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The Laryngoscope Oct 2023Obstructive upper airway pathologies are a great clinical challenge for the airway surgeon. Protection against acute obstruction is critical, but avoidance of...
BACKGROUND
Obstructive upper airway pathologies are a great clinical challenge for the airway surgeon. Protection against acute obstruction is critical, but avoidance of unnecessary tracheostomy must also be considered. Decision-making regarding airway, although supported by some objective findings, is largely guided by subjective experience and training. This investigation aims to study the relationship between clinical respiratory distress and objective measures of airway resistance in laryngeal cancer as determined by computational fluid dynamic (CFD) and morphometric analysis.
METHODS
Retrospective CT and clinical data were obtained for series of 20 cases, defined as newly diagnosed laryngeal cancer patients who required admission or urgent airway surgery, and 20 controls. Cases and controls were matched based on T-staging. Image segmentation and morphometric analysis were first performed. Computational models based on the lattice Boltzmann method were then created and used to quantify the continuous mass flow, rigid wall, and constant static pressure inlet boundary conditions.
RESULTS
The analysis demonstrated a significant relationship between airway resistance and acute obstruction (OR 1.018, 95% CI 1.001-1.045). Morphometric analysis similarly demonstrated a significant relationship when relating measurements based on the minimum cross-section, but not on length of stenosis. Morphometric measurements also showed significance in predicting CFD results, and their relationship demonstrated that airway pressures increase exponentially below 2.5 mm. Tumor subsite did not show a significant difference, although the glottic subgroup tended to have higher resistances.
CONCLUSION
Airway resistance analysis from CFD computation correlated with presence of acute distress requiring emergent management. Morphometric analysis showed a similar correlation, demonstrating a radiologic airway assessment technique on which future risk estimation could be performed.
LEVEL OF EVIDENCE
4 (case-control study) Laryngoscope, 133:2734-2741, 2023.
Topics: Humans; Airway Resistance; Laryngeal Neoplasms; Hydrodynamics; Case-Control Studies; Retrospective Studies; Lung; Dyspnea; Airway Obstruction; Respiratory Distress Syndrome; Computer Simulation
PubMed: 36951521
DOI: 10.1002/lary.30649 -
Experimental Physiology Apr 2020What is the central question of this study? Are sex difference in the central airways present in healthy paediatric patients? What is the main finding and its...
NEW FINDINGS
What is the central question of this study? Are sex difference in the central airways present in healthy paediatric patients? What is the main finding and its importance? In patients ≤12 years we found no sex differences in central airway luminal area. After 14 years, the males had significantly larger central airway luminal areas than the females. The sex differences were minimized, but preserved when correcting for height. Luminal area is the main determinant of airway resistance and our finding could help explain sex differences in pulmonary system limitations to exercise in paediatric patients.
ABSTRACT
Cross-sectional airway area is the main determinant of resistance to airflow in the respiratory system. In paediatric patients (<18 years), previous evidence for sex differences in cross-sectional airway area was limited to patients with history of pulmonary disease or cadaveric studies with small numbers of subjects. These studies either only report tracheal data and do not include a range of ages or correct for height. Therefore, we sought to assess sex differences in airway luminal area utilizing paediatric patients of varying ages and no history of respiratory disease. Using three-dimensional reconstructions from high-resolution computed tomography scans, we retrospectively assessed the cross-sectional airway area in healthy paediatric females (n = 97) and males (n = 128) over a range of ages (1-17 years). The areas of the trachea, left main bronchus, left upper lobe, left lower lobe, right main bronchus, intermediate bronchus and right upper lobe were measured at three discrete points by a blinded investigator. No differences between the sexes were noted in the cross-sectional areas of the youngest (ages 1-12 years) patients (P > 0.05). However, in patients ≥14 years the cross-sectional areas were larger in the males compared to females in most airway sites. For instance, the cross-sectional size of the trachea was 25% (218 ± 44 vs. 163 ± 24 mm , P < 0.01) larger in males vs. females among ages 13-17 years. When accounting for height, these sex differences in airway areas were attenuated, but persisted. Our results indicate that sex differences in paediatric airway cross-sectional area manifest after age ≥14 years and are independent of height.
Topics: Airway Resistance; Bronchi; Child; Child, Preschool; Female; Humans; Inhalation; Lung; Male; Retrospective Studies; Sex Characteristics; Tomography, X-Ray Computed; Trachea
PubMed: 32003484
DOI: 10.1113/EP088370 -
Intensive Care Medicine Experimental Dec 2022The respiratory system's static compliance (C) and airway resistance (R) are measured during an end-inspiratory hold on volume-controlled ventilation (static method). A...
BACKGROUND
The respiratory system's static compliance (C) and airway resistance (R) are measured during an end-inspiratory hold on volume-controlled ventilation (static method). A numerical algorithm is presented to calculate C and R during volume-controlled ventilation on a breath-by-breath basis not requiring an end-inspiratory hold (dynamic method).
METHODS
The dynamic method combines a numerical solution of the equation of motion of the respiratory system with frequency analysis of airway signals. The method was validated experimentally with a one-liter test lung using 300 mL and 400 mL tidal volumes. It also was validated clinically using airway signals sampled at 32.25 Hz stored in a historical database as 131.1-s-long epochs. There were 15 patients in the database having epochs on volume-controlled ventilation with breaths displaying end-inspiratory holds. This allowed for the reliable calculation of paired C and R values using both static and dynamic methods. Epoch mean values for C and R were assessed by both methods and compared in aggregate form and individually for each patient in the study with Pearson's R and Bland-Altman analysis. Figures are shown as median[IQR].
RESULTS
Experimental method differences in 880 simulated breaths were 0.3[0.2,0.4] mL·cmHO for C and 0[- 0.2,0.2] cmHO·s· L for R. Clinical testing included 78,371 breaths found in 3174 epochs meeting criteria with 24[21,30] breaths per epoch. For the aggregate data, Pearson's R were 0.99 and 0.94 for C and R, respectively. Bias ± 95% limits of agreement (LOA) were 0.2 ± 1.6 mL·cmHO for C and - 0.2 ± 1.5 cmHO·s· L for R. Bias ± LOA median values for individual patients were 0.6[- 0.2, 1.4] ± 0.9[0.8, 1.2] mL·cmHO for C and - 0.1[- 0.3, 0.2] ± 0.8[0.5, 1.2] cmHO·s· L for R.
DISCUSSION
Experimental and clinical testing produced equivalent paired measurements of C and R by the dynamic and static methods under the conditions tested.
CONCLUSIONS
These findings support to the possibility of using the dynamic method in continuously monitoring respiratory system mechanics in patients on ventilatory support with volume-controlled ventilation.
PubMed: 36581716
DOI: 10.1186/s40635-022-00483-2 -
Immunology and Allergy Clinics of North... Feb 2023Physiologic changes during pregnancy have implications for both upper and lower airway function. Upper airway resistance increases, and total lung capacity decreases.... (Review)
Review
Physiologic changes during pregnancy have implications for both upper and lower airway function. Upper airway resistance increases, and total lung capacity decreases. Upper airway symptoms increase; some women develop pregnancy-induced rhinitis and there is an increased prevalence of sleep-disordered breathing compared to prepregnancy. Longitudinal studies examining changes in upper and lower airway function parameters are limited, particularly in women with asthma. Some studies have observed reduced lung function with advancing gestation; however, changes are small and unlikely to be of major clinical significance. Spirometry is therefore a useful tool for clinical assessment of women with asthma during pregnancy.
Topics: Pregnancy; Female; Humans; Asthma; Airway Resistance; Sleep Apnea Syndromes
PubMed: 36411003
DOI: 10.1016/j.iac.2022.07.005 -
Journal of Mathematical Biology Oct 2022All schoolchildren know how often they breathe, but even experts don't know exactly why. The aim of this publication is to develop a model of the resting spontaneous...
All schoolchildren know how often they breathe, but even experts don't know exactly why. The aim of this publication is to develop a model of the resting spontaneous breathing rate using physiological, physical and mathematical methods with the aid of the principle that evolution pushes physiology in a direction that is as economical as possible. The respiratory rate then follows from an equation with the parameters [Formula: see text]-production rate of the organism, resistance, static compliance and dead space of the lungs, the inspiration duration: expiration duration - ratio and the end-expiratory [Formula: see text] fraction. The derivation requires exclusively secondary school mathematics. Using the example of an adult human or a newborn child, data from the literature then result in normal values for their breathing rate at rest. The reason for the higher respiratory rate of a newborn human compared to an adult is the relatively high [Formula: see text]-production rate together with the comparatively low compliance of the lungs. A side result is the fact that the common alveolar pressure throughout the lungs and the common time constant is a consequence of the economical principle as well. Since the above parameters are not human-specific, there is no reason to assume that the above equation could not also be applicable to many animals breathing through lungs within a thorax, especially mammals. Not only physiology and biology, but also medicine, could benefit: Applicability is being discussed in pulmonary function diagnostics, including pathophysiology. However, the present publication only claims to be a theoretical concept of the spontaneous quiet breathing rate. In the absence of comparable animal data, this publication is intended to encourage further scientific tests.
Topics: Humans; Adult; Animals; Infant, Newborn; Child; Respiratory Rate; Lung; Mammals
PubMed: 36282355
DOI: 10.1007/s00285-022-01790-8 -
The Journal of the Acoustical Society... Jun 2021Steady airflow resistances in semi-occluded airways as well as acoustic impedances in vocalization are quantified from the lungs to the lips. For clinical and voice...
Steady airflow resistances in semi-occluded airways as well as acoustic impedances in vocalization are quantified from the lungs to the lips. For clinical and voice training applications, the primary focus is on two airway conditions, an oral semi-occlusion and a semi-occlusion above the vocal folds. Laryngeal airflow resistance is divided into glottal airflow resistance and epilaryngeal airway resistance. Maximum aerodynamic power is transferred to the vocal tract if the glottal airflow resistance is reduced while the epilaryngeal airway resistance is increased. A semi-occlusion at the lips helps to set up this condition. For the acoustic power transfer, the epilaryngeal airway also serves to match the impedance of the source to the impedance of the vocal tract.
Topics: Humans; Larynx; Phonation; Vocal Cords; Voice; Voice Training
PubMed: 34241487
DOI: 10.1121/10.0005124 -
American Journal of Physiology. Lung... Jun 2022Lung resistance () is determined by airway and parenchymal tissue resistance, as well as the degree of heterogeneity in airway constriction. Deep inspirations (DIs) are...
Lung resistance () is determined by airway and parenchymal tissue resistance, as well as the degree of heterogeneity in airway constriction. Deep inspirations (DIs) are known to reverse experimentally induced increase in , but the mechanism is not entirely clear. The first step toward understanding the effect of DI is to determine how each of the resistance components is affected by DI. In the present study, we measured and apparent airway resistance (, which combines the effects of airway resistance and airway heterogeneity) simultaneously before and after a DI in acetylcholine (ACh)-challenged ex vivo sheep lungs. We found that at normal breathing frequency (0.25 Hz) ACh-challenge led to a doubling of , 80.3% of that increase was caused by an increase in ; the increase in apparent tissue resistance () was insignificant. 57.7% of the increase in was abolished by a single DI. After subtracting from , the remaining was mostly independent of ACh-challenge and its reduction after a DI came mostly from the change in the mechanical properties of lung parenchyma. We conclude that at normal breathing frequency, in an unchallenged lung is mostly composed of , and the increase in due to ACh-challenge stems mostly from the increase in and that both and can be greatly reduced by a DI, likely due to a reduction in true airway resistance and heterogeneity, as well as parenchymal tissue hysteresis post DI.
Topics: Airway Resistance; Animals; Inhalation; Lung; Parenchymal Tissue; Respiratory Function Tests; Sheep
PubMed: 35537098
DOI: 10.1152/ajplung.00033.2022 -
Respiratory Care Mar 2021A 20% reduction in the FEV is routinely used as an end point for methacholine challenge testing (MCT). Measurement of FEV is effort dependent, and some patients are not...
BACKGROUND
A 20% reduction in the FEV is routinely used as an end point for methacholine challenge testing (MCT). Measurement of FEV is effort dependent, and some patients are not able to perform acceptable and repeatable forced expiration maneuvers. The goal of the present study was to investigate the diagnostic value of airway resistance measurement by forced oscillation technique (FOT), body plethysmography, and interrupter technique compared with the traditionally accepted standard FEV measurement in evaluating the responsiveness to methacholine during MCT.
METHODS
We included in the study adult subjects referred for MCT because of asthma-like symptoms and with normal baseline spirometry. We modified routine MCT protocol by adding the assessment of airway resistance to the measurement of FEV at each step of MCT.
RESULTS
We observed, in the subjects with airway hyper-responsiveness versus those with normal airway responsiveness, a significantly greater percentage change in median (interquartile range) FOT resistance at 10 Hz (25.9% [13.7%-35.4%] vs 16% [15.7%-27.2%]), plethysmographic resistance (70.2% [39.5%-116.3%] vs 37.1% [23.9%-81.9%]), and mean ± SD conductance (-41.3 ± 15.4% vs -29.6 ± 15.9%); and a significantly greater change in mean ± SD FOT reactance at 10 Hz (-0.41 ± 0.48 cm HO/L/s vs -0.09 ± 0.32 cm HO/L/s) and at 15 Hz (-0.29 ± 0.2 cm HO/L/s vs -0.1 ± 0.19 cm HO/L/s). We also recorded significant differences in airway resistance parameters (FOT resistance at 10 Hz, FOT reactance at 15 Hz, plethysmographic airway resistance, and conductance indices as well as interrupter resistance) in FEV non-responders at the onset of respiratory symptoms during MCT compared with baseline.
CONCLUSIONS
Measurements of airway resistance could possibly be used as an alternative method to spirometry in airway challenge. Significant changes in airway mechanics during MCT are detectable by airway resistance measurement in FEV non-responders with methacholine-induced asthma-like symptoms. (ClinicalTrials.gov registration NCT02343419.).
Topics: Adult; Airway Resistance; Bronchial Provocation Tests; Forced Expiratory Volume; Humans; Methacholine Chloride; Spirometry
PubMed: 33203723
DOI: 10.4187/respcare.08331 -
Clinical Physiology and Functional... Sep 2021The forced oscillation technique (FOT) provides detailed information about the mechanics of the respiratory system, while requiring minimal co-operation by the patient....
BACKGROUND
The forced oscillation technique (FOT) provides detailed information about the mechanics of the respiratory system, while requiring minimal co-operation by the patient. FOT may be abnormal in subjects with normal spirometry and appears to be more closely related to airway symptoms. It is, therefore, attractive in epidemiological studies, where a large number of different examinations are made in each subjects in a short period of time. Current technical standards recommend the mean of three consecutive measurements to be used, but there is limited information regarding within-session variability of FOT measurements.
OBJECTIVE
The purpose of this study was to examine the within-session variability in FOT measurements in a large, population-based sample.
METHODS
We performed three consecutive FOT measurements in 700 subjects using the impulse oscillometry system. The first measurement was compared to the mean of three measurements for resistance at 5 and 20 Hz (R5 and R20, respectively), R5-R20, reactance at 5 Hz (X5) and resonant frequency (f ).
RESULTS
The differences between the first and the mean of three measurements (median, interquartile range) were minimal, for example 0.002, -0.008 to 0.014 kPa L s for R5 and -0.001, -0.008 to 0.005 kPa L s for X5. Findings were numerically similar for men and women as well as for subjects with and without airflow obstruction at spirometry.
CONCLUSIONS
We conclude that, whereas in clinical situations, three FOT measurements are to be preferred, a single measurement may suffice in epidemiological studies.
Topics: Airway Resistance; Female; Forced Expiratory Volume; Humans; Male; Oscillometry; Pulmonary Disease, Chronic Obstructive; Reproducibility of Results; Spirometry
PubMed: 33914403
DOI: 10.1111/cpf.12706 -
Journal of Applied Physiology... Aug 2021Obesity alters chest wall mechanics, reduces lung volumes, and increases airway resistance. In addition, the luminal area of the larger conducting airways is smaller in...
Obesity alters chest wall mechanics, reduces lung volumes, and increases airway resistance. In addition, the luminal area of the larger conducting airways is smaller in women than in men when matched for lung size. We examined whether differences in pulmonary mechanics with obesity and sex were associated with the dysanapsis ratio (DR), an estimate of airway size when the expiratory flow is maximal, in men and women with and without obesity. In addition, we examined the ability to estimate DR using predicted versus measured static recoil pressure at 50% forced vital capacity (FVC; Pst). Participants completed pulmonary function testing and measurements of pulmonary mechanics. Flow, volume, and transpulmonary pressure were recorded while completing forced vital capacity (FVC) maneuvers in a body plethysmograph. Static compliance curves were collected using the occlusion technique. DR was calculated using measured values of forced midexpiratory flow and Pst. DR was also calculated using Pst predicted from previously reported data. There was no significant group (lean vs. obese) by sex interaction or main effect of group on DR. However, women displayed significantly larger DR compared with men. Predicted Pst was significantly greater than measured Pst. DR calculated from measured Pst was significantly greater than when using predicted Pst. In conclusion, although obesity does not appear to alter airway size, women may have larger airways compared with men when midexpiratory flow is maximal. In addition, DR estimated using predicted Pst should be used with caution. It is unclear whether obesity in combination with sex influences the dysanapsis ratio (DR). These data indicate that DR is unaltered in adults with obesity and is greater in women than in men but similar between sexes when matched for lung volume. We also report a significant difference between predicted and measured static recoil pressure. Thus, we caution against predicting static recoil pressure in the calculation of DR.
Topics: Adult; Airway Resistance; Female; Forced Expiratory Volume; Humans; Lung; Lung Volume Measurements; Male; Obesity; Vital Capacity
PubMed: 34166096
DOI: 10.1152/japplphysiol.00133.2021