The purposes of our study are to: 1) determine the incidence of paradoxical response tochest wall loading in mechanically ventilated patients; 2) identify sub-populations inwhich it is most likely to occur (e.g., severe ARDS); and 3) standard the bedsideprocedure for demonstrating this physiology.
Mechanical ventilation can be a life-saving intervention for patients with respiratory
failure, but the acutely injured lung is vulnerable to further damage if positive
pressure ventilation is not employed judiciously. "Lung protective ventilation"
encompasses a group of practices intended to minimize ventilator-induced lung injury
(VILI) and includes the delivery of low tidal volumes (to minimize dynamic lung strain)
and the prevention of injuriously high airway pressures (to minimize lung stress). The
prone position, which compresses (or "loads") the chest wall, more evenly distributes
volume and pressure, mitigates the damaging effects of stress/strain, and improves
clinical outcomes in patients with severe respiratory failure from adult respiratory
distress syndrome (ARDS).
Chest wall loading would not be expected to produce these beneficial effects in the
supine position-quite the opposite; it usually results in net volume loss and higher
airway pressures in response to an unchanging tidal volume. A paradoxical response to
chest wall loading, leading to decreased airway pressures, however, was recently reported
in a group of patients with advanced lung disease secondary to COVID-19. In this cohort,
a paradoxical decrease in airway pressures was elicited during a brief period of manual
compression of the abdomen.
This maneuver, which is non-invasive, free of cost, and gives real-time information, may
have important diagnostic (and potentially therapeutic) implications for ventilator
management in patients with respiratory failure.
Diagnostic Test: Manual loading of the chest wall
The chest wall will be loaded by either compression of the abdominal wall, compression of
the lumbar spine, or compression of the sternum.
Inclusion Criteria: Non-surgical patients admitted to the ICU at Regions Hospital (St.
Paul, MN) or Methodist Hospital (St. Louis Park, MN), receiving mechanical ventilation
for any reason, and breathe passively during mechanical ventilation
Exclusion Criteria:
1. Age < 18 years old
2. Pregnancy at the time of their inclusionary hospitalization
3. Recent (< 30 days) abdominal or chest wall surgery (including spine)
4. Recent (< 30 days) abdominal or chest wall trauma (including spine)
5. Traumatic brain injury, intracranial bleed, or recent neurologic surgery
6. Family member or representative not available to provide informed consent
7. Not passive while receiving mechanical ventilation support
8. Hemodynamic instability
Regions Hospital
Saint Paul 5045360, Minnesota 5037779, United States
John Selickman, MD, Principal Investigator
University of Minnesota