Biomedical subjects
Publications and source records attributed to D Kurtz.
Sleep studies combined with the analysis of autonomic functions are, in several cases, necessary in order to make an accurate diagnosis. Polysomnograms require minimal technical equipment, the absence of which may cause the data obtained to be unreliable.
In patients with chronic obstructive pulmonary disease (COPD) exhibiting daytime hypoxaemia, a worsening of the latter occurs during sleep, particularly during REM sleep. The most efficient therapy of this sleep-related hypoxaemia is the nocturnal administration of O2 at a flow rate of 1.5-3 l/min. An alternative therapy, when daytime hypoxaemia is not too severe (PaO2 greater than 55 mmHg), is the use of almitrine (100 mg/day), a drug which improves daytime hypoxaemia in most COPD patients. The improvement of sleep hypoxaemia with almitrine is related to the increased daytime PaO2 and cannot be considered as a specific effect of almitrine on sleep-related respiratory events. It must be emphasized that almitrine is ineffective in about 25% of COPD patients ("nonresponders") and that almitrine can be used with conventional O2 therapy in patients with severe hypoxemia (daytime PaO2 less than 55 mmHg).
To clarify the paradox of a decrease in urine and sodium excretion occurring along with the elimination of peripheral edema when patients with obstructive sleep apnea (OSA) are treated with nasal continuous positive airway pressure (CPAP), we investigated the immediate effects of this treatment on the hematocrit and red blood cell count in eight patients with OSA. The hematocrit decreased in all patients, from a mean of 45.6 +/- 1.2 percent to 43.0 +/- 1.4 percent, with a parallel decrease in the red blood cell count from 4.777 +/- 0.168 millions/cu mm to 4.577 +/- 0.174 millions/cu mm (p less than 0.0005, one-tailed, in both cases). These results suggest that nasal CPAP treatment causes a hemodilution in patients with OSA, and are compatible with the hypothesis of an atrial natriuretic peptide-induced fluid shift from the intravascular to the extravascular volume in untreated patients with OSA. The reversal of these changes with CPAP treatment could explain the simultaneous decrease in sodium and urine excretion and the reduction of peripheral edema.
In its early stage adrenoleukodystrophy (ALD) is characterized by hypodensity at CT and signal abnormalities at RMI (low-intensity signal on T1-weighted sequences, high-intensity signal on T2-weighted sequences) in the white matter of the parieto-occipital region and the splenium of the corpus callosum. These CT and RMI abnormalities are suggestive of ALD in children with progressive alteration of the superior brain functions, but they are not specific of the disease. The authors present two cases of ALD and underline the almost pathognomonic value of contrast-enhanced ribbons found at the periphery of low-intensity signal plaques after gadolinium injection. These areas of blood-barrier disruption on a background of inflammation and active demyelination appear, on T2-weighted sequences, as ribbons of low-intensity signal within plaques of high-intensity signal. MRI is also superior to CT in detecting abnormalities located in the posterior fossa, notably lesions of the auditory fibres.
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Although ventilation during sleep has been studied in normal young and elderly subjects, little data are available concerning possible quantitative changes in ventilatory parameters in normal middle-aged subjects. We studied the occurrence of respiratory events and the changes in minute ventilation, tidal volume, and respiratory rate during rapid-eye-movement (REM) and non-REM (NREM) sleep in 40 normal (20 men and 20 women) middle-aged subjects, using polysomnography with pneumotachography and oximetry. Apnea indices greater than 5, with apneas predominantly of the obstructive type, were found in 17.5% of the subjects (30% of the men and 5% of the women). These "apneic" subjects differed from the "nonapneic" subjects only in that they had a higher body mass index. Minute ventilation decreased from wakefulness to sleep by 14% to 19%, owing to a decrease in tidal volume without a significant change in respiratory rate. This decrease was not greater in slow wave (stage 3-4 NREM) or in REM sleep than in stage 2 NREM sleep, nor was it greater in men than in women. It correlated with the minute ventilation during wakefulness: the higher the minute ventilation during wakefulness, the greater the decrease during sleep. The occurrence of respiratory events was not related to the degree of the decrease in minute ventilation from wakefulness to apnea-free sleep.
Despite the development of medical imaging, functional exploration of the central nervous system by means of EEG and evoked potentials still plays an important role in the diagnosis and monitoring of coma. Together with clinical examination, these techniques contribute to the assessment of coma depth and inform, sometimes earlier than clinical signs, on the course of the coma. Finally, the data supplied by paraclinical explorations have a diagnostic value in cases of acute encephalitis, dysmetabolic diseases, drug poisoning or severe cerebral anoxia.
The role of HLA antigens, and HLA-DR2 in particular, in the determination of mean sleep onset latencies (MSOLs) in multiple sclerosis (MS) was studied. It has been suggested that this antigen may play a part in the reduction of MSOLs, since nearly 100% of patients suffering from narcolepsy are DR2-positive. A multiple sleep latency test was performed in 37 patients suffering from MS without spontaneous complaints of sleep disturbances and who were typed for HLA-A, B, C, DR and DQ. The MSOL was reduced in a total of 21 patients, in only 7 of 15 DR2-positive patients and in 12 of 21 DQw1-positive patients. However, it was reduced in 13 of 16 B8- or B14-positive patients. In contrast with this, in the absence of an early sleep onset (MSOL greater than 30 min), no HLA antigens were found to be over-represented when considered individually; only those patients positive for a group of cross-reacting HLA antigens (B5, B15, B18, B21 or B35) had an MSOL greater than 30 min. These results suggest that the genes which code for the DR2 or DQw1 antigens, which are present in nearly 100% of narcoleptics, are not solely responsible for the appearance of an early sleep onset in MS.
Obstructive sleep apnea (OSA) patients have increased diuresis and natriuresis during sleep. In order to investigate the possible mechanisms of these changes in renal function, 35 consecutively diagnosed OSA patients were studied during sleep before and during nasal continuous positive airway pressure (CPAP) treatment, and were compared with 23 non-snoring controls. The excretion of urine and of electrolytes was increased before treatment and normalized with nasal CPAP treatment. The mechanism involved seems to be decreased sodium reabsorption at the level of the ascending limb of the loop of Henle. The observed increase in cyclic guanosine monophosphate excretion supports the hypothesis of increased atrial natriuretic peptide release during sleep in OSA patients.
1. It has recently been shown that obstructive sleep apnoea (OSA) patients have increased urinary water and salt excretion during sleep which tends to normalize with nasal continuous positive airway pressure (CPAP) treatment. 2. To investigate the mechanisms of these changes in renal function, nocturnal urinary excretion of catecholamines and guanosine 3':5'-cyclic monophosphate (cyclic GMP), which reflects atrial natriuretic factor (ANF) release, and next-morning plasma active renin concentrations were studied in 21 OSA patients on 2 consecutive nights, either untreated or treated with nasal CPAP. 3. In keeping with previous results, fractional urine flow and fractional Na+ and Cl- excretions were higher during untreated than during CPAP-treated nights. 4. No difference in plasma active renin concentration or in urinary excretion of noradrenaline, adrenaline, free dopamine and total dopamine could be demonstrated, but cyclic GMP excretion was significantly higher during untreated than during CPAP-treated nights. 5. The data are consistent with the hypothesis that the increased water and salt excretion in OSA patients is due to increased ANF release. 6. The proposed mechanism is an atrial distension due to increased (more negative) intrathoracic pressures during ineffective inspiratory efforts against the occluded upper airways which have been found in OSA.
Five pyridoxine-non-responsive homocystinuric patients aged 5 to 32 years were treated with oral betaine, 3 g b.i.d, in a double-blind, placebo-controlled, two-year crossover study of its effect on bone mineralization. Betaine therapy significantly reduced mean plasma homocystine (36 +/- 9 (SEM) mumol L-1 to 9 +/- 4 mumol L-1), with variable increases in plasma methionine and no adverse effects. Bone density, measured by computerized tomographic scanning of vertebral bodies, was below normal in all patients at the start of the study, and was not significantly altered by betaine therapy administered according to this protocol.
The frequency of daytime pulmonary hypertension (PH) in patients with obstructive sleep apnea syndrome (OSAS) has not been well established and its mechanisms are still under debate. We have thus performed right heart catheterization, in addition to standard spirography and arterial blood gas measurements, in a series of 46 consecutive patients in whom OSAS was firmly diagnosed by whole-night polysomnography. Only 9 of the 46 patients (20%) had PH defined by a mean resting pulmonary arterial pressure (Ppa) greater than or equal to 20 mm Hg. Among the patients without resting PH, 14 had exercising PH (defined by a Ppa greater than 30 mm Hg during 40-watt, steady-state exercise). Patients with resting PH differed from the others by a lower daytime PaO2 (60.8 +/- 7.6 versus 76.2 +/- 9.4 mm Hg; p less than 0.001), a higher daytime PaCO2 (44.6 +/- 4.2 versus 38.0 +/- 4.0 mm Hg; p less than 0.001), and lower VC and FEV1 (p less than 0.001). There was no difference between the 2 groups with regard to apnea index (62 +/- 34 versus 65 +/- 40) or the lowest sleep SaO2 (59 +/- 21 versus 66 +/- 18%) or the time spent in apnea. For the group as a whole, there was a good correlation between Ppa and daytime PaO2 (r = -0.61; p less than 0.001), PaCO2 (r = 0.55; p less than 0.001), and FEV1 (r = -0.52; p less than 0.001), but there was no significant correlation between Ppa and the apnea index, the lowest sleep SaO2, or the time spent in apnea.(ABSTRACT TRUNCATED AT 250 WORDS)
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Compliance with nasal continuous positive airway pressure (CPAP) has become a major concern, since this treatment is efficacious, but constraining. In 46 consecutive obstructive sleep apnoea (OSA) patients, we measured compliance with nasal CPAP by establishing a mean rate of use, with a built-in time counter read at three-month intervals, over a mean follow-up period of 232 +/- 27 days. The mean rate of use in the whole group was 5.14 +/- 0.31 hours per day. The acceptance rate was 90.9-93.2%, showing that patient acceptance is not a limitation in the use of nasal CPAP.
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