PEEP in Ventilation
Ventilation with positive end-expiratory pressure (PEEP) is directly linked to functional residual capacity (FRC), the lung volume remaining following normal expiration. In healthy patients, FRC is around 2,000 to 2,400 ml, generating a physiological PEEP of 1 to 2 mbar. This intrapulmonary pressure keeps the alveoli and airway open and allows gas exchange during the expiration phase. The advance expansion of the lung due to PEEP also facilitates subsequent inspiration.
In patients receiving invasive ventilation, FRC may be reduced due to the endotracheal tube or tracheal cannula, leading to suboptimal ventilation of the lungs. Patient position also affects FRC: When the patient is supine, the diaphragm may be displaced upwards, reducing the space for the lungs to expand, especially when individuals are relaxed. In addition, gravity leads to an uneven distribution of blood in the lungs; this may promote both peripheral airway collapse and pulmonary shunt. PEEP is adjusted during ventilation to counteract these problems. This increases FRC, improving gas exchange in the lungs and preventing alveolar collapse and atelectases.1
Read this article to find out more about ventilation with PEEP – from the definition, to the correct setting to the advantages and disadvantages. We also introduce the WEINMANN ventilators you can use to perform ventilation with PEEP reliably.2
PEEP and ventilation: Definition
PEEP (short for positive end-expiratory pressure) is the positive pressure maintained in the lung at the end of expiration. It is above normal atmospheric pressure and represents the lowest pressure value in the ventilation cycle.
PEEP is used in the context of mechanical ventilation to simulate the physiological mechanisms of breathing. During spontaneous breathing, closure of the glottis at the end of expiration generates a pressure of 1-2 mbar in the lungs.3
Ventilation with PEEP may improve oxygenation by stabilizing alveoli and airway and preventing atelectases. Increasing functional residual capacity (FRC) continues gas exchange during expiration as well, allowing ventilation to be secured.
Extrinsic PEEP
Extrinsic PEEP is the artificially-generated PEEP generated and electronically adjusted by a ventilator. On a bag-valve mask, PEEP can be adjusted with the aid of an external mechanical PEEP valve.
Intrinsic PEEP
Intrinsic PEEP – also called auto-PEEP – is not caused or adjusted by ventilation, but occurs in patients with airway obstructions. In these cases, expiratory time is insufficient for complete pressure compensation, with the result that there is still air in the lungs prior to the next inspiration.
It affects patients with diseases that obstruct the air flow or constrict the airway – like asthma or COPD. They have difficulty with expiration, as the airway can collapse. For these patients, expiration is associated with effort, so to counteract this sensation, they often breathe in again prematurely. This mechanism contributes to a permanently elevated air pressure in the lungs.4
Standard PEEP values
Most modern ventilators allow PEEP value settings between 0 mbar and 35 mbar. The optimal PEEP value for ventilation varies depending on the situation and on the condition of the patient.
The international ARDS Network recommends setting PEEP as a function of the oxygen concentration (FiO2) required. An increased requirement for oxygen indicates an oxygenation disorder which is often accompanied by alveolar collapse. A higher PEEP may be required in such cases to recruit more alveoli and to improve gas exchange.
The following table shows the PEEP values recommended as a function of the quantity of oxygen administered; this is based on the ARDS Network guidelines: 5
- Value
FiO2: 30
PEEP: 5
- Value
FiO2:40
PEEP: 5-8
- Value
FiO2: 50
PEEP: 8-10
- Value
FiO2: 60
PEEP: 10
- Value
FiO2: 70
PEEP: 10-14
- Value
FiO2: 80
PEEP: 14
- Value
FiO2: 90
PEEP: 14-18
- Value
FiO2: 100
PEEP: 18-24
Indication for ventilation with PEEP
PEEP should essentially be used for any invasive and non-invasive ventilation in order to counteract a drop in functional residual capacity – so the use of PEEP ventilation is standard in intensive care medicine. A PEEP of 5 mbar is generally sufficient in this case.
Even patients with oxygenation dysfunction or restrictive lung diseases benefit from ventilation with PEEP. In these cases, PEEP can improve both FRC and respiratory compliance. Examples of such diseases are:6
- Non-cardiogenic and cardiogenic pulmonary edema
- Acute lung failure (ARDS)
- Pneumonia
Contraindication
Ventilation with PEEP may be contraindicated in patients with diseases of the respiratory tract which may lead to intrinsic PEEP. This particularly applies to patients with COPD or asthma. However, as long as PEEP is lower than auto-PEEP, it may still contribute to keeping the minor airways open when ventilating COPD patients. The use of PEEP ventilation is thus disputed in COPD.6
Benefits and risks of ventilation with PEEP
Ventilation with PEEP is indispensable in modern intensive care and emergency medicine. However, it can also involve potential risks, depending on the level of PEEP setting. This table shows the key advantages and disadvantages in relation to ventilation with PEEP.
Advantages
PEEP reduces the risk of alveolar collapse and atelectases by guaranteeing the stability of the alveoli and contributing to reopening areas of the lung already suffering from atelectasis.
In addition, PEEP helps keep shunt volume steady during ventilation, achieving improved oxygenation.
PEEP also increases functional residual capacity with the result that more air remains in the lungs after expiration, supporting gas exchange. Advance expansion of the airway reduces airway resistance and facilitates the work of breathing.7
Ventilation with PEEP can also contribute to preventing pulmonary edema. In pulmonary edema, fluid accumulates in the lungs, impairing gas exchange. PEEP promotes the transfer of this fluid away from the alveoli and into the interstitium, the space between the alveoli and the blood vessels.8
Risks
Selection of the optimal PEEP value is a key challenge in ventilation. Too low a PEEP may lead to alveolar collapse during expiration. If the alveoli are recruited again on inspiration, there is a risk of ventilation-induced lung injury. Too high a PEEP, on the other hand, may overinflate the lungs.
Elevated PEEP may furthermore increase pressure in the thorax, putting the cardiovascular system under strain. A rise in intrathoracic pressure may lead to a drop in cardiac output and blood pressure, which in turn may impair perfusion and consequently the function of organs such as the kidneys.9
PEEP in manual and mechanical ventilation
In manual ventilation, PEEP is regulated by a mechanical valve with an integrated spring connected to the bag-valve mask, a so-called PEEP valve. The valve opens and closes depending on the pressure ratio between air pressure upstream of the valve and spring pressure.
Manual PEEP valves permit ventilation with PEEP even when a ventilator is not being used; this can be especially valuable in situations with limited resources. However, the PEEP setting is less precise on manual valves than on mechanical ventilators and therefore requires experience of handling.10
In mechanical ventilation, PEEP is controlled electronically by the ventilator. The PEEP valve is integrated in the device and it is possible to make highly detailed settings and measure the pressure level continuously.11 This maintains a predefined positive pressure during expiratory time, achieving greater accuracy with the benefit of no additional accessory being required.
Ventilation with PEEP in WEINMANN ventilators
PEEP is a fixed component of virtually every form of mechanical ventilation – including in the sphere of emergency medicine. WEINMANN ventilators give you the option of setting PEEP in both pressure-controlled and volume-controlled modes, including PCV, aPCV, BiLevel + ASB, IPPV, S-IPPV, SIMV and SIMV + ASB. The setting process is simple and clear.
With the MEDUMAT Standard² and MEDUVENT Standard ventilators, you get reliable ventilation in every situation:
- MEDUMAT Standard²: Our versatile ventilator with a battery runtime of 10 hours is suitable for any patient weighing 3 kg or above. This makes MEDUMAT Standard² the perfect companion for a wide range of scenarios, especially for extended sessions.
- MEDUVENT Standard: The device is one of the lightest turbine-driven emergency ventilators in the world and has a battery runtime of up to 7.5 hours. It allows ventilation at oxygen concentrations of 21-100 % without any kind of external compressed gas supply.
Both ventilators feature intuitive handling and extensive alarm functions. Night mode means that they can also be used in the dark. In addition to PEEP, you can set numerous other parameters to adapt ventilation to suit your individual patient. The monitoring delivered by the pressure and flow curves gives you an overview of all the parameters and the current state of your patient.
2 Larsen, R.; Mathes, A. (2023): Beatmung. Indikation – Techniken – Krankheitsbilder [Ventilation. Indications - Techniques - Clinical Pictures]. 7th edition Berlin, Heidelberg: Springer-Verlag, p. 122.
3 https://flexikon.doccheck.com/de/PEEP
4 Lang, Hartmut (2020), Beatmung für Einsteiger, Theorie und Praxis für die Gesundheits- und Krankenpflege [Ventilation for beginners, theory and practice for healthcare]. Berlin, Heidelberg: Springer-Verlag, p. 152.
5 Lang, Hartmut (2020), Beatmung für Einsteiger, Theorie und Praxis für die Gesundheits- und Krankenpflege [Ventilation for beginners, theory and practice for healthcare]. Berlin, Heidelberg: Springer-Verlag, p. 100, 281.
6 Larsen, R.; Mathes, A. (2023): Beatmung. Indikation – Techniken – Krankheitsbilder [Ventilation. Indications - Techniques - Clinical Pictures]. 7th edition Berlin, Heidelberg: Springer-Verlag, p. 284f.
7 Hartmut Lang (2017): Außerklinische Beatmung. Basisqualifikationen für die Pflege heimbeatmeter Menschen [Out-of-hospital ventilation. Basic qualifications for nursing home-ventilated patients]. Berlin, Heidelberg: Springer-Verlag, p. 120-131.
8 Lang, Hartmut (2020), Beatmung für Einsteiger, Theorie und Praxis für die Gesundheits- und Krankenpflege [Ventilation for beginners, theory and practice for healthcare]. Berlin, Heidelberg: Springer-Verlag, p. 99.
9 Hartmut Lang (2017): Außerklinische Beatmung. Basisqualifikationen für die Pflege heimbeatmeter Menschen [Out-of-hospital ventilation. Basic qualifications for nursing home-ventilated patients]. Berlin, Heidelberg: Springer-Verlag, p. 121f.