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

Estimation of Diaphragm Depth Based on Waist Circumference in the Thai Population

INTRODUCTION/AIMS

There is a potential risk of causing a pneumothorax during needle electromyography of the diaphragm. The diaphragm depth can be estimated from body mass index (BMI), but this may not be practical in bedbound patients. The objectives of this study were to formulate correlation equations to estimate diaphragm depth based on waist circumference (WC) and determine their validity.

METHODS

Personal data, weight, height, and WC were collected from healthy volunteers, and the diaphragm depth from the skin and diaphragm thickness of the participants were measured by ultrasonography. These data were used to formulate the equations for estimation of diaphragm depth based on WC, and the equations were validated by comparing the estimated diaphragm depths between BMI-based equations and WC-based equations.

RESULTS

A total of 100 volunteers (48 men and 52 women) were recruited. The median age of the participants was 27 years (interquartile range, 26). The mean WC was 83.3 cm. (standard deviation 7.8 cm.). The diaphragm depth ranged between 1.0 and 2.7 cm. Equations for estimation of the diaphragm depth were created for each hemidiaphragm using data from 80 participants: left hemidiaphragm depth = (0.03 × WC) - 0.89 (r² = 0.56); right hemidiaphragm depth = (0.03 × WC) - 0.94 (r² = 0.55) with 10-20% errors in 20 tested participants. The estimated diaphragm depths calculated from BMI and WC were comparable.

DISCUSSION

The WC-based equation can be used in addition to palpation techniques for guiding needle EMG insertion when ultrasound guidance is not available.

Electrophysiological assessment of respiratory function

While the traditional lung function tests are used to assess lung capacity and pulmonary function, they cannot evaluate respiratory driving function and the integrity of the conduction pathway from the central nervous system to the respiratory motor neuron in the spinal cord and to the diaphragm. The inspiratory trigger is sent from the central nervous system through the phrenic nerve and drives the diaphragm to generate inspiratory movement. Therefore, phrenic nerve stimulation and diaphragmatic electromyography are two fundamental methods to assess respiratory function. There are several useful tools to assess respiratory motor system including electrical or magnetic phrenic nerve stimulation, diaphragmatic needle electromyography, and diaphragmatic ultrasound. By these means, physicians can assess current respiratory status in different neurological diseases that affect respiratory muscles, follow-up of the severity of respiratory impairment, help to predict the chance of successfully weaning from ventilatory support, and confirm clinical diagnoses such as diaphragmatic myoclonus. Although some of these tests require special training, applying these neurophysiological assessments in clinical practice is highly recommended.

Primary Acute Neuromuscular Respiratory Failure

Neurologists are often called to evaluate patients with both defined and undiagnosed neuromuscular disorders when respiratory failure develops to determine if there is a neuromuscular cause. Being able to confidently diagnose neuromuscular respiratory failure and intervene appropriately is imperative, as early intervention and determination of the cause have survival implications. Outcomes are poor when the cause of neuromuscular weakness and resultant respiratory failure cannot be identified. This review discusses the clinical recognition of primary neuromuscular respiratory failure, its pathophysiology, diagnostic evaluation, and management, focusing on management of respiratory failure in the setting of Guillain-Barré syndrome and myasthenic crisis.

Respiratory failure because of neuromuscular disease

PURPOSE OF REVIEW

Understanding the mechanisms and abnormalities of respiratory function in neuromuscular disease is critical to supporting the patient and maintaining ventilation in the face of acute or chronic progressive impairment.

RECENT FINDINGS

Retrospective clinical studies reviewing the care of patients with Guillain-Barré syndrome and myasthenia have shown a disturbingly high mortality following step-down from intensive care. This implies high dependency and rehabilitation management is failing despite evidence that delayed improvement can occur with long-term care. A variety of mechanisms of phrenic nerve impairment have been recognized with newer investigation techniques, including EMG and ultrasound. Specific treatment for progressive neuromuscular and muscle disease has been increasingly possible particularly for the treatment of myasthenia, metabolic myopathies, and Duchenne muscular dystrophy. For those conditions without specific treatment, it has been increasingly possible to support ventilation in the domiciliary setting with newer techniques of noninvasive ventilation and better airway clearance. There remained several areas of vigorous debates, including the role for tracheostomy care and the place of respiratory muscle training and phrenic nerve/diaphragm pacing.

SUMMARY

Recent studies and systematic reviews have defined criteria for anticipating, recognizing, and managing ventilatory failure because of acute neuromuscular disease. The care of patients requiring long-term noninvasive ventilatory support for chronic disorders has also evolved. This has resulted in significantly improved survival for patients requiring domiciliary ventilatory support.

[Exploring the diaphragm: Ultrasound is essential]

The diaphragm is the muscle most implicated in breathing. Its morphological exploration usually depends on pulmonary radiography, fluoroscopy, CT-scanning and MRI. Its function is evaluated by the classical respiratory functional tests, the measurement of maximum inspiratory and expiratory pressures, the transdiaphragmatic pressure and even an electromyogram. Ultrasound is a technique still insufficiently used in respiratory medicine. It offers, however, many advantages: it is easy to implement, there is no irradiation, it is usable at the bedside, particularly when the patient is immobile or in intensive care. The results of the examination are immediately available. It allows morphological and dynamic study of each hemidiaphragm as well as providing invaluable information on the thoracic and subdiaphragmatic environment. Its field of exploration is extremely wide: raised hemidiaphragm, dyspnea following a stroke or a surgical procedure (thoracic or abdominal), road accident trauma, diagnosis and follow-up of a paresis or paralysis, evaluation of diaphragmatic mobility during the course of COPD (Chronic Obstructive Pulmonary Disease) and many other pathologies. Ultrasound is insufficiently used in pleural disease and even less so in the evaluation of the morphology and function of the diaphragm.

Safety of needle electromyography of the diaphragm: Anterior lung margins in quietly breathing healthy subjects

INTRODUCTION

Controversy persists as to whether the lung interposes on the needle electrode insertion path during diaphragm electromyography (EMG).

METHODS

Using high-resolution ultrasonography, we measured the distances between the medial recess of the intercostal spaces (ICSs) around the mid-clavicular line (MCL) and the lung margin. We performed measurements bilaterally during quiet breathing in the seated and supine positions.

RESULTS

We studied 10 young healthy men and found that, in the first ICS with the medial recess clearly (i.e., several cm) lateral to MCL (usually the eighth ICS), the distance between the recommended insertion site and the lung margin varied from 7.5 to 17 cm. The distance was slightly larger on the right side and in the supine position.

CONCLUSIONS

This study confirms that properly conducted "trans-intercostal" needle EMG of the diaphragm is generally safe in healthy subjects. Muscle Nerve 54: 54-57, 2016.

Guiding intramuscular diaphragm injections using real-time ultrasound and electromyography

INTRODUCTION

We describe a unique method that combines ultrasound and electromyography to guide intramuscular diaphragm injections in anesthetized large animals.

METHODS

Ultrasound was used to visualize the diaphragm on each side of spontaneously breathing, anesthetized beagle dogs and cynomolgus macaques. An electromyography (EMG) needle was introduced and directed by ultrasound to confirm that the needle entered the muscular portion of the diaphragm, and methylene blue was injected. Injection accuracy was confirmed upon necropsy by tracking the spread of methylene blue.

RESULTS

All methylene blue injections were confirmed to have been placed appropriately into the diaphragm.

CONCLUSIONS

This study demonstrates the feasibility and accuracy of using ultrasound and EMG to guide injections and to reduce complications associated with conventional blind techniques. Ultrasound guidance can be used for clinical EMG of the diaphragm. Future applications may include targeted diaphragm injections with gene replacement therapy in neuromuscular diseases.

The utility of musculoskeletal ultrasound in rehabilitation settings

Aside from its prompt use in musculoskeletal injuries (sports lesions, degenerative/inflammatory joint disorders, and peripheral nerve pathologies), ultrasonographic imaging can be used quite conveniently in various types of rehabilitation conditions as well. If used in a rehabilitation setting, ultrasound can significantly contribute to the diagnostic/therapeutic algorithm of rehabilitation patients. Accordingly, in this article, the authors focus on the diagnostic/interventional utility of ultrasound particularly for shoulder problems, overuse injuries of wheelchair users, heterotopic ossification, amputee follow-up, peripheral nerve and botulinum toxin injections, and diaphragm imaging/electromyography.