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NMR in Biomedicine Dec 2014The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and... (Review)
Review
The field of proton lung MRI is advancing on a variety of fronts. In the realm of functional imaging, it is now possible to use arterial spin labeling (ASL) and oxygen-enhanced imaging techniques to quantify regional perfusion and ventilation, respectively, in standard units of measurement. By combining these techniques into a single scan, it is also possible to quantify the local ventilation-perfusion ratio, which is the most important determinant of gas-exchange efficiency in the lung. To demonstrate potential for accurate and meaningful measurements of lung function, this technique was used to study gravitational gradients of ventilation, perfusion, and ventilation-perfusion ratio in healthy subjects, yielding quantitative results consistent with expected regional variations. Such techniques can also be applied in the time domain, providing new tools for studying temporal dynamics of lung function. Temporal ASL measurements showed increased spatial-temporal heterogeneity of pulmonary blood flow in healthy subjects exposed to hypoxia, suggesting sensitivity to active control mechanisms such as hypoxic pulmonary vasoconstriction, and illustrating that to fully examine the factors that govern lung function it is necessary to consider temporal as well as spatial variability. Further development to increase spatial coverage and improve robustness would enhance the clinical applicability of these new functional imaging tools. In the realm of structural imaging, pulse sequence techniques such as ultrashort echo-time radial k-space acquisition, ultrafast steady-state free precession, and imaging-based diaphragm triggering can be combined to overcome the significant challenges associated with proton MRI in the lung, enabling high-quality three-dimensional imaging of the whole lung in a clinically reasonable scan time. Images of healthy and cystic fibrosis subjects using these techniques demonstrate substantial promise for non-contrast pulmonary angiography and detailed depiction of airway disease. Although there is opportunity for further optimization, such approaches to structural lung imaging are ready for clinical testing.
Topics: Humans; Imaging, Three-Dimensional; Lung; Magnetic Resonance Imaging; Protons; Pulmonary Ventilation; Time Factors
PubMed: 24990096
DOI: 10.1002/nbm.3156 -
British Journal of Anaesthesia Sep 1963
Review
Topics: Humans; Muscle Relaxants, Central; Preanesthetic Medication; Pulmonary Ventilation; Respiratory Insufficiency
PubMed: 14066101
DOI: 10.1093/bja/35.9.521 -
Respiratory Care Nov 2014
Review
Topics: Humans; Pulmonary Ventilation; Respiration
PubMed: 25316888
DOI: 10.4187/respcare.03377 -
PloS One 2024The Incentive Spirometer (IS) increases lung volume and improves gas exchange by visually stimulating patients to take slow, deep breaths. It prevents respiratory... (Comparative Study)
Comparative Study
Comparative analysis of pulmonary ventilation distribution between low-cost and branded incentive spirometers using electrical impedance tomography in healthy adults: Study protocol.
BACKGROUND
The Incentive Spirometer (IS) increases lung volume and improves gas exchange by visually stimulating patients to take slow, deep breaths. It prevents respiratory complications and treats postoperative atelectasis in patients undergoing abdominal, thoracic, and neurosurgical procedures. Its effectiveness has been validated in studies that support improved lung capacities and volumes in individuals with respiratory complications, postoperative thoracic surgery, upper abdominal surgery, and bariatric surgery. The modified Pachón incentive spirometer (MPIS) is a cost-effective alternative to branded IS. It is crucial to validate whether the MPIS distributes ventilation as effectively as commercial devices do. Ventilation distribution will be measured using electrical impedance tomography.
OBJECTIVE
The aim is to compare the distribution of pulmonary ventilation between the MPIS and another commercial IS in healthy adults using electrical impedance tomography.
METHODS
A crossover clinical trial is proposed to evaluate the measurement of pulmonary ventilation distribution using EIT in a sample of healthy adults. All participants will use a commercial flow IS and the MPIS, with the order of assignment randomized. This research will use electrical impedance tomography to validate the operation of the MPIS.
CONCLUSIONS
This study protocol will compare two incentive spirometers' impact on pulmonary ventilation, potentially endorsing the adoption of a cost-effective device to enhance accessibility for targeted populations.
TRIAL REGISTRATION
The study was registered in ClinicalTrials.gov (NTC05532748).
Topics: Humans; Electric Impedance; Adult; Spirometry; Tomography; Pulmonary Ventilation; Male; Female; Healthy Volunteers; Cross-Over Studies; Lung; Middle Aged; Young Adult
PubMed: 38709742
DOI: 10.1371/journal.pone.0302476 -
Respiratory Physiology & Neurobiology Nov 2013Drug-induced respiratory depression (DIRD) is a common problem encountered post-operatively and can persist for days after surgery. It is not always possible to predict... (Review)
Review
Drug-induced respiratory depression (DIRD) is a common problem encountered post-operatively and can persist for days after surgery. It is not always possible to predict the timing or severity of DIRD due to the number of contributing factors. A safe and effective respiratory stimulant could improve patient care by avoiding the use of reversal agents (e.g., naloxone, which reverses analgesia as well as respiratory depression) thereby permitting better pain management by enabling the use of higher doses of analgesics, facilitate weaning from prolonged ventilation, and ameliorate sleep-disordered breathing peri-operatively. The purpose of this review is to discuss the current pharmaceutical armamentarium of drugs (doxapram and almitrine) that are licensed for use in humans as respiratory stimulants and that could be used to reverse drug-induced respiratory depression in the post-operative period. We also discuss new chemical entities (AMPAkines and GAL-021) that have been recently evaluated in Phase 1 clinical trials and where the initial regulatory registration would be as a respiratory stimulant.
Topics: Humans; Postoperative Complications; Pulmonary Ventilation; Respiratory Insufficiency; Respiratory System Agents
PubMed: 23791825
DOI: 10.1016/j.resp.2013.06.010 -
The European Respiratory Journal Jan 2007Some 300 million yrs ago, the ancestors of modern reptiles emerged from water and were committed to air breathing. They were exothermic and incapable of sustained levels... (Review)
Review
Some 300 million yrs ago, the ancestors of modern reptiles emerged from water and were committed to air breathing. They were exothermic and incapable of sustained levels of high physical activity. But from them evolved the two great classes of vertebrates with high levels of maximal oxygen consumption: the mammals and birds. A remarkable feature of these two divergent evolutionary lines is that, although the physiology of many organ systems shows many similarities, the lungs are radically different. A major difference is that the ventilation of the gas-exchanging tissue has a flow-through pattern in the bird but is reciprocating in the mammal. The result is that mammals have a reduced alveolar and arterial oxygen tension, a potential for uneven ventilation, and relatively large terminal air spaces. This in turn means that the pulmonary capillaries are poorly supported compared with the bird. The result is that the pulmonary capillaries in the bird have much thinner and more uniform walls, with more efficient gas exchange. Other advantages of the bird lung are that it utilises a more efficient cross-current pattern of gas-exchange, and the bird has separated the ventilatory and gas exchange functions. From a structure-function standpoint, the bird lung is superior.
Topics: Animals; Biological Evolution; Birds; Humans; Lung; Mammals; Pulmonary Gas Exchange; Pulmonary Ventilation
PubMed: 17197481
DOI: 10.1183/09031936.00133306 -
Minerva Anestesiologica Nov 2019Among recent lung imaging techniques and devices, electrical impedance tomography (EIT) can provide dynamic information on the distribution regional lung ventilation.... (Review)
Review
Among recent lung imaging techniques and devices, electrical impedance tomography (EIT) can provide dynamic information on the distribution regional lung ventilation. EIT images possess a high temporal and functional resolution allowing the visualization of dynamic physiological and pathological changes on a breath-by-breath basis. EIT detects changes in electric impedance (i.e., changes in gas/fluid ratio) and describes them in real time, both visually through images and waveforms, and numerically, allowing the clinician to monitor disease evolution and response to treatment. The use of EIT in clinical practice is supported by several studies demonstrating a good correlation between impedance tomography data and other validated methods of measuring lung volume. In this review, we will provide an overview on the rationale, basic functioning and most common applications of EIT in the management of mechanically ventilated patients.
Topics: Electric Impedance; Humans; Lung; Monitoring, Intraoperative; Monitoring, Physiologic; Pulmonary Circulation; Pulmonary Ventilation; Tomography
PubMed: 30945516
DOI: 10.23736/S0375-9393.19.13477-3 -
BMC Anesthesiology Jul 2019Postoperative pulmonary complications (PPCs) increase morbidity and mortality of surgical patients, duration of hospital stay and costs. Postoperative atelectasis of... (Observational Study)
Observational Study
Perioperative redistribution of regional ventilation and pulmonary function: a prospective observational study in two cohorts of patients at risk for postoperative pulmonary complications.
BACKGROUND
Postoperative pulmonary complications (PPCs) increase morbidity and mortality of surgical patients, duration of hospital stay and costs. Postoperative atelectasis of dorsal lung regions as a common PPC has been described before, but its clinical relevance is insufficiently examined. Pulmonary electrical impedance tomography (EIT) enables the bedside visualization of regional ventilation in real-time within a transversal section of the lung. Dorsal atelectasis or effusions might cause a ventral redistribution of ventilation. We hypothesized the existence of ventral redistribution in spontaneously breathing patients during their recovery from abdominal and peripheral surgery and that vital capacity is reduced if regional ventilation shifts to ventral lung regions.
METHODS
This prospective observational study included 69 adult patients undergoing elective surgery with an expected intermediate or high risk for PPCs. Patients undergoing abdominal and peripheral surgery were recruited to obtain groups of equal size. Patients received general anesthesia with and without additional regional anesthesia. On the preoperative, the first and the third postoperative day, EIT was performed at rest and during spirometry (forced breathing). The center of ventilation in dorso-ventral direction (COVy) was calculated.
RESULTS
Both groups received intraoperative low tidal volume ventilation. Postoperative ventral redistribution of ventilation (forced breathing COVy; preoperative: 16.5 (16.0-17.3); first day: 17.8 (16.9-18.2), p < 0.004; third day: 17.4 (16.2-18.2), p = 0.020) and decreased forced vital capacity in percentage of predicted values (FVC%predicted) (median: 93, 58, 64%, respectively) persisted after abdominal surgery. In addition, dorsal to ventral shift was associated with a decrease of the FVC%predicted on the third postoperative day (r = - 0.66; p < 0.001). A redistribution of pulmonary ventilation was not observed after peripheral surgery. FVC%predicted was only decreased on the first postoperative day (median FVC%predicted on the preoperative, first and third day: 85, 81 and 88%, respectively). In ten patients occurred pulmonary complications after abdominal surgery also in two patients after peripheral surgery.
CONCLUSIONS
After abdominal surgery ventral redistribution of ventilation persisted up to the third postoperative day and was associated with decreased vital capacity. The peripheral surgery group showed only minor changes in vital capacity, suggesting a role of the location of surgery for postoperative redistribution of pulmonary ventilation.
TRIAL REGISTRATION
This prospective observational single centre study was submitted to registration prior to patient enrollment at ClinicalTrials.gov (NCT02419196, Date of registration: December 1, 2014). Registration was finalized at April 17, 2015.
Topics: Aged; Aged, 80 and over; Anesthesia, Conduction; Anesthesia, General; Electric Impedance; Female; Humans; Lung; Male; Middle Aged; Monitoring, Physiologic; Perioperative Care; Pleural Effusion; Postoperative Complications; Prospective Studies; Pulmonary Atelectasis; Pulmonary Ventilation; Respiration, Artificial; Spirometry; Tomography; Vital Capacity
PubMed: 31351452
DOI: 10.1186/s12871-019-0805-8 -
Wiley Interdisciplinary Reviews.... Mar 2017The ongoing process of breathing underlies the gas exchange essential for mammalian life. Each respiratory cycle ensues from the activity of rhythmic neural circuits in... (Review)
Review
The ongoing process of breathing underlies the gas exchange essential for mammalian life. Each respiratory cycle ensues from the activity of rhythmic neural circuits in the brainstem, shaped by various modulatory signals, including mechanoreceptor feedback sensitive to lung inflation and chemoreceptor feedback dependent on gas composition in blood and tissues. This paper reviews a variety of computational models designed to reproduce experimental findings related to the neural control of breathing and generate predictions for future experimental testing. The review starts from the description of the core respiratory network in the brainstem, representing the central pattern generator (CPG) responsible for producing rhythmic respiratory activity, and progresses to encompass additional complexities needed to simulate different metabolic challenges, closed-loop feedback control including the lungs, and interactions between the respiratory and autonomic nervous systems. The integrated models considered in this review share a common framework including a distributed CPG core network responsible for generating the baseline three-phase pattern of rhythmic neural activity underlying normal breathing. WIREs Syst Biol Med 2017, 9:e1371. doi: 10.1002/wsbm.1371 For further resources related to this article, please visit the WIREs website.
Topics: Animals; Brain Stem; Central Pattern Generators; Computer Simulation; Models, Neurological; Pulmonary Gas Exchange; Pulmonary Ventilation; Respiration
PubMed: 28009109
DOI: 10.1002/wsbm.1371 -
Philosophical Transactions. Series A,... Sep 2008Current approaches to model nasal airflow are reviewed in this study, and new findings presented. These new results make use of improvements to computational and... (Review)
Review
Current approaches to model nasal airflow are reviewed in this study, and new findings presented. These new results make use of improvements to computational and experimental techniques and resources, which now allow key dynamical features to be investigated, and offer rational procedures to relate variations in anatomical form. Specifically, both replica and simplified airways of a single subject were investigated and compared with the replica airways of two other individuals with overtly differing geometries. Procedures to characterize and compare complex nasal airway geometry are first outlined. It is then shown that coupled computational and experimental studies, capable of obtaining highly resolved data, reveal internal flow structures in both intrinsically steady and unsteady situations. The results presented demonstrate that the intimate relation between nasal form and flow can be explored in greater detail than hitherto possible. By outlining means to compare complex airway geometries and demonstrating the effects of rational geometric simplification on the flow structure, this work offers a fresh approach to studies of how natural conduits guide and control flow. The concepts and tools address issues that are thus generic to flow studies in other physiological systems.
Topics: Computer Graphics; Computer Simulation; Humans; Models, Anatomic; Models, Biological; Nose; Pulmonary Ventilation; Respiration; Rheology
PubMed: 18593666
DOI: 10.1098/rsta.2008.0083