Prone Positioning Unloads the Right Ventricle in Severe ARDS

doi:10.1378/chest.07-1013

Chest

Volume 132, Issue 5, November 2007, Pages 1440-1446

https://doi.org/10.1378/chest.07-1013 Get rights and content

Background

Despite airway pressure limitation, acute cor pulmonale persists in a minority of ARDS patients. Insufficient airway pressure limitation, hypercapnia, or both may be responsible. Because prone positioning (PP) has been shown to be a safe way to reduce airway pressure and to improve alveolar ventilation, we decided to assess its effect on right ventricular (RV) pressure overload in ARDS patients.

Methods

Between January 1998 and December 2006, we studied 42 ARDS patients treated by PP to correct severe oxygenation impairment (Pao₂/fraction of inspired oxygen ratio, < 100 mm Hg). RV function was evaluated by bedside transesophageal echocardiography, before and after 18 h of prone-position ventilation. RV enlargement was measured by RV/left ventricular (LV) end-diastolic area ratio in the long axis. Septal dyskinesia was quantified by measuring short-axis systolic eccentricity of the LV.

Results

Before PP, 21 patients (50%) had acute cor pulmonale, defined by RV enlargement associated with septal dyskinesia (group 1), whereas 21 patients had a normal RV (group 2). PP was accompanied by a significant decrease in airway pressure and Paco₂. In group 1, this produced a significant decrease in mean (± SD) RV enlargement (from 0.91 ± 0.22 to 0.61 ± 0.21) after 18 h of PP (p = 0.000) and a significant reduction in mean septal dyskinesia (from 1.5 ± 0.2 to 1.1 ± 0.1) after 18 h of PP (p = 0.000).

Conclusion

In the most severe forms of ARDS, PP was an efficient means of controlling RV pressure overload.

Section snippets

Materials and Methods

Within the ARDS population treated between January 1998 and December 2006, we selected those patients meeting the following inclusion criteria: (1) patients with “severe” ARDS, leading to a Pao₂/fraction of inspired oxygen (Fio₂) ratio of < 100 mm Hg after 48 h of respiratory support with our “low-stretch” respiratory strategy; and (2) treatment by PP during the first week of respiratory support.

Results

Between January 1998 and December 2006, 144 patients meeting the ARDS criteria were treated by controlled mechanical ventilation in our eight-bed medical ICU. Transesophageal echocardiographic evaluation, which was performed during the first 48 h of respiratory support, revealed acute cor pulmonale, which was defined as RV dilatation associated with septal dyskinesia, in 32 patients. The crude incidence of this complication was thus 22%. The respective incidence of this complication in the

Discussion

When measured during a period of no flow, tracheal pressure in a mechanically ventilated patient reflects alveolar pressure. Thus, introducing an end-inspiratory pause, which produces a plateau, permits the measurement of alveolar pressure at end-inspiration. Because airway pressure transmission to the pleural space in an ARDS patient is minor,¹⁵ alveolar pressure constitutes the major determinant of transpulmonary pressure (ie, the alveolar distending pressure). This distending pressure is

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Prone positioning (PP) is an established treatment modality for respiratory failure. After aneurysmal subarachnoid hemorrhage (aSAH), PP is rarely performed considering the risk of intracranial hypertension. The aim of this study was to analyze the effects of PP on intracranial pressure (ICP), cerebral perfusion pressure (CPP) and cerebral oxygenation following aSAH. Patients and methods: Demographic and clinical data of aSAH patients admitted over a 6-year period and treated with PP due to respiratory insufficiency were retrospectively analyzed. ICP, CPP, brain tissue oxygenation (pBrO2), respiratory parameters and ventilator settings were analyzed before and during PP.
Thirty patients receiving invasive multimodal neuromonitoring were included. Overall, 97 PP sessions were performed. Mean arterial oxygenation and pBrO2 increased significantly during PP. We found a significant increase in median ICP compared to the baseline level in supine position. No significant changes in CPP were observed. Five PP sessions had to be terminated early due to medically refractory ICP-crisis. The affected patients were younger (p = 0.02) with significantly higher baseline ICP values (p = 0.009). Baseline ICP correlates significantly (p < 0.001) with ICP 1 h (R: 0.57) and 4 h (R: 0.55) after onset of PP.
PP in aSAH patients with respiratory insufficiency is an effective therapeutic option improving arterial and global cerebral oxygenation without compromising CPP. The significant increase in ICP was moderate in most sessions. However, as some patients experience intolerable ICP crises during PP, continuous ICP-Monitoring is considered mandatory. Patients with elevated baseline ICP and reduced intracranial compliance should not be considered for PP.
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: The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

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Chest

Original ResearchCRITICAL CARE MEDICINEProne Positioning Unloads the Right Ventricle in Severe ARDS

Background

Methods

Results

Conclusion

Section snippets

Materials and Methods

Results

Discussion

J Am Coll Cardiol

Chest

Chest

Ventilation-perfusion distribution in the adult respiratory distress syndrome

Am Rev Respir Dis

What as computed tomography taught us about the acute respiratory distress syndrome?

Am J Respir Crit Care Med

Improved oxygenation in patients with acute respiratory failure: the prone position

Am Rev Respir Dis

Pulmonary hypertension in severe acute respiratory failure

N Engl J Med

Two-dimensional zechocardiographic evaluation of right ventricular size and contractility in acute respiratory failure

Crit Care Med

Echo-Doppler demonstration of acute cor pulmonale at the bedside in the medical intensive care unit

Am J Respir Crit Care Med

Low stretch ventilation strategy in acute respiratory distress syndrome: eight years of clinical experience in a single center

Crit Care Med

Optimum end-expiratory airway pressure in patients with acute lung disease

N Engl J Med

Prone position in mechanically ventilated patients with severe acute respiratory failure

Am J Respir Crit Care Med

Ability and safety of a heated humidifier to control hypercapnic acidosis in severe ARDS

Intensive Care Med

Influence of tricuspid regurgitation and vena caval backward flow in mechanically ventilated patients: a color Doppler and contrast echocardiographic study

Chest

Hemodynamic instability in sepsis: bedside assessment by Doppler echocardiography

Am Rev Respir Crit Care Med

Original Research
CRITICAL CARE MEDICINE
Prone Positioning Unloads the Right Ventricle in Severe ARDS