CRITICAL CARE
CRITICAL CARE
CRITICAL CARE
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Central Sydney Health Service Royal Prince Alfred Hospital<br />
This is a ventilator protocol based on the ARDS Network study published in the New England<br />
Journal of Medicine (NEJM 2000;342:1301-8). This was a trial of 861 patients with Acute Lung<br />
Injury (ALI) or Acute Respiratory Distress Syndrome (ARDS) that were randomised to receive<br />
ventilation using tidal volumes based on ideal body weight (IBW) derived from height. The<br />
conventional ventilation group received tidal volumes of 12 ml/kg IBW and the low tidal volume<br />
using 6 ml/kg of ideal body weight (IBW). The study found that patients in the low tidal volume<br />
group had a significantly lower mortality (31% compared to 40%, p=0.007) and a shorter time on<br />
the ventilator (10±11 days vs. 12±11 days, p=0.007).<br />
This is a version of the ARDS Network protocol for low tidal volume ventilation for use on the<br />
Dräger “Evita XL” or “Evita 4” ventilator in ICU at RPAH.<br />
This ventilator protocol is not appropriate for patients with raised intracranial pressure,<br />
spinal cord injury, tricyclic antidepressant overdose, Sickle cell disease, or other conditions<br />
where hypercapnoea would not be tolerated.<br />
INITIAL VENTILATOR SETUP<br />
To Calculate Ideal Body Weight (IBW):<br />
� Tidal volumes are calculated from an ideal body weight calculation, which is derived<br />
from the patient’s height only. It is usually less than the actual body weight.<br />
� Using “Carevue”, go into patient demographics and add patent’s height. IBW will then<br />
be calculated and is displayed in the ventilation window.<br />
� The IBW is calculated from the equations below:<br />
� Males IBW (kg) = 50 + 0.91(height (cm) –152.4)<br />
� Females IBW (kg) = 45.5 + 0.91 (height (cm) –152.4)<br />
Follow steps below for setup:<br />
ARDS NETWORK PROTOCOL FOR<br />
LOW TIDAL VOLUME<br />
MECHANICAL VENTILATION<br />
� Using ‘Carevue’ select ARDS Net protocol in the ‘Add Row’ window. This will bring up<br />
all the necessary required measurements.<br />
� Select the mode as CMV. In this mode, every breath the patient triggers is given at the<br />
set tidal volume. If the patient is not breathing, they will be given the set respiratory rate.<br />
However, if their respiratory rate is higher than the set rate all breaths will be delivered at<br />
the set tidal volume.<br />
� Select Initial tidal volume as 6ml/kg IBW<br />
Version 2.1
Central Sydney Health Service Royal Prince Alfred Hospital<br />
� Set respiratory rate to maintain the minute ventilation (MV) that was recorded prior to<br />
changing the ventilator settings (set f = old MV divided by new VT in litres). This may not<br />
be possible as the maximum set respiratory rate (f) is 35<br />
� Ensure that Autoflow is turned on.<br />
� The airway pressure alarm must be set at 35 cm H2O.<br />
This will limit the maximal airway pressure to 30 cm H2O.<br />
� Turn the Flow Trigger “On” and set it to 2 L/min<br />
� Adjust the Inspiratory time to start with an I:E ratio of 1:3. I:E ratio is displayed in the<br />
bottom left corner of the “Ventilator settings” screen when Tinsp is selected.<br />
� Adjust the FiO2 and PEEP as outlined in the section arterial oxygenation goal<br />
(see below).<br />
SUBSEQUENT VENTILATOR ADJUSTMENTS<br />
TIDAL VOLUME AND INSPIRATORY TIME ADJUSTMENTS<br />
� These may be necessary if the alarm “pressure limited, volume not constant” occurs.<br />
This alarm indicates that the ventilator cannot deliver the programmed volume in the time<br />
allowed whilst keeping the pressure under the alarm limit of 35 cm H2O (actual airway<br />
pressure of 30 cm H2O). In this case the ventilator will deliver a lower tidal volume,<br />
rather than exceed the pressure limit. There are two solutions to this problem.<br />
1) Increasing the inspiratory time allows more time for the set tidal volume to be<br />
delivered without exceeding the pressure limit. Initially, the Tinsp should change I:E<br />
ratio from 1:3 to 1:2. If this does not help an I:E ratio of 1:1 should be used.<br />
2) If the above does not resolve the alarm reduce the tidal volume in one ml/kg IBW<br />
increments. This may be repeated every few minutes to a minimal tidal volume of<br />
4 ml/kg IBW. The tidal volume should not be reduced below this. If a tidal volume<br />
of 4 ml/kg is necessary, medical staff should be made aware.<br />
� If the patient’s tidal volume is less than 6 ml/kg IBW, regular attempts should be made to<br />
increase it, in 1 ml/kg IBW increments, back towards 6 ml/kg. The ability to do this will<br />
be limited by the alarm “pressure limited, volume not constant” as described above. A<br />
tidal volume of 8 ml/kg may be used after discussion with the ICU consultant and<br />
documentation in the notes.<br />
� If the patient is receiving 6 ml/kg IBW, attempts should be made to reduce the inspiratory<br />
time to give an I:E ratio of 1:3.
Central Sydney Health Service Royal Prince Alfred Hospital<br />
ARTERIAL OXYGENATION GOAL<br />
Goal: SpO2 = 88 to 95 % or PaO2 = 55 to 80 mm Hg if ABG available<br />
� Adjust the FiO2 and PEEP according to the combinations outlined below. This can be<br />
performed every 5-10 minutes.<br />
� Adjustment to oxygenation can be made on SpO2 alone. It is not necessary to do blood<br />
gases to change FiO2. Blood gases should be performed as indicated. However, if a PaO2<br />
is available adjustments are made based on it, rather than SpO2.<br />
Fi02<br />
Peep<br />
0.3<br />
5<br />
0.4<br />
5<br />
0.4<br />
8<br />
0.5<br />
8<br />
0.5<br />
10<br />
0.6<br />
10<br />
ARTERIAL pH and PaCO2 / EtCO2<br />
Goal: pH = 7.30 – 7.45<br />
0.7<br />
� Leave the respiratory rate at the current settings<br />
Acidosis management: pH 7.10 – 7.30<br />
� Increase the ventilator rate until pH > 7.30 or PaCO2 < 35<br />
� PaCO2 is related to minute ventilation (MV = Vt x f)<br />
� Increasing f increases MV and “blows off” CO2 increasing pH<br />
� Maximum set ventilator rate is 35 bpm<br />
Acidosis Management: pH < 7.10<br />
� Increase the set ventilator rate to 35 bpm<br />
10<br />
� If pH remains < 7.10, tidal volume may be increased in 1ml/kg IBW steps until pH > 7.10<br />
Inform the senior register or duty consultant of an increase in tidal volume above 8 ml/kg<br />
IBW<br />
Alkalosis Management<br />
� Decrease the ventilator rate if possible<br />
0.7<br />
12<br />
0.7<br />
14<br />
0.8<br />
14<br />
0.9<br />
14<br />
0.9<br />
16<br />
0.9<br />
18<br />
1.0<br />
20-<br />
24
Central Sydney Health Service Royal Prince Alfred Hospital<br />
WEANING FROM THE MECHANICAL VENTILATION<br />
� The weaning process is initiated by a CPAP trial. This should only occur once each day<br />
if the correct criteria are met (see indications for CPAP trial). It should only be initiated<br />
by the consultant or senior registrar and will usually be initiated on the ward round.<br />
WEANING FAILURE<br />
� Any weaning process (CPAP trial or Pressure Support Weaning) is considered to have<br />
failed if any of the following occur:<br />
� f > 35/min<br />
� Sp02 < 88%<br />
� Respiratory distress is present (more than 2 of the following)<br />
� Pulse >120% of the usual rate for >5 minutes<br />
� Marked use of accessory muscles<br />
� Abdominal paradox<br />
� Diaphoresis<br />
� Marked complaints of dyspnea<br />
� Should weaning failure occur the patient is placed back on CMV until the next day<br />
CPAP TRIAL<br />
� Conduct a CPAP trial daily when all the following are present:<br />
� Fi02 ≤ 0.4 and PEEP ≤ 8 cm H20<br />
� Subject has spontaneous breathing efforts.<br />
It may be necessary to decrease set rate by 50% for 5 minutes to detect respiratory<br />
efforts<br />
� Haemodynamically stable<br />
� To set CPAP of 5 cm H20 and Fi02 0.50<br />
� Set mode on the Dräger to PSV<br />
� Set PS 0 cm H2O<br />
� Set PEEP 5 cm H2O<br />
� Set FiO2 to 0.5<br />
� If f ≤ 35/min for 5 minutes<br />
� Advance to Pressure Support Weaning Procedure<br />
� If f > 35/min in < 5 minutes<br />
� CPAP trial not tolerated<br />
� return to previous CMV ventilator settings and reassess the next morning.<br />
� Occasionally it may be appropriate to repeat the trial after an appropriate intervention<br />
such as suctioning, analgesia, or anxiolysis if these contributed to weaning failure.
Central Sydney Health Service Royal Prince Alfred Hospital<br />
� In CareVue record on the “CPAP trial” line (ventilation window) whether the CPAP<br />
trial was PASSED or FAILED<br />
PRESSURE SUPPORT (PS) WEANING PROCEDURE<br />
Initial Pressure support settings:<br />
� Set PEEP 5 cm H20 and Fi02 0.5<br />
� Set initial PS based on f during CPAP trial:<br />
� If CPAP f < 25 /min<br />
� Set PS 10 cm H20<br />
� If CPAP f = 25-35 /min:<br />
� Set PS 20 cm H20<br />
Subsequent pressure support weaning settings:<br />
� Subsequent Pressure Support adjustments are made on respiratory rate (f) every 10-<br />
15min<br />
� If f > 25 increase Pressure Support by 2 to 5 cm H2O<br />
� Maximum pressure allowed, PEEP + PS = 30 cm H2O<br />
� Pressure airway alarm should be at 35 cm H2O<br />
� If f < 20 decrease Pressure Support by 2-5 cm H2O<br />
� If f > 35 and/or PEEP + PS > 30 cm H2O weaning has failed and CMV is initiated as<br />
above<br />
Subsequent Oxygen and PEEP Adjustments:<br />
� Adjustments are made as per Oxygenation Goals outlined above<br />
� If FiO2 > 0.5 and PEEP > 10 cm H2O are required while on pressure support ventilation,<br />
strong consideration should be given to reinitiating CMV as above. Inform the medical<br />
staff.<br />
EXTUBATION / SWEDISH NOSE VENTILATION<br />
� Extubation or spontaneous ventilation via a Swedish nose and tracheostomy should be<br />
considered if the following criteria are met.<br />
� f < 30 on Pressure support 5-7 cm H2O<br />
� Oxygenation goals are met with<br />
� PEEP of 5 cm H2O<br />
� FiO2 of 0.4 or less
Central Sydney Health Service Royal Prince Alfred Hospital<br />
Occupational Health and Safety: Universal precautions taken in the preparation, administration of drug and<br />
disposal of equipment and sharps.<br />
Cross Referenced: RPAH Occ. Health & Safety Manual and Infection Control Manual<br />
NSW Infection Control Policy 98/99<br />
Revised by: Clive Woolfe October 2, 2003<br />
Authorised by: Clive Woolfe, Intensivist<br />
Revision due: 2005<br />
With the introduction of Powerchart online ordering, a clinical agreement has been set up with the Director<br />
of ICS and other Staff Specialists. Nursing Management, with the agreement of the hospital executive, have<br />
made arrangement that allows all permanently employed RPAH Nursing Staff to place orders for a variety of<br />
tests on their behalf. It is a Health Insurance Commission (HIC) directive that all orders placed by nursing<br />
staff are countersigned by the responsible MO within 14 days.