The Effects of Vertical Position on Gas Exchange in Patients With Respiratory Failure

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  • sponsor
    University of Chicago
Updated on 27 January 2021
hypoxic respiratory failure


The purpose of this study is to investigate how changing from a supine to upright position affects gas exchange for patients with hypoxemic respiratory failure.

The research question is: will oxygen saturation and/or partial pressure of oxygen in the blood change when a patient with hypoxemic respiratory failure moves from a supine to upright position?


Our hypothesis is that blood oxygen tension will not decrease and may even increase when a patient with respiratory failure stands up. Supine positioning often causes partial lung collapse, which results in a decreased amount of lung being available for gas exchange. In patients with Acute Respiratory Distress Syndrome (ARDS), tilting the patient up in bed has been shown to increase oxygen tension and improve lung compliance. Positional changes are sometimes used as a "rescue" intervention in patients with severe hypoxemia from ARDS. The investigators hope to conclude that severe hypoxemia should not be viewed as a contraindication to physical therapy, but rather physical therapy may be a potential intervention for patients with marginal gas exchange.

After sedative interruption, physical therapists and nursing staff will assist mechanically ventilated patients in moving to the side of the bed. They will assess the extremity strength using the MRC scale. If lower extremity strength is at least 4/5, the patient will be assisted to assume the upright position. The investigators will monitor the patient continuously and the session will be stopped at any point for

  1. Mean arterial pressure <65 B. Heart rate <40, >130 beats/min C. Respiratory rate <5, >40 breaths/ min D. Pulse oximetry <88% E. Marked ventilator dyssynchrony F. Patient distress G. New arrhythmia H. Concern for myocardial ischemia I. Concern for airway device integrity J. Endotracheal tube removal

At this point, the patient's vital signs, pulse oximetry, and measures of lung compliance will be obtained. If an arterial line is in place and there have been ventilator adjustments since the morning arterial blood gas, the investigators will draw an arterial blood gas.

The physical therapists and nursing staff will then help the patient stand up. After one minute, the investigators will record another set of vital signs, pulse oximetry, and measures of lung compliance from the mechanical ventilator. If an arterial line is in place, the investigators will draw another arterial blood gas.

The patient will then be assisted back into bed. One hour later, the investigators will record the patient's vital signs, pulse oximetry, and measures of lung compliance from the mechanical ventilator.

Condition Respiratory Failure
Treatment Standing
Clinical Study IdentifierNCT01705119
SponsorUniversity of Chicago
Last Modified on27 January 2021


Yes No Not Sure

Inclusion Criteria

Patients aged 18 years who are mechanically ventilated
An oxygen saturation of 88-94% or an arterial line

Exclusion Criteria

Mean arterial pressure <65
Heart rate < 40 or > 130 beats/min
Respiratory rate < 5 or > 40 breaths/min
Pulse oximetry < 88%
Evidence of elevated intracranial pressure
Active gastrointestinal blood loss
Active myocardial ischemia
Actively undergoing a procedure
Patient agitation requiring increased sedative administration in the last 30 mins
Insecure airway (device)
The patient was not ambulatory prior to hospitalization
The patient's body habitus and/or mental status make it unsafe to stand up
The patient has been placed on strict bed rest by the treating physicians
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