From the Guidelines
In severe COPD, the initial PEEP strategy should start with low levels, as high PEEP can exacerbate dynamic hyperinflation and worsen outcomes, with a recommended starting point of around 5 cmH2O or less, as implied by the need to avoid excessive airway pressures and allow for adequate expiratory time 1. When managing severe COPD, it's crucial to consider the patient's underlying pathophysiology, which includes air trapping and hyperinflation.
- The BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults suggests that in obstructive disease, initial settings should aim for oxygenation with a SaO2 of 88-92%, and acid-base balance with a pH of 7.2-7.4, allowing for permissive hypercapnia if inspiratory airway pressure exceeds 30 cmH2O 1.
- A key consideration in COPD management is the avoidance of dynamic hyperinflation, which can be exacerbated by high PEEP levels or inadequate expiratory times, as evidenced by the statement that in airflow obstruction, prolonging the expiratory time reduces dynamic hyperinflation (gas-trapping) 1.
- The initial PEEP setting should be individualized, taking into account the patient's specific condition, including the severity of their COPD, the presence of any comorbidities, and their response to initial ventilatory settings.
- It's also important to closely monitor the patient's respiratory mechanics, including plateau pressures, driving pressures, and auto-PEEP, and to titrate PEEP carefully based on oxygenation requirements, work of breathing, and hemodynamic stability, as excessive PEEP can lead to barotrauma or hemodynamic compromise.
- In some cases, permissive hypercapnia may be an acceptable strategy to avoid excessive ventilatory pressures, as long as the pH remains above 7.2, which is a consensus target when pH control is difficult, and is supported by the ARDS literature demonstrating that a pH above 7.2 is well tolerated 1.
From the Research
Initial PEEP Strategy in Severe COPD
- The initial PEEP strategy in severe COPD is crucial to reduce the workload for ventilation and prevent pulmonary hyperinflation 2.
- Application of low levels of PEEP can be used to reduce intrinsic positive end-expiratory pressure (PEEPi) and the magnitude of the inspiratory effort during assisted mechanical ventilation or pressure support and weaning 2.
- The use of PEEP in COPD patients requires close monitoring of the end-expiratory lung volume, which can be accomplished by inspection of flow/volume curves during application of increasing levels of PEEP 2.
- There is no specific guideline for titration of the PEEP level in COPD patients, and the optimal PEEP strategy may vary depending on the individual patient's condition 2, 3.
PEEP Setting at the Individual Level
- Setting the optimal PEEP level at the individual level is crucial to provide lung protection and prevent ventilator-induced lung injury 3.
- The open lung approach requires that every collapsed unit potentially openable is opened and maintained open, and the methods to assess the recruitment are based on imaging or mechanically-driven gas exchange modifications 3.
- Comparative studies have shown that the only possible approach to measure the amount of collapsed tissue regaining inflation is the CT scan, and higher PEEP is usually more indicated when the recruitability is higher, as occurs with increasing severity 3.
Management of Severe COPD
- The management of severe COPD involves a combination of pharmacological and non-pharmacological treatments, including inhaled bronchodilators, steroids, and antibiotics, as well as oxygen therapy, high flow nasal cannulae oxygen therapy, non-invasive mechanical ventilation, and pulmonary rehabilitation 4, 5, 6.
- Long-acting bronchodilators and inhaled corticosteroids have been shown to reduce exacerbation rates in patients with moderate to severe COPD, and domiciliary oxygen therapy has been demonstrated to prolong survival in patients with resting hypoxia 5.