**Prof Marcelo Alcantara Holanda**

-Associate Prof. of Medicine, Federal University of Ceará, Brazil

-Idealizer and founder of the Xlung Platform

Click here to see in table form

Ideal or predicted body weight (IBW or PBW), kg

Gender: Male

Equations: 50 + 0,91 * (Height - 152,4 cm).

Comments/recommendations: VT: 6 to 8ml of IBW in general.

Gender: Female

Equations: 45, 5 + 0,91 * (Height - 152,4 cm).

Comments/recommendations: VC < 6 ml/kg - ARDS.

Respiratory mechanics and related variables

**Variable: Peak airway pressure**

Equations: None

Comments/recommendations:

- Maximum airway pressure

- Keep below 35-45 cmH2O>

**Variable: Plateau pressure**

Equations: None

Comments/recommendations:

- Alveolar pressure at end inspiration during a pause of 2 s

- Keep below 15 cmH2O or lowest possible value

**Variable: Driving pressure**

Equations: None

Comments/recommendations:

- Alveolar pressure at end inspiration – PEEP

- Keep below 28-30 cmH2O or lowest possible value

**Variable: Auto-PEEP or intrinsic PEEP**

Equations: None

Comments/recommendations:

- Alveolar pressure at end expiration measured woth a pause of 2-3s

- Normal: zero, or equal to PEEP

- Try to keep < 10 cmH2O or the lowest possible value

**Variable: Airway resistance (Raw)**

Equations: (Peak pressure – Plateau pressure, cmH2O)) / Flow (l/s)

Comments/recommendations:

- Needs square wave flow type

- Normal 4-10 cmH2O/l.s

- Try to keep < 20 cmH2O/l.s in obstructive airway diseases

**Variable: Static compliance(Cst)**

Equations: Tidal volume (ml) / (Plateau pressure – PEEP, cmH2O)

Comments/recommendations:

- Normal 50 a 80 ml/cmH2O

- Higher in emphysema

- Lower in in restrictive diseases:

- ARDS

- Cardiogenic pulmonar edema

- Abdominal distension

- Pneumothorax

**Variable: Time constant**

Equations: Raw cmH2O.L.s x Cst L/cmH2O

Comments/recommendations: Note that Cst needs to be in L and not mL/cmH2O

**Variable: I:E ratio**

Equations: One to Exp. time / Insp. time

Comments/recommendations:

Example: Insp. Time of 0.5s; Exp time of 2.5s, than I:E ratio will be, 1 to (2.5/0.5) or 1:5

Gas exchange

**Variable: PaO2 pressure**

Equations: None

Comments/recommendations: Keep between 65 to 85mmHg with the loest possible FIO2

**Variable: PaCO2**

Equations: None

Comments/recommendations:

- Set according to the pH

- Permissive hypercapnia (PaCO2 > 50mmHg) in ARDS, COPD or status asthmaticus

- Keep between 35 to 38 mmHg in acute traumatic brain injury

**Variable: pH arterial**

Equations: None

Comments/recommendations:

- Keep between 7.34-7.44

- Permissive hypercapnia (PaCO2 > 50mmHg) allow acidemia with pH > 7.20

**Variable: SaO2 or SpO2**

Equations: None

Comments/recommendations:

- Keep between 92-97%

- Make sure the SpO2 sensor provides consistent waveforms

**Variable: FIO2 setting **

Equations: FIO2 target = PaO2 target x (FIO2 current / PaO2 current)

Comments/recommendations: Set the lowest possible FIO2

**Variable: PaO2/FIO2 ratio**

Equations: PaO2 (mmHg) /FIO2 (absolute value, not in %)

Comments/recommendations:

- Normal > 400 a 500, sea level

- It may estimate the amount of pulmonary shunt:

- 200-300, 10-20% of shunt

- 100-199, 20-40% of shunt

- < 100, > 40% of shunt

**Variable: Respiratory rate (RR) setting**

Equations: RR target = RR current x PaCO2 current / PaCO2 target

Comments/recommendations: Choose a PaCO2 target according to the patient’s condition and the pH

Weaning predictors

**Variable: Clinical and physiological parameters for SBT interruption**

Equations: None

Comments/recommendations:

- Agitation, sweating, altered level of consciousness

- RR > 35 bpm

- SpO2 < 90%

- Heart Rate > 140 bpm

- Systolic blood pressure > 180 mmHg or < 90 mmHg

**Variable: Maximum inspiratory pressure (MIP)**

Equations: None

Comments/recommendations: MIP < |-25 to -30cmH2O| are associated with extubation failure due to respiratory muscle’s weakness

**Variable: P 0.1**

Equations: None

Comments/recommendations:

- Airway pressure measured in 100ms after initiation of breathing effort Correlates directly to the respiratory drive

- Normal < 4cmH2O, higher values may be associated to weaning failure

**Variable: Rapid shallow breathing (RR/VT) ratio**

Equations: RR bpm / Mean VT (L)

Comments/recommendations:

- Usually measured with the patient disconnected from the ventilator

- Values > 105 bpm/L are associated with a higher risk of failure during the spontaneous breathing test (SBT)

**Variable: Integrative Weaning Index (IWI)**

Equations: Cst ml/cmH2O × SaO2 / (RR/TV) ratio

Comments/recommendations:

- Cst needs to be measured in volume control ventilation with inspiratory hold for 0.5 to 1.0 second with no inspiratory efforts

- IWI>25mL/cmH2O.breaths/min/L is associated with weaning success