Aerosol Delivery During Mechanical Ventilation to the Rat

Abstract

The authors have adjusted a jet nebulizer to a mechanical ventilator (Servo Ventilator, Siemens) to deliver an aerosol to rats. They aimed to clarify whether a modified jet nebulizer generating particles with a mass median aerodynamic diameter of 2 microm would be effective and safe in intubated ventilated rats. Fluorescent microspheres (diameter: 1.0 microm) were aerosolized to verify qualitatively and quantitatively intrapulmonary deposition. Particle deposition fraction was 3.8% (1.3%) of the delivered dose (median [interquartile range]). There was no evidence for any adverse event as assessed from heart rate, mean arterial pressure, PaO2 and PaCO2 before, during, and after nebulization. No pulmonary tissue trauma was detected histologically.

Inhaled levosimendan reduces mortality and release of proinflammatory mediators in a rat model of experimental ventilator-induced lung injury*

“…Nebulizer settings were FIO 2 0.25 and respiratory rate 40 breaths/min. Particles produced from the nebulizer have a median aerodynamic size distribution of 2.0 m (geometric standard deviation 1.6) and an intrapulmonary deposition fraction of 3.8% Ϯ 1.3% (20).…”

“…For inhalational application of levosimendan, rats were connected to a specifically designed nebulizer, as described elsewhere (20). Briefly, the system consists of a ventilator (Siemens-Servo 900-B, Siemens, Elema, Sweden) connected with an electronic valve for jet nebulization (Siemens Nebulizer 945, Siemens, Elema, Sweden) and a nebulizer chamber (Micro-Cirrus, Intersurgical, Twickenham, UK).…”

A brief exposure to isoflurane (50 s) significantly impacts on plasma cytokine levels in endotoxemic rats

“…Experiments were performed simultaneously with pairs of 2 rats/ day (one animal from the control group and one animal from the isoflurane group, at random). Surgical procedures were performed as recently described [5]. Rats were placed supine on a heating pad, tracheotomized and endotracheally intubated with a 13-G cannula (ID: 2.0 mm, OD: 2.5 mm, Abbott, Wiesbaden, Germany), modified with a standard connector for pediatric endotracheal tubes.…”

Optimized Aerosol Delivery to a Mechanically Ventilated Rodent

“…(5)(6)(7)(8) Direct liquid instillation has been shown to deposit liquid formulations in a heterogeneous pattern, localizing predominantly in the larger airways, while aerosolization results in a more diffuse, homogeneous pattern with deposition in the gas exchanging smaller airways and alveolar regions. (9,10) However, it is important to note that aerosolization is a less efficient system of delivery, with lung deposition in anesthetized, mechanically ventilated rats previously reported to be approximately 3.9%, (11) and approximately 8% in anesthetized, spontaneously breathing rats. (12) This inefficiency is a result of inertial impaction of droplets throughout the aerosol delivery system, coupled with exhalation of droplets and the residual unnebulized volume of test agent remaining in the aerosol generator.…”