Effects of lung volume on diaphragm EMG signal strength  during voluntary contractions

Beck, Jennifer; Sinderby, Christer A.; Lindström, Lars; Grassino, A.

doi:10.1152/jappl.1998.85.3.1123

Cited by 143 publications

(130 citation statements)

References 31 publications

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“…This critique is based on studies of evoked diaphragm compound muscle action potentials (15) or outdated methodology that does not control for interelectrode distance (16). Using appropriate methodology, EAdi obtained during spontaneous breathing is not artifactually influenced by changes in muscle length, chest wall configuration, or lung volume (17,18).…”

Section: Summary Of Findingsmentioning

confidence: 99%

Prolonged Neural Expiratory Time Induced by Mechanical Ventilation in Infants

et al. 2004

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Mechanical ventilation may interfere with the spontaneous breathing pattern in infants because they have strong reflexes that play a large role in the control of breathing. This study aimed to answer the following questions: does a ventilator-assisted breath 1) reduce neural inspiratory time, 2) reduce the amplitude of the diaphragm electrical activity, and 3) prolong neural expiration, within the delivered breath? In 14 infants recovering from acute respiratory failure (mean age and weight were 2.3 Ϯ 1.3 mo and 3.95 Ϯ 0.82 kg, respectively), we measured 1) the electrical activity of the diaphragm with a multiple-array esophageal electrode, and 2) airway opening pressure, while patients breathed on synchronized intermittent mandatory ventilation (mean rate, 11.2 Ϯ 6.5 breaths/min). We compared neural inspiratory and expiratory times for the mandatory breaths and for the spontaneous breaths immediately preceding and following the mandatory breath. Although neural inspiratory time was not different between mandatory and spontaneous breaths, neural expiratory time was significantly increased (p Ͻ 0.001) for the mandatory breaths (953 Ϯ 449 ms) compared with the premandatory and postmandatory spontaneous breaths (607 Ϯ 268 ms and 560 Ϯ 227 ms, respectively). Delivery of the mandatory breath resulted in a reduction in neural respiratory frequency by 28.6 Ϯ 6.4% from the spontaneous premandatory frequency. The magnitude of inspiratory electrical activity of the diaphragm was similar for all three breath conditions. For the mandatory breaths, ventilatory assist persisted for 507 Ϯ 169 ms after the end of neural inspiratory time. Infant-ventilator asynchrony (both inspiratory and expiratory asynchrony) was present in every mandatory breath and constituted 53.4 Ϯ 26.2% of the total breath duration. Newborn infants have strong reflexes that play a large role in the control of breathing (1). The work of Hering and Breuer in 1868 demonstrated in newborn animals that expansion of the lung reflexly inhibits inspiration-the HB inspiratoryinhibiting reflex-and promotes expiration-the HB expiratory-promoting reflex (2). With respect to mechanical ventilation in infants, it is reasonable to expect that delivery of ventilatory assistance should reflexly reduce neural Ti and neural inspiratory activity within the breath delivered. With respect to the HB expiratory-promoting reflex, one would expect an increase in neural Te during the assisted breath, compared with a spontaneous unassisted breath. The expiratory-promoting reflex has been clinically observed in mechanically ventilated infants, but was described with indirect estimates of neural timing (such as airway or esophageal pressure or flow) to gauge its effects (3-5). In addition to the fact that no quantitative evaluation of the reflex was made, the recent work of Parthasarathy et al. (6) has demonstrated that indirect estimates of respiratory timing are in poor agreement with more direct measurements of neural activity.Much of the available literature on reflex control of ...

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Section: Summary Of Findingsmentioning

confidence: 99%

Prolonged Neural Expiratory Time Induced by Mechanical Ventilation in Infants

et al. 2004

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“…Motions of the rib cage and abdomen were monitored by Respitrace bands placed over the rib cage (nipple level) and abdomen (umbilical level). Crural diaphragm electrical activity (Edi) was measured by a multi-array oesophageal electrode [13,15,16].…”

Section: Measurementsmentioning

confidence: 99%

“…The intensity of expiratory muscle contraction was quantified as the phasic increase in gastric pressure during expiration [3, 10±12]. The force generating ability of the diaphragm was defined in the present study as the ability of the diaphragm to generate transdiaphragmatic pressure for a given diaphragm activation, and was assessed as the ratio of peak transdiaphragmatic pressure to peak diaphragm electrical activity [13].…”

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Expiratory muscle pressure and breathing mechanics in chronic obstructive pulmonary disease

Shi¹,

Sinderby²,

Bieleń³

et al. 2000

Eur Respir J

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Expiratory muscle recruitment is common in stable chronic obstructive pulmonary disease (COPD) patients. Due to airway obstruction, there is little reason to believe that active expiration in COPD would be mechanically effective in lowering operating lung volume. The physiological significance of expiratory muscle recruitment in COPD, therefore, remains unknown. The purpose of this study was to assess, in COPD patients breathing at rest, the effect of expiratory muscle contraction on force generating ability of the diaphragm.The force generating ability of the diaphragm was evaluated from its pressure swing (Pdi) for a given diaphragm electrical activity (Edi), where Edi was normalized as % of its maximal value (Pdi/Edi/Edi,max). Phasic expiratory muscle contraction was measured as the total expiratory rise in gastric pressure (Pga,exp.rise).Nineteen seated patients with moderate to severe COPD, participated in the study and 10 exhibited phasic rise in Pga during expiration with a mean Pga,exp.rise of 1.91 0.89 cmH 2 O. The patients were thus divided into passive expiration (PE) and active expiration (AE) groups. There was no significant difference in various lung function and breathing pattern parameters between the two groups. Pdi/Edi/Edi,max was 0.63 0.07 and 0.54 0.07 cmH 2 O/% in PE and AE groups, respectively, and was not significantly different between each other. Compared with PE group, AE group not only recruited expiratory muscles, but also preferentially recruited inspiratory rib cage muscles and derecruited the diaphragm.The results do not support a significant improvement of the force-generating ability of the diaphragm by phasic contraction of expiratory muscles at rest in chronic obstructive pulmonary disease patients. Eur Respir J 2000; 16: 684±690.

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“…Although the diaphragm is at a mechanical disadvantage at higher lung volumes, the EAdi signal is not decreased. In fact, the response to weakened me-chanical output of the diaphragm is an increase in EAdi (12)(13)(14). With respect to cycling-off the ventilator breath, the neural expiration is not detected during PSV, which could lead to overinflation and excessive volume delivery, whereas with NAVA, cycling-off occurs when the diaphragm activity is turned off by the respiratory centers and hence should provide a more physiologic termination of the assist.…”

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confidence: 99%

Improved Synchrony and Respiratory Unloading by Neurally Adjusted Ventilatory Assist (NAVA) in Lung-Injured Rabbits

et al. 2007

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With increasing pressure support ventilation (PSV), a form of pneumatically triggered ventilation, there can be an increase in wasted inspiratory efforts (neural inspiratory efforts that fail to trigger the ventilator). With neurally adjusted ventilatory assist (NAVA), a mode of ventilation controlled by the electrical activity of the diaphragm (EAdi), synchrony should be maintained at high levels of assist. The aim of this study was to evaluate the response to increasing levels of PSV and NAVA on synchrony and diaphragm unloading in lung-injured rabbits. Animals were ventilated on PSV or NAVA in random order, each at three levels. We measured neural and ventilator respiratory rates, EAdi, transdiaphragmatic pressure (Pdi), and tidal volume (VT). At low PSV, 95% of neural efforts were triggered, compared with high PSV, where only 66% of the neural efforts were triggered. During NAVA, all neural efforts were triggered, regardless of level. Increasing NAVA levels reduced EAdi and Pdi-time products by 48% (p Ͻ 0.05) and 66% (p Ͻ 0.05). In contrast, increasing PSV did not reduce the diaphragm electrical activity-time product and increased the transdiaphragmatic pressuretime product (p Ͻ 0.05) due to the increased wasted efforts. We conclude that synchrony with the ventilator is an important determinant for diaphragm unloading. (Pediatr Res 61: 289-294, 2007) P atient-triggered ventilation in the pediatric intensive care unit setting is common (1) and compared with conventional mechanical ventilation has been shown to improve VT (2), work of breathing (2), and oxygenation (3) and to reduce blood pressure fluctuations (4) and transpulmonary pressure (5) in newborns. Despite these findings, a recent meta-analysis indicates that patient-triggered ventilation has no impact on mortality (6). One possible explanation for this may be that even though patient-triggered ventilation was used, synchronous ventilation may not have actually been achieved, an observation not reported in many trials.A common form of patient-triggered ventilation is PSV, a mode of partial ventilatory assist that is triggered by pressure or flow, is pressure targeted, and flow cycled. It is generally believed that increasing the level of assist with PSV unloads the respiratory muscles (7,8). However, investigators have demonstrated there may be a significant amount of respiratory work to trigger the ventilator (9), and there may be wasted inspiratory efforts, where the patient makes an inspiratory effort, but the ventilator fails to trigger. These asynchronies are aggravated at higher levels of assist (9,10) and possibly at higher respiratory rates because expiratory time is too short to allow complete exhalation. Dynamic hyperinflation puts the diaphragm at a mechanical disadvantage, thereby affecting the ability to trigger the ventilator.NAVA is a mode of partial ventilatory assist in which the ventilator is controlled by the electrical activity of the diaphragm (EAdi) (11). The EAdi represents the final neural output of the respiratory c...

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Effects of lung volume on diaphragm EMG signal strength during voluntary contractions

Cited by 143 publications

References 31 publications

Prolonged Neural Expiratory Time Induced by Mechanical Ventilation in Infants

Prolonged Neural Expiratory Time Induced by Mechanical Ventilation in Infants

Expiratory muscle pressure and breathing mechanics in chronic obstructive pulmonary disease

Improved Synchrony and Respiratory Unloading by Neurally Adjusted Ventilatory Assist (NAVA) in Lung-Injured Rabbits

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