Pressure-Controlled Ventilation (PCV)
Ventilation in the PCV mode represents a therapeutic option in intensive care and emergency medicine that reliably supports patients who lack spontaneous breathing capacity. The PCV mode maintains constant pressure in the airways to ensure deliver of an adequate oxygen supply. PCV is used particularly in patients with respiratory insufficiency when their lungs can no longer perform their function independently. For that reason, PCV represents a life-saving measure that enables effective ventilation and can support patients in frightening situations.
In this article, you will learn how PCV is defined, what advantages it offers and which WEINMANN ventilators support this form of ventilation.
Definition: What is pressure-controlled ventilation (PCV)?
Pressure-controlled ventilation (PCV) is mechanical ventilation during which the pressure is controlled: and works by means of an adjustable inspiratory pressure (pInsp). In the PCV mode, a positive end-expiratory pressure (PEEP) can be set to prevent alveolar collapse and keep the airways open.
Due to the preset ventilation pressure, the tidal volume varies during PCV ventilation as a function of respiratory system compliance and the patient’s airway resistance.1,2
How PCV works
For PCV, PEEP, the inspiratory pressure (pInsp) and the mandatory ventilation frequency are preset initially. The ventilator then generates positive pressure, which increases the transpulmonary pressure. This causes the respiratory gas to flow into the lungs along the pressure gradient. As a function of resistance and compliance, a certain tidal volume and a decelerating flow is achieved.3 Decelerating means that the flow speed is initially high and then decreases.
The ventilator supplies a sufficient amount of air until the preset inspiratory pressure is reached. The aim is to ensure adequate ventilation. In general, the air is delivered with a ramp of around 0.2 seconds such that the peak flow is reached somewhat later.4 As soon as the preset air pressure is reached, this level is maintained for the entire inspiration time.
The inspiratory-expiratory ratio (I:E) is defined as the ratio of time expended on inspiration versus that expended on expiration. At the end of the inspiratory time, the administered air is lowered back to the PEEP level via the expiratory valve. Afterwards, the expiratory phase begins and then a new ventilation cycle starts.2
Indications
PCV is a controlled form of ventilation intended for use in patients who lack spontaneous breathing. It can be used for ventilation in respiratory insufficiency, such as acute respiratory distress syndrome (ARDS)3 or chronic obstructive pulmonary disease (COPD).5
Ventilation in the PCV mode can also support patients with reduced respiratory system compliance in the work of breathing. In diseased lungs, distensibility is often reduced, which leads to a reduced tidal volume. A careful increase in pInsp can counteract this state.2
Ventilation in the PCV mode is also used in infants and small children and, in some cases, can also be administered non-invasively via a mask.6 Furthermore, the PCV mode is used for the ventilation of quadriplegics or individuals with neuromuscular diseases.2 These conditions weaken the respiratory muscles and can cause complete respiratory insufficiency.7 The versatility of ventilation in the PCV mode makes it an important method in modern intensive care and emergency medicine.
Advantages of ventilation in the PCV mode
Ventilation in the PCV mode offers numerous advantages for patients in intensive care. Pressure-controlled ventilation protects the lungs by limiting the maximum pressure during inspiration. This prevents critical pressure values from being exceeded, thereby minimizing the risk of overexpansion of the lungs and ventilator-induced lung injury like barotrauma.7
In addition, ventilation in the PCV mode tends to be better tolerated than volume-controlled ventilation (VCV). The reason for this is mainly due to the constant airway pressure and the ability to adjust the airflow to the patient’s individual needs. This constant airway pressure improves lung compliance, optimizes dead space ventilation and heightens patient comfort.8
Moreover, the continuous pressure level and the decelerating flow can promote the opening of the alveoli, which is particularly advantageous compared to constant-flow ventilation in the VCV mode. Ventilation in the PCV mode is also able to maintain the pressure level and ventilation within certain limits despite leaks in the system such as in the ventilation hose.7
In the PCV mode, ventilation can optionally take place at the PEEP setting. Alternatively, zero end-expiratory pressure (ZEEP) can be set, although PEEP is preferred in most intensive care situations due to its advantages.
Disadvantages of ventilation in the PCV mode
In addition to its advantages, ventilation in the PCV mode can also have disadvantages. Since the tidal volume depends on the patient’s compliance and resistance, impedance fluctuations can lead to volume changes. Impedance is defined as the resistance of the airways and lungs to inflowing gas.
With increased compliance, the tidal volume increases, which increases the danger of hyperventilation and respiratory alkalosis. Overexpansion of the lungs is another conceivable consequence.
By contrast, reduced compliance can lead to hypoventilation with hypercapnia resulting in respiratory acidosis. To minimize these risks, ventilation parameters should always be carefully monitored during ventilation in the PCV mode.9
Difference between ventilation in PCV and aPCV modes
Although similar to the ventilation in the pressure-controlled ventilation (PCV) mode, aPCV is an assisted mode. On ventilation in the aPCV mode, patients can breathe spontaneously during expiration within a certain time window. This spontaneous breathing initiates a trigger that synchronizes the patient’s own efforts to breath with a mechanical breath.
By taking spontaneous breathing into account during aPCV, the ventilation frequency and thereby the minute volume can be influenced by the patient’s respiratory activity.10 During ventilation in the PCV mode, by contrast, the minute volume remains constant and depends solely on the patient’s compliance and airway resistance. The differences between the two modes are clearly illustrated in the following table.
PCV: Pressure-controlled ventilation
- Control type
Pressure-controlled
- Operating mode
Controlled
- Application
No spontaneous breathing
- Pressure limit
Fixed pressure limit through pressure control
- Volume delivery
Constant, depending on respiratory system compliance and resistance
aPCV: Assisted pressure-controlled ventilation
- Control type
Pressure-controlled
- Operating mode
Assisted
- Application
Partial spontaneous breathing, but also possible without spontaneous breathing
- Pressure limit
Fixed pressure limit through pressure control
- Volume delivery
Adaptive, depending on the patient’s spontaneous breathing, compliance of the respiratory system and resistance
Setting the parameters
In order to minimize risks and ensure guideline-compliant ventilation, PCV can be optimally adapted to the patient’s individual needs by setting the parameters. The adjustable ventilation parameters include:
- Inspiratory pressure (pInsp) in mbar: This value describes the ventilation pressure that should be achieved during inspiration.
- Ventilation frequency (Freq.) in 1/min: Respiratory rate indicates how often a breath is taken per minute.
- Positive end-expiratory pressure (PEEP) in mbar: This pressure keeps the alveoli open at the end of exhalation and improves gas exchange.
- Maximum inspiratory pressure (pMax) in mbar: This value limits the maximum achievable pressure during inhalation, thereby protecting the lungs from excessive pressure.
- Inspiratory-expiratory ratio (I:E): This ratio defines the time of inhalation versus exhalation.
PCV mode in WEINMANN ventilators
PCV is available as an optional ventilation mode on the MEDUMAT Standard² ventilator and the MEDUVENT Standard ventilator from WEINMANN.
MEDUVENT Standard is one of the lightest transport and emergency ventilators in the world, weighing only 2.1 kg. Despite its compact size, the device can ventilate adults with a volume of 3.5 liters for up to 7.5 hours at typical ventilation settings – without using up the patient’s own oxygen reserves. The inspiratory oxygen concentration (FiO) can be set from 21% to 100%. Depending on a blood gas analysis (BGA), the necessary oxygen content should be kept as low as possible to avoid lung damage caused by free oxygen radicals.
MEDUMAT Standard² is a versatile and reliable companion in any deployment situation. With a battery runtime of 10 hours, the device is particularly suitable for longer sessions. Thanks to its low weight of just 2.5 kg, it is particularly easy to handle and space-saving. This makes MEDUMAT Standard² the ideal partner for use on location, during transportation or clinical settings. The ventilator is suitable for patients weighing upwards from 3 kg, which means it can be employed flexibly regardless of age and weight.
WEINMANN ventilators are additionally characterized by their intuitive operation and high level of patient safety. In critical situations, ventilation can be started quickly and guideline compliantly by entering the patient’s height. This saves valuable time during first aid, which can improve patient outcomes. The clearly arranged controls enable the time-saving and effective use while visual and acoustic warning signals warn of potential dangers. A hygiene filter prevents contamination and protects the device, staff and patients. In addition, a night view ensures that the device displays can be read easily, even in the dark.
WEINMANN ventilators are your reliable companions for emergency medical services. They support PCV in patients who are lacking spontaneous breathing while ensuring adequate ventilation and oxygenation.
1 https://www.amboss.com/de/wissen/maschinelle-beatmung/
2 Hartmut Lang (2017): Außerklinische Beatmung. Basisqualifikationen für die Pflege heimbeatmeter Menschen. Berlin Heidelberg: Springer-Verlag, p. 120-131.
3 Larsen R, Ziegenfuß T (2013). Beatmung. 5th Edition, Berlin-Heidelberg: Springer-Verlag, p. 205.
5 https://register.awmf.org/assets/guidelines/001-021k_S3_Invasive_Beatmung_2017-12.pdf
7 R. Larsen, T. Ziegenfuß (2017). Pocket Guide Beatmung. Berlin Heidelberg: Springer-Verlag, p. 54.
8 https://www.ncbi.nlm.nih.gov/books/NBK555897/
9 R. Larsen, T. Ziegenfuß (2017). Pocket Guide Beatmung. Berlin Heidelberg: Springer-Verlag, p. 55.
10 https://www.weinmann-emergency.com/de/themen/notfallbeatmung/druckkontrollierte-beatmung