Intercostal nerve electrodiagnostic testing in rib fractures.

INTRODUCTION/AIMS: Intercostal nerve injury can occur after rib fractures, resulting in denervation of the abdominal musculature. Loss of innervation to the rectus abdominis and intercostal muscles can cause pain, atrophy, and eventual eventration, which may be an underrecognized and thus undertreated complication of rib fractures. We investigated the clinical utility of intercostal nerve electrodiagnostic testing following rib fractures to diagnose and localize nerve injury at levels T7 and below. METHODS: Five patients with displaced bicortical rib fractures involving the 7th-11th ribs and clinical eventration of the ipsilateral abdominal wall underwent intercostal nerve conduction studies (NCS) and needle electromyography (EMG) on the affected side. EMG of the rectus abdominis and intercostal muscles was performed with ultrasound guidance, and ultrasound measurements of rectus abdominis thickness were obtained to assess for atrophy. RESULTS: Average patient age was 59.4 years and average body mass index (BMI) was 31.5 kg/m2. Intercostal NCS and EMG were able to reliably diagnose and localize intercostal nerve damage after rib fractures. Ultrasound demonstrated an average rectus abdominis transverse cross-sectional thickness of 0.534 cm on the affected side, compared with 1.024 cm on the non-affected side. DISCUSSION: Intercostal electrodiagnostic studies can diagnose and localize intercostal nerve damage after displaced rib fractures. Musculoskeletal ultrasound can be used to diagnose and quantify rectus abdominis atrophy and to accurately and safely guide needle EMG to the intercostal and rectus abdominis muscles.

Ability of parasternal intercostal muscle thickening fraction to predict reintubation in surgical patients with sepsis.

OBJECTIVES: We aimed to evaluate the ability of the parasternal intercostal (PIC) thickening fraction during spontaneous breathing trial (SBT) to predict the need for reintubation within 48 h after extubation in surgical patients with sepsis. METHODS: This prospective observational study included adult patients with sepsis who were mechanically ventilated and indicated for SBT. Ultrasound measurements of the PIC thickening fraction and diaphragmatic excursion (DE) were recorded 15 min after the start of the SBT. After extubation, the patients were followed up for 48 h for the need for reintubation. The study outcomes were the ability of the PIC thickening fraction (primary outcome) and DE to predict reintubation within 48 h of extubation using area under receiver characteristic curve (AUC) analysis. The accuracy of the model including the findings of right PIC thickening fraction and right DE was also assessed using the current study cut-off values. Multivariate analysis was performed to identify independent risk factors for reintubation. RESULTS: We analyzed data from 49 patients who underwent successful SBT, and 10/49 (20%) required reintubation. The AUCs (95% confidence interval [CI]) for the ability of right and left side PIC thickening fraction to predict reintubation were 0.97 (0.88-1.00) and 0.96 (0.86-1.00), respectively; at a cutoff value of 6.5-8.3%, the PIC thickening fraction had a negative predictive value of 100%. The AUCs for the PIC thickening fraction and DE were comparable; and both measures were independent risk factors for reintubation. The AUC (95% CI) of the model including the right PIC thickening fraction > 6.5% and right DE ≤ 18 mm to predict reintubation was 0.99 (0.92-1.00), with a positive predictive value of 100% when both sonographic findings are positive and negative predictive value of 100% when both sonographic findings are negative. CONCLUSIONS: Among surgical patients with sepsis, PIC thickening fraction evaluated during the SBT is an independent risk factor for reintubation. The PIC thickening fraction has an excellent predictive value for reintubation. A PIC thickening fraction of ≤ 6.5-8.3% can exclude reintubation, with a negative predictive value of 100%. Furthermore, a combination of high PIC and low DE can also indicate a high risk of reintubation. However, larger studies that include different populations are required to replicate our findings and validate the cutoff values.

Ultrasound-guided parasternal intercostal nerve block for postoperative analgesia in mediastinal mass resection by median sternotomy: a randomized, double-blind, placebo-controlled trial.

BACKGROUND: Ultrasound-guided parasternal intercostal nerve block is rarely used for postoperative analgesia, and its value remains unclear. This study aimed to evaluate the effectiveness of ultrasound-guided parasternal intercostal nerve block for postoperative analgesia in patients undergoing median sternotomy for mediastinal mass resection. METHODS: This randomized, double-blind, placebo-controlled trial performed in Renmin Hospital, Wuhan University, enrolled 41 participants aged 18-65 years. The patients scheduled for mediastinal mass resection by median sternotomy were randomly assigned were randomized into 2 groups, and preoperatively administered 2 injections of ropivacaine (PSI) and saline (control) groups, respectively, in the 3rd and 5th parasternal intercostal spaces with ultrasound-guided (USG) bilateral parasternal intercostal nerve block. Sufentanil via patient-controlled intravenous analgesia (PCIA) was administered to all participants postoperatively. Pain score, total sufentanil consumption, and postoperative adverse events were recorded within the first 24 h. RESULTS: There were 20 and 21 patients in the PSI and control group, respectively. The PSI group required 20% less PCIA-sufentanil compared with the control group (54.05 ± 11.14 µg vs. 67.67 ± 8.92 µg, P < 0.001). In addition, pain numerical rating scale (NRS) scores were significantly lower in the PSI group compared with control patients, both at rest and upon coughing within 24 postoperative hours. Postoperative adverse events were generally reduced in the PSI group compared with controls. CONCLUSIONS: USG bilateral parasternal intercostal nerve block effectively reduces postoperative pain and adjuvant analgesic requirement, with good patient satisfaction, therefore constituting a good option for mediastinal mass resection by median sternotomy.

Usefulness of Parasternal Intercostal Muscle Ultrasound during Weaning from Mechanical Ventilation.

BACKGROUND: The assessment of diaphragm function with diaphragm ultrasound seems to bring important clinical information to describe diaphragm work and weakness. When the diaphragm is weak, extradiaphragmatic muscles may play an important role, but whether ultrasound can also assess their activity and function is unknown. This study aimed to (1) evaluate the feasibility of measuring the thickening of the parasternal intercostal and investigate the responsiveness of this muscle to assisted ventilation; and (2) evaluate whether a combined evaluation of the parasternal and the diaphragm could predict failure of a spontaneous breathing trial. METHODS: First, an exploratory evaluation of the parasternal in 23 healthy subjects. Second, the responsiveness of parasternal to several pressure support levels were studied in 16 patients. Last, parasternal activity was compared in presence or absence of diaphragm dysfunction (assessed by magnetic stimulation of the phrenic nerves and ultrasound) and in case of success/failure of a spontaneous breathing trial in 54 patients. RESULTS: The parasternal was easily accessible in all patients. The interobserver reproducibility was good (intraclass correlation coefficient, 0.77 (95% CI, 0.53 to 0.89). There was a progressive decrease in parasternal muscle thickening fraction with increasing levels of pressure support (Spearman ρ = -0.61 [95% CI, -0.74 to -0.44]; P < 0.0001) and an inverse correlation between parasternal muscle thickening fraction and the pressure generating capacity of the diaphragm (Spearman ρ = -0.79 [95% CI, -0.87 to -0.66]; P < 0.0001). The parasternal muscle thickening fraction was higher in patients with diaphragm dysfunction: 17% (10 to 25) versus 5% (3 to 8), P < 0.0001. The pressure generating capacity of the diaphragm, the diaphragm thickening fraction and the parasternal thickening fraction similarly predicted failure or the spontaneous breathing trial. CONCLUSIONS: Ultrasound assessment of the parasternal intercostal muscle is feasible in the intensive care unit and provides novel information regarding the respiratory capacity load balance.

CT-Derived Pretreatment Thoracic Sarcopenia Is Associated with Late Mortality after Thoracic Endovascular Aortic Repair.

BACKGROUND: Frailty, characterized by physiologic depletion, predicts postoperative morbidity and mortality in vascular surgery patients. CT-derived sarcopenia is a valuable method for objectively staging frailty preoperatively. PURPOSE: With prior analyses primarily measuring psoas cross-sectional area on CT, we compared a method of measuring thoracic sarcopenia to existing techniques of lumbar sarcopenia and assessed the association with long-term survival and outcomes post-Thoracic Endovascular Aortic Repair (TEVAR). METHODS: Prospectively collected data of 217 patients undergoing TEVAR from 2009 to 2012 were reviewed. Thoracic sarcopenia was quantified by measuring total area of the rectus abdominis, latissimus dorsi, intercostal, erector spinae, and external and internal oblique muscles at the T12 vertebral level. Total psoas area at the L3 was used to measure lumbar sarcopenia. RESULTS: 200 patients had preoperative imaging enabling measurements of thoracic sarcopenia, 186 of these patients were also assessed for lumbar sarcopenia. Thoracic sarcopenic patients were older, had lower body mass indices, were more commonly female, and most commonly being treated for aneurysms. Thoracic sarcopenic patients had significantly higher rates of congestive heart failure, hypertension, prior vascular intervention, and TEVAR-related adverse events. Thoracic sarcopenia was associated with significantly higher mortality at 2 and 5 years post-TEVAR (2-year mortality: 19% vs 8%, P = 0.02; 5-year mortality: 31% vs 18%, P = 0.03). Lumbar sarcopenia was not associated with increased mortality at any time point. Patients whose muscle mass degraded over 48-month follow-up did not experience significantly higher rates of adverse events. CONCLUSIONS: CT-derived thoracic sarcopenia, but not lumbar sarcopenia, is significantly associated with 5-year mortality post-TEVAR.

Ultrasound versus manipulation to determine an intercostal space for single-port thoracoscopy surgery: a diagnostic accuracy study.

BACKGROUND: Malposition of the intercostal space used for single-port thoracoscopy surgery can lead to problems. This study was to assess the accuracy of point-of-care ultrasound in verifying the position of intercostal space. METHODS: A total of 200 patients, ASA (American Society of Anesthesiologists) physical status I or II, who underwent single-port thoracoscopic lobectomy, were enrolled. After the induction of anesthesia, a thoracic team confirmed the incision position. Firstly, the intercostal space was located by a young resident thoracic surgeon by ultrasound. Secondly, the intercostal space was located by an experienced thoracic surgeon by manipulation. Finally, the investigator verified the location of the intercostal space under direct vision through thoracoscopy, which was recognized as standard method. The time required by ultrasound and manipulation were recorded. RESULTS: The inter-relationships between ultrasound and the standard method and between manipulation and the standard method were consistent. Manipulation positioning showed a sensitivity of 90.6% and specificity of 30% while ultrasound positioning showed a sensitivity of 87.1% and specificity of 60%. The specificity of ultrasound positioning was higher than that of manipulation position. The time required by ultrasound was shorter than that required by manipulation. CONCLUSIONS: Compared with the manipulation method, the ultrasound-guided method could accurately locate the intercostal space. Ultrasound requires less time than manipulation. TRIAL REGISTRATION: ISRCTN10722758. Registered 04 June 2019.

[Clinical evaluation of in-plane ultrasound-guided thoracic paravertebral block using laterally intercostal approach].

OBJECTIVE: To evaluate the feasibility and success rate of in-plane ultrasound-guided paravertebral block using laterally intercostal approach. METHODS: In the study, 27 patients undergoing elective thoracic surgery were selected to do paravertebral block preoperatively. The fifth intercostal space was scanned by ultrasound probe which was placed along the long axis of the rib and 8 cm lateral to the midline of the spine. The needle was advanced in increments aiming at the space between the internal and innermost intercostal muscles. Once the space between the muscles was achieved, 20 mL of 0.5% (mass fraction) ropivacaine was injected and a catheter was inserted. Whether the tip of catheter was in right place was evaluated by ultrasound image. The block dermatomes of cold sensation were recorded 10, 20 and 30 min after the bolus drug was given. Then 0.2% ropivacaine was infused with 6 mL/h via the catheter by an analgesia pump postoperatively. The block dermatomes of cold sensation and pain score were recorded 1, 6, 24 and 48 h postoperatively. RESULTS: The first attempt success rate of catheteration was 81.48% (22/27); the tips of catheter were proved in right places after the second or third attempt in 5 patients. The median numbers of the block dermatomes 10, 20 and 30 min after the bolus drug was given were 2, 3, 4; the median numbers of block dermatomes were 5, 5, 5, 4, and of pain score were 1, 1, 2, 2 at 1, 6, 24, 48 h postoperatively; no case of bilateral block, pneumothorax or vessel puncture occurred. CONCLUSION: Thoracic paravertebral block using laterally intercostal approach is feasible, which has high success rate of block and low rate of complications.

Randomized, Placebo-Controlled Trial of Biofeedback for the Treatment of Rumination.

OBJECTIVES: We previously demonstrated that rumination is produced by an unperceived, somatic response to food ingestion, and we developed an original biofeedback technique based on electromyography (EMG)-guided control of abdomino-thoracic muscular activity. Our aim was to demonstrate the superiority of biofeedback vs. placebo for the treatment of rumination. METHODS: Randomized, placebo-controlled trial performed in a referral center. Consecutive patients who fulfilled the Rome III criteria for rumination (18 women, 6 men; 19-79 years age) were selected and all included in the study; 1 patient assigned to placebo withdrew because of an unrelated accident. Abdomino-thoracic muscle activity after a challenge meal was recorded by EMG. The patients in the biofeedback group were shown the signal and instructed to control muscle activity, whereas the patients in the placebo group were not shown the signal and were given oral simethicone. Each patient underwent 3 sessions over a 10-day period. MAIN OUTCOME: number of rumination events as measured by questionnaires for 10 consecutive days before and after intervention. RESULTS: Patients on biofeedback (n=12) but not on placebo (n=11) effectively learned to reduce intercostal activity (by 51±6% vs. 10±7% increment on placebo; P<0.001) and anterior wall muscle activity (by 52±4% vs. 9±2% increment on placebo; P<0.001). Biofeedback treatment resulted in a 74±6% reduction in rumination activity (from 29±6 before to 7±2 daily events after intervention) vs. 1±14% on placebo; P=0.001 (from 21±2 before to 21±4 daily events after intervention). CONCLUSIONS: Rumination can be effectively corrected by biofeedback-guided control of abdomino-thoracic muscular activity.

Comparison of intrahepatic vein-to-liver parenchyma and intercostal muscle-to-liver parenchyma strain ratios in the assessment of liver fibrosis: which one should we use?

PURPOSE: The aims of this study were to investigate whether there is a difference in diagnostic value between vein to parenchyma strain ratio (VPSR) and muscle to parenchyma strain ratio (MPSR). METHODS: VPSR and MPSR were calculated via sonoelastography, and were recorded for comparison with histopathology. ROC analysis, the Mann-Whitney U test, the Kruskal-Wallis test, and Spearman's rank correlation test were used for statistical analysis. RESULTS: The study included 59 cases of individuals who underwent biopsy (29 women, 30 men). When the threshold value for VPSR was set at 3.23, the sensitivity was 96.2% and the specificity was 83.3% (p < 0.001, F ≥ 1). When the threshold value was set at 3.01 for MPR, the sensitivity was 88.7% and the specificity was 83.3% (p < 0.001, F ≥ 1). The areas under the curve values were VPSR 0.95 and MPSR 0.92 for F ≥ 1, VPSR 0.94 and MPSR 0.92 for F ≥ 2, and VPSR 1.00 and MPSR 0.76 for F = 3 (p < 0.001). The Spearman's correlation coefficient was 0.75, and a high positive concordance was found between VPSR and MPSR (p < 0.001). CONCLUSIONS: In this study, a high positive correlation was observed between two strain ratios, and VPSR was found to be more reliable than MPSR in determining liver fibrosis.

Accuracy of transthoracic ultrasound for the prediction of chest wall infiltration by lung cancer and of lung infiltration by chest wall tumours.

BACKGROUND: We wanted to determine the accuracy of transthoracic ultrasound in the prediction of chest wall infiltration by lung cancer or lung infiltration by chest wall tumours. METHODS: Patients having preoperative CT-scan suspect for lung/chest wall infiltration were prospectively enrolled. Inclusion criteria for lung cancer were: obliteration of extrapleural fat, obtuse angle between tumour and chest wall, associated pleural thickening. The criteria for chest wall tumours were: rib destruction and intercostal muscles infiltration with extrapleural fat obliteration and intrathoracic extension. Lung cancer patients with evident chest wall infiltration were excluded. Transthoracic ultrasound was preoperatively performed. Predictions were checked during surgical intervention. RESULTS: Twenty-three patients were preoperatively examined. Sensitivity, specificity, positive and negative predictive values of transthoracic ultrasound were 88.89%, 100%, 100% and 93.3%, respectively. Youden index was used to determine the best cut-off for tumour size in predicting lung/chest wall infiltration: 4.5cm. At univariate logistic regression, tumour size (<4.5 vs ≥ 4.5cm) (p=0.0072) was significantly associated with infiltration. CONCLUSIONS: Transthoracic ultrasound is a useful instrument for predicting neoplastic lung or chest wall infiltration in cases of suspect CT-scans and could be used as part of the preoperative workup to assess tumour staging and to plan the best surgical approach.

Pneumomediastinum and the aortic nipple: the clinical relevance of the left superior intercostal vein.

This article discusses the appearance of the "aortic nipple" in chest radiography, and reviews the embryology and anatomy of the left superior intercostal vein which causes the appearance of an "aortic nipple." This radiological sign is useful in differentiating certain thoracic pathologies, such as pneumomediastinum, pneumopericardium, and medial pneumothorax. Pneumomediastinum is an encompassing term describing the presence of air in the mediastinum, and may arise from a wide range of pathological conditions. Despite the well-described imaging of pneumomediastinum, it is sometimes difficult to differentiate from other conditions such as pneumopericardium and medial pneumothorax. A separate finding, "aortic nipple" is the radiographic term used to describe the lateral nipple-like projection from the aortic knob present in a small number of individuals. The aortic nipple corresponds to the end-on appearance of the left superior intercostal vein coursing around the aortic knob, and may be mistaken radiologically for lymphadenopathy or a neoplasm. Despite their relative independence, the aortic nipple is defined by new contours in cases of pneumomediastinum, taking on an "inverted aortic nipple" appearance. In this position, the inverted aortic nipple may facilitate radiographic discrimination of pneumomediastinum from similar conditions. This study aims to review the common clinical and radiographic features of both pneumomediastinum and the aortic nipple. The radiologic appearance of the aortic nipple occurring in unison with pneumomediastinum, and its potential role as a tool in the differentiation of pneumomediastinum from similarly presenting conditions will also be described.

The ratio of parasternal intercostal muscle-thickening fraction-to-diaphragm thickening fraction for predicting weaning failure.

BACKGROUND: Diaphragm dysfunction is associated with weaning outcomes in mechanical ventilation patients, in the case of diaphragm dysfunction, the accessory respiratory muscles would be recruited. The main purpose of this study is to explore the performance of parasternal intercostal muscle thickening fraction in relation to diaphragmatic thickening fraction ratio (TFic1/TFdi2) for predicting weaning outcomes, and compare its accuracy with D-RSBI in predicting weaning failure. MATERIALS AND METHODS: We prospectively enrolled consecutive patients from 7/2022-5/2023. We measured TFic, TFdi, and diaphragmatic excursion (DE3) by ultrasound and calculated the TFic/TFdi ratio and diaphragmatic rapid shallow breathing index (D-RSBI4). Receiver-operator characteristic (ROC5) curves evaluated the accuracy of the TFic/TFdi ratio and D-RSBI in predicting weaning failure. RESULTS: 161 were included in the final analysis, 114 patients (70.8%) were successfully weaned from mechanical ventilation. The TFic/TFdi ratio (AUROC = 0.887 (95% CI: 0.821-0.953)) was superior to the D-RSBI (AUROC = 0.875 (95% CI: 0.807-0.944)) for predicting weaning failure. CONCLUSIONS: The TFic/TFdi ratio predicted weaning failure with high accuracy and outperformed the D-RSBI.

Intercostal Muscle Function During Noninvasive Ventilation and Acute Hypercapnic Respiratory Failure.

BACKGROUND: Noninvasive ventilation (NIV) is a widely used and well-established treatment modality for respiratory failure. In patients with increased respiratory work of breathing, accessory muscles are commonly activated along with the diaphragm. Whereas diaphragm ultrasound has been utilized to assess outcomes of mechanical ventilation, the data on intercostal muscle ultrasound remain limited. We aimed to investigate the association between intercostal muscle thickening fraction (TF) and NIV failure in critical care patients with hypercapnic respiratory failure. METHODS: Critical care subjects receiving NIV for hypercapnic respiratory failure were enrolled in the study. The intercostal muscle TF was measured on admission day (day 0) and the following day (day 1). NIV failure was defined as the need for invasive mechanical ventilation or death during NIV therapy. RESULTS: A total of 158 subjects were enrolled, and 30 experienced NIV failure. Age, sex, and body mass index (BMI) were similar in the NIV success and failure groups. Acute Physiology And Chronic Health Evaluation II (APACHE II) and the Sequential Organ Failure Assessment (SOFA) scores were higher in the NIV failure group. In terms of causes of respiratory failure, the COPD exacerbation rate was higher in the NIV success group. TF was higher in the NIV failure group on both day 0 and day 1. The increased TF on the ICU admission day, with a cutoff value of 12%, was associated with NIV failure after adjusting for age, sex, BMI, APACHE II, and SOFA. Persistence of a higher TF value on both day 0 and day 1 was also associated with NIV failure risk. CONCLUSIONS: There was a positive relation between intercostal muscle TF measured by ultrasound and NIV failure, even after adjusting for APACHE II and SOFA scores.

Prolonged loss of intercostal muscle mass and its predictors in COVID-19 patients: A retrospective study from tertiary hospital.

Sarcopenia is a contributing factor in the development of long-COVID syndrome. We aimed to investigate how intercostal muscle mass changes over 3 months compared to other chest wall muscles following COVID-19 infection, along with identifying factors contributing to intercostal muscle loss during follow-up. We retrospectively studied 110 COVID-19 patients, analyzing muscle masses in the intercostal, pectoralis, and thoracic 12th vertebra level (T12) on initial and follow-up CT scans. Muscle mass was quantitatively assessed using density histogram analysis. We calculated the muscle difference ratio (MDR) as the following formula: (initial muscle mass - follow-up muscle mass)/initial muscle mass. Patients were categorized into 2 groups: <3 months follow-up (n = 53) and ≥ 3 months follow-up (n = 57). We employed stepwise logistic regression, using intercostal MDR ≥ 25% in follow-up as an independent variable and age < 65 years, ventilator use, steroid use, follow-up > 3 months, hospital stay > 13 days, body mass index < 18.5 kg/m², and female gender as dependent variables. The loss of intercostal muscle was the most severe among the 3 chest wall muscles in the CT follow-up. Intercostal MDR was significantly higher in the ≥ 3 months follow-up group compared to the < 3 months group (32.5 ±â€…23.6% vs 19.0 ±â€…21.1%, P = .002). There were no significant differences in pectoralis MDR or T12 MDR between the 2 groups. Stepwise logistic regression identified steroid use (3.494 (1.419-8.604), P = .007) and a follow-up period > 3 months [3.006 (1.339-6.748), P = .008] as predictors of intercostal MDR ≥ 25%. The intercostal muscle wasting was profound compared to that in the pectoralis and T12 skeletal muscles in a follow-up CT scan, and the intercostal muscle wasting was further aggravated after 3 months of COVID-19 infection. The use of steroids and a follow-up period exceeding 3 months were significant predictors for ≥ 25% of intercostal muscle wasting in follow-up.

Neuromuscular ultrasound for evaluation of the diaphragm.

Neuromuscular clinicians are often asked to evaluate the diaphragm for diagnostic and prognostic purposes. Traditionally, this evaluation is accomplished through history, physical exam, fluoroscopic sniff test, nerve conduction studies, and electromyography (EMG). Nerve conduction studies and EMG in this setting are challenging, uncomfortable, and can cause serious complications, such as pneumothorax. Neuromuscular ultrasound has emerged as a non-invasive technique that can be used in the structural and functional assessment of the diaphragm. In this study we review different techniques for assessing the diaphragm using neuromuscular ultrasound and the application of these techniques to enhance diagnosis and prognosis by neuromuscular clinicians.

An algorithm for the safety of costal diaphragm electromyography derived from ultrasound.

INTRODUCTION: Costal diaphragm electromyography (EMG) remains unpopular due to the risk of pneumothorax. In this study we assessed the safety of the "trans-intercostal" method of diaphragm EMG using B-mode ultrasound. METHODS: Twenty healthy subjects participated in this investigation. The diaphragm and the lung were visualized in the most distal intercostal space (dICS) with ultrasound. The risk of pneumothorax was assessed at the mid-clavicular, anterior, and mid-axillary levels, during normal and deep breathing, in supine and upright postures. RESULTS: The dICS at the anterior axillary level was the safest landmark for diaphragm EMG during normal breathing, with the subject supine. The mid-clavicular level is the least optimal location for EMG. The upright position and deep breaths increase the risk of pneumothorax. CONCLUSIONS: The safety of the trans-intercostal method of diaphragm EMG depends on the anatomic level chosen to insert the needle, patient position, and breathing pattern. Hence, we have developed a safety algorithm for electromyographers.