Vertical Positioning in ARDS?
November 1, 2006 4 minutes read
Vertical Positioning in ARDS?
Abstract & Commentary
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: Moving patients with ARDS from supine into a quasi-vertical position (head and upper body elevated 45 degrees, legs lowered 45 degrees) for 1 hour was well tolerated and was associated with physiologic improvement (improved arterial oxygenation and evidence for increased lung recruitment) in two-thirds of them.
Source: Richard JC, et al. Effects of vertical positioning on gas exchange and lung volumes in acute respiratory distress syndrome. Intensive Care Med. 2006;32:1623-1626.
Studies using computed tomography have shown that patients with the acute respiratory distress syndrome (ARDS) typically have a cephalocaudal gradient in the distribution of lung density, with the greatest density (and collapse) in the lung bases adjacent to the diaphragm. Changing a patient's body position from supine to prone is usually followed by an improvement in arterial oxygenation, at least temporarily, thought to be due in part to increases in effective ventilation at the lung bases. At Henri Mondor Hospital in Creteil, France, Richard and colleagues performed this prospective observational study in patients with ARDS to determine whether moving them into a quasi-vertical position would improve gas exchange and also be tolerated physiologically.
Patients were first studied for 1 hour in the supine position, with determination of arterial blood gases and a pressure-volume curve using the oscillating low-flow inflation technique. They were then "verticalized" for 1 hr, all measurements were repeated, and they were returned to the supine position. Quasi-vertical positioning was achieved first by raising the head and upper body by 45 degrees, and then by lowering the portion of the bed supporting the legs by 45 degrees. Inspired and expired tidal volumes were measured continuously during the switch from supine to vertical and from vertical to supine positions, in order to determine changes in end-expiratory lung volume ( EELV). The study was to be terminated if desaturation (> 10% decrease in SpO2), hypotension (> 20% decrease in mean arterial pressure), or tachycardia (> 20% increase in heart rate) occurred.
The 16 consecutive patients ranged in age from 18 to 74 years, and had ARDS associated with pneumonia (7 patients), sepsis (6), aspiration (3), pancreatitis (1), and transfusion-related acute lung injury (1). Ten of them were studied in the first 3 days of ARDS, although others were evaluated as late as day 9; they had substantial oxygenation deficits, with arterial PO2 94 ± 33 mm Hg on FIO2 0.50-1.00 in the supine position at the time of study.
All 16 patients tolerated the verticalization procedure without adverse effects. Mean arterial PO2 increased from 94 ± 33 to 142 ± 49 mm Hg on moving from the supine to the quasi-vertical position. PO2 increased by 40% or more in 11 (69%) patients, who were designated by a priori criteria as "responders," and did not change or decreased (from +12% to -24% of baseline) in the other 5. Among the "responders," the exhaled volume at 20 cm H2O above baseline PEEP (designated vol 20) was greater in the quasi-vertical than in the supine position (751 ± 246 M: vs 519 ± 285 mL; P < 0.0033), suggesting that lung recruitment occurred concomitantly with the improvement in oxygenation. This exhaled volume did not change in the 5 "non-responders" (655 ± 331 vs 663 ± 325 mL; P = 0.5).
The authors conclude that verticalization is a simple technique that is well tolerated by patients with ARDS and improves oxygenation in a significant proportion of them. They provide support for a time-dependent increase in lung volume suggestive of progressive lung recruitment in the quasi-vertical position.
Commentary
This study demonstrates the short-term feasibility and apparent clinical safety of moving patients with ARDS into a 45-degree head-up, 45-degree legs-down (quasi-vertical) position. It also shows that oxygenation improved in two-thirds of them, with evidence for lung recruitment in the vertical position that was not found in the oxygenation non-responders. After the success of this pilot study, the authors conclude that further investigation into the possible role of "verticalization" in managing patients with ARDS is warranted.
The on-line supplement to this brief report contains further clinical information about the protocol and the patients studied, and features a photograph of a "verticalized" patient in the authors' unit. Although when I first read the paper the position sounded a bit extreme, the photo is reassuring, as is the information that none of the 16 patients in whom it was tried for the study experienced any adverse effects. This should not be surprising, since elevation of the head of the bed by 45 degrees has become accepted practice, and lowering the legs simply extends this process. In describing their experimental procedure, the authors were careful to state that, in "verticalizing" a patient, the head and trunk were first elevated, and then the legs were lowered; this sequence was reversed when the patient was returned to the supine position.
The big question is whether this maneuver is likely to make any overall difference in managing patients with ARDS. The literature is now replete with studies of interventions producing short-term improvement in oxygenation that have been found to have either no beneficial effect (as with inhaled nitric oxide and prone positioning), or a definite negative effect (tidal volumes of 12 mL/kg compared with 6 mL/kg), with respect to survival and other patient-relevant outcomes. Although the findings of Richard et al are definitely intriguing, we should await the results of a properly-designed clinical trial before adding "verticalization" to the management regimen for our patients with ARDS.
Studies using computed tomography have shown that patients with the acute respiratory distress syndrome (ARDS) typically have a cephalocaudal gradient in the distribution of lung density, with the greatest density (and collapse) in the lung bases adjacent to the diaphragm.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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