Diaphragmatic Activity Research Articles

The relationship between the cholinergic mechanism of toxicity and oxidative stress in rats during subacute diazinon poisoning

Diazinon is an organophosphate pesticide (OP) that has significant potential for accidental and intentional poisoning of wildlife, domestic animals and humans.The aim of the study is to investigate the correlation between cholinesterase activity and oxidative stress parameters in liver and diaphragm by continuous monitoring as a function of time during prolonged use of diazinon.Wistar rats were treated orally with diazinon (55 mg/kg/day): 7, 14, 21 and 28 days. At the end of each period, blood, liver and diaphragm were collected to examine cholinesterase activity and enzymatic/non-enzymatic oxidative stress parameters: superoxide dismutase 1 (SOD1), catalase (CAT), thiobarbituric acid substances (TBARS), protein carbonyl groups.In all four time periods, there was a significant change in acetylcholinesterase (AChE) in erythrocytes and butyrylcholinesterase (BuChE) in blood plasma, CAT in liver and diaphragm and SOD1 in diaphragm. Parameters significantly altered during the cholinergic crisis included: cholinesterases and TBARS in liver and diaphragm and partially SOD1 in liver. Protein carbonyl groups in liver and diaphragm were significantly altered outside the cholinergic crisis. In the liver, there was a very strong negative correlation between BuChE and TBARS in all four time periods and BuChE and CAT on day 7. In the diaphragm, a very strong negative correlation was found between AChE and TBARS at days 7 and 14, and a very strong positive correlation between AChE and SOD1 at days 14, 21 and 28.A better understanding of the relationship between cholinergic overstimulation and oxidative stress may help to better assess health status in prolonged OPs intoxication.

Measuring Expiratory Diaphragm Activity: An Electrifying Tool to Guide Positive End-Expiratory Pressure Strategy in Critically Ill Children?

Measuring Expiratory Diaphragm Activity: An Electrifying Tool to Guide Positive End-Expiratory Pressure Strategy in Critically Ill Children?

Editor's Choice Articles for June.

Editor's Choice Articles for June.

Therapeutic Strategies Targeting Respiratory Recovery after Spinal Cord Injury: From Preclinical Development to Clinical Translation.

High spinal cord injuries (SCIs) lead to permanent functional deficits, including respiratory dysfunction. Patients living with such conditions often rely on ventilatory assistance to survive, and even those that can be weaned continue to suffer life-threatening impairments. There is currently no treatment for SCI that is capable of providing complete recovery of diaphragm activity and respiratory function. The diaphragm is the main inspiratory muscle, and its activity is controlled by phrenic motoneurons (phMNs) located in the cervical (C3-C5) spinal cord. Preserving and/or restoring phMN activity following a high SCI is essential for achieving voluntary control of breathing. In this review, we will highlight (1) the current knowledge of inflammatory and spontaneous pro-regenerative processes occurring after SCI, (2) key therapeutics developed to date, and (3) how these can be harnessed to drive respiratory recovery following SCIs. These therapeutic approaches are typically first developed and tested in relevant preclinical models, with some of them having been translated into clinical studies. A better understanding of inflammatory and pro-regenerative processes, as well as how they can be therapeutically manipulated, will be the key to achieving optimal functional recovery following SCIs.

Effects of caffeine on diaphragmatic activity in preterm infants.

Caffeine is the first-choice drug for the treatment for apnea of prematurity (AOP) in preterm infants and it has been reported that it improves the diaphragm activity. The aim of this study was to evaluate by ultrasound possible changes in diaphragm contractility and motility induced by caffeine. We studied 26 preterm infants with gestational age ≤34 weeks treated with caffeine for the prevention or treatment of AOP. Diaphragmatic ultrasound was performed 15 min (T0 ) before and 60 min (T60 ) after the loading (20 mg/kg) or maintenance (5 mg/kg) dose of caffeine. Diaphragmatic excursion (DE) and thickness at the end of inspiration (DT-in) and expiration (DT-ex), as well as peak velocity of the excursion at the end of inspiration (DT-in) and expiration (DT-ex) increased after administration of both loading and maintenance dose of caffeine. Ultrasounds confirmed that caffeine improves the activity of diaphragm in preterm infants improving its thickness, amplitude of excursions, and contraction velocity. These results are consistent with the effectiveness of caffeine in treating AOP and decreasing the risk of failure of noninvasive respiratory support in preterm infants with respiratory distress syndrome (RDS).

Pressure transmission and electrical diaphragm activity in preterm infants during nasal intermittent positive pressure ventilation-an exploratory prospective physiological study.

Pressure transmission and electrical diaphragm activity in preterm infants during nasal intermittent positive pressure ventilation-an exploratory prospective physiological study.

Closed-loop electrical epidural stimulation restores ipsilesional in-phase diaphragm activity in spontaneously breathing rats after acute C2-hemisection

Epidural electrical stimulation has great promise for recovering many functions after spinal cord injury, including breathing. High-frequency stimulation of the thoracic [DiMarco and Kowalski, 2009] and cervical cord [Gonzalez-Rothi et al. 2017] recovers some phrenic and diaphragm activity. However, open-loop stimulation paradigms induce tonic activity and, thus far, have not elicited recovery of breathing function independent of the stimulation period. We have shown in C2-hemisected rats, closed-loop epidural stimulation (CLES; paced from contralateral diaphragm EMG activity) increases excitability in the respiratory motor network [Malone et al. 2022]; still, the ability of CLES to recover respiratory function following spinal cord injury has not been explored. Here, we hypothesized that CLES can elicit phasic ipsilesional diaphragm activity in C2-hemisected rats without tonic output. To test this, 3-5 month female Sprague-Dawley rats were anesthetized via inhaled isoflurane anesthetic, implanted with stimulating wire electrodes on the dorsal dura at C4 and recording electrodes bilaterally on the diaphragm, and C2-hemisected. After injury, a 15-30 minute recovery to ensure abolishment of ipsilateral diaphragm activity was followed by measurement of spinal motor evoked potentials of the diaphragm, and a baseline recording of diaphragm EMG activity. Biphasic CLES (n=3), set to an amplitude of ¼ the motor threshold, or a sham waiting period (n=3) was delivered for 20 minutes. EMG post processing was done in Spike2 using custom scripts. Stimulated animals received on average 101.8 +/- 22.8 Hz of stimulation during breaths. In stimulated animals, phasic ipsilesional diaphragm EMG activity significantly increased during stimulation (23.7 +/- 1.9 spikes per breath vs 4.32 +/- 1.9 at baseline, p < 0.005). Stimulation did not increase tonic activity of the ipsilesional diaphragm, and ipsilesional diaphragm activity stopped with cessation of stim indicating no spontaneous recovery of activity. Additionally, there was no significant recovery of sham animals during the same period (5.2 +/- 1.9 vs 4.5 +/- 1.9 spikes per breath). Peak EMG activity and modulus of the contralesional diaphragm were significantly elevated from baseline during stimulation (peak value 0.19 +/- 0.015 V vs 0.15 +/- 0.005 V baseline p < 0.05, % change modulus 34.9 +/- 5.9%, p < 0.03). This work represents the first report that CLES can increase phasic diaphragm EMG activity both ipsi- and contralaterally after acute C2-hemisection. Further study is necessary to determine if CLES can elicit similar effects in a chronic model of injury. Additionally, work to determine the mechanism underlying these changes is essential to tailor this therapy for improving breathing function in individuals with spinal cord injury. T32HL134621, R01HL153102, SPARC OT2OD023854 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Modulatory effect of trans-spinal magnetic intermittent theta burst stimulation on diaphragmatic activity following cervical spinal cord contusion in the rat

Transcranial magnetic intermittent theta burst stimulation can enhance the excitability of the cortical region. However, it is unclear whether this approach can modulate spinal neuroplasticity. The present study was designed to investigate hether trans-spinal magnetic intermittent theta burst stimulation can modulate respiratory motor outputs in the rodent model of cervical spinal cord injury. The effect of trans-spinal magnetic intermittent theta burst stimulation on diaphragmatic activity was assessed in adult rats with unilateral cervical spinal cord contusion at 2 weeks post-injury. The result demonstrated that unilateral cervical spinal cord contusion significantly attenuated the inspiratory activity and motor evoked potential of the diaphragm. Trans-spinal magnetic intermittent theta burst stimulation significantly enhanced the inspiratory activity of the diaphragm in cervical spinal cord contused rats. Moreover, inspiratory bursting could be recruited by trans-spinal magnetic intermittent theta burst stimulation in the contused rats without diaphragmatic activity. Notably, the whole body metabolism was also increased by trans-spinal magnetic intermittent theta burst stimulation. These results suggested that trans-spinal magnetic intermittent theta burst stimulation can be considered as a rehabilitative strategy for improving the respiratory activity after cervical spinal cord injury. National science and technology council (111-2636-B-110-001) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Daily low dose ampakine treatment causes a sustained increase in diaphragm activation following chronic cervical spinal cord injury

Cervical spinal cord injuries (SCIs) result in significant and long-lasting respiratory compromise, leading to morbidity and mortality in the SCI patient population. There is a critical need to develop therapies to counter this respiratory insufficiency. Ampakines are positive allosteric modulators of AMPA receptors that have been shown to alleviate respiratory depression following neuromuscular disorders or opioid use. We have recently shown that low dose (5mg/kg) ampakines can stimulate diaphragm muscle activation and increase overall ventilation at acute and sub-acute timepoints post C2 spinal hemisection injury in rats. Our next step in the translation pathway is to transition to a repeated daily ampakine exposure paradigm after a chronic SCI, as part of a rehabilitation approach. Previous studies in hippocampal slices have shown that repeated dosing with ampakines can support long term potentiation mechanisms and upregulate neuroplasticity related genes. In the present study, we hypothesized that daily treatment with ampakines in chronically injured rats will cause a sustained increase in diaphragm motor output following a high cervical SCI. Over the period of 8-12 weeks after C2 spinal hemisection injury, rats received daily intra-peritoneal injections of ampakine CX717 (5 mg/kg, n=8; 4M, 4F) or CX1739 (5 mg/kg, n=8; 4M, 4F) or vehicle (2-hydroxypropyl-beta-cyclodextrin; HPCD; n=8; 4M, 4F). Ventilation was measured using whole body plethysmography and diaphragm electromyogram (EMG) was assessed using in-dwelling muscle electrodes. Recordings were conducted at 8-, 10- and 12-weeks post injury. The acute response to intravenous ampakine administration was also assessed at the chronically injured timepoint of 8 weeks. Both CX717 and CX1739 were effective at stimulating ipsilateral diaphragm muscle activity (51 ± 12% and 32 ± 5% increase, respectively; p=0.002) and tidal volume (19 ± 7% and 25 ± 7% respectively; p=0.002) as compared to the HPCD group (EMG: 4 ± 3%, tidal volume: -3 ± 5%) at 8 weeks post C2 hemisection. The effect of CX717 treatment was sustained up to 15 minutes where as CX1739 returned close to baseline by 15 minutes. With daily ampakine treatment, we observed a progressive increase (treatment effect: p=0.009) in ipsilateral diaphragm EMG output during eupneic breathing at the 10- and 12-week time points in both the CX717 (13 ± 5%, 18 ± 7% respectively) and CX1739 (9 ± 4%, 17 ± 7% respectively) treated groups as compared to the EMG output at the onset of the daily ampakine therapy. No change in EMG output was observed in the daily HPCD group (-2 ± 3%, -0.5 ± 5% respectively). There was no impact of daily ampakine treatment on respiratory rate, which may indicate that the drug is acting on spinal motoneurons (vs. a medullary mechanism). Our data indicates that daily treatment with ampakines is a promising therapy to stimulate long-lasting neuroplastic changes in respiratory circuits to promote functional recovery following SCI. 1R01HL139708-01A1 (DDF), 1 R01 HL153140-01 (DDF), Craig Neilsen Foundation Fellowship (SR) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Exercise Position to Improve Synergy Between the Diaphragm and Pelvic Floor Muscles in Women With Pelvic Floor Dysfunction: A Cross Sectional Study

ObjectiveThis study aimed to investigate the synergy between the diaphragm and pelvic floor muscles (PFM) according to different exercise positions in women with pelvic floor dysfunction. Our secondary aim was to determine the short-term effects of single-week pelvic floor muscle training (PFMT) program on diaphragmatic function. MethodsThe cross-sectional study included 64 women with pelvic floor dysfunction. The participants' diaphragm and abdominal muscle functions during voluntary PFM contraction and relaxation were assessed by surface electromyography and ultrasonography. The surface electromyography assessments were performed in supine (P1), crawling (P2) and sitting (P3) positions. A single week-PFMT was conducted on women who agreed to determine the short-term responses of the diaphragm function. The muscle functions according to exercise positions were compared with Friedman Analysis of Variance, and the short-term effects of single-week PFMT on diaphragm function was analyzed with Wilcoxon Signed-Ranks Test. ResultsThe diaphragm activity during voluntary PFM contraction was highest in P2 before and after single-week PFMT (P < .001). Positive significant correlations were found between the activities diaphragm and abdominal muscles in different exercise positions (P < .05). After single-week PFMT, diaphragm thickness increased (P = .030) in P1, but diaphragm activity did not change in all 3 exercise positions (P > .05). ConclusionThe synergy between the diaphragm and PFM was greater in the crawling position in women with pelvic floor dysfunction. The abdominal muscles seemed to contribute to maintaining this synergy. Therefore, PFMT combined with diaphragmatic breathing exercises in the crawling position should be considered. In addition, single-week PFMT may positively affect diaphragm function in the short-term.

Effects of Stimulus Pattern on Inspiratory Muscle Activation during High Frequency Spinal Cord Stimulation in an Animal Model

Background: High Frequency Spinal Cord Stimulation (HF-SCS) is a unique method of inspiratory muscle activation and has the potential to restore breathing in ventilator dependent tetraplegic subjects. Objective: To evaluate the pattern of diaphragm (D), parasternal (PA) and external intercostal (EI) activation during rectangular vs ramp-shape HF-SCS, compared to spontaneous breathing. Methods: In 8 anesthetized dogs, a stimulating disc electrode was positioned on the ventral surface of the spinal cord at the T2 level. Stimulus train duration for ramp-shape and rectangular HF-SCS was set at 1.3s since this duration approximated that occurring during spontaneous breathing. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes approximated that occurring during SB. The ramp-shape pattern of stimulation was linearly increased from zero to the desired stimulus amplitude. Single motor unit (SMU) EMG activity of the PA, EI and D muscles was assessed during SB and HF-SCS (following spinalization at the C2 level) with rectangular and ramp-shape stimulation patterns, in separate trials. Time of onset (To), b) time to peak discharge frequency (TTP) and c) peak firing frequency (PFF) were measured under each condition. To and TTP were determined relative to the onset of inspiratory flow and expressed as a percentage of inspiratory time (Ti). The patterns of the inspiratory muscle activation during HF-SCS were compared to that obtained during spontaneous breathing. Results: During SB, D was recruited first followed by PA and EI; mean ± SE To was 19.6±1.4, 32.1±2.4 and 40.4±2.3%Ti, respectively. During rectangular HF-SCS, To was 3.0±0.4, 5.8±1.2 and 4.3±0.9%Ti for D, PA and EI, respectively (p&lt;0.05 for each compared to SB). During ramp-shape HF-SCS, To was 23.1±3.7, 33.6±4.5 and 39.9±4.6%Ti for D, PA and EI respectively (NS for each compared to SB). During SB, TTP was 65.2±2.2, 71.0±2.0 and 74.0±2.0%Ti for D, PA and EI. During rectangular HF-SCS, TTP was 30.4±3.7, 25.4±3.3 and 35.2±2.8%Ti, for D, PA and EI (p&lt;0.05 for each compared to SB). During ramp-shape HF-SCS, TTP was 60.5±2.9, 58.2±2.7 and 62.6±6.0%Ti for Dia, PA and EI (p&lt;0.05 for PA and EI compared to SB). During SB, PFF of SMUs of the D, PA and EI were 10.3±0.5, 12.8±0.4 and 12.2±0.7Hz, respectively. However, during rectangular HF-SCS, PFF were 14.0±0.6, 14.7±0.7 and 14.5±0.5Hz for D, PA and EI, respectively (p&lt;0.05 for each compared to SB). During ramp-shape HF-SCS, PFF were 12.3±0.8, 13.8±0.9 and 12.6±1.2 for D, PA and EI, respectively (NS for each compared to SB). Conclusion: Activation of the inspiratory motoneuron pools via HF-SCS is receptive to different patterns of electrical stimulation.Ramp-shape HF-SCS compared to rectangular HF-SCS results in a more physiologic pattern of inspiratory muscle activation. National Institutes of Health grant no. R01 NS105785. Conflict of interest: Dr. A. DiMarco is a founder of and has a significant financial interest in Synapse BioMedical, a manufacturer of diaphragm pacing systems (nos. 5,678,535 and 5,911,218). Dr. A. DiMarco and Dr. K. Kowalski hold the U.S. patents for technology related to the content of this study, Respiratory Muscle Activation by Spinal Cord Stimulation (no. 8,352,036). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Relationship Between Esophageal Pressure and Diaphragm Thickening Fraction in Spontaneously Breathing Sedated Children: A Feasibility Study.

Diaphragm ultrasound is a novel alternative to esophageal pressure measurements in the evaluation of diaphragm function and activity, but data about its reliability in a pediatric setting are lacking. We aimed to compare the esophageal pressure swing (∆Pes, gold standard) with the diaphragmatic thickening fraction (DTF) as a measure of inspiratory effort in sedated children. Additionally, we studied the effect of positive end-expiratory pressure (PEEP) on the end-expiratory thickness of the diaphragm (DTee). Prospective open-label non-randomized interventional physiological cohort study. Operating room in tertiary academic hospital. Children 28 days to 13 years old scheduled for elective surgery with general anesthesia, spontaneously breathing through a laryngeal mask airway, were eligible for inclusion. Exclusion criteria were disorders or previous surgery of the diaphragm, anticipated difficult airway or acute cardiopulmonary disease. All measurements were performed prior to surgery. Patients were subjected to different levels of respiratory load, PEEP and anesthetic depth in a total of seven respiratory conditions. The esophageal pressure and diaphragm thickening fraction were simultaneously recorded for five breaths at each respiratory condition. The relation between ∆Pes and DTF was studied in a mixed model. We analyzed 407 breaths in 13 patients. Both DTF (p = 0.03) and ∆Pes (p = 0.002) could detect respiratory activity, and ∆Pes and DTF were associated across respiratory conditions (p < 0.001; R2 = 31%). With increasing inspiratory load, ∆Pes increased significantly, while DTF did not (p = 0.08). Additionally, DTee did not differ significantly between 10, 5, and 0 cm H2O PEEP (p = 0.08). In spontaneously breathing sedated children and across different respiratory conditions, DTF could differentiate minimal or no inspiratory effort from substantial inspiratory effort and was associated with ∆Pes. Increased efforts resulted in higher ∆Pes but not larger DTF.

Activation of Hippo Pathway Damages Slit Diaphragm by Deprivation of Ajuba Proteins.

Nuclear exclusion of the cotranscription factor YAP, which is a consequence of activation of the Hippo signaling pathway, leads to FSGS and podocyte apoptosis. Ajuba proteins play an important role in the glomerular filtration barrier by keeping the Hippo pathway inactive. In nephrocytes from Drosophila melanogaster , a well-established model system for podocyte research, Ajuba proteins ensure slit diaphragm (SD) formation and function. Hippo pathway activation leads to mislocalization of Ajuba proteins, decreased SD formation, rearrangement of the actin cytoskeleton, and increased SD permeability. Targeting the kinases of the Hippo pathway with specific inhibitors in the glomerulus could, therefore, be a promising strategy for therapy of FSGS. The highly conserved Hippo pathway, which regulates organ growth and cell proliferation by inhibiting transcriptional cofactors YAP/TAZ, plays a special role in podocytes, where activation of the pathway leads to apoptosis. The Ajuba family proteins (Ajuba, LIM domain-containing protein 1 (LIMD1) and Wilms tumor protein 1-interacting protein [WTIP]) can bind and inactivate large tumor suppressor kinases 1 and 2, (LATS1/2) two of the Hippo pathway key kinases. WTIP, furthermore, connects the slit diaphragm (SD), the specialized cell-cell junction between podocytes, with the actin cytoskeleton. We used garland cell nephrocytes of Drosophila melanogaster to monitor the role of Ajuba proteins in Hippo pathway regulation and structural integrity of the SD. Microscopy and functional assays analyzed the interplay between Ajuba proteins and LATS2 regarding expression, localization, interaction, and effects on the functionality of the SD. In nephrocytes, the Ajuba homolog Djub recruited Warts (LATS2 homolog) to the SD. Knockdown of Djub activated the Hippo pathway. Reciprocally, Hippo activation reduced the Djub level. Both Djub knockdown and Hippo activation led to morphological changes in the SD, rearrangement of the cortical actin cytoskeleton, and increased SD permeability. Knockdown of Warts or overexpression of constitutively active Yki prevented these effects. In podocytes, Hippo pathway activation or knockdown of YAP also decreased the level of Ajuba proteins. Ajuba proteins regulate the structure and function of the SD in nephrocytes, connecting the SD protein complex to the actin cytoskeleton and maintaining the Hippo pathway in an inactive state. Hippo pathway activation directly influencing Djub expression suggests a self-amplifying feedback mechanism.

Elevated Diaphragmatic Tonic Activity in PICU Patients: Age-Specific Definitions, Prevalence, and Associations.

Tonic diaphragmatic activity (tonic Edi, i.e., sustained diaphragm activation throughout expiration) reflects diaphragmatic effort to defend end-expiratory lung volumes. Detection of such elevated tonic Edi may be useful in identifying patients who need increased positive end-expiratory pressure. We aimed to: 1) identify age-specific definitions for elevated tonic Edi in ventilated PICU patients and 2) describe the prevalence and factors associated with sustained episodes of high tonic Edi. Retrospective study using a high-resolution database. Single-center tertiary PICU. Four hundred thirty-one children admitted between 2015 and 2020 with continuous Edi monitoring. None. We characterized our definition of tonic Edi using data from the recovery phase of respiratory illness (i.e., final 3 hr of Edi monitoring, excluding patients with significant persistent disease or with diaphragm pathology). High tonic Edi was defined as population data exceeding the 97.5th percentile, which for infants younger than 1 year was greater than 3.2 μV and for older children as greater than 1.9 μV. These thresholds were then used to identify patients with episodes of sustained elevated tonic Edi in the first 48 hours of ventilation (acute phase). Overall, 62 of 200 (31%) of intubated patients and 138 of 222 (62%) of patients on noninvasive ventilation (NIV) had at least one episode of high tonic Edi. These episodes were independently associated with the diagnosis of bronchiolitis (intubated patients: adjusted odds [aOR], 2.79 [95% CI, 1.12-7.11]); NIV patients: aOR, 2.71 [1.24-6.0]). There was also an association with tachypnea and, in NIV patients, more severe hypoxemia. Our proposed definition of elevated tonic Edi quantifies abnormal diaphragmatic activity during expiration. Such a definition may help clinicians to identify those patients using abnormal effort to defend end-expiratory lung volume. In our experience, high tonic Edi episodes are frequent, especially during NIV and in patients with bronchiolitis.

Monitorización del destete ventilatorio en el paciente crítico

The weaning process can be classified as simple, difficult, or prolonged. The incidence of difficult or prolonged weaning varies from 15% to 25%, according to the series. In critically ill patients it accounts for up to 50% of the total time that they are connected to the ventilator. It is very important to monitor weaning to detect the patients in whom it will be prolonged, and to help us in their management and decision making. Firstly, gas exchange and ventilatory mechanics must be monitored, fundamental in all patients on mechanical ventilation (MV). In addition, monitoring specific parameters that provide information on the patient's respiratory effort is strategic in the weaning process. These parameters include occlusion pressure (P0.1), oesophageal pressure (Poes), Negative Inspiratory Force (NIF), also known as Maximum Inspiratory Pressure (MIP), diaphragmatic electric activity (Edi), total work of breathing (WOB), and its components, elastic WOB (eWOB), and resistive WOB (rWOB). Monitoring weaning from mechanical ventilation means we can establish when the conditions have been met to start the weaning process, propose a weaning protocol adapted to the conditions of the patient, and define our post-extubation respiratory care protocol to prevent weaning failure.

Diaphragmatic Activation Correlated with Lumbar Multifidus Muscles and Thoracolumbar Fascia by B-Mode and M-Mode Ultrasonography in Subjects with and without Non-Specific Low Back Pain: A Pilot Study

Background and Objectives: The diaphragm, the lumbar multifidus muscles, and the thoracolumbar fascia (TLF) execute an important role in the stability of the lumbar spine and their morphology has been modified in subjects with non-specific low back pain (NS-LBP). While it is true that three structures correlate anatomically, the possible functional correlation between them has not been investigated previously in healthy subjects nor in subjects with NS-LBP. The aim of the present study was to examine this functional nexus by means of a comparison based on ultrasonographic parameters of the diaphragm, the lumbar multifidus muscles, and the TLF in subjects with and without NS-LBP. Materials and Methods: A sample of 54 (23 NS-LBP and 31 healthy) subjects were included in the study. The thickness and diaphragmatic excursion at tidal volume (TV) and force volume (FV), the lumbar multifidus muscles thickness at contraction and at rest, and the TLF thickness were evaluated using rehabilitative ultrasound imaging (RUSI) by B-mode and M-mode ultrasonography. The diaphragm thickening capacity was also calculated by thickening fraction (TF) at tidal volume and force volume. Results: There were no significant differences recorded between the activation of the diaphragm and the activation of the lumbar multifidus muscles and TLF for each variable, within both groups. However, there were significant differences recorded between both groups in diaphragm thickness and diaphragm thickening capacity at tidal volume and force volume. Conclusions: Diaphragmatic activation had no functional correlation with the activation of lumbar multifidus muscles and TLF for both groups. Nevertheless, subjects with NS-LBP showed a reduced diaphragm thickness and a lower diaphragm thickening capacity at tidal volume and force volume, compared to healthy subjects.

Acute and chronic changes in diaphragmatic activity and respiratory function following C3 spinal hemi-contusion in mice

Acute and chronic changes in diaphragmatic activity and respiratory function following C3 spinal hemi-contusion in mice

Feasibility of transesophageal phrenic nerve stimulation

BackgroundEvery year, more than 2.5 million critically ill patients in the ICU are dependent on mechanical ventilation. The positive pressure in the lungs generated by the ventilator keeps the diaphragm passive, which can lead to a loss of myofibers within a short time. To prevent ventilator-induced diaphragmatic dysfunction (VIDD), phrenic nerve stimulation may be used.ObjectiveThe goal of this study is to show the feasibility of transesophageal phrenic nerve stimulation (TEPNS). We hypothesize that selective phrenic nerve stimulation can efficiently activate the diaphragm with reduced co-stimulations.MethodsAn in vitro study in saline solution combined with anatomical findings was performed to investigate relevant stimulation parameters such as inter-electrode spacing, range to target site, or omnidirectional vs. sectioned electrodes. Subsequently, dedicated esophageal electrodes were inserted into a pig and single stimulation pulses were delivered simultaneously with mechanical ventilation. Various stimulation sites and response parameters such as transdiaphragmatic pressure or airway flow were analyzed to establish an appropriate stimulation setting.ResultsPhrenic nerve stimulation with esophageal electrodes has been demonstrated. With a current amplitude of 40 mA, similar response figures of the diaphragm activation as compared to conventional stimulation with needle electrodes at 10mA were observed. Directed electrodes best aligned with the phrenic nerve resulted in up to 16.9 % higher amplitude at the target site in vitro and up to 6 cmH20 higher transdiaphragmatic pressure in vivo as compared to omnidirectional electrodes. The activation efficiency was more sensitive to the stimulation level inside the esophagus than to the inter-electrode spacing. Most effective and selective stimulation was achieved at the level of rib 1 using sectioned electrodes 40 mm apart.ConclusionDirected transesophageal phrenic nerve stimulation with single stimuli enabled diaphragm activation. In the future, this method might keep the diaphragm active during, and even support, artificial ventilation. Meanwhile, dedicated sectioned electrodes could be integrated into gastric feeding tubes.

Influence of mild pulmonary congestion on diaphragmatic mobility and activities of daily living in chronic kidney disease: An experimental and clinical study

BackgroundPulmonary congestion is a strong predictor of mortality and cardiovascular events in chronic kidney disease (CKD); however, the effects of the mild form on functionality have not yet been investigated. The objective of this study was to assess the influence of mild pulmonary congestion on diaphragmatic mobility (DM) and activities of daily living (ADL) in hemodialysis (HD) subjects, as well as compare ADL behavior on dialysis and non-dialysis days. In parallel, experimentally induce CKD in mice and analyze the resulting pulmonary and functional repercussions. MethodsThirty subjects in HD underwent thoracic and abdominal ultrasonography, anthropometric assessment, lung and kidney function, respiratory muscle strength assessment and symptoms analysis. To measure ADL a triaxial accelerometer was used over seven consecutive days. Twenty male mice were randomized in Control and CKD group. Thoracic ultrasonography, TNF-α analysis in kidney and lung tissue, exploratory behavior and functionality assessments were performed. ResultsMild pulmonary congestion caused a 26.1% decline in DM (R2=.261; P=.004) and 20% reduction in walking time (R2=.200; P=.01), indicating decreases of 2.23mm and 1.54min, respectively, for every unit increase in lung comet-tails. Regarding ADL, subjects exhibited statistically significant differences for standing (P=.002), walking (P=.034) and active time (P=.002), and number of steps taken (P=.01) on days with and without HD. In the experimental model, CKD resulted in increased levels of TNF-α on kidneys (P=.037) and lungs (P=.02), attenuation of exploratory behavior (P=.01) and significant decrease in traveled distance (P=.034). Thoracic ultrasonography of CKD mice showed presence of B-lines. ConclusionThe mild pulmonary congestion reduced DM and walking time in subjects undergoing HD. Individuals were less active on dialysis days. Furthermore, the experimental model implies that the presence of pulmonary congestion and inflammation may play a decisive role in the low physical and exploratory performance of CKD mice.

A Multichannel EMG System for Spatial Measurement of Diaphragm Activities

An important aspect of mechanical ventilation is the recognition and quantification of spontaneous respiratory effort. However, a measurement of flows and pressures often used for this purpose is prone to error. A promising alternative is to detect diaphragmatic contractions, directly. A method recently proposed is to acquire the diaphragm electromyography (EMG) signals using surface electrodes. However, this method is often limited by disturbances and electrode placements for some applications in which the patient is moving, such as rehabilitation or breathing training. In this work, we present a novel noninvasive method that addresses these problems. This method is based on a novel dry electrode belt, which can be used to comfortably derive EMG signals from the thorax, in combination with a developed electrical measurement system. The modular multichannel system is capable of simultaneously deriving and digitizing 32 differential EMG channels and sending them to a personal computer (PC). A specific digital signal processing chain allows combining the data into one robust overall signal. In addition, the signals derived from the thorax can be used to obtain information regarding the spatiotemporal propagation of the diaphragm EMG. To verify the functionality, the system is characterized. Subsequently, subject measurements are performed. From these, the spatiotemporal propagation of diaphragm EMG on the thorax can be identified. For better visualization, this propagation is graphically displayed in a 3-D model. In addition, it is shown how the combination of all signals can be used to obtain a robust overall signal that can be used to control ventilators.