Work of breathing characteristics of seven portable ventilators

Bench-test comparison of 26 emergency and transport ventilators

Introduction

Numerous emergency and transport ventilators are commercialized and new generations arise constantly. The aim of this study was to evaluate a large panel of ventilators to allow clinicians to choose a device, taking into account their specificities of use.

Methods

This experimental bench-test took into account general characteristics and technical performances. Performances were assessed under different levels of FIO₂ (100%, 50% or Air-Mix), respiratory mechanics (compliance 30,70,120 mL/cmH₂O; resistance 5,10,20 cmH₂O/mL/s), and levels of leaks (3.5 to 12.5 L/min), using a test lung.

Results

In total 26 emergency and transport ventilators were analyzed and classified into four categories (ICU-like, n = 5; Sophisticated, n = 10; Simple, n = 9; Mass-casualty and military, n = 2). Oxygen consumption (7.1 to 15.8 L/min at F_IO₂ 100%) and the Air-Mix mode (F_IO₂ 45 to 86%) differed from one device to the other. Triggering performance was heterogeneous, but several sophisticated ventilators depicted triggering capabilities as efficient as ICU-like ventilators. Pressurization was not adequate for all devices. At baseline, all the ventilators were able to synchronize, but with variations among respiratory conditions. Leak compensation in most ICU-like and 4/10 sophisticated devices was able to correct at least partially for system leaks, but with variations among ventilators.

Conclusion

Major differences were observed between devices and categories, either in terms of general characteristics or technical reliability, across the spectrum of operation. Huge variability of tidal volume delivery with some devices in response to modifications in respiratory mechanics and F_IO₂ should make clinicians question their use in the clinical setting.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-014-0506-0) contains supplementary material, which is available to authorized users.

Maximizing oxygen delivery during mechanical ventilation with a portable oxygen concentrator

BACKGROUND

Transportation of the critically ill or injured war fighter requires the coordinated care and judicious use of resources. Availability of oxygen (O2) supplies for the mechanically ventilated patient is crucial. Size and weight of cylinders makes transport difficult and presents an increased risk of fire. A proposed solution is to use a portable oxygen concentrator (POC) for mechanical ventilation. We tested the SeQual Eclipse II POC paired with the Impact 754 and Pulmonetics LTV-1200 ventilators in the laboratory and evaluated the fraction of inspired oxygen (FIO2) across a range of minute volumes.

METHODS

Each ventilator was attached to a test lung and pressure, volume, flow, and inspired oxygen (FIO2) was measured by a gas or flow analyzer. Ventilators were tested at a tidal volume (VT) of 500 mL; an inspiratory time of 1.0 second; respiratory rates of 10, 20, and 30 breaths per minute; and positive end-expiratory pressure of 0 and 10 cm H2O. The LTV 1200 was tested with and without the expiratory bias flow. The Eclipse II was modified to provide pulse dosing on inspiration at 3 volumes (64, 128, and 192 mL) and continuous flow at 1 L/min to 3 L/min. Six combinations of ventilator settings were used with each POC setting for evaluation. O2 was injected at the ventilator gas outlet and patient y-piece for pulse dose and continuous flow. Additionally, continuous flow O2 was injected into the oxygen inlet port of the LTV 1200, and a reservoir bag, on the inlet port of the Impact 754. All tests were done with both ventilators using continuous flow, wall source O2 as a control. We also measured the FIO2 with the concentrator on the highest pulse dose setting while decreasing ventilator VT to compensate for the added volume.

RESULTS

The delivered FIO2 was highest when oxygen was injected into the ventilator circuit at the patient y-piece using pulse dosing, with the VT corrected. The next highest FIO2 was with continuous flow at the inlet (LTV), and reservoir (Impact). Electrical power consumption was less during pulse dose operation.

SUMMARY

Oxygen is a finite resource, which is cumbersome to transport and may present a fire hazard. The relatively high FIO2 delivered by the POC makes this method of O2 delivery a viable alternative to O2 cylinders. However, patients requiring an FIO2 of 1.0 would require additional compressed oxygen. This system allows O2 delivery up to 76% solely using electricity. An integrated ventilator or POC capable of automatically compensating VT for POC output is desirable. Further patient testing needs to be done to validate these laboratory findings.

Current Issues in Home Mechanical Ventilation

As modern health care continues to evolve, we expect and are seeing that more sophisticated medical care will be provided outside the traditional acute care environments. Advances in home medical technology, economic pressures, health-care consumerism, and societal changes are all factors playing a role in this evolution. Medically fragile and technology-dependent individuals who were once limited to care in acute and subacute institutional settings are now frequently cared for at home, most often by their immediate family members. Mechanical ventilation has found its way into the patient's home such that physicians and other providers must be prepared for the challenges associated with managing the conditions of complex, ventilator-dependent individuals outside of the walls, controls, and safety of the institutional setting. With little published science and recognized standards of practice, there are fewer rules to guide clinicians through this process. Experience has shown, however, that successful home management of ventilator-dependent individuals can be traced to a smooth and collaborative discharge from the hospital to home. Reimbursement and coverage issues must also be well understood to avoid the aggravation of denials and challenges for necessary equipment and assistance. Once home, a streamlined, patient-centered process supported by effective communication between all care providers can result in a safe and appropriate long-term home ventilation success story.

Correlation of arterial Pco2 and Petco2 in prehospital controlled ventilation

INTRODUCTION

This study was carried out to estimate the relationship between arterial PCO2 (PaCO2) and end-tidal carbon dioxide (PETCO2) during prehospital controlled ventilation and also to evaluate variation of the gradient between PCO2 and PETCO2 during prehospital transport.

METHODS

Measurements of PETCO2 from capnography values and PaCO2 from arterial blood gases were registered at the beginning (T(0)) and at the end (T(end)) of out-of-hospital management. For all patients requiring invasive ventilation, the gradient between PCO2 and PETCO2 was calculated for T(0) and T(end), the PaCO2-PETCO2 variation between T(end) and T(0) was also calculated.

RESULTS

One hundred patients were included in this study (mean age, 58.4 +/- 16.4 years; 57 were male). There was no variation of the mean gradient (DeltaPaCO2-PETCO2 ) during transport (8.64 +/- 13.5 mm Hg at T(0) and 7.26 +/- 12.94 mm Hg at T(end)). Thirty-six percent of patients (n = 36) had a gradient above +10 mm Hg, and for 6% of patients (n = 4) the gradient was lower than -10 mm Hg. The PaCO2-PETCO2 gradient was not significantly different according to the pathology, but was significantly higher in hypercapnic patients compared with hypocapnic or normocapnic patients. In patients with severe head injury, the capnia was normalized in 80% of patients at the end of the transport according to the last blood gas result. In this subgroup the DeltaPaCO2-PETCO2 (T(end) - T(0)) gradient was stable between T(0) and T(end) except in 20% of the patients for whom the DeltaPaCO2-PETCO2 was lower than -10 mm Hg. Fifty-four percent of critical care physicians had modified the respiratory setting after the first arterial blood gas results.

CONCLUSIONS

The PaCO2 cannot be estimated by the PETCO2 in the prehospital setting. There is wide variation in the gradient between PCO2 and PETCO2 depending on patient condition, and over time, the relationship does not remain constant and thus cannot be useful in prehospital ventilation management.

Understanding and implementing advances in ventilator capabilities

PURPOSE OF REVIEW

To review the changes in mechanical ventilation technology over the past year and identify areas that provide a benefit.

RECENT FINDINGS

The literature demonstrates a continued effort to improve patient ventilator synchrony though the development of new triggering and cycling methods. These techniques include using new signals and using closed loop techniques to respond to changes in patient breathing pattern. New modes of ventilation continue to be introduced, often without proof of efficacy. Fortunately, clinicians have developed alterations to new modes that improve utility and they continue to study these techniques clinically to determine appropriate use. Monitoring the patient remains an important area of investigation, with a flurry of activity surrounding pressure volume curves of the respiratory system. Finally, new ventilators have been introduced that combine high-end performance with small size and weight, while providing an on-board source of air.

SUMMARY

Mechanical ventilation is ubiquitous to intensive care. Advances in ventilator technology are rapid, and clinicians must keep abreast of changes in ventilator performance and application.