[Cooling shell in renal transplantation. Thermometric evaluation of a prototype]

We have developed a cooling system for renal transplants designed to eliminate the second period of warm ischaemia corresponding to the vascular anastomosis phase of renal transplantation. This is an autonomous and independent system which forms a shell around the transplant. Following application of the system, cooling is achieved by refrigeration of a Multitherm sponge contained in the wall of the shell. The thermometric characteristics of a prototype were evaluated in vitro and in vivo in pigs. This system allows the kidney to be preserved at a temperature of less than 10 degrees C for 1 hour without inducing any risk of lesions of the renal surface. Human applications should be developed in the near future.

Proton magnetic resonance spectroscopy of human amniotic fluids sampled at 17-18 weeks of pregnancy in cases of decreased digestive enzyme activities and detected cystic fibrosis

Low digestive enzyme activities in human amniotic fluid can be observed in normal and disease-affected pregnancies: cystic fibrosis, trisomy 21, intestinal atresia. Amniotic fluids were analyzed by proton nuclear magnetic resonance (NMR) spectroscopy in order to specify prenatally the etiology of low digestive enzyme activities observed at 17-18 weeks of amenorrhea. A total of 114 amniotic fluid samples were collected at 17-18 weeks of amenorrhea. Karyotyping and assays of digestive enzyme activities were performed in all cases. Samples were divided into six groups according to enzyme activities and pathology. Proton spectra were retrospectively recorded. Many compounds, such as amino acids and carboxylic acids, were detected by NMR. The same resonance intensities (normalized to creatinine) were observed in the six groups. Nevertheless, an unidentified resonance at 1.05 ppm was detected in seven out of 13 cases of cystic fibrosis affected fetuses. The NMR spectra demonstrated the stability of the amniotic fluid composition at 17-18 weeks of amenorrhea, even when the fetus was affected by a disease such as trisomy 21 or intestinal atresia. The resonance associated with most cases of cystic fibrosis should be further investigated.

Lipoproteins in heart transplantation: proton magnetic resonance spectroscopy of plasma

Despite the major improvement in immunosuppressive therapy, noninvasive detection of heart graft rejection remains a challenge. As lipoproteins are involved in several immunomodulation mechanisms, we studied their proton NMR spectra in plasma from patients after heart transplantation. NMR data were compared to clinical and functional evaluation of rejection process. The total linewidth (TLW) of methyl and methylene peaks, mainly arising from lipoproteins, were significantly lower for patients without a rejection process than for patients before surgery and patients with evidences of a rejection process. When TLW values are referred to TLW on the 8th day for each patient, the sensitivity and the specificity of the test are increased, with resulting positive and negative predictive values of 90 and 91%, respectively. The results obtained on more than 400 samples from 46 patients justify the use of proton NMR spectroscopy as a clinical tool.

Heart and unilateral lung transplantation in patients with end-stage cardiopulmonary disease and previous thoracic operations

Orthotopic en bloc transplantation of the heart and one lung has been done in two patients with end-stage cardiopulmonary disease and a prior thoracic operation. The first patient had undergone right pulmonary thromboembolectomy with caval ligation 5 years earlier, and the second had had left lower lobectomy for bronchiectasis 15 years before the heart and contralateral lung transplantation. Surgical procedures followed the techniques that had been developed in animals. Transplantation of the unoperated contralateral lung made it possible to avoid dissection in the obliterated pleural space and to minimize bleeding, which simplified the procedure considerably. Dramatic reduction in pulmonary artery pressure and improved respiratory function allowed both patients to be weaned from cardiopulmonary bypass without problems. Although the first patient died of liver and renal failure soon after the operation, an intact cough reflex facilitated recovery in the second patient, who has been discharged with essentially normal respiratory function. This report describes heart and unilateral lung transplantation as a procedure of choice for patients with extensive pleural adhesions that made total cardiopulmonary replacement unfeasible.

Assessment of the optimal atrio-ventricular delay in DDD paced patients by impedance plethysmography

The beneficial haemodynamic effects of sequential atrioventricular (AV) pacing have been clearly established and are dependent on the AV delay and pacing rate. However, the optimal AV delay is difficult to determine in each particular patient. We used a modified impedance plethysmographic method to assess variations in stroke volume for different AV delay and pacing rate settings. Impedance measurements showed a good correlation with CO2 rebreathing stroke volume measurements in VVI patients. Impedance variations were then used to set the optimal AV delay at different pacing rates in DDD patients. The inverse relationship between the optimal AV delay and the pacing rate has been accurately identified in most of the patients but is not predictable. In all cases, the cardiac output was higher in DDD mode at the optimal AV delay than in VVI mode. In some patients with a damaged myocardium, the stroke volume appeared to be highly sensitive to multiple AV delay settings. Impedance plethysmography can permit such repetitive non-invasive quick measurements, increasing the accuracy of optimal AV delay determination and is well suited for routine examination of patients with cardiac dual chamber pacemakers.

A dynamic analysis of the ventilatory response to hypoxia in man

1. The dynamics of the ventilatory response to isocapnic hypoxia were studied in seven healthy subjects using four different levels of hypoxia, (inspired oxygen pressures, PI,O2 equal to 110, 100, 80 and 60 mmHg) successively increasing and decreasing stepwise. 2. Five such progressions were performed for each subject, corresponding to five different durations of the steps (t) ranging between 0.33 and 5.00 min. The overall duration of one test (T) was taken as the sum of the seven successive PI,O2 hypoxic steps (t) plus one step t of air breathing. Thus, the values of T ranged between 2.6 and 40.0 min. 3. End-tidal CO2 pressure was maintained constant (+/- 1 mmHg) throughout the test by manipulation of inspired CO2 pressure. 4. We measured, as a function of T, (i) the magnitude of the loops formed by the ventilatory response curves (PA,O2-VE) as measured by their surface area (S), (ii) the magnitude of ventilatory response to each rising hypoxic step, and (iii) the difference between resting VE and VE observed at PA,O2 equal to 50 mmHg (delta V50). On average, we found one maximum in absolute value of S at T = 8 min and one minimum at T = 12 min, along with two maxima of ventilatory response at T values of 8 and 24 min. 5. The same measurements were made on tidal volume response curves (PA,O2-VT) and ventilatory frequency response curves (PA,O2-f): on average we observed two non-significant peaks in the progression with T of VT and S(VT) and two significant peaks in that of delta VT,50 for T = 8 and T = 24 min. No significant peak was observed in the progression with T of f curve parameters. 6. These results are discussed together with the current dynamic model of the ventilatory control system, which includes a central neural controller with no dynamics of its own and a linear response to chemoreceptor inputs. We discuss the physiological meaning of a negative loop area in relation to the previously described depressant effect of hypoxia upon the brain stem. 7. We conclude that the dynamics of the controlling neuronal network are responsible for the observed singularities which result from differential sensitivity properties of the controller. We propose the existence of discrete excitatory states of the controller as a possible explanation of the shape of the steady-state response curve to hypoxia and of the loop variations.

A dynamic analysis of the ventilatory response to carbon dioxide inhalation in man

1. The dynamics of the ventilatory response to carbon dioxide inhalation were studied in ten healthy young men using four different inspired fractions of carbon dioxide (FI, CO2) in air (0.015, 0.030, 0.045 and 0.060) successively increasing and decreasing stepwise. 2. Seven such different progressions were performed for each subject and each of seven different durations of the steps (t) ranging between 0.1 (i.e. one ventilatory cycle) and 10 min ('steady-state' conditions). The overall duration of one test (T) was taken as the sum of the seven successive FI, CO2 steps (t) plus one step, t, of air breathing. Thus, the values of T ranged between 0.8 (i.e. eight ventilatory cycles) and 80 min. Three subjects were tested twice. 3. We measured, as a function of T, the magnitude of the loops formed by the curves PA, CO2-VE and the value of the highest ventilatory response (VE max) to each progression. For all ten subjects, both functions had two maxima, one for T values of 2.6 or 8.0 min and one for T values of 24 or 40 min, and one minimum at T equal to 12 min. 4. The same measurements were made on tidal volume-response curves (PA, CO2-VT) and ventilatory frequency-response curves (PA, CO2-f) and yielded the same results except for the ventilatory frequency-response curves, for which we only found a statistically insignificant single maximum for T values of 24 or 40 min. 5. The locations of the maxima in loop magnitude and VE max were similar in duplicate tests in three subjects, whereas the quantitative values of these variables showed wide differences. 6. We compared our results with what is expected from the current linear dynamic model of ventilatory control submitted to the same forcing function: the first maximum in the loop magnitude is predicted by the model, but the second is not. The model shows no peak in the evolution of VE max. 7. We conclude that controlled system dynamics, which are the only ones included in dynamic models of ventilatory control, cannot by themselves account for our observations, and that one should take into consideration the dynamics of the controlling neuronal network.

Arterial elasticity and physical working capacity in young men

We have tested the hypothesis that there is a positive relation between arterial elasticity and physical working capacity (PWC) at a given age. The subjects were 28 young men, 16-18 yr old. Arterial elasticity was evaluated by measuring the carotid to femoral pulse-wave velocity (c) at rest. The slope, S(c) of the relation between c and the diastolic blood pressure was studied during a cold pressor test to test vascular reactivity. The relationship between heart rate (HR) and work load was determined using a cycle ergometer; the variables measured were the slope of this relation S(PWC) and the power output at a HR of 170 min-1 (PWC170). The PWC170 ranged from 1.8 to 4.6 W/kg, and values of c ranged from 3.9 to 6.8 m/s. A strong inverse linear relation was found between c and PWC170 (r = -0.76), whereas the HR at rest was positively related to both c (r = 0.68) and PWC170 (r = 0.74). There was no relationship between HR at rest and the slopes S(c) and S(PWC); the latter two variables depend mainly on the sympathetic response. These results show the importance of the intrinsic mechanical properties of the cardiovascular system, particularly arterial elasticity, in human adaptations to muscular exercise.

[Exploration of left ventricular function in insulin-dependent diabetics (relation with retinopathy)]

Non invasive methods for the exploration of myocardial function permit the demonstration of preclinical diabetic cardiomyopathy. In this study, we have tried to define the relationship between the degree of diabetic retinopathy and the presence of myocardial dysfunction. We have recorded echocardiogram and phonomechanograms on thirty two insulin dependent diabetics (IDD) less than 50 years of age, without evidence of arteriosclerosis. All patients had a normal baseline electrocardiogram and a normal bicycle exercise test. These diabetics were assigned to three groups: I = no retinopathy (9 patients); II = minimum retinopathy (12 patients); III = marked retinopathy (11 patients). They were compared to ten non-diabetic control subjects of similar age (group 0). None of the parameters of systolic function was modified in the different groups of diabetics in comparison with the control group. We found, however, a very significant reduction of the maximum rate of enlargement of left ventricule and reduction of the maximum narrowing rate of the left ventricular posterior wall during the protodiastolic period in group III, v.s. group 0, I and II. Group III contained 3 patients with borderline hypertension and 5 patients with diabetic glomerulopathy. Our results indicate a diminution of myocardial compliance and relaxation in those IDD with marked retinopathy, but it raises the question of the role of borderline elevations of arterial pressure or hypertension during physical exercise, which are frequently found in diabetics with retinopathy in causing these abnormalities.

Long-term treatment of congestive heart failure with captopril

1 The efficacy of the converting-enzyme inhibitor captopril in the management of severe congestive heart failure was assessed in 14 patients over 360-885 days by clinical evaluation, M-mode echocardiography, systolic time intervals, plasma renin activity, and plasma aldosterone. 2 As compared with baseline values, a significant reduction was observed in heart rate, mean arterial pressure, left ventricular end-diastolic and end-systolic diameters, left ventricular pre-ejection period, tension time index, body weight, and plasma aldosterone. Significant increases in left ventricular ejection time and fractional circumferential shortening (p less than 0.01) were also observed. 3 The functional and haemodynamic benefit provided by captopril was therefore sustained during long-term therapy without severe untoward effects or attenuation.

Arterial compliance, systolic pressure and heart rate in elderly women at rest and on exercise

In two groups of elderly women, the relationships between arterial compliance estimated by pulse wave velocity (PWV), and systolic blood pressure (SP), heart rate (HR), oxygen consumption and the time taken to run 400 m have been studies. Both at rest and with increasing levels of exercise, faster PWVs are associated with higher SPs. These is a tendency for resting HR to be higher with faster PWVs. The changes in HR and oxygen consumption from resting values are strikingly increased with faster PWVs. The time taken over 400 m rises as arterial compliance falls. Therefore, it seems that, with aging, reduced arterial compliance is a major factor affecting cardiovascular responses to exercise.