A modification of the pressure-flow technique for measuring breathing of cold air and its effect on nasal cross-sectional area

Computational Fluid Dynamic Analysis of Different Velopharyngeal Closure Patterns

Objective:

Velopharyngeal (VP) closure has high impact on the quality of life, especially in patients with cleft palate. For better understanding the VP closure, it is important to understand the airflow dynamics of different closure patterns, including circular, coronal, sagittal, and circular with a Passavant’s ridge. The purpose of this study was to demonstrate the airflow characteristics of different velopharyngeal closure patterns.

Methods:

Sixteen adults with no notable upper airway abnormality who needed multislice spiral computed tomography scans as part of their clinical care. Airways were reconstructed. A cylinder and a cuboid were used to replace the VP port in three models of VP port patterns. Flow simulations were carried using computational fluid dynamics. Airflow pressures in the VP orifice, oral cavity and nasal cavity, as well as airflow velocity through the velopharyngeal orifice, were calculated.

Results:

The airflow dynamics at the velopharynx were different among different velopharyngeal patterns as the area of the velopharyngeal port increased from 0 to 25 mm2. The orifice areas of different closure conditions in four velopharyngeal closure patterns were significantly different. The maximal orifice area for adequate velopharyngeal closure was 7.57 mm2 in the coronal pattern and 6.21 mm2 in the sagittal pattern.

Conclusions:

Airflow dynamics of the velopharynx were correlated to the velopharyngeal closure patterns. Different closure patterns had different largest permitted orifice areas for getting the appropriate oral pressures for normal speech.

Analysis of Velopharyngeal Functions Using Computational Fluid Dynamics Simulations

Objectives:

Competent velopharyngeal (VP) function is the basis for normal speech. Understanding how VP structure influences the airflow during speech details is essential to the surgical improvement of pharyngoplasty. In this study, we aimed to illuminate the airflow features corresponding to various VP closure states using computed dynamic simulations.

Methods:

Three-dimensional models of the upper airways were established based on computed tomography of 8 volunteers. The velopharyngeal port was simulated by a cylinder. Computational fluid dynamics simulations were applied to illustrate the correlation between the VP port size and the airflow parameters, including the flow velocity, pressure in the velopharyngeal port, as well as the pressure in oral and nasal cavity.

Results:

The airflow dynamics at the velopharynx were maintained in the same velopharyngeal pattern as the area of the velopharyngeal port increased from 0 to 25 mm2. A total of 5 airflow patterns with distinct features were captured, corresponding to adequate closure, adequate/borderline closure (Class I and II), borderline/inadequate closure, and inadequate closure. The maximal orifice area that could be tolerated for adequate VP closure was determined to be 2.01 mm2.

Conclusion:

Different VP functions are of characteristic airflow dynamic features. Computational fluid dynamic simulation is of application potential in individualized VP surgery planning.

Guideline Values for Minimum Nasal Cross-Sectional Area in Children

OBJECTIVE

The purpose was to determine age-specific values of the minimum cross-sectional area of the nasal airway in children without cleft lip or palate and to assess whether gender differences occur with growth in order to develop guidelines for assessment in children with clefts.

PARTICIPANTS

All schoolchildren aged 8 to 17 years who met the research criteria were studied during rest breathing using the pressure-flow technique. The children came from a rural area of 3800 inhabitants. Consecutive age cohorts were used for comparisons.

RESULTS

Nasal cross-sectional area increased in females from 0.38 cm² in 8-year-olds to 0.58 cm² in 17-year-olds. There was a decrease in size at ages 10 to 11 and 14 to 15 years. In males, the area increased from 0.40 to 0.68 cm² and decreased slightly from 9 to 10 and 14 to 15 years. The annual changes were statistically significant in females between 8 and 9 and 11 to 13 years of age, and in males from 11 to 12, 13 to 14, and 15 to 17 years of age. Across gender, the only significant difference occurred at age 16.

CONCLUSIONS

Our results indicate that the increase in nasal airway size is not consistent during growth. Nasal airway size showed almost equal values for both genders in young children but was systematically larger in boys from 14 years of age on. The results refer that by 17 years of age nasal airway may not have reached adult size in males.

Perception and Respiratory Responses of the Upper Airway Mechanism to Added Resistance With Aging

Objectives

To assess breathing behaviors and perception of added respiratory loads in young compared to old individuals, and to determine whether aging affects the perception and response to changes in nasal airway resistance.

Study design

In a clinical study, 40 young (11-20 years) and 40 older (59-82 years) subjects were evaluated during rest breathing and during the application of added airway resistance loads.

Methods

The pressure-flow technique was used to measure airflow rate (mL/s) and oral-nasal pressures (cmH₂O) to calculate nasal resistance (cmH₂O/L/s). To create calibrated resistance loads for the test conditions, we used a device modified from a precision iris diaphragm.

Results

During rest breathing airflow rate was significantly lower for the younger group compared to older group. Using the loading device, 11-20-year-olds detected increased resistance at the level of 2.26 cmH₂O/L/s compared to 4.55 cmH₂O/L/s in 59-82-year-olds. In contrast to the younger group, mean airflow rate was higher during expiration than during inspiration among 59-82-year-olds except at rest breathing.

Conclusions

The data revealed that the perception and respiratory response to increased airway resistance changed with aging. Younger subjects were more sensitive to changes within the airway. In both groups, subjects responded to increased airway resistance by decreasing airflow rate. However, expiratory phase became more active than inspiratory phase only in the older group.

Level of Evidence

N/A.

Upper airway resistance during growth: A longitudinal study of children from 8 to 17 years of age

OBJECTIVE

To study upper airway breathing in 115 children annually from 8 to 17 years of age with the hypothesis that upper airway respiratory needs increase steadily during growth and show sexual dimorphism.

MATERIAL AND METHODS

To calculate nasal resistance, airflow rate (mL/s) and oronasal pressures (cmH2O) were measured during rest breathing in a seated position using the pressure-flow technique.

RESULTS

Median values of oronasal pressure ranged at different ages in girls from 0.88 to 1.13 and in boys from 0.92 to 1.44 cmH2O, being 0.95 and 0.93 cmH2O at the age of 17 years, respectively. The gender differences were statistically significant in four age groups (P < .05 by the Mann-Whitney test). Mean values of nasal resistance decreased from 8 to 17 years of age in girls from 4.0 (±3.27) to 2.4 (±2.30) and in boys from 3.3 (±2.48) to 1.5 (±0.81) cmH2O/L/s. However, there was an increase in resistance in 11-year-old girls and 12-year-old boys and at the age of 15 in both genders (P < .05 by paired t-test).

CONCLUSIONS

Respiratory efforts stabilize oronasal pressure to maintain vital functions at optimal level. Nasal resistance decreased with age but increased temporarily at the prepubertal and pubertal phases, in accordance with other growth and possibly hormonal changes. When measuring upper airway function for clinical purposes, especially in patients with sleep apnea, asthma, allergies, cleft palate, or maxillary expansion, the measurements need to be compared with age- and gender-specific values obtained from healthy children.

Supine position decreases the ability of the nose to warm and humidify air

We tested the hypothesis that decreasing nasal air volume (i.e., increasing nasal turbinate blood volume) improves nasal air conditioning. We performed a randomized, two-way crossover study on the conditioning capacity of the nose in six healthy subjects in the supine and upright position. Cold, dry air (CDA) was delivered to the nose via a nasal mask, and the temperature and humidity of air were measured before it entered and after it exited the nasal cavity. The total water gradient (TWG) across the nose was calculated and represents the nasal conditioning capacity. Nasal volume decreased significantly from baseline without changing the mucosal temperature when subjects were placed in the supine position (P < 0.01). TWG in supine position was significantly lower than that in upright position (P < 0.001). In the supine position, nasal mucosal temperature after CDA exposure was significantly lower than that in upright position (P < 0.01). Our data show that placing subjects in the supine position decreased the ability of the nose to condition CDA compared with the upright position, in contrast to our hypothesis.

Effects of age, body mass index, and gender on nasal airflow rate and pressures

OBJECTIVES

The purpose of this study was to evaluate the variation of airflow rate and oral-nasal pressure with age, body mass index (BMI), and gender (i.e., to evaluate whether the effects of age, BMI, and gender on airflow rate and pressures are convergent with their effects on nasal cross-sectional area and resistance).

STUDY DESIGN

A cross-sectional study of 332 subjects (214 female and 118 male subjects) aged 16 to 82 years.

METHODS

The aerodynamic measurements of nasal airflow rate and nasal and oral pressures were performed by posterior rhinomanometry. Age, gender, weight, and height were recorded for each subject, and the BMI was calculated. The effects of age, BMI, and gender on airflow rate and nasal and oral pressures were estimated by ANOVA.

RESULTS

Nasal airflow rate and oral and nasal pressures increased with increasing BMI. In addition, the mean values of airflow rate and pressures were significantly higher in male than in female subjects. Increasing age was related to increased oral pressure, but was not associated with airflow rate or nasal pressure.

CONCLUSIONS

This study suggests that, on the contrary to the findings in children and adolescents, BMI and gender should be taken into consideration when measuring the patency of upper airway in adults.

Variation of nasal respiratory pattern with age during growth and development

The purpose of this study was to determine changes in nasal respiratory pattern with growth and development, particularly to determine the age where upper airway growth ceases. The results on 361 healthy subjects, aged 7 to 24 years, based on aerodynamic measurements during rest breathing, showed clear differences between inspiratory and expiratory phases. Nasal airflow rate and cross-sectional area increased and oral-nasal pressure and nasal resistance decreased with age up to the age of 16, levelling by the age of 20 years. The body size and gender had effect only on nasal airflow rate. This study suggests that the measurements of the nasal respiratory pattern, determining impaired nasal airway, should be done during inspiration and using age-related assesment from a healthy population until the age of 16 years. From then on, guidelines for adults are applicable.