Mechanical ventilation protocol

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Vishnu Vardhan Serla M.B.B.S. [2]

Mechanical Ventilation Protocol

Inclusion Criteria

• PaO₂ <= 300 ( corrected for altitude)
• Bilateral (patchy, diffuse or homogenous) infiltrates consistent with pulmonary edema
• No clinical evidence of left atrial hypertension

Ventilator Setup

• Calculate predicted body weight. It is calculated using the formula

Males = 50 + 2.3[height(in inches)-60]

Females = 45.5 + 2.3[height(in inches)-60]

• Selecting the ventilator mode
• Set ventilator settings to achieve initial V_t = 8 ml/kg of predicted body weight
• Reduce VT by 1 ml/kg at intervals ≤ 2 hours until V_T = 6ml/kg PBW.
• Set initial rate to approximate baseline minute ventilation (not > 35 breaths per minute).
• Adjust V_T and respiratory rate to achieve pH and plateau pressure goals below.

Oxygenation Goal

• PaO2 55-80 mmHg or SpO2 88-95% is the goal.
• Use a minimum PEEP of 5 cm H2O.
• Consider use of incremental FiO2/PEEP combinations to achieve goal.

Lower PEEP/Higher FiO₂

FiO2	0.3	0.4	0.4	0.5	0.5	0.6	0.7	0.7	0.7	0.8	0.9	0.9	0.9	1.0
PEEP	5	5	8	8	10	10	10	12	14	14	14	16	18	18-24

Higher PEEP/Lower FiO₂

FiO2	0.3	0.3	0.3	0.3	0.3	0.4	0.4	0.5	0.5	0.5 - 0.8	0.8	0.9	1.0	1.0
PEEP	5	8	10	12	14	14	16	16	18	20	22	22	22	24

Plateau Pressure Goal

• Plateau pressure goal(Pplat) is <= 30 cm H₂O
• Check Pplat every 4^th hourly after change in PEEP ot V_T
• If Pplat > 30 cm of H₂O

Decrease V_T by 1ml/kg

• If Pplat < 25 cm of H₂O and V_T < 6ml/kg

Increase V_T by 1ml/kg unbtil Pplat > 25 cm H₂O or V_T = 6 ml/kg

• If Pplat < 30 cm and breath stacking or dys-synchrony occurs

Increase V_T in 1 ml/kg increments to 7 or 8 ml/kg, if Pplat remains <=30 cm of H₂O

PH Goal

• pH should be maintained at 7.30 - 7.45
• If pH is less than 7.30 (acidosis)

a. Range of 7.15 - 7.30

Increase respiratory rate until pH > 7.30 or PaCO₂

Maximum rate can be 35

b. Less than 7.15

Increase respiratory rate to 35

V_T can be increased in 1 ml/kg until pH >7.15 (Pplat target of 30 may be exceeded)

Bicarbonate can be given

• If pH is more than 7.45 (alkalosis)

Decrease the ventilation rate if possible

I:E Ratio Goal

Recommend that duration of inspiration be less than equal to duration of expiration.

Weaning

A spontaneous breathing trial has to be done daily when

• FiO2 ≤ 0.40 and PEEP ≤ 8.
• PEEP and FiO2 ≤ values of previous day.
• Patient has acceptable spontaneous breathing efforts. (May decrease vent rate by 50% for 5 minutes to detect effort.)
• Systolic BP ≥ 90 mm Hg without vasopressor support.
• No neuromuscular blocking agents or blockade.

Spontaneous Breathing Trial

If all above criteria are met and patient has been in the observed for at least 12 hours, initiate a trial of upto 120 minutes of spontaneous breathing with FiO2 < 0.5 and PEEP < 5

1. Place on T-piece, trach collar, or CPAP ≤ 5 cm H2O with PS < 5

2. Assess for tolerance as below for up to two hours.

a. SpO2 ≥ 90: and/or PaO2 ≥ 60 mm Hg b. Spontaneous VT ≥ 4 ml/kg predicted body weight c. RR ≤ 35/min d. pH ≥ 7.3 e. No respiratory distress (distress= 2 or more)

HR > 120% of baseline

Marked accessory muscle use

Abdominal paradox

Diaphoresis

Marked dyspnea

3. If tolerated for at least 30 minutes, consider extubation.

4. If not tolerated resume pre-weaning settings.