1995

Is voluntary control of breathing impaired in patients with chronic obstructive pulmonary disease?

1. To assess whether voluntary control of breathing is impaired in patients with chronic obstructive pulmonary disease, a group of such patients performed a tracking task, requiring volitional control of respiratory muscles. 2. Eight patients (mean age 60 years; mean ratio of forced expiratory volume in 1 s to forced vital capacity = 31%) took part in the study. Five of the seven patients in whom blood gas measurements were made were mildly hypoxaemic (PaO2 = 53-71 mmHg), and one of these was hypercapnic (PaCO2 = 55 mmHg). Each subject performed a compensatory ventilatory tracking task using a tracking system which comprised a fixed target displayed on a monitor screen and a cursor moving in a line bisecting the target. The position of the cursor was perturbed by a forcing function and patients were required to keep the cursor on the target by breathing in and out of a spirometer. 3. To allow for any non-specific deficiency in motor control, patients performed a similar manual tracking task, using their dominant arm to move a joystick. As a control group, 11 healthy subjects (mean age 58 years; mean ratio of forced expiratory volume in 1 s to forced vital capacity = 77%) underwent an identical experimental protocol. 4. Motor control performances were measured in terms of the error between the target position and the subject's positioning of the cursor. Indices of performance were the root mean square of the error and the averages of the zero errors (i.e. end expiration/arm movement towards the trunk) and the peak errors (i.e. end inspiration/arm movement from the trunk).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Performance and learning during voluntary control of breath patterns.

Fourteen subjects learned to adjust their breath pattern to two target breaths displayed on a video screen, by using visual feedback, during two sessions 24 h apart. These two targets were respectively the smallest and the largest breaths of a ten-breath sample previously recorded from each subject's resting spontaneous breathing. Performances were significantly better for the large than for the small target breath. This cannot be directly inferred from current knowledge related to the control of movement time and amplitude, but rather it may be inferred from the periodic character of breathing, to the higher mental load during the small breath task, or to the presumably different frequencies of target breaths in the whole span of spontaneous breathing. In the second session, performance on the two targets levelled out as a result of learning.

Adult↗
PubMed1993

Entrainment of the respiratory rhythm: a new approach.

When we periodically perturbed the central respiratory oscillator with a controlled periodic stimulation provided by a mechanical ventilator, an entrainment phenomenon occurred: the actual rhythm of the respiratory centres was phase locked to the periodic stimulation. In some experiments, we observed an intermittence phenomenon: the respiratory rhythm successively seemed entrained, departed from this mode for few cycles, returned to the previous pseudo entrainment and so on. From intermittence data, we were able to plot a phase response curve. From literature data on the effects of a single stimulation applied at various moments in the respiratory cycle, we built up a mathematical model designed to simulate entrainment experiments. This model simulated entrainment phenomenon, but did not satisfactorily accommodate the experimental phase response curve. The section of the simulated phase response curve responsible for discrepancies was the result of the combination of an inspiratory shortening owing to a stimulation occurring during inspiration, and a positive relationship between inspiratory duration TI and expiratory duration TE. We changed the TE-TI relationship, assuming that the expiratory duration is determined not by the inspiratory duration but rather by the lung volume at the end of inspiration. The revised model was then able to exhibit almost all the qualitative properties previously noted in experiments. The significance in biological terms of the new TE-TI relationship, which is apparently incompatible with almost all previous experimental data, is discussed.

Animals↗
PubMed1993

Breathing patterns of monozygous twins during behavioural tasks.

To better understand behavioural and genetic influences upon breathing, the breathing patterns of 8 pairs of monozygous (MZ) twins were measured under 4 behavioural conditions; relaxed without standardisation; eyes closed; eyes open; and reading. Breathing was quantified by inspiratory and expiratory durations (TI, TE), tidal volume (VT) and derived variables. Airflow shape was normalised and quantified using 8 dimensions. Reading caused breathing to increase by > 500 ml/min compared to the other four conditions. Differences in breathing between combinations of two conditions were compared by testing whether the differences within an individual were smaller than the differences between random pairs of individuals from the same 16 subjects. For almost all respiratory variables, and whatever the behavioural condition, there were highly significant similarities within an individual (p < 0.00025 on 32/80 comparisons). Under each condition, the differences within MZ twin-pairs were compared to the differences within random-pairs from the same subject population. There were highly significant similarities within twin-pairs for the airflow shape across all conditions. However, TI, TE and VT failed to consistently show significant similarities within twin pairs. Hence, an individual's airflow shape appears to be a fundamental characteristic which is conserved when behavioural condition and level of ventilation changes. Further, MZ twins have similar airflow shapes--whatever the behavioural situation. Hence, behavioural influences upon airflow shape act upon monozygous twin pairs in similar ways, or such influences were negligible under the conditions of the present study.

Adolescent↗
PubMed1992

Entrainment of respiratory rhythm by periodic lung inflation: effect of airflow rate and duration.

In anesthesized, paralyzed, and mechanically ventilated rabbits, the rate and duration of airflow were varied to investigate the effect on the central respiratory rhythm during 1:1 entrainment (1 phrenic nerve burst for 1 pump inflation). Our results showed that 1) the largest range of 1:1 entrainment was obtained with the longest inflation durations associated with the lowest flow rates and 2) both inspiratory (TI) and expiratory (TE) durations (as estimated by the period of phrenic nerve activity and phrenic nerve silence, respectively) increased when total respiratory duration (TT = TI+TE) increased. The phase relationships we studied were DI (the time elapsing between the onset of phrenic activity and the beginning of pump inflation) and DE (the time between the end of phrenic activity and the end of pump inflation). Both DI and DE increased when the total ventilatory period increased. However, for constant ventilatory period, DI changed with the rate and duration of airflow, whereas DE remained constant. In addition, under these conditions, TI, TE, and the integrated phrenic nerve activity remained constant independently of airflow rate and duration. The present results are discussed with regard to the pulmonary receptors (slowly and rapidly adapting receptors and C fibers) that are stimulated during mechanical ventilation, and hypotheses are drawn regarding their possible contribution to rhythm generation and the mechanism through which they may act.

Animals↗
PubMed1992

Individuality of breathing patterns during hypoxia and exercise.

Breathing was recorded via a pulsed ultrasonic flowmeter in 11 healthy subjects, at rest and during steady-state exercise (at 50% of their maximal O2 consumption) at both sea level (200 m) and simulated altitude (4,500 m in a hypobaric chamber). The pattern of breathing was quantified breath by breath in terms of classical respiratory variables (tidal volume and inspiratory and expiratory times), and the shape of the entire airflow profile was quantified by harmonic analysis. Statistical tests were used to compare the within-individual with the between-individual variations. In comparing the sea level vs. altitude rest (16% increase in ventilation) and sea level vs. altitude exercise (40% increase in ventilation) airflow profiles, we found a significantly greater resemblance within the individual than between individuals. Comparisons of sea level rest and exercise (295% increase in ventilation) and altitude rest and exercise (375% increase in ventilation) revealed no similarity within individuals. Despite airflow profile changes between rest and exercise, it is still possible to attest to a diversity of flow profile between individuals during exercise. Hypoxia at rest or during exercise does not alter the phenomenon of the individuality of breathing patterns.

Adult↗
PubMed1992

[Selective laryngeal re-innervations in the dog by nervous microsutures of branches of the recurrent laryngeal nerve].

INTRODUCTION: This work has been carried out to investigate in an animal model, the possibility of surgical selective reinnervation of the larynx following destruction of the laryngeal branch of the vagus nerve. MATERIAL AND METHODS: In ten dogs, on the right side of the neck only, the recurrent laryngeal nerve was identified, cut and section of the nerve removed. Following this the hemi-larynx on the operated side was reinnervated in the following manner. Using a microsurgical suture (described in the text) the motor nerves from extra-laryngeal muscles were anastomosed onto the nerves supplying the intrinsic abductors and adductors of the larynx. The nerve to sterno-thyroid was anastomosed onto the nerve supplying the posterior crico-arytenoid muscle (vocal cord abductor). Similarly the nerve supplying thyrohyoid was anastomosed onto the cut distal end of the adductor division of the recurrent laryngeal nerve. Clinical, electromyographical and histological evaluations have been used to prove the reinnervation. RESULTS: In the nine surviving animals successful re-innervations, as defined by the return of normal function, has been achieved for posterior crico-arytenoid and 7 adductor muscles. CONCLUSION: This study has demonstrated the feasibility of laryngeal reinnervation after surgical section of the recurrent laryngeal nerve, and give some cause for optimism for its ultimate application in man.

Anastomosis, Surgical↗
PubMed1991

Mechanisms of pulmonary edema induced by an organophosphorus compound in anesthetized dogs.

To determine the mechanism governing pulmonary edema induced by an organophosphorus compound, S-(2-diisopropylaminoethyl)-O-ethylmethyl phosphonothiolate (VX), lung lymph flow and lymph-to-plasma protein concentration ratio were measured in six anesthetized, open-chest, mechanically ventilated beagle dogs before and after intravenous injection of 6 micrograms/kg of VX. Systemic and pulmonary hemodynamic data (heart rate, aortic blood flow, and left atrial, systemic arterial, pulmonary arterial, and pulmonary capillary pressures) were continuously recorded. Arterial blood gases and pH were measured every 30 min. Histological examinations and lung water content measurements were also carried out. Following VX injection, lung lymph flow increased (from 109 +/- 38 to 179 +/- 66 microliters/min, p less than 0.05) while lymph-to-plasma protein concentration ratio remained unchanged (from 0.64 +/- 0.14 to 0.62 +/- 0.12, N.S.). Neither systemic nor pulmonary hemodynamics were changed. Lung water content expressed as blood-free wet-to-dry weight ratio increased from 4.31 +/- 0.23 to 5.35 +/- 0.26 (p less than 0.05). Histological examinations revealed in many cases diffuse congestion of lungs and interstitial edema. These results suggest that VX injection induces an increase in pulmonary capillary permeability which may lead to a high-permeability edema.

Acetylcholinesterase↗