THE RATIO OF NEURAL DRIVE TO TIDAL VOLUME MEASURED FROM SURFACE ELECTRODES CAN DETECT CLINICALLY SIGNIFICANT FALLS IN FEV1 IN ASTHMATIC SUBJECTS DURING HISTAMINE CHALLENGE

The potential for acute shortages of ventilators at the peak of the COVID-19 pandemic has raised the possibility of needing to support two patients from a single ventilator. To provide a system for understanding and prototyping designs, we have developed a mathematical model of two patients supported by a mechanical ventilator. We propose a standard set-up where we simulate the introduction of T-splitters to supply air to two patients and a modified set-up where we introduce a variable resistance in each inhalation pathway and one-way valves in each exhalation pathway. Using the standard set-up, we demonstrate that ventilating two patients with mismatched lung compliances from a single ventilator will lead to clinically significant reductions in tidal volume in the patient with the lowest respiratory compliance. Using the modified set-up, we demonstrate that it could be possible to achieve the same tidal volumes in two patients with mismatched lung compliances, and we show that the tidal volume of one patient can be manipulated independently of the other. The results indicate that, with appropriate modifications, two patients could be supported from a single ventilator with independent control of tidal volumes.

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

Journal of Applied Physiology ◽

10.1152/japplphysiol.00691.2017 ◽

2018 ◽

Vol 124 (2) ◽

pp. 356-363 ◽

Cited By ~ 11

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.

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Blunted perception of neural respiratory drive and breathlessness in patients with cystic fibrosis

ERJ Open Research ◽

10.1183/23120541.00057-2015 ◽

2016 ◽

Vol 2 (1) ◽

pp. 00057-2015 ◽

Cited By ~ 6

Author(s):

Charles C. Reilly ◽

Caroline J. Jolley ◽

Caroline Elston ◽

John Moxham ◽

Gerrard F. Rafferty

Keyword(s):

Cystic Fibrosis ◽

Total Lung Capacity ◽

Forced Expiratory Volume ◽

Respiratory Drive ◽

Healthy Individuals ◽

Surface Electrodes ◽

Lung Capacity ◽

Clinically Significant ◽

The Right ◽

The Relationship

The electromyogram recorded from the diaphragm (EMGdi) and parasternal intercostal muscle using surface electrodes (sEMGpara) provides a measure of neural respiratory drive (NRD), the magnitude of which reflects lung disease severity in stable cystic fibrosis. The aim of this study was to explore perception of NRD and breathlessness in both healthy individuals and patients with cystic fibrosis. Given chronic respiratory loading and increased NRD in cystic fibrosis, often in the absence of breathlessness at rest, we hypothesised that patients with cystic fibrosis would be able to tolerate higher levels of NRD for a given level of breathlessness compared to healthy individuals during exercise.15 cystic fibrosis patients (mean forced expiratory volume in 1 s (FEV1) 53.5% predicted) and 15 age-matched, healthy controls were studied. Spirometry was measured in all subjects and lung volumes measured in the cystic fibrosis patients. EMGdi and sEMGpara were recorded at rest and during incremental cycle exercise to exhaustion and expressed as a percentage of maximum (% max) obtained from maximum respiratory manoeuvres. Borg breathlessness scores were recorded at rest and during each minute of exercise.EMGdi % max and sEMGpara % max and associated Borg breathlessness scores differed significantly between healthy subjects and cystic fibrosis patients at rest and during exercise. The relationship between EMGdi % max and sEMGpara % max and Borg score was shifted to the right in the cystic fibrosis patients, such that at comparable levels of EMGdi % max and sEMGpara % max the cystic fibrosis patients reported significantly lower Borg breathlessness scores compared to the healthy individuals. At Borg score 1 (clinically significant increase in breathlessness from baseline) corresponding levels of EMGdi % max (20.2±12% versus 32.15±15%, p=0.02) and sEMGpara % max (18.9±8% versus 29.2±15%, p=0.04) were lower in the healthy individuals compared to the cystic fibrosis patients.In the cystic fibrosis patients EMGdi % max at Borg score 1 was related to the degree of airways obstruction (FEV1) (r=−0.664, p=0.007) and hyperinflation (residual volume/total lung capacity) (r=0.710, p=0.03). This relationship was not observed for sEMGpara % max.These data suggest that compared to healthy individuals, patients with cystic fibrosis can tolerate much higher levels of NRD before increases in breathlessness from baseline become clinically significant. EMGdi % max and sEMGpara % max provide physiological tools with which to elucidate factors underlying inter-individual differences in breathlessness perception.

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Discharge frequencies of single motor units in human diaphragm and parasternal muscles in lying and standing

Journal of Applied Physiology ◽

10.1152/jappl.2001.90.1.147 ◽

2001 ◽

Vol 90 (1) ◽

pp. 147-154 ◽

Cited By ~ 24

Author(s):

J. E. Butler ◽

D. K. McKenzie ◽

S. C. Gandevia

Keyword(s):

Tidal Volume ◽

Motor Unit ◽

Motor Units ◽

Neural Drive ◽

Unit Discharge ◽

Single Motor Unit ◽

Single Motor ◽

Single Motor Units ◽

Inspiratory Muscles ◽

Motor Unit Discharge

Single motor unit discharge was measured directly in diaphragm and parasternal intercostal muscles to determine whether neural drive to human inspiratory muscles changes between lying and standing. The final discharge frequency of diaphragmatic motor units increased slightly, by 1 Hz (12%; P < 0.01), when subjects were standing [182 units, median 9.1 Hz (interquartile range 7.6–11.3 Hz)] compared with lying supine [159 units, 8.1 Hz (6.6–10.3 Hz)]. However, this increase with standing occurred in only two of six subjects, in one of whom tidal volume increased significantly during standing. Parasternal intercostal motor unit final discharge frequencies did not differ between standing [116 units, 8.0 Hz (6.6–9.6 Hz)] and lying [124 units, 8.4 Hz (7.0–10.3 Hz)]. The discharge frequencies at the onset of inspiration did not differ between lying and standing for either muscle. A larger proportion of motor units in both inspiratory muscles had postinspiratory or tonic expiratory activity for lying compared with standing (15 vs. 4%; P < 0.05). We conclude that there is no major difference in the phasic inspiratory drive to the diaphragm with the change in posture.

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Adaptation of anesthetized men to breathing through an inspiratory resistor

Journal of Applied Physiology ◽

10.1152/jappl.1976.41.3.285 ◽

1976 ◽

Vol 41 (3) ◽

pp. 285-291 ◽

Cited By ~ 24

Author(s):

W. A. Whitelaw ◽

J. P. Derenne ◽

J. Couture ◽

J. Milic-Emili

Keyword(s):

Carbon Dioxide ◽

Tidal Volume ◽

Respiratory Muscles ◽

Respiratory Frequency ◽

Chemical Stimulus ◽

Pressure Waves ◽

Resistive Load ◽

Occlusion Pressure ◽

Neural Drive ◽

Normal Men

Normal men anesthetized with methoxyflurane rebreathed carbon dioxide under two conditions. In one case they breathed most of the time through a low-resistance circuit and an inspiratory resistor of 40.4 cmH2O/1-s-1 was applied at intervals. In another case they breathed most of the time through the resistor and were allowed occasional free breaths. There were no differences between the two types of runs in tidal volume, respiratory frequency, duration of inspiration of loaded or unloaded breaths, or in amplitude or shape of occlusion pressure waves. It is concluded that the reaction of conscious men to an inspiratory resistive load, consisting of a compensatory augmentation of neural drive to respiratory muscles that does not depend on a chemical stimulus, is absent in anesthetized men.

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Tidal Volume in Pediatric Ventilation: Do You Get What You See?

Journal of Clinical Medicine ◽

10.3390/jcm11010098 ◽

2021 ◽

Vol 11 (1) ◽

pp. 98

Author(s):

Erik Koomen ◽

Joppe Nijman ◽

Ben Nieuwenstein ◽

Teus Kappen

Keyword(s):

Tidal Volume ◽

Clinical Decision Making ◽

Clinical Care ◽

Pediatric Intensive Care ◽

Clinical Decision ◽

Lung Protective Ventilation ◽

Mechanical Ventilators ◽

Technical Factors ◽

Clinically Significant ◽

The University

Mechanical ventilators are increasingly evolving into computer-driven devices. These technical advancements have impact on clinical decisions in pediatric intensive care units (PICUs). A good understanding of the design of mechanical ventilators can improve clinical care. Tidal volume (TV) is one of the corner stones of ventilation: multiple technical factors influence the TV and, thus, influence clinical decision making. Ventilator manufacturers make various design choices regarding the phase, site and conditions of TV measurement as well as algorithmic processing choices. Such choice may impact the measurement and subsequent display of TV. A software change of the TV measuring algorithm of the SERVO-i® (Getinge, Solna, Sweden) at the PICU of the University Medical Centre Utrecht was studied in a prospective cohort. It showed, as example, a clinically significant impact of 8% difference in reported TV. Design choices in both the hardware and software of mechanical ventilators can have a clinically relevant impact on the measurement of tidal volume. In our search for the optimal TV for lung-protective ventilation, such choices should be taken into account.

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Chest Physiotherapy for Mechanically Ventilated Children: A Systematic Review

Journal of Pediatric Intensive Care ◽

10.1055/s-0041-1732448 ◽

2021 ◽

Author(s):

Emma Shkurka ◽

Jo Wray ◽

Mark Peters ◽

Harriet Shannon

Keyword(s):

Systematic Review ◽

Tidal Volume ◽

Clinical Importance ◽

Pediatric Intensive Care ◽

Chest Physiotherapy ◽

Mechanically Ventilated ◽

Sustained Change ◽

Clinically Significant ◽

Critical Appraisal Skills ◽

The Impact

AbstractThe aim of this study was to appraise and summarize the effects of chest physiotherapy in mechanically ventilated children. A systematic review was completed by searching Medline, Embase, Cinahl Plus, PEDro, and Web of Science from inception to February 9, 2021. Studies investigating chest physiotherapy for mechanically ventilated children (0–18 years), in a pediatric intensive care unit were included. Chest physiotherapy was defined as any intervention performed by a qualified physiotherapist. Measurements of effectiveness and safety were included. Exclusion criteria included preterm infants, children requiring noninvasive ventilation, and those in a nonacute setting. Thirteen studies met the inclusion criteria: two randomized controlled trials, three randomized crossover trials, and eight observational studies. The Cochrane risk of bias and the Critical Appraisal Skills Program tools were used for quality assessment. Oxygen saturations decreased after physiotherapy involving manual hyperinflations (MHI) and chest wall vibrations (CWV). Although statistically significant, these results were not of clinical importance. In contrast, oxygen saturations improved after the expiratory flow increase technique; however, this was not clinically significant. An increase in expiratory tidal volume was demonstrated 30 minutes after MHI and CWV. There was no sustained change in tidal volume following a physiotherapy-led recruitment maneuver. Respiratory compliance and dead-space increased immediately after MHI and CWV. Atelectasis scores improved following intrapulmonary percussive ventilation, and MHI and CWV. Evidence to support chest physiotherapy in ventilated children remains inconclusive. There are few high-quality studies, with heterogeneity in interventions and populations. Future studies are required to investigate multiple physiotherapy interventions and the impact on long-term outcomes.

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Histamine challenge and bronchodilator tests assessed by the ratio of diaphragm EMG to tidal volume

10.1183/13993003.congress-2015.pa1033 ◽

2015 ◽

Author(s):

Bai-Ting He ◽

Ning Zhang ◽

Lian Zhou ◽

Jing Wang ◽

John Moxham ◽

...

Keyword(s):

Tidal Volume ◽

Histamine Challenge

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A Simulated Single Ventilator / Dual Patient Ventilation Strategy for Acute Respiratory Distress Syndrome During the COVID-19 Pandemic

10.1101/2020.04.07.20056309 ◽

2020 ◽

Cited By ~ 1

Author(s):

José A. Solís-Lemus ◽

Edward Costar ◽

Denis Doorly ◽

Eric C. Kerrigan ◽

Caroline H. Kennedy ◽

...

Keyword(s):

Mathematical Model ◽

Acute Respiratory Distress Syndrome ◽

Respiratory Distress Syndrome ◽

Tidal Volume ◽

Distress Syndrome ◽

The Other ◽

Mechanical Ventilator ◽

Ventilation Strategy ◽

Respiratory Compliance ◽

Clinically Significant

AbstractThe potential for acute shortages of ventilators at the peak of the Covid-19 pandemic has raised the possibility of needing to support two patients from a single ventilator. To provide a system for understanding and prototyping designs we have developed a mathematical model of two patients supported by a mechanical ventilator. We propose a standard setup where we simulate the introduction of T-splitters to supply air to two patients and a modified setup where we introduce a variable resistance in each inhalation pathway and one-way valves in each exhalation pathway. Using the standard setup, we demonstrate that ventilating two patients with mismatched lung compliances from a single ventilator will lead to clinically-significant reductions in tidal volume in the patient with the lowest respiratory compliance. Using the modified setup, we demonstrate that it could be possible to achieve the same tidal volumes in two patients with mismatched lung compliances, and we show that the tidal volume of one patient can be manipulated independently of the other. The results indicate that, with appropriate modifications, two patients could be supported from a single ventilator with independent control of tidal volumes.

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