VENTILATION DEFINITIONS

1. Minute ventilation (VE): Tidal volume multiplied by the respiratory rate (normal is 60cc/kg/min), usually expressed in liters (8-10L.min). The body regulates carbon dioxide through changes in minute ventilation. Increases in carbon dioxide leads to increased respiratory rate and/or tidal volume and increased minute ventilation (amount of air exchanged during one minute of ventilation). 1-3
2. Peak Inspiratory Pressure (PIP): The greatest pressure within the lungs during inspiration. Pressures above 35mmHg have been shown to cause pressure-related lung injury (barotrauma). Ideally, pressures should remain below 30 mmHg. Increased peak pressures are usually due to increases in resistance or decreased lung compliance within the respiratory system (e.g., kink in the circuit, mucous plugging, laryngospasm/bronchospasm, tension pneumothorax, inability for adequate exhalation, edema). 1-3
3. Plateau pressure: It is the static pressure achieved at the end of a full inspiration. To measure plateau pressure, we need to perform an inspiratory hold on the ventilator to permit the pressure to equalize through the system. Plateau pressure is a measure of alveolar pressure and lung compliance. Normal plateau pressure is below 30 cm H20, and higher pressure can generate barotrauma. Checking a plateau pressure is helpful to delineate between a resistance or compliance problem. If peak pressures are high and plateau pressures are normal, this is indicative of a resistance problem (kinked circuit, ventilator asynchrony, laryngospasm, mucous plugging, etc.). If peak and plateau pressure are high, this is more likely from compliance issues such as pneumonia, pulmonary edema, atelectasis, pneumothorax, abdominal compartment syndrome, etc.).
4. End Tidal CO2 (EtCO2 ): Measurement of carbon dioxide on end tidal expiration. Normal values are 35mmHg-45mmHg. Exhaled gasses are analyzed by either vital signs monitor or portable EtCO2 devices (e.g., EMMA) a quantitative capnograph or capnometer is the clinical standard of care with invasively ventilated patients. EtCO2 is one of the most useful measures to determine overall adequacy of ventilation. Anyone who is intubating a patient and putting them on mechanical ventilation must be able to monitor EtCO2 .
5. Arterial Blood Gas (ABG): Although continuous pulse oximetry and EtCO2 can reliably confirm adequate oxygenation, ventilation, and guide most ventilator changes – ABGs are the gold standard for evaluating acid-base status, oxygenation, ventilation and adjusting ventilation settings. If a point of care blood gas analyzer is available, this can enable targeted ventilator setting changes. Knowing these values will greatly improve critical care guidance via telemedicine resources. At facility-based care (Role 2 care and beyond) an arterial line for continuous blood pressure monitoring and ABG sampling should be placed.
6. Normal ABG values:

- pH (7.35-7.45)
- PaO2 (75-100 mmHg)
- PaCO2 (35-45 mmHg)
- HCO3 (22-26 meq/L)
- Base excess/deficit (-2 to +2)
- SaO2 (95-100%)