Diaphragm Electromyogram Research Articles

Effects of Sports Bras and Breast Volume on Pulmonary System and Respiratory Symptom Responses to Exercise in Healthy Females.

This study assessed the individual and combined effects of sports bras and breast volume on pulmonary system and respiratory symptom responses to exercise in recreationally-active females. Twenty-three healthy females (18-27 y; bra sizes 32B-36DDD) were divided into small and large breast volume groups (SBV and LBV, respectively) around median volume (324 ml; mean ± SD SBV: 284 ± 38 ml vs. LBV: 560 ± 97 ml; p < 0.001, g = 3.84). Participants completed three 5-minute bouts of constant-load cycle exercise at 30, 60, and 90% of their peak power output while wearing a high-support sports bra, low-support sports bralette, or their own (self-selected) sports bra in randomized order. Measurements included ventilation, breathing pattern, respiratory pressures, diaphragm electromyogram (EMGdi), and ratings of perceived exertion (RPE), breathlessness (intensity and unpleasantness) and chest tightness due to bra. Compared to low-support and personal sports bras, the high-support sports bra evoked stronger sensations of restricted breathing and chest tightness ('slight' to 'moderate' restriction in n = 7 [30%] vs. n = 1 [4%] in low-support and personal bras; p = 0.014). There was, however, no evidence of greater concomitant inspiratory constraints, EMGdi, or inspiratory muscle pressure generation in either bra (all p > 0.05). Notably, LBV compared to SBV participants reported greater RPE (p = 0.037, ηp2 = 0.20), breathlessness intensity (p = 0.039, ηp2 = 0.20) and unpleasantness (p = 0.041; ηp2 = 0.19), which, in the setting of comparable pulmonary system responses to exercise, was likely driven by stronger perceived chest tightness and/or bra awareness in LBV participants. Despite evoking mild-to-moderately severe chest tightness due to bra during exercise - correctly fitted sports bras, whether low- or high-support, do not impose a physiological burden to the respiratory system and its response to mild-to-heavy intensity exercise in otherwise healthy females.

Role of the pontine respiratory group in the suppression of cough by codeine in cats

Codeine was microinjected into the area of the Kölliker-Fuse nucleus and the adjacent lateral parabrachial nucleus, within the pontine respiratory group in 8 anesthetized cats. Electromyograms (EMGs) of the diaphragm (DIA) and abdominal muscles (ABD), esophageal pressures (EP), and blood pressure were recorded and analyzed during mechanically induced tracheobronchial cough. Unilateral microinjections of 3.3 mM codeine (3 injections, each 37 ± 1.2 nl) had no significant effect on the cough number. However, the amplitudes of the cough ABD EMG, expiratory EP and, to a lesser extent, DIA EMG were significantly reduced. There were no significant changes in the temporal parameters of the cough. Control microinjections of artificial cerebrospinal fluid in 6 cats did not show a significant effect on cough data compared to those after codeine microinjections. Codeine-sensitive neurons in the rostral dorsolateral pons contribute to controlling cough motor output, likely through the central pattern generator of cough.

Diaphragmatic Myopathy Associated with Dual Immune Checkpoint Inhibitors in a Patient with Renal Cell Carcinoma

ABSTRACT Immune-related adverse events (irAEs) have become increasingly prevalent with immune checkpoint inhibitor (ICI) cancer treatment. We present a 79-year-old man with metastatic renal cell carcinoma who developed shortness of breath and hypercapnic respiratory insufficiency after his first cycle of nivolumab and ipilimumab. Laboratory data showed elevated creatinine kinase, troponins, and transaminases. Computed tomography of the chest demonstrated bilateral lower lobe atelectasis. Heart catheterization and endomyocardial biopsy were unremarkable. Electromyogram (EMG) and nerve conduction studies (NCS) of the limb muscles revealed mild diffuse myopathy, normal sensory nerve conductions, and low-amplitude motor responses. Subsequent diaphragmatic EMG and NCS demonstrated severe myopathy. ICI-mediated myopathy predominantly affecting diaphragmatic muscles was diagnosed. Treatment included intravenous methylprednisolone, infliximab, abatacept, rituximab, and plasmapheresis. He underwent tracheostomy placement on hospital day 11 due to minimal improvement. He was discharged to a long-term acute care hospital, but unfortunately, he died less than 1 month later due to recurrent infections. irAEs can affect any organ system, but diaphragmatic dysfunction is uncommon. Use of diaphragmatic EMG, NCS, ultrasound study, or biopsy can support the diagnosis. Treatment includes systemic steroids, plasmapheresis, immunosuppressive medications, respiratory support, and cessation of causative medications. ICI-related diaphragmatic dysfunction should be suspected in those patients at risk with hypoxia, hypercapnia, or prolonged invasive or noninvasive ventilation without a distinct etiology. This case report exemplifies the importance of multidisciplinary workup and management of respiratory symptoms and insufficiency to identify and ameliorate irAEs. Diaphragmatic involvement can be associated with significant morbidity and mortality despite early aggressive multimodal therapy.

Ampakines increase diaphragm activation following mid-cervical contusion injury in rats

Ampakines are positive allosteric modulators of AMPA receptors. We hypothesized that low-dose ampakine treatment increases diaphragm electromyogram (EMG) activity after mid-cervical contusion injury in rats. Adult male and female Sprague Dawley rats were implanted with in-dwelling bilateral diaphragm EMG electrodes. Rats received a 150 kDyn C4 unilateral contusion (C4Ct). At 4- and 14-days following C4Ct, rats were given an intravenous bolus of ampakine CX717 (5 mg/kg, n = 10) or vehicle (2-hydroxypropyl-beta-cyclodextrin; HPCD; n = 10). Diaphragm EMG was recorded while breathing was assessed using whole-body plethysmography. At 4-days, ampakine administration caused an immediate and sustained increase in bilateral peak inspiratory diaphragm EMG bursting and ventilation. The vehicle had no impact on EMG bursting. CX717 treated rats were able to increase EMG activity during a respiratory challenge to a greater extent vs. vehicle treated. Rats showed a considerable degree of spontaneous recovery of EMG bursting by 14 days, and the impact of CX717 delivery was blunted as compared to 4-days. Direct recordings from the phrenic nerve at 21–24 days following C4Ct confirmed that ampakines stimulated bilateral phrenic neural output in injured rats. We conclude that low-dose intravenous treatment with a low-impact ampakine can enhance diaphragm activation shortly following mid-cervical contusion injury, when deficits in diaphragm activation are prominent.

Trans-spinal magnetic stimulation induces co-activation of the diaphragm and biceps in healthy subjects.

The present study was designed to examine the effect of trans-spinal magnetic stimulation on bilateral respiratory and forelimb muscles in healthy subjects. Two wings of a figure-of-eight magnetic coil were placed on the dorsal vertebrae, from the fifth cervical to the second thoracic dorsal vertebra with a center at the seventh cervical vertebra. The surface electromyograms of bilateral diaphragm and biceps were recorded in response to trans-spinal magnetic stimulation with 20%-100% maximum output of the stimulatory device in male (n = 12) and female participants (n = 8). Trans-spinal magnetic stimulation can induce a co-activation of bilateral diaphragm and biceps when the stimulation intensity is above 60%. The onset latency was comparable between the left and right sides of the muscles, suggesting bilateral muscles could be simultaneously activated by trans-spinal magnetic stimulation. In addition, the intensity-response curve of the biceps was shifted upward compared with that of the diaphragm in males, indicating that the responsiveness of the biceps was greater than that of the diaphragm. This study demonstrated the feasibility of utilizing trans-spinal magnetic stimulation to co-activate the bilateral diaphragm and biceps. We proposed that this stimulatory configuration can be an efficient approach to activate both respiratory and forelimb muscles.

Exercise‐induced bronchoconstriction assessed by a ratio of surface diaphragm EMG to tidal volume

AbstractExercise‐induced bronchoconstriction (EIB) is usually assessed by changes in forced expiratory volume in 1 s (FEV1) which is effort dependent. The purpose of this study was to determine whether the diaphragm electromyogram (EMGdi) recorded from chest wall surface electrodes could be used to reflect changes in airway resistance during an exercise challenge test and to distinguish patients with EIB from those without EIB. Ninety participants with or without asthma history were included in the study. FEV1 was recorded before and 5, 10, 15, and 20 min after exercise. EIB was defined as an FEV1 decline greater than 10% after exercise. A ratio of root mean square of EMGdi to tidal volume (EMGdi/VT) was used to assess changes in airway resistance. Based on changes in FEV1, 25 of 90 participants exhibited EIB; the remainder were defined as non‐EIB participants. EMGdi/VT in EIB increased by 124% (19%–478%) which was significantly higher than that of 21% (−39% to 134%) in non‐EIB participants (p &lt; 0.001). At the optimal cutoff point (54% in EMGdi/VT), the area under the ROC curve (AUC) for detection of a positive test was 0.92 (p &lt; 0.001) with sensitivity 92% and specificity 88%. EMGdi/VT can be used to assess changes in airway resistance after exercise and could be used to distinguish participants with EIB from those without EIB.

Central sleep apnea treated by a constant low-dose CO2 supplied by a novel device.

CO2 inhalation has been previously reported as a treatment for central sleep apnea both when associated with heart failure or where the cause is unknown. Here, we evaluated a novel CO2 supply system using a novel open mask capable of comfortably delivering a constantly inspired fraction of CO2 ([Formula: see text]) during sleep. We recruited 18 patients with central sleep apnea (13 patients with cardiac disease, and 5 patients idiopathic) diagnosed by diaphragm electromyogram (EMG) recordings made during overnight full polysomnography (PSG) (night 1). In each case, the optimal [Formula: see text] was determined by an overnight manual titration with PSG (night 2). Titration commenced at 1% CO2 and increased by 0.2% increments until central sleep apnea (CSA) disappeared. Patients were then treated on the third night (night 3) with the lowest therapeutically effective concentration of CO2 derived from night 2. Comparing night 1 and night 3, both apnea-hypopnea index (AHI; 31 ± 14 vs. 6 ± 3 events/h, P < 0.01) and arousal index (22 ± 8 vs. 15 ± 8 events/h, P < 0.01) were significantly improved during CO2 treatment. Sleep efficiency improved from 71 ± 18 to 80 ± 11%, P < 0.05, and sleep latency was shorter (23 ± 18 vs. 10 ± 10 min, P < 0.01). Heart rate was not different between night 1 and night 3. Our data confirm the feasibility of our CO2 delivery system and indicate that individually titrated CO2 supplementation with a novel device including a special open mask can reduce sleep disordered breathing severity and improve sleep quality. Randomized controlled studies should now be undertaken to assess therapeutic benefit for patients with CSA.NEW & NOTEWORTHY A novel device using a special mask was developed and proved that CO2 therapy using the device could eliminate central sleep apnea (CSA) events and improve sleep quality including reducing arousal index in patients with heart failure. The device would become a useful clinical treatment for heart failure patients with CSA.

Differential inhibition of cough by GABAA and GABAB receptor antagonists in the nucleus of the solitary tract in cats

Bicuculline and saclofen were microinjected into the rostral (rNTS) and caudal nucleus of the solitary tract (cNTS) in 17 anesthetized cats. Electromyograms (EMGs) of the diaphragm (DIA) and abdominal muscles (ABD), esophageal pressures (EP), and blood pressure were recorded and analyzed. Bilateral microinjections of 1 mM bicuculline in the rNTS significantly reduced the number of coughs (CN), amplitudes of DIA and ABD EMG, inspiratory and expiratory EP, and prolonged the duration of the cough expiratory phase (CTE) as well as the total cough cycle duration (CTtot). Bilateral microinjections of 2 mM saclofen reduced only cough expiratory efforts. Bilateral microinjection of bicuculline in the cNTS significantly reduced CN and amplitudes of ABD EMG and elongated CTE and CTtot. Bilateral microinjections of saclofen in cNTS had no significant effect on analyzed cough parameters. Our results confirm a different GABAergic inhibitory system in the rNTS and cNTS acting on mechanically induced cough in cats.

Novel automated “score mapping” of diaphragmatic compound motor action potential for the early detection of phrenic nerve injury during cryoablation

The proximity of phrenic nerve to right sided pulmonary veins (PV) make it susceptible to injury during cryoballoon ablation (CBA) for atrial fibrillation (AF). Monitoring of diaphragmatic compound motor action potentials (CMAP) obtained from lead aVF or modified surface ECG leads placed along the diaphragm have been used for early detection of phrenic nerve injury (PNI). 1 Schaerli N. Badertscher P. Spies F. et al. A Simplified Method to Detect Phrenic Nerve Injury During Cryoballoon Ablation of Atrial Fibrillation Using Lead aVF of the Surface ECG. Circ Arrhythm Electrophysiol. 2021 Aug; 14e009986https://doi.org/10.1161/CIRCEP.121.009986 Crossref Scopus (0) Google Scholar Thirty percent drop in CMAP amplitude has been shown in studies as the threshold for prevention of PNI. 2 Miyazaki S. Hachiya H. Taniguchi H. et al. Prospective Evaluation of Bilateral Diaphragmatic Electromyograms During Cryoballoon Ablation of Atrial Fibrillation. JCE. 2015; 26: 622-628 Google Scholar However, CMAP signals may be susceptible to respiratory variations, catheter movement, inadequate baseline amplitude making it difficult to monitor the change in CMAP. 3 Sharma P.S. Padala S.K. Thompson J.J. Gunda S. Koneru J.N. Ellenbogen K.A. Factors Influencing Diaphragmatic Compound Motor Action Potentials During Cryoballoon Ablation for Atrial Fibrillation. JCE. 2016; 7: 1384-1389 Google Scholar Score-map of the CMAP using template matching with 3D electroanatomic mapping system can be used to automate the monitoring of CMAP. The aims of this study were to assess the relationship of change in CMAP amplitude with change in score-map and then use the automated score-map prospectively for early detection of PNI during CBA.

Co-activation of diaphragm and bicep in response to trans-spinal magnetic stimulation in healthy males

Magnetic stimulation is a non-invasive approach to activate the neural tissue and induce the motor evoked potential. Diaphragm and bicep are innervating by motoneurons located within the mid-cervical spine cord; thus, the present study was designed to evaluate whether trans-spinal magnetic stimulation can co-activate the diaphragm and bicep in healthy male subjects (n=12) (KMUHIRB-F(I)-20210039). The two wings of the figure-of-eight magnetic coil (MCF-B65, inner diameter: 35 mm; out diameter: 75 mm) were placed on the dorsal vertebrae from the fifth cervical to the second thoracic vertebral column and its handle was vertical to the spine. The surface electromyogram of the bilateral diaphragm and bicep was recorded in response to trans-spinal magnetic stimulation with 20-100% maximum output of the stimulatory device. The results showed that trans-spinal magnetic stimulation can co-activate both muscles when the stimulatory intensity reached 60%. Notably, the intensity-response curve of motor evoked potential was significantly different between diaphragm and bicep. Specifically, the normalized response curve of the bicep was generally greater than that of the diaphragm, suggesting the excitability and responsiveness of bicep were greater than that of the diaphragm during trans-spinal magnetic stimulation. In addition, the motor evoked potential of the right diaphragm and bicep was greater than the left side during low stimulatory intensity, indicating there are anatomical and/or physiological differences between left and right muscles. In conclusion, trans-spinal magnetic stimulation with two coil wings along the vertebrae can co-activate the diaphragm and bicep. This trans-spinal magnetic stimulatory configuration can be considered as a feasible and efficient neuro-rehabilitative strategy to activate muscles innervating by the cervical spinal cord in subjects with impaired respiratory and forelimb motor function. The Ministry of Science and Technology (MOST 110-2636-B-110-001 &amp; 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.

RESPIRATORY MECHANICS AND NEURAL RESPIRATORY DRIVE OF UNTREATED GASPING DURING CARDIAC ARREST IN A PORCINE MODEL.

Introduction: Although the effects on hemodynamics of gasping during cardiac arrest (CA) have received a lot of attention, less is known about the respiratory mechanics and physiology of respiration in gasping. This study aimed to investigate the respiratory mechanics and neural respiratory drive of gasping during CA in a porcine model. Method: Pigs weighing 34.9 ± 5.7 kg were anesthetized intravenously. Ventricular fibrillation (VF) was electrically induced and untreated for 10 min. Mechanical ventilation (MV) was ceased immediately after the onset of VF. Hemodynamic and respiratory parameters, pressure signals, diaphragmatic electromyogram data, and blood gas analysis data were recorded. Results: Gasping was observed in all the animals at a significantly lower rate (2-5 gaps/min), with higher tidal volume ( VT ; 0.62 ± 0.19 L, P < 0.01), and with lower expired minute volume (2.51 ± 1.49 L/min, P < 0.001) in comparison with the baseline. The total respiratory cycle time and the expiratory time tended to be lengthened. Statistically significant elevations in transdiaphragmatic pressure, the pressure-time product of diaphragmatic pressure, and the mean of root mean square diaphragmatic electromyogram values (RMSmean) were observed ( P < 0.05, P < 0.05, and P < 0.001, respectively); however, VT /RMSmean and transdiaphragmatic pressure/RMSmean were reduced at all time points. The partial pressure of oxygen showed a continuous decline after VF to reach statistical significance in the 10th minute (9.46 ± 0.96 kPa, P < 0.001), whereas the partial pressure of carbon dioxide tended to first rise and then fall. Conclusions: Gasping during CA was characterized by high VT , extremely low frequency, and prolonged expiratory time, which may improve hypercapnia. During gasping, increased work of breathing and insufficient neuromechanical efficacy of neural respiratory drive suggested the necessity of MV and appropriate management strategies for MV during resuscitation after CA.

Dynamic evaluation of the pulmonary protective effects of prone position ventilation via respiratory mechanics for patients with moderate to severe acute respiratory distress syndrome.

BackgroundPatients with moderate to severe acute respiratory distress syndrome (ARDS) have been recommended to receive prone position ventilation (PPV). However, the dynamic changes in respiratory mechanics during PPV and their relationship with the prognosis have not been sufficiently evaluated. In addition, the impact of using neuromuscular blocking agents (NMBAs) during PPV on respiratory mechanics is not clear enough. Thus, the study aims to investigate the above-mentioned issues.MethodsA prospective cohort study was conducted on 22 patients with moderate to severe ARDS who received PPV in the intensive care unit (ICU) of the First Affiliated Hospital of Guangzhou Medical University. A multifunctional gastric tube was used to measure the patients’ respiratory mechanics during supine position ventilation (SPV), early PPV (PPV within 4 h of initiation), and middle/late PPV (more than 6 h after the initiation of PPV). Longitudinal data were analyzed with generalized estimating equations (GEE).ResultsCompared with SPV, the esophageal pressure swings (ΔPes) measured during the PPV was significantly higher (SPV 7.46 vs. early PPV 8.00 vs. middle/late PPV 8.30 cmH2O respectively; PSPV vs. middle/late PPV =0.025<0.05). A stratified analysis by patients’ outcome showed that the peak airway pressure (Ppeak), ΔPes and respiration rate (RR) in the death group were significantly higher than survival group. On the contrary, the tidal volume (Vt), diaphragmatic electromyogram (EMGdi) and PaO2/FiO2 ratio (PFR) in the death group were significantly lower than survival group. Notably, the ΔPes and transpulmonary driving pressure (DPL) were significantly lower in the patients treated with NMBAs (7.08 vs. 8.76 cmH2O ΔPes; P<0.01), (14.82 vs. 18.08 cmH2O DPL; P<0.001).ConclusionsDuring the transition from SPV to early PPV and then to middle/late PPV, the ΔPes in the PPV were greater than SPV and it fluctuated within a normal range while oxygenation improved significantly in all patients. The Ppeak, ΔPes and RR in the death group were significantly higher than survival group. When NMBAs were used, the ΔPes, inspiratory transpulmonary pressure (PLei), driving pressure (DP) and DPL were significantly decreased, suggesting that the rational combination of NMBAs and PPV may exert a synergistic protective effect on the lungs.

Laryngeal and swallow dysregulation following acute cervical spinal cord injury.

Laryngeal function is vital to airway protection. Although swallow is mediated by the brainstem, the mechanism underlying the increased risk of dysphagia after cervical spinal cord injury (SCI) is unknown. We hypothesized that: 1) loss of descending phrenic drive affects swallow and breathing differently, and 2) loss of ascending spinal afferent information alters swallow regulation. We recorded electromyograms (EMGs) from upper airway and chest wall muscles in freely breathing pentobarbital-anesthetized cats and rats. Laryngeal abductor activity during inspiration increased about twofold following C2 lateral hemisection. Ipsilateral to the injury, the crural diaphragm EMG amplitude was reduced during breathing (62 ± 25% change postinjury), but no animal had complete termination of activity; 75% of animals had increased contralateral diaphragm recruitment, but this did not reach significance. During swallow, laryngeal adductor and pharyngeal constrictor muscles increased activity, and diaphragm activity was bilaterally suppressed. This was unexpected because of the ipsilateral-specific response during breathing. Swallow-breathing coordination was disrupted by injury, and more swallows occurred during early expiration. Finally, to determine if the chest wall is a major source of feedback for laryngeal regulation, we performed T1 total transections in rats. As in the C2 lateral hemisection, inspiratory laryngeal recruitment was the first feature noted after injury. In contrast to the C2 lateral hemisection, diaphragmatic drive increased after T1 transection. Overall, we found that SCI alters laryngeal drive during swallow and breathing, and alters swallow-related diaphragm activity. Our results show behavior-specific effects, suggesting that swallow is affected more than breathing is by SCI, and emphasizing the need for additional studies on the effect of ascending afferents from the spinal cord on laryngeal function.NEW & NOTEWORTHY This is the first manuscript to determine the impact of cSCI on laryngeal and swallow function, and to describe a possible mechanism for dysphagia and altered airway protection after injury.

Diaphragm EMG activity during hyperbaric oxygen exposure in spinal injured rats

Cervical spinal cord injury can cause significant respiratory dysfunction and in severe cases necessitates mechanical ventilation. Accumulating evidence indicates that hyperbaric oxygen (HBO) therapy, initiated shortly after spinal cord injury (SCI), can mitigate spinal cord pathology. Further, a recent study from our group demonstrated that HBO therapy can attenuate diaphragm atrophy after SCI. The primary purpose of the present investigation was to evaluate diaphragm electromyogram (EMG) activity during HBO therapy in rats with cervical SCI. HBO therapy has not been widely adopted after SCI, and if HBO is to be translated to human use, we reasoned that it is important to determine how breathing is impacted during HBO exposure. Adult female Sprague‐Dawley rats were implanted with chronic indwelling EMG electrodes in the mid‐costal diaphragm two weeks prior to SCI. Following hemicontusion injury of the C4 spinal cord, one experimental group was treated with HBO (n=3), and another group was left untreated (n=3). The HBO treatment consisted of a one hour exposure to 100% O2 at 3 atmospheres (ATA). In all experiments, diaphragm EMG activity was recorded in freely moving rats, without anesthesia. Recordings were made for 10 minutes prior to treatment, throughout the HBO exposure, and for 10 minutes after. Diaphragm EMG recordings in the normobaric normoxia control group conditions were completed for the same duration of time as the treated group. Daily HBO treatment and EMG recordings were done until 10‐days post‐SCI. Peak diaphragm EMG burst amplitude was quantified before SCI, over the 10 days of treatment, and at 1 and 2 weeks post‐treatment. Prior to SCI, body weight was similar between groups (control: 227±4 g; HBO: 228±3 g). All rats with tolerated HBO treatment with no evidence of adverse events or impact on weight gain over the 10 day period (10 day body weight: control: 198 ± 14 g; HBO: 197 ± 13 g). The acute HBO exposure caused an increase in the area under the curve of the rectified and integrated inspiratory burst amplitude of the diaphragm recording made ipsilateral to the lesion. This increase averaged 126 ± 18% of baseline across the 10 HBO treatments. The ipsilateral EMG burst amplitude also remained elevated at 10 min post‐HBO exposure (115 ± 32%) compared to pre HBO exposure. At the conclusion of the 10 day treatment paradigm, ipsilateral diaphragm EMG output during quiet breathing was elevated in HBO (156 ± 50% of post‐injury baseline) as compared to the control group (111 ± 6% of baseline). However the ipsilateral diaphragm EMG burst amplitude of the two groups were similar when evaluated 2 weeks after the daily HBO sessions concluded. This ongoing study indicates that acute exposure to HBO therapy is associated with an increase in diaphragm EMG activity, and 10 days of HBO therapy accelerates the recovery of diaphragm activation following cervical contusion injury.

Accessory Muscle Support of Breathing in Young Dystrophin‐deficient mdx Mice

Duchenne muscular dystrophy (DMD) is a genetic neuromuscular disorder that occurs due to the absence of the structural protein dystrophin and secondary consequences. DMD is characterized by severe and progressive skeletal muscle weakness, which extends to the respiratory muscles. In young dystrophin‐deficient mdx mice, peak inspiratory pressure‐generating capacity is preserved despite diaphragm muscle weakness and reduced electromyogram (EMG) activitya. Our overarching hypothesis is that accessory muscle compensation limits ventilatory deficit in early dystrophic disease. Four‐month‐old male wild‐type (n=39) and mdx (n=41) mice were studied. Breathing was assessed in conscious mice using whole body plethysmography during normoxia and chemochallenge (10% O2/6% CO2). Thoracic oesophageal pressure and obligatory (diaphragm and external intercostal) respiratory muscle EMG activities were recorded in urethane (1.7g/kg i.p.) anaesthetised spontaneously breathing mice during baseline and sustained tracheal occlusion (maximal muscle activation). Diaphragm and scalene (accessory respiratory muscle) force output were examined ex vivo. Data were statistically compared using unpaired Student’s t test or two‐way ANOVA with Bonferroni post hoc test. Peak diaphragm force ex vivo (P &lt; 0.0001) and baseline diaphragm EMG activity (P = 0.01) were significantly lower in mdx compared with wild‐type. Minute ventilation was equivalent in age‐matched wild‐type and mdx mice during baseline and chemochallenge (P = 0.1). Peak diaphragm (P &lt; 0.0001) and external intercostal (P = 0.01) EMG activities during obstruction were significantly lower in mdx mice compared to wild‐type, while peak inspiratory pressure was equivalent (P = 0.4). Interestingly, peak scalene muscle force ex vivo was preserved in 4‐month‐old mdx mice (P = 0.8). Despite a decline in diaphragm muscle performance (decreased EMG activity and mechanical weakness) at baseline, ventilatory capacity is preserved in mdx mice. Furthermore, despite lower peak electrical activation of the obligatory muscles of breathing and diaphragm muscle functional deficit, peak inspiratory pressure is preserved in 4‐month‐old mdx mice, confirming our previous findings in 2‐month‐old micea. Our finding of preserved scalene muscle force suggests that compensation may be provided by accessory muscles to support ventilatory and non‐ventilatory behaviours in early dystrophic disease. Current studies are examining the EMG activity of accessory respiratory muscles (e.g. scalene, sternomastoid, cleidomastoid and trapezius) in early and advanced dystrophic disease in mdx mice.References a Burns DP, Murphy KH, Lucking EF, O'Halloran KD. Inspiratory pressure‐generating capacity is preserved during ventilatory and non‐ventilatory behaviours in young dystrophic mdx mice despite profound diaphragm muscle weakness. J. Physiol. 2019;597(3):831‐848.

Rostral-Caudal Effect of Cervical Magnetic Stimulation on the Diaphragm Motor Evoked Potential after Cervical Spinal Cord Contusion in the Rat.

The present study was designed to investigate the rostral-caudal effect of spinal magnetic stimulation on diaphragmatic motor-evoked potentials after cervical spinal cord injury. The diaphragm electromyogram was recorded in rats that received a laminectomy or a left midcervical contusion at the acute (1 day), subchronic (2 weeks), or chronic (8 weeks) injury stages. The center of a figure-eight coil was placed at 30 mm lateral to bregma on the left side, and the effect of magnetic stimulation was evaluated by stimulating the rostral, middle, and caudal cervical regions in spontaneously breathing rats. The results demonstrated that cervical magnetic stimulation induced intensity-dependent motor-evoked potentials in the bilateral diaphragm in both uninjured and contused rats; however, the left diaphragm exhibited a higher amplitude and earlier onset than the right diaphragm. Moreover, the intensity-response curve was shifted upward in the rostral-to-caudal direction of magnetic stimulation, suggesting that caudal cervical magnetic stimulation produced more robust diaphragmatic motor-evoked potentials compared with rostral cervical magnetic stimulation. Interestingly, the diaphragmatic motor-evoked potentials were similar between uninjured and contused rats during cervical magnetic stimulation despite weaker inspiratory diaphragmatic activity in contused rats. In addition, in contused animals but not uninjured animals, diaphragmatic motor-evoked potential amplitudes were greater at the chronic stage than during earlier injury stages. These results demonstrated that cervical magnetic stimulation can excite the residual phrenic motor circuit to activate the diaphragm in the presence of a significant lesion in the cervical spinal cord. These findings indicate that this non-invasive approach is effective for modulating diaphragmatic excitability after cervical spinal cord injury.

Temporary Diaphragm Pacing for Patients at Risk of Prolonged Mechanical Ventilation After Extensive Open Aortic Surgery

Respiratory failure after extensive aortic surgery (EAS), such as thoracoabdominal aortic aneurysm (TAAA) repair, is the most prevalent complication. It starts with the initiation of mechanical ventilation (MV), which results in diaphragm atrophy and contractile dysfunction, termed ventilator-dependent diaphragmatic dysfunction (VIDD), with attendant increases in morbidity and mortality. VIDD has been reported in ≤53% of patients after 24 hours of MV. Diaphragm pacing (DP) has been used for patients with VIDD, such as quadriplegia and diaphragm paralysis. We evaluated the feasibility of DP for patients with a high risk of prolonged MV after EAS. A retrospective review of prospectively collected data was conducted of patients who had undergone implantation of a Food and Drug Administration–approved DP system after EAS from June 2020 to March 2021. The DP electrodes were placed in the left diaphragm after diaphragm closure after TAAA repair or bilaterally after transperitoneal exposure. DP was instituted on arrival to the intensive care unit to prevent diaphragm atrophy and VIDD. The diaphragm electromyogram was analyzed before DP and daily. The key clinical outcome variables were recorded. Seven patients (four men; mean age, 70.1 years) had undergone DP implantation after TAAA repair (n = 6) or transperitoneal renal/visceral debranching (n = 1). The risk factors for respiratory failure and outcomes are listed in the Table. Pulmonary function could not be assessed in three patients owing to emergency nature of the operation. No patient died intraoperatively. No DP-related complications occurred. In all patients, significant improvement in the diaphragm electromyogram was noted with DP (Fig). The median total MV time, including operating time, was 32 hours (range, 16-73 hours). The median postoperative MV time was 22.1 hours (range, 8-63 hours). One patient had required reintubation because of pulmonary edema 29 hours after initial extubation, requiring 44 hours of additional MV. No patient had required prolonged MV (>3 days) or developed VIDD. The median intensive care unit length of stay was 5 days. DP was used for 2 to 6 days (median, 3.8 days). DP increased diaphragm muscular contractions and might mitigate prolonged MV and the development of VIDD after EAS. A further comparative study is warranted.TableRisk factors and outcomesPt. No.Age; sexRisk factorProcedureMV duration, hoursICU, daysFEV1, %EMG: right; leftPostoperativeTotalBaselineFollow-up160; MFormer smokerTAAA repair17.530.54NANA; weakNA; good276; MFormer smoker; sleep studies with poor oxygen saturationRuptured TAAA repair12206NANA; weakNA; good381; MFormer smoker; COPDMycotic TAAA repair16.525.52NANA; weakNA; good475; FFormer smoker; COPDRuptured TAAA repair816101.68NA; weakNA; good561; FActive smoker; COPDTAAA repair243651.55NA; nearly absentNA; good666; MActive smoker; COPDRVD19 + 4423 + 4462.38Nearly absent; nearly absentGood; good779; FFormer smokerTAAA repair637351.29NA; absentNA; weakCOPD, Chronic obstructive pulmonary disease; EMG, electromyogram; F, female; FEV1, forced expiratory volume in 1 second; ICU, intensive care unit; M, male; MV, mechanical ventilation; NA, not applicable; Pt. No., patient number; RVD, renal/visceral debranching; TAAA, thoracoabdominal aortic aneurysm. Open table in a new tab

Comparison of home ambulatory type 2 polysomnography with a portable monitoring device and in-laboratory type 1 polysomnography for the diagnosis of obstructive sleep apnea in children.

To compare type 2 polysomnography (T2PSG) to the gold standard type 1 in-laboratory polysomnography (T1PSG) for diagnosing obstructive sleep apnea (OSA) in children; validate home T2PSG in children with suspected OSA. Eighty-one participants (ages 6-18) with suspected OSA had simultaneous T1PSG and T2PSG in the sleep laboratory, 47 participants (ages 5-16) had T1PSG in the sleep laboratory and T2PSG performed at home. Sleep scientists staged and scored polysomnography data, and pediatric sleep physicians assigned a diagnosis of normal or OSA. Participant demographics, polysomnography variables, and diagnoses were compared using chi-square and Fisher's exact tests for nominal variables, t test for continuous variables and Cohen's kappa to assess concordance. Acceptable recordings were obtained for every home T2PSG. When T1PSG and T2PSG were simultaneous, correlation between the number of arousals, respiratory disturbance index, and sleep stages was excellent. T2PSG at home demonstrated less stage 2 sleep, more rapid eye movement sleep, and higher sleep efficiency. Comparison of home T2PSG to T1PSG for diagnosing OSA showed a false-positive rate of 6.6% and false-negative rate of 3% for those performed at home. T2PSG in the home is feasible with excellent concordance with T1PSG for the purposes of diagnosing OSA in children aged 5-18 years. Home T2PSG may be more representative of a "normal" night for children and could benefit those suspected of having OSA by reducing waiting times for laboratory PSG, improving access to PSG and possibly reducing costs of investigating and treating OSA. Withers A, Maul J, Rosenheim E, O'Donnell A, Wilson A, Stick S. Comparison of home ambulatory type 2 polysomnography with a portable monitoring device and in-laboratory type 1 polysomnography for the diagnosis of obstructive sleep apnea in children. J Clin Sleep Med. 2022;18(2):393-402.

Differential effects of acute cerebellectomy on cough in spontaneously breathing cats.

The role of the cerebellum in controlling the cough motor pattern is not well understood. We hypothesized that cerebellectomy would disinhibit motor drive to respiratory muscles during cough. Cough was induced by mechanical stimulation of the tracheobronchial airways in anesthetized, spontaneously breathing adult cats (8 male, 1 female), and electromyograms (EMGs) were recorded from upper airway, chest wall, and abdominal respiratory muscles. Cough trials were performed before and at two time points after total cerebellectomy (10 minutes and >1 hour). Unlike a prior report in paralyzed, decerebrated, and artificially ventilated animals, we observed that cerebellectomy had no effect on cough frequency. After cerebellectomy, thoracic inspiratory muscle EMG magnitudes increased during cough (diaphragm EMG increased by 14% at 10 minutes, p = 0.04; parasternal by 34% at 10 minutes and by 32% at >1 hour, p = 0.001 and 0.03 respectively). During cough at 10 minutes after cerebellectomy, inspiratory esophageal pressure was increased by 44% (p = 0.004), thyroarytenoid (laryngeal adductor) muscle EMG amplitude increased 13% (p = 0.04), and no change was observed in the posterior cricoarytenoid (laryngeal abductor) EMG. Cough phase durations did not change. Blood pressure and heart rate were reduced after cerebellectomy, and respiratory rate also decreased due to an increase in duration of the expiratory phase of breathing. Changes in cough-related EMG magnitudes of respiratory muscles suggest that the cerebellum exerts inhibitory control of cough motor drive, but not cough number or phase timing in response to mechanical stimuli in this model early after cerebellectomy. However, results varied widely at >1 hour after cerebellectomy, with some animals exhibiting enhancement or suppression of one or more components of the cough motor behavior. These results suggest that, while the cerebellum and behavior-related sensory feedback regulate cough, it may be difficult to predict the nature of the modulation based on total cerebellectomy.

Estimated ECG Subtraction method for removing ECG artifacts in esophageal recordings of diaphragm EMG

The accuracy of diaphragm electromyogram (EMGdi) derived parameters, as used in critically ill intensive care unit (ICU) patients, can be compromised due to electrocardiographic (ECG) interference in the EMGdi signal. Removal of ECG contamination from the esophageal recordings of the EMGdi is challenging due to spectral overlapping of EMG and ECG signals and because of variability in ECG shape and amplitude. Therefore, we designed an Estimated ECG Subtraction (EES) method, based on three steps: (1) identification of the timing of the ECG artifact without an ECG reference channel, (2) estimation of the normalized ECG, considering the EMGdi as noise, and (3) subtraction of the denormalized ECG estimate from the EMGdi recordings. We evaluated the EES method against the use of a single wavelet-based adaptive filter. Using EMGdi signals of ten ICU patients and simulated contaminated EMG, we demonstrated that the EES method yields uncontaminated EMGdi, and showed that it is more effective than a wavelet-based adaptive filter only. Implementation of this technique may offer means to improve diaphragm activity monitoring and control in clinical practice.