Preclinical Models for Pulmonary Drug Delivery
Anthony J. Hickey, Sandro R.P. da Rocha in Pharmaceutical Inhalation Aerosol Technology, 2019
In mammals, the respiratory tree is defined by branching of the airways, the extent of which varies to some degree between species. The anatomical architecture of the respiratory tract consists of the upper and lower airways. The upper airways include the nasal cavity, pharynx, and larynx, while the lower airways are made up of the trachea and bronchial branchings of the lung (Figure 30.2). The structures within these regions can be further grouped into conducting and respiratory zones, based on structural features and their role in the process and regulation of respiration. The conducting zone is the first stage, which includes the nose, pharynx, larynx, trachea, bronchi, bronchioles, and terminal bronchioles. The respiratory zone includes the deeper, more distal structures such as the respiratory bronchioles, the alveolar ducts, and alveoli.
Inhalation Injury
Stephen M. Cohn, Matthew O. Dolich, Kenji Inaba in Acute Care Surgery and Trauma, 2016
Cioffi described 54 II patients treated with VDR-4 during 1987–1990 and compared observed mortality and pneumonia rates to those predicted by data from the recent past, in which conventional ventilation was employed (12–15 mL/kg tidal volumes). The VDR-4 was associated with a reduction in mortality from 43% (predicted) to 19% (observed), and with a reduction in pneumonia from 46% (predicted) to 26% (observed) [25]. Others showed an improvement in gas exchange at lower airway pressures [26–28]. In a recent RCT performed at the U.S. Army Burn Center, Chung et al. randomized burn patients (with or without II) requiring mechanical ventilation to VDR-4 versus low-tidal-volume ventilation. They found that the VDR-4 group achieved ventilation and oxygenation goals more frequently and required a lower rate of rescue to other forms of mechanical ventilation [29].
Vascular Innervation In The Respiratory Tract With Special Reference To Neuropeptides
Geoffrey Burnstock, Susan G. Griffith in Nonadrenergic Innervation of Blood Vessels, 2019
The vascular supply of the respiratory system is of particular importance for two reasons. Firstly, the pulmonary gas exchange requires a well-developed vascular network and secondly, the air conditioning in the upper respiratory tract — the nasal mucosa in particular — depends upon the blood flow in the submucosal vascular bed. Not surprisingly, there is extensive literature on the autonomic innervation of blood vessels in the respiratory system. Techniques for the histochemical demonstration of acetylcholinesterase (AChE) enabled studies on the distribution of presumed cholinergic nerves in the respiratory tract in which AChE-positive nerve fibers were found to form dense plexuses around blood vessels.15 The Falck-Hillarp histofluorescence method for the localization of catecholamines6 revealed a rich supply of noradrenaline(NA)-containing nerve fibers around blood vessels in the respiratory tract, particularly in the upper portion, including the nasal mucosa.4,5,7-9 A functional characterization of the adrenergic and cholinergic pathways in the autonomic control of the airways was attempted decades before the morphological and anatomical characterization of the nerve supply was possible. Already in 1929 Undritz10 demonstrated an atropine-resistant vasodilatation in the nasal mucosa, a phenomenon which has since been encountered in many vascular beds.
A computational model of upper airway respiratory function with muscular coupling
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Olusegun J. Ilegbusi, Don Nadun S. Kuruppumullage, Matthew Schiefer, Kingman P. Strohl
Figure 7 shows the predicted velocity distribution within the airway lumen for the three cases considered. Figure 7(a) presents the velocity distribution within the airway in the standing position. Air enters the airway from the nasal cavity and flows down through the airway lumen to the larynx. As expected, the highest velocity magnitude occurs near the axis of the airway lumen and the smallest velocities occur near the walls of the airway due to frictional effects are highest. There is no significant airflow into the oral cavity in both the standing posture (Figure 7(a)) and the case when dilator muscle is activated (Figure 7(c)). The result is consistent with the fact that a typical human being inhales air through the nose during breathing if no obstruction occurs. Some localized swirls are observed mostly near the irregular morphological regions of the airway. The airflow, however, is found to be significantly disturbed in the supine position due to the partial airway collapse. Specifically, the velocity within the lumen increases significantly in the epiglottic region to compensate for the narrowing walls. Figure 7(c) shows a notable recovery of the air flow velocity in the airway lumen with activation of the dilator muscle. Dilator muscle activation causes the airway to expand and allows air to flow with minimal obstruction. In our model, we allowed the oral cavity to have a small opening which in turn allows air to flow freely through the oral cavity.
Nanocrystals based pulmonary inhalation delivery system: advance and challenge
Published in Drug Delivery, 2022
Pengfei Yue, Weicheng Zhou, Guiting Huang, Fangfang Lei, Yingchong Chen, Zhilin Ma, Liru Chen, Ming Yang
The lungs are the organs that contact with the exchange of air between the organism and the outside world. They are divided into two main regions: the conducting airway region and the respiratory region. The airway is a continuous branch from the bronchi to the lungs and consists mainly of bronchi, bronchioles, and terminal bronchioles. As the bronchi continue to branch, the diameter of the tubes becomes smaller, the tube wall becomes thinner, and the structure of the tube wall changes gradually. The annular smooth muscles of the bronchi contract or relax under splanchnic nerves innervation and it is responsible for the regulation of airflow passage into the alveoli. This is the site where the lung tissue completes gas exchange consisting of respiratory bronchioles, alveolar ducts, lung sacs, and alveoli. The respiratory bronchiole is the transitional pipes between the pulmonary airway and the respiratory site. Each respiratory bronchiole branch is divided into 2–3 alveolar ducts. The alveolar sacs are the common opening of several alveoli and are connected to the alveolar ducts. The gut is the main site for the digestion and absorption of nutrients.
Novel Therapies for Sleep Apnea—The Implants Have Arrived!
Published in The Neurodiagnostic Journal, 2018
Edwin M. Valladares, Terese C. Hammond
Airway evaluation through DISE has evolved and become a good predictor of success for upper airway stimulation therapy (Vanderveken et al. 2013). DISE is an operating-room procedure where sleep is induced using a sedative, such as propofol, to mimic sleep while airway collapse is characterized using a fiber-optic laryngoscope. The sedative is used to the lowest dose that elicits loss of consciousness as measured by loss of response to normal conversational voice stimulation. Since this is a procedure conducted in an operating room, a team of nurses assists with monitoring the patient’s vitals (Charakorn and Kezirian 2016). It has been shown that patients with concentric collapse of the palate do not do well with upper airway stimulation therapy as opposed to other types of collapse, thereby suggesting that tongue protrusion from upper airway stimulation is insufficient to overcome airway obstruction in concentric collapse (Vanderveken et al. 2013). Figure 1 demonstrates examples of (a) an open airway, (b) lateral wall collapse, and (c) concentric collapse.
Related Knowledge Centers
- Nasal Mucosa
- Pharynx
- Respiration
- Respiratory Epithelium
- Esophagus
- Respiratory System
- Larynx
- Nose
- Nasal Cavity
- Epiglottis