Ventilatory parameters and maximal respiratory pressure changes with age in Duchenne muscular dystrophy patients.

The aim of this longitudinal study was to precise, in children with Duchenne muscular dystrophy, the respective functional interest of ventilatory parameters (Vital capacity, total lung capacity and forced expiratory volume in one second [FEV(1)]) in comparison to maximal inspiratory pressure (Pimax) during growth. In ten boys the mean age of 9.1 +/- 1 years) to mean age of 16 +/- 1.

[Respiratory function testing in infants: recommendations on normal values].

The present document is being produced on behalf of the French Society of the Physiology Task Force on standards for Infant Respiratory Function Testing whose aim is to provide guidelines for good laboratory practices according to the latest international recommendations. Application of such recommendations could be of particular value when attempting to develop standardized protocols in the scope of multi-centre trials. The first part resume these recommendations about apparatus, acquisition system and software for Infant Respiratory Function Testing.

L-arginine decreases inflammation and modulates the nuclear factor-kappaB/matrix metalloproteinase cascade in mdx muscle fibers.

Duchenne muscular dystrophy (DMD) is a lethal, X-linked disorder associated with dystrophin deficiency that results in chronic inflammation, sarcolemma damage, and severe skeletal muscle degeneration. Recently, the use of L-arginine, the substrate of nitric oxide synthase (nNOS), has been proposed as a pharmacological treatment to attenuate the dystrophic pattern of DMD. However, little is known about signaling events that occur in dystrophic muscle with l-arginine treatment.

Role of respiratory system impedance in the difference of ventilatory control between children and adults.

How children are able to adapt their ventilation to the intensity of exercise faster than adults remain unclear. We hypothesized that differences of VE observed between children and adults depend on either peripheral chemoreceptors or central command activity. We examined ventilatory control parameters in either normoxic or hypoxic condition (FI 02 =0.

Alteration of the piglet diaphragm contractility in vivo and its recovery after acute hypercapnia.

Background: The effects of hypercapnic acidosis on the diaphragm and its recovery to normocapnia have been poorly evaluated. The authors studied diaphragmatic contractility facing acute variations of arterial carbon dioxide tension (Paco2) and evaluated the contractile function at 60 min after normocapnia recovery.

Methods: Thirteen piglets weighing 15-20 kg were anesthetized, ventilated, and separated into two groups: a control group (n = 5) evaluated in normocapnia (time-control experiments) and a hypercapnia group (n = 8) in which animals were acutely and shortly exposed to five consecutive ranges of Paco2 (40, 50, 70, 90, and 110 mmHg).

Ventilation during air breathing and in response to hypercapnia in 5 and 16 month-old mdx and C57 mice.

Previous studies have shown a blunted ventilatory response to hypercapnia in mdx mice older than 7 months. We test the hypothesis that in the mdx mice ventilatory response changes with age, concomitantly with the increased functional impairment of the respiratory muscles. We thus studied the ventilatory response to CO(2) in 5 and 16 month-old mdx and C57BL10 mice (n = 8 for each group).

L-arginine improves dystrophic phenotype in mdx mice.

A possible treatment for Duchenne muscular dystrophies would be to compensate for dystrophin loss by increasing the expression of utrophin, another cytoskeletal protein of the muscle membrane. We previously found that L-arginine, the substrate for nitric oxide synthase, significantly increased utrophin level in muscle and targeted it to the sarcolemma. Here, we have addressed the expected benefit in the mdx mice.

Effect of inspiratory threshold loading on ventilatory kinetics during constant-load exercise.

Humoral factors play an important role in the control of exercise hyperpnea. The role of neuromechanical ventilatory factors, however, is still being investigated. We tested the hypothesis that the afferents of the thoracopulmonary system, and consequently of the neuromechanical ventilatory loop, have an influence on the kinetics of oxygen consumption (VO2), carbon dioxide output (VCO2), and ventilation (VE) during moderate intensity exercise.

Effects of short vs. prolonged mechanical ventilation on antioxidant systems in piglet diaphragm.

Objective: Prolonged controlled mechanical ventilation (MV) is known to induce diaphragmatic oxidative stress that seems to be an important factor reducing force-generating capacity. To better understand the cellular mechanisms involved, this work examined the effect of short vs. prolonged MV on antioxidant defense in the diaphragm.

Changes in respiratory muscle endurance during puberty.

The evaluation of respiratory muscle endurance provides clinically useful information on muscle function, especially in children with respiratory and neuromuscular diseases. However, endurance may be lower in young children than in older children because of the major physical changes of puberty. We thus compared respiratory muscle endurance in 15 healthy pre- and peripubertal children (S1-S2/P1 group) and 14 healthy children near the end of the pubertal process (S4P4 group).

The effect of respiratory muscle training with CO2 breathing on cellular adaptation of mdx mouse diaphragm.

The aim of our study was to investigate the cellular mechanisms induced by hypercapnic stimulation of ventilation, during 6 weeks/30 min per day, in 10 mdx and 8 C57BL10 mice (10+/-0.2 months old). Ten mdx and eight C57BL10 mice served as control group.

[Maximal respiratory pressures in children: the methodological challenge].

Introduction: Measurement of maximal respiratory pressures against an occlusion has been used for a long time to assess respiratory muscle strength in the follow up of children with respiratory disease. In the early stage of disease this is the main test for diagnosing respiratory muscle involvement and the degree of that involvement. STATE OF KNOWLEDGES: The interpretation of the results is difficult on account of variability of the measurements and of the reference values.

[Ventilatory response to maximal exercise in healthy children].

Introduction: The evaluation of the ventilatory response of children during exercise is essential to determine its role in impaired exercise tolerance. The aim of this review is to describe the variables and the values of maximal ventilatory parameters observed in healthy children in the published literature.

State Of Art: The maximal ventilation (VEmax) and the tidal volume (VTmax) increase in a linear fashion with age and plateau in boys at 15 years, and in girls at 13 years.

Gender influence on the oxygen consumption of the respiratory muscles in young and older healthy individuals.

To understand the influence of gender on oxygen consumption of respiratory muscles (VO(2)resp), 32 healthy subjects participated in the study (16 males, 16 females). They were divided into four groups: young males, young females, older males and older females. We used a closed circuit device which allowed a continuous increase in external dead space at a constant rate of 300 ml per 90 s and was equipped with a 9-L Gould spirometer filled with 100 % O(2).

Respiratory pressures in boys from 11-17 years old: a semilongitudinal study.

We hypothesized that in children, maximal respiratory pressures increase with age and more during the pubertal growth spurt. The aim of this work was to follow maximal respiratory pressures, with a semilongitudinal study, in three groups of prepubertal, peripubertal, and postpubertal children in order to specify pressure changes with age and determine the contributions of growth and puberty. A semilongitudinal study was conducted in 44 boys assigned to three overlapping age groups: from 11-13 (prepubertal stage), from 13-15 (pubertal stage), and from 15-17 years (postpubertal stage).

Effect of food restriction on lactate sarcolemmal transport.

The objective of this study was to investigate the effects of 6 weeks of food restriction (FR) on sarcolemmal lactate transport in rats. The daily food consumption of rats was monitored for 10 days, after which they were assigned to either a control group (CTL, n = 7) that consumed food ad libitum or an FR group (n = 7) that received a daily ration equal to 60% of their predetermined baseline food intake. After the 6-week period, we observed in red gastrocnemius (RG) a fall of 48% in glycogen content (P <.

Addition of inspiratory resistance increases the amplitude of the slow component of O2 uptake kinetics.

The contribution of respiratory muscle work to the development of the O(2) consumption (Vo(2)) slow component is a point of controversy because it has been shown that the increased ventilation in hypoxia is not associated with a concomitant increase in Vo(2) slow component. The first purpose of this study was thus to test the hypothesis of a direct relationship between respiratory muscle work and Vo(2) slow component by manipulating inspiratory resistance. Because the conditions for a Vo(2) slow component specific to respiratory muscle can be reached during intense exercise, the second purpose was to determine whether respiratory muscles behave like limb muscles during heavy exercise.

The effects of prior cycling and a successive run on respiratory muscle performance in triathletes.

The aim of the present study was to compare the effects of prior cycling and a successive run on respiratory muscle performance during a cycle-run succession as performed in the triathlon. We hypothesized that despite the moderate intensity of exercise and the absence of exhaustion, the crouched cycling position would induce a decrease in respiratory muscle performance that would be reversed by the successive vertical run position. Ten male triathletes (22.

Electrophysiologic changes during exercise testing in patients with chronic obstructive pulmonary disease.

To determine whether skeletal muscle is involved in the exercise limitation of chronic obstructive pulmonary disease (COPD), we investigated electrical adaptations in muscle during incremental cycling exercise testing. Changes in quadriceps activity were compared using surface electromyography (SEMG) and motor point stimulation in ten COPD patients and ten healthy subjects. Patients showed significantly lower exercise capacity, and M-wave duration was increased from exercise onset (P < 0.

Effects of controlled mechanical ventilation on respiratory muscle contractile properties in rabbits.

Objective: We examined in rabbits the effects of more than 48 h of mechanical ventilation on the contractile properties and fiber type adaptations of the respiratory muscles.

Design And Setting: Experimental prospective study in a university laboratory.

Animals And Interventions: Nineteen rabbits were randomly allocated to two groups: control (n=10) or mechanically ventilated (MV; n=9) for 51+/-3 h.

Post-extubation stridor in intensive care unit patients. Risk factors evaluation and importance of the cuff-leak test.

Objective: To evaluate the incidence and identify factors associated with the occurrence of post-extubation stridor and to evaluate the performance of the cuff-leak test in detecting this complication.

Design: Prospective, clinical investigation.

Setting: Intensive care unit of a university hospital.

Comparison of the effects of heat and moisture exchangers and heated humidifiers on ventilation and gas exchange during non-invasive ventilation.

Objective: To compare the short-term effects of a heat and moisture exchanger (HME) and a heated humidifier (HH) during non-invasive ventilation (NIV).

Design: Prospective, clinical investigation.

Setting: Intensive care unit of a university hospital.

The effect of cycling followed by running on respiratory muscle performance in elite and competition triathletes.

This study investigated the possibility of there being differences in respiratory muscle strength and endurance in elite and competition triathletes who have similar maximal oxygen uptakes (VO(2max)) and ventilatory thresholds (Th(vent)). Five internationally-ranked elite, [mean (SD) age 23.8 (1.

Dose-dependent effect of individualized respiratory muscle training in children with Duchenne muscular dystrophy.

The aim of this study was to evaluate the effects of low intensity, home inspiratory muscle training on respiratory muscle endurance in children with Duchenne muscular dystrophy, using a double-blind protocol. The originality aspect of this study is the use of a reproducible method of endurance and of the same method for evaluation and training. We studied eight trained children (mean age 14.