What is 'auto-PEEP' in mechanical ventilation?

Auto-PEEP, also known as intrinsic PEEP, refers to the condition where there is a buildup of pressure in the lungs at the end of expiration because the patient does not have enough time to exhale fully before the next inhalation starts. This can happen in patients with obstructive lung diseases or inadequate expiratory time due to various mechanical settings. When this condition occurs, it means that the positive end-expiratory pressure (PEEP) is effectively created by the dynamics of the breathing pattern, rather than being set on the ventilator. The accumulation of this pressure can lead to reduced ventilation efficiency and increased work of breathing, making it a significant consideration in ventilatory management.

The other options do not accurately represent auto-PEEP’s definition. The pressure generated during inhalation reflects the mechanics of inspiratory effort rather than the condition of auto-PEEP. An increase in tidal volume pertains to the volume of air delivered with each breath, which is unrelated to the timing of expiration that characterizes auto-PEEP. A reduction in respiratory rate might suggest improved ventilation time but does not inherently involve the concept of pressure buildup in the lungs at the end of expiration.