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Need your expertise

This patient is a COPD, intubated and mechanically ventilated in PS.

Looking at the esophageal pressure waveform, Peso is higher at the beginning of expiration as compared to the end of expiration.

Is it the normal elastic recoil during a passive expiration or is it an active expiration?

Thanks for your comments



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I think by the end of I-time, the inspiratory muscles have (mostly) relaxed. Hence, the Pes at the end of I-time is more reflective of the true elastic recoil pressure of the chest wall (Pel,w). This would, of course, be higher than expiratory Pes due to increase in thoracic volume during inspiration.


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Airtrapping creating iPEEP/distended lung could lead to a positive Pes during passive exhalation.

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I fully agree with Carlo Alberto: it looks like passive exhalation. At the bedside, I suggest to visualize the Pes-volume loop on the ventilator screen: as long as exhalation is passive, the expiratory Pes-volume relationship is linear and its slope is actually the chest wall elastance.

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Very nice traces and interesting aspect! I would say that the expiration was relaxed, without contraction of the expiratory muscle. It is true that it would have been nice to have the gastric pressure but the shape of the esophageal trace speaks for chest wall relaxation curve. Interestingly this happens in a patient with expiratory flow limitation, in which contraction of expiratory muscle is not able to increase the expiratoru flow and hence to decrase the end expiratory lung volume. In other words, the contraction of the expiratory muscle is useless in presence of expiratory flow limitation.

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Alberto
Alberto
Nov 19, 2018

Very interesting tracing! If it was active exhalation, I would have expected an increase of the esophageal pressure until the end of expiration (as described in Lessard et al, AJRCMM 1995).  ? Short active exhalation? I would be very interested in the experts opinion!


Also, the flow does not go back to zero at the end expiration, suspicious for iPEEP. This can also be seen at the beginning of diaphragmatic contraction (esophageal pressure deflection), where you can appreciate a negative pressure deflection that happens before flow inversion (ideally, slowing the speed of the waveform would allow us to better estimate this)

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