sodium-pertechnetate-tc-99m and Bronchopulmonary-Dysplasia

Bronchopulmonary dysplasia (BPD) is a significant cause of morbidity in the preterm population. Clinical severity grading based on the need for supplemental oxygen and/or need for positive airway pressure at 36 weeks postmenstrual age does not yield reproducible predictive values for later pulmonary morbidity. Single photon emission computed tomography (SPECT) was used to measure the distribution of lung ventilation (V) and perfusion (Q) in 30 BPD preterm infants at a median age of 37 weeks postmenstrual age. The V and Q were traced with 5 MBq Technegas and Technetium-labeled albumin macro aggregates, respectively, and the V/Q match-mismatch was used to quantify the extent of lung function impairment. The latter was then compared with the clinical severity grading at 36 weeks, and time spent on mechanical ventilation, continuous positive airway pressure (CPAP) and supplemental oxygen. Of those with mild and moderate BPD 3/9 and 3/11 patients, respectively, showed significant V/Q mismatches. By contrast, 4/10 patients with severe BPD showed a satisfactory V/Q matching distribution. An unsatisfactory V/Q match was not correlated with time spent on supplemental oxygen or CPAP, but was significantly negatively correlated with time spent on mechanical ventilation. SPECT provides unique additional information about regional lung function. The results suggest that the current clinical severity grading can be improved and/or complemented with SPECT.

Topics: Bronchopulmonary Dysplasia; Cohort Studies; Female; Gestational Age; Humans; Infant; Infant, Extremely Premature; Infant, Newborn; Infant, Premature; Lung; Male; Severity of Illness Index; Sodium Pertechnetate Tc 99m; Tomography, Emission-Computed, Single-Photon; Ventilation-Perfusion Ratio

The benefits of inhaled therapy in ventilated neonates are recognized, but the reliability of drug delivery in nebulizer-ventilator circuits is uncertain. We quantified the effect of changing variables. Twenty-three freshly killed rabbits (1.15-1.9 kg) were ventilated via a tracheostomy by a pressure-limited, time-cycled ventilator (Neovent). A radioaerosol of 99Tcm pertechnetate from an Ultravent nebulizer (Mallinkrodt) was fed into the proximal ventilator tubing. Two 3-minute nebulizations at "standard settings" were followed by 2 at altered pressure, frequency, gas flow, I:E ratio, or position of the nebulizer in the circuit. Each nebulization was followed by a 3-minute gamma camera image and total deposited radioactivity was measured in excised lungs and trachea. Images demonstrated good peripheral aerosol deposition. At standard settings, lung deposition averaged 2.8% of the aerosol released. This was decreased markedly by reducing tidal volume (ventilator pressures) and residence time of aerosol (I:E ratio). Reduced gas flow decreased deposition slightly, presumably by increased particle size and marginally reduced tidal volume. Deposition did not change with increased frequency; increased minute ventilation was offset by decreased residence time of the aerosol. We conclude that the Ultravent nebulizer can be used to nebulize drugs in a standard neonatal circuit, although the dose delivered is small. Tidal volume and aerosol residence time are important determinants of aerosol delivery.

Topics: Animals; Bronchopulmonary Dysplasia; Disease Models, Animal; Humans; Infant, Newborn; Lung; Lung Compliance; Lung Diseases; Nebulizers and Vaporizers; Plethysmography; Rabbits; Radionuclide Imaging; Respiration, Artificial; Sodium Pertechnetate Tc 99m; Tidal Volume