New aerosol delivery system for neonatal ventilator circuits.

Abstract

There is mounting evidence that a variety of drugs delivered as aerosols are likely to be of benefit in neonatal units. To avoid many of the problems associated with the use of jet nebulisers in ventilator circuits, a chamber was designed to be used in conjunction with a metered dose inhaler (MDI). The dimensions (4 cmxll cm) were chosen in an attempt to maximise drug delivery. In vitro studies were subsequently performed in order to determine the optimum operating conditions. Sodium cromoglycate delivered via this system was collected on a filter placed between the tip of an endotracheal tube and a model lung. The dose delivered was determined by means of an ultraviolet spectrophotometric assay. Using a Draeger Babylog 8000 ventilator it was found that drug delivery as maximised by actuating the device just before the inspiratory cycle when the chamber was placed adjacent to the endotracheal tube and by using a long (one second) inspiratory time. Under these conditions 1X5-2% of the original dose was deposited upon the filter at tidal volumes of 11-22 ml. When considered in terms of body weight this is many times the equivalent dose delivered to adults from an MDI. Effective drug delivery to the filter was confirmed using a radiolabeiled aerosol. Radiolabelled studies delivering aerosol to the lungs of intubated rabbits demonstrated that deposition aerosol was distributed uniformly between lobes when corrected for the weight of each lobe.In conclusion, the device appears likely to deliver significant, reproducible quantities of drug to the lower respiratory tract while being simple to use.

Optimal Delivery of Aerosols to Infants During Mechanical Ventilation

“…Furthermore, the distribution of deposited drug within the lungs of ventilated infants is currently not known. Considering the low tidal volumes associated with infant ventilation in conjunction with previous findings, (13,16) aerosol may not reach the alveolar airspace.…”

“…(11)(12)(13)(14) This extremely low delivery efficiency has been consistently demonstrated based on in vitro experiments (13,14) and animal models, (11,13,15) and in humans. (16) Newer vibrating mesh and ultrasonic nebulizers have significantly increased lung delivery efficiency of aerosols for ventilated infants to a value of approximately 10% in some cases.…”

“…From in vivo studies, Fok et al (16) reported a high fraction of the delivered 1% dose resides in the central airways. Using an MDI and rabbit model, Everard et al (13) demonstrated three-to fivefold more dose in the trachea and main bronchi than in the remainder of the lungs. Effective aerosol therapy requires that the medication be delivered to its intended site of action within the airways at a controlled dose.…”

“…The size of the ETT is limited by the patient's anatomy; however, larger tubes are known to transmit more aerosol. (13,19) Few studies have attempted to modify the wye geometry for improved aerosol delivery. Ivri and Fink 26 proposed low angles ( < 15°) in ventilation circuit components to minimize depositional losses.…”

Early prophylactic inhaled beclomethasone in infants less than 1250 g for the prevention of chronic lung disease

“…The infants in the study group were given beclomethasone diproprionate at 250 µg/puff to a target retained pulmonary dose of 0.2 mg/kg/day. The estimated retained pulmonary dose was 10% of the given dose, based on previously published literature (21)(22)(23). Infants in the placebo group received inactive propellant at the same number of puffs as the treatment group.…”