Deposition and Clinical Impact of Inhaled Particles in the Lung.

Particles suspended in the air we breathe are deposited in the airways as a function of the properties of the particle itself (shape, size and hydration), inspiratory air flow, airway anatomy, breathing environment, and mucociliary clearance. The scientific study of the deposition of inhaled particles in the airways has been conducted using traditional mathematical models and imaging techniques with particle markers. In recent years, the integration of statistical and computer methods, giving rise to a new discipline called digital microfluidics, has led to significant advances. In routine clinical practice, these studies are of great use for optimizing inhaler devices in line with particular characteristics of the drug to be inhaled and the pathology of the patient.

Measurement of upper airway resistances: A simple way to assess its collapsibility?

PURPOSE: The collapsibility of the upper airway is a key factor in the pathogenesis of obstructive sleep apnea (OSA). The exact measurement of this parameter, typically performed by obtaining the critical pressure (Pcrit), has not been introduced into clinical practice. The techniques that are used to measure the upper airway resistance could provide information on its the collapsibility of the airway. The aim of this study was to associate resistance in the upper airway with the presence of OSA. METHODS: Using a cross-sectional design with a control group, consecutive cases that were seen in the Chest Diseases Sleep Unit were recruited after undergoing nocturnal polysomnography. The upper airway collapsibility was determined based on the change in its resistance from the standing position to the supine position with a flow interruption (Rint) device by measuring the angle formed between the pressure/flow lines (PF angle) between the two positions. RESULTS: The PF angle was greater in the OSA group than in the controls: 7.5° (4) vs. 4° (2) (P < .001), with a positive correlation between the width of the angle and the apnea-hypopnea index (AHI) (r: 0.28, P = .03). Placing the threshold level at 10°, a sensitivity of 25% was obtained, along with a specificity of 96%, for the diagnosis of OSA. CONCLUSION: The measurement of resistance in the upper airway using flow interruption (Rint) can predict the presence of moderate and severe OSA with high specificity but low sensitivity.