Respironics Inc. 1127941 User Manual
Instructions for Use | Therapy Modes and Controls
Dynamic Therapy Parameters
30
𝐷𝐷𝐷𝐷𝐷𝐷 𝐶𝐶 =
𝑉𝑉
𝑡𝑡
𝑃𝑃
𝑝𝑝𝑝𝑝𝑝𝑝𝑡𝑡
− 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
Where:
•
PEEP is the total pressure (intrinsic plus extrinsic) at the start of the breath (𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 = 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑒𝑒
+ 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑖𝑖
)
•
𝑉𝑉
𝑡𝑡
is the tidal volume
Note that the compliance is related to the airway resistance by the respiratory time constant, τ, by the relationship described above.
𝐷𝐷𝐷𝐷𝐷𝐷 𝐶𝐶 =
𝜏𝜏
𝐷𝐷𝐷𝐷𝐷𝐷 𝑅𝑅
Dyn Pplat
Plateau pressure is the pressure applied to small airways and alveoli during positive-pressure mechanical ventilation. In the Measured and
Calculated Parameters window, this value is Dyn Pplat. Having already estimated the compliance (Dyn R and Dyn C above), Trilogy Evo calculates
Dyn Pplat as follows:
𝑃𝑃
𝑝𝑝𝑝𝑝𝑝𝑝𝑡𝑡
=
𝑉𝑉
𝑡𝑡
𝐷𝐷𝐷𝐷𝐷𝐷 𝐶𝐶 + 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 + 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑖𝑖
Where:
•
𝑉𝑉
𝑡𝑡
is the tidal volume
•
𝐷𝐷𝐷𝐷𝐷𝐷 𝐶𝐶 is dynamic compliance
•
PEEP is the total pressure (intrinsic plus extrinsic) at the start of the breath (𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 = 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑒𝑒
+ 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑖𝑖
•
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑖𝑖
= −𝐷𝐷𝐷𝐷𝐷𝐷𝑅𝑅 ∗ 𝑄𝑄
𝑝𝑝
(𝑃𝑃𝐸𝐸𝑃𝑃) this value is the intrinsic PEEP or AutoPEEP
AutoPEEP
Intrinsic PEEP, 𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑖𝑖
, is the resistive pressure at the end of exhalation (EOE), that occurs when a new breath is initiated before the previous breath
is completed. In the Measured and Calculated Parameters window, this value is AutoPEEP. AutoPEEP can be used as a guide to detect the presence
of dynamic hyperinflation. In most cases, this number represents the pressure in the small airways at the start of the breath in excess of the PEEP
applied by the ventilator. In some cases, such as a ventilated, complex, COPD patient, the displayed pressure may not be accurate. However, in
these complex cases, any non-zero pressure displayed (accurate or not) indicates the presence of AutoPEEP. When Auto PEEP is zero, this
indicates that there is no intrinsic PEEP.
Trilogy Evo calculates AutoPEEP using the following formula:
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃
𝑖𝑖
= −𝐷𝐷𝐷𝐷𝐷𝐷 𝑅𝑅 ∗ 𝑄𝑄
𝑝𝑝
(𝑡𝑡 = 𝑃𝑃𝐸𝐸𝑃𝑃)
Where:
•
Dyn R is the dynamic resistance (explained in a previous section, “Dyn R” above)
•
𝑄𝑄
𝑝𝑝
(𝑡𝑡 = 𝑃𝑃𝐸𝐸𝑃𝑃) is the patient flow at the end of the exhalation (EOE)