Assessing Respiratory Variability During Mechanical Ventilation in Acute Lung Injury (ALI)
| Status: | Withdrawn |
|---|---|
| Conditions: | Hospital, Pulmonary |
| Therapuetic Areas: | Pulmonary / Respiratory Diseases, Other |
| Healthy: | No |
| Age Range: | 18 - Any |
| Updated: | 4/21/2016 |
| Start Date: | March 2010 |
| End Date: | March 2016 |
Assessing Respiratory Variability During Mechanical Ventilation in Acute Lung Injury
Healthy biological systems are characterized by a normal range of "variability" in organ
function. For example, many studies of heart rate clearly document that loss of the normal
level of intrinsic, beat-to-beat variability in heart rate is associated with poor prognosis
and early death.
Unlike the heart, little is known about patterns of respiratory variability in illness. What
is known is that, like the heart, healthy subjects have a specific range of variability in
breath- to-breath depth and timing. Additionally, in animal models, ventilator strategies
that re-introduce normal variability to the breathing pattern significantly reduce
ventilator-associated lung injury.
Critically ill patients requiring mechanical ventilation offer an opportunity to observe and
analyze respiratory patterns in a completely non-invasive manner. Current mechanical
ventilators produce real-time output of respiratory tracings that can analyzed for
variability.
The investigators propose to non-invasively record these tracings from patients ventilated
in the intensive care units for mathematical variability analysis. The purpose of these
pilot analyses are to: (1) demonstrate the range of respiratory variability present in the
mechanically ve ventilated critically ill and (2) demonstrate the ventilator modality that
delivers or permits the closest approximation to previously described beneficial or normal
levels of variability. Future studies will use this pilot data in order to determine if the
observed patterns of respiratory variability in mechanically ventilated critically ill
subjects have prognostic or therapeutic implications.
function. For example, many studies of heart rate clearly document that loss of the normal
level of intrinsic, beat-to-beat variability in heart rate is associated with poor prognosis
and early death.
Unlike the heart, little is known about patterns of respiratory variability in illness. What
is known is that, like the heart, healthy subjects have a specific range of variability in
breath- to-breath depth and timing. Additionally, in animal models, ventilator strategies
that re-introduce normal variability to the breathing pattern significantly reduce
ventilator-associated lung injury.
Critically ill patients requiring mechanical ventilation offer an opportunity to observe and
analyze respiratory patterns in a completely non-invasive manner. Current mechanical
ventilators produce real-time output of respiratory tracings that can analyzed for
variability.
The investigators propose to non-invasively record these tracings from patients ventilated
in the intensive care units for mathematical variability analysis. The purpose of these
pilot analyses are to: (1) demonstrate the range of respiratory variability present in the
mechanically ve ventilated critically ill and (2) demonstrate the ventilator modality that
delivers or permits the closest approximation to previously described beneficial or normal
levels of variability. Future studies will use this pilot data in order to determine if the
observed patterns of respiratory variability in mechanically ventilated critically ill
subjects have prognostic or therapeutic implications.
Different modes of mechanical ventilation allow different levels of patient control of the
respiratory pattern. For example, the most common mode of ventilation, called volume
control, gives very little control to the patient in the amount of air taken for each
breath. Other modes, such as pressure control, pressure regulated volume control and
pressure support, allow more patient control of the volume of air delivered by the
ventilator. Newer modes, such as airway pressure release ventilation (APRV), allow
completely spontaneous patient respirations. All of these modes allow at least some patient
control of respiratory rates.
Studies of natural breathing by healthy subjects have shown normal levels of variability in
respiratory rate and tidal volume.1 Variability in physiological processes has been
associated with health and the loss of variability can presage the onset of illness. For
example, normal humans exposed to LPS (lipopolysaccharide-the potent immune-stimulating cell
wall component of bacteria) lose their normal respiratory variability. Thus, physiological
variability may represent a "hidden vital sign," the monitoring of which may herald
important clinical events. Additionally, re-establishing normal levels of variability has
therapeutic benefits in animal models. 2
The variability in respiratory patterns in ill patients has not been well studied. For
example, it is currently unclear if critical illness results in deviations from normal
variability patterns, if ventilator modes allowing increasing patient control of respiration
allow patients to attain greater normalcy of respiratory variability, or if deviations from
normal respiratory patterns while on ventilator modes which allow for increased levels of
spontaneous breathing have prognostic implications.
The purpose of this pilot study is to record respiratory patterns from the ventilators of
patients receiving various modes of mechanical ventilation in order to quantify and compare
levels of respiratory variability associated with each mode. Our hypothesis is that APRV, a
mode that allows spontaneous respiration, will be associated with respiratory variability
patterns that most closely approximate that of normal subjects.
We hope that data derived from this study will inform future observational studies
correlating respiratory variability during mechanical ventilation with severity of illness
and prognosis.
respiratory pattern. For example, the most common mode of ventilation, called volume
control, gives very little control to the patient in the amount of air taken for each
breath. Other modes, such as pressure control, pressure regulated volume control and
pressure support, allow more patient control of the volume of air delivered by the
ventilator. Newer modes, such as airway pressure release ventilation (APRV), allow
completely spontaneous patient respirations. All of these modes allow at least some patient
control of respiratory rates.
Studies of natural breathing by healthy subjects have shown normal levels of variability in
respiratory rate and tidal volume.1 Variability in physiological processes has been
associated with health and the loss of variability can presage the onset of illness. For
example, normal humans exposed to LPS (lipopolysaccharide-the potent immune-stimulating cell
wall component of bacteria) lose their normal respiratory variability. Thus, physiological
variability may represent a "hidden vital sign," the monitoring of which may herald
important clinical events. Additionally, re-establishing normal levels of variability has
therapeutic benefits in animal models. 2
The variability in respiratory patterns in ill patients has not been well studied. For
example, it is currently unclear if critical illness results in deviations from normal
variability patterns, if ventilator modes allowing increasing patient control of respiration
allow patients to attain greater normalcy of respiratory variability, or if deviations from
normal respiratory patterns while on ventilator modes which allow for increased levels of
spontaneous breathing have prognostic implications.
The purpose of this pilot study is to record respiratory patterns from the ventilators of
patients receiving various modes of mechanical ventilation in order to quantify and compare
levels of respiratory variability associated with each mode. Our hypothesis is that APRV, a
mode that allows spontaneous respiration, will be associated with respiratory variability
patterns that most closely approximate that of normal subjects.
We hope that data derived from this study will inform future observational studies
correlating respiratory variability during mechanical ventilation with severity of illness
and prognosis.
Inclusion Criteria:
- Age > or equal to 18.
- Requires mechanical ventilation.
- Admitted to surgical, medical, or coronary critical care unit
- Triggering ventilator above set rate
- Meets American European consensus definition of acute lung injury: PaO2/FiO2 ratio
<300 or SaO2/FiO2 ratio<315; bilateral infiltrates on chest x-ray (CXR); no
congestive heart failure (CHF).
Exclusion Criteria:
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