62 years old female who was intubated for acute on chronic hypercapnic respiratory failure secondary to COPD exacerbation. Her ideal body weight is 67 Kg. CXR shows severely hyperinflated lungs.

Patient was placed on AC mode of ventilation with VT of 450 mL, RR of 22 per minute, and an inspiratory flow of 60 L/min. Her minute ventilation was 10 liters per minute.

Blood gases revealed acute on chronic respiratory acidosis with pH of 7.22 and pCO2 of 75

An inspiratory hold maneuver was done and shown in the following screenshot:

Feb 15, 2024

I guess all the answers are right, the goal is to prolong the expiratory time to allow for complete exhalation of the air. I would start by increasing the flow rate trying to decrease the inspiratory time and I:E ratio without changing the minute ventilation. Then I would decrease the tidal volume and/or the rate and accepting permissive hypercapnea. Adding external PERP can help triggering on the ventilator as this would allow the patient to exert less efforts.

This screenshot shows an increased flow rate to 70 L/min, decreased rate to 14, and decreased tidal volume to 450:

inspiratory hold now shows improved plateau pressure to 22:

And expiratory hold shows improved autoPEEP to around 5-7:

Blood gases improved despite decreased minutes ventilation:

Mazen Kherallah

January 26, 2024

Ventilator graphic of an intubated asthmatic patient on mechanical ventilation showing mild persistent flow at end of expiration indicating auto-PEEP:

The ventilator settings were changed as the following:

VT decreased from 470 to 420 mL.

Rate decreased from 20 to 16 breaths per minute but the patient is still breathing over.

The inspiratory time was decreased from 0.9 second to 0.6 second.

Feb 01, 2024

•

Improving in auto PEEP , it can be achieved by :

1) decrease in RR ,

2) decrease in Tidal Volume,

3) by decreasing inspiration time, expiration time will be automatically increased.

Mazen Kherallah

December 29, 2023

PRVC mode of ventilation with a targeted VT of 400, RR 26 and I:E ratio of 1:1.5. Notice the dynamic hyperinflation (autoPEEP) with persistent flow at end of expiration and the ineffective triggers.

Ventilator settings were adjusted to allow longer expiration by decreasing the rate to 20 per minute, and decreasing inspiratory time with I:E at 1:2.9. The volume was also increased to 450 ml.

Dynamic hyperinflation improved remarkably and now the ventilator is triggered with every inspiratory effort of the patient.

Respiratory Dynamics

Ventilator Graphics

Ventilatory Asynchrony

Respiratory Failure

Noor Ali Shah

Dec 29, 2023

•

In the first setting of ventilator, there were two issues discovered

1) Auto Peep due to low expiration time, leading to air trapping- Auto Peep, by decreasing RR expiration time increased lead to resolved the auto peep issue as shown in second picture.

2) The second issue discovered what I observed was “ Air Hunger or Starvation ” in flow time waves, which was resolved by increasing Tidal Volume or Peak flow.

Thanks Dr. Mazen for sharing such interesting articles.

Edited

Mazen Kherallah

December 23, 2023

As you know, patients with severe asthma and status asthmaticus develop dynamic hyperinflation syndrome and autoPEEP meaning that the inhaled air does not get exhaled completely and the pressure is built up inside the alveoli. This is caused by not enough expiratory time due to the high time constant of the airways. My question, what will happen next if the process continues?

How does dynamic hyperinflation progress if no change in the expiratory time made on the ventilator?

0%Continues to build till the lung ruptures
0%Stops on its own due to increased driving pressure
0%I do not know!

You may want to see this video to help you understand the concept.

Respiratory Dynamics

Respiratory Failure

Paolo Copetti

Dec 23, 2023

It should stop when the higher elastic recoil caused by the hyperinflation permits the expiration to be be faster enough to be completed (provided this equilibrium takes Place within the limits of lung parenchima integrity otherwise barotrauma May result). Time constant (compliance x resistance) Is the core variabile.Shall we Say that the equilibrium Is found without barotrauma when the decrease in compliance can compensate for the increased resistance?and on the other end that we may have a PNX when the residence Is so High that the compliance required to balance It must be so low that in would require the lung to be that overstached that It goes beyond its limits?

Mazen Kherallah

December 22, 2023

47 years old female with status asthmatics who got intubated and placed on mechanical ventilation. An inspiratory hold was applied as shown in this snapshot of the ventilator screen:

Notice the limitation of the expiratory flow in the first breath before the inspiratory hold. Also notice that the peak pressure is elevated at 46 cm H2O, the plateau is elevated at 30 cm H2O and the difference is at 16 cm H2O representing the increased airway resistance due to bronchospasm.

What is the most likely explanation of the increased plateau pressure in this asthmatic patient?

0%Pneumonia
0%Pneumothorax
0%AutoPEEP
0%Lung collapse

You can vote for more than one answer.

What would you do next to confirm your diagnosis?

Dec 23, 2023

Here is a screenshot of the ventilator waveforms of the pressure, flow, and volume over time in this patient prior the the inspiratory and expiratory hold.

@Everyone

Mazen Kherallah

December 6, 2023

65 year-old male with acute respiratory failure secondary to pulmonary edema who was intubated and placed on mechanical ventilation. His course was complicated with left parietal occipital and temporal infarction. The following graphs have been observed;