Horst Windt

BACKGROUND: Noninvasive monitoring of airway inflammation is important for diagnosis and treatment intervention of lung disease. Mediators of interest are often nonvolatile molecules that are exhaled as aerosols and captured by breath condensation. Because analysis of exhaled breath condensate has been troublesome in the past, partly due to poor standardization and unknown dilution, we investigated in detail the influence of respiratory variables on exhaled particle number and size distribution during tidal breathing in healthy volunteers. METHODS: Particle number was detected by a condensation nuclei counter, and size distribution was determined by a laser spectrometer online with high time resolution while subjects underwent a defined protocol of normal and deep tidal breathing. Intra- and intersubject variability of particle emission was analyzed and physical properties of exhaled aerosols were correlated to pulmonary function variables obtained by body-plethysmography. RESULTS: The particle size distribution was in the submicron range and stable during tidal breathing. Increasing tidal volumes dominantly influenced particle number emission while flow rates had only little effect. Reproducibility within subjects was high, but there was a large variation of particle emission between subjects. The ratio of functional residual capacity to total lung capacity was found to correlate with exhaled particle numbers. This indicates that particle generation is caused by reopening of terminal airways and is dependent on functional residual capacity. CONCLUSION: We conclude that online determination of exhaled aerosols from the human lungs is a prerequisite to standardize the assessment of nonvolatile mediators by normalization to the aerosol emission rate.

BACKGROUND: Human breath contains small particles that might be useful for the noninvasive diagnosis of lung disease. In this study, the impact of airway obstruction on particle emission was investigated. METHODS: Particle number flux and particle size distribution were measured for healthy nonsmokers (n=16), healthy smokers (n=13), patients with chronic obstructive pulmonary disease (n=28, GOLD stage I-IV), and patients with asthma before and after methacholine challenge (n=10). The measurements were carried out using a condensation nucleus counter (TSI 3760) and a laser spectrometer (PMT LASAIR II-110). RESULTS: Particle number per breath showed high intrasubject reproducibility. However, there was a large intersubject variability in the number of emitted particles on the order of two magnitudes, with no influence of airway obstruction on emission level. Methacholine-induced airway obstruction, in subjects with allergic asthma, did not change the number of exhaled particles, when compared with prechallenge values. For the droplet size distribution averaged per breath, there was no difference between healthy subjects and subjects with airway obstruction. CONCLUSIONS: Airway obstruction does not change the number flux or size distribution of particles in exhaled breath. The high intersubject variability of particle emission supports the concept of online determination of aerosol properties (primarily number flux, during exhaled breath) during breath condensate sampling to properly normalize the results of biochemical analysis. As high dilution and variable dilution are the main challenges of biomarker assessment in exhaled breath condensate, this normalization procedure would significantly add to the value of the technique.

Previous investigations on the effects of cigarette smoke on cultured cells have used mainly smoke condensate dissolved in culture medium. A system has been designed which allows direct exposure of cells to fresh cigarette smoke, without an intervening layer of growth medium between the cells and the smoke. Preliminary results have been obtained which demonstrate the viability of the system. V79 cells were cultured on porous membranes (Transwell; Costar). During smoke exposure only the lower surface of each Transwell is supplied with culture medium from the bottom of the culture chambers. In this way the cells had direct contact with the atmosphere at the upper surface and could be exposed directly to the test compound. The constructed exposure system consists of a smoke generator and an exposure unit containing six Transwells, the latter contained in an incubator. Cigarette smoke was generated using a standard 2 s, 35 ml puff once per min. The puff is diluted with conditioned air from the incubator and injected into the exposure unit. Following exposure of the cells to air only for 3 h there was no effect upon V79 cell viability. However, after exposure to smoke containing between 88 and 224 mg/m3 particulate matter, an inhibition of cell proliferation and induction of micronuclei was measured. When a Cambridge filter pad was placed between the cigarette and the cell exposure system to remove particulate matter cell proliferation was also reduced and an increased frequency of micronuclei above the control value was measured.

BACKGROUND: In pulmonary medicine, aerosolization of substances for continuous inhalation is confined to different classes of nebulizers with their inherent limitations. Among the unmet medical needs is the lack of an aerosolized surfactant preparation for inhalation by preterm neonates, to avoid the risks associated with endotracheal intubation and surfactant bolus instillation. In the present report, we describe a high-concentration continuous powder aerosolization system developed for delivery of inhalable surfactant to preterm neonates. METHODS: The developed device uses a technique that allows efficient aerosolization of dry surfactant powder, generating a surfactant aerosol of high concentration. In a subsequent humidification step, the heated aerosol particles are covered with a surface layer of water. The wet surfactant aerosol is then delivered to the patient interface (e.g., nasal prongs) through a tube. RESULTS: The performance characteristics of the system are given as mass concentration, dose rate, and size distribution of the generated aerosol. Continuous aerosol flows of about 0.84 L/min can be generated from dry recombinant surfactant protein-C surfactant, with concentrations of up to 12 g/m(3) and median particle sizes of the humidified particles in the range of 3 to 3.5 μm at the patient interface. The system has been successfully used in preclinical studies. CONCLUSION: The device with its continuous high-concentration delivery is promising for noninvasive delivery of surfactant aerosol to neonates and has the potential for becoming a versatile disperser platform closing the gap between continuously operating nebulizers and discontinuously operating dry powder inhaler devices.