- Research Letter
- Open Access
Potential protective effects of continuous anterior chest compression in the acute respiratory distress syndrome: physiology of an illustrative case
Critical Care volume 25, Article number: 187 (2021)
To the Editor,
Continuous anterior chest compression (CACC) may have protective effects in patients with the Acute Respiratory Distress Syndrome (ARDS) by decreasing the anterior chest wall compliance, thus decreasing the anterior transpulmonary pressure and the resulting risk of overdistension  along with promoting redistribution of ventilation through the dependent regions. In some ARDS patients, we have even observed an unexpected dramatic improvement in respiratory system compliance while compressing the anterior chest wall. We herein report the physiology of an illustrative case.
A 63-year-old male renal transplant recipient with no prior respiratory history was intubated for a SARS-CoV-2 related moderate ARDS. His respiratory mechanics progressively worsened, with a respiratory system compliance below 15 mL/cmH2O, a driving pressure of 28 cmH2O and appearance of a positive stress index  despite a decrease in tidal volume at 5 ml/kg of predicted body weight and the use of a low level of PEEP (6 cmH2O). Compression of the anterior chest wall resulted in a disappearance of the stress index pattern and a significant decrease in plateau pressure, prompting further assessment.
The patient was already sedated and paralyzed, in zero degree supine, under assist-control ventilation with the following settings: tidal volume: 350 ml, respiratory rate: 35 breaths/min. We assessed the respiratory mechanics (using flow, airway and esophageal pressure, and elastic pressure–volume curves) and ventilation distribution (using electrical impedance tomography, EIT) at the basal level of PEEP (PEEP6) without or with concomitant CACC (PEEP6 + CACC), and at zero end expiratory pressure (ZEEP). The CACC was achieved by compressing a saline bag on the sternum. The pressure inside the bag was measured and maintained at 80 cmH2O by strapping a rigid plate over it following a patented method (WO2019/048774A1).
Switching from PEEP6 to ZEEP induced a disappearance of the stress index and an increase in respiratory system compliance, mainly related to an increase in regional anterior compliance (Fig. 1). However, in the meantime, EIT evidenced a derecruitment of posterior areas, and the SpO2 dropped from 97 to 85%.
As compared to PEEP6, the overall effects of PEEP6 + CACC were an increase in pulmonary and respiratory system compliance resulting in a marked decrease in plateau pressure, a slight increase in SpO2 to 98%, and a decrease in the end expiratory lung volume (Fig. 1 and 2). Regional effects of CACC were the followings:
A decrease in anterior (ventral) lung regions distension: the positive stress index pattern disappeared, the end-inspiratory transpulmonary pressure decreased and the regional lung compliance in the anterior half increased.
A recruitment of the posterior (dorsal) lung regions: the number of pixels showing positive ∆Z in the posterior half of EIT matrix increased by 10% and the regional lung compliance in the posterior half increased.
A homogenization of tidal ventilation: the ratio between ventilation distributions of the anterior and posterior halves went from 60%/40% to 50%/50%.
No noticeable hemodynamic variation was observed.
The dramatic increase in respiratory system compliance during CACC in this ARDS patient may result from several combined mechanisms: 1-In the part of the lung already aerated but subject to intra-tidal overdistension, the noticeable decrease in the end expiratory lung volume resulted in a leftward shift of the pressure–volume curve below the upper inflexion point , 2-the concomitant recruitment in the posterior regions resulted in an increase in the number of aerated lung units .
Note that CACC may have affected the esophageal pressure and that EIT is useful for characterizing regional volume variations but may lack precision.
This original description prompts further exploration of the tolerance and physiological effects of CACC in ARDS patients.
Availability of data and materials
The data used and/or analysed during the current assessment are available from the corresponding author on reasonable request.
Acute respiratory distress syndrome
Continuous anterior chest compression
Electrical impedance tomography
Positive end expiratory pressure
Zero end expiratory pressure
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There was no specific funding for this work.
Ethics approval and consent to participate
Informed consent was obtained from the patient's next of kin for this report.
Consent for publication
Informed consent was obtained from the patient's next of kin for this report. The patient subsequently died.
GC reports personal fees from Air Liquide Medical System, Medtronic and Löwenstein, outside the submitted work. AMD reports grants from Fischer Paykel, Baxter, Philips, Ferring and GSK, personal fees from Air Liquide, Baxter, Amomed, Getinge and Addmedica, outside the submitted work. ST reports no competing interest.
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Carteaux, G., Tuffet, S. & Mekontso Dessap, A. Potential protective effects of continuous anterior chest compression in the acute respiratory distress syndrome: physiology of an illustrative case. Crit Care 25, 187 (2021). https://doi.org/10.1186/s13054-021-03619-0