From the Guidelines
Late cycle ventilation, also known as late expiratory phase ventilation, refers to the delivery of positive pressure throughout expiration, which helps to flush exhaled CO2 from the mask and distal ventilator tubing, aids triggering, and counteracts the tendency for upper airway collapse during expiration. This technique is particularly relevant in the context of non-invasive ventilation (NIV) and is achieved through the use of pressure-targeted ventilation modes, such as those employing a single lumen circuit with an integral exhalation port or an exhalation port inserted into the ventilator circuit close to the mask 1. The use of a minimum EPAP of 3 cm is required to effectively vent the system and prevent CO2 rebreathing.
Key Considerations
- The choice of interface for NIV, such as a full-face mask (FFM), is crucial to accommodate mouth breathing and the natural diversity of the human face.
- Pressure-targeted ventilation offers several advantages, including constant pressure delivery, compensation for air leak, and the ability to flush exhaled CO2 from the ventilator circuit.
- The mode of ventilation, whether spontaneous (S) or timed (T), should be selected based on the patient's inspiratory effort and the need for ventilator support.
Clinical Implications
- Late cycle ventilation can help improve gas exchange and reduce the risk of ventilator-associated lung injury by better matching ventilation with perfusion in heterogeneously affected lungs.
- The technique may be particularly beneficial in patients with obstructive lung diseases, such as COPD or asthma, where air trapping is common.
- The exact parameters for implementing late cycle ventilation would need to be tailored to individual patient needs based on their lung mechanics and underlying pathology, as outlined in guidelines such as the BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults 1.
From the Research
Definition of Late Cycle Ventilation
Late cycle ventilation, also known as late expiratory phase ventilation, refers to the phase of mechanical ventilation where the ventilator terminates inspiration and begins expiration later than the patient's neural timing.
Causes and Effects
- Patient-ventilator asynchrony may occur if the flow at which the ventilator cycles to exhalation does not coincide with the termination of neural inspiration 2.
- Delayed cycling can lead to increased work of breathing and discomfort for the patient 3.
- The proper adjustment of the breath termination criterion (TC) can improve patient-ventilator synchrony and decrease the work of breathing during pressure support ventilation 3.
Types of Dyssynchrony
- Seven forms of dyssynchrony are common, including ineffective triggering, autotriggering, inadequate flow, too much flow, premature cycling, delayed cycling, and peak pressure apnoea 4.
- Delayed cycling is a type of dyssynchrony that can occur when the ventilator terminates inspiration later than the patient's neural timing 4.
Ventilator Settings and Modes
- Adjustable cycling features and waveform graphics can enhance patient-ventilator synchrony 2.
- Different ventilation modes, such as pressure assist-control ventilation and volume assist-control ventilation, can affect patient-ventilator synchrony and breathing effort 5, 6.
- The use of proportional assist ventilation (PAV) can improve patient-ventilator synchrony and reduce the work of breathing compared to pressure support ventilation (PSV) 6.