PubMed Health⌕ Search

Biomedical subjects

P Escourrou

Publications and source records attributed to P Escourrou.

At least 55 records · Page 3Linked to original sources
PubMed1991

[Vasomotor activity and vascular geometry].

The circulation may be divided into several anatomical and functional segments placed in series. The vessels of distribution (great arteries) are designed to decrease the cardiac periodicity. The tone of the resistance vessels (arterioles) control the blood pressure. In situ changes of their diameter must be assessed with respect to variations in pressure in order to evaluate the active or passive mechanism of a physiological or therapeutic intervention. The vessels of exchange (capillaries, veinules) which have no smooth muscle in their walls are passively affected by changes in flow and transmural pressure. The capacitance vessels (veins) are partially affected by the blood flow entering this segment and influence the cardiac output by the effects of changes of volume on venous return to the heart.

Blood Vessels↗
PubMed1990

Neonatal patterns of breathing after cesarean section with or without epidural fentanyl.

The pattern of breathing and lung mechanics were evaluated during the first 7 h of life in full-term healthy newborns delivered by cesarean section with bupivacaine epidural anesthesia, without (group 1) or with the addition of 100 micrograms of fentanyl (group 2). Respiration and oxyhemoglobin saturation (SpO2) were measured with calibrated inductive plethysmography and pulse oximetry, respectively, and recorded from 60-420 min following birth. Compliance of respiratory system (CRS) was measured using a multiple occlusion technique at 60 and 420 min. Pattern of breathing was compared during period I (60-240 min) and II (240-420 min) with the following results: 1) the number of apnea spells was similar in both groups during both periods; 2) in both groups, from period I to period II a significant decrease in apnea duration was observed (7.6 +/- 0.7 s-4.1 +/- 0.5 s in group 1 and 6.7 +/- 1.2 s-5.1 +/- 1.0 s in group 2, respectively (P less than 0.05); 3) respiratory rate (RR) and minute ventilation (VE) were similar in both groups during both study periods; and 4) both RR and VE significantly decreased in the two groups from period I to period II (i.e., 59 +/- 5-46 +/- 2 breath per min-1 and 313 +/- 60-248 +/- 24 ml.kg-1.min-1 in group 1, and 60 +/- 2-51 +/- 1 breath.min-1 and 318 +/- 12-290 +/- 12 ml.kg-1.min-1 in group 2, respectively; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Esophageal reflux in symptomatic and asymptomatic infants: postprandial and circadian variations.

Twenty-two full-term infants, nine asymptomatic and 13 symptomatic for chronic digestive problems, had long-term (mean = 21 h) esophageal pH monitoring. All children were observed in strictly standardized conditions including meals and body position. Symptomatic infants presented significantly more esophageal refluxes, spent a greater percentage of time with a pH below 4, had a longer reflux duration (longer clearing time) and presented more refluxes lasting more than 5 min. We performed a determination of the circadian variations of parameters associated with esophageal reflux. Asymptomatic and symptomatic infants presented significant circadian variations of the percentage of time below pH 4 and of the longest duration of reflux. However, symptomatic infants had significantly higher mean values and increased amplitudes of circadian rhythms. Moderate phase lag existed for certain variables between symptomatic and asymptomatic infants. These findings can be helpful when interpreting the results of long-term esophageal pH monitoring.

Analysis of Variance↗
PubMed1990

Interaction between tracheal sound and flow rate: a comparison of some different flow evaluations from lung sounds.

We simultaneously recorded tracheal sound and air flow from nine normal subjects (seven males and two females). Sound was picked up at the supra sternal notch with an air-coupled sensitive microphone held in a small airtight probe. Flow was measured at the mouth using a pneumotachograph Fleisch n degrees 2. Both sound and flow were directly digitized at a sampling rate of 5120 Hz and then divided in 128-sample blocks. For each sound block the frequency spectrum was computed using the fast Fourier transform. In order to evaluate instantaneous flow-rate from tracheal sounds we investigated eight methods divided in two groups of four. In the first group (i.e., reference curves methods), we assumed that a relationship existed between sound and flow and was thus reflected by the variations of certain parameters. We chose to use simple straightforward relationships, already known and published. We tested four different parameters. During a calibration phase, we built for each parameter P a reference curve representing the variations of P versus flow and being specific to each subject. Then, an unknown flow was evaluated in calculating P on a 128-sample block, and the reference curve gave the corresponding flow. In the second group, we made a hierarchial clustering analysis of sound spectra for revealing the frequency modifications, induced by the flow. We tested two kinds of spectra as well as two ways of associating a flow to a given cluster. This led us to four other methods for calculating the flow. All the eight methods but one gave a mean uncertainty in the measure of flow of about 15%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Systemic hypertension in sleep apnea syndrome. Relationship with sleep architecture and breathing abnormalities.

To examine the possible relationship between systemic HT and SAS we compared 21 hypertensive (HT+) and 29 normotensive (HT-) patients for morphologic characteristics, sleep disturbances and respiratory events monitored during a full night polysomnography. There was no significant difference between HT+ and HT- patients with respect to age, weight, BMI, sleep stage distribution and disorganization, apnea-hypopnea index (number of episodes per hour of sleep) and duration (minutes per hour of sleep) nor O2 saturation indices: mean nocturnal and minimum O2 saturation. We conclude therefore that HT in SAS patients is not directly related to morphologic characteristics, sleep disturbances and breathing abnormalities.

Adult↗
PubMed1990

[Passive compliance of the total respiratory system in newborn infants born by cesarean section].

The compliance of the total respiratory system (CRS) was measured by the occlusion technique: a) at H1-H2, H6-H7 and D3-D4 in 8 full-term newborns after cesarean section; b) at H1-H2 and H6-H7 in 6 full-term newborns delivered vaginally and at D3-D4 in 10 full-term newborns delivered vaginally. At H1-H2 respiratory frequency measured by inductive plethysmography was not significantly different between newborns after cesarean section (60 +/- 6 c/min) and newborns delivered vaginally (53 +/- 16 c/min). CRS normalized for body weight was not significantly different between newborns after cesarean section and those delivered vaginally at H1-H2 (0.6 +/- 0.1 vs 0.7 +/- 0.1 ml/cmH2O/kg) and at H6-H7 (0.7 +/- 0.1 vs 0.8 +/- 0.3 ml/cmH2O/kg). At D3-D4, CRS was significantly greater than at H6-H7 in newborns after cesarean section (1.1 +/- 0.2 ml/cmH2O/kg, p less than 0.001) and in newborns delivered vaginally (1 +/- 0.1 ml/cmH2O/kg, p less than 0.02). We conclude that in newborns after cesarean section without tachypnea, the evolution in CRS is similar to that in newborns delivered vaginally.

Analysis of Variance↗
PubMed1986

A single orally administered dose of almitrine improves pulmonary gas exchange during exercise in patients with chronic air-flow obstruction.

To verify if the improvement in gas exchange observed at rest with almitrine in patients with chronic air-flow obstruction is maintained at exercise, we studied 10 patients on a randomized, crossover, double-blind exercise protocol. After assessment of steady state of their disease, patients with FEV 1 less than 1.5 L.s-1 and PaCO2 less than 70 mmHg cycled 8 to 11 min at 80% of their previously determined maximal O2 uptake. Blood gases, arterial lactate (La), expired ventilation, (VE), O2 uptake (Vo2), Co2 production (VCO2), heart rate (HR), and arterial blood pressure (BP) were measured at rest, at mid-exercise, at end-exercise, and at 2, 14, 15, and 35 min of recovery. We found that at all stages of the study PaO2 was significantly higher in those who had received almitrine than in those who had received placebo; the mean increment was 11.9 torr at rest, 8.9 at end-exercise, and 13.7 at 15 min of recovery. Changes in PaCO2 and arterial (H+) were the opposite of those in PaO2; at end-exercise PaCO2 was 5.9 torr lower in those who had received almitrine, and pH was 7.36 versus 7.32 in those who had received placebo. No significant difference was found at all stages of the study between drug and placebo with respect to VE, VO2, VCO2, HR, and BP. But the ventilatory equivalent for oxygen, VE/VO2, was slightly higher in those who had received almitrine than in those who had received placebo during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1984

Splanchnic vasomotor and metabolic adjustments to hypoxia and exercise in humans.

To determine whether hypoxia increases splanchnic vasoconstriction and impedes splanchnic metabolism during exercise, 11 subjects were exercised for 72 min at O2 uptake (VO2) of 1.8 1/min; 11% O2 was breathed during 30-50 min. Splanchnic blood flow (SBF), arterial and hepatic venous concentrations of indocyanine green (ICG), O2, CO2, metabolites, and catecholamines were determined in seven subjects; complete sets of all measurements were obtained from four. Arterial O2 content and tension fell from normal values to 12.3 ml/100 and to 32.2 Torr, respectively, during hypoxia; heart rate rose to 159 from 117 beats/min, arterial blood pressure was unchanged, and plasma norepinephrine (NE) and epinephrine (E) concentrations rose from 0.79 (NE) and 0.2 (E) ng/ml (normoxia) to 2.7 and 0.72, respectively, during hypoxia. SBF rose insignificantly from 1.14 (normoxia) to 1.35 l/min during hypoxia and fell significantly to 1.01 1/min after return to normoxia. Splanchnic VO2 was maintained at normal levels by increased extraction as hepatic venous O2 fell to 1.7 ml/100 ml and hepatic venous O2 tension to 7.5 Torr. Hepatic glucose release rose from 642 (normoxia) to 1,164 mg/min (hypoxia); lactate uptake increased from 0.26 to 2.1 mM/min; NE uptake rose from 417 to 1,508 ng/min, but hypoxia reduced ICG extraction by 28%. Thus hypoxia did not cause splanchnic vasoconstriction normally accompanying increases in HR and NE concentration or reductions in maximum VO2. SBF was maintained at a level sufficient to maintain all metabolic functions except ICG extraction.

Adult↗
PubMed1984

Hypoxemia increases plasma catecholamine concentrations in exercising humans.

To determine whether plasma catecholamine concentrations (a measure of sympathetic nervous activity [SNA]) rise above normoxic levels during exercise with hypoxemia, we exercised seven men for 15 min at three loads that required from 40 to 88% of maximal O2 uptake (VO2max). Subjects breathed room air on one day and 11-12% O2 on another with relative work loads corrected for the 24% fall in VO2max during hypoxemia. Hypoxemia caused large increments in norepinephrine (NE) concentration (radioenzyme technique) to 1.21 +/- 0.20 ng/ml (mean +/- SE), 2.79 +/- 0.38, and up to 5.90 +/- 0.75 (hypoxemia) compared with 0.89 +/- 0.06, 1.66 +/- 0.16, and 3.95 +/- 0.39 in normoxia at the three loads, respectively (P less than 0.001). Epinephrine (E) concentration approximately doubled (P less than 0.001) in hypoxemia at each load when compared with normoxic levels (i.e., 0.10 +/- 0.01 ng/ml, 0.23 +/- 0.03, and 0.46 +/- 0.06 in normoxia). However, hypoxemia did not significantly alter linear relationships between log plasma NE concentration and either heart rate (HR) or percent VO2max utilized, or between HR and percent VO2max. Thus NE concentration, like HR, appeared to reflect relative severity of exercise and overall SNA in both hypoxemia and normoxia. Above 40% VO2max during hypoxemia, circulating NE and E far exceeded levels known to have direct vasoconstrictor and metabolic effects in normoxic humans, but hypoxemia may blunt vasoconstriction in some regions.

Adult↗
PubMed1984

Nifedipine attenuates acute hypoxic pulmonary vasoconstriction in awake piglets.

The calcium channel blocker nifedipine was administered to awake piglets to determine the drug's potential efficacy as a pulmonary vasodilator in newborns. We hypothesized that nifedipine attenuates acute hypoxic pulmonary vasoconstriction in this age group. Hemodynamic and arterial blood gas measurements were made in 24 catheterized piglets, 10 +/- 3 days of age, while they breathed room air and then 12% O2, 4% CO2, and 86% N2 gas. Thirteen piglets were studied before and after infusions of 15 and 40 micrograms X kg-1 X min-1 of nifedipine prior to hypoxia to see if the drug prevents hypoxic pulmonary vasoconstriction. In 7 animals, nifedipine was administered after the onset of hypoxia to see if the drug reduces ongoing hypoxic pulmonary vasoconstriction. Nifedipine significantly increased heart rate (56 +/- 28%) and cardiac output (48 +/- 45%) and decreased systemic artery pressure (-11 +/- 7%) and systemic vascular resistance (-37 +/- 18%) compared with pretreatment values under normoxic conditions. Pulmonary artery pressure increased (28 +/- 21%) after nifedipine treatment, but total pulmonary resistance remained unchanged during normoxia. Nifedipine did not reduce pulmonary artery pressure compared with pretreatment values during hypoxia, but reduced the elevation in total pulmonary resistance associated with hypoxia by 45 to 99% in a dose-dependent manner. We conclude that nifedipine vasodilates the constricted pulmonary vasculature associated with hypoxia in newborns but that this effect is manifested primarily by a rise in cardiac output rather than by a reduction in pulmonary artery pressure in this age group.

Animals↗
PubMed1983

Iron repletion decreases maximal exercise lactate concentrations in female athletes with minimal iron-deficiency anemia.

We studied the effect of 2 weeks of iron therapy on exercise performance and exercise-induced lactate production in trained women athletes: six control subjects with normal parameters of iron status and nine with mild iron-deficiency anemia defined by low Fe/TIBC, ferritin, and minimally decreased Hgb values. Iron therapy improved the abnormal measures of iron status and low Hgb in the second group to normal. Exercise performance in a progressive work-exercise protocol on a bicycle ergometer to exhaustion was unchanged after iron therapy in both groups; however, blood lactate levels at maximum exercise in the iron-deficient group decreased significantly from 10.3 +/- 0.6 mmol/L before therapy to 8.42 +/- 0.7 after therapy (p less than 0.03). The control subjects did not significantly alter lactate levels after maximal exercise on iron compared to placebo: 8.3 +/- 0.8 mmol/L vs. 8.5 +/- 0.7. Although there was not a significant difference in maximum exercise performance after iron therapy, these data support animal experiments implying that iron may play a role in oxidative metabolism and that minimal decreases in Hgb may impair arterial oxygen content enough to affect aerobic metabolism. In addition, these findings may have important implications for competitive women athletes in whom mild iron deficiency may go unnoticed.

Acidosis↗
PubMed1982

Splanchnic vasoconstriction in heat-stressed men: role of renin-angiotensin system.

We conducted a two-part study to determine whether the renin-angiotensin system contributes to the rise in splanchnic vascular resistance (SVR) during heat stress (rectal temperature was raised 1 degree C). In experiment 1 (control) seven men on a normal salt diet were directly heated (water-perfused suits) for 40-50 min. Arterial pressure (85 Torr) was unchanged; plasma renin activity (PRA) rose from 102 to 239 ng angiotensin I.100 ml-1.3 h-1; and SVR increased 73% (from 63 to 109 units). Experiment 2 was a repetition of experiment 1 on the same subjects, except that propranolol (10 mg iv) was given at the onset of heating to block renin release. Propranolol attenuated the rise in heart rate and reduced mean arterial pressure from 82 to 72 Torr; it blocked the rise in PRA with heating in two subjects, reduced it in three, but increased it in two. Although changes in SVR paralleled those in PRA in three subjects, SVR still rose 60% (from 58 to 99 units) after PRA rise was blocked. In both experiments, plasma norepinephrine concentration rose indicating increased sympathetic nervous activity. During mild heat stress, increased PRA is not a major factor in the increase of SVR.

Adult↗
PubMed1982

Circulatory transport of oxygen in patients with chronic airflow obstruction exercising maximally.

Twenty patients with chronic bronchitis were exercised maximally on a bicycle ergometer. At exhaustion, arterial partial pressure of O2 (Pao2) decreased and that of CO2 (Paco2) increased in 8 patients (Subgroup 1). Arterial PO2 increased and Paco2 did not change in the remaining 12 patients (Subgroup 2). Forced expiratory volume in one second was lower in Subgroup 1 than in Subgroup 2. The decrease in arterial pH and the response of cardiac output were the same in both subgroups. Mixed venous PO2 decreased to 23 mm Hg or less in all patients in Subgroup 1 and in 3 patients in Subgroup 2; it stayed above 25 mm Hg in the remaining 9 patients. Our data imply that the ventilatory response to exercise is insufficient not only in Subgroup 1 but also in Subgroup 2 where the patients failed to hyperventilate in response to exercise-induced acidosis and that an unused oxygen reserve is still present at exhaustion in some patients with chronic airflow obstruction.

Aged↗