Dose variability of supplemental oxygen therapy with open patient interfaces based on in vitro measurements using a physiologically realistic upper airway model.

Background: Supplemental oxygen therapy is widely used in hospitals and in the home for chronic care. However, there are several fundamental problems with the application of this therapy such that patients are often exposed to arterial oxygen concentrations outside of the intended target range. This paper reports volume-averaged tracheal oxygen concentration measurements (FtO2) from in vitro experiments conducted using a physiologically realistic upper airway model.

In Vitro-In Silico Comparison of Pulsed Oxygen Delivery From Portable Oxygen Concentrators Versus Continuous Flow Oxygen Delivery.

Background: Portable oxygen concentrators (POCs) deliver oxygen in intermittent pulses. The challenge of establishing equivalence between continuous flow oxygen and nominal pulse flow settings on different POCs is well known. In vitro bench measurements and in silico mathematical modeling were used to compare the performance of 4 POCs versus continuous flow oxygen by predicting the F at the trachea and entering the acini.

Comparison of pulsed versus continuous oxygen delivery using realistic adult nasal airway replicas.

Background: Portable oxygen concentrators (POCs) typically include pulse flow (PF) modes to conserve oxygen. The primary aims of this study were to develop a predictive in vitro model for inhaled oxygen delivery using a set of realistic airway replicas, and to compare PF for a commercial POC with steady flow (SF) from a compressed oxygen cylinder.

Methods: Experiments were carried out using a stationary compressed oxygen cylinder, a POC, and 15 adult nasal airway replicas based on airway geometries derived from medical images.

The effect of disease and respiration on airway shape in patients with moderate persistent asthma.

Computational models of gas transport and aerosol deposition frequently utilize idealized models of bronchial tree structure, where airways are considered a network of bifurcating cylinders. However, changes in the shape of the lung during respiration affect the geometry of the airways, especially in disease conditions. In this study, the internal airway geometry was examined, concentrating on comparisons between mean lung volume (MLV) and total lung capacity (TLC).

A tree-parenchyma coupled model for lung ventilation simulation.

In this article, we develop a lung ventilation model. The parenchyma is described as an elastic homogenized media. It is irrigated by a space-filling dyadic resistive pipe network, which represents the tracheobronchial tree.

The Creation and Statistical Evaluation of a Deterministic Model of the Human Bronchial Tree from HRCT Images.

A quantitative description of the morphology of lung structure is essential prior to any form of predictive modeling of ventilation or aerosol deposition implemented within the lung. The human lung is a very complex organ, with airway structures that span two orders of magnitude and having a multitude of interfaces between air, tissue and blood. As such, current medical imaging protocols cannot provide medical practitioners and researchers with in-vivo knowledge of deeper lung structures.

An in silico analysis of oxygen uptake of a mild COPD patient during rest and exercise using a portable oxygen concentrator.

Oxygen treatment based on intermittent-flow devices with pulse delivery modes available from portable oxygen concentrators (POCs) depends on the characteristics of the delivered pulse such as volume, pulse width (the time of the pulse to be delivered), and pulse delay (the time for the pulse to be initiated from the start of inhalation) as well as a patient's breathing characteristics, disease state, and respiratory morphology. This article presents a physiological-based analysis of the performance, in terms of blood oxygenation, of a commercial POC at different settings using an in silico model of a COPD patient at rest and during exercise. The analysis encompasses experimental measurements of pulse volume, width, and time delay of the POC at three different settings and two breathing rates related to rest and exercise.

Modelling levels of nitrous oxide exposure for healthcare professionals during EMONO usage.

Background: Computational fluid dynamics (CFD) has been used to compute nitrous oxide (N2O) levels within a room during the administration of an equimolar mix of N2O/oxygen (EMONO) in the clinical setting. This study modelled realistic scenarios of EMONO usage in hospital or primary care, in order to estimate the potential N2O exposure of healthcare professionals (HCP) with routine EMONO use and to provide guidance for EMONO users.

Methods: Sixteen scenarios were defined by carrying out a survey of practitioners.

Realistic glottal motion and airflow rate during human breathing.

The glottal geometry is a key factor in the aerosol delivery efficiency for treatment of lung diseases. However, while glottal vibrations were extensively studied during human phonation, the realistic glottal motion during breathing is poorly understood. Therefore, most current studies assume an idealized steady glottis in the context of respiratory dynamics, and thus neglect the flow unsteadiness related to this motion.

Controlled, Parametric, Individualized, 2-D and 3-D Imaging Measurements of Aerosol Deposition in the Respiratory Tract of Asthmatic Human Subjects for Model Validation.

Background: Computer modeling is used to predict inhaled aerosol deposition in the lung based on definition of the aerosol characteristics and the breathing pattern and airway anatomy of the subject. Validation of the models is limited by the lack of detailed experimental data. Three-dimensional imaging provides an opportunity to address this unmet need.

Controlled, parametric, individualized, 2D and 3D imaging measurements of aerosol deposition in the respiratory tract of healthy human volunteers: in vivo data analysis.

Background: To provide a validation dataset for aerosol deposition modeling, a clinical trial was performed in which the inhalation parameters and the inhaled aerosol were controlled or characterized.

Methods: Eleven, healthy, never-smokers, male participants completed the study. Each participant performed two inhalations of (99m)Tc-labeled aerosol from a vibrating mesh nebulizer, which differed by a single controlled parameter (aerosol particle size: "small" or "large"; inhalation: "deep" or "shallow"; carrier gas: air or a helium-oxygen mix).

Airway morphology from high resolution computed tomography in healthy subjects and patients with moderate persistent asthma.

Models of the human respiratory tract developed in the past were based on measurements made on human tracheobronchial airways of healthy subjects. With the exception of a few morphometric characteristics such as the bronchial wall thickness (WT), very little has been published concerning the effects of disease on the tree structure and geometrical features. In this study, a commercial software package was used to segment the airway tree of seven healthy and six moderately persistent asthmatic patients from high resolution computed tomography images.

The use of combined single photon emission computed tomography and X-ray computed tomography to assess the fate of inhaled aerosol.

Background: Gamma camera imaging is widely used to assess pulmonary aerosol deposition. Conventional planar imaging provides limited information on its regional distribution. In this study, single photon emission computed tomography (SPECT) was used to describe deposition in three dimensions (3D) and combined with X-ray computed tomography (CT) to relate this to lung anatomy.