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Biomedical subjects

R Ronchetti

Publications and source records attributed to R Ronchetti.

At least 37 records · Page 2Linked to original sources
PubMed1975

Clinical application of regional lung function studies in infants and small children using 13N.

A technique is described for the investigation of regional lung function in infants and children using 13N and a gamma camera. Boluses of isotopic gas are inhaled and perfused while the lung fields are scanned. The child is lightly sedated and breathes normally throughout. Regional function is assessed in terms of the distribution of gas and blood, and the balance between ventilation and perfusion is estimated by comparing an index of the ventilation per unit volume of ventilated lung with that of perfused lung. The use of the method in 8 infants and children with different clinical problems is described to show its application. The method is capable of defining the severity and localization of any abnormality and may also be useful in showing normal function in suspect areas.

Child, Preschool↗
PubMed1975

Generalized pulmonary hyperinflation and Fallot's tetralogy in a neonate investigated by pulmonary physiological and radioisotopic methods.

An infant is described who presented a complex cardiopulmonary problem which was evaluated with the help of new physiological techniques. the infant was born at term after an emergency Caesarian section for fetal distress and was found to have meconium aspiration. He remained persistently tachypnoeic and hypoxic despite high ambient oxygen. Chest radiography suggested cystic lesions at the lung bases, and lung function tests confirmed hyperinflation with delayed nitrogen washout. In addition the child had signs of Fallot's tetralogy, and this diagnosis was confirmed by cardiac catheterization. Because of persistent hypoxia and tachypnoea disproportionate to the cardiac condition, the possibility of localized lung disease was considered. Regional lung function tests were carried out in the neonatal period and again at six months of age useing radioisotopic 13N given by both inhalation and injection. These studies showed gross ventilation/perfusion imbalance in the lungs, particularly marked at the bases, but with enough generalized abnormality to preclude the possibility of surgical intervention. The principles of the measurement of lung mechanics in the newborn by whole-body plethysmography, nitrogen washout, and regional radioisotopic spirometry are outlined. The particular value of these techniques in the evaluation of complex disorders is discussed, especially where both cardiac and pulmonary abnormalities are present.

Airway Resistance↗
PubMed1975

An analysis of a rebreathing method for measuring lung volume in the premature infant.

Functional residual capacity (FRC) and thoracic gas volume (TGV) were measured in 20 infants, of whom 11 were healthy preterm infants, 5 were recovering from the respiratory distress syndrome (RDS), and 4 had other pulmonary problems. In addition, some of the theoretical aspects of rebreathing techniques, including the lung to bag N2 difference at equilibrium, were studied by constructing a simple digital computer model of the system. In both the normal preterm infants and the post-RDS group, the TGV was significantly greater than the FRC (0.02 greater than P greater than 0.01), indicating the presence of trapped gas (Fig. 2). The mean time taken to reach equilibrium during rebreathng was 44 sec in the normal infants and 52 sec in the post-RDS group (Table 2). In one infant with generalized cystic lung disease, equilibrium was not achieved even after 3 min of rebreathing (Fig. 1). The computer-generated analysis of rebreathing for a normal 3-kg infant is shown in Figure 3, with an in vivo curve for comparison. The rapid equilibration of N2 was completed within 55 sec but, as in the in vivo experiments, there was a change in slope of the line afer 1.7 min. It can be seen from Table 3 that, if a small initial bag volume (11 ml) is used, 30 sec of rebreathing is adequate for equilibration only when FRC and dead space are normal, and errors would occur if either were enlarged. The computer study showed that the gradient for N2 between bag and lung at equilibrium is of the order of 0.2-0.37% which would cause a negligible error when calculating FRC and assuming that lung N2 is equal to the measured bag N2. The combined in vivo and computer studies served to validate the rebreathing technique as a method for measuring FRC, and have enabled it to be modified for use even in small or very sick infants with poor ventilation. The most useful procedure to employ would seem to be to use an initial bag volume of 150-200 ml and to continue the rebreathing for 1.5-2 min, with samples being taken for analysis at approximately 20-sec intervals.

Computers↗