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Biomedical subjects

V Lafay

Publications and source records attributed to V Lafay.

At least 19 recordsLinked to original sources
PubMed2006

[The heart and underwater diving].

Cardiovascular examination of a certain number of candidates for underwater diving raises justifiable questions of aptitude. An indicative list of contraindications has been proposed by the French Federation of Underwater Studies and Sports but a physiopathological basis gives a better understanding of what is involved. During diving, the haemodynamic changes due not only to the exercise but also to cold immersion, hyperoxaemia and decompression impose the absence of any symptomatic cardiac disease. Moreover, the vasoconstriction caused by the cold and hyperoxaemia should incite great caution in both coronary and hypertensive patients. The contraindication related to betablocker therapy is controversial and the debate has not been settled in France. The danger of drowning makes underwater diving hazardous in all pathologies carrying a risk of syncope. Pacemaker patients should be carefully assessed and the depth of diving limited. Finally, the presence of right-to-left intracardiac shunts increases the risk of complications during decompressionand contraindicates underwater diving. Patent foramen ovale is a special case but no special investigation is required for its detection. The cardiologist examining candidates for underwater diving should take all these factors into consideration because, although underwater diving is a sport associated with an increased risk, each year there are more and more people, with differing degrees of aptitude, who wish to practice it.

Decompression Sickness↗
PubMed2006

[Implementation of the hypertension network in Mali (RHYTM)].

In view of the rising prevalence of arterial hypertension and its complications throughout sub-Saharan Africa including in rural areas, the Association of the Rural Doctors of Mali asked its NGO partner, Sant6 Sud, for assistance in setting up a medical network dedicated to hypertension. This report describes the implementation of the Mali Hypertension Network (French acronym, RHYTM) that involved three stages, i.e., physician training, development of appropriate protocols and field trials. The physician training stage was carried out over a one-week period and covered all the aspects of hypertension. In the second stage international guidelines were used as a basis for development of appropriate protocols for the rural setting. Field trials were conducted in the villages to verify the feasibility of the protocols and functionality of the network. Treatment of hypertension depends mainly on lifestyle and dietetic measures with emphasis on reducing salt intake. Drug treatment is based primarily on first-intention use of thiazidic diuretics. Management of this chronic pathology runs up against socio-cultural, economic and logistic obstacles. These problems are discussed and possible solutions are proposed. This preliminary experience will provide epidemiologic and clinical data on a sample population including more than 80000 people and explore the possibility of extending the network to other zones in this area of Africa.

Delivery of Health Care↗
PubMed1997

Doppler-echocardiography study of cardiac function during a 36 atm (3,650 kPa) human dive.

To determine the influence of a saturation dive on cardiac function, Doppler-echocardiographic measurements were compared at sea level and during a 36 atm (3,650 kPa) He-O2 dive (gas density: 7 g/liter) in four healthy men. Left ventricular systolic function was studied from time motion measurements. Transmitral flow (E:A ratio) and isovolumetric relaxation time were used to assess left ventricular diastolic function. Cardiac output was derived from systolic pulmonary and aortic valvular flows. Cardiac output decreased 4.4 +/- 0.8 vs. 5.9 +/- 1.2 liter/min at sea level) whereas stroke volume, left ventricular ejection fraction, atria and ventricular diameters remained unchanged. Thus, the decrease in cardiac output was attributed to bradycardia (56 +/- 8 vs. 73 +/- 9 beats/min at sea level) which probably resulted from the slight hyperoxia (PI(O2), 0.4 atm). We found no evidence of left ventricular diastolic dysfunction. nor did we find valvular regurgitation or pulmonary hypertension. We conclude that Doppler-echocardiography can be used safely to investigate cardiac function during human saturation dives. Our results suggest that a 36 atm He-O2 dive does not modify cardiac or systolic and diastolic function except for a slight decrease in cardiac output correlated to bradycardia.

Adult↗
PubMed1997

[Changes in cardiac function during recreational diving].

Underwater diving is a widely practised leisure activity. As cardiac patients may wish to participate, cardiologists should be aware of potential changes of cardiac function during diving. Multiple factors may affect haemodynamics. Firstly, changes in pressure, secondary to ventilation of a high density gas mixture which increases afterload. Hyperoxia is the principal factor which slows the heart rate, a commonly observed phenomenon. Excitability and conduction speed may be modified by the increase in hydrostatic pressure. During decompression, gaseous pulmonary embolism may increase right heart pressures and cause a paradoxical embolism may increase right heart pressures and cause a paradoxical embolism in patients with a right-to-left shunt. Immersion increases the preload. Exposure to cold also plays a role increasing afterload and slowing the heart rate. These factors may disturb cardiac function and expose cardiac patients to accidents during underwater diving.

Animals↗
PubMed1996

Electrocardiogram changes during positive pressure breathing in rabbits.

Positive pressure breathing produced by mechanical ventilation with an expiratory threshold load (ETL) may modify electrocardiogram (ECG) complexes independently of any recording artefact due to lung volume changes. Anaesthetized, paralyzed rabbits were treated for about 2 h, then killed. In intact then vagotomized animals two situations were studied successively. Firstly, positive inspiratory pressure breathing, and secondly, positive inspiratory plus expiratory pressure breathing by adding ETL to mechanical ventilation. Arterial blood gases were measured and held constant throughout the challenge. Oesophageal pressure, giving indirect measurement of intrathoracic pressure, arterial blood pressure, blood flows in abdominal aorta and inferior vena cava and standard ECG recordings were made at baseline condition during mechanical ventilation, then at the end of a 10-min period of ETL breathing. The ETL breathing decreased arterial blood pressure significantly and reduced arterial and venous blood flows in the same proportion. No change in the duration of ECG complexes was noticed. However, ETL markedly reduced the amplitude of P- and T-waves, but not that of R-wave, an effect significantly accentuated after vagotomy. The ETL breathing increased the T-vector angle, with no associated change in QRS vector angle. The present animal investigations revealed that positive pressure breathing modifies the ECG independently of the consequences of ETL-induced lung volume changes. We speculate that the changes in P- and T-wave amplitude may have resulted from a reduced transmural pressure gradient between the epicardium and endocardium.

Animals↗
PubMed1996

Survey of the seroprevalence of Bartonella quintana in homeless people.

Trench fever is caused by Bartonella (Rochalimaea) quintana, a small gram-negative rod that is transmitted by body lice. Recently, B. quintana infections in homeless patients have been reported in the United States and Europe. From October 1993 to October 1994, the seroprevalence of antibodies to B. quintana was assessed by indirect immunofluorescence in a prospective study of 221 nonhospitalized homeless people, 43 hospitalized homeless patients (cases), 250 blood donors, and 57 hospitalized matched controls. Four (1.8%) of 221 nonhospitalized homeless people tested had titers of > 1:100. Of the 43 cases, seven (16%) had serological titers of > or = 1:100. None of the 250 serum samples from blood donors contained antibodies to B. quintana. The presence of antibodies to B. quintana in cases was significantly associated with the presence of body lice, exposure to cats, headaches, eastern European origin, and pain in the legs. This study demonstrates the presence of antibodies to B. quintana in the homeless population and should alert physicians that B. quintana might be an etiologic agent of fever in homeless patients.

Animals↗
PubMed1996

[Manipulations of cervical vertebrae and trauma of the vertebral artery. Report of two cases].

Vertebrobasilar-distribution stroke is a rare but sometimes severe complication of chiropractic neck manipulation. We report two patients with dissections of the vertebral arteries authenticated two and six days after the cervical manipulation. In the first case, a Wallenberg's syndrome occurred due to a dissection of the right intracranial vertebral artery; the patient was treated with anticoagulant therapy but little improvement of the disorder was noted. The second patient had transitory neurologic manifestations which led to the discovery of an intimal tear of the ostium of the right vertebral artery with a floating clot. Further embolic complications were avoided by performing a venous bypass between the right common carotid and the vertebral artery at the base of the skull. Therapists should be aware of vertebrobasilar complications after spinal manipulations and should ask for early explorations (brain CT, cerebral angiography) to institute rapidly the most appropriate treatment.

Aortic Dissection↗
PubMed1995

ECG changes during the experimental human dive HYDRA 10 (71 atm/7,200 kPa).

Electrocardiogram (ECG) analysis was performed in three human divers during a 71 atm (7,200 kPa) saturation dive (COMEX HYDRA 10 experiment). The inhaled gas mixture was slightly hyperoxic; its composition was basically helium and oxygen. Hydrogen was introduced during compression and its partial pressure reached 20 atm. ECG changes were the same in the three divers. Marked bradycardia rapidly appeared at the beginning of compression, then this response adapted throughout the dive. P-R, QRS, and Q-T intervals and the S-T segment did not change significantly. The QRS axis remained stable. However, a rightward shift occurred in P and T vector angles. These changes were correlated with time and gas density, respectively. The modifications of ventricular repolarization during compression are similar to those we observed during the HYDRA 9 COMEX dive. They may correspond to changes in duration of myocardial cell repolarization due to increased intrathoracic pressure changes with dense-gas breathing. A marked global diminution of voltage occurred during the decompression period. This suggests that accumulation of micro bubbles in tissues may influence the impedance, causing an artifact in the amplitude of ECG complexes.

Adult↗
PubMed1995

[Physical training and blood pressure].

The effects of exercise training on blood pressure (BP) are reviewed. BP rises during exercise and lowers in the post-exercise period. Regular physical training result in a significant lowering of BP at rest as long as the training is continued. Moreover exercise training result in a BP lowering during exercise which is greater in hypertensive patients than in normotensive subjects. A favourable effect is observed also on ambulatory blood pressure, but the night-time blood pressure is not lowered. The mechanisms of training-induced changes of BP are not sufficiently known. The exercise training seems act on systemic vascular resistance, plasma catecholamine, PGE2 and taurine levels, renin-angiotensin-aldosterone system. As adequate physical training can reduce BP, we can consider it is a non pharmacological treatment of hypertension: mainly for border lines, labile and mild hypertensives patients. For certain hypertensive patients, some sports can be permitted when no target organ is involved.

Adolescent↗
PubMed1991

[Development of echocardiographic and Doppler parameters after orthotopic cardiac transplantation, except during rejection periods].

The aim of this study was to evaluate spontaneous changes of Doppler and echocardiographic parameters of cardiac transplants in the absence of rejection. Based on 258 recordings representing the follow up of 30 patients after orthotopic cardiac transplantation in the absence of histological signs of rejection on biopsy within 24 hours, we tried to define: the evolution of these parameters from the first postoperative week to after the 30th month (average 12 months); the Doppler echocardiographic values of "normal" transplants: the values observed one year after surgery were compared with a control group age-matched to the donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

[Results of cardiac surgery in patients over 70 years of age. Apropos of a retrospective study of 170 patients].

The ever increasing age of the general population and the frequency of coronary and aortic lesions in patients aged 70 or older make cardiac surgery in the elderly a topic of current interest. In a retrospective study of 170 cases the overall mortality rate was 14 p. 100 (4.7 p. 100 in 1986). During the past two years (1985 and 1986), the mortality rates in patients with coronary disease who underwent elective surgery were 10 p. 100 and 4 p. 100 respectively. Emergency surgery (left coronary trunk and unstable angina excluded) and associated operations on the heart made the prognosis worse with overall mortality rates of 13 p. 100 and 15 p. 100 respectively (9 p. 100 in 1985, 10 p. 100 in 1986). In aortic valve surgery, hospital mortality rates were 28 p. 100 in 1985 and 6 p. 100 in 1986. Post-operative morbidity was high (52 p. 100 of patients) and consisted mostly of respiratory and neurological complications (14.7 p. 100 and 9.4 p. 100 respectively of all patients). Only 4 p. 100 of the patients developed peri-operative myocardial infarction. Functional results were satisfactory in both coronary disease and heart valve disease patients. The survival rate at 4 years was 74.5 +/- 10 p. 100 globally and 87.3 +/- 9 p. 100 in coronary patients operated upon electively. Thus, the considerable advances in surgical techniques and post-operative intensive care achieved during the last few years have significantly improved the results obtained in this population.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMedDate not supplied

Visits to the emergency room for asthma attacks and short-term variations in air pollution. A case-crossover study.

BACKGROUND: The 'case-crossover' design is a strategy fitted to studying transient effects of intermittent exposure on acute-onset disease occurring shortly after exposure. It has the important advantage of eliminating most confounding variables, allowing a stronger causality inference. OBJECTIVES: The objective of the study was to evaluate the relationships between emergency room (ER) visits for asthma attacks and gaseous air pollution changes. METHODS: The study included 549 individuals, 3-49 years old, visiting the ER during 1 year. Exposure to gaseous air pollutants (SO2, NO2, O3) on the same day and up to 4 days before was computed according to the patient's address. The statistical analysis included meteorological data as potential confounding variables. RESULTS: No association could be shown between ER visits and SO2 or NO2 levels. In contrast, there was a statistically significant association between ER visits and mean O3 levels, on the day of admission and also on D -2 and D -3. For an increase of 10 microg/m3, the risk of requiring an ER admission increased by 6-10%. CONCLUSIONS: Using this new strategy, we confirmed that ozone changes lead to a moderate increase in risk of requiring an ER admission in asthmatic subjects.

Adolescent↗