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Influence of Two Different Interfaces for Noninvasive Ventilation Compared to Invasive Ventilation on the Mechanical Properties and Performance of a Respiratory System^*

A Lung Model Study

^* From the Department of Anaesthesiology, Emergency, and Critical Care Medicine (Drs. Moerer, Quintel, and Neumann), University of Göttingen, Göttingen, Germany; University of Göttingen (Mr. Fischer and Mr. Hartelt), Göttingen, Germany; Department of Anaethesiology and Critical Care Medicine (Dr. Kuvaki), Balkan Dokuz Eylül University School of Medicine, Izmir, Turkey.

Correspondence to: Peter Neumann, MD, PhD, Department of Anaesthesiology, Emergency and Intensive Care Medicine, Georg-August-University of Göttingen, Robert Koch Str. 40, D-37075 Göttingen, Germany; e-mail: pneuman{at}gwdg.de

Abstract

Background: Noninvasive ventilation (NIV) is increasingly used in intensive care medicine, but only little information is available how different NIV interfaces affect the performance of a ventilatory system. Therefore, we compared delay times, pressure time products (PTPs), and wasted efforts during inspiration among patients receiving invasive ventilation and NIV with a helmet (NIV-H) or a face mask (NIV-FM).

Methods: Using an in vitro lung model capable of simulating spontaneous breathing, gas flow and airway pressure were measured with varying positive end-expiratory pressure and pressure support (PS) levels. Wasted efforts were determined while lung compliance, respiratory rate (RR), continuous positive airway pressure (CPAP), and PS levels were changed.

Results: Delay times were more than twice as long with a helmet compared to NIV-FM or invasive ventilation (p < 0.001), but decreased during NIV-H with increasing CPAP (p < 0.001) and PS levels (p < 0.001). During the initial inspiratory phase, PTP was smaller with NIV-H compared to NIV-FM or invasive ventilation, but not so when a complete inspiration with PS was evaluated. Wasted efforts occurred earlier during NIV-H and were aggravated with rising PS, RR, and compliance.

Conclusions: Although delay times are prolonged during NIV-H, PTP is initially smaller compared to NIV-FM and invasive ventilation, indicating less work of breathing due to the high volume the patient can access. Increasing the CPAP or PS level decreases delay times in NIV-H and should therefore be considered whenever possible. Wasted inspiratory efforts occurred at higher RRs and should carefully be monitored during NIV.

Key Words: facemask • helmet • invasive ventilation • noninvasive ventilation • pressure support ventilation • trigger

This article has been cited by other articles:

				D. Chiumello Is the Helmet Different Than the Face Mask in Delivering Noninvasive Ventilation? Chest, June 1, 2006; 129(6): 1402 - 1403. [Full Text] [PDF]