A three-element model of lumped parameter based on the statistic data of Weible's symmetric model and on the reference anatomic figures of the bronchial tree of the lungs has been proposed using the fluid network theory. It was assumed that the upper five or seven generations of the twenty-four generations of the respiratory airway are asymmetric, while the rest are symmetric. GEAR method was used to solve the ordinary differential equations. The pressure and flow rate distributions in different positions of the lungs during normal respiration and partial bronchial obstruction were compared, respectively. This model has great significance in finding out the air distribution in the human bronchial tree under various physiological and pathological conditions.
Airway Resistance ; Bronchi ; anatomy & histology ; pathology ; physiology ; Humans ; Models, Biological ; Respiration ; Respiratory Mechanics ; physiology

Respirator breathing resistance impacts performance of wearers during constant work load. However, it is less clear as to how breathing resistance affects the tolerant capacity of users during graded work load. The present study investigated the tolerant capacity of 8 individuals during incremental work load. The 8 subjects were required to wear two matched respirators (respirators I and II which were designed to have different breathing resistances and the same dead space) respectively on separate days and then work to end points. Minute ventilation (V(E)), breathing frequency (BF), oxygen consumption (VO(2)) and heart rate (HR) were recorded during exercise, while tolerant time, response time and breathing discomfort were measured at the end of each test trial. The test variables were compared between the two respirators by using matched-pairs t-test. The results showed that the tolerant time was significantly reduced for the respirator I with higher level of breathing resistance when compared with its counterpart with lower breathing resistance (respirator II) (P<0.05). The same changes occurred for response time. Results also showed a significant increase in V(E) and BF for respirator I wearers when the work load was above 125 W. The O(2) consumption was similar under the two breathing resistance conditions. These findings suggested that the respiratory resistance caused by self-contained breathing apparatus (SCBA) has an impact on the tolerant capacity of users.
Airway Resistance ; physiology ; Exercise ; physiology ; Exercise Tolerance ; physiology ; Humans ; Male ; Oxygen Consumption ; physiology ; Physical Exertion ; physiology ; Respiration, Artificial ; methods ; Respiratory Mechanics ; physiology ; Young Adult

Mechanical force plays an important role in physiological function and pathophysiologic conditions of respiratory system. Recently, a number of researches focused on how mechanical force affected pulmonary cells. This paper reviews the molecular basis of mechanical force in detail. The significance of mechanical force in respiratory therapy is also discussed.
Airway Resistance ; Biomechanical Phenomena ; Humans ; Lung Compliance ; Respiratory Mechanics ; physiology ; Respiratory Physiological Phenomena ; Respiratory System

BACKGROUNDObstructive sleep apnea is strongly associated with obesity, particularly abdominal obesity common in centrally obese males. Previous studies have demonstrated that intra-abdominal pressure (IAP) is increased in morbid obesity, and tracheal traction forces may influence pharyngeal airway collapsibility. This study aimed to investigate that whether IAP plays a role in the mechanism of upper airway (UA) collapsibility via IAP-related caudal tracheal traction.

METHODSAn abdominal wall lifting (AWL) system and graded CO2pneumoperitoneum pressure was applied to four supine, anesthetized Guizhou miniature pigs and its effects on tracheal displacement (TD) and airflow dynamics of UA were studied. Individual run data in 3 min obtained before and after AWL and obtained before and after graded pneumoperitoneum pressure were analyzed. Differences between baseline and AWL/graded pneumoperitoneum pressure data of each pig were examined using a Student's t-test or analysis of variance.

RESULTSApplication of AWL resulted in decreased IAP and significant caudal TD. The average displacement amplitude was 0.44 mm (P < 0.001). There were three subjects showed increased tidal volume (TV) (P < 0.01) and peak inspiratory airflow (P < 0.01); however, the change of flow limitation inspiratory UA resistance (Rua) was not significant. Experimental increased IAP by pneumoperitoneum resulted in significant cranial TD. The average displacement amplitude was 1.07 mm (P < 0.001) when IAP was 25 cmH2O compared to baseline. There were three subjects showed reduced Rua while the TV increased (P < 0.01). There was one subject had decreased TV and elevated Rua (P < 0.001).

CONCLUSIONSDecreased IAP significantly increased caudal TD, and elevated IAP significantly increased cranial TD. However, the mechanism of UA collapsibility appears primarily mediated by changes in lung volume rather than tracheal traction effect. TV plays an independent role in the mechanism of UA collapsibility.

Airway Resistance ; physiology ; Animals ; Female ; Lung Volume Measurements ; Obesity, Morbid ; physiopathology ; Sleep Apnea, Obstructive ; physiopathology ; Swine ; Tidal Volume ; physiology ; Trachea ; physiology

OBJECTIVEImpulse oscillometry (IOS) is a new method for determination of breathing mechanics, which features convenient operation, good repeatability and wider range analysis. As there is no standardized normal value in China at present, this study will provide a normal value of lung function determination by impulse oscillometry for children in Chengdu area.

METHODTotally 549 children were chosen at random from Chengdu area, with 292 boys and 257 girls who were 4 to 14 years old. The subjects were assigned into 10 age groups according to their chronological age with one year difference between every two adjacent groups. The respiratory total impedance (Zrs), viscosity resistance (Rrs) and elastic resistance (Xrs) at various oscillation frequency were measured by the Master Screen IOS which was manufactured by German Jaeger Company. The measured data were treated with the linear stepwise multiple regression, and established the prediction equation. At the same time, paired comparison was carried out with the measured data and equation obtained from this study, Lechtenboerger equation and prediction equation obtained from Guangzhou area.

RESULTThe total impedance and airway resistance were negatively correlated with the children's height and age. Zrs (male) = -0.756 + 189.586/height, r = -0.782, P < 0.001; Zrs (female) = -0.497 + 152.468/height, r = -0.726, P < 0.001. Rrs became the same in trend; while Xrs were proportional to the height, e.g. the values increased as the height increased. The difference of the airway resistance (R(5)-R(20)) was negatively correlated with the children's height: R(5)-R(20) (male) = 0.601 - 0.0034 x height, r = -0.677, P < 0.001; R(5)-R(20) (female) = 0.549 - 0.0031 x height, r = -0.658, P < 0.001. Among the relationships with many impulse oscillometry parameters, height ranked at first place; age at second. The multiple regression equation of IOS primary index was established. Both the measured data and the correlation coefficient of the study obtained equation were greater than the coefficient correlation of the Lechtenboerger equation, but had no significant difference compared with that of prediction equation in Guangzhou area.

CONCLUSIONThe normal value in impulse oscillometry in children in Chengdu area is different from the predicted parameters in other countries. The equation obtained from this study seems to be more suitable for the children in its local area. It is recommended to apply the predicted value from the corresponding population in the determination of the lung function by impulse oscillometry.

Airway Resistance ; physiology ; Child ; China ; Electric Impedance ; Female ; Humans ; Male ; Oscillometry ; methods ; Respiratory Function Tests ; methods ; Respiratory Physiological Phenomena

OBJECTIVE: Acoustic rhinometry (AR) was performed to standardize the measurement techniques, result interpretation and reference values of nasal cavity volume (NV) in preschool children. METHOD: (1) Nasal cavity models were used to test the correlations between NV, minimal cross-sectional area (MCA), and nasal resistance. (2) There were 97 four-year-old and 137 five-year-old children underwent AR test. RESULT: (1) Model tests showed that resist the nce were better correlated with the change of volume than the MCA. (2) The average bilateral NV in preschool children was (2.03 +/- 0.4) ml. No significant gender and age difference were observed (P>0.05). CONCLUSION Volume measurement appears more sensitive and reliable than the MCA in assessing nasal patency. The AR result interpretation and normative NV values in preschool children are introduced.
Airway Resistance ; Child, Preschool ; Female ; Humans ; Male ; Nasal Cavity ; anatomy & histology ; physiology ; Reference Values ; Rhinometry, Acoustic ; methods

OBJECTIVE: To obtain the normal values of acoustic rhinometry and rhinomanometry parameters of normal adult and analyze the correlation of two measurement results between rhinomanometry and acoustic rhinometry. METHOD: Eighty-two normal adults were recruited in our research. Acoustic rhinometry was used to acquire unilateral area of first constriction (UA1), unilateral area of second of constriction (UA2), unilateral minimum cross-sectional area (UMCA), unilateral nasal volume 0-5 cm, 2-5 cm (UV5, UV2-5), and rhinomanometer was used to measure the effective unilateral and total nasal resistances in inspiration, expiration at 150 Pa or Broms (radius is 200 Pa) (UR(ins150), UR(ins200), UR(exp150), UR(exp200), TR(ins150), TR(ins200), TR(exp150), TR(exp200)). RESULT: UA1 was (0.63 +/- 0.14) cm2 for male, (0.60 +/- 0.14) cm2 for female; UA2 was (0.72 +/- 0.48) cm2 for male, (0.6 +/- 0.4) cm2 for female; UMCA was (0.50 +/- 0.16) cm2 for male, (0.47 +/- 0.18) cm2 for female; UV5 was (5.68 +/- 1.73) cm3 for male, (5.16 +/- 1.85) cm3 for female; UV2-5 was (4.13 +/- 1.56) cm3 for male, (3.83 +/- 1.66) cm3 for female. No statistical significance was found between men and women (T = 0.093, 0.134, 0.392, 0.408, P > 0.05). UR(ins150) was (0.86 +/- 0.96) Pa/(cm3 x s); UR(ins200) was (0.45 +/- 0.61) Pa/(cm3 x s); UR(exp150) was (0.83 +/- 0.71) Pa/(cm3 x s); UR exp200 was (0.52 +/- 0.88) Pa/(cm3 x s); TR(ins150) was (0.38 +/- 0.34) Pa/(cm3 x s); TR(ins200) was (0.18 +/- 0.24) Pa/ (cm3 x s); TRp(exp150) was (0.38 +/- 0.27) Pa/(cm3 x s); TR(exp200) was (0.19 +/- 0. 24) Pa/(cm3 x s). There was significant correlation between UR(ins150), UR(exp150), TR(ins150), TR(exp150 and UMCA, UV5, UV2 - 5 (P < 0.05, respectively). CONCLUSION There was correlation between acoustic rhinometry and rhinomanometry. The results of this study can be used as a valuable reference to judge nasal cavity condition of normal adult.
Adolescent ; Adult ; Airway Resistance ; Female ; Humans ; Male ; Middle Aged ; Nasal Cavity ; physiology ; Reference Values ; Rhinomanometry ; Rhinometry, Acoustic ; Young Adult

BACKGROUNDFor patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) and type 2 diabetes mellitus (T2DM), the night sleep interruption and intermittent hypoxia due to apnea or hypopnea may induce glycemic excursions and reduce insulin sensitivity. This study aimed to investigate the effect of continuous positive airway pressure (CPAP) therapy in patients with OSAHS and T2DM.

METHODSContinuous glucose monitoring system (CGMS) was used in 40 patients with T2DM and newly diagnosed OSAHS. The measurements were repeated after 30 days of CPAP treatment. Subsequently, insulin sensitivity and glycohemoglobin (HbA1c) were measured and compared to the pretreatment data.

RESULTSAfter CPAP therapy, the CGMS indicators showed that the 24-h mean blood glucose (MBG) and the night time MBG were significantly reduced (P < 0.05 and P = 0.03, respectively). The mean ambulatory glucose excursions (MAGEs) and the mean of daily differences were also significantly reduced (P < 0.05 and P = 0.002, respectively) compared to pretreatment levels. During the night, MAGE also significantly decreased (P = 0.049). The differences between the highest and lowest levels of blood glucose over 24 h and during the night were significantly lower than prior to CPAP treatment (P < 0.05 and P = 0.024, respectively). The 24 h and night time durations of high blood glucose (>7.8 mmol/L and > 11.1 mmol/L) decreased (P < 0.05 and P < 0.05, respectively) after the treatment. In addition, HbA1c levels were also lower than those before treatment (P < 0.05), and the homeostasis model assessment index of insulin resistance was also significantly lower than before CPAP treatment (P = 0.034).

CONCLUSIONSCPAP therapy may have a beneficial effect on improving not only blood glucose but also upon insulin sensitivity in T2DM patients with OSAHS. This suggests that CPAP may be an effective treatment for T2DM in addition to intensive diabetes management.

Adult ; Blood Glucose ; physiology ; Continuous Positive Airway Pressure ; methods ; Diabetes Mellitus, Type 2 ; therapy ; Female ; Humans ; Insulin Resistance ; physiology ; Male ; Middle Aged ; Sleep Apnea, Obstructive ; therapy ; Treatment Outcome

OBJECTIVETo obtain the normal values of four-phase rhinomanometry specific parameters of normal adult Chinese and analyze the correlation between four-phase rhinomanometry and acoustic rhinometry measurement results.

METHODSEighty-five normal adults were recruited. The HRR2 four-phase rhinomanometry was used to acquire the effective resistances in inspiration, expiration and total breathing process (Reffin, Reffex, Refft) and vertex resistance in the process of inspiration and expiration (Vrin and Vrex). The Eccovision acoustic rhinometry was used to measure the minimum cross-sectional area (MCA) and the nasal volume of 0-5 cm nasal cavity (V5).

RESULTSReffin (x(-) +/- s) was (1.28 +/- 1.02) Pa/(cm(3).s) for male, (1.55 +/- 1.03) Pa/(cm(3).s) for female; Reflex (x(-) +/- s) was (1.43 +/- 1.07) Pa/(cm(3).s) for male, (1.75 +/- 1.14) Pa/(cm(3).s) for female; Refft (x(-) +/- s) was (1.34 +/- 0.99) Pa/(cm(3).s) for male, (1.62 +/- 1.03) Pa/(cm(3).s) for female; Vrin (x(-) +/- s) was (1.31 +/- 1.03) Pa/(cm(3).s) for male; (1.60 +/- 1.03) Pa/(cm(3).s) for female, Vrex (x(-) +/- s) was (1.46 +/- 1.04) Pa/(cm(3).s) for male, (1.82 +/- 1.17) Pa/(cm(3).s) for female. No statistically significant difference was found between men and women (r = 0.661, -0.397, 0.127, 0.649, -0.684, P > 0.05, respectively). There was no significant correlation between Reffin, Reflex, Refft, Vrin, Vrex and age, height, weight, head circumference, body surface area, body mass index (P > 0.05, respectively). However, there was significant correlation between Reffin, Reflex, Refft, Vrin, Vrex and MCA, V5 (P < 0.05, respectively).

CONCLUSIONSThe results of four-phase rhinomanometry show significant correlation to acoustic rhinometry.

Adolescent ; Adult ; Airway Resistance ; physiology ; Female ; Humans ; Male ; Middle Aged ; Nasal Cavity ; physiology ; Reference Values ; Respiration ; Rhinomanometry ; methods ; Rhinometry, Acoustic ; methods ; Young Adult

The effect of variation of nasal structure on airflow distribution was investigated. Based on the CT images of the nose of a healthy female, a three-dimensional nasal model was developed. Two new nasal models were produced by removing part of inferior turbinate and part of middle turbinate in the left side of the original model. The numerical simulation and analysis for airflow field in the three nasal models was conducted by the finite element method. The simulation results from new models were compared with those from the original model. The airflow rate changed in the two sides of new nasal models. The airflow distribution and the pressure grades varied in the side of nasal model where part of inferior turbinate or part of middle turbinate was removed. The variation of nasal cavity structure will result in airflow redistribution in nasal cavity. The effect of removing turbinate on the airflow distribution in nasal cavity was described quantitatively.
Airway Resistance ; physiology ; Computer Simulation ; Exhalation ; physiology ; Female ; Finite Element Analysis ; Humans ; Image Processing, Computer-Assisted ; Inhalation ; physiology ; Models, Biological ; Nasal Cavity ; diagnostic imaging ; physiology ; Tomography, X-Ray Computed ; Turbinates ; surgery