Lung-protective ventilation
Lung-protective ventilation is an important method for minimizing the mechanical load on the lungs caused by mechanical ventilation.1 Although ventilation is life-saving in many cases and indispensable in intensive care and emergency medicine, ventilation-induced lung injury can occur, which may have long-term consequences for patients.
Lung-protective ventilation does not describe a standardized guideline, but it includes guidelines for setting ventilation parameters to ensure gentle ventilation and counteract lung damage. Read this article to find out how it relates to the Open Lung concept and how WEINMANN ventilators support this form of ventilation.
Definition: Lung-protective ventilation
Lung-protective ventilation (LPV) is a gentle form of mechanical ventilation used in intensive care and emergency medicine. The aim of this ventilation method is to minimize ventilator-induced lung injury (VILI) and at the same time ensure sufficient pulmonary gas exchange.
It has its origins in the intensive care management of acute respiratory distress syndrome (ARDS), which is why most studies and recommendations refer to this clinical picture. Although there are currently no binding guidelines for setting ventilation parameters, certain basic principles have become established.
Ventilation parameters
One central aspect is the use of low tidal volumes. We recommend 4–6 ml/kg ideal body weight (IBW). The tidal volume refers to the IBW, as the lungs are proportional to height. Since the lungs do not shrink or grow with the patients overweight or underweight, the tidal volume should not be adjusted to the real body weight. This ensures that patients can be ventilated in the same way regardless of their actual weight.2
Another important parameter in lung-protective ventilation is the limitation of the inspiratory oxygen concentration (FiO2) to less than 60%. This prevents the formation of free oxygen radicals that can damage lung tissue.
In addition, an optimal positive end-expiratory pressure (PEEP) should be set in accordance with the PEEP table of the ARDS Network3. This is the way to achieve the best possible SpO2 and paO2 values with minimal FiO2 and stable hemodynamics during lung-protective ventilation.
To avoid barotrauma, the inspiratory plateau pressure should be reduced to less than 30 mbar if possible. In addition, the pressure difference between PEEP and the upper pressure level should be kept as low as possible, ideally below 15 mbar.
In summary, the following parameters result for lung-protective ventilation:
- Tidal volume: 4–6 ml/kg IBW
- FiO2: < 60%
- PEEP: according to the cited PEEP table
- Plateau pressure: < 30 mbar
- Pressure difference between PEEP and upper pressure level: < 15 mbar 4
Objectives of lung-protective ventilation
Lung-protective ventilation is intended to protect the lungs through gentle ventilation and to recruit as many lung units as possible. This includes setting the PEEP high enough to keep the lungs open. At the same time, the pInsp is kept low to prevent overexpansion and damage to the lungs. This aims to prevent collapsed alveoli and atelectasis (atelectrauma) and reduce possible complications like ventilator-induced lung injury. Such lung injury can manifest in the form of volutrauma, barotrauma and biotrauma, often leading to inflammation, impaired gas exchange and respiratory arrest.5
Another important aim of lung-protective ventilation is to avoid shearing forces. These forces occur when collapsed and ventilated alveoli are directly adjacent to each other and multiply the ventilation pressure. Such shearing can damage the cells of the membrane and cause pro-inflammatory mediators to be released.6
In patients with severe ARDS, lung-protective ventilation can significantly reduce mortality through the application of low tidal volumes.7 Low tidal volumes moreover contribute to recruitment in the infiltrated, atelectatic and consolidated lung, reduce increased anatomical and alveolar dead space and prevent high inspiratory O2 concentrations. In addition, low tidal volumes protect the ventilated lung areas and, if possible, support the maintenance of spontaneous breathing.8
Lung-protective ventilation can improve the prognosis in severe acute respiratory failure.9
Advantages of lung-protective ventilation
Lung-protective ventilation offers considerable advantages for intensive care patients, particularly those with acute lung injury (ALI) and ARDS. A study by the American ARDS Network showed that gentle ventilation significantly reduces mortality: The mortality rate dropped from 39.8% to 31.0%, thereby allowing the concluded that the form of ventilation significantly improves the survival rate.
In addition, lung-protective ventilation minimizes the mechanical stress on the lungs caused by mechanical ventilation and secondary organ dysfunction. Furthermore, it reduces the duration of ventilation, optimizes oxygen supply and improves lung physiology.7 For these reasons, postoperative pulmonary complications are reduced and the relative risk of death on day 28 is decreased.10
The open-lung concept and lung-protective ventilation
The open lung concept is a ventilation maneuver introduced by Lachmann that supports lung-protective ventilation. The lungs are kept open and functional throughout ventilation to improve oxygenation and promote the release of carbon dioxide. In this way, further harm to the lung tissue is minimized and general respiratory function is improved.
The open-lung concept and adaptation to lung-protective ventilation and its characteristics are performed in several steps:
- Opening of the lungs: First, the lungs are opened with pressure-controlled ventilation (PVC) and a relatively high peak inspiratory pressure (pInsp). Inspiratory peak pressures of 40–60 mbar should be administered for at least 10 to 30 breaths. The ratio between inspiration and expiration (I:E) should be around 1:1 or 2:1 and PEEP should be 10–20 mbar.
- Keeping the lungs open: The lungs are then kept open by gradually adjusting the inspiratory pressure to the lowest pressure at which recruitment does not get lost. PEEP remains between 10 and 20 mbar.
- Adapting to lung-protective ventilation parameters: Once the lung has been successfully opened, pInsp is reduced to the lowest possible value to ensure lung-protective ventilation. During this process, the driving pressure should be as low as possible to achieve adequate PCO2 values. For this purpose, peak inspiratory pressure and mean pressure are titrated to the lowest possible difference.
The effectiveness of the lung recruitment maneuver can be assessed using two methods:
- Blood gas analysis: An increase in the arterial partial pressure of oxygen (paO2) in the blood indicates improved oxygen uptake by the lungs.
- Pressure/volume curve: The pressure/volume curve of the lungs can provide information about whether lung capacity and compliance have increased as a result of the maneuver.
Maximum recruitment of lung units is a prerequisite for use. The recruitment potential of the patients must also be taken into account. However, it is not clear whether recruitment maneuvers reduce mortality and ventilation time in patients with ALI or ARDS, which is why they are not deemed standard procedures.
The optimal recruitment pressure, the duration and the required frequency of the maneuver are still open as well. Due to these uncertainties, it is imperative that the lung-protective ventilation procedure is carried out by well-trained specialist staff.11,12
WEINMANN l Supporting lung-protective ventilation
WEINMANN supports lung-protective ventilation, particularly in the PRVC mode, which is integrated in the MEDUMAT Standard² ventilator and MEDUVENT Standard ventilator. PRVC ventilation is a pressure-regulated, volume-controlled mode that enables gentle ventilation. For this mode, the inspiratory pressure is adjusted within one test breath such that the target tidal volume can be achieved in a pressure-controlled manner. The main advantages of PRVC ventilation are:
- The tidal volume is set exactly according to the specifications and can be preconfigured in the operator menu.
- The tidal volume is applied at the lowest possible pressure (pressure-controlled ventilation).
- The adjustable PEEP and maximum ventilation pressure (pMax).
- The option for monitoring the plateau pressure (pPlat).
At these settings, the PRVC mode enables lung-protective ventilation to be performed reliably. WEINMANN ventilators offer numerous advantages that make them indispensable in emergency responses:
MEDUVENT Standard is one of the most lightweight turbine-driven transport ventilators and emergency devices in the world. With a weight of just 2.1 kg and a volume of 3.5 liters, it can ventilate an adult for up to 7.5 hours without an external pressurized gas supply at normal ventilation settings. During the procedure, inspiratory oxygen concentrations of 21–100% can be administered. That is why this ventilator is particularly suitable for lung-protective ventilation, as the preset allows FiO2 values below 60% to be administered.
MEDUMAT Standard² is the ideal companion for emergency medical services in any situation and features numerous ventilation modes. With a weight of just 2.5 kg and a battery runtime of 10 hours, this ventilator is particularly suitable for sessions that take longer or run over long distances, for example out in the country. The device can ventilate patients from a body weight of 3 kg upwards, which is why MEDUMAT Standard² is suitable for both infant and adult ventilation.
WEINMANN ventilators are characterized by their intuitive operation. The operating symbols are clearly arranged and the devices are equipped with visual and acoustic warning signals. This ensures patient safety and that any modifications can be made if necessary. Pressure and flow curves on the ventilators enable straightforward monitoring. That way, lung-protective ventilation can be monitored to ensure that the lungs are sufficiently ventilated without being overextended. In critical situations, ventilation can be started quickly and guideline compliantly by entering the patient’s height. The device uses this variable to calculate the optimum tidal volume for lung-protective ventilation.
Lung-protective ventilation is gentle on the patient and reduces many of the risks associated with mechanical ventilation, such as volutrauma and barotrauma. WEINMANN ventilators contribute to making lung-protective ventilation effective and safe by offering compatible ventilation modes and user-friendly functions.
2 Lang, Hartmut (2020). Beatmung für Einsteiger. 3. Ed. Berlin Heidelberg: Springer-Verlag
3 Higher versus Lower Positive End-Expiratory Pressures in Patients with the Acute Respiratory Distress Syndrome | New England Journal of Medicine: https://www.nejm.org/doi/full/10.1056/NEJMoa032193
4 Breathing/ventilation Dirk Jahnke - Ventilation Settings: https://atmungbeatmung.de/index.php/beatmung/19-einstellung-der-beatmung
5 https://www.nysora.com/de/An%C3%A4sthesie/Lungenprotektive-Beatmung/
7 https://www.ai-online.info/abstracts/pdf/dacAbstracts/2009/09_Quintel.pdf
8 R. Larsen, T. Ziegenfuß (2017). Pocket Guide Beatmung. Berlin Heidelberg: Springer-Verlag
9 https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-0032-1329430
10 https://www.nysora.com/de/An%C3%A4sthesie/Lungenprotektive-Beatmung/
11 R. Larsen, T. Ziegenfuß (2017). Pocket Guide Beatmung. Berlin Heidelberg: Springer-Verlag
12 https://www.thieme-connect.com/products/ejournals/abstract/10.1055/s-2001-10470#N10944