What is the normal inspiratory time (itime) on a ventilator (vent)?

From the Guidelines

The normal inspiratory time (I-time) on a ventilator is not explicitly stated in the provided evidence, but based on general medical knowledge, it typically ranges from 0.8 to 1.2 seconds for adult patients. This setting should be individualized based on the patient's condition, underlying pathology, and ventilation goals.

Key Considerations

• For patients with obstructive lung disease, a shorter I-time of 0.8-1.0 seconds is often preferred to allow adequate expiratory time and prevent air trapping.
• For patients with restrictive lung disease or ARDS, a slightly longer I-time of 1.0-1.2 seconds may be beneficial to improve oxygenation.
• The provided evidence 1 focuses on ventilator settings for patients with suspected or confirmed COVID-19, but does not specifically address inspiratory time.

Ventilator Settings

• The evidence suggests adjusting ventilator settings to deliver full breaths with asynchronous chest compressions, and ensuring endotracheal tube/tracheostomy and ventilator circuit continuity 1.
• It also recommends assessing the need to adjust the positive end-expiratory pressure level to balance lung volumes and venous return 1.

Clinical Decision Making

• Adjustments to I-time should be made based on patient comfort, ventilator synchrony, blood gas results, and observed chest rise and fall patterns.
• The I-time directly affects the I:E ratio (inspiratory to expiratory ratio), which is typically maintained at 1:2 to 1:3 in normal lungs, allowing sufficient time for gas exchange during inspiration while providing adequate time for passive exhalation, preventing auto-PEEP and maintaining appropriate minute ventilation.

From the Research

Normal Inspiratory Time on a Ventilator

The normal inspiratory time (itime) on a ventilator is not explicitly stated in the provided studies. However, some studies provide information on the phases of the ventilation cycle and the control parameters of the ventilator:

• The study 2 divides each ventilation cycle into four phases: the triggering phase, the inhalation phase, the switching phase, and the exhalation phase.
• The study 2 also proposes a novel fuzzy control method of the ventilator support pressure in the pressure support ventilation mode, which takes into account the trigger sensitivity and the patient's inspiratory effort.
• The study 3 discusses the importance of patient-ventilator interaction and the need to monitor asynchronies between the patient and the ventilator, but does not provide specific information on the normal inspiratory time.

Ventilator Settings

Some studies provide information on ventilator settings, but not specifically on the normal inspiratory time:

• The study 4 recommends a tidal volume of 6 ml/kg of ideal body weight and an end-inspiratory (plateau) pressure of 30 cm H2O for "protective ventilation" in patients with acute respiratory distress syndrome (ARDS).
• The study 4 also discusses the use of moderate-to-high PEEP levels to treat hypoxemia, but does not provide specific information on the normal inspiratory time.

Patient-Ventilator Interaction

The study 3 emphasizes the importance of patient-ventilator interaction and monitoring asynchronies between the patient and the ventilator, but does not provide specific information on the normal inspiratory time. Key points include:

• Patient-ventilator asynchronies are relatively frequent during mechanical ventilation in critically ill patients and are associated with poor outcomes.
• Monitoring patient-ventilator interaction is mandatory to improve the applied strategies and thus improve patient-ventilator interaction.
• The development and understanding of monitoring tools are necessary to allow a better appraisal of this area, which may lead to better outcomes for patients.