Peak Pressure

Peak pressure applies when there is airflow in the circuit, i.e. during inspiration. What determines the peak pressure is the airway resistance in the lungs. So it follows that if there is a problem with the airways the peak pressure will rise.

Plateau Pressure

Plateau pressure applies when there is not airflow in the circuit. That is when inspiration is complete. This pressure is determined by the lung compliance. So it follows that if there is a problem with the compliance the plateau pressure will rise.

So lets work through this diagram to help our understanding of the difference, and how it can help us interpret the information.

Peak Pressue and Plataeu pressureIf we ventilate the lung then the airway pressure will go up and the flow will increase (1).

When we release the breath, the pressure will go down, and the flow will move in the opposite direction as the air moves out (2). The flow then returns to base line (3).

Let us then say that we inflate the lungs but then hold them at inflation for a period of time. The pressure will reach a peak (4), and then as the breath hold comes in there will be an equilibrium pressure (5), (remember the balloon analogy here: it takes high pressure to inflate the balloon, but once inflated, a lot less effort to keep it inflated) until release of the pressure as exhalation takes place (6).

You can see on the flow line the period between (5) and (6) where there is no flow as the breath hold takes place.

So, remember,  peak pressure (circled) is a reflection of the airways and  plateau pressure is a reflection of lung compliance.

Remembering that important fact, lets look at a couple of examples that we might encounter.

elevated peak pressureSo firstly we can look at a wave form demonstrating a high peak pressure.
If the difference between the peak pressure and the plateau pressure is greater than 5 mm Hg then that is defined as an elevated peak pressure.

The other extreme would be where there is not a problem with the peak pressure but instead with a high plateau pressure.

So if the pressure alarm is going off you need to know whether it is a high peak pressure causing the problem or a high plateau pressure.

high plateau pressureWhy is that important?

Because a high peak pressure is an airway issue, for example:

  • Bronchospasm
  • Retained secretions
  • Mucous plug
  • ETT tip occlusion

…and a high plateau pressure is a compliance issue, for example:

  • Pneumothorax
  • Pulmonary oedema
  • ARDS
  • Pneumonia.

So understanding the difference between peak pressure and plateau pressure will help you diagnose what may be wrong with your patients ventilation.

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Intubation
6 Ways To Be Better With a BVM
Mechanical Ventilation- Physiologic Effects
Anatomy of Adult ETT
Mechanical Ventilation- Terminology
Mechanical Ventilation- Modes of Ventilation I
Mechanical Ventilation- Modes of Ventilation II
Mechanical Ventilation- Pressure/Volume/Flow Loops
Mechanical Ventilation- Peak Pressure and Plateau Pressure
PEEP (Positive End Expiratory Pressure)
Increase the rate or the tidal volume
Ventilation/Perfusion
Ventilation Screen- What do some of those numbers mean?
Phase Variables
I:E ratios and total cycle time.
Why do we ventilate?.
Volume controlled ventilation and compliance.
Lung compliance.
How do I describe how my patient is being ventilated?
Pressure/Volume loop
AC versus SIMV
A-a gradient
Pressure Support
Pressure Support Ventilation Curves
Pressure/Volume/Flow Curves

 

Originally posted 2015-03-30 05:23:57. Republished by Blog Post Promoter

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4 Responses to Mechanical Ventilation- Peak Pressure and Plateau Pressure

  1. min says:

    If the difference between the peak pressure and the plateau pressure is greater than 5 mm Hg then that is defined as an elevated peak pressure.

    The other extreme would be where there is not a problem with the peak pressure but instead with a high plateau pressure.

    ??? mmHg or CM H20 for airway pressure

  2. Dawn says:

    “min” obviously meant cmH20 in the context of this conversation. We talk about mmHg when we are dealing with blood gasses, not airway pressures. I’m sure it was a small oversight.

    “Should be less than 30” – is that all you got out of this? If so, you missed the entire point, which is that we need to distinguish between…is our patient having a Compliance issue or a Resistance issue? If we don’t comprehend that aspect, then we cannot properly care for our patient and do what is right for them, we’re simply a knob turner for the vent. We have to be able to understand each patient’s illness/disease process and how it’s affecting their entire system, especially their lungs. For example, if you have an ARDS patient or pulmonary fibrosis (stiff lungs), they’ll have low compliance/high resistance to flow and they will need a longer I-time/shorter E-time. But if you have a patient with floppy lungs, like emphysema, they’ll have the opposite – high compliance/low resistance to flow and they’ll need shorter I-time with longer E-time to allow them to get all their trapped air out. Neither will have the same pressures, you’ll think differently for the two different patients…everyone is different and you can’t just go by “black and white” rules. You have to do a little bit of thinking. It’s not as easy as just plugging in the calculations and you’re done. There is a LOT to it.

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