Dynamics of re-expansion of atelectasis during general anaesthesia

Rothen, Hans Ulrich; Neumann, Peter; Berglund, Johan; Valtysson, Johann; Magnusson, Anders; Hedenstierna, Göran

doi:10.1093/bja/82.4.551

Cited by 197 publications

(141 citation statements)

References 29 publications

(32 reference statements)

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“…Studies have examined the peak pressure and duration of a DI required to completely overcome the atelectasis encountered in normal subjects during general anesthesia (29,30). Still other studies utilizing computed tomography of the chest have demonstrated lasting improvements after RMs, again in healthy human subjects during general anesthesia (31).…”

Section: Discussionmentioning

confidence: 99%

Transient mechanical benefits of a deep inflation in the injured mouse lung

Allen

Lundblad

Parsons

et al. 2002

Journal of Applied Physiology

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Allen, Gilman, Lennart K. A. Lundblad, Polly Parsons, and Jason H. T. Bates. Transient mechanical benefits of a deep inflation in the injured mouse lung. J Appl Physiol 93: 1709-1715. First published July 12, 2002 10.1152/japplphysiol.00473.2002The lasting effects of a recruitment maneuver (RM) in the injured lung are not well characterized. We speculated that the reduction in respiratory elastance (H) after a deep inflation (DI) is transient in nature and should be sustained longer at higher positive end-expiratory pressure (PEEP). Thirteen ventilated mice were given 2 DIs at various levels of PEEP before and after saline lavage. Forced oscillations were used to measure H periodically over 7 min after the DIs. Time constants ( ) were estimated for the post-DI recovery in H. Values for before lavage (80-115 s) were reduced after lavage (13-30 s) at all levels of PEEP (P ϭ 0.0001). PEEP did not significantly influence before or after lavage. The plateau level and total recovery in H after a DI were significantly influenced by PEEP and lavage (P Ͻ 0.0001). Our results suggest that for a DI to be beneficial in the injured mouse lung, it may have to be applied several times a minute. atelectasis; acute lung injury; recruitment; elastance; positive-pressure respiration PHYSICIANS HAVE KNOWN for a long time that atelectasis plays a pivotal role in the development of hypoxemia during mechanical ventilation, both in general anesthesia for routine surgery and in various instances of acute lung injury. Recent practice has now moved toward the use of lower tidal volumes (VT) in patients with acute lung injury and acute respiratory distress syndrome (ARDS) after two important studies demonstrated lower mortality outcomes by using this strategy (1, 1a). However, because of the progressive alveolar derecruitment that is often encountered with the use of lower VT (27), there has been a renewed interest in the use of recruitment maneuvers (RMs) as a means of reopening these regions of atelectasis. Many studies have demonstrated improvement in oxygenation, respiratory system compliance, and even lung volume after sustained or deep inflations (DIs) in many different scenarios (3-5, 17, 18, 26, 28), but some of these same studies were unable to show any lasting improvement when RMs were delivered during conventional positive pressure ventilation (4,18,25).These apparently conflicting results may be explained by the different experimental situations involved, as the effect of a RM is likely to depend on the size and duration of the inflation, the mode of ventilation in which the inflation is delivered, and the level of positive end-expiratory pressure (PEEP) employed. Furthermore, if the effects of a RM are transient, then its apparent benefits will depend on when they are measured. Different researchers have measured the effects of a RM at different time points after its administration (3,4,17,26,28), yet there has been little attempt to characterize the rate at which the benefits of a RM are lost in the period immediately after ...

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Section: Discussionmentioning

confidence: 99%

Transient mechanical benefits of a deep inflation in the injured mouse lung

Allen

Lundblad

Parsons

et al. 2002

Journal of Applied Physiology

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“….............................................................................................................................................................................................................. ................................................................................................................................................................................................................... ventilatory cycle, the extent depending on the relationship between the pulmonary condition and the ventilator setting [11,17,26,29,48]. Lung consolidation in the ICU is not only caused by high F i O 2 and gravitational forces as during anaesthesia, but also by surfactant dysfunction and alveolar flooding due to an altered vascular barrier [49,50] [12,[51][52][53][54][55][56].…”

Section: Human Studiesmentioning

confidence: 99%

Lung recruitment during mechanical positive pressure ventilation in the PICU: what can be learned from the literature?

Halbertsma¹,

Hoeven

2005

Anaesthesia

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Summary A literature review was conducted to assess the evidence for recruitment manoeuvres used in conventional mechanical positive pressure ventilation. A total of 61 studies on recruitment manoeuvres were identified: 13 experimental, 31 ICU, 6 PICU and 12 anaesthesia studies. Recruitment appears to be a continuous process during inspiration and expiration and is determined by peak inspiratory pressure (PIP) and positive end expiratory pressure (PEEP). Single or repeated recruitment manoeuvres may result in a statistically significant increase in oxygenation; however, this is short lasting and clinically irrelevant, especially in late ARDS and pneumonia. Temporary PIP elevation may be effective but only after PEEP loss (for example disconnection and tracheal suctioning). Continuous PEEP elevation and prone positioning can increase Pao2 significantly. Adverse haemodynamic or barotrauma effects are reported in various studies. No data exist on the effect of recruitment manoeuvres on mortality, morbidity, length of stay or duration of mechanical ventilation. Although recruitment manoeuvres can improve oxygenation, they can potentially increase lung injury, which eventually determines outcome. Based on the presently available literature, prone position and sufficient PEEP as part of a lung protective ventilation strategy seem to be the safest and most effective recruitment manoeuvres. As paediatric physiology is essentially different from adult, paediatric studies are needed to determine the role of recruitment manoeuvres in the PICU.

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“…[37][38][39][40] The effectiveness of PEEP in recruiting alveolar tissue correlates with the value of the Lower Inflexion Point (LIP). 13,[40][41] A range of ventilators have software suitable to measure P-V curves. A method of determining an appropriate figure for SI was calculated by Qiu and colleagues based upon 5 X Mean Airway Pressure (MAP).…”

Section: Whose Lungs Do You Recruit?mentioning

confidence: 99%

“…Two studies have confirmed the effective use of PV loops to reflect recruitment above the LIP and below the UIP in adult populations. [41][42] However a study by Pestana and colleagues found that P-V curves rarely reflected recruitment manoeuvres in ARDS patients which they suggest limits their application in the clinical setting as a measure of recruitment efficacy or as a guide to manage ventilation. 43 Two studies caution clinicians against using inbuilt ventilator P-V software as they had significant deleterious results in their research.…”

Section: Whose Lungs Do You Recruit?mentioning

confidence: 99%