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PEEP Optimization using LUS in ARDS and its effects on diaphragmatic dysfunction
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PEEP Optimization using LUS in ARDS and its effects on diaphragmatic dysfunction
ARDS
Acute respiratory distress syndrome (ARDS) is a common problem among critically ill patients and is associated with high mortality and limited longterm quality of life.
Introduction
Berlin criteria for acute respiratory distress syndrome:
1. Timing: Within 1 week of a known clinical insult
2. Chest imaging a Bilateral opacity—not fully explained by effusions, lobar/lung collapse.
3. Origin of Edema Respiratory failure not fully explained by cardiac failure or fluid overload.
4. Need objective assessment (e.g., echocardiography) to exclude hydrostatic edema if no risk factor present
Severity:
Mild: P/F ratio 200-300 with PEEP 5 cmH2O
Moderate :P/F ratio 200-100 with PEEP 5 cmH2O
Severe :P/F ratio below 100 with PEEP 5 cmH2O
Etiology
sepsis, pneumonia, aspiration, trauma, multiple blood transfusions and COVID-19 are responsible for the majority of causes
Etiology
Lung protective stratigy
low tidal volume (4-6 ml/kg) ventilation to prevent tidal hyperinflation and application of PEEP to prevent atelectrauma are the main components of lung protective ventilation in patients with ARDS
Management
PEEP ??
Lower PEEP/higher FiO2.
PEEP ??
Higher PEEP/lower FiO2.
In ARDS, lung units become poorly or nonaerated due to collapse, flooding, or consolidation.
This places patients at increased risk of ventilator-induced lung injury due both to overdistention of aerated lung units and cyclic opening and closing of small airways and alveoli (atelectrauma).
WHY PEEP?
LUS score to assess areation
ECHO assessment of LV function and RV function
Assessment of diaphragmatic function
MEASURE AREATION??
Methodology
Prospective randomized controlled study was conducted on sixty patients admitted to the department of critical care medicine, faculty of medicine, Cairo University, from June 2021 to November 2022
Methodology
Inclusion criteria:
1- Fulfilling Berlin definition to confirm the criteria of ARDS
2- Stable MAP
3-Patients intubated mechanically ventilated due to progressive hypoxemia and ARDS.
Ventilation strategy targets
Ventilation strategy
for all 60 patients fulfilling the criteria were:
a- Volume control ventilation with low tidal volumes (mean tidal volumes of 6 mL per Kg of predicted body weight).
b- Plateau pressures were below 30 cm H2O.
c- FiO2 level was set to maintain accepted oxygenation (SpO2 88–95% or PaO2 60–80 mmHg).
d- Initially PEEP was set at 5cm H2O.
e- Respiratory rate was set to maintain adequate minute ventilation and to keep the arterial pH >7.25 to 7.44.
Patients were subjected to echocardiography assessment of left ventricular function by measuring cardiac output
LV,RV assessment
a- Assessment of right ventricular function using tricuspid annular plane systolic excursion (TAPSE):
b- Measuring estimated pulmonary artery pressure.
Diaphragmatic thickness assessment
Transducer placed perpendicular to the chest wall, in the eighth or ninth intercostal space, between the anterior axillary and the midaxillary lines, to observe the zone of apposition .
Diaphragmatic thickness assessment
all measures were obtained after intubation and 24 hours later
In our study population we intended to compare PEEP/ FiO2 table, that is commonly used in clinical practice and recommended by ARDSnet to LUS in detecting the best PEEP for ARDS patients
Group I , PEEP/Fio2 table
Group I
Optimum PEEP was determined using lower PEEP/ higher Fio2 combination, the oxygenation goal was a minimum of PaO2 60–80 mmHg or SpO2 88–95% as recommended by ARDS network trial.
Group II ,LUS group
PEEP was adjusted using ECHO comet score (ECS) lung ultrasound
Group II
Right side
Left side
ECS score
interstitial-alveolar syndrome
• Zero class
• Septal syndrome
• White lung
ECS score
Results
A- Primary outcome:
Relation between PEEP optimization and lung compliance in both groups.
Study outcomes
B- Secondary outcome:
1- Effect of PEEP on hemodynamics: MAP,COP,TAPSE,RVSP,inotropic support,PEEP related complications.
2- lung mechanics:
driving pressure,PEEP,autoPEEP,airway pressure,diaphragmatic thickness.
3- gas exchange:
Spo2,P/F,PaCo2.
4- clinical outcome:
duration of mechanical ventilation,length of stay,mortality.
lung compliance in both groups
Static compliance= Vt/(plateau-PEEP) DP
Despite we found significantly higher lung compliance in the LUS group after 24 hours, we could not consider it an effect of better PEEP.
Which might be related to less severe cases with better baseline compliance before PEEP optimization.
This is shown by the lack of significant delta compliance secondary to PEEP in both groups.
Compliance
and lung mechanics
We found that mean driving pressure was significantly lower in LUS group than in PEEP/Fio2 group.
Howevere ,we should emphasize that this lower driving pressure in LUS group may be due to less severe ARDS
lung mechanics
We also found that mean diaphragmatic thickness was significantly lower in PEEP/Fio2 group than in LUS group.
We found that mean PEEP was significantly lower in LUS group than in PEEP/ FiO2 table group.
We also found that mean MAP and delta mean MAP, Mean COP and delta Mean COP ,mean TAPSE and delta TAPSE, delta RVSP was significantly better in LUS group than in PEEP/FiO2 group.
hemodynamics
We also found that there was statistically significant relation between mean and delta auto PEEP in both groups after 24 hours.
We also found that there was significantlly lesser need for inotropic support and PEEP related complications in LUS group than PEEP/FiO2 group.
Our study showed that the change in SpO2 and P/F ratio was significantly better in LUS group than in PEEP/FiO2 group.
We found that the PaCO2 significantly lower in LUS group in comparison to PEEP/FiO2 group
Gas exchange
Our study showed significantly better survival in favor of LUS group which was treated with lesser PEEP in comparison to PEEP/FiO2 group
Clinical outcome
best PEEP” should simultaneously provide
1-appropriate gas-exchange .
2-keeps the lungs open (prevents phasic airway collapse) and avoids alveolar overdistension.
3-does not compromise hemodynamics.
4- carries better clinical outcome.
Conclusion
Ultrasound provide a potential enhancement for PEEP optimization in a case-by-case scenario helping intensivists to reach best PEEP targets through best lung aeration using the least PEEP requirements.