Publications (12)37.31 Total impact
-
Article: CARBON MONOXIDE MEMBRANE CONDUCTANCE AND CAPILLARY VOLUME COMPONENTS OF LUNG DIFFUSING CAPACITY IN HIGH ALTITUDE NEWCOMERS.
[show abstract] [hide abstract]
ABSTRACT: Acute exposure to high altitude (HA) induces changes in CO membrane conductance (DmCO) and capillary lung volume (Vc). One source of scatter in literature data is exercise, climbing, prior to HA which was avoided in this study. Measurements were performed in 25 lowlanders at Brussels (D0) and at 4300 m after a 2 or 3 days exposure (D2,3), before and after an exercise test, and 5 days later (D7,8) under a trial with two arterial pulmonary vasodilators and a placebo group. The NO/CO transfer method was used applying either an infinite or a finite value to the NO blood conductance (θNO) which could alter sharply the results. A doppler echocardiography provided the haemodynamic data. Compared to sea level, DLCO increased by 24% at D2,3 and returned to control at D7,8. The increase in DLCO resulted from increases in DmCOand Vc whatever the θNO value The alveolar volume (VA) increased by 16% at D2,3 and normalized at D7,8. The mean increase in systolic arterial pulmonary pressure at rest at D2,3 was slight. The increase in Vc in acute condition might be due to the increase in VA and to the increase in capillary pressure. . Compared to the infinite θNO value, the use of a finite θNO value led to about a two-fold increase in DmCO value and to a persistent increase in DmCO at D7,8 compared to D0. After exercise DmCO decreased slightly in subjects treated by the vasodilators suggesting an effect on interstitial oedema.Journal of Applied Physiology 04/2013; · 3.75 Impact Factor -
Article: Pulmonary vascular reserve and exercise capacity at sea level and at high altitude.
[show abstract] [hide abstract]
ABSTRACT: Abstract Pavelescu, Adriana, Vitalie Faoro, Herve Guenard, Claire de Bisschop, Jean-Benoit Martinot, Christian Melot, Robert Naeije. Pulmonary vascular reserve and exercise capacity at sea level and at high altitude. High Alt. Med. Biol. 14:19-26, 2013.-It has been suggested that increased pulmonary vascular reserve, as defined by reduced pulmonary vascular resistance (PVR) and increased pulmonary transit of agitated contrast measured by echocardiography, might be associated with increased exercise capacity. Thus, at altitude, where PVR is increased because of hypoxic vasoconstriction, a reduced pulmonary vascular reserve could contribute to reduced exercise capacity. Furthermore, a lower PVR could be associated with higher capillary blood volume and an increased lung diffusing capacity. We reviewed echocardiographic estimates of PVR and measurements of lung diffusing capacity for nitric oxide (DLNO) and for carbon monoxide (DLCO) at rest, and incremental cardiopulmonary exercise tests in 64 healthy subjects at sea level and during 4 different medical expeditions at altitudes around 5000 m. Altitude exposure was associated with a decrease in maximum oxygen uptake (Vo2max), from 42±10 to 32±8 mL/min/kg and increases in PVR, ventilatory equivalents for CO2 (VE/Vco2), DLNO, and DLCO. By univariate linear regression Vo2max at sea level and at altitude was associated with VE/Vco2 (p<0.001), mean pulmonary artery pressure (mPpa, p<0.05), stroke volume index (SVI, p<0.05), DLNO (p<0.02), and DLCO (p=0.05). By multivariable analysis, Vo2max at sea level and at altitude was associated with VE/Vco2, mPpa, SVI, and DLNO. The multivariable analysis also showed that the altitude-related decrease in Vo2max was associated with increased PVR and VE/Vco2. These results suggest that pulmonary vascular reserve, defined by a combination of decreased PVR and increased DLNO, allows for superior aerobic exercise capacity at a lower ventilatory cost, at sea level and at high altitude.High altitude medicine & biology 03/2013; 14(1):19-26. · 1.58 Impact Factor -
Article: Improvement in lung diffusion by endothelin A receptor blockade at high altitude.
[show abstract] [hide abstract]
ABSTRACT: Lung diffusing capacity has been reported variably in high-altitude newcomers and may be in relation to different pulmonary vascular resistance (PVR). Twenty-two healthy volunteers were investigated at sea level and at 5,050 m before and after random double-blind intake of the endothelin A receptor blocker sitaxsentan (100 mg/day) vs. a placebo during 1 wk. PVR was estimated by Doppler echocardiography, and exercise capacity by maximal oxygen uptake (Vo(2 max)). The diffusing capacities for nitric oxide (DL(NO)) and carbon monoxide (DL(CO)) were measured using a single-breath method before and 30 min after maximal exercise. The membrane component of DL(CO) (Dm) and capillary volume (Vc) was calculated with corrections for hemoglobin, alveolar volume, and barometric pressure. Altitude exposure was associated with unchanged DL(CO), DL(NO), and Dm but a slight decrease in Vc. Exercise at altitude decreased DL(NO) and Dm. Sitaxsentan intake improved Vo(2 max) together with an increase in resting and postexercise DL(NO) and Dm. Sitaxsentan-induced decrease in PVR was inversely correlated to DL(NO). Both DL(CO) and DL(NO) were correlated to Vo(2 max) at sea level (r = 0.41-0.42, P < 0.1) and more so at altitude (r = 0.56-0.59, P < 0.05). Pharmacological pulmonary vasodilation improves the membrane component of lung diffusion in high-altitude newcomers, which may contribute to exercise capacity.Journal of Applied Physiology 01/2012; 112(1):20-5. · 3.75 Impact Factor -
Article: Pulmonary capillary blood volume and membrane conductance in Andeans and lowlanders at high altitude: A cross-sectional study.
[show abstract] [hide abstract]
ABSTRACT: Lung carbon monoxide (CO) transfer and pulmonary capillary blood volume (Vc) at high altitudes have been reported as being higher in native highlanders compared to acclimatised lowlanders but large discrepancies appears between the studies. This finding raises the question of whether hypoxia induces pulmonary angiogenesis. Eighteen highlanders living in Bolivia and 16 European lowlander volunteers were studied. The latter were studied both at sea level and after acclimatisation to high altitude. Membrane conductance (Dm(CO)) and Vc, corrected for the haemoglobin concentration (Vc(cor)), were calculated using the NO/CO transfer technique. Pulmonary arterial pressure and left atrial pressures were estimated using echocardiography. Highlanders exhibited significantly higher NO and CO transfer than acclimatised lowlanders, with Vc(cor)/VA and Dm(CO)/VA being 49 and 17% greater (VA: alveolar volume) in highlanders, respectively. In acclimatised lowlanders, Dm(CO) and Dm(CO)/VA values were lower at high altitudes than at sea level. Echocardiographic estimates of cardiac output and pulmonary arterial pressure were significantly elevated at high altitudes as compared to sea level. The decrease in Dm(CO) in lowlanders might be due to altered gas transport in the airways due to the low density of air at high altitudes. The disproportionate increase in Vc in Andeans compared to the change in Dm(CO) suggests that the recruitment of capillaries is associated with a thickening of the blood capillary sheet. Since there was no correlation between the increase in Vc and the slight alterations in haemodynamics, this data suggests that chronic hypoxia might stimulate pulmonary angiogenesis in Andeans who live at high altitudes.Nitric Oxide 11/2010; 23(3):187-93. · 3.55 Impact Factor -
Article: Does exercise have deleterious consequences for the lungs of patients with chronic heart failure?
[show abstract] [hide abstract]
ABSTRACT: Changes in lung function in patients with chronic heart failure (CHF), usually reported at rest, may be exacerbated during exercise and induce post-exercise effects. We investigated the hypothesis that post-exercise induced changes in lung function in CHF patients are due to the consequences of left atrial overload. Twenty-one CHF patients and six healthy subjects (Ctrl) participated in this study. Transfer lung capacity for carbon monoxide (T(LCO)) and maximal expiratory flows (V (max)) were measured before a maximal exercise test and 1h, 2h and 20h afterwards. CHF patients were divided in two groups according to their ventilatory response to the maximal exercise test (V(E) vs. V(CO(2)) relationship slopes above or below 34, i.e., CHF>34 and CHF<34). Compared with the Ctrl group, in CHF groups resting T(LCO) and V(max) were lower. After exercise, further changes in T(LCO) and V(max) were observed in CHF>34. T(LCO) per unit volume (K(CO)) was increased 1h post-exercise while maximal expiratory flow between 25 and 75% of forced vital capacity was decreased 2h and 20h post-exercise. We observed a negative correlation between the delta T(LCO) 1h post-exercise from rest and the delta T(LCO) 2h post-exercise from rest. The decreases in pulmonary V(max) we observed well after exercise following increases in K(CO) in patients with high ventilatory response to exercise (CHF>34) might indicate bronchial congestion resulting from increased left atrial pressure during exercise. We propose that endurance training should be prescribed cautiously for these patients.Respiratory medicine 12/2008; 103(3):393-400. · 2.33 Impact Factor -
Article: Echocardiographic right ventricular strain analysis in chronic heart failure.
[show abstract] [hide abstract]
ABSTRACT: We sought to compare the additive value of right ventricular (RV) function assessed by longitudinal systolic strain (epsilon% - ROI: 9.2 at 10.8 mm) with cardiopulmonary exercise testing (CPET) or brain natriuretic peptide (BNP) in patients with heart failure (HF). We studied 19-patients (age = 56 +/- 8 years) in New York Heart Association HF class III-IV, who underwent standard and tissue Doppler echocardiography, CPET and BNP measurements on the same day. RV function was assessed by systolic strain (epsilon, %, ROI: 9.2-10.8 mm) in the mid-segment. Clinical outcomes were examined at 6 months. epsilon (-19.9+/-6.8%) was correlated with BNP (R = 0.52, P = 0.02), slope VE/VCO(2) (R = -0.65, P = 0.003), peak VO(2) (R = 0.46, P = 0.04) and the maximal workload (Watts) developed during CPET (R = 0.54, P=0.02). During follow-up, 1-patient died, 1-underwent heart transplantation, and 4 were re-hospitalized for worsening HF. Patients with major adverse cardiac events (MACE) had a significantly higher mean BNP concentration (852.8 ng/mL +/- 1114.3 vs. 201.4+ /- 293.8, P = 0.03), higher VE/VCO(2) (41.3 +/- 3.6 vs. 35.0 +/- 4.8 P < 0.001) and lower epsilon (-13.9 +/- 4.9 vs. -22.2+ /- 5.8, P < 0.001) than patients who remained MACE-free. By multivariate analysis, ST was the only predictor of MACE. In HF-patients presenting, RV-function assessed by systolic epsilon was reliable, easily measurable and a stronger prognosticator than CPET or BNP.European Heart Journal – Cardiovascular Imaging 12/2007; 8(6):449-56. · 2.32 Impact Factor -
Article: Deciphering the nitric oxide to carbon monoxide lung transfer ratio: physiological implications.
[show abstract] [hide abstract]
ABSTRACT: Using simultaneous nitric oxide and carbon monoxide lung transfer measurements (T(LNO) and T(LCO)), the membrane transfer capacity (D(m)) and capillary lung volume (V(c)) as well as the dimensionless ratio T(LNO)/T(LCO) can be calculated. The significance of this ratio is yet unclear. Theoretically, the T(LNO)/T(LCO) ratio should be inversely related to the product of both lung alveolar capillary membrane (mu) and blood sheet thicknesses (K). NO and CO transfers were measured in healthy subjects in various conditions likely to be associated with changes in K and/or mu. Experimentally, deflation of the lung from 7.4 to 4.8 l decreased the T(LNO)/T(LCO) ratio from 4.9 to 4.2 (n=25) which was consistent mainly with a thickening of the blood sheet. Compared with continuous negative pressure breathing, continuous positive pressure breathing increased this ratio suggesting a thinning of the capillary sheet. It was also observed with 12 healthy subjects that slight haemodilution that may thicken the blood sheet decreased the T(LNO)/T(LCO) ratio from 4.85 to 4.52. In conclusion, the T(LNO)/T(LCO) ratio is related to the thickness of the alveolar blood barrier. This ratio provides novel information for the analysis of the diffusion properties.The Journal of Physiology 08/2007; 582(Pt 2):767-75. · 4.72 Impact Factor -
Article: Expiratory muscles modulate negative expiratory pressure-induced flow during muscular exercise.
[show abstract] [hide abstract]
ABSTRACT: The recruitment of expiratory muscles during exercise might be altered by the application of negative expiratory pressure (NEP) inducing a feature of expiratory flow limitation (EFL) called muscle EFL. To check this hypothesis EFL and expiratory muscle EMG (ExpEMG) were measured at rest and during exercise in eight healthy subjects. Six subjects performed isocapnic hyperventilation. At 5hPa NEP, 5/8 subjects had EFL during exercise. This limitation disappeared when NEP value was increased and did not appear during isocapnic hyperventilation. During exercise, in limited subjects, ExpEMG was significantly reduced during expiration with NEP as compared to control. Gastric pressure measured in a limited subject increased during expiration but less with NEP than without it, while this pressure measured in another, non-limited, subject decreased. An inhibitory reflex due to negative pressure could be responsible for muscle EFL by reducing expiratory muscle activity. The response to NEP during exercise should be interpreted with caution.Respiratory Physiology & Neurobiology 01/2007; 154(3):453-66. · 2.24 Impact Factor -
Article: Spectral analysis of heart rate variability: interchangeability between autoregressive analysis and fast Fourier transform.
[show abstract] [hide abstract]
ABSTRACT: Interchangeability between fast Fourier transform (FFT) and autoregressive (AR) analysis was assessed on series of 256 R-R intervals recorded in 56 seated subjects and in 15 men performing an orthostatic test. Low- (LF) and high-frequency (HF) components were calculated and expressed both in absolute (square milliseconds) and normalized units (NU). During orthostatic stress, the same upward trend for LF square milliseconds and LF/HF ratio and downward trend for HF square milliseconds and HF NU were observed with FFT and AR analysis. However, the values for HF square milliseconds were significantly greater with FFT, as compared with AR analysis in standing position (P < .05). Moreover, Bland & Altman method highlighted a large discrepancy between the results of FFT and AR analysis for all heart rate variability indices in the 3 conditions. Therefore, parametric and nonparametric spectral analyses could not be considered as interchangeable at rest in healthy subjects even if they give same qualitative results.Journal of Electrocardiology 01/2006; 39(1):31-7. · 1.14 Impact Factor -
Article: Parasympathetic airway response and heart rate variability before and at the end of methacholine challenge.
[show abstract] [hide abstract]
ABSTRACT: The autonomic nervous system plays a primary role in regulating airway caliber, and its dysfunction is likely to contribute to the pathogenesis of airways diseases. Moreover, some findings support the hypothesis that autonomic dysfunction and/or dysregulation contributes to the pathogenesis of airway hyperresponsiveness (AHR). Heart rate variability (HRV) spectral analysis allows identifying noninvasively perturbations of the autonomic system. We tested the relationship between AHR and cardiac parasympathetic tone assessed by HRV spectral analysis in patients submitted to a diagnostic methacholine bronchial challenge (MBC). Fifteen women and 38 men (age range, 18 to 56 years) participated in the study. The principal indications for MBC were suspected asthma, chronic cough, unexplained exercise-induced dyspnea, or cough. The R-R intervals were continuously recorded during the MBC. Autoregressive method was performed on two series of 256 R-R intervals extracted before and after the MBC to obtain low-frequency (LF) and high-frequency (HF) components. The MBC distinguished 29 subjects without airway responsiveness (R-) and 24 responder or hyperresponsive subjects (R+): mean provocative dose of methacholine causing a 20% reduction in mean (+/- SD) FEV1 of 467 +/- 351 microg (range, 70 to 1,426 microg). The HF component expressed in normalized units (n.u.) [the index of parasympathetic modulation] was significantly higher in R+ than in R- at baseline, before MBC (21 +/- 21 n.u. vs 11 +/- 9 n.u., p < 0.05). Interestingly, R+ showed a significant increase of HF component after MBC (243 +/- 30 to 567 +/- 620 ms2 and 21 +/- 21 to 34 +/- 30 n.u., p < 0.01). For all subjects, HF (n.u.) calculated at baseline and after MBC were significantly influenced by the bronchial responsiveness (r2 = -0.28 and -0.51, respectively; p < 0.001). In summary, we found that R+ had a significantly higher parasympathetic tone than R- at baseline, and that R+ showed a significant increase in cardiac reactivity after bronchial challenge. These findings demonstrate that the autonomic nervous system, which contributes to the pathogenesis of AHR, is closely linked to cardiac modulation.Chest 02/2005; 127(1):23-9. · 5.25 Impact Factor -
Article: Spectral analysis of heart rate variability during exercise in trained subjects.
[show abstract] [hide abstract]
ABSTRACT: To investigate the effects of strenuous exercise on heart rate variability (HRV). We evaluated the effects of exercise intensity and duration on HRV indices in 14 healthy trained subjects. Each subject exercised for 3, 6, and 9 min at 60 and 70% of the power achieved at maximal oxygen consumption (PVO2(max)) and for 3 and 6 min (or 3 min twice) at 80% of PVO2(max). The electrocardiogram RR intervals were recorded then processed by fast(FFT) and short-time (STFT) Fourier transform for determination of low-frequency (LF, 0.045-0.15 Hz) and high-frequency (HF, 0.15-1.0 Hz) components. The LF and HF components expressed as absolute power (ms2) decreased significantly at the onset of exercise (P < 0.05). However, with increasing exercise intensity, the HF component expressed as normalized units (n.u.) (reflecting parasympathetic modulation) increased significantly, whereas the LF component (n.u.) and LF/HF ratio (both reflecting sympathetic modulation) decreased significantly (P < 0.05). STFT showed that increasing exercise intensity was associated with a shift in HF peak frequency related to an increase in respiratory rate and a marked decrease in LF power (ms2). Moreover, HFn.u. rose (r = 0.918, P < 0.01) and LFms2 fell as minute ventilation increased (r = 0.906, P < 0.01). Parasympathetic respiratory control and nonautonomic mechanisms may influence the HF-peak shift during strenuous exercise. HRV and the usual indexes of sympathetic activity do not accurately reflect changes in autonomic modulation during exhaustive exercise.Medicine & Science in Sports & Exercise 10/2004; 36(10):1702-8. · 4.43 Impact Factor -
Article: Accounting for flow dependence of respiratory resistance during exercise.
[show abstract] [hide abstract]
ABSTRACT: Studies of airway function during exercise have produced conflicting results both in healthy and diseased subjects. Respiratory resistance (Rrs) was measured using an impulse oscillation technique. A flow/resistance curve was established for each of 16 healthy males during voluntary hyperventilation (VHV) at rest. Then, Rrs and flow were measured immediately (t(0)) and 90 sec (t(90)) after exercise on a cycle ergometer at 60, 70, and 80% of maximal aerobic power. The flow/resistance relationship at rest during VHV was used to assess the flow dependence of Rrs. Rrs at t(0) was higher than at rest (P <0.01) but lower than Rrs obtained at matched flow during VHV (P <0.05). In healthy subjects, the linear increase in Rrs with VHV indicates airflow dependency of Rrs following Rohrer's equation. The relative decrease in Rrs with exercise suggests bronchodilation. The bronchodilating effect disappeared promptly when exercise was stopped suggesting that it may have been related to a reflex mechanism.Respiratory Physiology & Neurobiology 06/2003; 136(1):65-76. · 2.24 Impact Factor
Top co-authors
Top Journals
Institutions
-
2003–2012
-
Université de Poitiers
- Laboratoire des Adaptations Physiologiques aux Activités Physiques (LAPHAP)
Poitiers, Poitou-Charentes, France
-
-
2007
-
Centre Hospitalier Universitaire de Rennes
Rennes, Brittany, France
-
