Weaning from Mechanical Ventilation

weaning

the process of gradually reducing mechanical ventilatory support until a patient is able to assume sustainable spontaneous breathing

weaning success

the absence of ventilatory support for at least 48 hours following extubation

post-anesthesia extubation

is weaning success rate higher in post-anesthesia extubation or medical condition extubation?

weaning in progress

describes patients who are extubated but continue to receive ventilatory support by noninvasive ventilation

failure of spontaneous breathing trial (SBT)

weaning failure is characterized by...

-Tachypnea

-Tachycardia

-Hypoxemia

-Arrythmias

name four clinical signs of SBT failure

fail

patient is agitated, distressed, diaphoretic, and has increased work of breathing during an SBT. Pass or Fail?

True

True or False: Before weaning, he patient should have recovered from the acute phase of the disease leading to mechanical ventilation.

Rapid Shallow Breathing Index

what does RSBI stand for?

RR/Vt

RSBI formula

RSB increases deadspace ventilation. This is negative, thus why we want RSBI to be less than 100 breaths/min.

How does rapid shallow breathing affect dead space ventilation? Is this positive or negative?

less than 100 breaths/minute

For weaning readiness, what should RSBI be?

less than 4-10 mmHg

what should P(A-a)O2 be be on room air (21% FiO2)?

percentage of shunting

what is Qs/Qt

less than 20%

what should shunt percentage be for weaning readiness?

less than 10%

what is normal shunt percentage?

10-20%

what percentage range represents mild shunting?

-Vital capacity

-Maximum inspiratory pressure (MIP)

Name the 2 weaning criteria in the pulmonary reserve category

greater than 10 cc/kg IBW

what should vital capacity be for weaning readiness?

less than -20 cmH20

what should maximum inspiratory pressure be for weaning readiness?

deadspace to tidal volume ratio

what is Vd/Vt?

less than 60%

what should Vd/Vt ratio be for weaning readiness?

greater than 30 cmH2O

what should static compliance be for weaning readiness?

50 cmH2O

what is normal static compliance?

less than 30%

what is normal Vd/Vt ratio?

FALSE: RSBI should be measured with the use of MINIMUM pressure support

True or False: RSBI should be measured with maximum pressure support.

30 minutes

SBT should be performed no longer than...

True

True or False: SBT may use a T-tube, CPAP, and automatic tube compensation

FALSE: SIMV must be used with pressure support

True or False: SIMV is recommended as a stand alone mode for weaning

adjust pressure support until tidal volume is between 6-8 cc/kg IBW

how do you determine adequate pressure support?

automatic tube compensation

this feature reduces airflow resistance of the artificial airway, allows spontaneous breathing without the effects of an artificial airway, and reduces work of breathing and may facilitate weaning

increased airway resistance

if an ETT is too small for the patient, how would airway resistance be affected?

increase airway resistance

how would condensation in ventilator circuit tubing affect airway resistance?

-Tension pneumothorax

-Pleural effusion

-Migration of the ETT into mainstem bronchus

name 3 causes of a sudden decrease in compliance

-ARDS

-Pneumonia

-Atelectasis

name 3 causes of a gradual decrease in compliance

decrease static compliance

how would obesity affect static compliance?

True

True or False: Prolonged increase in work of breathing may lead to respiratory muscle fatigue and ventilatory failure.

may cause ventilatory muscle fatigue and diaphragmatic atrophy

how can long term ventilatory support affect respiratory muscles?

True

True or False: Pressure support ventilation can be used to retrain atrophied respiratory muscles

Terminal weaning

The withdrawal of mechanical ventilation that results in the death of a patient