Bronchoscopic suctioning may cause lung collapse: a lung model and clinical evaluation

Area of Science:

• Critical Care Medicine
• Respiratory Physiology
• Pulmonary Engineering

Background:

• Bronchoscopic suctioning is a common procedure in mechanically ventilated patients.
• Maintaining lung volume and stability is crucial for patients with acute lung injury (ALI).
• The impact of suctioning on lung volumes during different ventilation modes is not fully understood.

Purpose of the Study:

• To evaluate changes in lung volume during and after bronchoscopic suctioning.
• To compare these changes under volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV).
• To assess the adequacy of ventilator support during suctioning in ALI patients.

Main Methods:

• Bench testing using a lung model and a patient study involving 13 ALI patients.
• Bronchoscopic suctioning performed with 12 or 16 Fr bronchoscopes.
• Measurements included suction flow, airway pressure, functional residual capacity (FRC), and ventilation using electric impedance tomography (EIT).

Main Results:

• Suction flow rates ranged from 5 to 17 L/min at vacuum levels of -20 to -80 kPa.
• Pronounced lung derecruitment occurred during suctioning, with a significant decrease in FRC (-479 ± 472 ml).
• Ventilators could not compensate for volume loss, leading to decreased tracheal pressure.

Conclusions:

• Suction-induced airflow exceeds minute ventilation in many ALI patients.
• Current ventilator strategies (VCV and PCV) are insufficient to maintain FRC during suctioning.
• Tracheal pressure drops below atmospheric pressure, indicating potential for lung injury.