Weaning Protocols in Prolonged Mechanical Ventilation: What Have We Learned?


I. Pre-daily screening at time of admission:

 Evaluate for clinical stability including sedatives, analgesics requirement and delirium [24]

 Glasgow Coma Scale >13

 Evaluate to begin inspiratory muscle strength training

 Evaluate to begin whole-body physical therapy

II. Daily screening:

 Hemodynamic variables

  Heart rate between 50 and 120 beats/min

  Systolic blood pressure between 90 and 180 mmHg

[All variables must be met]

 Respiratory variables

  FIO2 <50 % with SpO2 >90 %; PEEP <8 cm H2O

The following variables measured during spontaneous breathing:

  Tidal volume >5 ml/kg

  Respiratory rate <35 breaths/min

  Rapid shallow breathing index (f/VT) <105 breaths/min/l

  Maximum inspiratory pressure less than −20 cm H2O

[4 out of 5 variables must be met]

III. Spontaneous breathing trial (SBT)

 One hour SBT via tracheostomy collar and humidified O2

 Assess for respiratory distress

  Heart rate increased or decreased >20 % of baseline

  Systolic blood pressure <80 or >180 mmHg

  SpO2 <90 %

  Respiratory rate >35 breaths/min

  Agitation

  Anxiety

  Diaphoresis

  Patient request

 If any of the above signs are present, return patient to previous ventilator settings and reassess the following morning.

IV. Weaning method

 Tracheostomy collar with humidified O2:

  If patient tolerates 1 h of SBT, increase SBT (tracheostomy collar and humidified O2) to a total of 2 h, progressing with an increment of 2 h daily (i.e., 4, 6, 8, 10, 12 h) divided in two separate sessions (e.g., 2 h twice a day for a total of 4 h of SBT).

  If patient tolerates 12 h of SBT, increase duration with an increment of 4 h daily (i.e., 16, 20, 24 h).

  Return to previous ventilator settings for any intolerance.

 Pressure support:

  If patient does not tolerate within the first 12 h of SBT, may use pressure support (PS) as alternative weaning method. PS level titrated until patient does not display signs of respiratory distress (see above) for at least 6 h before attempts to decrease PS level, or reassess the following morning.

  For PS trial, reduce PS level daily at a decrement of 2 cm H2O twice a day until patient tolerates PS of less than 6 cm H2O for 12 h, then progress to SBT via tracheostomy collar and humidified O2 with an increment of 4 h daily as above (i.e., 16, 20, 24 h).






6.3 Summary


A weaning protocol in patients requiring PMV leads to shortened weaning time and expedient decision-making but not an increase in weaning success rate. Increasing the successful weaning rate requires enhancement of inspiratory muscle capacity and limb muscles strength. Overall weaning time is shortened with unsupported breathing (tracheostomy collar). In patients with early weaning failure, weaning time is similar using PS as an alternative weaning method.


6.4 Future Research


There exists a paucity of studies of the effects inspiratory muscle strength training and whole-body rehabilitation in patients requiring PMV. During cardiothoracic surgery, brief phrenic nerve stimulation has been shown to increase force generation in diaphragm muscle single-fiber preparation compared with unstimulated contralateral hemidiaphragm [23]. This preliminary data suggests that intermittent phrenic nerve stimulations have the potential to improve diaphragm muscle strength in patients requiring PMV. Similarly, because upper limb muscle strength training contributes to shorten weaning time [22], studies of physical therapy focusing on upper limb muscle strengthening are needed.

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Oct 12, 2016 | Posted by in CRITICAL CARE | Comments Off on Weaning Protocols in Prolonged Mechanical Ventilation: What Have We Learned?

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