Respiratory Failure & Mechanical Ventilation

69 years old with anoxic encephalopathy and acute right parietal infarct after cardiac arrest. On Volume control mode of ventilation with VT of 510 breathing

What do you think?

‎‏Age/gender : 54y/o male

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📝 ‎‏ Diagnosed as ARDS, H1N1 positive, later found to have ICH

‎‏ 🗂️ Medical history : Nil

🏋🏻‍♂️ ‎‏Adm wt.60kg, ht.168cm.

‎‏ Current wt: 54.0

How do you explain the the drop in the pressure indicated by the white arrows on the pressure/time scalar?

@Everyone

Please answer the question and provide your input in the comment section!

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.

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;

Please identify the abnormality and answer the following question:

65 years old with submasdive pulmonary embolism, DVT, atrial flutter, and non-ischemic cardiomyopathy. Intubated and placed on mechanical ventilation at night (A/C mode VT 500, Flow of 50, RR 22 and PEEP 5). The following was observed during the morning round:

Based on the pressure over time waveform, how would you approach this case?

Please notice the volume over time scalar as indicated by the light orange arrow and provide your feedback:

@Everyone

Please select your answer and you may provide your explanation in the comment section.

Double-triggering seen in flow and volume waveforms from volume-controlled ventilation. Continued subject effort during the second breath causes the airway pressure to drop below the trigger threshold, which initiates an additional “stacked” breath. Note the large increase in peak airway pressure caused by the stacked breath and the high peak expiratory flow following the stacked breath.

Cycling asynchrony on the ventilator assessed by expiratory muscle EMG (Transversus abdominis):

The above graph shows the relationship between the flow over time waveform and the activities of the expiratory muscles measure by EMG. The relationship of neural expiratory time to ventilator expiratory time was assessed by measuring the phase angle, expressed in degrees. If neural activity began simultaneously with the ventilator, the phase angle (0) was zero. Neural activity beginning after the offset (termination) of inflation by the ventilator resulted in a positive phase angle (60 degrees for subject 1). Neural activity beginning before the offset of inflation by the ventilator resulted in a negative phase angle (45 degrees for subject 2)

We performed an inspiratory hold and the plateau pressure is higher than the peak inspiratory pressure. How can that be explained for the patient who is not sedated.

Left image showing delayed termination (cycling) asynchrony with inspiratory time of 1 second. Middle image, inspiratory time was decreased to 0.8 and asynchrony improved. However, patient started to have double triggering as shown in the right image.

Delayed cycling (termination) indicated by early patient’s expiratory efforts!

Flow-time waveform from a patient receiving intermittent mandatory ventilation with pressure support. Large tidal volume (VT) during the mandatory breath prolongs expiratory time (lengthened time constant) that exceeds the patient’s neural timing mechanism. Additional patient efforts that fail to trigger the ventilator are evident in the expiratory flow waveform.

It illustrates the impact of large tidal volumes (VT) provided during the mandatory breaths and the impact on expiratory timing. Following the large mandatory breath, expiratory time is slightly prolonged and interferes with the patient’s internal timing mechanism, so the next inspiratory effort (seen as a sudden drop in the expiratory flow, to nearly zero) occurs prior to completion of exhalation. As in previous waveforms, this example illustrates the importance of carefully evaluating the flow waveform to identify additional patient efforts.

Flow, airway pressure (Paw), and esophageal pressure (Pes) in a patient with severe chronic obstructive pulmonary disease and ventilated with pressure support. The dotted lines indicate the beginning of inspiratory efforts that triggered the ventilator. The thin, black arrows indicate nontriggering inspiratory efforts. Notice the time delay between the beginning of inspiratory effort and ventilator triggering. Ineffective (nontriggering) efforts occurred during both mechanical inspiration and expiration. Those ineffective efforts can easily be identified on the flow waveform; ineffective efforts during mechanical inspiration abruptly increase inspiratory flow, whereas during expiration they result in an abrupt decrease in expiratory flow (open arrows in the flow waveform). The set respiratory frequency is 12 breaths/min, but the patient is making 33 inspiratory efforts per minute.

The second breath is an ineffective breath to trigger the ventilator as the patient’s efforts did not generate a flow to reach the trigger threshold on the ventilator setting, therefore it was wasted with minimal tidal volume!

The adequacy of flow during volume-controlled ventilation can be evaluated with the pressure-time waveform. Since the total work performed during the breath is the sum of the patient work and the ventilator work, we can evaluate the relative contributions of both by comparing the shapes of the pressure-time waveform during 2 different conditions: completely passive breathing, during which the waveform has a defined pattern based on the type of flow (constant-flow, descending-ramp, or sinusoidal) and patient-triggered breathing, during which the additional patient effort “dishes out” (ie, makes concave) the pressure waveform, relative to the amount of patient work performed. The hatched area illustrates the pressure-time product and represents the effort the patient contributed to the delivery of the breath.

Ineffective effort!

Dynamic hyperinflation syndrome (auto PEEP) on volume/flow loop, note the persistent flow at the end of expiration and the tapped volume indicated by the yellow square.

The question is, what happens to the auto PEEP if settings on the ventilator are not corrected, does the lung continue to hyperinflate or what?