Lung and diaphragm protective ventilation: a synthesis of recent data

ABSTRACT

Introduction

: To adhere to the Hippocratic Oath, to ‘first, do no harm’, we need to make every effort to minimize the adverse effects of mechanical ventilation. Our understanding of the mechanisms of ventilator-induced lung injury (VILI) and ventilator-induced diaphragm dysfunction (VIDD) has increased in recent years. Research focuses now on methods to monitor lung stress and inhomogeneity and targets we should aim for when setting the ventilator. In parallel, efforts to promote early assisted ventilation to prevent VIDD have revealed new challenges, such as titrating inspiratory effort and synchronizing the mechanical with the patients’ spontaneous breaths, while at the same time adhering to lung-protective targets.

Areas covered

This is a narrative review of the key mechanisms contributing to VILI and VIDD and the methods currently available to evaluate and mitigate the risk of lung and diaphragm injury.

Expert opinion

Implementing lung and diaphragm protective ventilation requires individualizing the ventilator settings, and this can only be accomplished by exploiting in everyday clinical practice the tools available to monitor lung stress and inhomogeneity, inspiratory effort, and patient–ventilator interaction.

KEYWORDS:

• ARDS
• ventilator-induced lung injury (VILI)
• ventilator-induced diaphragmatic dysfunction (VIDD)
• inspiratory effort
• monitoring

Article highlights

• Lung and diaphragm protective ventilation consists of interventions aiming at normalizing key respiratory system functions affected by mechanical ventilation, mainly the distribution of ventilation, the alveolar stress, and the diaphragmatic contractions.

• The inhomogeneous distribution of ventilation plays a cardinal role in the development of VILI, and can be improved by prone position, appropriate PEEP, and spontaneous breathing. Electrical impedance tomography is a promising monitoring technique, enabling visualization of the distribution of ventilation.

• The driving pressure is an easily applicable index of tidal lung stress, as tidal volume is normalized to the functional lung size. The driving pressure can also be measured in assisted ventilation, but, in pressure support it can be overestimated by expiratory muscle contraction. The transpulmonary driving pressure is a better indicator of lung stress when chest wall elastance is abnormal.

• Monitoring of esophageal pressure can facilitate lung and diaphragm protective ventilation, as the transpulmonary pressures help to evaluate lung stress and distribution of ventilation, while the swings of esophageal pressure enable monitoring inspiratory effort and patient–ventilator interactions during assisted ventilation.

• Diaphragmatic contractions improve the distribution of ventilation and prevent diaphragm disuse atrophy, therefore spontaneous breathing plays a key role in lung and diaphragm protective ventilation, but cautious titration of effort, avoiding both excessively low and high effort as well as asynchronies is necessary. Diaphragm pacing is a promising new method to maintain diaphragmatic contractions when deep sedation is needed.

Declaration of Interests

K. Vaporidi has received speakers’ fees from Medtronic. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewer disclosures

A reviewer on this manuscript has disclosed that they have conducted the referenced work on phrenic nerve stimulation. The same reviewer is also a consultant for the company that is developing the technology (Lungpacer). Peer reviewers on this manuscript have no other relevant financial relationships or otherwise to disclose.

Additional information

Funding

This paper was not funded.