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Respiratory Medicine Jul 2011Body plethysmography allows to assess functional residual capacity (FRC(pleth)) and specific airway resistance (sRaw) as primary measures. In combination with deep... (Review)
Review
Body plethysmography allows to assess functional residual capacity (FRC(pleth)) and specific airway resistance (sRaw) as primary measures. In combination with deep expirations and inspirations, total lung capacity (TLC) and residual volume (RV) can be determined. Airway resistance (Raw) is calculated as the ratio of sRaw to FRC(pleth). Raw is a measure of airway obstruction and indicates the alveolar pressure needed to establish a flow rate of 1 L s(-1). In contrast, sRaw can be interpreted as the work to be performed by volume displacement to establish this flow rate. These measures represent different functional aspects and should both be considered. The measurement relies on the fact that generation of airflow needs generation of pressure. Pressure generation means that a mass of air is compressed or decompressed relative to its equilibrium volume. This difference is called "shift volume". As the body box is sealed and has rigid walls, its free volume experiences the same, mirror image-like shift volume as the lung. This shift volume can be measured via the variation of box pressure. The relationship between shift volume and alveolar pressure is assessed in a shutter maneuver, by identifying mouth and alveolar pressure under zero-flow conditions. These variables are combined to obtain FRC(pleth), sRaw and Raw. This presentation aims at providing the reader with a thorough and precise but non-technical understanding of the working principle of body plethysmography. It also aims at showing that this method yields significant additional information compared to spirometry and even bears a potential for further development.
Topics: Airway Obstruction; Airway Resistance; Functional Residual Capacity; Humans; Plethysmography, Whole Body; Spirometry; Total Lung Capacity
PubMed: 21356587
DOI: 10.1016/j.rmed.2011.02.006 -
Respiratory Physiology & Neurobiology Nov 2021Cystic fibrosis (CF) is characterized by small airway disease; but central airways may also be affected. We hypothesized that airway resistance estimated from...
Cystic fibrosis (CF) is characterized by small airway disease; but central airways may also be affected. We hypothesized that airway resistance estimated from computational fluid dynamic (CFD) methodology in infants with CF was higher than controls and that early airway inflammation in infants with CF is associated with airway resistance. Central airway models with a median of 51 bronchial outlets per model (interquartile range 46,56) were created from chest computed tomography scans of 18 infants with CF and 7 controls. Steady state airflow into the trachea was simulated to estimate central airway resistance in each model. Airway resistance was increased in the full airway models of infants with CF versus controls and in models trimmed to 33 bronchi. Airway resistance was associated with markers of inflammation in bronchoalveolar lavage fluid obtained approximately 8 months earlier but not with markers obtained at the same time. In conclusion, airway resistance estimated by CFD modeling is increased in infants with CF compared to controls and may be related to early airway inflammation.
Topics: Airway Resistance; Computer Simulation; Cystic Fibrosis; Humans; Hydrodynamics; Infant; Models, Biological; Pneumonia; Tomography, X-Ray Computed
PubMed: 34157384
DOI: 10.1016/j.resp.2021.103722 -
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 -
BioMed Research International 2015
Topics: Airway Management; Airway Resistance; Emergency Medicine; Humans; Intubation, Intratracheal; Respiration, Artificial
PubMed: 26199941
DOI: 10.1155/2015/425715 -
Respiratory Physiology & Neurobiology Oct 2023Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from... (Review)
Review
Oscillometry has been around for almost 70 years, but there are still many unknowns. The test is performed during tidal breathing and is therefore free from patient-dependent factors that could influence the results. The Forced Oscillation Technique (FOT), which requires minimal patient cooperation, is gaining ground, particularly with elderly patients and children. In pulmonology, it is a valuable tool for assessing obstructive conditions (with a distinction between central and peripheral obstruction) and restrictive disorders (intrapulmonary and extrapulmonary). Its sensitivity allows the assessment of bronchodilator and bronchoconstrictor responses. Different lung diseases show different patterns of changes in FOT, especially studied in asthma and chronic obstructive pulmonary disease. Because of these differences, many studies have analysed the usefulness of this technique in different areas of medicine. In this paper, the authors would like to present the basics of oscillometry with the areas of its most recent clinical applications.
Topics: Child; Humans; Aged; Airway Resistance; Oscillometry; Asthma; Pulmonary Disease, Chronic Obstructive; Respiratory Function Tests; Spirometry; Forced Expiratory Volume
PubMed: 37536553
DOI: 10.1016/j.resp.2023.104135 -
Respiratory Research Mar 2020The mechanism for symptomatic improvement after bronchial thermoplasty (BT) is unclear, since spirometry reveals little or no change. In this study, the effects of BT on...
BACKGROUND
The mechanism for symptomatic improvement after bronchial thermoplasty (BT) is unclear, since spirometry reveals little or no change. In this study, the effects of BT on airway resistance were examined using two independent techniques.
METHODS
Eighteen consecutive patients, with severe asthma (57.6 ± 14.2 years) were evaluated by spirometry and plethysmography at three time points: (i) baseline, (ii) left lung treated but right lung untreated and (iii) 6 weeks after both lungs were treated with BT. At each assessment, total and specific airway resistance (Raw, sRaw) were measured. High resolution CT scans were undertaken at the first two assessments, and measurements of lobar volume, airway volume and airway resistance were made. The Asthma Control Questionnaire (ACQ) was administered at each assessment.
RESULTS
The baseline ACQ score was 3.5 ± 0.9, and improved progressively to 1.8 ± 1.2 (p < 0.01). At baseline, severe airflow obstruction was observed, FEV1 44.8 ± 13.7% predicted, together with gas trapping, and elevated Raw at 342 ± 173%predicted. Following BT, significant improvements in Raw and sRaw were observed, as well as a reduction in Residual Volume, increase in Vital Capacity and no change in FEV1. The change in Raw correlated with the change in ACQ (r = 0.56, p < 0.05). CT scans demonstrated reduced airway volume at baseline, which correlated with the increased Raw determined by plethysmography (p = - 0.536, p = < 0.05). Following BT, the airway volume increased in the treated lung, and this was accompanied by a significant reduction in CT-determined local airway resistance.
CONCLUSION
Symptomatic improvement after BT is mediated by increased airway volume and reduced airway resistance.
Topics: Adult; Aged; Airway Resistance; Asthma; Bronchial Thermoplasty; Female; Humans; Male; Middle Aged; Plethysmography; Respiratory Function Tests
PubMed: 32228586
DOI: 10.1186/s12931-020-1330-5 -
Respiratory Care Jan 2012Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of... (Review)
Review
Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of many factors that contribute to obstructive lung disease. One of these factors is increased airway resistance. Airway resistance is traditionally measured by relating air flow and driving pressure using body plethysmography, thus deriving airway resistance (R(aw)), specific airway resistance (sR(aw)), and specific airway conductance (sG(aw)). Other methods to measure airway resistance include the forced oscillation technique (FOT), which allows calculation of respiratory system resistance (R(RS)) and reactance (X(RS)), and the interrupter technique, which allows calculation of interrupter resistance (R(int)). An advantage of these other methods is that they may be easier to perform than spirometry, making them particularly suited to patients who cannot perform spirometry, such as young children, patients with neuromuscular disorders, or patients on mechanical ventilation. Since spirometry also requires a deep inhalation, which can alter airway resistance, these alternative methods may provide more sensitive measures of airway resistance. Furthermore, the FOT provides unique information about lung mechanics that is not available from analysis using spirometry, body plethysmography, or the interrupter technique. However, it is unclear whether any of these measures of airway resistance contribute clinically important information to the traditional measures derived from spirometry (FEV(1), FVC, and FEV(1)/FVC). The purpose of this paper is to review the physiology and methodology of these measures of airway resistance, and then focus on their clinical utility in relation to each other and to spirometry.
Topics: Airway Resistance; Asthma; Forced Expiratory Volume; Humans; Lung; Lung Diseases, Obstructive; Plethysmography; Pulmonary Disease, Chronic Obstructive; Respiratory Function Tests; Spirometry
PubMed: 22222128
DOI: 10.4187/respcare.01411 -
Medicine Sep 2020Airway compliance is an important index in the surgery of pediatric patients. This study aimed to explore factors affecting dynamic airway compliance (Cdyn) and airway... (Observational Study)
Observational Study
Airway compliance is an important index in the surgery of pediatric patients. This study aimed to explore factors affecting dynamic airway compliance (Cdyn) and airway resistance (Raw) after general anesthesia endotracheal intubation for adenotonsillectomy of pediatric patients.A prospective study was undertaken of 107 children who underwent adenotonsillectomy in Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine between January and June 2018. The values of Cdyn and Raw were recorded at 5, 10, and 15 minute during general anesthesia endotracheal intubation. Univariate analysis and multiple linear regression analysis were performed for factors that affected Cdyn and Raw.Of the 107 patients aged 56.67 ± 18.28 months, 69 (64%) patients were male, and 26 (24%) and 12 (11%) had an upper respiratory infection in the past week and 1 to 2 weeks, respectively. During anesthesia, Cdyn showed a decreasing trend (P < .001) while Raw showed an increasing trend (P < .001). Multivariate analysis revealed that height (β=0.177-0.193) had the strongest correlation with Cdyn; rales during pulmonary auscultation (β= -2.727 to -1.363) and sputum suction (β= -1.670 to -0.949) were also associated with Cdyn (all P < .05). Height was the factor with the strongest negative correlation with Raw (β= -0.382 to -0.305). Rales during pulmonary auscultation (β=10.063-11.326) and sputum suction (β=3.863-9.003) were also associated with Raw (All P < .05).Height, rales during preoperative auscultation and sputum suction were all associated with intraoperative Cydn and Raw for pediatric patients undergoing adenotonsillectomy and should be considered before the surgery.
Topics: Adenoidectomy; Airway Resistance; Anesthesia, General; Auscultation; Body Height; Child; Child, Preschool; Female; Humans; Intubation, Intratracheal; Lung Compliance; Male; Prospective Studies; Respiratory Tract Infections; Tonsillectomy
PubMed: 32899092
DOI: 10.1097/MD.0000000000022101 -
Environmental Health : a Global Access... Jul 2018Air pollution has been found to adversely affect children's lung function. Forced expiratory volume in 1 s and forced vital capacity from spirometry have been studied...
BACKGROUND
Air pollution has been found to adversely affect children's lung function. Forced expiratory volume in 1 s and forced vital capacity from spirometry have been studied most frequently, but measurements of airway resistance may provide additional information. We assessed associations of long-term air pollution exposure with airway resistance.
METHODS
We measured airway resistance at age 8 with the interrupter resistance technique (R) in participants of the Dutch PIAMA birth cohort study. We linked R with estimated annual average air pollution concentrations [nitrogen oxides (NO, NO), PM absorbance ("soot"), and particulate matter < 2.5 μm (PM), < 10 μm (PM) and 2.5-10 μm (PM)] at the birth address and current home address (n = 983). Associations between air pollution exposure and interrupter resistance (R) were assessed using multiple linear regression adjusting for potential confounders.
RESULTS
We found that higher levels of NO at the current address were associated with higher R [adj. mean difference (95% confidence interval) per interquartile range increase in NO: 0.018 (0.001, 0.035) kPa·s·L]. Similar trends were observed for the other pollutants, except, PM. No association was found between R and exposure at the birth address.
CONCLUSIONS
Our results support the hypothesis that air pollution exposure is associated with a lower lung function in schoolchildren.
Topics: Air Pollutants; Air Pollution; Airway Resistance; Child; Cohort Studies; Humans; Netherlands; Nitrogen Oxides; Particulate Matter; Soot
PubMed: 30016982
DOI: 10.1186/s12940-018-0407-9