5 - Discontinuing Mechanical Ventilation

guidelines for discontinuing MV

• reversal of disease

• CV stability (BP, C.O.)

• nutrition and rest

• ventilatory ability

• gas exchange

MV discontinuation criteria

• V_T

> 5 mL/kg IBW

MV discontinuation criteria

• RR/f

8-20 b/min

MV discontinuation criteria

• VC

> 10 mL/kg IBW

MV discontinuation criteria

• NIF/MIP

< −20 cmH₂O

MV discontinuation criteria

• V_E

5-10 L/min; patient able to double on demand

MV discontinuation criteria

• WOB

no signs of WOB

MV discontinuation criteria

• CNS depressants

little/no CNS depressants used

MV discontinuation criteria

• rate-volume ratio (RVR)

< 100

MV discontinuation criteria

• inspiratory pressure at 0.1 sec

0 to −2

MV discontinuation criteria

• ABG

normal with F_iO₂ < 50% and PEEP 3-5

MV discontinuation criteria

• shunt

< 20%

MV discontinuation criteria

• P_A-aO₂

< 300

MV discontinuation criteria

• V_D/V_T

< 60%

steps of discontinuing MV without weaning (< 2 days MV)

1. prepare patient physically and psychologically

2. attach patient to T-piece O₂ delivery system (same/higher F_iO₂) or CPAP

3. ABGs in 15-20 minutes

4. evaluate need for artificial airway

weaning from MV

• (S)IMV

• speed of rate reduction depends on patient’s clinical condition and length of MV

• COPD: low rate to avoid respiratory muscle atrophy and ventilator dependence

weaning from MV

• CPAP/PS

• may increase muscle endurance, patient-ventilator synchrony, and comfort

• decreases WOB

• contraindication: no respiratory drive

• complications

  • system leak may cause high continuous flow

  • patient may not be able to breathe pressure-supported breaths with inline SVN

weaning from MV

• closed-loop (MMV, VS, automode)

• pros

  • better P_aCO₂ control than IMV

  • fewer ABGs and ventilator adjustments

  • faster weaning

• cons

  • rapid breathing can meet V_E but cause hypercapnia

  • ventilator must have high rate and/or low V_T alarm and feedback mechanism

signs of weaning failure

• tachypnea

• accessory muscle use

• paradoxical abdominal movement

• dyspnea

• sweating

• chest pain

causes of weaning failure

• increased R_aw

• decreased C_L

• decreased respiratory muscle strength

terminal weaning (“pulling the plug”) criteria

• hopeless/futile intervention

• untreatable pain and suffering due to disease