Continuous, reliable measurement of static compliance of the lung and thorax is essential in mechanical ventilation. Dynamic compliance is dependent on airway resistance and can be misleading. An inflation hold maneuver measures static compliance by holding air in the lungs at the end of inspiration to measure plateau pressure. Poor compliance can indicate collapsed or overdistended lungs, while surfactant improves compliance and reduces pressure needs.
4. Ventilators deliver gas to the
lungs using positive pressure
at a certain rate.
The amount of gas delivered
can be limited by time,
pressure or volume.
The duration can be cycled by
time, pressure or flow.
Volume Change
Time
Gas Flow
Pressure Difference
8. Cdyn vs. Cstat
Measurements of respiratory mechanics during mechanical
ventilation
Continuous, reliable measurement of static compliance of
the lung and thorax is of the upmost importance in
state-of-the-art mechanical ventilation.
Dynamic compliance cannot be considered a satisfactory
substitute, as it is dependent on the airway resistance
and can be misleading in various clinical conditions.
However, Cdyn is used in mode to estimate the maximum
tidal volume allowed, which is calculated as
: Cdyn x Pmax ( Pmax = set alarm limit (Phigh)-10-PEEP).
9. . PIP Cdyn (over come airway resistance ) always
higher than plat pressure (Cstat)
. Cdyn ( resistance and alveolar diseases )
Alveolar disease only ))lower than Cstat
10. Cdyn diseases vs. Cstat diseases
.Cdyn diseases like airway obstructions
,alveolar disease like atelectasis ,
pneumonia, pneumothorax
.Cstat diseases like Alveolar ( atelectasis ,
pneumonia )
11.
12. Inflation hold or inspiratory pause
hold air in the lung at end of inspiration (P plateau)
to measure Cstat
15. Clinical Implications (cont.)
Role of Surfactant
Improves compliance
Results in a rapid decline in pressures required
to deliver the tidal volumes after surfactant
administration
16. Lets try this
3kg neonate, tidal volume delivered- 14ml,
pressure required to drive this volume is PIP of
18 and PEEP of 4
Calculate compliance=??
18. Clinical Implications (cont.)
. Collapsed/ overstretched lungs --- poor
compliance
. PEEP--- Pressure required to open the
lungs and keep it inflated
. High PIP (excess pressure) which over
distends the lungs, does not result in
better volume deliver
19.
20.
21. Who’s Watching the Patient?
Pierson, IN: Tobin, Principles and Practice of Critical Care Monitoring
22. Key points
. Elastic properties of lung & chest wall
. Continuous, reliable measurement of static compliance .
. Inhalation hold or inspiratory pause test give you clue
about what is maximum pressure (Plateau ) needed
..Collapsed/ overstretched lungs --- poor compliance
Notes de l'éditeur
Reverse relationship between C- P , high Pressure lead to low compliance verse versa
Dynamic compliance represent s pul. compliance during gas flow such as active inspiration ( during inspiration & expiration )
If P Plat higher than PIP baby may be active breath out while the P plat. Is being measured lead to in correct measurement .
و أنا محتاج التمدد الثابت للرئة ليه عشان اعرف هي محتاج قد إيه ضغط عشان يكون ناسب لها We need plateau pressure to measure the static compliance
قانون نيو تين كل فعل له رد فعل مساوي له في المقدار ومضاد له في الاتجاه والهواء دخل في نهاية الشهيق الضغط ده اللي جوه هو بلاتوه اللي عايز يقاس measurement maximum plateau pressure 30 cmh2o we need to improve c stat