Niv and weaning

NIV And Weaning
Mostafa Elshazly
Professor Of Pulmonary Medicine
Chairman Of PCCU
Kasr Alainy School Of Medicine
Cairo University
elshazly66@hotmail.com

Esteban A, , et al. Evolution of mechanical ventilation in response to clinical research. Am J Respir Crit Care Med 2008; 177:170–177
• It has been estimated that 40% of the
time a patient is mechanically ventilated
is dedicated to the process of weaning.

The current clinical challenge is to
improve weaning from MV in critically ill
patients who fail the first test of
spontaneous breathing.

NIV And Weaning
Patients undergoing a SBT as part of a failed weaning attempt will
probably develop a rapid and shallow breathing pattern, with an
increased workload on the respiratory muscles.
This is accompanied by a progressive increase in dynamic lung
elastance, intrinsic PEEP, inspiratory resistance and work of breathing
in COPD patients

NIV And Weaning
A high drive to breathe coupled with the imbalance between the
increased workload and reduced inspiratory muscle strength causes
respiratory distress and hypercapnia.
These changes are not seen in patients who successfully tolerate a SBT.

NIV And Weaning
Switch from PPV to SB may increase
left ventricular afterload as a result of:
• an increase in the venous return
• large negative deﬂections in intrathoracic
pressure due to the inspiratory threshold load

NIV And Weaning
This results in decreased
SvO2 during SB.
By contrast, mixed venous
oxygen saturation (SvO2) is
unchanged or increased
during SB in successfully
weaned patients

Use Of NIV During Difficult And Prolonged Weaning
• The primary end-point when NIV is used for patients
with difficult or prolonged weaning should be
shortening weaning and avoiding re-intubation.

• 50 intubated COPD patients with severe hypercapnic RF , who
had recovered from their exacerbation within 48 h of initiation
of MV but had failed a SBT using a T-piece, were randomly
allocated to receive:
• 1) extubation and noninvasive PSV; or
• 2) continuing intubation and PSV.
Nava S, Ambrosino N, Clini E, et al. Noninvasive mechanical ventilation in the weaning of patients with RF due to COPD . A randomized, controlled trial. Ann Intern
Med. 1998;128:721–8.

• Patients receiving noninvasive PSV were ventilated for a
shorter period, had a shorter ICU stay, a lower incidence of
nosocomial pneumonia and improved 60-days survival
Noninvasive PSV was as eﬀective as invasive PSV
for maintaining PaCO2 and arterial pH
Nava S, Ambrosino N, Clini E, et al. Noninvasive mechanical ventilation in the weaning of patients with RF due to COPD . A randomized, controlled trial. Ann Intern
Med. 1998;128:721–8.

• 33 intubated hypercapnic RF patients with failure of a single
weaning trial were randomly allocated to:
• 1) remain intubated and receive PSV; or
• 2) undergo extubation and noninvasive PSV.
NIV reduced the average length of the endotracheal MV period by 3 days
The incidence of complications associated with intubation and weaning, length
of stay and survival were not significantly diﬀerent.
Girault C, Daudenthun I, Chevron V, et al. Noninvasive ventilation as a systematic extubation and weaning technique in acute-on-chronic respiratory failure: a
prospective, randomized controlled study. Am J Respir Crit Care Med. 1999;160:86–92.

• 208 intubated patients with chronic hypercapnic RF and DW
were randomly allocated to receive:
1) conventional invasive weaning;
2) extubation followed by standard oxygen therapy; or
3) extubation followed by NIV
No difference was found in the reintubation rate between the three weaning strategies.
NIV decreases the intubation duration and may improve the weaning results in difficult-to-
wean patients with CHRF by reducing the risk of postextubation ARF.
Girault C, Bubenheim M, Abroug F, et al. Noninvasive ventilation and weaning in patients with chronic hypercapnic respiratory failure. Am J Respir Crit Care Med.
2011;184:672–9

• 43 patients with prolonged weaning, 33 of whom had
underlying chronic respiratory disorders, who had failed SBTs
on three consecutive days were randomly allocated to:
• 1) extubation and NIV; or
• 2) a conventional weaning approach with continuing intubation.
Patients receiving NIV had shorter periods of both endotracheal and
total MV , shorter ICU and hospital stays, a reduced incidence of
nosocomial pneumonia and septic shock/multiple organ failure, a
reduced requirement for tracheostomy to facilitate weaning, and
improved survival.

• A systematic review and meta-analysis of the use of NIV to
wean critically ill adult patients from MV identified a total of 16
RCTs or quasi-RCTs published or presented as abstracts.
• NIV had a consistently positive eﬀect on mortality and
ventilator-associated pneumonia as well as other relevant
outcomes, without increasing the risk of weaning failure or
re-intubation

None of the randomized controlled studies found NIV to be
inferior to weaning with the endotracheal tube in place.
The individual studies discussed above and the
systemic review indicate that NIV can successfully
facilitate weaning, principally in patients with COPD.

Use Of NIV
During
Difficult And
Prolonged
Weaning

Limitations of the use of NIV during weaning
• The majority of published studies have been conducted in
selected populations of patients with underlying chronic airﬂow
obstruction and hypercapnic RF, who are hemodynamically
stable , and have a normal level of consciousness, no fever and
a preserved cough reﬂex

Limitations of the use of NIV during weaning
• The main reasons for NIV failure are
• Lack of cooperation,
• Excessive secretions,
• Severe strength–load imbalance and
• Hemodynamic instability.
All of these factors can be addressed by protection of the
airways and proper medical therapy.

Key major recommendations
• Noninvasive ventilation can be used to facilitate weaning in a select group
of COPD patients who have been intubated for at least 24 h secondary to
an acute exacerbation and who have failed one or more trials of
spontaneous breathing.

• It must be remembered that NIV should only be used in a
patient who has satisfied the criteria to undertake a SBT.
• This strategy should be restricted to patients who demonstrate some degree
of recovery from the acute process that led to intubation and exhibit
adequate oxygenation (e.g., PaO2/FiO2 ≥120–150 on PEEP ≤5–8
cmH2O), hemodynamic stability (adequate blood pressure with little or no
vasopressor support), and some spontaneous breathing efforts.

• The patient must be a good candidate for NIV.
• They must be able to tolerate the mask chosen to deliver NIV.
• The patient must be capable of SB for at least 5–10 min to allow for
fitting and adjustment of the mask and the fine-tuning of the
ventilator required to ensure optimal NIV support.
• NIV in this setting may be contraindicated in patients deemed to be
technically difficult to reintubate; this group should be considered
for tracheostomy.

• Once extubated to NIV, patients must be observed closely, and
health- care providers with expertise in airway management should
be readily available.
• If signs of respiratory distress are present, despite NIV, and do not
resolve (or worsen) within 4 h of extubation, reintubation should
occur without delay

NIV to avoid re-intubation
• Some patients experience RF requiring re-intubation after
extubation though they have fulfilled the criteria for weaning
and successfully passed SBT.
• Extubation failure can be defined as an episode of RF
requiring ventilatory support, occurring within 48 h of
deliberate or unplanned extubation.
• Rates of extubation failure as high as 23.5% have been reported.

NIV as a preventative strategy
• Some patients experience RF requiring re-intubation after
extubation though they have fulfilled the criteria for weaning
and successfully passed SBT.
• Extubation failure can be defined as an episode of RF
requiring ventilatory support, occurring within 48 h of
deliberate or unplanned extubation.
• Rates of extubation failure as high as 23.5% have been reported.

• NIV has been assessed as a preventative strategy in ventilated
ICU patients who have risk factors for post-extubation failure,
such as age greater than 65, poor cough, cardiac and
respiratory comorbidity, and hypercapnia (while ventilated or
preexisting).
NIV As A Preventative Strategy

NIV As A
Preventative
Strategy

NIV As A Preventative Strategy

NIV as a rescue treatment
• There have been several RCTs examining the use of NIV as a
rescue treatment for post-extubation respiratory distress

NIV as a rescue treatment
➢We conclude that NIV is not effective in averting the need for reintubation
in unselected patients in whom RF develops after extubation.
➢In addition, NIV does not improve survival and may in fact be harmful.
➢Although selected patients in specialized centers may benefit from this
therapy, specific hypotheses need to be tested prospectively.

When To Stop
• If the decision is made to use NIV in the post-extubation
period, it is important to monitor the patient closely.
• Clinical signs of NIV failure should be closely assessed

When To Stop
• Fatigue: tachypnea, accessory muscle use, abdominal paradox
• Tolerance: mask and pressure
• SpO2, heart rate, blood pressure
• Ability to clear airway secretions
• Arterial blood gases
• Patient wishes

When To Stop
• Strong consideration should be given to reintubation if
the respiratory status of the patient is not improving
over the first hour after initiation of NIV.

Setting Up the NIV Support
• Patient cooperation after extubation, absence of
deteriorating mental status, absence of hemodynamic
instability, and ability to protect airways, are crucial to
the application and success of NIV

• For “preventive” and “curative” approaches, both
CPAP and NIV have been used
• For NIV, pressure support ventilation (PSV) is the mode
of ventilation most often used.

• In general, the studies that evaluated the use of PSV
and positive end-expiratory pressure (PEEP) after
extubation do not suggest a specific approach in this
setting

• Usually, PEEP is started at 3–5 cmH2O and increased as
needed to improve oxygenation, without adverse hemodynamic
effect.
• PS is started at the same level (3–5 cmH2O) and increased in
increments of 2 cmH2O to achieve 6–8 ml/kg VTE, a decrease in
the patients’ RR , and a comfort improvement; the average
pressure support level is 12–15 cmH2O.

• The slope of delivered pressure (i.e., speed of
pressurization) is set up as maximum tolerated,
inspiratory and expiratory trigger of 3 l/min, and 50 %
of peak inspiratory flow

• So far, there are three different weaning/duration
approaches
(1) gradual decrease in duration of NIV,
(2) gradual decrease in ventilator support level and duration
(3) abrupt discontinuation of NIV when clinical and gas
exchange/ pH targets have been achieved.

Niv and weaning

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