Optimisation of positive end-expiratory pressure by forced oscillation technique in a lavage model of acute lung injury.
Summary of "Optimisation of positive end-expiratory pressure by forced oscillation technique in a lavage model of acute lung injury."
PURPOSE:
We evaluated whether oscillatory compliance (C(X5)) measured by forced oscillation technique (FOT) at 5 Hz may be useful for positive end-expiratory pressure (PEEP) optimisation.
METHODS:
We studied seven pigs in which lung injury was induced by broncho-alveolar lavage. The animals were ventilated in volume control mode with a tidal volume of 6 ml/kg. Forced oscillations were superimposed on the ventilation waveform for the assessment of respiratory mechanics. PEEP was increased from 0 to 24 cmH(2)O in steps of 4 cmH(2)O and subsequently decreased from 24 to 0 in steps of 2 cmH(2)O. At each 8-min step, a CT scan was acquired during an end-expiratory hold, and blood gas analysis was performed. C(X5) was monitored continuously, and data relative to the expiratory hold were selected and averaged for comparison with CT and oxygenation.
RESULTS:
Open lung PEEP (PEEP(ol)) was defined as the level of PEEP corresponding to the maximum value of C(X5) on the decremental limb of the PEEP trial. PEEP(ol) was on average 13.4 (±1.0) cmH(2)O. For higher levels of PEEP, there were no significant changes in the amount of non-aerated tissue (V(tissNA)%). In contrast, when PEEP was reduced below PEEP(ol), V(tissNA)% dramatically increased. PEEP(ol) was able to prevent a 5% drop in V(tissNA)% with 100% sensitivity and 92% specificity. At PEEP(ol) V(tissNA)% was significantly lower than at the corresponding PEEP level on the incremental limb.
CONCLUSIONS:
The assessment of C(X5) allowed the definition of PEEP(ol) to be in agreement with CT data. Thus, FOT measurements of C(X5) may provide a non-invasive bedside tool for PEEP titration.
Affiliation
Dipartimento di Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milan, Italy, raffaele.dellaca@polimi.it.
Journal Details
This article was published in the following journal.
Name: Intensive care medicine
ISSN: 1432-1238
Pages:
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21455750
- DOI: http://dx.doi.org/10.1007/s00134-011-2211-7
Medical and Biotech [MESH] Definitions
Positive-pressure Respiration, Intrinsic
Non-therapeutic positive end-expiratory pressure occurring frequently in patients with severe airway obstruction. It can appear with or without the administration of external positive end-expiratory pressure (POSITIVE-PRESSURE RESPIRATION). It presents an important load on the inspiratory muscles which are operating at a mechanical disadvantage due to hyperinflation. Auto-PEEP may cause profound hypotension that should be treated by intravascular volume expansion, increasing the time for expiration, and/or changing from assist mode to intermittent mandatory ventilation mode. (From Harrison's Principles of Internal Medicine, 12th ed, p1127)
Forced Expiratory Flow Rates
The rate of airflow measured during a FORCED VITAL CAPACITY determination.
Forced Expiratory Volume
Measure of the maximum amount of air that can be expelled in a given number of seconds during a FORCED VITAL CAPACITY determination . It is usually given as FEV followed by a subscript indicating the number of seconds over which the measurement is made, although it is sometimes given as a percentage of forced vital capacity.
Valsalva Maneuver
Forced expiratory effort against a closed GLOTTIS.
Maximal Expiratory Flow-volume Curves
Curves depicting MAXIMAL EXPIRATORY FLOW RATE, in liters/second, versus lung inflation, in liters or percentage of lung capacity, during a FORCED VITAL CAPACITY determination. Common abbreviation is MEFV.
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