Prenatal unilateral cerebellar hypoplasia in a series of 26 cases: significance and implications for prenatal diagnosis.

OBJECTIVE: To define imaging patterns of unilateral cerebellar hypoplasia (UCH), discuss possible pathophysiological mechanisms and underline the etiology and prognosis associated with these lesions. METHODS: In this retrospective study we reviewed the charts of 26 fetuses diagnosed between 2003 and 2011 with UCH, defined by asymmetrical cerebellar hemispheres with or without decreased transverse cerebellar diameter. The review included analysis of the anatomy of the cerebellar hemispheres, including foliation, borders and parenchymal echogenicity, and of the severity of the hypoplasia. Data from clinical and biological work-up and follow-up were obtained. RESULTS: Our series could be divided into two groups according to whether imaging features changed progressively or remained constant during follow-up. In Group 1 (n = 8), the progression of imaging features, echogenic cerebellar changes and/or hyposignal in T2*-weighted MR images were highly suggestive of ischemic/hemorrhagic insult. In Group 2 (n = 18), imaging features remained constant during follow-up; UCH was associated with abnormal foliation in three proven cases of clastic lesions, a cystic lesion was noted in three cases of PHACE (posterior fossa anomalies, hemangioma, arterial anomalies, cardiac abnormalities/aortic coarctation, eye abnormalities) syndrome and, in the remaining cases, UCH remained unchanged, with no imaging pattern typical of hemorrhage. In 24 cases the infant was liveborn and follow-up was continued in 23, for a mean period of 3 years. Among these, neurological complications were identified in seven (in one of seven (at a mean of 46 months) in Group 1 and in six of 16 (at a mean of 35 months) in Group 2). The surface loss of cerebellar hemisphere was > 50% in 19/24 fetuses and the vermis was clearly normal in appearance in 19/24. Predisposing factors for fetal vascular insult were identified in eight cases: these included maternal alcohol addiction, diabetes mellitus, congenital cytomegalovirus infection and pathological placenta with thrombotic vasculopathy and infarctions. CONCLUSION: UCH is defined as a focal lesion of the cerebellum that may be secondary to hemorrhage and/or ischemic insult, suggesting a clastic origin, particularly when imaging follow-up reveals changes over time. UCH may also be a clue for the prenatal diagnosis of PHACE syndrome. The amount of surface loss of cerebellar hemisphere does not correlate with poor prognosis. UCH with normal vermis is often associated with normal outcome.

Pulmonary diffusion limitation after prolonged strenuous exercise.

To determine the effect of strenuous prolonged exercise on alveolo-capillary membrane diffusing capacity, 11 marathon runners aged 37 +/- 7 years (mean +/- SD) were studied before and during early recovery (28 +/- 14 min) from a marathon race. Lung capillary blood volume (Vc) and the alveolo-capillary diffusing capacity (Dm) were determined in a one-step maneuver by simultaneous measurements of CO and NO lung transfer (DLCO and DLNO, respectively) using the single breath, breath-holding method. After the race, both DLCO and DLNO were significantly decreased in all subjects (-10.9 +/- 4.8%, P less than 10(-4) and -29.0 +/- 11.1%, P less than 10(-4), respectively). The mean value of the derived DmCO decreased by -29.3 +/- 11.1%, whereas Vc had not entirely returned to control resting value. Although these results do not indicate the detailed mechanism involved, interstitial lung fluid was suspected to accumulate, particularly in alveoli, during the race. We concluded that the high overall work load and the extended duration of the exercise both contributed to a transient change in the structure of the alveolo-capillary membrane thereby affecting the diffusing capacity of the alveolo-capillary membrane.

Solubility of Freon 22 in human blood and lung tissue.

The solubility of Freon 22 in human blood and lung tissue was determined using the chromatographic method of Wagner et al. (J. Appl. Physiol. 36: 600-605, 1974). In normal human blood, the mean Bunsen coefficient of solubility (alpha B) was 0.804 cm3 STPD.cm-3.ATA-1 at 37 degrees C. It increased with hematocrit (Hct) according to the equation alpha B = 0.274 Hct + 0.691. Tissue homogenates were prepared from macroscopically normal lung pieces obtained at thoracotomy from eight patients undergoing resection for lung carcinoma. The Bunsen solubility coefficients were 0.537 +/- 0.068 and 0.635 +/- 0.091 in washed and unwashed lung, respectively. These values can be used in the determination of both cardiac output and pulmonary tissue volume in humans by use of the rebreathing technique.

Pulmonary gas exchange in Andean natives with excessive polycythemia--effect of hemodilution.

Pulmonary gas exchange in Andean natives (n = 8) with excessive high-altitude (3,600-4,200 m) polycythemia (hematocrit 65.1 +/- 6.6%) and hypoxemia (arterial PO2 45.6 +/- 5.6 Torr) in the absence of pulmonary or cardiovascular disease was investigated both before and after isovolemic hemodilution by use of the inert gas elimination technique. The investigations were carried out in La Paz, Bolivia (3,650 m, 500 mmHg barometric pressure). Before hemodilution, a low ventilation-perfusion (VA/Q) mode (VA/Q less than 0.1) without true shunt accounted for 11.6 +/- 5.5% of the total blood flow and was mainly responsible for the hypoxemia. The hypoventilation with a low mixed venous PO2 value may have contributed to the observed hypoxemia in the absence of an impairment in alveolar capillary diffusion. After hemodilution, cardiac output and ventilation increased from 5.5 +/- 1.2 to 6.9 +/- 1.2 l/min and from 8.5 +/- 1.4 to 9.6 +/- 1.3 l/min, respectively, although arterial and venous PO2 remained constant. VA/Q mismatching fell slightly but significantly. The hypoxemia observed in subjects suffering from high-altitude excessive polycythemia was attributed to an increased in blood flow perfusing poorly ventilated areas, but without true intra- or extrapulmonary shunt. Hypoventilation as well as a low mixed venous PO2 value may also have contributed to the observed hypoxemia.

Determination of lung capillary blood volume and membrane diffusing capacity in man by the measurements of NO and CO transfer.

NO and CO lung transfer values (TL) were measured separately in 14 healthy subjects (7 men, 7 women), using the single breath technique. Five repetitive maneuvers were performed by each subject for TLNO and TLCO determinations. The inspired mixture contained either 8 ppm NO or 0.25% CO, with 2% He, 21% O2 in N2. In order to measure an appreciable fraction of NO in the alveolar gas it was necessary to shorten the breath holding time to 3 sec. TLNO was about five times greater than TLCO. This result suggests that the specific conductance of blood (theta) for NO is very high and that the second term of the second member of the equation 1/TLNO = 1/DmNO + 1/(theta NO.Qc) is therefore negligible. DmCO and Qc values can thus be computed from TLNO and TLCO measurements. The results obtained with this method are very close to those reported in the literature; for men DmCO = 79.0 +/- 14.3 ml.min-1.Torr-1, Qc = 78.0 +/- 13.2 ml and for women DmCO = 59.0 +/- 10.1 ml.min-1.Torr-1, Qc = 59.5 +/- 11.6 ml.

Series dead space for inert gases in healthy subjects.

In ten normal subjects, series dead space was determined for six intravenously infused inert gases (SF6, ethane, cyclopropane, fluothane, ether, acetone) from their expired and alveolar concentrations. The method for sampling alveolar gas was based on the criterion of identity of mean alveolar and expired gas exchange ratios. Inert gases were analysed chromatographically. Acetone, the most soluble gas, yielded the lowest dead space, the difference to the other gases being about 4.5%. This is probably due to the non-infinite value of the series dead space ventilation-perfusion ratio (VA/Q) which was estimated at about 2,000. The diffusivity, inversely related to the molecular weight, also played a role, the heaviest gas (fluothane) having a greater dead space than the lightest (ethane). The underestimation of the dead space from acetone is expected to be greater in subjects with low tidal volume and high bronchial blood flow, i. e. in some patients with respiratory disease.

[Inert gas study of heliox gas exchange in patients with COPD]. / Etude par les gaz inertes des échanges gazeux en héliox chez les malades atteints de BPCO.

Ventilation and perfusion distributions were measured in the patients with COPD breathing room air and normoxic helium-oxygen mixture (heliox) successively, using the multiple inert gas method. The D (A-a) O2 were calculated from ideal alveolar gas (Ai) and with West's gas mean model (A). Measured PaO2 and predicted PaO2 were compared during room air and heliox breathing. There were no change in overall distributions and in D (Ai-a) while D (A-a) O2 increase significantly during heliox breathing and the predicted PaO2 were significantly higher than the measured PaO2. Heliox breathing does not seem to change parallel heterogeneity in COPD. These results suggest an impairment of series heterogeneity and O2 diffusion during heliox breathing.

[Effects of oral almitrine on the distribution of VA/Q ratio in chronic obstructive lung diseases (author's transl)]. / Almitrine orale et distribution des rapports VA/Q dans les bronchopneumopathies chroniques obstructives.

A double blind study of effects of a low dose of almitrine has been performed in patients with severe chronic obstructive lung diseases. Besides hemodynamic and ventilation data, ventilation-perfusion ratio distribution was measured by the inert gas method in order to try to explain the improvement in blood gases caused by this drug. At the dose of 1.5 mg/kg almitrine produces : 1) an increase in ventilation and PaO2, 2) no change in pulmonary vascular resistances compared to a rise on placebo, 3) a drop of 4% in the percentage of cardiac output perfusing low VA/Q lung units with a concomitant increase in lung units with VA/Q ratio between 0.1 and 10, and 4) no significant change in the distribution of ventilation. The change in the distribution of blood flow is one of the causes of the rise in PaO2, but its mechanism is at yet not clear. The present results suggest arterial vasoconstriction in units with very low VA/Q accompanied by diversion of blood flow towards lung units with higher VA/Q ratio.

[Diazepam levels in the ventricular cerebrospinal fluid and peripheral venous blood in man]. / Dosage du diazépam dans le liquide céphalo-rachidien ventriculaire et dans le sang veineux périphérique chez l'homme.

Six samples of ventricular cerebral spinal fluid from an external ventricular drain, and peripheral venous blood were taken during the course of parenteral diazepam administration in man. The diazepam level was measured by gas phase chromatography. The levels of diazepam in the CSF were low compared with the plasms concentrations and around the same level as the free circulating fraction. The drug appears in the CSF relatively late after intravenous administration. It would appear that the passage of the drug from the blood into the CSF is slow and not very marked. Therefore it is not the main cause for the pharmocodynamic effects which are the result of the drug passing the blood barrier in the more restricted sense.