Understanding Plateau Pressure
Plateau pressure refers to the pressure within the small air sacs of the lungs, known as alveoli, at the very end of an inhaled breath when airflow has momentarily ceased. This measurement provides a direct indication of how distended the lung tissue itself is. Healthcare professionals use this measurement to assess a patient’s lung condition and guide adjustments to ventilator settings. Maintaining appropriate plateau pressure helps prevent potential lung damage.
This measurement differs from peak inspiratory pressure, which includes resistance encountered as air flows through ventilator tubing and larger airways. By contrast, plateau pressure specifically isolates the pressure exerted on delicate lung tissue, making it a more accurate gauge of potential lung overstretching. To obtain this reading, an inspiratory hold maneuver is performed on the mechanical ventilator, allowing airflow to momentarily stop.
What is a Normal Plateau Pressure?
A normal plateau pressure is generally considered to be less than 30 centimeters of water (cm H2O). This specific threshold is widely accepted in clinical practice as a safe upper limit for mechanically ventilated patients. Keeping the plateau pressure below this value is important because exceeding it significantly increases the risk of ventilator-induced lung injury (VILI).
When plateau pressure rises above 30 cm H2O, it indicates that the lung tissue is being overstretched, which can damage the delicate structures of the alveoli. This overstretching can lead to inflammation, fluid accumulation, and impaired gas exchange within the lungs. While this 30 cm H2O guideline serves as a general upper limit, slight variations may exist based on individual patient characteristics.
Factors Influencing Plateau Pressure Readings
Several factors can cause plateau pressure readings to deviate from the normal range. One primary cause of increased plateau pressure is reduced lung compliance, meaning the lungs have become stiffer and are less able to expand easily. Conditions such as Acute Respiratory Distress Syndrome (ARDS), pulmonary fibrosis, and severe pneumonia can significantly decrease lung compliance, requiring higher pressures to inflate the lungs. Fluid overload, which can lead to pulmonary edema, also stiffens lung tissue and contributes to elevated plateau pressures.
Incorrect ventilator settings, particularly the delivery of excessively large tidal volumes (the amount of air delivered with each breath), can also directly elevate plateau pressure. When too much air is pushed into the lungs, it increases the pressure within the alveoli. External pressures on the chest cavity, such as severe abdominal distension or stiffness of the chest wall, can also restrict lung expansion and increase the pressure required to ventilate the lungs. Conversely, very low tidal volumes or an improvement in lung compliance can lead to a decrease in plateau pressure.
Why Maintaining Normal Plateau Pressure is Important
Maintaining plateau pressure within the normal range is important for preventing serious complications in mechanically ventilated patients. Consistently high plateau pressure increases the risk of ventilator-induced lung injury (VILI). VILI can lead to further lung damage, prolong a patient’s need for mechanical ventilation, and worsen overall patient outcomes.
Healthcare providers monitor plateau pressure measurements to make informed adjustments to ventilator settings. For instance, if plateau pressure is too high, the medical team might reduce the tidal volume delivered by the ventilator. This careful management helps to protect the patient’s delicate lung tissue and optimize ventilation, contributing to a safer recovery.