The work of breathing in a nonlinear model of respiratory mechanics

2002 ◽  
Author(s):  
A. Athanasiades ◽  
F. Ghorbel ◽  
J.W. Clark ◽  
S.C. Niranjan ◽  
C.H. Liu ◽  
...  
Keyword(s):  
Nonlinear Model ◽  
Respiratory Mechanics ◽  
Work Of Breathing

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.

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.

scholarly journals Increased respiratory neural drive and work of breathing in exercise-induced laryngeal obstruction

2018 ◽  
Vol 124 (2) ◽  
pp. 356-363 ◽  
Author(s):  
Emil S. Walsted ◽  
Azmy Faisal ◽  
Caroline J. Jolley ◽  
Laura L. Swanton ◽  
Matthew J. Pavitt ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Respiratory Mechanics ◽  
Minute Ventilation ◽  
Work Of Breathing ◽  
Neural Drive ◽  
Exertional Dyspnea ◽  
Laryngeal Obstruction ◽  
Laryngeal Closure ◽  
Endoscopic Video ◽  
Exercise Induced

Exercise-induced laryngeal obstruction (EILO), a phenomenon in which the larynx closes inappropriately during physical activity, is a prevalent cause of exertional dyspnea in young individuals. The physiological ventilatory impact of EILO and its relationship to dyspnea are poorly understood. The objective of this study was to evaluate exercise-related changes in laryngeal aperture on ventilation, pulmonary mechanics, and respiratory neural drive. We prospectively evaluated 12 subjects (6 with EILO and 6 healthy age- and gender-matched controls). Subjects underwent baseline spirometry and a symptom-limited incremental exercise test with simultaneous and synchronized recording of endoscopic video and gastric, esophageal, and transdiaphragmatic pressures, diaphragm electromyography, and respiratory airflow. The EILO and control groups had similar peak work rates and minute ventilation (V̇e) (work rate: 227 ± 35 vs. 237 ± 35 W; V̇e: 103 ± 20 vs. 98 ± 23 l/min; P > 0.05). At submaximal work rates (140–240 W), subjects with EILO demonstrated increased work of breathing ( P < 0.05) and respiratory neural drive ( P < 0.05), developing in close temporal association with onset of endoscopic evidence of laryngeal closure ( P < 0.05). Unexpectedly, a ventilatory increase ( P < 0.05), driven by augmented tidal volume ( P < 0.05), was seen in subjects with EILO before the onset of laryngeal closure; there were however no differences in dyspnea intensity between groups. Using simultaneous measurements of respiratory mechanics and diaphragm electromyography with endoscopic video, we demonstrate, for the first time, increased work of breathing and respiratory neural drive in association with the development of EILO. Future detailed investigations are now needed to understand the role of upper airway closure in causing exertional dyspnea and exercise limitation. NEW & NOTEWORTHY Exercise-induced laryngeal obstruction is a prevalent cause of exertional dyspnea in young individuals; yet, how laryngeal closure affects breathing is unknown. In this study we synchronized endoscopic video with respiratory physiological measurements, thus providing the first detailed commensurate assessment of respiratory mechanics and neural drive in relation to laryngeal closure. Laryngeal closure was associated with increased work of breathing and respiratory neural drive preceded by an augmented tidal volume and a rise in minute ventilation.

Effects of induced bronchoconstriction on pulmonary blood flow

1986 ◽  
Vol 60 (6) ◽  
pp. 1960-1966 ◽  
Author(s):  
R. Olgiati ◽  
A. Wanner
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Pulmonary Blood Flow ◽  
Respiratory Mechanics ◽  
Work Of Breathing ◽  
Cardiovascular Effects ◽  
Pleural Pressure ◽  
Similar Degree ◽  
Arterial Blood ◽  
Chemical Mediators

Allergic bronchoconstriction may be associated with hemodynamic alterations due to changes in respiratory mechanics (or the associated changes in arterial blood gas composition) or the cardiovascular effects of chemical mediators. In an attempt to differentiate between these two possible mechanisms, we obtained measurements of hemodynamics, respiratory mechanics, and O2 consumption (VO2) in nine asymptomatic adult ragweed asthmatics before and after inhalation challenge with either ragweed extract or methacholine. We measured specific airway conductance (sGaw) by body plethysmography, pleural pressure with an esophageal balloon catheter, pulmonary blood flow (Q) and VO2 by a rebreathing technique, and heart rate. For a similar degree of bronchoconstriction after the two types of challenge (mean +/- SD sGaw 0.06 +/- 0.03 and 0.05 +/- 0.02 cmH2O–1 . s-1, P = NS), mean Q increased by 29 and 29%, and mean VO2 by 33 and 37% 15–20 min after ragweed and methacholine, respectively. Since heart rate did not change, there was a concomitant increase in mean stroke volume by 25 and 35%, respectively (P less than 0.05). The respiratory pleural pressure swings during quiet breathing and the rebreathing maneuver and the work of breathing during rebreathing also increased to a similar degree after the two types of challenge. These observations suggest that, if chemical mediators are released into the circulation during antigen-induced bronchoconstriction, their blood concentrations are too low for appreciable cardiovascular effects. The increase in rebreathing cardiac output during allergic and nonallergic bronchoconstriction is probably due to increases in intrathoracic pressure swings and in the work of breathing.

scholarly journals Heliox breathing equally influences respiratory mechanics and cycling performance in trained males and females

2015 ◽  
Vol 118 (3) ◽  
pp. 255-264 ◽  
Author(s):  
Sabrina S. Wilkie ◽  
Paolo B. Dominelli ◽  
Benjamin C. Sporer ◽  
Michael S. Koehle ◽  
A. William Sheel
Keyword(s):  
Exercise Performance ◽  
Respiratory Mechanics ◽  
Work Of Breathing ◽  
Time Trial ◽  
Whole Body ◽  
Flow Limitation ◽  
Maximal Aerobic Capacity ◽  
Expiratory Flow Limitation ◽  
Ventilatory Capacity ◽  
Expiratory Flow

In this study we tested the hypothesis that inspiring a low-density gas mixture (helium-oxygen; HeO2) would minimize mechanical ventilatory constraints and preferentially increase exercise performance in females relative to males. Trained male ( n = 11, 31 yr) and female ( n = 10, 26 yr) cyclists performed an incremental cycle test to exhaustion to determine maximal aerobic capacity (V̇o2max; male = 61, female = 56 ml·kg−1·min−1). A randomized, single-blinded crossover design was used for two experimental days where subjects completed a 5-km cycling time trial breathing humidified compressed room air or HeO2 (21% O2:balance He). Subjects were instrumented with an esophageal balloon for the assessment of respiratory mechanics. During the time trial, we assessed the ability of HeO2 to alleviate mechanical ventilatory constraints in three ways: 1) expiratory flow limitation, 2) utilization of ventilatory capacity, and 3) the work of breathing. We found that HeO2 significantly reduced the work of breathing, increased the size of the maximal flow-volume envelope, and reduced the fractional utilization of the maximal ventilatory capacity equally between men and women. The primary finding of this study was that inspiring HeO2 was associated with a statistically significant performance improvement of 0.7% (3.2 s) for males and 1.5% (8.1 s) for females ( P < 0.05); however, there were no sex differences with respect to improvement in time trial performance ( P > 0.05). Our results suggest that the extent of sex-based differences in airway anatomy, work of breathing, and expiratory flow limitation is not great enough to differentially affect whole body exercise performance.

A Novel and Experimental Design for Mechanical Ventilation with Optimal Spontaneous Flow Pattern and WOB Feedback Control

2013 ◽  
Vol 284-287 ◽  
pp. 2189-2193
Author(s):  
Shyan Lung Lin ◽  
San Shan Hung ◽  
Ching Kun Chen ◽  
Hsing Cheng Chang
Keyword(s):  
Mechanical Ventilation ◽  
Feedback Control ◽  
Flow Pattern ◽  
Respiratory Mechanics ◽  
Work Of Breathing ◽  
Respiratory Control ◽  
Respiratory Physiology ◽  
Innovative Design ◽  
Feedback Control Strategy ◽  
Minimum Work

In this study, we proposed an innovative design for mechanical ventilation by applying the previously implemented optimal respiratory control simulator as the controller of an experimental ventilation device. Instead of providing a fixed airflow pattern, an optimal spontaneous flow pattern was optimized by the simulator based on patient’s estimated respiratory mechanics and was applied to drive a ventilation device. We also implemented an experimental ventilation control system, including the simulator, a ventilation device, an artificial lung, and a feedback control mechanism to attain minimum work of breathing during mechanical ventilation. The experiments were elaborated to verify that once patient’s respiratory physiology was significant changed, the breathing signals and measured respiratory mechanics were instantaneously monitored, and the optimization process was renewed by the simulator under the feedback control strategy.

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