scholarly journals Physiological mechanisms of dyspnea during exercise with external thoracic restriction: Role of increased neural respiratory drive

2014 ◽  
Vol 116 (5) ◽  
pp. 570-581 ◽  
Author(s):  
Cassandra T. Mendonca ◽  
Michele R. Schaeffer ◽  
Patrick Riley ◽  
Dennis Jensen
Keyword(s):  
Tidal Volume ◽  
Balloon Catheter ◽  
Respiratory Drive ◽  
Exercise Tests ◽  
Transdiaphragmatic Pressure ◽  
Pressure Time ◽  
Sensory Intensity ◽  
Dynamic Operating ◽  
Mechanistic Basis ◽  
The Relationship

We tested the hypothesis that neuromechanical uncoupling of the respiratory system forms the mechanistic basis of dyspnea during exercise in the setting of “abnormal” restrictive constraints on ventilation (VE). To this end, we examined the effect of chest wall strapping (CWS) sufficient to mimic a “mild” restrictive lung deficit on the interrelationships between VE, breathing pattern, dynamic operating lung volumes, esophageal electrode-balloon catheter-derived measures of the diaphragm electromyogram (EMGdi) and the transdiaphragmatic pressure time product (PTPdi), and sensory intensity and unpleasantness ratings of dyspnea during exercise. Twenty healthy men aged 25.7 ± 1.1 years (means ± SE) completed symptom-limited incremental cycle exercise tests under two randomized conditions: unrestricted control and CWS to reduce vital capacity (VC) by 21.6 ± 0.5%. Compared with control, exercise with CWS was associated with 1) an exaggerated EMGdi and PTPdi response; 2) no change in the relationship between EMGdi and each of tidal volume (expressed as a percentage of VC), inspiratory reserve volume, and PTPdi, thus indicating relative preservation of neuromechanical coupling; 3) increased sensory intensity and unpleasantness ratings of dyspnea; and 4) no change in the relationship between increasing EMGdi and each of the intensity and unpleasantness of dyspnea. In conclusion, the increased intensity and unpleasantness of dyspnea during exercise with CWS could not be readily explained by increased neuromechanical uncoupling but likely reflected the awareness of increased neural respiratory drive (EMGdi) needed to achieve any given VE during exercise in the setting of “abnormal” restrictive constraints on tidal volume expansion.

Sustainable inspiratory pressures over varying flows, volumes, and duty cycles

1990 ◽  
Vol 69 (5) ◽  
pp. 1875-1882 ◽  
Author(s):  
T. L. Clanton ◽  
B. T. Ameredes ◽  
D. B. Thomson ◽  
M. W. Julian
Keyword(s):  
Tidal Volume ◽  
Duty Cycle ◽  
Dynamic Pressure ◽  
Breathing Patterns ◽  
Transdiaphragmatic Pressure ◽  
Lung Inflation ◽  
Duty Cycles ◽  
Pressure Time ◽  
Endurance Tests ◽  
Normal Humans

This study identifies the influence of flow (0.5-2.0 l/s), duty cycle (0.29-0.57), and tidal volume (1.08-2.16 liters) on sustainable inspiratory muscle pressure (Pmus) and transdiaphragmatic pressure (Pdi) development. Six normal humans performed endurance tests using an isoflow method, which allowed for measurements of maximum dynamic Pmus and Pdi, with controlled lung inflation. The subjects repeated maximum dynamic voluntary inspirations for 10 min. Pressures dropped exponentially from initial measurements at rest (Pmusi or Pdi) to sustainable values (Pmus or Pdis). As flow and tidal volume increased, maximum initial and sustainable pressures decreased significantly. However, at a constant duty cycle, the sustainable dynamic pressures remained predictable fractions of initial dynamic pressures (i.e., Pmuss/Pmusi or Pdis/Pdii), regardless of changes in flow and tidal volume. In contrast, as duty cycle increased, the sustainable fractions significantly decreased for both Pdi and Pmus. For example, at a duty cycle of 0.29, Pmuss/Pmusi was approximately 0.71, and at a duty cycle of 0.57, Pmuss/Pmusi was approximately 0.62. Calculated sustainable pressure-time indexes varied significantly between 0.16 to 0.32 for Pmus and 0.11 to 0.22 for Pdi over the breathing patterns studied. We conclude that 1) the maximum dynamic pressure that can be sustained at a given duty cycle is a predictable fraction of the maximum dynamic pressure that can be generated at rest when measured under the same conditions of inspiration and 2) the sustainable fraction of initial dynamic pressure significantly decreases with increasing duty cycle.

scholarly journals Neural respiratory drive and breathlessness in COPD

2014 ◽  
Vol 45 (2) ◽  
pp. 355-364 ◽  
Author(s):  
Caroline J. Jolley ◽  
Yuanming M. Luo ◽  
Joerg Steier ◽  
Gerrard F. Rafferty ◽  
Michael I. Polkey ◽  
...  
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Tidal Volume ◽  
Pulmonary Disease ◽  
Vital Capacity ◽  
Treadmill Exercise ◽  
Forced Expiratory Volume ◽  
Chronic Obstructive ◽  
Respiratory Drive ◽  
Obstructive Pulmonary Disease ◽  
The Relationship

The aim of this study was to test the hypothesis that neural respiratory drive, measured using diaphragm electromyogram (EMGdi) activity expressed as a percentage of maximum (EMGdi%max), is closely related to breathlessness in chronic obstructive pulmonary disease. We also investigated whether neuroventilatory uncoupling contributes significantly to breathlessness intensity over an awareness of levels of neural respiratory drive alone.EMGdi and ventilation were measured continuously during incremental cycle and treadmill exercise in 12 chronic obstructive pulmonary disease patients (forced expiratory volume in 1 s±sd was 38.7±14.5 % pred). EMGdi was expressed both as EMGdi%max and relative to tidal volume expressed as a percentage of predicted vital capacity to quantify neuroventilatory uncoupling.EMGdi%max was closely related to Borg breathlessness in both cycle (r=0.98, p=0.0001) and treadmill exercise (r=0.94, p=0.005), this relationship being similar to that between neuroventilatory uncoupling and breathlessness (cycling r=0.94, p=0.005; treadmill r=0.91, p=0.01). The relationship between breathlessness and ventilation was poor when expansion of tidal volume became limited.In chronic obstructive pulmonary disease the intensity of exertional breathlessness is closely related to EMGdi%max. These data suggest that breathlessness in chronic obstructive pulmonary disease can be largely explained by an awareness of levels of neural respiratory drive, rather than the degree of neuroventilatory uncoupling. EMGdi%max could provide a useful physiological biomarker for breathlessness in chronic obstructive pulmonary disease.

Hypoxic potentiation of the ventilatory response to dynamic forearm exercise

1993 ◽  
Vol 74 (5) ◽  
pp. 2365-2372 ◽  
Author(s):  
R. F. Fregosi ◽  
D. R. Seals
Keyword(s):  
Ventilatory Response ◽  
Respiratory Drive ◽  
O2 Consumption ◽  
Exercise Tests ◽  
Systemic Hypoxia ◽  
Afferent Nerve Endings ◽  
Forearm Exercise ◽  
Response To Exercise ◽  
The Relationship ◽  
Stimulation Of

The slope of the relationship between ventilation (VI) and O2 consumption, as derived in progressive-intensity exercise tests, is increased markedly by systemic hypoxia. The mechanisms underlying the hypoxic potentiation of the ventilatory response to exercise have not been established, partly because several factors that can increase respiratory drive (e.g., metabolic rate, cardiac output, circulating catecholamine levels) change significantly and simultaneously under these conditions. In an effort to avoid these confounding changes, we sought to determine whether hypoxia potentiates the ventilatory response to dynamic forearm exercise in humans. Forearm exercise increased the O2 consumption by only 80–90 ml/min; nevertheless, hypoxia resulted in a significant potentiation of VI that was mediated by a marked increase in breathing frequency. These observations led us to hypothesize that the hypoxic potentiation of VI is due to an exaggerated stimulation of chemosensitive afferent nerve endings within the exercising muscles ("muscle chemoreceptors"). We tested this hypothesis in separate experiments under conditions of forearm ischemia so that the stimulus to the muscle chemoreceptors in normoxic and hypoxic exercise would be the same. The magnitude of the change in VI evoked by hypoxic ischemic exercise was significantly greater than the sum of the separate changes evoked by normoxic ischemic exercise and hypoxic ischemic rest. We conclude that the combination of dynamic forearm exercise and hypoxia potentiates VI and that this effect is mediated by neural structures that govern respiratory frequency. Moreover the potentiated ventilatory response cannot be attributed to an exaggerated stimulation of intramuscular chemoreceptors.

Ventilation standards for small mammals

1964 ◽  
Vol 19 (2) ◽  
pp. 360-362 ◽  
Author(s):  
Leonard I. Kleinman ◽  
Edward P. Radford
Keyword(s):  
Body Weight ◽  
Tidal Volume ◽  
Small Mammals ◽  
Artificial Respiration ◽  
Alveolar Ventilation ◽  
Breathing Frequency ◽  
Slide Rule ◽  
Physiological Dead Space ◽  
The Relationship ◽  
Tidal Volume Breathing

Ventilation standards for small mammals have been prepared on the basis of the relationship between alveolar ventilation and metabolism. On the assumptions of an average respiratory quotient of 0.85 and physiological dead space directly proportional to tidal volume, the relationship between tidal volume, breathing frequency, and body weight has been derived. The standards are presented in a graphic form and as a slide rule. animal ventilation; artificial respiration; tidal volume, breathing frequency and body weight relationship Submitted on August 15, 1963

Threshold for muscle lactate accumulation during progressive exercise

1989 ◽  
Vol 66 (6) ◽  
pp. 2710-2716 ◽  
Author(s):  
J. Chwalbinska-Moneta ◽  
R. A. Robergs ◽  
D. L. Costill ◽  
W. J. Fink
Keyword(s):  
Blood Lactate ◽  
Bicycle Ergometer ◽  
Exercise Tests ◽  
Muscle Lactate ◽  
Lactate Accumulation ◽  
Ergometer Exercise ◽  
Progressive Exercise ◽  
Blood Lactate Accumulation ◽  
Highly Correlated ◽  
The Relationship

The purpose of this study was to investigate the relationship between muscle and blood lactate concentrations during progressive exercise. Seven endurance-trained male college students performed three incremental bicycle ergometer exercise tests. The first two tests (tests I and II) were identical and consisted of 3-min stage durations with 2-min rest intervals and increased by 50-W increments until exhaustion. During these tests, blood was sampled from a hyperemized earlobe for lactate and pH measurement (and from an antecubital vein during test I), and the exercise intensities corresponding to the lactate threshold (LT), individual anaerobic threshold (IAT), and onset of blood lactate accumulation (OBLA) were determined. The test III was performed at predetermined work loads (50 W below OBLA, at OBLA, and 50 W above OBLA), with the same stage and rest interval durations of tests I and II. Muscle biopsies for lactate and pH determination were taken at rest and immediately after the completion of the three exercise intensities. Blood samples were drawn simultaneously with each biopsy. Muscle lactate concentrations increased abruptly at exercise intensities greater than the “below-OBLA” stage [50.5% maximal O2 uptake (VO2 max)] and resembled a threshold. An increase in blood lactate and [H+] also occurred at the below-OBLA stage; however, no significant change in muscle [H+] was observed. Muscle lactate concentrations were highly correlated to blood lactate (r = 0.91), and muscle-to-blood lactate ratios at below-OBLA, at-OBLA, and above-OBLA stages were 0.74, 0.63, 0.96, and 0.95, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Patient-ventilator interaction during acute hypercapnia: pressure-support vs. proportional-assist ventilation

1996 ◽  
Vol 81 (1) ◽  
pp. 426-436 ◽  
Author(s):  
V. M. Ranieri ◽  
R. Giuliani ◽  
L. Mascia ◽  
S. Grasso ◽  
V. Petruzzelli ◽  
...  
Keyword(s):  
Respiratory Rate ◽  
Dead Space ◽  
Pressure Support ◽  
Esophageal Pressure ◽  
Respiratory Drive ◽  
Resistive Load ◽  
Proportional Assist Ventilation ◽  
Pressure Time ◽  
Pressure Time Product ◽  
Stimulation Of

The objective of this study was to compare patient-ventilator interaction during pressure-support ventilation (PSV) and proportional-assist ventilation (PAV) in the course of increased ventilatory requirement obtained by adding a dead space in 12 patients on weaning from mechanical ventilation. With PSV, the level of unloading was provided by setting the inspiratory pressure at 20 and 10 cmH2O, whereas with PAV the level of unloading was at 80 and 40% of the elastic and resistive load. Hypercapnia increased (P < 0.001) tidal swing of esophageal pressure and pressure-time product per breath at both levels of PSV and PAV. During PSV, application of dead space increased ventilation (VE) during PSV (67 +/- 4 and 145 +/- 5% during 20 and 10 cmH2O PSV, respectively, P < 0.001). This was due to a relevant increase in respiratory rate (48 +/- 4 and 103 +/- 5% during 20 and 10 cmH2O PSV, respectively, P < 0.001), whereas the increase in tidal volume (VT) played a small role (13 +/- 1 and 21 +/- 2% during 20 and 10 cmH2O PSV, respectively, P < 0.001). With PAV, the increase in VE consequent to hypercapnia (27 +/- 3 and 64 +/- 4% during 80 and 40% PAV, respectively, P < 0.001) was related to the increase in VT (32 +/- 1 and 66 +/- 2% during 80 and 40% PAV, respectively, P < 0.001), respiratory rate remaining unchanged. The increase in pressure-time product per minute and per liter consequent to acute hypercapnia and the sense of breathlessness were significantly (P < 0.001) higher during PSV than during PAV. Our data show that, after hypercapnic stimulation of the respiratory drive, the capability to increase VE through changes in VT modulated by variations in inspiratory muscle effort is preserved only during PAV; the compensatory strategy used to increase VE during PSV requires greater muscle effort and causes more pronounced patient discomfort than during PAV.

scholarly journals Mechanisms of exercise intolerance in Global Initiative for Chronic Obstructive Lung Disease grade 1 COPD

2014 ◽  
Vol 44 (5) ◽  
pp. 1177-1187 ◽  
Author(s):  
Jordan A. Guenette ◽  
Roberto C. Chin ◽  
Sicheng Cheng ◽  
Paolo B. Dominelli ◽  
Natya Raghavan ◽  
...  
Keyword(s):  
Work Of Breathing ◽  
Pressure Ratio ◽  
Chronic Obstructive Lung Disease ◽  
Exercise Intolerance ◽  
Chronic Obstructive ◽  
Respiratory Drive ◽  
Obstructive Pulmonary Disease ◽  
Transdiaphragmatic Pressure ◽  
Generating Capacity ◽  
Neuromuscular Abnormalities

The purpose of this study was to determine if a dissociation existed between respiratory drive, as estimated by diaphragmatic electromyography (EMGdi), and its pressure-generating capacity during exercise in mild chronic obstructive pulmonary disease (COPD) and whether this, if present, had negative sensory consequences.Subjects meeting spirometric criteria for mild COPD (n=16) and age and sex-matched controls (n=16) underwent detailed pulmonary function testing and a symptom limited cycle test while detailed ventilatory, sensory and respiratory mechanical responses were measured.Compared with controls, subjects with mild COPD had greater ventilatory requirements throughout submaximal exercise. At the highest equivalent work rate of 60 W, they had a significantly higher: total work of breathing (32±17 versus 16±7 J·min−1; p<0.01); EMGdi (37.3±17.3 versus 17.9±11.7% of maximum; p<0.001); and EMGdi to transdiaphragmatic pressure ratio (0.87±0.38 versus 0.52±0.27; p<0.01). Dyspnoea–ventilation slopes were significantly higher in mild COPD than controls (0.17±0.12 versus 0.10±0.05; p<0.05). However, absolute dyspnoea ratings reached significant levels only at high levels of ventilation.Increased respiratory effort and work of breathing, and a wider dissociation between diaphragmatic activation and pressure-generating capacity were found at standardised work rates in subjects with mild COPD compared with controls. Despite these mechanical and neuromuscular abnormalities, significant dyspnoea was only experienced at higher work rates.

Abstract 13216: Initial Survey of Respiratory Mechanics During Prehospital Bag Ventilation

Circulation ◽  
2021 ◽  
Vol 144 (Suppl_2) ◽  
Author(s):  
Betty Y Yang ◽  
Jennifer E Blackwood ◽  
Jenny Shin ◽  
Sally Guan ◽  
Mengqi Gao ◽  
...  
Keyword(s):  
Tidal Volume ◽  
Respiratory Mechanics ◽  
Predicted Body Weight ◽  
Convenience Sample ◽  
Measuring Device ◽  
Respiratory Parameters ◽  
Initial Survey ◽  
Post Intubation ◽  
End Tidal ◽  
The Relationship

Introduction: Respiratory mechanics, such as tidal volume and inspiratory pressures, affect outcome in hospitalized patients with respiratory failure. The ability to accurately measure respiratory mechanics in the prehospital setting is limited, thus the relationship between prehospital respiratory mechanics and clinical outcome is not well understood. In this feasibility study, we examined respiratory mechanics of bag-valve mask (BVM) ventilation by emergency medical services (EMS) using a novel in-line measuring device during a period when agencies switched from larger to smaller ventilation bags. Methods: This prospective cohort study included a convenience sample of adult patients who received BVM ventilation by EMS, from August 2018 to January 2020, in Bellevue, Washington. The airway monitoring device was applied by paramedics after intubation to passively record in black box mode, until termination of efforts or hospital arrival. Respiratory parameters included tidal volume, airway pressure, flow rates, end-tidal carbon dioxide, and respiratory rate. Prehospital agencies transitioned from large (1500 mL) to small (1000 mL) ventilation bags during the study period. Results: 7371 post-intubation breaths were measured in 54 patients, 32 treated for out-of-hospital cardiac arrest (OHCA) and 22 treated for non-arrest conditions, primarily respiratory etiology. EMS ventilated 19 patients with a small bag and 35 patients with a large bag. Ventilation with a smaller bag was characterized by less variability in tidal volumes and higher proportion of breaths delivered within 4-10 mL/kg of predicted body weight (Figure) (p<0.05). Conclusions: Respiratory mechanics can be measured in EMS patients receiving BVM ventilation following intubation. Ventilation with a smaller bag might reduce variation in tidal volume, but further study is needed. These data provide the first evaluation of respiratory mechanics during manual ventilation provided by EMS.

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