31 research outputs found
Phase I dynamics of cardiac output, systemic O2 delivery, and lung O2 uptake at exercise onset in men in acute normobaric hypoxia
No full textWe tested the hypothesis that vagal withdrawal plays a role in the rapid (phase I) cardiopulmonary response to exercise. To this aim, in five men (24.6 +/-3.4 yr, 82.1 +/-13.7 kg, maximal aerobic power 330 +/- 67 W), we determined beat-by-beat cardiac output (Q˙), oxygen delivery (Q˙aO2), and breath-by-breath lung oxygen uptake (V˙O2) at light exercise (50 and 100 W) in normoxia and acute hypoxia (fraction of inspired O2 +/- 0.11),because the latter reduces resting vagal activity. We computed Q˙ from stroke volume (Qst, by model flow) and heart rate (fH, electrocardiography), and Q˙aO2 from Q˙ and arterial O2 concentration. Double exponentials were fitted to the data. In hypoxia compared with normoxia, steady-state fH and Q˙ were higher, and Qst and V˙ O2 were unchanged.Q˙aO2 was unchanged at rest and lower at exercise. During transients, amplitude of phase I (A1) for V˙O2 was unchanged. For fH, Q˙and Q˙aO2, A1 was lower. Phase I time constant (tau1) forQ˙aO2 and V˙O2 was unchanged. The same was the case for Q˙ at 100 W and for fH at 50 W. Qst kinetics were unaffected. In conclusion, the results do not fully support the hypothesis that vagal withdrawal determines phase I, because it was not completely suppressed. Although we can attribute
the decrease in A1 of fH to a diminished degree of vagal withdrawal
in hypoxia, this is not so for Qst. Thus the dual origin of the phase I of Q˙ and Q˙aO2, neural (vagal) and mechanical (venous return increase by muscle pump action), would rather be confirmed
Cardio-pulmonary adaptations to prolonged bed rest in humans
No full textCette thèse inclut trois études. La première décrit l'évolution temporelle de la décroissance de la consommation maximale d'oxygène ( V'O2max) durant alitement prolongé (AP); la deuxième explore l'impact de l'AP sur les régulations autonomes cardiovasculaires; la troisième décrit les effets de la posture sur la réponse cardiopulmonaire. Il apparaît que : 1) La V'O2max décroit de manière asymptotique, avec deux phases, l'une rapide, pendant les deux premières semaines d'AP, l'autre lente, avec une constante de temps de 80 jours. La capacité d'exercice, quoique réduite, est ainsi maintenue lors de voyages spatiaux de longue durée, permettant aux astronautes d'atteindre Mars étant encore opérationnels. 2) Les paramètres toniques des régulations autonomes cardiaques sont altérés lors d'AP, tandis que les fonctions oscillatoires restent conservées. 3) L'AP amplifie les effets posturaux sur le volume d'éjection. Le maintien du débit cardiaque dépend d'une augmentation de fréquence. La consommation d'oxygène augmente pour altération du contrôle moteur
Détermination du débit cardiaque par la méthode du Modelflow appliquée à une artère périphérique au repos et à l'exercice modéré
No full textCette thèse comporte deux études menées dans le but de valider le Modelflow® comme méthode de détermination du débit cardiaque (Q') battement-par-battement chez l'humain. Dans la première étude, nous comparons les valeurs de Q' obtenues par le Modelflow® à partir de profils de l'onde pulsatile enregistrés simultanément au doigt et à l'artère radiale, au repos et à l'exercice. Les profils pulsatiles périphériques se traduisent par des valeurs de Q' systématiquement plus élevées que celles obtenues au niveau artériel. Dans la deuxième étude, nus avons calibré Q' par Modelflow® appliqué aux profils pulsatiles au doigt, en utilisant la technique d'acétylène en circuit-ouvert, au repos et à divers niveaux d'effort à l'état stationnaire. Les facteurs de correction calculés étaient indépendants du niveau d'effort. L'utilisation de Modelflow® comme méthode fiable pour la mesure de Q' au repos et à l'exercice est possible après correction par rapport à une méthode indépendante
Correction of cardiac output obtained by Modelflow® from finger pulse pressure profiles with a respiratory method in humans
No full textThe beat-by-beat non-invasive assessment of cardiac output (Q˙ , litre · min−1) based on the arterial pulse pressure analysis called Modelflow® can be a very useful tool for quantifying the cardiovascular adjustments occurring in exercising humans. ˙Q was measured in nine young subjects at rest and during steady-state cycling exercise performed at 50, 100, 150 and 200 Wby using Modelflow® applied to the Portapres® non-invasive pulse wave (˙QModelflow) and by means of the open-circuit acetylene uptake (˙QC2H2 ). ˙Q values were correlated linearly (r=0.784), but Bland–Altman analysis revealed that mean ˙QModelflow − ˙QC2H2 difference (bias) was equal to 1.83 litre · min−1 with an S.D. (precision) of 4.11 litre · min−1, and 95% limits of agreement were relatively large, i.e. from −6.23 to +9.89 litre · min−1. ˙QModelflow values were then multiplied by individual calibrating factors obtained by dividing ˙QC2H2 by ˙QModelflow for each subject measured at 150 Wto obtain corrected˙Q Modelflow (˙Qcorrected) values. ˙Qcorrected values were compared with the corresponding ˙QC2H2 values, with values at 150 Wignored. Data were correlated linearly (r=0.931) and were not significantly different. The bias and precision were found to be 0.24 litre · min−1 and 3.48 litre · min−1 respectively, and 95% limits of agreement ranged from −6.58 to +7.05 litre · min−1. In conclusion, after correction by an independent method, Modelflow® was found to be a reliable and accurate procedure for measuring ˙Q in humans at rest and exercise, and it can be proposed for routine purposes
Cardiac output by Modelflow® method from intra-arterial and fingertip pulse pressure profiles
No full textModelflow®, when applied to non-invasive fingertip pulse pressure recordings, is a poor predictor of cardiac output (Q˙ , litre · min−1). The use of constants established from the aortic elastic characteristics, which differ from those of finger arteries, may introduce signal distortions, leading to errors in computing Q˙ .We therefore hypothesized that peripheral recording of pulse pressure
profiles undermines the measurement of Q˙ with Modelflow®, so we compared Modelflow® beat-by-beat ˙Q values obtained simultaneously non-invasively from the finger and invasively from the radial artery at rest and during exercise. Seven subjects (age, 24.0+−2.9 years; weight, 81.2+−12.6 kg) rested, then exercised at 50 and 100 W, carrying a catheter with a pressure head in the left radial artery and the photoplethysmographic cuff of a finger pressure device on the third and fourth fingers of the contralateral hand. Pulse pressure from both devices was recorded simultaneously and stored on a PC for subsequent ˙Q computation. The mean values of systolic, diastolic and mean arterial pressure at rest and exercise steady state were significantly (P<0.05) lower from the finger than the intra-arterial catheter. The corresponding mean steady-state ˙Q obtained from the finger (˙Qporta) was significantly (P<0.05) higher than that computed from the intra-arterial recordings (˙Qpia). The line relating beat-by-beat ˙Qporta and ˙Qpia was y=1.55x−3.02 (r2 =0.640). The bias was 1.44 litre · min−1 and the precision was 2.84 litre · min−1. The slope
of this line was significantly higher than 1, implying a systematic overestimate of ˙Q by ˙Qporta with respect to ˙Qpia. Consistent with the tested hypothesis, these results demonstrate that pulse
pressure profiles from the finger provide inaccurate absolute ˙Q values with respect to the radial artery, and therefore cannot be used without correction with a calibration factor calculated previously by measuring ˙Q with an independent method
Hospital-based injury data from level III institution in Cameroon: Retrospective analysis of the present registration system
No full textBackgroundData on the epidemiology of trauma in Cameroon are scarce. Presently, hospital records are still used as a primary source of injury data. It has been shown that trauma registries could play a key role in providing basic data on trauma. Our goal is to review the present emergency ward records for completeness of data and provide an overview of injuries in the city of Limbe and the surrounding area in the Southwest Region of Cameroon prior to the institution of a formal registration system.MethodsA retrospective review of Emergency Ward logs in Limbe Hospital was conducted over one year. Records for all patients over 15 years of age were reviewed for 14 data points considered to be essential to a basic trauma registry. Completeness of records was assessed and a descriptive analysis of patterns and trends of trauma was performed.ResultsInjury-related conditions represent 27% of all registered admissions in the casualty department. Information on age, sex and mechanism of injury was lacking in 22% of cases. Information on vital signs was present in 2% (respiratory rate) to 12% (blood pressure on admission) of records. Patient disposition (admission, transfer, discharge, or death) was available 42% of the time, whilst location of injury was found in 84% of records. Road traffic injury was the most frequently recorded mechanism (36%), with the type of vehicle specified in 54% and the type of collision in only 22% of cases. Intentional injuries were the second most frequent mechanism at 23%.ConclusionThe frequency of trauma found in this context argues for further prevention and treatment efforts. The institution of a formal registration system will improve the completeness of data and lead to increased ability to evaluate the severity and subsequent public health implications of injury in this region
ETHICS OF HUMAN GENETIC STUDIES IN SUB-SAHARAN AFRICA: THE CASE OF CAMEROON THROUGH A BIBLIOMETRIC ANALYSIS
No full textSimultaneous determination of the kinetics of cardiac output, systemic O(2) delivery, and lung O(2) uptake at exercise onset in men
No full textWe tested whether the kinetics of systemic O(2) delivery (QaO(2)) at exercise start was faster than that of lung O(2) uptake (Vo(2)), being dictated by that of cardiac output (Q), and whether changes in Q would explain the postulated rapid phase of the Vo(2) increase. Simultaneous determinations of beat-by-beat (BBB) Q and QaO(2), and breath-by-breath Vo(2) at the onset of constant load exercises at 50 and 100 W were obtained on six men (age 24.2 +/- 3.2 years, maximal aerobic power 333 +/- 61 W). Vo(2) was determined using Gronlund's algorithm. Q was computed from BBB stroke volume (Q(st), from arterial pulse pressure profiles) and heart rate (f(h), electrocardiograpy) and calibrated against a steady-state method. This, along with the time course of hemoglobin concentration and arterial O(2) saturation (infrared oximetry) allowed computation of BBB QaO(2). The Q, QaO(2) and Vo(2) kinetics were analyzed with single and double exponential models. f(h), Q(st), Q, and Vo(2) increased upon exercise onset to reach a new steady state. The kinetics of QaO(2) had the same time constants as that of Q. The latter was twofold faster than that of Vo(2). The Vo(2) kinetics were faster than previously reported for muscle phosphocreatine decrease. Within a two-phase model, because of the Fick equation, the amplitude of phase I Q changes fully explained the phase I of Vo(2) increase. We suggest that in unsteady states, lung Vo(2) is dissociated from muscle O(2) consumption. The two components of Q and QaO(2) kinetics may reflect vagal withdrawal and sympathetic activation
Acute glycaemic effects of co-trimoxazole at prophylactic dose in healthy adults
No full textAbstract Background Cases of severe hypoglycaemia were reported in HIV/AIDS patients receiving high dose of the sulfonylurea co-trimoxazole for opportunistic infections. Whether co-trimoxazole at prophylactic dose would induce similar side effects is unknown. We aimed to investigate the acute effects of co-trimoxazole at prophylactic dose on glucose metabolism in healthy adults. Methods We enrolled 20 healthy volunteers (15 males and 5 females) aged 23.0 (SD 2.0) years, with mean BMI of 22.3 (SD 3.6) Kg/m 2 with normal glucose tolerance, hepatic and renal function. We performed a 75-g oral glucose tolerance test (OGTT) with and without concomitant oral co-trimoxazole administered 60 min before the test. Blood glucose response was measured using a capillary test at baseline and at 30, 60, 90, 120 and 180 min following oral glucose load on the two occasions. C-peptide response was also measured. Absolute values of blood glucose and C-peptide with and without co-trimoxazole were compared using the Wilcoxon test. Results During the OGTT without co-trimoxazole (control) vs. the OGTT with co-trimoxazole (test), the glycaemia varied from 4.83 (SD 0.39) mmol/l vs. 4.72 (SD 0.28) mmol/l at T0 (P = 0.667), to 8.00 (SD 1.11) mmol/l vs. 7.44 (SD 0.78) mmol/l at T30 (P = 0.048), 8.00 (SD 1.17) mmol/l vs. 7.67 (SD 1.00) mmol/l at T60 (P = 0.121), 7.33 (SD 0.94) mmol/l vs. 7.11 (SD 0.83) mmol/l at T90 (P = 0.205), 6.78 (SD 1.00) mmol/l vs. 6.67 (SD 1.00) mmol/l at T120 (P = 0.351) and 4.72 (SD 1.39) mmol/l vs. 4.72 (SD 1.56) mmol/l at T180 (P = 0.747). The ratio of area under the glycaemia curve during the control and test investigation was 96.7 %, thus a 3.3 decreased glycaemic response (p = 0.062). A decrease of glycaemia by more than 10 % occurred in 6/20 participants at T30, 7/20 participants at T60 and 1/20 participant at T30 and T60. None of the volunteers experienced co-trimoxazole-induced hypoglycaemia. At the same time, the C-peptide response during the control vs. the test investigation varied from 278.1 (SD 57.5) pmol/l vs. 242.8 (SD 42.5) pmol/l at T0 (P = 0.138), to 1845.6 (SD 423.6) pmol/l vs. 2340.6 (SD 701.3) pmol/l at T60 (P = 0.345) and 1049.8 (SD 503.1) pmol/l vs. 1041.63 (SD 824.21) pmol/l at T180 (P = 0.893). Conclusion Ninety minutes after its administration, co-trimoxazole induced a significant reduction of the early glycaemic response to oral glucose in parallel with a 27-% increase in insulin secretory response. Co-trimoxazole induced within 120 min a more than 10-% blood glucose reduction in 2/3 of participants. However none of the volunteers experienced hypoglycaemia
Heart Rate Variability of Patients with Respect to Induction of Anesthesia in Gynaecologic Surgery: A Cross Sectional Study in Yaounde (Cameroon)
No full textABSTRACT
Introduction. Heart rate variability (HRV) is a well-established quantitative predictor of clinical cardiac events and thus may be an indispensable tool of the anaesthetist, thus motivating our study, with the aim of analysing HRV at induction of anaesthesia. Materials and Methods. We carried out a prospective cross-sectional study from the November 1st, 2019 to December 31st, 2021 in the surgical theatres of the Yaounde Gyneco-Obstetric and Pediatric Hospital (YGOPH). All patients presenting for gynaecologic surgery under general anaesthesia, with stable haemodynamic parameters were included. HRV of patients was measured at rest, and in 5-minute segments during induction. Results were analysed with the aid of KUBIOS software. HRV parameters were compared with baseline resting values and presented in tabular form. Results. Forty-three patients were included, 25 patients being under the age of 40 years. Induction agents included Propofol, Thiopental and Ketamine in the ratio 38:4: 1. There was a general decrease in HRV of patients, following intravenous induction of aneasthesia. LF/HF (low frequency on high frequency) ratio was significantly increased in the FFT spectrum, suggesting significant sympathetic predorminance over parasympathetic input on the HRV. Advancing age (above 40), obesity, anaemia and hypertension led to decreased HRV with varied contributions of PNS and SNS to individual effects seen. Conclusion. HRV in gynaecologic patients decreases with intravenous induction of anaesthesia. Comorbidities further decrease HRV during induction of anaesthesia with various contributions of the sympathetic and parasympathetic system.
RÉSUMÉ
Introduction. La variabilité de la fréquence cardiaque (VFC)est un prédicteur quantitatif bien établi des événements cardiaques cliniques et peut donc être un outil indispensable pour l'anesthésiste. Le But de Notre étude est d'analyser la VFC lors de l'induction de l'anesthésie. Méthodologie. Nous avons réalisé une étude transversale prospective du 1er novembre 2019 au 31 décembre 2021 dans les salles d'opération de l'hôpital gynéco-obstétrique et pédiatrique de Yaoundé (YGOPH). Tous les patients se présentant pour une chirurgie gynécologique sous anesthésie générale, avec des paramètres hémodynamiques stables, ont été inclus. La VFC des patients a été mesurée au repos et par segment de 5 minutes pendant l'induction. Les résultats ont été analysés à l'aide du logiciel KUBIOS. Les paramètres de VFC ont été comparés aux valeurs de repos de référence et présentés sous forme de tableau. Résultats: Quarante-trois patients ont été inclus, dont 25 avaient moins de 40 ans. Les agents d'induction comprenaient le propofol, le thiopental et la kétamine dans un rapport de 38:4:1. On a observé une diminution générale de la VFC des patients après l'induction intraveineuse de l'anesthésie. Le ratio LF/HF (basse fréquence sur haute fréquence) a augmenté de manière significative dans le spectre FFT, suggérant une prédominance sympathique significative sur l'entrée parasympathique la VFC. L'âge avancé (plus de 40 ans), l'obésité, l'anémie et l'hypertension ont entraîné une diminution de la VFC .. Conclusion: La VFC chez les patients gynécologiques diminue lors de l'induction intraveineuse de l'anesthésie. Les comorbidités diminuent davantage l'HRV lors de l'induction de l'anesthésie, avec diverses contributions du système sympathique et parasympathique
