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European Respiratory Review : An... Mar 2022Recently, "Technical standards for respiratory oscillometry" was published, which reviewed the physiological basis of oscillometric measures and detailed the technical... (Review)
Review
Recently, "Technical standards for respiratory oscillometry" was published, which reviewed the physiological basis of oscillometric measures and detailed the technical factors related to equipment and test performance, quality assurance and reporting of results. Here we present a review of the clinical significance and applications of oscillometry. We briefly review the physiological principles of oscillometry and the basics of oscillometry interpretation, and then describe what is currently known about oscillometry in its role as a sensitive measure of airway resistance, bronchodilator responsiveness and bronchial challenge testing, and response to medical therapy, particularly in asthma and COPD. The technique may have unique advantages in situations where spirometry and other lung function tests are not suitable, such as in infants, neuromuscular disease, sleep apnoea and critical care. Other potential applications include detection of bronchiolitis obliterans, vocal cord dysfunction and the effects of environmental exposures. However, despite great promise as a useful clinical tool, we identify a number of areas in which more evidence of clinical utility is needed before oscillometry becomes routinely used for diagnosing or monitoring respiratory disease.
Topics: Airway Resistance; Asthma; Humans; Oscillometry; Respiratory Function Tests; Spirometry
PubMed: 35140105
DOI: 10.1183/16000617.0208-2021 -
Intensive Care Medicine Oct 2016We hypothesized that the ventilator-related causes of lung injury may be unified in a single variable: the mechanical power. We assessed whether the mechanical power...
PURPOSE
We hypothesized that the ventilator-related causes of lung injury may be unified in a single variable: the mechanical power. We assessed whether the mechanical power measured by the pressure-volume loops can be computed from its components: tidal volume (TV)/driving pressure (∆P aw), flow, positive end-expiratory pressure (PEEP), and respiratory rate (RR). If so, the relative contributions of each variable to the mechanical power can be estimated.
METHODS
We computed the mechanical power by multiplying each component of the equation of motion by the variation of volume and RR: [Formula: see text]where ∆V is the tidal volume, ELrs is the elastance of the respiratory system, I:E is the inspiratory-to-expiratory time ratio, and R aw is the airway resistance. In 30 patients with normal lungs and in 50 ARDS patients, mechanical power was computed via the power equation and measured from the dynamic pressure-volume curve at 5 and 15 cmH2O PEEP and 6, 8, 10, and 12 ml/kg TV. We then computed the effects of the individual component variables on the mechanical power.
RESULTS
Computed and measured mechanical powers were similar at 5 and 15 cmH2O PEEP both in normal subjects and in ARDS patients (slopes = 0.96, 1.06, 1.01, 1.12 respectively, R (2) > 0.96 and p < 0.0001 for all). The mechanical power increases exponentially with TV, ∆P aw, and flow (exponent = 2) as well as with RR (exponent = 1.4) and linearly with PEEP.
CONCLUSIONS
The mechanical power equation may help estimate the contribution of the different ventilator-related causes of lung injury and of their variations. The equation can be easily implemented in every ventilator's software.
Topics: Adult; Aged; Airway Resistance; Case-Control Studies; Female; Humans; Logistic Models; Lung; Male; Middle Aged; Positive-Pressure Respiration; Respiratory Distress Syndrome; Respiratory Mechanics; Tidal Volume; Ventilator-Induced Lung Injury; Ventilators, Mechanical
PubMed: 27620287
DOI: 10.1007/s00134-016-4505-2 -
Postgraduate Medicine Apr 2017Dyspnea refers to the sensation of breathlessness, shortness of breath, or difficulty breathing that is commonly observed in patients with respiratory and cardiac... (Review)
Review
Dyspnea refers to the sensation of breathlessness, shortness of breath, or difficulty breathing that is commonly observed in patients with respiratory and cardiac disease. In the United States alone, dyspnea is reported in up to 4 million all-cause emergency room visits annually. Dyspnea can be a symptom of several different underlying physical conditions, typically involving the lung and heart. Indeed, it is an important symptom in chronic obstructive pulmonary disease (COPD), where it is associated with limited physical activity, increased anxiety and depression, decreased health-related quality of life (HRQoL), and reduced survival. Currently there is no single physiological correlate that will accurately predict dyspnea, particularly because the mechanisms that contribute to respiratory discomfort can vary between diseases and between individuals experiencing breathlessness who have been diagnosed with the same disease. Therefore, various subjective clinical and psychophysical scales and questionnaires are typically used to measure or predict dyspnea. It is the goal of this review to discuss the pathophysiological mechanisms leading to dyspnea, particularly those associated with COPD, the physical and psychological impact on patients, assessment approaches, and modalities currently used to treat it.
Topics: Airway Resistance; Bronchodilator Agents; Dyspnea; Exercise; Health Status; Humans; Lung; Oxygen Inhalation Therapy; Pulmonary Disease, Chronic Obstructive; Quality of Life; Respiratory Mechanics; Severity of Illness Index; Sex Distribution
PubMed: 28277858
DOI: 10.1080/00325481.2017.1301190 -
Otolaryngologic Clinics of North America Oct 2018
Topics: Airway Resistance; Humans; Nasal Obstruction
PubMed: 30032999
DOI: 10.1016/j.otc.2018.06.002 -
American Journal of Respiratory and... Jun 2021If the risk of ventilator-induced lung injury in acute respiratory distress syndrome (ARDS) is causally determined by driving pressure rather than by Vt, then the... (Randomized Controlled Trial)
Randomized Controlled Trial
If the risk of ventilator-induced lung injury in acute respiratory distress syndrome (ARDS) is causally determined by driving pressure rather than by Vt, then the effect of ventilation with lower Vt on mortality would be predicted to vary according to respiratory system elastance (Ers). To determine whether the mortality benefit of ventilation with lower Vt varies according to Ers. In a secondary analysis of patients from five randomized trials of lower- versus higher-Vt ventilation strategies in ARDS and acute hypoxemic respiratory failure, the posterior probability of an interaction between the randomized Vt strategy and Ers on 60-day mortality was computed using Bayesian multivariable logistic regression. Of 1,096 patients available for analysis, 416 (38%) died by Day 60. The posterior probability that the mortality benefit from lower-Vt ventilation strategies varied with Ers was 93% (posterior median interaction odds ratio, 0.80 per cm HO/[ml/kg]; 90% credible interval, 0.63-1.02). Ers was classified as low (<2 cm HO/[ml/kg], = 321, 32%), intermediate (2-3 cm HO/[ml/kg], = 475, 46%), and high (>3 cm HO/[ml/kg], = 224, 22%). In these groups, the posterior probabilities of an absolute risk reduction in mortality ≥ 1% were 55%, 82%, and 92%, respectively. The posterior probabilities of an absolute risk reduction ≥ 5% were 29%, 58%, and 82%, respectively. The mortality benefit of ventilation with lower Vt in ARDS varies according to elastance, suggesting that lung-protective ventilation strategies should primarily target driving pressure rather than Vt.
Topics: Airway Resistance; Bayes Theorem; Elasticity; Female; Humans; Logistic Models; Male; Respiration, Artificial; Respiratory Distress Syndrome; Retrospective Studies; Survival Rate; Tidal Volume; Ventilator-Induced Lung Injury
PubMed: 33439781
DOI: 10.1164/rccm.202009-3536OC -
Clinics in Chest Medicine Sep 2014The sleep state is associated with significant changes in respiratory physiology, including ventilatory responses to hypoxia and hypercapnia, upper airway and... (Review)
Review
The sleep state is associated with significant changes in respiratory physiology, including ventilatory responses to hypoxia and hypercapnia, upper airway and intercostal muscle tone, and tidal volume and minute ventilation. These changes are further magnified in certain disease states, such as chronic obstructive pulmonary disease, restrictive respiratory disorders, neuromuscular conditions, and cardiac diseases. This article discusses the regulation of breathing during sleep in health and associated comorbid conditions.
Topics: Airway Resistance; Heart Diseases; Humans; Hypercapnia; Hypoxia; Pulmonary Disease, Chronic Obstructive; Respiration Disorders; Respiratory Mechanics; Respiratory Muscles; Respiratory Physiological Phenomena; Sleep; Sleep Apnea Syndromes
PubMed: 25156761
DOI: 10.1016/j.ccm.2014.06.001 -
Pneumonologia I Alergologia Polska 2016Airway resistance is the ratio of driving pressure to the rate of the airflow in the airways. The most frequent methods used to measure airway resistance are whole-body... (Review)
Review
Airway resistance is the ratio of driving pressure to the rate of the airflow in the airways. The most frequent methods used to measure airway resistance are whole-body plethysmography, the interrupter technique and the forced oscillation technique. All these methods allow to measure resistance during respiration at the level close to tidal volume, they do not require forced breathing manoeuvres or deep breathing during measurement. The most popular method for measuring airway resistance is whole-body plethysmography. The results of plethysmography include among others the following parameters: airway resistance (Raw), airway conductance (Gaw), specific airway resistance (sRaw) and specific airway conductance (sGaw). The interrupter technique is based on the assumption that at the moment of airway occlusion, air pressure in the mouth is equal to the alveolar pressure . In the forced oscillation technique (FOT), airway resistance is calculated basing on the changes in pressure and flow caused by air vibration. The methods for measurement of airway resistance that are described in the present paper seem to be a useful alternative to the most common lung function test - spirometry. The target group in which these methods may be widely used are particularly the patients who are unable to perform spirometry.
Topics: Airway Resistance; Asthma; Female; Forced Expiratory Volume; Humans; Male; Plethysmography, Whole Body; Respiratory Function Tests; Spirometry
PubMed: 27238174
DOI: 10.5603/PiAP.2016.0014 -
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 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 -
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