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Ideal Body Weight

Gender
M/F
Height
cm
PBW

{{ predictedBodyWeight }} kg

4 mL/kg {{ idealFour }} mL
6 mL/kg {{ idealSix }} mL
8 mL/kg {{ idealEight }} mL

Esophageal Catheter Positioning

In adult patients place the esophageal balloon 35-40 cm from the lips or nose. During an expiratory hold, gently push on the chest to increase the pressure in the chest. Freeze the waveforms of the esophageal and ventilator graphics. Measure the change in pressure during the push. Good positioning results in a ratio of 0.80 - 1.20

Make sure the proper unit is selected for Pes

{{ posRatio }} {{ posRatio }}

0.80-1.20


Respiratory Mechanics

Perform an expiratory hold on the ventilator for no more than 3 seconds, followed by an inspiratory hold for no more than 3 seconds. Freeze the waveforms of the esophageal and ventilator graphics. Measurements are taken at the onset of zero flow.

Make sure the proper unit is selected for Pes

{{ pdrive }} {{ pdrive }}

Driving Pressure
(RS)

{{ compCRS }}

Compliance
(RS)

{{ pLExp }}

Expiratory PL
(Directly Measured)

{{ pLInsp }}

Inspiratory PL
(Directly Measured)

{{ elastanceRatio }}

EL/ERS
(normal 0.70-0.85)

{{ elastancePlat }} {{ elastancePlat }}

Inspiratory PL
(Elastance Derived)


Ventilatory Ratio

The Ventilatory Ratio (VR) is a simple bedside index of impaired efficiency of ventilation and correlates well with physiological dead space fraction (dead space to tidal volume ratio, VD/VT) in patients with ARDS. (Reference)

Gender
M/F
Height
cm
VE
L/min
PaCO2
mmHg
PBW

{{ predictedBodyWeight }} kg

4 mL/kg {{ idealFour }} mL
6 mL/kg {{ idealSix }} mL
8 mL/kg {{ idealEight }} mL
Ventilatory Ratio

{{ ventilatoryRatio }}

{{ ventilatoryRatio }}


Lung Recruitability and Airway Opening Pressure

To test recruitability the PEEP must be changed from a higher PEEP to a lower level of PEEP (ideally by 10 cm H2O). Example: 15 cm H2O to 5 cm H2O. Addtionally, Volume Assist Control should be used. PLEASE USE A 0.3 SECOND INSPIRATORY PAUSE SETTING TO MEASURE PLATEAU PRESSURE. DO NOT PERFORM A MANUAL INSPIRATORY PAUSE. (Performing a manual inspiratory pause that is too long can often lead to erroneously low plateau pressure readings)

A test for Airway Closure should be done before this recruitability test. Please input the value into this form (instructional video for performing the test is at the end of this page).

The 'High PEEP' of the R/I ratio maneuver should be ideally AT LEAST 5 cm H2O above AOP provided Pplat is < 30 cm H2O. Continue to use a delta pressure of 10 cmH2O (even though it may cross the AOP) to be consistent with the expiratory driving pressure used in the study. (Reference)

Reduce the respiratory rate to 6-8 bpm to ensure enough time to exhale when PEEP is dropped.

Perform the following steps (see the video demonstration below):

  1. Input the exhaled volume at high PEEP with the respiratory rate set to 6-8 bpm
  2. Change to the lower PEEP ( do not do a gradual decrease), observe the exhaled volume when the PEEP changes from high to low!
  3. Look at the plateau pressure (some ventilators it would be the end-inspiratory pressure) measured by the ventilator with 0.3 second inspiratory pause setting (as shown in the video at the bottom of this page).

Note: High PEEP needs to be higher than AOP.

Airway Opening Pressure
Leave it empty if no airway closure
cm H2O
High PEEP
cm H2O
Set Tidal Volume (VT)
ml
VT exhaled @ high PEEP
ml
Low PEEP
cm H2O
VT exhaled from high to low PEEP
ml
Plateau Pressure (at low PEEP)
cm H2O

{{ recruitmentRatio }} {{ recruitmentRatio }}

Recruitment to Inflation Ratio

The value is the ratio between the compliance of the recruited lung to that of the respiratory system.
Values >= 0.5 suggest more potential for lung recruitment with respect to lung inflation. (Reference)


Diaphragm Ultrasound Thickening Fraction

Maximal thickening fraction is measured during maximal (volitional) inspiratory effort by patient. Assessing the maximum thickening fraction is particularly helpful when the thickening fraction is lower than 15% during assisted ventilation.

Assessing maximum thickening fraction

1. Remove assistance from the ventilator (PS 0 CPAP 0), or T-Piece.
2. Coach the patient to make a maximum effort while capturing the ultrasound image for measurement.

If patient is unable to follow commands due to delirium or sedative effect.

1. Explain to patient that it will be “difficult to breathe for a few seconds".
2. Apply end-expiratory occlusion on ventilator for up to 20 seconds to stimulate maximal inspiratory efforts –”Marini maneuver” (see Truwit and Marini, Chest 1992).
3. Abort occlusion if patient develops significant distress or agitation.
4. Measure maximal thickening on ultrasound from the first breath immediately after airway occlusion is released

Reference

Thickess at Expiration
Thickness at Inspiration

Diaphragm Thickening Fraction

{{ thickeningFraction }}%

This value is consistent with diaphragm disfunction

{{ thickeningFraction }}%

Normal

{{ thickeningFraction }}%

This value suggests over assistance or poor diaphragm strength (attempt Maximum Effort measurement)

{{ thickeningFraction }}%

Normal

{{ thickeningFraction }}%

This value suggests excessive effort.

Predicting High Inspiratory Effort

Using occlusion pressure (Pocc)

Steps to using the calculator

1. Input the peak airway pressure from the ventilator during tidal breathing.
2. Input the PEEP setting.
3. Perform an expiratory hold, wait until the patient makes an inspiratory effort, then freeze the ventilator waveform (or record it if using a Servo i ventilator).
4. Using the ventilator cursor, measure the baseline and peak inspiratory (lowest drop in pressure) during the occlusion.

Reference

During Tidal Breathing

Peak Airway Pressure
cm H2O
PEEP set
cm H2O

During Expiratory Hold

Baseline Pressure
cm H2O
Peak Drop (lowest pressure)
cm H2O

Pmus Predicted

{{ Pmus }} cm H2O

{{ Pmus }} cm H2O

Dynamic Transpulmonary Driving Pressure Predicted

{{ dynamicPL }} cm H2O

{{ dynamicPL }} cm H2O

Occlusion pressure (Pocc): {{ pocclusion }} cm H2O


Reference Videos

Airway Opening Pressure Servoi

Download Video

Recruitability Maneuver

Download Video

Airway Opening Pressure PB980

Download Video

Airway Opening Pressure PB840

Download Video

This calculator is ideal for education and simulation purposes. It DOES NOT replace clinical or professional judgement. Use at your own discretion.

Calculator by Thomas Piraino RRT in collaboaration with Lu Chen MD, Michele Bertoni MD and Ewan Goligher MD PhD