Inhaled mass

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for particulate matter containing no asbestos and <1% crystalline silica is 3mg/m for respirable size fraction and lOmg/m for inhalable mass fraction. Exposure to any substance in the particulate mass that has a designated TLV should be controlled to that value. 

Nikander K, Bisgaard H. Impact of constant and breath-S5mchronized nebuhzation on inhaled mass of nebulized budesonide in infants and children. Pediatr Puhnonol 1999 28 187-193. 

Figure 4 Cartoon depicting technique for quantification of nebulizer output and measurement of deposition. On the left, a patient inhales nebulized particles via a Y piece. The exhalation filter captures exhaled particles. On the right, the same patient performs a similar maneuver. The inhaled mass filter captures particles that would have been inhaled. Differences between filters measure deposition. Breathing pattern can be monitored using a pneumotachograph represents the sum of minute ventilation plus nebulizer flow leaving the expiratory arm of the Y piece). (From Ref. 9.)...

Figure 5 Inhaled mass of nebulized pentamidine as a percentage of the nebulizer charge for two commercially available nebulizers (AeroTech II CIS-US, Bedford, MA, and Respirgard II Marquest, Englewood, CO) plotted against time. (From Ref. 9.)...

The factors determining deposition are divided into two main components, the inhaled mass (Eq. 2), which reflects the characteristics of the specific delivery system (8), and the deposition fraction (DF, Eq. 3) ... 

A. In Vitro Measurement of Inhaled Mass for Adult and Pediatric Aerosol Delivery... 

Figure 6 Sketch depicting technique for bench measurements of inhaled mass and particle distribution. Breathing pattern defined by settings on Harvard pump. Particles presented to patient are captured on the inhaled mass filter. In separate experiments, the cascade impactor measures inspired aerosol isokinetically. (From Ref. 10.)...

Figure 7 Influence of breathing pattern on inhaled mass during continuous nebuliza-tion. (From Ref. 13.)...

Figure 9 Reproducibility data from 10 examples of two commercially available nebulizers. Individual data points, mean, and standard deviation are illustrated for slope and plateau of the inhaled mass relationship depicted in Fig. 6. There is considerable scatter for both nebulizers, but the plateau of the AeroTech exhibits reduced variability. (From Ref. 9.)...

Figure 10 influence of solvent on nebulizer function. Data represent inhaled mass versus time for cyclosporine dissolved in either ethanol or propylene glycol. 

Figure 11 inhaled mass versus time for a solution (albuterol) and a suspension (budesonide) using the AeroTech II nebulizer (tidal volume, 200 mL frequency, 25 breaths per min duty cycle, 0.5). 

Figure 13 Pulmonary deposition of pentamidine plotted against the inhaled mass of pentamidine in patients receiving aerosolized prophylaxis. The filled circles describe those patients receiving prophylaxis who actually developed Pneumocystis carinii pneumonia. (From Ref. 20.)...

Figure 6 represents an in vitro simulation of a patient breathing an aerosol from a nebulizer and measurement of inhaled mass. An important additional goal is the assessment of the distribution of nebulized particles in a manner that represents as closely as possible the aeresol as it is actually inhaled by a patient. To measme the particle distribution investigators often use cascade impaction, described in principle in Fig. 16. The aerosol, which consists of particles suspended in a gas, enters the cascade impactor at a constant volumetric...

Figure 20 Sketch of ventilator circuit incorporating jet nebulization. The lower panel describes method for measuring inhaled mass in vitro, the upper panel, in vivo gamma camera scanning. (From Ref. 35.)...

The filter measures inhaled mass. In the insert is a sketch of the filter configuration used to measure exhaled particles (and hence deposition) and a gamma camera for regional studies. 

Nebulizers can be tested in a given ventilator circuit and, as shown in Fig. 22, the choice of nebulizer can have a significant impact on drug delivery. Inhaled mass versus time is shown for a number of common nebulizers, including the devices first tested in Fig. 5. Devices shown to be efficient for spontaneously breathing patients are often even more efficient on the ventilator provided that the ventila-... 

Figure 21 Influence of ventilator choice on aerosol output expressed as inhaled mass (%) versus time for four ventilators utilizing the Misty-Neb nebulizer. (Baxter Healthcare Corp., Valencia CA from Ref. 32.)...

Figure 22 Importance of nebulizer choice in aerosol delivery via mechanical ventilation. The breathing pattern was fixed and inhaled mass (%) is plotted against time for four different nebulizers. (From Ref. 27.)...

A low-flow cascade impactor can be inserted into the ventilator circuit between the distal tip of the endotracheal (or tracheostomy) tube and the inhaled mass filter. Impaction experiments have repeatedly shown that the aerosols leaving the tube and entering the patient are similar to those produced by small-particle nebulizers such as the AeroTech n. Often the MMADs are about 1.0 pm (27). 

Nikander K, Deyner J, Smaldone GC. Effects of equipment dead space and pediatric breathing patterns on inhaled mass of nebulized budesonide. J Aerosol Med 1999 12 67-73. 

Smaldone GC, Cruz-Rivera M, Nikander K. In vitro determination of inhaled mass and particle distribution for budesonide nebulizing suspension. J Aerosol Med 1998 11 113-125. 

Inspiration The breathing process whereby air is taken into the mouth and noise. Also called inhalation. Mass spectrometer A device that identifies relative concentrations of gases by means of mass-to-charge... 

---