The impact of expiration on particle deposition within the nasal cavity

In vitro - in vivo correlation of intranasal drug deposition

In vitro - in vivo correlation (IVIVC) allows prediction of in vivo drug deposition from a nasally inhaled drug based on in vitro drug measurements. In vitro measurements include physical particle characterization and, more recently, deposition studies using anatomical models. Currently, there is a lack of IVIVC for deposition measurements in anatomical models, especially for deposition patterns in various nasal cavity regions. Therefore, improvement of in vitro and in vivo measurement methods and knowledge about nasal deposition mechanisms should help IVIVC in the future.

Non-Reflex Defense Mechanisms of Upper Airway Mucosa: Possible Clinical Application

The sinonasal mucosa has an essential role in defense mechanisms of the upper respiratory tract. The innate immune system presents the primary defense against noxious microorganisms followed by induction of the adaptive immune mechanisms as a consequence of the presence of pathogens. This well-known activation of adaptive immune system in response to presence of the antigen on mucosal surfaces is now broadly applicated in vaccinology research. Prevention of infectious diseases belongs to substantial challenges in maintaining the population health. Non-invasive, easily applicable mucosal vaccination purposes various research opportunities that could be usable in daily practice. However, the existence of multiple limitations such as rapid clearance of vaccine from nasal mucosa by means of mucociliary transport represents a great challenge in development of safe and efficient vaccines. Here we give an updated view on nasal functions with focus on nasal mucosal immunity and its potential application in vaccination in nearly future.

Intranasal Filtration of Inhaled Aerosol in Human Subjects as a Function of Nasal Pressure Drop

BACKGROUND

Intersubject variability in nasal deposition of inhaled aerosol is significant because of the differences in nasal anatomy and breathing rate. The notable limitation of the majority of previously developed predictive correlations is including a limited number of subjects. A few recent studies have considered a wide age range of subjects, but the resulting correlations require the knowledge of the dimensions of the nasal airways and the properties of inhaled gas. In this study empirical correlations are proposed to predict aerosol deposition in nasal airways of subjects of different age as a function of intranasal pressure drop and the particle aerodynamic diameter.

METHODS

The experimental nasal deposition and pressure drop data in anatomically correct nasal replicas of 5 adults, 13 children aged 4-14 years, and 11 infants aged 3-18 months were reanalyzed. The range of aerodynamic diameter was 0.5-5.3 μm and physiological breathing at different activity levels was considered. Correlations between nasal deposition and a deposition parameter including the aerodynamic size of inhaled aerosol and nasal pressure drop were developed with nonlinear least-square algorithms. The general coefficient of determination r² was used to evaluate the fitting accuracy for each correlation.

RESULTS

New correlations were developed to predict the intranasal deposition of particles as a function of intranasal pressure drop and particle size for pediatric and adult subjects. The intranasal deposition fraction in adults and children can be calculated using the same correlation, whereas the intranasal deposition in infants followed a different trend line because of higher intranasal pressure drop in infants.

CONCLUSION

This study was the first offering correlations to predict intranasal deposition in multiple age groups using only the aerodynamic size of inhaled aerosol and nasal pressure drop. These correlations include the effects of intersubject variability in nasal deposition within each age group and among different age groups.

Nanoparticles for nasal vaccination

The great interest in mucosal vaccine delivery arises from the fact that mucosal surfaces represent the major site of entry for many pathogens. Among other mucosal sites, nasal delivery is especially attractive for immunization, as the nasal epithelium is characterized by relatively high permeability, low enzymatic activity and by the presence of an important number of immunocompetent cells. In addition to these advantageous characteristics, the nasal route could offer simplified and more cost-effective protocols for vaccination with improved patient compliance. The use of nanocarriers provides a suitable way for the nasal delivery of antigenic molecules. Besides improved protection and facilitated transport of the antigen, nanoparticulate delivery systems could also provide more effective antigen recognition by immune cells. These represent key factors in the optimal processing and presentation of the antigen, and therefore in the subsequent development of a suitable immune response. In this sense, the design of optimized vaccine nanocarriers offers a promising way for nasal mucosal vaccination.

Voice Care Knowledge Among Clinicians and People With Healthy Voices or Dysphonia

An important clinical component in the prevention and treatment of voice disorders is voice care and hygiene. Research in voice care knowledge has mainly focussed on specific groups of professional voice users with limited reporting on the tool and evidence base used. In this study, a questionnaire to measure voice care knowledge was developed based on "best evidence." The questionnaire was validated by measuring specialist voice clinicians' agreement. Preliminary data are then presented using the voice care knowledge questionnaire with 17 subjects with nonorganic dysphonia and 17 with healthy voices. There was high (89%) agreement among the clinicians. There was a highly significant difference between the dysphonic and the healthy group scores (P = 0.00005). Furthermore, the dysphonic subjects (63% agreement) presented with less voice care knowledge than the subjects with healthy voices (72% agreement). The questionnaire provides a useful and valid tool to investigate voice care knowledge. The findings have implications for clinical intervention, voice therapy, and health prevention.

Numerical simulation of air temperature and airflow patterns in the human nose during expiration

Recovery of heat and water during expiration is an important but not yet fully understood function of the nose. The presented study investigated cooling of the expiratory air for heat recovery within the human nose applying numerical simulation. A numerical simulation in a bilateral three-dimensional model of the human nose based on computed tomography was employed. Temperature distribution and airflow patterns during expiration were displayed. Cooling of the expiratory air primarily takes place in the areas of inferior and middle turbinate. Areas of the highest decrease in temperature are characterized by turbulent airflow with vortices of low velocity. Numerical results showed good concordance with experimental in vivo temperature measurements. Heating of inspired air not only depends on inspiration but also on expiration. Cooling the warm expiratory air may be regarded as an important factor for heat recovery. Furthermore, the results demonstrate the close relation between heat exchange and airflow patterns.

Diesel exhaust enhances influenza virus infections in respiratory epithelial cells

Several factors, such as age and nutritional status, can affect the susceptibility to influenza infections. Moreover, exposure to air pollutants, such as diesel exhaust (DE), has been shown to affect respiratory virus infections in rodent models. Influenza virus primarily infects and replicates in respiratory epithelial cells, which are also a major targets for inhaled DE. Using in vitro models of human respiratory epithelial cells, we determined the effects of an aqueous-trapped solution of DE (DE(as)) on influenza infections. Differentiated human nasal and bronchial epithelial cells, as well as A549 cells, were exposed to DE(as) and infected with influenza A/Bangkok/1/79. DE(as) enhanced the susceptibility to influenza virus infection in all cell models and increased the number of influenza-infected cells within 24 h post-infection. This was not caused by suppressing antiviral mediator production, since interferon (IFN) beta levels, IFN-dependent signaling, and IFN-stimulated gene expression were also enhanced by exposure to DE(as). Many of the adverse effects induced by DE exposure are mediated by oxidative stress. Exposure to DE(as) used in these studies generated oxidative stress in respiratory epithelial cells, and addition of the antioxidant glutathione-ethylester (GSH-ET) reversed the effects of DE(as) on influenza infections. Furthermore, DE(as) increased influenza virus attachment to respiratory epithelial cells within 2 h post-infection. Taken together, the results presented here suggest that in human respiratory epithelial cells oxidative stress generated by DE(as) increases the susceptibility to influenza infection and that exposure to DE(as) increases the ability of the virus to attach to and enter respiratory epithelial cells.