display and functions Rosemary Salazar RRT, Eva Nourbakhsh MD

compliance (“stiff lung”) plateau pressure; compliance plateau pressure.

High plateau pressure increases the risk of barotrauma.

Low plateau pressure can result in atelectasis and hypoventilation.

Plateau pressure should not exceed 30 cm H₂O.

For example, patients with ARDS, pulmonary fibrosis, or abdominal distension will have

plateau pressure.

Mean airway pressure (Pmean) is the average pressure throughout the ventilatory cycle.

This incorporates all pressures to which the lungs are exposed during the respiratory cycle.
The mean airway pressure will increase if the PEEP is increased.
Trends in Pmean may provide useful information.
Monitored in patients on APRV or high frequency ventilation.
in ARDS; in emphysema.

Positive end-expiratory pressure (PEEP) is externally applied pressure that maintains a positive airway pressure throughout expiration

Please refer to PEEP chapter (9)

Inspiratory time (Ti) is the time between the start of inspiration and the start of exhalation.

Longer inspiratory time is associated with improved oxygenation but increases the risk of auto-PEEP.

Expiratory time (Te) is the time between the start of expiration and the start of inspiration.

I: E ratio is the ratio between inspiratory time and expiratory time.

Usual ratio is 1:2 to 1:3

Minute volume () is the amount of gas moved in and out of the respiratory system in one minute

Tidal volume multiplied by respiratory rate.
The higher the the more CO₂ is excreted.
The normal is 5–8 L/min.
may reflect inefficient gas exchange or hyperventilation.
may cause hypoxemia or hypercapnia.
For example, patients with ARDS often have an increased E.

Inspiratory minute volume (MV_IN) is the volume delivered in one minute during inspiration.

This number is patient dependent on some modes of ventilation.

Expiratory minute volume (MV_EX) is the exhaled volume in one minute.

MV_IN and MV_EX should be the same.
Please refer to troubleshooting chapter.

Inspiratory tidal volume (V_TI) is the tidal volume during inspiration.

A small V_T can result in hypoxemia, atelectasis, or hypoventilation.
A large V_T can result in hyperventilation, volutrauma, or low CO₂.

Expiratory tidal volume (V_TE) is the tidal volume during exhalation.

V_TI and V_TE should be the same.
Please refer to troubleshooting chapter (23).

Cuff Pressures

• Endotracheal tubes (ETT) have a cuff to seal the airway. The pressure used to inflate the cuff can be measured with a manometer.

• The cuff pressure should be kept < 20 mmHg. The cuff pressure should not exceed 25 mmHg; this should limit pressure induced necrosis.

• High cuff pressures cause physical trauma to the trachea and/or impede blood flow to the tracheal mucosa.

• Measured once a shift by RT.

Lung compliance is the measurement of the distensibility of the lung.

• Static compliance measures the elastic properties of the lung.

static compliance may be due to pleural or chest wall disorders.

• Dynamic compliance measures both elastic and resistive forces.

dynamic compliance may be due to resistance, such as with excessive secretions, bronchospasm, occlusion of ETT, or a kink in tubing.

• in both dynamic and the static compliance may be caused by atelectasis, pneumothorax, pulmonary edema, ARDS, mainstem intubation, or worsening of the underlying disorder.