Ventilator Management in COPD

Author: Justin Bright, MD (Senior Staff Physician, Henry Ford Hospital, Department of Emergency Medicine, Detroit, MI) // Editor: Alex Koyfman, MD

 

Its 7:01am.  Your shift in your department’s high acuity area is just beginning, and you are waiting to receive sign out.  There hasn’t even been time to get your first sip of coffee.  Just as you are lifting your cup to your lips, the charge nurse grabs you and says, “Doctor, I need you!  This patient isn’t looking so good!”

You enter the room, and find a patient, ashen gray, somnolent and slumped over, barely breathing.  You have no other history other than she was dropped off by her husband, who is in the waiting room, and that the chief complaint at intake was difficulty breathing.  The nurse who grabbed you says the patient deteriorated quickly in the 15 minutes she was in triage to the time she made it back to the treatment area.

You perform a very quick exam:

Vitals: Tc unknown  HR 35  RR 6  SaO2 25% on RA  Blood Sugar 109

Constitutional: somnolent, unresponsive, looks significantly older than stated age of 57 years old

Cardiac: Bradycardic, no other abnormalities

Respiratory: Apneic, minimal air movement, no wheezing appreciated

As team leader, it is obvious to you that this patient needs to be intubated.  Prior to intubation, she is vigorously bagged in an effort to improve the pulse oximetry.  Despite perfect technique, the patient’s pulse oximetry will not go above 50%.  She is intubated using RSI and direct laryngoscopy.  You do so without any complication.  But, when you attempt to bag ventilate this patient, it feels firm as a rock, and she has minimal improvement in her pulse oximetry.  Her heart rate continues to hold in the 30s.  Everyone in the room is getting tense.

Question:

            Why is your patient so difficult to bag? What differentials must you consider?

Answer:

In most instances, when you intubate a patient in respiratory failure, you experience relief because you addressed the patient’s critical issue.  With COPD patients, intubation can make a patient significantly worse – even kill them – if you don’t respect the pathophysiology of the disease process.  Conversely, if you know the possible obstacles waiting for you in the minutes and hours post-intubation, you can plan for them and insure the problem is addressed before it happens.

This patient’s respiratory physiology is working against her.  The core issue of COPD is not getting a breath in – it’s getting a breath out.  When considering possible reasons why ventilation is not improved post-intubation, you need to think in terms of mechanical obstruction, mechanical malfunction, and pressure.  The leading possibilities for why this patient cannot be adequately bagged after intubation are:

1) Auto-PEEP (“breath stacking”)

2) Tension pneumothorax

3) Tube obstruction

4) Malfunction of apparatus

Question:

What is auto-PEEP?

 Answer:

Auto-PEEP is a dynamic hyperinflation of the lungs due to inspiration before exhalation of the preceding breath can be completed.  This hyperinflation causes an increase in alveolar and intrathoracic pressure.  The ultimate end game of auto-PEEP is elevated intrathoracic pressure that causes systemic vascular return to be decreased.  The lack of SVR will cause hemodynamic collapse, and is a common cause of cardiac arrest post-intubation in COPD patients.  Other possible sequelae of auto-PEEP are barotrauma, ventilator-induced lung injury, and V/Q mismatch.

There are 3 main ways auto-PEEP occurs:

1) High minute ventilation – high respiratory rates or high tidal volumes

2) Expiratory flow limitation – airway collapse due to bronchospasm, inflammation, or remodeling

3) Expiratory resistance – kinked or obstructed endotracheal tubes

The most common auto-PEEP pitfall post-intubation is in improper bagging rate and incorrect ventilator settings.  Both of these lead to high minute ventilation.  Often times bagging of a COPD patient happens at far too fast of a rate.  Your adrenaline is pumping, and you’re constantly watching the pulse oximetry on the monitor, waiting for it to come up.  The time delay from intubation until you see pulse oximetry improvement seems like an eternity, and it’s natural to bag even faster trying to make it come up.  This is exactly the opposite of what your patient needs.  In the case I presented, the patient was bagged vigorously in an effort to improve the pre-oxygenation prior to intubation.  I believe this contributed to our difficulties post-intubation.  Once the endotracheal tube was placed, we were bagging the patient once every ten seconds.

Question:

            How do I set the ventilator after intubating a COPD patient?

 Answer:

The primary concern when ventilating a COPD patient is maintaining as long of an expiratory phase as possible.  This needs to be communicated to your respiratory therapist, who may make the initial ventilator settings based on a standard protocol.  Small tidal volumes and very low respiratory rates are necessary to adequately ventilate your patient.  In my personal experience, I usually can get an I:E ratio of 1:4.  For me, high peak pressures seem to limit any longer expiratory phase.

 Question:

What do I do if my COPD patient codes shortly after intubation?

 Answer:

The first thing you need to do if your patient is already on the ventilator is disconnect it.  After that, your first consideration has to be that the patient’s hemodynamic collapse is due to auto-PEEP.  You need to press on the patient’s chest with both hands, and try your best to expel any air you can from the thoracic cavity.  If you’re lucky, this will make the patient easier to bag and cause the patient to regain a pulse.

If you and your patient are not that lucky, your next considerations need to be endotracheal tube obstruction or tension pneumothoraxSuctioning the endotracheal tube may relieve obstruction due to mucous.  I recommend suctioning the patient before bilateral needles and chest tubes because suctioning is faster, clearly less invasive, and may fix the problem before initiating a process you can’t undo.

Question:

What are some final pearls about post-intubation management of a COPD patient?

Answer:

It is a common pitfall to get so caught up in the intubation and resuscitation of such a critical patient, that simple things like continuous in-line nebulizers are forgotten.  Continuous nebulizers will help resolve the bronchospasm, thereby improving any expiratory flow limitation and reducing auto-PEEP.  Also, don’t forget a paralysis and sedation plan post-intubation.  In the acute stages, COPD patients will likely require long-acting chemical paralysis and judicious sedation to prevent triggering their own breaths and increasing auto-PEEP.

In the emergency department, many times there is a correlation between severity of illness and degree of head elevation on the cot.  Low acuity patients are ambulatory or sit upright, while critically ill patients lay flat.  Laying a COPD patient flat post-intubation is to their detriment.  Doing so may increase expiratory flow limitation, and subsequently cause more auto-PEEP.  It is recommended that patient’s be positioned semi-recumbent post-intubation.

Case Resolution:

            This patient was intubated without complication, but was incredibly difficult to bag ventilate after.  Three separate attempts were made to push on the patient’s chest to expel air, and each time only had a brief improvement in the patient’s clinical status.  Two enormous mucous plugs were subsequently suctioned out of the patient’s endotracheal tube, and the patient became easier to bag, and her pulse oximetry improved into the mid-70s, and her heart rate got into the 50s.  Bagging then became more difficult again, and we decided to place bilateral needle thoracostomies and subsequent chest tubes.  I believe it was the combination of chest compression, suction, and chest tubes that finally produced a situation where the patient could be adequately ventilated.  She was bagged 6-8 times per minute until her pulse oximetry reached 100%, and her HR and blood pressure normalized.

She was connected to the ventilator with the plan for low tidal volumes and respiratory rates communicated to the respiratory therapist.  Continuous in-line nebulizers were started, as were steroids and empiric broad-spectrum antibiotics.  Initial chest x-ray showed a right sided infiltrate that culture results showed was due to Klebsiella.  The patient’s initial ABG showed a pCO2 of 142!!  When I followed up on the patient to write this post, she had a 14-day MICU course with inability to wean from the vent.  Her family made the decision to withdraw treatment and enter hospice.  The patient ultimately died within hours of extubation.

 

References:

-Intrinsic positive end-expiratory pressure in mechanically ventilated patients with and without tidal expiratory flow limitation.  Armaganidis A, Stavrakaki-Kallergi K, Koutsoukou A, Lymberis A, Milic-Emili J, Roussos C. Crit Care Med. 2000;28(12):3837.

-Intrinsic positive end-expiratory pressure (PEEPi). Rossi A, Polese G, Brandi G, Conti G. Intensive Care Med. 1995;21(6):522.

-Expiratory muscle activity increases intrinsic positive end-expiratory pressure independently of dynamic hyperinflation in mechanically ventilated patients. Lessard MR, Lofaso F, Brochard L. Am J Respir Crit Care Med. 1995;151(2 Pt 1):562

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