A spontaneous breathing trial is a test for patients on
mechanical ventilation
Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move air ...
, before they can be weaned from the
ventilator
A ventilator is a piece of medical technology that provides mechanical ventilation by moving breathable air into and out of the lungs, to deliver breaths to a patient who is physically unable to breathe, or breathing insufficiently. Ventilators ...
, i.e. return to normal breathing. The weaning process depends closely on the patient's pathology, but the final common pathway to ventilator independence always includes at least one trial of spontaneous breathing. Trials of spontaneous breathing have been shown to accurately predict the success of spontaneous breathing.
[Yang K, Tobin MJ, A prospective study of indexes predicting the outcome of weaning from mechanical ventilation. N Engl J Med 1991;324:1445-1450]
Indications for trials of spontaneous breathing
*
Fraction of inspired oxygen
Fraction of inspired oxygen (''FI''O2), corrected denoted with a capital "I", is the molar or volumetric fraction of oxygen in the inhaled gas. Medical patients experiencing difficulty breathing are provided with oxygen-enriched air, which means a ...
(F
IO
2) less than 50%
*
Positive end expiratory pressure
Positive end-expiratory pressure (PEEP) is the pressure in the lungs (alveolar pressure) above atmospheric pressure (the pressure outside of the body) that exists at the end of expiration. The two types of PEEP are extrinsic PEEP (PEEP applied b ...
(PEEP) less than 8 cm water
* "Minimal vent settings"
** e.g., ratio of arterial partial pressure of oxygen to F
IO
2 (
P/F ratio) in the vicinity of 400
Valid methods
In all of the methods below, the common endpoint measurement is a
Rapid Shallow Breathing Index (Tobin Index) of less than or equal to 105. The RSBI ("Riz-bee") is simply the ratio of respiratory frequency in respirations per minute to tidal volume in liters (f/V
t). Certainly, other measures such as patient's mental status should be considered. E.g., a
Glasgow Coma Scale
The Glasgow Coma Scale (GCS) is a clinical scale used to reliably measure a person's level of consciousness after a brain injury.
The GCS assesses a person based on their ability to perform eye movements, speak, and move their body. These thre ...
score of less than 8 is an independent indication for intubation in traumatic brain injury.
* Briefly move the tubing supply from the ventilator to continuous supply oxygen ("wall oxygen")
* Reduce pressure support to 5 cm water
* Reduce continuous positive airway pressure to 5 cm water
References
{{refimprove, article, date=April 2009
Medical terminology