[Show abstract][Hide abstract] ABSTRACT: In the last 2 years, several reports have dealt with recruitment/positive end-expiratory pressure (PEEP) selection. Most of them confirm previous results and few add new information.
It has been definitely confirmed that opening pressures are different throughout the acute respiratory distress syndrome lung parenchyma, ranging from 5-10 up to 30-40 cmH2O. The highest opening pressures are required to open the most dependent lung regions. It has been found that in 2 s, most of the recruitable lung regions may be open when a proper pressure is applied. The best way to assess recruitment is computed tomography scanning, whereas lung mechanics are a reasonable bedside surrogate. Impedance tomography has been increasingly tested, whereas gas exchange is the less reliable indicator of recruitment. A large outcome study showed that higher PEEP might provide survival benefit in a subgroup of more severe patients as compared with lower PEEP. To set PEEP in each individual patient, the use of the expiratory limb of the pressure-volume curve has been suggested. Setting PEEP according to transpulmonary pressure has a robust physiological background, although it requires confirmatory study.
Indiscriminate application of recruitment maneuver in unselected acute respiratory distress syndrome population does not provide benefits. However, in the most severe patients, recruitment maneuver has to be considered and higher PEEP applied. To individualize PEEP, the expiratory phase has to be considered, and the esophageal pressure measurement to compute the transpulmonary pressure should be progressively introduced in clinical practice.
Current opinion in critical care 12/2009; 16(1):39-44. · 2.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To study and compare the relationship between end-expiratory lung volume (EELV) and changes in end-expiratory lung impedance (EELI) measured with electrical impedance tomography (EIT) at the basal part of the lung at different PEEP levels in a mixed ICU population.
End-expiratory lung volume, EELI and tidal impedance variation were determined at four PEEP levels (15-10-5-0 cm H2O) in 25 ventilated ICU patients. The tidal impedance variation and tidal volume at 5 cm H2O PEEP were used to calculate change in impedance per ml; this ratio was then used to calculate change in lung volume from change in EELI. To evaluate repeatability, EELV was measured in quadruplicate in five additional patients.
There was a significant but relatively low correlation (r = 0.79; R2 = 0.62) and moderate agreement (bias 194 ml, SD 323 ml) between DeltaEELV and change in lung volume calculated from the DeltaEELI. The ratio of tidal impedance variation and tidal volume differed between patients and also varied at different PEEP levels. Good agreement was found between repeated EELV measurements and washin/washout of a simulated nitrogen washout technique.
During a PEEP trial, the assumption of a linear relationship between change in global tidal impedance and tidal volume cannot be used to calculate EELV when impedance is measured at only one thoracic level just above the diaphragm.
European Journal of Intensive Care Medicine 07/2009; 35(8):1362-7. · 5.17 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: It has become clear that mechanical ventilation itself can cause damage to the lung in critically ill patients, also known as ventilator-induced lung injury (VILI). Insight into the mechanisms of VILI has learned that a compromise must be found between positive end-expiratory pressure (PEEP) induced alveolar recruitment and prevention of hyperinflation. Therefore, there is a need for clinicians to optimize the PEEP settings for the individual patient at the bedside. In this review, we will discuss several lung-monitoring techniques to improve patient ventilator settings.
Recently, new monitoring tools like electrical impedance tomography (EIT), vibration response imaging, respiratory inductive plethysmography and functional residual capacity (FRC) have been (re-)introduced in our ICU. Nowadays, FRC can be measured without the use of tracer gases and without disconnection from the ventilator. EIT is another noninvasive bedside monitoring tool that provides regional ventilation distribution images and can be used for qualitative and quantitative assessment of regional change in ventilation after a ventilator change. These new noninvasive techniques are discussed and seem promising to help clinicians to improve their ventilator settings in the individual patient at the bedside.
In conclusion, both FRC and EIT are promising clinical monitoring systems but clinical studies are needed to prove whether these monitors help the clinician toward effective and better ventilator management.
Current opinion in critical care 04/2012; 18(3):261-6. · 2.67 Impact Factor
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