Recruitment maneuvers in ards

alveolar recruitment

1. Recruitment maneuvers in ARDS

2. Berlin definition ARDS is defined as a syndrome characterized by onset within 1 week of a known clinical insult, bilateral radiographic opacities not fully explained by pleural effusions, atelectasis, or nodules, respiratory failure not fully explained by cardiac failure or fluid overload, poor systemic oxygenation with a PaO2/FIO2 ≤300 and a PEEP or CPAP ≥5 cm H2O PaO2/FIO2 ≤300, but >200, are referred to as having mild ARDS, Moderate ARDS is defined as PaO2/FIO2 ≤200, but >100, and severe ARDS is defined as PaO2/FIO2 ≤100

3. Introduction To maintain oxygenation, FRC, and respiratory system elastance is the application of recruitment maneuvers (RMs), which have become a component of lung-protective ventilation strategies Recruitment is the dynamic process of opening previously collapsed lung units by increasing transpulmonary pressure These maneuvers expected to improve oxygenation, lung compliance, facilitate alveolar fluid clearance and outcome Lung units can be kept open by airway pressures that are lower than those required to open them, leading to the concept of recruitment using periodic higher pressure maneuvers with application of PEEP to maintain alveolar patency

4. In a normal homeostatic condition: Sigh reflex maintains lung compliance and decreases atelectasis. Alveolar recruitment maneuver is the intervention of intentional transient application of high transpulmonary pressure to achieve reopening of nonaerated collapsed peripheral airways and alveoli Mortality benefits are controversial. ART trial(alveolar recruitment for ARDS) shown these maneuvers are harmful and lead to increase mortality

5. Atelectasis results from increased interstitial pressure and weight of the lung It can be enhanced by patient related factors obesity, ↑ intraabdominal pressure, high levels of inspired oxygen in unstable alveoli, patient disconnection from the ventilator, tracheal suctioning Lung in ARDS can be reaerated by increasing transpulmonary pressure Lung recruitability has been found to be quite low, averaging 9% of total lung mass, between 5 and 45 cm of H2O

6. Recruiting the lung is a ventilatory strategy that can decrease VILI: – Increase in the aerated lung mass, which contributes to minimize the lung heterogeneity and to increase the size of lung – Prevention of repeated opening and closure of the terminal respiratory units

7. Lung pathology in ARDS is not uniform. CT chest of these patients in supine position shows three different lung areas with variable involvement. The most dorsal dependent area shows significant collapse due to interstitial and alveolar edema. this aggravates lung injury during mechanical ventilation by decreasing the size of the lung available for ventilation and gas exchange. The most ventral region is the normal open lung which gets overinflated causing volutrauma and barotrauma. The area at the interface between the normal open lung and the atelecatic lung is partially collapsed and is subjected to shear stress by cyclical tidal recruitment and derecruitment

8. Lung-Protective Mechanical Ventilation The goals of lung-protective ventilation are to avoid injury due to overexpansion of alveoli during inspiration (“ volu -trauma”) and injury due to repetitive opening and closing of alveoli during inspiration and expiration (“ atelecta -trauma”) The injury can be prevented by application of sufficient PEEP mechanical ventilation using limited tidal volumes should be less injurious to the lungs of patients with ARDS and should result in better outcomes

9. Recruitment Manoeuvres Sigh Sustained inflation Extended sigh Prone ventilation

10. Sigh Recruitment Manoeuvres Consists of high tidal volume in controlled mode or high PEEP up to a specific plateau pressure level , for a selected number of cycles Pelosi et al: 3 consecutive sighs/ minute at 45 cm H2O plateau pressure found Improvement in oxygenation, lung elastance , and functional residual capacity compared to patients who did not receive sighs Mortality benefit was not observed.

11. Sustained inflation Recruitment Manoeuvres Most widely used Recruitment Manoeuvres Ventilator is set in CPAP mode and then CPAP of 30-40 cm H20 is applied for 30-40 seconds . Grasso et al: Reported improvement in oxygenation and lung function and minimize atelectasis in experimental and clinical scenarios Also been associated with risk of hypotension and barotrauma

12. Done after ensuring SBP between 100-200 mmHg and HR between 70-140/min Ensure patient is sedated and paralyzed. If FiO2 <1.00, FiO2 to be raised to 1.00 for 5 minutes Ventilation mode to be changed to CPAP with most recent PEEP level CPAP to be increased over 10 seconds to 40 cmH2O . CPAP to be maintained at 40cmH2O for 45 seconds

13. The Recruitment Manoeuvres to be terminated immediately and CPAP returned to the most recent PEEP level if any of the following signs of distress occurs: – SBP decreases to 90 mmHg or by > 30 mmHg – HR increases to >140/min or by >20/min – SpO2 decreases by 5% and is <90% After 45 seconds at CPAP=40cm H2O,CPAP to be decreased over 5 seconds to the pre- Recruitment Manoeuvres level Most recent ventilation settings will be resumed upon completion or early termination of Recruitment Manoeuvres If 2 Recruitment Manoeuvres require early termination within a single 24 hour interval, no additional recruitment maneuvers to be attempted for atleast 12 hours

14. Stepwise Recruitment Manoeuvres Airway pressure and/or PFEP is increased for a specific time. this process gradually increases transpulmonary pressure and time for recruitment. Use stable Peak end inspiratory Pressure and incremental PEFP Use a fixed driving pressure (like 15 cm) and a stepwise increase in PEFP (25. 30. 35 cm H20) for 2minutes Apply fixed tidal volume and stepwise increases in PEEP. Since stepwise RMs recruit lung units as effectively as sustained inflation with a lower mean airway pressure, they may lead to less hemodynamic compromise and hyperinflation

15. In experimental endotoxin-induced mild ARDS, stepwise RM, compared to sustained inflation, was associated with reduced type Ⅱ epithelial cell damage and decreased expression of markers associated with fibrosis and endothelial cell damage

16. Prone ventilation Prone positioning improves gas exchange via its effect on pleural pressure and lung compression Increased functional residual capacity (FRC) has also been proposed, but changes in FRC have not been a dominant finding in most studies of prone ventilation In supine position, the dorsal pleural pressure is greater than ventral pleural pressure So , the ventral trans pulmonary pressure exceeds the dorsal transpulmonary pressure and greater expansion of the ventral alveoli than the dorsal alveoli

17. Exaggerated in supine patients with acute respiratory distress syndrome (ARDS), probably because the difference between the dorsal and ventral pleural pressures is increased by the excess lung weight The result is a tendency towards overinflation of the ventral alveoli and atelectasis of the dorsal alveoli Prone positioning reduces the difference between the dorsal and ventral pleural pressures ,Making ventilation more homogeneous Leading to a decrease in alveolar over inflation and alveolar collapse. Minimize stress and strain on alveoli, limiting ventilator associated lung injury from overdistention and cyclic atelectasis

18. Compression: In supine position: Heart compresses the medial posterior lung parenchyma and the diaphragm compresses the posterior-caudal lung parenchyma Compression by either the heart or the diaphragm may exaggerate dependent lung collapse in the supine position, increasing hypoxemia and ventilator-associated lung injury During prone ventilation, the heart becomes dependent, decreasing medial posterior lung compression The diaphragm is displaced caudally (especially in non-obese patients and when the abdomen is left unsupported), decreasing compression of the posterior-caudal lung parenchyma Improve ventilation and oxygenation

19. Cardiac output: Increase in lung recruitment and reduction in hypoxic pulmonary vasoconstriction Increases in cardiac output by Increases in right ventricular preload, and decreased right ventricular afterload

20. Predictor The best predictor of a sustained increase in PaO2 during prone ventilation is 10 mmHg increase in PaO2 over the first 30 minutes of prone ventilation predicted a sustained increase in PaO2 over the next two hours Patients whose PaO2 did not increase during the first 30 minutes of prone ventilation showed no subsequent improvement in their oxygenation

21. Patients with diffuse pulmonary edema and dependent alveolar collapse appear more likely to improve their PaO2 during prone ventilation than patients with predominantly anterior abnormalities, marked consolidation, and/or fibrosis Extrapulmonary cause for their ARDS seem more likely to increase their PaO2 during prone ventilation than patients with a pulmonary cause Patients with elevated intraabdominal pressure appear more likely to increase their PaO2 during prone ventilation than patients with normal intraabdominal pressure Patients whose chest wall compliance decreases when moving from the supine to the prone position are likely to improve their PaO2 during prone ventilation

22. Proning severe ARDS patients (PROSWA) trial has proved prone position as an important rescue measure to improve outcome in ARDS patient. In spite of the fact that a large number of studies have been published, definitive guidelines for the best method has not been recommended.

23. In hospital mortality outcome by RM

24. Alveolar recruitment for ARDS trial Multicenter RCT Conducted in 9 countries in 120 ICUs Control arm were on MV as per ARDS net protocol Intervention group received pressure control ventilation with fixed driving pressure 15cm of h20. PEEP was started from 25 to 45 each for 2 min after this patient was shifted back to MV with 5ml/kg , RR 20, flow 30l/min and fio2 100. PEEP was titrated from 23 and static compliance was measured after 4 min.

25. PEEP was decreased stepwise by 3cm and static compliance was measured at each step. Optimum PEEP was the PEEP with max compliance +2 cm of H2O. after PEEP titration new RM with 45cm of H2O PEEP was applied for 1 minute and than setting changed back to optimum PEEP

26. Recruitment stratergy group had 63.8% mortality , control group had 59.3% mortslity in hospital At 28days 55.3% and 49.3% RM can exacerbate inflammatory response by overdistension , bacterial translocation and reperfusion injury Limitation - Only 10% were on chosen for prone ventilation, malignancy and other potential diseases were not excluded.

27. Recent meta analysis including 7 RCTS concluded no improvement in mortality or length of ICU and hospital stay in ARDS

28. Recruitability Every patient of ARDS does not respond to RM. these maneuvers can overdistend aerated lung units and worsen VILI and hemodynamics. they should be used in a patient who has potential for responding to such a maneuver. Lung recruitability could provide valuable information before RM application to prevent possible deleterious effects

29. Factors potentially involved in the variability of response to RM in ARDS ARDS related - Focal vs nonfocal , Early vs late ,Severe vs moderate, Associated vasoactive drugs RM-Related Type of RMs Distribution of lung perfusion Transpulmonary pressure Timing of application Patient positioning Post-RM strategy Post-RM PEEP

30. The earlier or exudative phase of ARDS has better chance of RM success compared with a later or fibrotic phase Patients with extrapulmonary etiology of ARDS have better response to recruitment Those with diffuse changes on imaging studies have better chance of RM success than those with focal changes Patients with severe ARDS respond better to RM and the high respiratory system elastance is associated with better response to recruitment in clinical trials

31. Indications for RM ARDS / Acute Lung Injury (Patients with “secondary ARDS” ( eg from abdominal sepsis) seem to respond better than those with “primary” ARDS eg . from pneumonia) Bilateral pulmonary infiltrates PaO2/FiO2* <300 = ALI PaO2/FiO2 <200 = ARDS Atelectasis during general anaesthesia Desaturation After suctioning the ETT

32. Contraindications for RM Hemodynamic compromise: recruitment manoeuvres cause a transient loss of venous return, compromising cardiac output. Existing barotrauma Increased intracranial pressure Predisposition to barotrauma: Apical bullous lung disease Focal lung pathology eg . lobar pneumonia

33. Complications of RMs Hemodynamic compromise Barotrauma Desaturation

34. Take home message. RMs in ARDS improve oxygenation in majority of patients Routine use of RMs cannot be recommended; it should be considered for use on an individualized basis in patients with ARDS who have life threatening hypoxemia Consider ECMO in the sickest patients

35. Thank you