From the Guidelines
For patients with asthma requiring mechanical ventilation, initial ventilator settings should focus on avoiding air trapping and dynamic hyperinflation, with a recommended low tidal volume strategy of 6-8 mL/kg ideal body weight and respiratory rates of 10-14 breaths per minute, as supported by the guidelines outlined in 1. The goal of mechanical ventilation in asthma is to provide adequate oxygenation while minimizing airway pressures and the possibility of barotrauma.
- Key ventilator settings include:
- Tidal volume: 6-8 mL/kg ideal body weight
- Respiratory rate: 10-14 breaths per minute
- Inspiratory to expiratory (I:E) ratio: at least 1:3 or greater (such as 1:4 or 1:5)
- Plateau pressures: below 30 cmH2O
- PEEP: moderate, 5-8 cmH2O
- FiO2: as needed for adequate oxygenation
- Permissive hypercapnia (allowing PCO2 to rise) may be necessary, provided pH remains above 7.2, as noted in 1.
- It is essential to monitor for auto-PEEP by performing end-expiratory hold maneuvers, aiming to keep auto-PEEP below 10 cmH2O.
- Concurrent administration of bronchodilators, such as continuous albuterol, systemic corticosteroids, and consideration of magnesium sulfate for severe cases, is crucial in managing asthma exacerbations, as discussed in 1 and 1.
- Consultation with or comanagement by a physician expert in ventilator management is essential due to the complexity and risks associated with ventilation in severe asthma, as emphasized in 1.
From the Research
Ventilator Settings for Asthma Patients
The goal of mechanical ventilation for patients with acute severe asthma is to ensure adequate oxygenation, ventilation, and gas exchange while preventing hyperinflation, auto-positive end-expiratory pressure, and subsequent barotrauma 2.
Inspiratory Settings
- Tidal volume size should be limited to prevent volutrauma, with a recommended range of 4 to 8 ml/kg predicted body weight 3.
- Respiratory rate should be selected to provide adequate ventilation, with a recommended range of 20 to 35 breaths per minute 3.
Expiratory Settings
- Positive end-expiratory pressure (PEEP) should be used to prevent atelectasis, with a recommended starting point of 5 cmH2O or higher as needed 3.
- Extrinsic PEEP should be carefully managed to avoid worsening lung hyperinflation 4.
Additional Considerations
- Controlled hypoventilation with permissive hypercapnia may be used to reduce morbidity and mortality in patients with acute severe asthma 4, 5.
- Deep sedation with respiratory drive-suppressing opioids may be necessary to maintain patient-ventilator synchrony, while avoiding muscle paralysis whenever possible 4.
- Non-invasive positive pressure ventilation may be considered as an alternative to invasive mechanical ventilation in selected patients with severe asthma 6.