Lung Recruitment Maneuver

Original Editor - Manisha Shrestha

Top Contributors - Manisha Shrestha, Kim Jackson and Uchechukwu Chukwuemeka  

Introduction

Recruitment generally means opening up collapsed alveoli to improve oxygenation. Lung recruitment maneuver is the maneuver in which temporary airway pressure is increased during mechanical ventilation so as to open up the collapsed alveoli and enhance alveolar unit involving in tidal ventilation to improve the oxygenation. If recruitment maneuver is combined with the administration of higher PEEP (positive end expiratory pressure) via mechanical ventilator, it is known as open lung ventilator strategy.

In the study done by Dean HR (2015), the recruitment of lungs can be done by other techniques rather than recruitment maneuver. Other techniques include the removal of mucus plug and positioning of the patient which ultimately improves the opening up of alveoli and enhances oxygenation. Therefore, methods to accomplish alveolar recruitment mentioned by Dean HR (2015) are:

• Treatment of underlying disease process: removal of airway obstruction, treatment of infection.
• Sustained inflation followed by decremental PEEP.
• Step-wise recruitment ( incremental PEEP)
• Airway pressure release ventilation
• High frequency oscillation ventilation
• Sigh
• Prone positioning

Indications

This maneuver re‐open the collapsed field of the lungs by temporarily elevating intrapulmonary pressure to levels higher than those achieved during tidal ventilation.

Advantages of Lung Recruitment Maneuver

• Increase the number of alveoli in the dependent part of the lungs participating in gas exchange.
• Increase lung compliance.
• Reduced intrapulmonary shunt improving gas exchange in pulmonary capillaries.

Disadvantages of Lung Recruitment Maneuver

• Short‐term physiological benefit.
• Increase intra-thoracic pressure compromising hemodynamic due to reduced venous return and cardiac output for a short duration.
• Hypotension and de-saturation. 
• Overdistension of alveoli.
• No significant change in the duration of mechanical ventilation, ICU stay, and hospital stay after recruitment maneuver.
• Injury to the pulmonary epithelium due to increased in intrapulmonary pressure (barotraumas) leading pneumothorax, pneumomediastinum, or subcutaneous emphysema.  

Lung recruitment Maneuver and Acute Respiratory Distress Syndrome (ARDS).

ARDS is the life threatening syndrome characterized by diffuse pulmonary inflammation,hypoxemia, and respiratory distress.

According to the American-European Consensus Conference (AECC) 1994, ARDS was defined as: the acute onset of respiratory failure, bilateral infiltrates on chest radiograph, hypoxemia as defined by a PaO2/FiO2 ratio ≤200 mmHg, and no evidence of left atrial hypertension or a pulmonary capillary pressure <18 mmHg (if measured) to rule out cardiogenic edema.

Evidence

About 14 % of COVID-19 cases are severe and 5% may require ICU support. One of the common secondary complications to COVID-19 in severe cases is ARDS.

Evidence shows that lung recruitment maneuver along with other co-intervention like higher PEEP ventilation strategy and lung protection strategy (ventilation strategies that combine low tidal volumes and relatively high respiratory rate by applying positive end expiratory pressure in relation with appropriate FiO2) has shown benefit to the patient with ARDS than recruitment maneuver alone. Even though the significance of recruitment maneuver in ARDS patient is low, WHO has chosen recruitment maneuver as a relative intervention with high continuous positive airway pressure (CPAP) (30–40 cmH2O), progressive incremental increases in PEEP with constant driving pressure, or high driving under supervised monitoring of hemodynamics and considering benefit VS risk. Recruitment maneuver should be immediately discontinued if there are any signs of no improvement in oxygenation, hypotension, or barotrauma. And stepwise recruitment maneuver is recommended rather than sustained inflation as it helps in balance recruitment against over-distension.

For more information you can go to this video

The significance of recruitment maneuver in patient with ARDS shown to be low. It may be because of the following reasons:

• In ARDS, alveoli of dependent lung field are de-recruited because it is filled with fluid from the inflammation and edema rather than collapsed.
• In ARDS, lung field is heterogeneously participating in gas exchange and an increase in alveolar pressure results in over-distention of spared alveoli which may cause barotraumas.

Prone Positioning

Prone position is the recruitment technique in which the patient is made to lie on the stomach to open up the non-aerated alveoli in a homogenous manner to improve oxygenation. WHO has suggested to place the patient with ARDS following COVID-19 in prone position for 12-16 hours in a day.

How Does it Help?

• Sponge model

Pleural pressure is the sum of all forces exerting to compress the alveolus including the weight of tissue above the alveolus and the transmitted pressure across the diaphragm from the abdomen. A decrease in pleural pressure helps in opening up the alveoli. In prone position, pleural pressure decrease in the dorsal part of lung, increasing the opening up of alveoli. This is known as Sponge model and was first described by Gattinoni et al.

• Lungs are asymmetrical in prone and supine position due to the ventral intra-thoracic structures like heart, compression of subjacent lung parenchyma and also due to displacement of abdominal content cranially toward diaphragm mainly in sedated patient due to loss of diaphragmatic tone. In prone position due to the asymmetry of lungs with more lungs field available in the dorsal part, recruiting more alveoli and thus increase ventilation. Pulmonary perfusion is relatively equal in both positions thus help in ventilation-perfusion matching and ultimately enhance oxygenation.

Complications

There are relative complications of prone positioning which can be eliminated if the procedure is done by experienced health staff. It includes:

• Airway obstruction and endotracheal tube dislodgement
• Hypotension and arrhythmias
• Loss of venous access
• Facial and airway edema
• A greater opportunity for paralysis and sedation

Contraindications

Absolute contraindication

• Recent sternotomy or abdominal incisions.
• Unstable vertebral fractures
• Significantly increased intracranial pressures

Resources

You can also visit the following pages:

• Respiratory Management of COVID 19
• efficacy-of-prone-ventilation-in-adult-patients-with-acute-respiratory-failure-a-meta-analysis

References

Original Editor - Manisha Shrestha Top Contributors - Manisha Shrestha, Kim Jackson and Uchechukwu Chukwuemeka