Use of Home Ventilators for Ventilatory Support during Magnetic Resonance Imaging

Special Article - Pulmonary Critical Care & Sleep Medicine

Austin J Pulm Respir Med 2016; 3(1): 1040.

Use of Home Ventilators for Ventilatory Support during Magnetic Resonance Imaging

Ogna A1,3*, Ambrosi X¹, Prigent H², Falaize L2,3, Leroux K4, Annane D¹, Carlier R5, Orlikowski D1,3 and Lofaso F²

¹Service de Réanimation Médicale et Unité de Ventilation à Domicile, AP-HP, Hôpital Raymond Poincaré, France

²Service de Physiologie-Explorations Fonctionnelles, APHP, Hôpital Raymond Poincaré, France

³INSERM CIC 14.29, AP-HP, Hôpital Raymond Poincaré, France

4ASV Sante, France

5Service d’Imagerie médicale, AP-HP, Hôpital Raymond Poincaré, France

*Corresponding author: Ogna A, Service de Réanimation Médicale et Unité de Ventilation à Domicile, AP-HP, Hôpital Raymond Poincaré 92380 Garches, France

Received: April 03, 2016; Accepted: May 18, 2016; Published: May 23, 2016

Abstract

Purpose: Magnetic Resonance Imaging (MRI) is a valuable diagnostic tool for neuroimaging in the Emergency and Critical Care setting, but its use may be limited in acutely and chronically ventilated patients, who cannot maintain the supine position in spontaneous breathing for the duration required for the procedure, as it may be the case in acute and chronic neurological and neuromuscular diseases with diaphragm involvement.

We aimed to evaluate the performance of home life support ventilators used with a longer circuit, allowing the application of ventilatory support during MRI. The study hypothesis was that home ventilators are accurate in delivery the set ventilatory parameters despite a modified circuit.

Materials and Methods: Four non-MRI-compatible life-support home ventilators were tested on a bench using 3 circuits of 4.8 m length and 3 ventilation settings.

Results: We found measurable differences in the efficacy of the ventilation delivered to the test lung, which was influenced from the used ventilator, the type of circuit and the ventilation parameters. In the volumetric setting with unvented circuit, the difference between set VT and delivered VT ranged between -10% and +3%. In the barometric setting, only the ventilators providing automatic compensation for circuit compliance and resistance were reliable in the delivery of the set inspiratory and end-expiratory pressures.

Conclusion: The use of home ventilators during MRI may represent a valuable alternative when a MRI-compatible ventilator is not available, but may require an adjustment of the ventilatory setting, and a systematic verification of the parameters effectively delivered to the patient.

Keywords: Respiratory failure; Home ventilators; Magnetic resonance imaging; Critical care; Bench evaluation

Abbreviations

ICU: Intensive Care Unit; MRI: Magnetic Resonance Imaging; PC-CMV: Pressure-Controlled Mechanical Ventilation Mode; VC-CMV: Volume-Controlled Mechanical Ventilation Mode; VT: Respiratory Tidal Volume

Introduction

In recent years, Magnetic Resonance Imaging (MRI) has been increasingly performed as a diagnostic exam, and currently represents an essential diagnostic tool for acute and chronic diseases affecting the neurological system [1-5]. Among the situations where neuroimaging is indicated, the execution of a MRI may be problematic in patients presenting acute or chronic respiratory failure and who are unable to sustain the supine position in spontaneous breathing for the exam’s duration. These situations may be present in the Emergency and Critical Care setting, right where neuroimaging may be required. For example, patients with neuromuscular disorders or cervical spinal cord injuries may present a restrictive respiratory failure, requiring ventilatory support in the acute phase or in the long term, especially in case of diaphragmatic involvement [6-8]. The use of mechanical ventilation during MRI may allow to overcome this problem, which is shared with other intensive or critical care patients requiring ventilatory support. The application of mechanical ventilation during MRI imaging raises an issue, since the unique electromagnetic environment of MRI requires dedicated medical devices, but only very few ICU- and transport-ventilators are MRI-compatible [9] and the acquisition of such an expensive ventilator may not be warranted if the projected use is infrequent. A possible alternative may consist in leaving the ventilator in the MRI control room, where non-MRIspecific devices are allowed, and to ventilate the patient using a longer circuit [10]. This would allow to use portable life-support ventilators during MRI, whose performance in this setting has however not yet been tested.

The aim of our bench study was to evaluate the performance of life-support home ventilators for the use with a longer circuit, allowing the application of ventilatory support during MRI. The study hypothesis was that home ventilators are accurate in delivery the set ventilatory parameters despite a modified circuit in the volumetric ventilation mode, but an adaptation of the setting may be necessary in the barometric ventilatory mode to compensate for the increased circuit resistance.

Methods

Four life-support home ventilators were studied: VIVO 60 (BREAS, Sweden), Astral 150 (ResMed, France), PB 560 (Covidien, USA) and Trilogy 100 (Philips Respironics, USA). A volumecontrolled setting (VC-CMV with Tidal Volume (VT) 500 ml) was tested in the different configurations available for each ventilator: double limb circuit (VIVO 60, Astral 150, PB 560), single limb circuit with expiratory valve (VIVO 60, Astral 150, PB 560), single limb vented circuit (VIVO 60, Trilogy 100). Three standard circuits of 22 mm diameter were assembled in series for a total circuit length of 4.8 m; in the MRI room of our hospital, this length allowed to place the ventilator in the control room and to reach the patient lying in the MRI, passing the circuit in a waveguide feed through in the Faraday cage. A calibrated expiratory leak (Whisper Swivel II, Philips Respironics) was used in the vented setting. Two pressure-controlled setting (PC-CMV at 20 cm H2O and 15 cm H2O respectively, PEEP 5 cmH2O) were also tested with the single-limb vented circuit (VIVO 60, Astral 150, Trilogy 100).

The test ventilator was connected via the test circuit to a lung model (Michigan Dual Adult Test Lung TTL 2600i, Michigan Instruments, USA). The compliance of the lung model was set at 30 mL/cmH2O, and the airway resistance at 5 cm H2O/L.s (Pneuflo Rp5, Michigan Instruments, Grand Rapids, Michigan), corresponding to a restrictive adult pattern. Flow and pressure signals were captured near the test lung, using a Fleischman pneumotachograph (Fleisch, Switzerland) and an analog/digital system (MP150, Biopac Systems, USA) (Figure 1). For each ventilator and each setting, the effectively delivered VT and pressures were recorded over 15 respiratory cycles, after a stabilization time of 2 minutes.