ENERGY ANALYSIS OF A NONLINEAR MODEL OF THE NORMAL HUMAN LUNG

2000 ◽  
Vol 08 (02) ◽  
pp. 115-139 ◽  
Author(s):  
A. ATHANASIADES ◽  
F. GHORBEL ◽  
J. W. CLARK ◽  
S. C. NIRANJAN ◽  
J. OLANSEN ◽  
...  
Keyword(s):  
Nonlinear Model ◽  
Respiratory Mechanics ◽  
Work Of Breathing ◽  
Laboratory Data ◽  
Upper Airways ◽  
Peripheral Airways ◽  
Viscoelastic Element ◽  
Wall Compliance ◽  
The Individual ◽  
Natural Breathing

Despite the existence of respiratory mechanics models in the literature, rarely one finds analytical expressions that predict the work of breathing (WOB) associated with natural breathing maneuvers in non-ventilated subjects. In the present study, we develop relations that explicitly identify WOB, based on a proposed nonlinear model of respiratory mechanics. The model partitions airways resistance into three components (upper, middle and small), includes a collapsible airways segment, a viscoelastic element describing lung tissue dynamics and a static chest wall compliance. The individual contribution of these respiratory components on WOB is identified and analyzed. For instance, according to model predictions, during the forced vital capacity (FVC) maneuver, most of the work is expended against dissipative forces, mainly during expiration. In addition, expiratory dissipative work during FVC is almost equally partitioned among the upper airways and the collapsible airways resistances. The former expends work at the beginning of expiration, the latter at the end of expiration. The contribution of the peripheral airways is small. Our predictions are validated against laboratory data collected from volunteer subjects and using the esophageal catheter balloon technique.

scholarly journals Tracking respiratory mechanics around natural breathing rates via variable ventilation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Samer Bou Jawde ◽  
Allan J. Walkey ◽  
Arnab Majumdar ◽  
George T. O’Connor ◽  
Bradford J. Smith ◽  
...  
Keyword(s):  
Respiratory Mechanics ◽  
Variable Ventilation ◽  
Natural Breathing

scholarly journals Airway smooth muscle photorelaxation via opsin receptor activation

2019 ◽  
Vol 316 (1) ◽  
pp. L82-L93 ◽  
Author(s):  
Peter D. Yim ◽  
George Gallos ◽  
Jose F. Perez-Zoghbi ◽  
Yi Zhang ◽  
Dingbang Xu ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Blue Light ◽  
Airway Smooth Muscle ◽  
Ex Vivo ◽  
Receptor Activation ◽  
Upper Airways ◽  
Peripheral Airways ◽  
Protein Receptor ◽  
Calcium Activated Potassium Channels ◽  
Precision Cut Lung Slices

Nonvisual opsin (OPN) receptors have recently been implicated in blue light-mediated photorelaxation of smooth muscle in various organs. Since photorelaxation has not yet been demonstrated in airway smooth muscle (ASM) or in human tissues, we questioned whether functional OPN receptors are expressed in mouse and human ASM. mRNA, encoding the OPN 3 receptor, was detected in both human and mouse ASM. To demonstrate the functionality of the OPN receptors, we performed wire myography of ex vivo ASM from mouse and human upper airways. Blue light-mediated relaxation of ACh-preconstricted airways was intensity and wavelength dependent (maximum relaxation at 430-nm blue light) and was inhibited by blockade of the large-conductance calcium-activated potassium channels with iberiotoxin. We further implicated OPN receptors as key mediators in functional photorelaxation by demonstrating increased relaxation in the presence of a G protein receptor kinase 2 inhibitor or an OPN chromophore (9- cis retinal). We corroborated these responses in peripheral airways of murine precision-cut lung slices. This is the first demonstration of photorelaxation in ASM via an OPN receptor-mediated pathway.

Time course of respiratory mechanics during histamine challenge in the dog

1992 ◽  
Vol 73 (6) ◽  
pp. 2643-2647 ◽  
Author(s):  
A. M. Lauzon ◽  
G. Dechman ◽  
J. H. Bates
Keyword(s):  
Time Course ◽  
Airway Resistance ◽  
Respiratory Mechanics ◽  
Smooth Muscles ◽  
Atropine Sulfate ◽  
Mechanical Parameters ◽  
Peripheral Airways ◽  
Tissue Resistance ◽  
Histamine Challenge ◽  
Tissue Elastance

We studied the dynamics of respiratory mechanical parameters in anesthetized tracheostomized paralyzed dogs challenged with a bolus of histamine injected either venously (venous group) or arterially (arterial group). The venous group was further divided into two groups: the first was bilaterally vagotomized and received hexamethonium bromide (denervated group), and the second also received atropine sulfate (atropine group). In the venous group, tissue resistance (Rti) and tissue elastance (Eti) increased biphasically, whereas airway resistance was monophasic and synchronized with the second rise of the tissue parameters. In the arterial group, Rti, Eti, and airway resistance increased synchronously. The denervated and atropine groups showed dynamics similar to those of the venous group. We postulate that the first phase observed in Rti and Eti in the venous group is due to constriction of the smooth muscles of the peripheral airways and blood vessels distorting the parenchyma. The second and larger phase is then due to histamine reaching the bronchial circulation and constricting the central airways, again distorting the parenchyma. The results from the arterial group support this hypothesis, whereas those from the denervated group ascertain that none of the phases observed in the venous group was due to nervous reflexes.

scholarly journals Using Machine Learning to Aid the Interpretation of Urine Steroid Profiles

2018 ◽  
Vol 64 (11) ◽  
pp. 1586-1595 ◽  
Author(s):  
Edmund H Wilkes ◽  
Gill Rumsby ◽  
Gary M Woodward
Keyword(s):  
Machine Learning ◽  
Clinical Laboratory ◽  
Laboratory Data ◽  
Large Data ◽  
Data Sets ◽  
Clinical Practices ◽  
Steroid Profiles ◽  
The Individual ◽  
Multiclass Classifier ◽  
Urine Steroid

Abstract BACKGROUND Urine steroid profiles are used in clinical practice for the diagnosis and monitoring of disorders of steroidogenesis and adrenal pathologies. Machine learning (ML) algorithms are powerful computational tools used extensively for the recognition of patterns in large data sets. Here, we investigated the utility of various ML algorithms for the automated biochemical interpretation of urine steroid profiles to support current clinical practices. METHODS Data from 4619 urine steroid profiles processed between June 2012 and October 2016 were retrospectively collected. Of these, 1314 profiles were used to train and test various ML classifiers' abilities to differentiate between “No significant abnormality” and “?Abnormal” profiles. Further classifiers were trained and tested for their ability to predict the specific biochemical interpretation of the profiles. RESULTS The best performing binary classifier could predict the interpretation of No significant abnormality and ?Abnormal profiles with a mean area under the ROC curve of 0.955 (95% CI, 0.949–0.961). In addition, the best performing multiclass classifier could predict the individual abnormal profile interpretation with a mean balanced accuracy of 0.873 (0.865–0.880). CONCLUSIONS Here we have described the application of ML algorithms to the automated interpretation of urine steroid profiles. This provides a proof-of-concept application of ML algorithms to complex clinical laboratory data that has the potential to improve laboratory efficiency in a setting of limited staff resources.

Pathophysiology and prevention of sputum retention

2016 ◽  
Author(s):  
John J. Marini ◽  
Paolo Formenti
Keyword(s):  
Work Of Breathing ◽  
Traumatic Experience ◽  
Prone Positioning ◽  
Normal Flow ◽  
Airway Patency ◽  
Peripheral Airways ◽  
Total Body ◽  
Central Airway ◽  
Airway Suctioning ◽  
P Retention

Retention of airway mucus is one of the major problem that confronts post-operative and critically-ill patients, as well as the caregivers that address it. Retained secretions increase the work of breathing and promote hypoxaemia, atelectasis, and pneumonia. The airway-intubated patient is at particular risk of retaining mucus, as the presence of the tube interrupts normal flow of airway secretions toward the larynx by the mucociliary escalator and coughing effectiveness is degraded by a glottis that is stented open and cannot close effectively. Clearance of mucus is aided by using sufficient gas stream and total body hydration to reduce sputum viscosity and lubricate secretion plugs. Airway suctioning, a routine, but inherently traumatic experience for the patient, may clear the central airway, but leave peripheral airways unrelieved of their secretion burden. Prone positioning appears to confer an advantage regarding secretion drainage and clearance. Physiotherapy techniques may be useful in re-establishing and maintaining airway patency.

A comparison of methods used to quantify the work of breathing during exercise

2021 ◽  
Author(s):  
Troy James Cross ◽  
Elizabeth A. Gideon ◽  
Sarah J. Morris ◽  
Catherine L. Coriell ◽  
Colin D. Hubbard ◽  
...  
Keyword(s):  
Gold Standard ◽  
Respiratory Mechanics ◽  
Work Of Breathing ◽  
Specific Method ◽  
Campbell Diagram ◽  
Volitional Exhaustion ◽  
Volume Integration ◽  
Graded Exercise ◽  
Systematic Pattern ◽  
No Gold Standard

The mechanical work of breathing (Wb) is an insightful tool used to assess respiratory mechanics during exercise. There are several different methods used to calculate the Wb, however - each approach having its own distinct advantages/disadvantages. To date, a comprehensive assessment of the differences in the components of Wb between these methods is lacking. We therefore sought to compare the values of Wb during graded exercise as determined via the 4 most popular methods: (i) pressure-volume integration; (ii) the Hedstrand diagram; (iii) the Otis diagram; and the (iv) modified Campbell diagram. Forty-two participants (30 ± 15 years; 16 women) performed graded cycling to volitional exhaustion. Oesophageal pressure-volume loops were obtained throughout exercise. These data were used to calculate the total Wb and, where possible, its subcomponents of inspiratory and expiratory, resistive and elastic Wb, using each of the 4 methods. Our results demonstrate that the components of Wb were indeed different between methods across the minute ventilations engendered by graded exercise (P < 0.05). Importantly, however, no systematic pattern in these differences could be observed. Our findings indicate that the values of Wb obtained during exercise are uniquely determined by the specific method chosen to compute its value - no two methods yield identical results. Because there is currently no "gold-standard" for measuring the Wb, it is emphasized that future investigators be cognizant of the limitations incurred by their chosen method, such that observations made by others may be interpreted with greater context, and transparency.

Respiratory and cardiovascular systems

2011 ◽  
pp. 353-472
Keyword(s):  
Soft Tissue ◽  
Respiratory Mechanics ◽  
Pulmonary Perfusion ◽  
Upper Airways ◽  
Pulmonary System ◽  
System P ◽  
P Diffusion ◽  
Lower Airways ◽  
Cardiovascular Systems

The thorax Anatomy of the thorax and lungs 354 Skeletal and soft tissue framework of the thorax 356 The pulmonary system Pleura and pleural cavities 360 Upper airways 362 Lower airways 372 Respiratory mechanics—static 376 Respiratory mechanics—dynamic 380 Diffusion 382 Ventilation 384 Pulmonary perfusion 386...

scholarly journals Análise da Revisão Cochrane: Antihistamínicos para a Constipação. Cochrane Database Syst Rev. 2015;11:CD009345.

2016 ◽  
Vol 29 (3) ◽  
pp. 164
Author(s):  
Carmel Sterrantino ◽  
Gonçalo Duarte ◽  
João Costa ◽  
António Vaz-Carneiro
Keyword(s):  
Beneficial Effect ◽  
Common Cold ◽  
Randomized Clinical Trials ◽  
Nasal Congestion ◽  
Cochrane Review ◽  
Adult Patients ◽  
Upper Airways ◽  
Runny Nose ◽  
Increased Risk ◽  
The Individual

The common cold is an acute, self-limiting inflammation of the mucosa of the upper airways, which may involve one or all the sinuses, nasopharynx, oropharynx and larynx. It is common to have at least one episode per year. Common cold symptoms, which may include sore throat, sneezing, nasal congestion, runny nose, headache, malaise and mild fever usually disappear within a few days without treatment. The causative agent of most colds is rhinovirus. Although not associated with mortality, common cold is associated with significant morbidity. There is no vaccine or cure for common cold and, therefore, their treatment is centered on relieving the symptoms. This Cochrane review aimed to synthesize the existing evidence about the clinical benefit of antihistamines, used as monotherapy, compared with placebo or no treatment in children and adult patients with common cold. A total of 18 randomized clinical trials with 4342 participants were included. Main results were: 1) Antihistamines have a small (days one and two) beneficial effect in the short term on the severity of overall symptoms in adult patients, although this effect is not present in the medium to long term; 2) antihistamines were not associated with a clinically significant beneficial effect on the individual symptoms (nasal congestion, rhinorrhea, and sneezing); 3) Antihistamines are not associated with an increased risk of adverse effects; 4) No conclusion can be made about the effectiveness of antihistamines in pediatric populations. Our interpretation of the results is that the available evidence is insufficient to support the prescription or buying OTC antihistamines to relieve the symptoms of common cold without allergic component.

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