Artificial surfactant for therapy in hydrocarbon-induced lung injury in sheep.

OBJECTIVE: To document the effect of administering artificial surfactant into the trachea, either by instillation or aerosolization, on acute lung injury experimentally induced with kerosene in sheep. DESIGN: Randomized, prospective, controlled study. SETTING: Research laboratory. SUBJECTS: Sheep (n = 24), weighing 8.5 to 25.2 kg (average 16.6). INTERVENTIONS: In anesthetized, tracheally intubated sheep with pulmonary and femoral artery catheters inserted, lung injury was induced by instilling kerosene (0.3 mL/kg) into the trachea. After 15 mins of spontaneous breathing, mechanical ventilation was instituted with a uniform F10(2) and a tidal volume of 10 mL/kg. Sheep were then assigned randomly to one of four regimens as follows: exogenous surfactant or saline (5 mL/kg each) was administered as a bolus intratracheally or by aerosolization for 6 hrs. MEASUREMENTS AND MAIN RESULTS: Arterial and mixed venous blood gases, pH, airway pressure, and static respiratory system compliance were measured and compared between aerosol saline and aerosol surfactant and between bolus saline and bolus surfactant. For all variables except static respiratory system compliance, the hourly rate of change from 15 mins, 1 hr, and 6 hrs after kerosene instillation was determined for each animal, and group rank sums of hourly rates of change were compared. For static respiratory system compliance, the slope of the pressure-volume curve with volumes of 100, 200, 300, 400, and 500 mL was computed for each animal at baseline and at 3 and 6 hrs after kerosene instillation. Group rank sums for static respiratory system compliance at 3 and 6 hrs were compared. Also, the 3- and 6-hr static respiratory system compliance values at each of the volumes were compared. With saline, six of eight sheep died; with surfactant, no sheep died (p = .001). When compared with saline at 15 mins, 1 hr, and 6 hrs after kerosene instillation, surfactant, regardless of whether administered by aerosol or bolus, significantly increased rate of change of arterial oxygen saturation, mixed venous oxygen saturation, and PO2. CONCLUSIONS: In the present animal study, artificial surfactant was an effective treatment for hydrocarbon aspiration. Aerosolized surfactant achieved results similar to instilled surfactant but at a lower total dose.

A new pediatric respiratory monitor that accurately measures imposed work of breathing: a validation study.

OBJECTIVE: A new, microprocessor-controlled respiratory monitor (model CP-100 Pediatric, Bicore Monitoring Systems, Irvine, CA) that measures imposed work of breathing and a variety of respiratory parameters for pediatric patients receiving ventilatory support has recently been developed. To validate its accuracy, measurements obtained using this monitor were compared with those obtained using conventional laboratory equipment. METHODS: An in vitro lung model was used to simulate spontaneously breathing pediatric patients ranging from infancy to 10 years of age. Tidal volume, respiratory rate, and peak inspiratory flow rates were simulated in a stepwise manner. Values for imposed work, tidal volume, peak inspiratory flow rate, and change in airway pressure for both methods were compared using regression analysis. RESULTS: The coefficients of determination (r2) describing the relationships of both methods of measuring imposed work, tidal volume, peak inspiratory flow rate, and the change in airway pressure ranged from 0.99 to 1.00, and were highly significant (p < 0.001). For all measurements, bias was minimal and precision was calculated. CONCLUSIONS: Our data reveal that this pediatric respiratory monitor accurately measures imposed work of breathing, as well as tidal volume, flow rate, and airway pressure. Imposed work of breathing measurements obtained from the monitor may be used to adjust pressure support ventilation, so that the imposed work of the breathing apparatus is reduced to zero and the patient's total work of breathing is thus decreased.