Surface forces in the lung, atelectasis, and transpulmonary pressure.

Williams, James; Tierney, Donald F.; Parker, Harold R.

doi:10.1152/jappl.1966.21.3.819

Cited by 76 publications

(35 citation statements)

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“…3). This finding contrasts with that of a much earlier study in lambs and rabbits (35), although a more recent investigation using computer tomography scanning in injured pig lungs (24) found no significant differences between values for at different levels of PEEP. However, we are not able to conclude that closure in the lung is a pressure-independent process just because does not depend on PEEP.…”

Section: Discussioncontrasting

confidence: 84%

“…In the mouse, regional differences throughout the lung due to gravity are presumably negligible. It has also been suggested that smaller animals may have a more rapid rate of loss in compliance due to the smaller surface area of their alveoli and subsequent rapid change in the proportional air-space configuration (35). Indeed, previous human studies suggest that the benefits of sustained inflations can persist as long as 40 min in normal subjects under general anesthesia (31) but not without some degree of decay over time.…”

Section: Discussionmentioning

confidence: 99%

“…Because mechanical stretch is known to stimulate secretion of surfactant by type II alveolar cells (37) and may lead to more effective dispersion of existing surfactant, an alternative mechanism is the gradual loss of surfactant from the air-liquid interface. Williams et al (35) ascribed slow changes in H entirely to this latter mechanism, whereas Horie and Hildebrandt (14) proposed that a combination of surfactant dynamics together with airway closure at low lung volumes could be responsible. With the recent interest in optimal ventilation of critically ill patients, the attention of the scientific community seems to have focused on recruitment/derecruitment as an important process in the lung (12,16,18,21,23,27,28), particularly to describe the greatly increased hysteresis of the quasi-static pressure-volume curve in lung injury (18,28).…”

Section: Discussionmentioning

confidence: 99%

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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: Discussioncontrasting

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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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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“…The critical opening pressure of collapsed lung units therefore extended well above 20 cmH 2 O. At normal surfactant function, such high opening pressures imply that the radius of the structures which open is very small [30]. Alveolar collapse rather than airway closure seems to be the main component of derecruitment as observed with computer tomography in anaesthetised and paralysed man [31].…”

Section: Discussionmentioning

confidence: 99%

Elastic properties of the lung and the chest wall in young and adult healthy pigs

Robertis¹,

Liu²,

Blomquist³

et al. 2001

Eur Respir J

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Understanding of the elastic pressure/volume (Pel/V) curve is still limited in health and disease. The aim of the present study was to elucidate the Pel/V curve and elastance of the respiratory system (ERS) lung (EL) and chest wall (ECW) in healthy pigs.Six young (20.8 kg) and seven adult (58.9 kg), anaesthetized, paralysed and ventilated pigs were studied. Pel/V curves were recorded at zero end-expiratory pressure (ZEEP) and at positive end-expiratory pressure (PEEP) up to 40 cmH 2 O with a computer controlled ventilator during an insuf¯ation at a low, constant¯ow.Pel/V curves of the respiratory system showed a complex pattern in both young and adult pigs. During the insuf¯ation, ERS decreased, increased, fell, and increased again. A second Pel/V curve recorded immediately after the ®rst one showed lower elastance and only one early fall in ERS. ECW fell over the initial segment and was then nearly stable. Difference between 1st and 2nd curves re¯ected changes in EL caused by recruitment during the 1st insuf¯ation. At PEEP, such signs of collapse and recruitment were reduced.A strong tendency to lung collapse contributes to a complex pattern of elastic pressure/volume curves. At low volumes and distending pressures the chest wall contributes signi®cantly to changes in respiratory system elastance. The elastic pressure/volume (Pel/V) curve has, during the last years, attracted increasing interest since it may offer guidance in setting ventilators in patients with adult respiratory distress syndrome. The interest has been focused on the lower in¯exion point (LIP) of the curve and its relationship to an optimal level of positive end-expiratory pressure [1±5]. The observation of an LIP at quite high pressures in healthy man has led to discussion about the nature of the LIP. The possibility that the thoracic cage might cause an in¯exion point together with or rather than recruitment of collapsed lung units has been discussed [6,7]. Furthermore, the concept that the linear segment following the LIP represents a Pel/V range at which the lung is well recruited has been challenged on the basis of theoretical and experimental studies [8±10].In young healthy pigs it has been observed that the Pel/V curve of the respiratory system showed a nonlinear and complex pattern if a recruitment manoeuvre was not performed immediately before the recording [6]. When compliance was plotted against distending pressure, two peaks were observed. This complex pattern was considered to re¯ect a tendency for airspace to collapse in a more pronounced fashion than in humans. The application of positive endexpiratory pressure (PEEP) of 4 cmH 2 O only partly prevented lung collapse. It was discussed whether the behaviour of the lungs was affected by the juvenile age of the animals. Spurred by the prospect of lung xenotransplantation with a transgenic pig as donor [11] and by an interest to further explore the nature of the Pel/V curve, the investigation was extended by partitioning respiratory system mechanics into pulmonary and chest...

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“…We also considered the possibility that the mode of ventilation increased the amount of surfactant present in a physical state which sedimented at 500 g. In this regard, if one considers factors governing particle sedimentation in a centrifugal field (19) it becomes apparent that the volume and the density of the sedimenting particle determine the velocity of the sedimentation if the density of the medium and centrifugal force remain constant. The similarity in isopycnic density between the bands in lavage material from CTV (5,22,23). In essence, a fall in alveolar surface area during expiration leads to compression of molecules in the surface lining film which is thought to cause a loss of surfactant molecules from the film.…”

mentioning

confidence: 99%