Biomedical subjects

M Ramonatxo

Publications and source records attributed to M Ramonatxo.

At least 37 records · Page 2Linked to original sources

PubMed1998

Ventilation response to CO2 and exercise-induced hypoxaemia in master athletes.

Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyperpnoea. The aim of this study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation of the central chemoreceptors. The ventilation response to CO2 was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7 (SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, VO2max), and during strenuous exercise (70% VO2max) using the rebreathing method. Our results showed that the ventilation response to CO2 did not differ with endurance training and/or exercise, that the threshold of the CO2 response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [deltaTh(0-40): 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that deltaTh(0-40) and Th during moderate exercise were negatively correlated with arterial O2 saturation during maximal exercise (r=0.50, P<O0.05). We concluded therefore that exercise-induced hypoxaemia in master athletes may not be due to a lower ventilation response to CO2, but may be partly related to a greater increase in Th during moderate exercise.

Aged↗

PubMed1998

Tension-time index of inspiratory muscles in COPD patients: role of airway obstruction.

Inspiratory muscle function has been shown to be related to general muscle weakness, weight loss, blood gas tensions, airway obstruction and hyperinflation. The aim of this study was to define (1) the factor that is the main determinant of the tension-time index of the inspiratory muscles (TTmus), and which this increases the risk of inspiratory muscle fatigue; and (2) whether a breathing strategy is adopted to avoid inspiratory muscle fatigue. Twenty-seven normal volunteers and 35 stable COPD outpatients (FEV1% predicted, range: 21-89%; and FRC/TLC, range: 49-77%) were studied. The TTmus was determined as follows: TTmus = PI/PImax.TI/Ttot, where Pi is the mean inspiratory pressure calculated from the mouth occlusion pressure (P0.1), PImax is the maximal inspiratory pressure, TI is the inspiratory time, and Ttot is the total time of the breathing cycle. COPD patients showed significantly lower PImax and higher P0.1, PI, PI/PImax, and TTmus than normal subjects. No patient had a TTmus value higher than the inspiratory muscle fatigue threshold of 0.33. The FEV1 was significantly correlated with TTmus and all its components in the patients. The FRC/TLC was also correlated with all components except PI. Body weight was only correlated with PImax. In a forward and backward stepwise regression analysis, FEV1 appeared to be the only significant factor explaining the variance of log (PI/PImax) and log (TTmus), whereas FRC/TLC was the principal determinant of PImax. In COPD patients, a non-linear relationship was found between TI and P0.1. A negative linear relationship was found between TI/Ttot and PI/PImax. In conclusion, although hyperinflation predominantly affected inspiratory muscle strength in a group of stable COPD patients with a wide range of severity, airway obstruction was the principal factor determining the magnitude of TTmus. In addition, in order to remain below the inspiratory muscle fatigue threshold, as the severity of airway obstruction increased, patients adopted a breathing strategy characterized by decreased TI/Ttot as inspiratory pressure demand increased.

Adaptation, Physiological↗

PubMed1998

Non-invasive assessment of inspiratory muscle performance during exercise in patients with chronic heart failure.

AIMS: The aim of this study was to assess inspiratory performance at rest and during exercise in patients with chronic heart failure in comparison with healthy controls using a non-invasive index: the tension-time index of inspiratory muscles (TTMUS). METHODS: We studied 13 patients with chronic heart failure (57 +/- 7 years) and 10 control subjects (58 +/- 6 years) at rest and during an incremental maximal exercise test. Measurements included breathing pattern (inspiratory time, total time of respiratory cycle, minute ventilation, tidal volume and respiratory frequency), mouth occlusion pressure and mean inspiratory pressure (calculated as follows: 5 x mouth occlusion pressure x inspiratory time). The maximal inspiratory pressure was measured at rest. TTMUS was calculated from the equation: TTMUS = PI/PIMAX x TI/TTOT, where PI/PIMAX is the ratio of mean inspiratory pressure to maximal inspiratory pressure and TI/TTOT is the ratio of mean inspiratory time to total time of the respiratory cycle. RESULTS: At rest, the results in patients showed non-significantly higher mouth occlusion pressure, lower maximal inspiratory pressure (P < 0.001), and a higher ratio of mean inspiratory pressure to maximal inspiratory pressure (P < 0.01). There was no difference in the breathing pattern. TTMUS was thus significantly higher in the patients with chronic heart failure (P < 0.001). At maximal exercise (77 +/- 16 W for patients with chronic heart failure vs 142 +/- 27 W for controls, P < 0.001), the ratio of mean inspiratory time to total time of respiratory cycle, the mouth occlusion pressure and the ratio of mean inspiratory pressure to maximal inspiratory pressure were not different. TTMUS was thus comparable in the two groups. During exercise, at comparable workloads (20, 40 and 60 W), the patients showed higher mouth occlusion pressure (P < 0.01) and a higher ratio of mean inspiratory pressure to maximal inspiratory pressure (P < 0.001), whereas the ratio of mean inspiratory time to total time of the respiratory cycle was similar. TTMUS was thus higher in the patients at each workload (P < 0.05). CONCLUSION: This study shows that the determination of TTMUS at rest and during exercise allows the observation of alterations in inspiratory muscle performance as a result of both reduced inspiratory strength, as measured by the maximal inspiratory pressure, and increased ventilatory drive, as reflected by the mouth occlusion pressure in patients with chronic heart failure. The non-invasiveness of this new index is an additional argument for its use in a clinical setting.

Adult↗

PubMed1998

Changes in breathing pattern and respiratory muscle performance parameters during difficult weaning.

OBJECTIVE: This study examined, using noninvasive means, the changes in breathing pattern and inspiratory muscle pressure-time indices during difficult progressive withdrawal of pressure-support ventilation. DESIGN: A prospective analysis of the temporal evolution of several respiratory variables in difficult-to-wean patients. SETTING: A university hospital intensive care unit. PATIENTS: A heterogeneous group of 17 patients receiving prolonged mechanical ventilation. INTERVENTIONS: Daily measurements of breathing pattern and respiratory muscle performance parameters in difficult-to-wean patients. MEASUREMENTS AND MAIN RESULTS: We examined breathing pattern variables, rapid shallow breathing (respiratory rate/tidal volume), tracheal occlusion pressure, maximal inspiratory pressure (P(I)max), and the tension-time index of the inspiratory muscles (TTmus = P(I)/P(I)max x Ti/Ttot) (where Ti/Ttot is inspiratory fraction of the cycle). All measurements were repeated at 24-hr intervals throughout the difficult weaning period. The patients were extubated on satisfying ten of 12 classical weaning criteria. Eleven patients were successfully weaned from mechanical ventilation while six patients were not. Weaning failure was associated with the following: a) longer periods of mechanical ventilation before weaning; b) high values of tracheal occlusion pressure, respiratory rate, minute ventilation, and effective impedance maintained throughout the difficult weaning period; and c) persistent high PaCO2 and intrinsic positive end-expiratory pressure values. As the weaning failure patients' inspiratory muscles confronted an increasing inspiratory load, values of the tension-time index of the inspiratory muscles entered or remained in the fatigue zone. In contrast, weaning success patients normalized their breathing pattern and decreased their tracheal occlusion pressure, effective impedance, and tension-time index values. CONCLUSIONS: Breathing pattern alterations and respiratory muscle performance impairments lead to ventilator dependency after prolonged mechanical ventilation. The measurement of variables such as the noninvasive tracheal occlusion pressure, inspiratory power of breathing, and tension-time index of the inspiratory muscles facilitate the management of difficult-to-wean patients.

Aged↗

PubMed1997

Determinants of the tension-time index of inspiratory muscles in children with cystic fibrosis.

Nutritional status and chronic pulmonary hyperinflation can alter respiratory muscle function in cystic fibrosis (CF). This study investigated: 1) whether inspiratory muscle function is reduced in children with stable CF in comparison with healthy controls; and 2) the mechanisms leading to inspiratory muscle weakness, which probably predispose to respiratory muscle fatigue. We determined the tension-time index of the inspiratory muscles (TTMUS) noninvasively at rest in 16 children with mild to moderate CF (mean age, 11 +/- 2 years) and 10 healthy controls (mean age, 11 +/- 2 years). The TTMUS was determined as follows: TTMUS = TI/TTOT.PI/PIMAX, where PI is the mean inspiratory pressure estimated from the measure of mouth occlusion pressure (P0.1), PIMAX is the maximal inspiratory pressure, and TI/TOT is the duty cycle. The results showed similar nutritional status in both groups, as well as mild to moderate airway obstruction, hyperinflation, and trapped gas in the CF group. In this group only, a significant inverse relationship was found between TI/TOT and PI/PIMAX[TITTOT = 0.482 - (0.388PI/PIMAX), r = -0.53; p < 0.05]. These patients also had greater TTMUS (TTMUS = 0.087 +/- 0.030 in CF vs. 0.056 +/- 0.014 in controls, P < 0.01) that increased with decreasing lean body mass (r = -0.70, P < 0.005), with increasing percent predicted functional residual capacity (r = 0.70, P < 0.05), and increasing volumes of trapped gas (r = 0.77, P < 0.01). The multiple linear regression analysis for these factors was significant (R2 = 0.84, P < 0.01); however, the partial regression coefficient was significant only for lean body mass (r2 = 0.60, P < 0.05). Therefore, muscle mass appeared as the strongest determinant of TTMUS in CF. This study used a noninvasive method to assess the inspiratory muscle performance in children with CF. The results suggest impairment in inspiratory muscle function in these children despite good nutritional status and only mild to moderate alteration in pulmonary function tests. In addition, we were able to investigate some of the determinants of inspiratory muscle weakness, namely, muscle mass, hyperinflation, and trapped gas, and found that muscle mass played a predominant role.

Body Mass Index↗

PubMed1997

Non-invasive quantification of diaphragm kinetics using m-mode sonography.

PURPOSE: The standard conditions of spirometry (i.e., wearing a noseclip and breathing through a mouthpiece and a pneumotachograph) are likely to alter the ventilatory pattern. We used "time motion" mode (M-mode) sonography to assess the changes in diaphragm kinetics induced by spirometry during quiet breathing. METHODS: An M-mode sonographic study of the right diaphragm was performed before and during standard spirometry in eight patients without respiratory disease (age 34 to 68 yr). RESULTS: During spirometry, the diaphragm inspiratory amplitude (DIA) increased from 1.34 +/- 0.18 cm to 1.80 +/- 0.18 cm (P = 0.007), whereas the diaphragmatic inspiratory (T1 diaph) increased from 1.27 +/- 0.15 to 1.53 +/- 0.23 sec, (P = 0.015, without change in diaphragmatic total time interval (Ttot diaph). Therefore, the diaphragm duty cycle (T1 diaph/Ttot diaph) increased from 38% +/- 1% to 44% +/- 4% (P = 0.023). The diaphragm inspiratory (DIV) and expiratory (DEV) motion velocity (P = 0.007). CONCLUSION: M-mode sonography enabled us to demonstrate that the wearing of a nose clip and breathing through a mouthpiece and a pneumotachograph induce measurable changes in diaphragm kinetics.

Adult↗

PubMed1997

Changes in maximal exercise ventilation and breathing pattern in boys during growth: a mixed cross-sectional longitudinal study.

The aim of this mixed cross-sectional longitudinal study covering a total age range of 11-17 years, i.e. the entire pubertal growth period, was (1) to specify the changes in maximal breathing pattern during incremental exercise; (2) to determine what parts of the changes are due to anthropometric characteristics, physical fitness and inspiratory or expiratory muscle strength; and (3) to determine if the role of these variables is identical before, during and after pubertal growth spurt. This study was conducted in 44 untrained schoolboys separated into three groups, with an initial age of 11.2 +/- 0.2 years for group A, 12.9 +/- 0.25 years for group B, and 14.9 +/- 0.26 years for group C. These children were subsequently followed for 3 years, during the same time period each year. The maximal inspiratory and expiratory pressures (PI max and PE max) were used as an index of the respiratory muscle strength. During an incremental exercise test, maximal ventilation (VE max), tidal volume (VT max), breathing frequency (fmax), inspiratory and expiratory times (tI max and tE max) and mean inspiratory flow (VT/tI max) were measured at maximal oxygen uptake (VO2max). Our study showed that there was a marked increase with age in VE max, VT max, and VT/tI max, and no significant changes in fmax, tI max and tE max. PI max and PE max showed a general trend towards an increase between 11 and 17 years. The study of the linear correlations between maximal breathing pattern and the anthropometric characteristics, physical fitness and inspiratory or expiratory muscle strength showed that, in the three groups of children, (1) lean body mass was the major determinant of VE max, VT max and VT/tI max and the relationships were significantly different before, during and after the pubertal growth spurt; (2) physical fitness was the main determinant of tI max, tE max and fmax before and after the pubertal growth spurt; and (3) maximal respiratory strength did not play a significant role. In conclusion, this mixed cross-sectional longitudinal study showed, at maximal exercise, a significant increase in VE max during growth due only to a significant increase in VT max and VT/tI max, and that the relationships of anthropometric characteristics and physical fitness with maximal breathing pattern change during growth.

Adolescent↗

PubMed1997

Effect of step duration during incremental exercise on breathing pattern and mouth occlusion pressure.

We compared the effects of two step durations on breathing pattern, mouth occlusion pressure and "effective" impedance of the respiratory system during incremental exercise. Nine normal subjects (mean age: 27.8+/-1.21 years) performed two incremental exercise tests in randomized order: one test with step increments every 1 min 30s and the other, every 4 min. After a warm-up at 25 W for the 1 min 30 s test, the power was increased by 50 W from 50 W to exhaustion. During the last minute at each power, we measured ventilation (VE), tidal volume (VT), breathing frequency (fR), inspiratory and expiratory time (TI and TE), total time of the respiratory cycle (TTOT), TI/TTOT, mean inspiratory flow (VT/TI), mouth occlusion pressure (P0.1), "effective" impedance of the respiratory system (P0.1/(VT/ TI)) and venous blood lactate concentration ([La]). Our result showed that at maximal exercise the power was significantly higher (p < 0.01) and [La] lower (p < 0.01) in the 1 min 30 s test. At 100, 150 and 200 W, the 4 min test showed significantly higher oxygen uptake (VO2), carbon dioxide output (VCO2), VE, P0.1, fR, VT/TI and HR (p <0.001) and significantly lower TI, TE and TTOT (p<0.01). [La] was significantly higher at 150 W (p<0.05) and 200 W (p<0.001). At the same VCO2, P0.1 was not significantly different between the two tests, whereas VE showed a tendency to be higher (p = 0.08) and P0.1/(VT/TI) was significantly lower during the 4 min test. In conclusion, this study allowed us to quantify the difference in inspiratory neuromuscular output and ventilatory response between 1 min 30s and 4 min tests and showed that different step durations alter the relationship between inspiratory neuromuscular output and mean inspiratory flow.

Adult↗

PubMed1996

Differences in mouth occlusion pressure and breathing pattern between arm and leg incremental exercise.

The aim of the study was to compare breathing pattern, mouth occlusion pressure, mean inspiratory flow and the ratio of mouth occlusion pressure to mean inspiratory flow at the same power output and carbon dioxide output during arm and leg incremental exercise. Mouth occlusion pressure was used as an index of inspiratory neuromuscular activity and its ratio to mean inspiratory flow as an index of the 'effective' impedance of the respiratory system. Eight normal subjects performed two incremental exercise tests, one with arms, the other with legs, on different weeks and in randomized order, and on two identical cycle ergometers. The power output was increased by steps of 25 W for arms and 50 W for legs every 4 min until exhaustion. At the same power output, oxygen consumption, carbon dioxide output, ventilation, mean inspiratory flow, mouth occlusion pressure, 'effective' impedance (P < 0.001) and respiratory frequency (P < 0.01) were higher during arm exercise than during leg exercise, whereas inspiratory time (P < 0.05) and expiratory time (P < 0.01) were lower. At the same carbon dioxide output, mouth occlusion pressure, ventilation, 'effective' impedance (P < 0.001) and respiratory frequency (P < 0.01) were higher and expiratory time (P < 0.05) was lower during arm exercise. In conclusion, the higher inspiratory neuromuscular activity and impedance of the respiratory system during arm exercise and the differences observed in ventilation and breathing pattern at equal carbon dioxide output seem related to the differences in exercising muscle afferents and the presence of an increased load due to contraction of rib cage muscles to stabilize posture.

Adult↗

PubMed1995

Pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise in young trained and untrained adults.

To investigate pulmonary gas exchange and ventilatory responses to brief intense intermittent exercise and to study the effects of physical fitness on these responses, nine trained and nine untrained healthy male subjects aged 18-33 years performed the force-velocity (F-v) exercise test. This test consisted of 6-s sprints against increasing braking forces (F) separated by 5-min recovery periods. Oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) were continuously measured during the test and the magnitudes of their responses to the sprints were then calculated. For all subjects VO2 increased rapidly after beginning the sprints, and the peaks of the responses (F = 13.4; P < 0.001), end of recovery values (F = 6.5; P < 0.01), and VO2 magnitudes of response (F = 12.4; P < 0.001) rose significantly with the repetition of the sprints. The VO2 magnitudes of response correlated with the corresponding sprint power outputs (r = 0.55; P < 0.001) and with the sprint repetitions (r = 0.51, P < 0.001). The VCO2 (F = 7.1; P < 0.01) and VE (F = 5.0; P < 0.01) peaks of response increased with the initial load incrementation, then stabilized when the subjects attained peak power output. End of recovery VCO2 (F = 18.0; P < 0.001) and VE (F = 14.1; P < 0.001) values rose with increasing F. The F-v peak VO2, VCO2, VE, tidal volume and respiratory frequency responses attained 53%, 40%, 44%, 66%, and 82% of the peak values measured at exhaustion of maximal graded exercise, respectively. (ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Validation of a noninvasive tension-time index of inspiratory muscles.

The aim of this study was to validate a noninvasive tension-time index (TT) for all the inspiratory muscles estimated from the measurement of mouth occlusion pressure (P0.1), i.e., TT of inspiratory muscles (TTmus = PI/PImax x TI/TT, where PI is mean inspiratory pressure, PImax is maximal PI, TI is time of muscle contraction, and TT is total time of respiratory cycle) compared with TT of the diaphragm (TTdi = Pdi/Pdimax x TI/TT, where Pdi is mean transdiaphragmatic pressure and Pdimax is maximal Pdi). PI was estimated as PI = 5 P0.1 x TI. Eleven patients with chronic obstructive pulmonary disease and seven normal subjects were studied at rest in the sitting position. After 5 min of steady state, we measured breathing pattern, gastric and esophageal pressures, Pdi, mean inspiratory transpulmonary pressure swing, PImax, and Pdimax. By linear regression analysis, significant positive correlations were found between PI and mean inspiratory transpulmonary pressure swing, PI and Pdi, PImax and Pdimax, and PI/PImax and Pdi/Pdimax, with P < 0.001 for all subjects combined. These led to the highly significant correlation between TTmus and TTdi for all subjects combined (TTmus = 2.1 TTdi + 0.012; r = 0.97; P < 0.001) and for patients only (TTmus = 2.0 TTdi + 0.024; r = 0.97; P < 0.001). Therefore, patterns of breathing that lie near fatigue thresholds can be identified with TTmus or TTdi. In conclusion, noninvasive and clinically easily determined TTmus seems valid for situating patients of chronic obstructive pulmonary disease in reference to the inspiratory muscle fatigue.

Aged↗

PubMed1995

[Evolution of breathing pattern and ventilation at maximal exercise during growth. Definition of reference values].

The aim of the study was to define the changes of parameters of breathing pattern and ventilation (VE) as a function of age during maximal exercise in children. A multi-longitudinal survey was conducted in forty four untrained schoolboys, divided in three groups with initial age of 11.2 years for group I, 12.9 years for group II, and 14.9 for group III. These children were subsequently followed three years ago at the same period. The range age was thus 11.2 to 16.9 years. This study showed that, during growth, ventilation (VE max), tidal volume (VT max) and mean inspiratory flow (VT/TI max) increased significantly with age, that inspiratory frequency (f max) decreased, that inspiratory, expiratory and total time of the respiratory cycle (TI max, TE max, TTOT max) increased slightly and that the inspiration fraction (TI/TTOT max) was identical at 11 and 17 years. Furthermore we observed that the peak height velocity and peak tidal volume velocity took place at the same age, i.e., 14 years and that those of weight and VT/TI at the same age of 15 years. In conclusion, this study allowed us to define reference values for breathing pattern at maximal exercise in sedentary boys and to specify the relation between growth and parameters of breathing pattern in these children.

Adolescent↗

PubMed1993

Ventilatory response of prepubertal boys and adults to carbon dioxide at rest and during exercise.

The aim of this study was to determine whether the greater ventilation in children at rest and during exercise is related to a greater CO2 ventilatory response. The CO2 ventilatory response was measured in nine prepubertal boys [10.3 years (SD 0.1)] and in 10 adults [24.9 years (SD 0.8)] at rest and during moderate exercise (VCO2 = 20 ml.kg-1.min-1) using the CO2-rebreathing method. Three criteria were measured in all subjects to assess the ventilatory response to CO2: the CO2 sensitivity threshold (Th), which was defined as the value of end tidal PCO2 (PETCO2) where the ventilation increased above its steady-state level; the reactivity slope expressed per unit of body mass (SBM), which was the slope of the linear relation between minute ventilation (VE) and PETCO2 above Th; and the slope of the relationship between the quotient of tidal volume (VT) and inspiration time (tI) and PETCO2 (VT.tI-1.PETCO2(-1)) values above Th. The VE, VT, breathing frequency (fR), oxygen uptake (VO2), and CO2 production (VCO2) were also measured before the CO2-rebreathing test. The following results were obtained. First, children had greater ventilation per unit body weight than adults at rest (P < 0.001) and during exercise (P < 0.01). Second, at rest, only VT.tI-1.PETCO2(-1) was greater in children than in adults (P < 0.001). Third, during exercise, children had a higher SBM (P < 0.02) and VT.tI-1.PETCO2(-1) (P < 0.001) while Th was lower (P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

Breathing pattern and ventilatory response to CO2 during exercise.

The aim of this study was to determine during moderate exercise whether response to the CO2 rebreathing test was dependent on differences in breathing pattern components among individuals recorded before the test and whether differences in tidal volume response and/or breathing frequency response to CO2 during the test could influence their ventilatory response to CO2. Ten healthy, sedentary male subjects, 20 to 34 years old, participated in the study. Ventilatory response to CO2 was measured by the CO2 rebreathing method (7% CO2, 50% O2). The measurements of breathing pattern components and CO2 rebreathing were made during mild steady state exercise: VCO2 = 20 ml.kg-1.min-1. We measured the following: 1) tidal volume (VTex) and breathing frequency (fex) before CO2 rebreathing and 2) ventilatory response to CO2 (SVEex), tidal volume response to CO2 (SVTex), and breathing frequency response to CO2 (Sfex) during the CO2 rebreathing test. The results showed that SVEex was correlated with VTex (r = 0.89, p less than 0.001), fex (r = -0.79, p less than 0.01), and Sfex (r = 0.83, p less than 0.01). There was no correlation between SVEex and SVTex. A curvilinear relationship existed between SVEex and alveolar ventilation calculated during exercise (r = 0.87, p less than 0.001), but there was no correlation with dead space. Sfex was positively correlated with VTex (r = 0.68, p less than 0.05) and negatively with fex (r = -0.70, p less than 0.05). We concluded that, during moderate exercise, higher tidal volumes measured before CO2 rebreathing were associated with higher response to the CO2 rebreathing test and consequently with higher ventilatory response to CO2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1991

Influence of anthropometric characteristics on changes in maximal exercise ventilation and breathing pattern during growth in boys.

The aim of this study was to investigate the effect of growth on ventilation and breathing pattern during maximal exercise oxygen consumption (VO2max) and their relationships with anthropometric characteristics. Seventy six untrained schoolboys, aged 10.5-15.5 years, participated in this study. Anthropometric measurements made included body mass, height, armspan, lean body mass, and body surface area. During an incremental exercise test, maximal ventilation (VEmax), tidal volume (VTmax), breathing frequency (fmax), inspiratory and expiratory times (tImax and tEmax), total duration of respiratory cycle (tTOTmax), mean inspiratory flow (VT/tImax), and inspiration fraction (tI/tTOTmax) were measured at VO2max. A power function was calculated between anthropometric characteristics and ventilatory variables to determine the allometric constants. The results showed firstly, that VEmax, VTmax, tImax, tEmax, tTOTmax, and VT/tImax increased with age and anthropometric characteristics (P less than 0.001), fmax decreased (P less than 0.001), and tI/tTOTmax remained constant during growth; secondly that lean body mass explained the greatest percentage of variance of VEmax (62.1%), VTmax (76.8%), and VT/tImax (70.6%), while anthropometric characteristics explained a slight percentage of variance of fmax and timing; and thirdly that VEmax, VTmax, and VT/tImax normalized by lean body mass did not change significantly with age. We concluded that at VO2max there were marked changes in ventilation and breathing pattern with growth. The changes in VEmax, VTmax, and VT/tImax were strongly related to the changes in lean body mass.

Adolescent↗

PubMed1991

Effect of resistive loads on pattern of respiratory muscle recruitment during exercise.

In healthy subjects, we compared the effects of an expiratory (ERL) and an inspiratory (IRL) resistive load (6 cmH2O.l-1.s) with no added resistive load on the pattern of respiratory muscle recruitment during exercise. Fifteen male subjects performed three exercise tests at 40% of maximum O2 uptake: 1) with no-added-resistive load (control), 2) with ERL, and 3) with IRL. In all subjects, we measured breathing pattern and mouth occlusion pressure (P0.1) from the 3rd min of exercise, in 10 subjects O2 uptake (VO2), CO2 output (VCO2), and respiratory exchange ratio (R), and in 5 subjects we measured gastric (Pga), pleural (Ppl), and transdiaphragmatic (Pdi) pressures. Both ERL and IRL induced a high increase of P0.1 and a decrease of minute ventilation. ERL induced a prolongation of expiratory time with a reduction of inspiratory time (TI), mean expiratory flow, and ratio of inspiratory to total time of the respiratory cycle (TI/TT). IRL induced a prolongation of TI with a decrease of mean inspiratory flow and an increase of tidal volume and TI/TT. With ERL, in two subjects, Pga increased and Ppl decreased more during inspiration than during control suggesting that the diaphragm was the most active muscle. In one subject, the increases of Ppl and Pga were weak; thus Pdi increased very little. In the two other subjects, Ppl decreased more during inspiration but Pga also decreased, leading to a decrease of Pdi. This suggests a recruitment of abdominal muscles during expiration and of accessory and intercostal muscles during inspiration. With IRL, in all subjects, Ppl again decreased more, Pga began to decrease until 40% of TI and then increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Hyperpnoea and CO2 sensitivity of the respiratory centres during exercise.

The aim of this study was to specify whether exercise hyperpnoea was related to the CO2 sensitivity of the respiratory centres measured during steady-state exercise of mild intensity. Thus, ventilation (VE), breathing pattern [tidal volume (VT), respiratory frequency (f), inspiratory time (TI), total time of the respiratory cycle (TTOT), VT/TI, TI/TTOT] and CO2 sensitivity of the respiratory centres determined by the rebreathing method were measured at rest (SCO2re) and during steady-state exercise (SCO2ex) of mild intensity [CO2 output (VCO2) = 20 ml.kg-1.min-1] in 11 sedentary male subjects (aged 20-34 years). The results showed that SCO2re and SCO2ex were not significantly different. During exercise, there was no correlation between VE and SCO2ex and, for the same VCO2, all subjects had very close VE values normalized for body mass (bm), regardless of their SCO2ex (VEbm0.75 = 1.44 l.min-1.kg-1 SD 0.10). A highly significant positive correlation between SCO2ex and VT (normalised for bm) (r = 0.80, P less than 0.01), TI (r = 0.77, P less than 0.01) and TTOT (r = 0.77, P less than 0.01) existed, as well as a highly significant negative correlation between SCO2ex and (normalised for bm-0.25) (r = -0.73, P less than 0.01). We conclude that the hyperpnoea during steady-state exercise of mild intensity is not related to the SCO2ex. The relationship between breathing pattern and SCO2ex suggests that the breathing pattern could influence the determination of the SCO2ex. This finding needs further investigation.

Adult↗

PubMed1989

Relationship between aerobic physical fitness and ventilatory control during exercise in young swimmers.

The aim of this study was to specify in young trained swimmers, during progressive exercise, whether different aerobic physical fitness goes along with differences in breathing pattern and in mouth occlusion pressure used as a non-invasive index of neuromuscular output. Ten children (aged 10.5-16 years) with high VO2 max (57.6 +/- 3.6 ml.min-1.kg-1) and ten children (aged 11-17 years) with moderate VO2 max (44 +/- 3.8 ml.min-1.kg-1) realized a maximal exercise test on a cycle ergometer. During the last minute of each power level we measured the following parameters: VO2, VCO2, VEBW, f, VTBW/TI,TI/TTOT, as well as mouth occlusion pressure (P0.1) and 'effective impedance' of the respiratory system (P0.1/VTBW/TI). Our results showed that at a same VCO2, children with high VO2 max had significantly lower P0.1, P0.1/VTBW/TI and f than children with moderate VO2 max and same VEBW/TI. At different levels of VO2, in the twenty children of the two groups, we have found significant correlations between VO2 max of each subject and P0.1 (P less than 0.01), P0.1/VTBW/TI (P less than 0.001). At a same VO2, children with a higher VO2 max showed significantly lower P0.1, P0.1/VTBW/TI at all levels of VO2 and lower VEBW and VTBW/TI at high level of VO2. At a same VE, the two groups of children showed the same values of VT/TI and f. In conclusion this study shows first, that different aerobic physical fitness does not go along with different breathing pattern, and second, that swimmers with high physical fitness have a lower ventilatory response to exercise but a higher ventilatory and neuromuscular efficiency during exercise than children with moderate physical fitness.

Adolescent↗