Use of ventilation bag for the respiratory support during magnetic resonance imaging in Arnold-Chiari ventilated patients, a case report

Abstract

Context: Magnetic Resonance Imaging (MRI) is an essential diagnostic tool for neuroimaging tissues such as the spinal cord. Unfortunately, the use of MRI may be limited in ventilated patients, who cannot maintain the supine position in spontaneous breathing for the whole duration of the exam (i.e. neuro-muscular patients with diaphragm involvement). The use of MRI-compatible ventilator during MRI could be a solution but they are not universally available. Furthermore, their performances are not up to those of the conventional ones and they are not always compatible with Non Invasive Ventilation (NIV).

Findings: This case report describes an easy and low-cost solution to ventilate a patient non-invasively during the MRI procedure. The patient in this case was a 45-yr-old man, wheelchair-dependent and chronically ventilated in NIV with a forced vital capacity in supine position of 370 ml (10% of predicted normal), affected by Arnold-Chiari Syndrome, and in need of a MRI diagnostic control.

Conclusion: The technique proposed, that does not affect the MRI images quality, consists in ventilating the patient using a simple nonmetallic Ventilation Bag, operated by a Respiratory Therapist. This has been proven a useful and economical solution for ventilatory support during MRI for a respiratory-dependent patient with Arnold-Chiari Syndrome.

Introduction

Magnetic Resonance Imaging (MRI) is an essential diagnostic tool for neuroimaging tissues such as the spinal cord,^1,2 and requires to lay in the supine position into the magnet.

Many patients with high-level spinal cord disease are in need of ventilatory support during MRI, as they cannot maintain the supine position in spontaneous breathing for the whole duration of the exam.³

These patients have a combination of reduced lung and chest wall compliance. Their respiratory muscle weakness leads to a decrease in vital capacity (VC) and therefore to hypoventilation.⁴ Most importantly and of relevance for MRI examination, VC can be significantly lower in the supine position then in the sitting position.⁵

To overcome hypoventilation these patients use long-term Non Invasive Ventilation (NIV) that supports them in breathing, prolongs their survival and improves their quality of life.⁶

MRI-compatible ventilators are a good solution to ventilate patients avoiding electromagnetic interferences. However, in many rehabilitation hospitals, MRI-compatible ventilators are not available because of their high costs and infrequent use.

Transfer of the patient to an equipped MRI center is difficult for the high cost and the patient discomfort. Furthermore, it does not guarantee a better result: the hospital should be equipped with an MRI compatible ventilator suitable for NIV, the team should be expert in NIV, and, not less importantly, the patient should be adaptable to an unknown ventilator.

Furthermore, the performances of MRI-compatible ventilators are not equal to the ones of conventional ventilators^7,8 and their set up is not always suitable for NIV.

An alternative to MRI-compatible ventilators may consist in using a Home Ventilator placed in the control room, where no restrictions on magnetic devices apply, and connected to the patient using a long circuit.

However, the reproducibility of this approach is limited by the fact that the design of the circuit is highly dependent on the MRI room and department’s architecture.^9,10

Moreover, the settings of the Home Ventilator are also extremely sensitive to the type of ventilator and to the specific hydraulic characteristics of the circuit used,^11,12 posing a real challenge when needed to be tuned for a real patient.

The purpose of this report is to describe a successful, safe, and economical technique that can be used to ventilate a respiratory-dependent patient while performing an MRI and that consists in using a Ventilation Bag.

Case report

The patient was a 45-yr-old wheelchair-dependent man with Arnold-Chiari Syndrome type 1, syringomyelia, hydrocephalus shunted, kyphoscoliosis, generalized spasticity, respiratory failure type II in NIV (20 h/day) through oronasal mask during night-time and Mouth Piece Ventilation during daytime (ventilator model: Trilogy 100, Philips Respironics, USA).

During the hospitalization, clinical worsening was noted: an increase in spasticity and opisthotonus events, followed by a need for a longer daytime ventilation, nystagmus, and neurological bladder. These conditions required a diagnostic analysis through MRI.

His arterial blood gas (ABG) was: pH 7.46, PCO2 47 mmHg, PO2 92 mmHg in ambient air; his forced vital capacity (FVC) in sitting position was 820 ml (23% of predicted normal), FVC in supine position was 370 ml (10% of predicted normal), and he was unable to breathe unassisted in the supine position for more than a few minutes.

The patient was thus in need of ventilatory support during MRI, to overcome the respiratory failure, and to minimize the risk of movements and the consequent artifacts in the imaging.

First, the technique was tested by training the patient to be ventilated in the supine position for 30 consecutive minutes with a Ventilation Bag (model RA401, Easyred), operated by a Respiratory Therapist. The Ventilation Bag was connected by a 30 cm ventilator circuit (model Airlife corrugated EVA tubing, 22 mm) and a mouth piece (model: angled mouthpiece, 22 mm, FC06566, Respironics). SpO2 and dyspnea symptom was monitored during this training, and the ABG was verified immediately after. His SpO2 remained larger than 95% throughout the whole procedure, no dyspnea was referred and ABG: pH 7,46; pCO2 38 mmHg; pO2 111 mmHg. After the successful test and patient training, the MRI examination was performed using a 1.5 T MRI (Philips Achieva Intera), with a 16-Channel Head Coil.

The respiratory therapist manually ventilated the patient (Figure 1), throughout the whole examination period, except for some sequences (T2 TSE sagittal and T2 TSE axial), that allow no interferences, for a maximum time of 3.47 min, in which the patient was able to maintain the ventilatory autonomy.

Figure 1.

MRI setup. Ventilation Bag connected by a 30 cm ventilator circuit and an angled mouthpiece operated by a Respiratory therapist during MRI using a 1.5 T with a 16-Channel Head Coil.

Sequences: Survey; T2 TSE sagittal; T1 TSE sagittal; T2 TSE axial; STIR sagittal; T2 TSE coronal.

The MRI examination lasted 18.55 min.

This technique allowed performing the exam safely and comfortably without affecting the MRI images quality (Figure 2). MRI findings: malacia and dystrophy and downward displacement of the cerebellar tonsils (C1 level), vermis and brainstem, myelomalacia at level C1-C2 with large intramedullary and right paramedian syringomyelic cavity seen until C5. These findings explained the ventilatory and neurological worsening.

Figure 2.

T2 Arnold – Chiari malformation, demonstrating tonsil displacement and syringomyelic cavity from C2 to C5.

Discussion

Ventilatory insufficiency requiring NIV is a relative contraindication to many diagnostic procedures such as bronchoscopy, gastroscopy, and MRI or surgical procedures such as gastrostomy and spinal surgery for scoliosis.

During these procedures, NIV should be always preferred instead of invasive as avoiding intubation reduces patient morbidity, hospital stay, and overall costs.^13,14 However NIV still remains a challenge and a unconventional tool.¹⁵

This case report described here for the first time the use of a nonmetallic Ventilation Bag (a NIV method) operated by a Respiratory Therapist to allow ventilator dependent patients to perform a MRI examination.

This technique is safe and easy only with cooperating patients, not critically ill, in the hands of a team expert in manual ventilation and in MRI procedures.

Patients using manual ventilation during MRI need to be alert, cooperative, and well trained before the procedure and they need to have a clear understanding of what is required from them during the procedure.

To exclude any complications of the manual ventilation, the technique should be performed only by expert Respiratory Therapists, however, we cannot exclude the occurrence of adverse effects, that have been in any case rarely documented, usually always in emergency settings, as aspiration, gastric dilatation, lung injury from over-stretching, hypoventilation or hyperventilation.^16–18

Moreover, the operating respiratory therapist clearly needs to be trained according to the hospital MRI safety guidelines and emergency procedures to reduce any risk.

As the respiratory therapist needs to stay inside the MRI room during the whole examination, they are exposed to magnetic fields. Even if the MRI hazards for professional are low (biological effects, vertigo and nausea sensation), we recommend to follow the MRI procedures and exposure limits suggested by the Health Protection Agency (HPA), International Electrotechnical Commission (IEC), and International Commission on Non-Ionising Radiation (ICNIRP).¹⁹

Conclusion

In turn, the use of a simple Ventilation Bag has been proven a safe and low-cost alternative to the use of MRI-compatible ventilators or of Home Ventilators, allowing to perform an MRI examination and suitable for ventilated, not critically ill, patient admitted in rehabilitation hospitals.

Disclaimer statements

Contributors Claudia Enrichi contributed to conception and design of the study, analyzed and interpreted data, drafted and revised the manuscript, and contributed to the approval of the final version of the manuscript. Cristiano Zanetti, Rosaria Stabile, Francesco Piccione, Carla Carollo, Luca Ghezzo analyzed and interpreted data, drafted and revised the manuscript, and contributed to the approval of the final version of the manuscript.

Funding None.

Declaration of interest None.

Conflicts of interest The authors report no potential conflict of interest.