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Practical assessment of respiratory mechanics.
| Content Provider | Semantic Scholar |
|---|---|
| Author | Stenqvist, Ola |
| Copyright Year | 2003 |
| Abstract | More than 30 years after its ®rst description, mortality associated with the acute respiratory distress syndrome (ARDS) is still great, with reported rates between 30 and 60%. The range in mortality is partly because of the loose de®nition of both ARDS and acute lung injury (ALI), based on bilateral lung in®ltrates on X-ray, a left ventricular ®lling pressure <18 mm Hg and a PaO2/FIO2 of <300 mm Hg (ALI) or <200 mm Hg (ARDS). No factors relating to lung mechanics are used in these de®nitions. Use of PEEP can easily move the patient from ARDS to ALI or even out of the de®nition completely. The vagueness of the de®nition is also indicated when mortality is the same in ALI and ARDS, not related to ventilator settings. 50 However, Amato and colleagues showed that a `protective' form of ventilation, in contrast to `normal' ventilator treatment, reduced mortality from 71 to 38% in ARDS, and the ARDSNetwork study found that mortality decreased from 40 to 31% when tidal volumes were decreased from 12 to 6 ml kg. It may be argued that a tidal value of 12 ml kg is not normal, and these studies may only show that the use of large tidal volumes is harmful, as seen in the study of Amato and colleagues, in which the control group mortality was very high (71%), rather than small tidal volumes being protective. A link between lung mechanics and morbidity and mortality was suspected in 1998, and in 1999 Ranieri and colleagues reported that in ̄ammatory markers in lung lavage ̄uid and blood were less with a protective ventilatory strategy and that the risk of developing organ failure was reduced. 66 The concept of ventilator-induced lung injury is well established. Lung injury can cause a systemic in ̄ammatory reaction leading to multiple organ failure and death in patients with ARDS. Despite the clear link between lung mechanics and outcome in ALI and ARDS, ventilator settings are normally based on blood gases rather than measurements of lung mechanics. Rarely is the gap between research and clinical practice as wide as in the assessment of lung mechanics. In research, static measurements are considered ideal and the ventilator settings are supposed to be made on this basis, i.e. endexpiratory pressure should be above the lower in ̄ection point and tidal volume below the upper in ̄ection point on the static pressure±volume curve to avoid cyclic collapse, reopening of alveoli and overstretching. In clinical practice, however, lung mechanics are assessed during ventilation so that pressure measurements are affected by the resistance of the endotracheal tube. At best, the ventilation is set with an end-inspiratory pause giving semistatic conditions, so that an adequate plateau pressure indicates the maximal alveolar pressure. Intermittent application of a prolonged hold in expiration gives information about intrinsic PEEP. The discrepancy between the static methods used for research and clinical reality and the dynamic measurements of lung mechanics raises the question of whether static measurements are truly superior to dynamic measurements, if the latter could be obtained in such a way that the effects of endotracheal tube and airway resistance were minimized. |
| Starting Page | 92 |
| Ending Page | 105 |
| Page Count | 14 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://oup.silverchair-cdn.com/oup/backfile/Content_public/Journal/bja/91/1/10.1093/bja/aeg141/2/aeg141.pdf?Expires=1492529952&Key-Pair-Id=APKAIUCZBIA4LVPAVW3Q&Signature=CazTJMVcwzYWE7-a5oH~O-DMZv9EyyqXQ~LPzxaziEG-8-DuJj8obgE6sBaLzgtH40pOndOI08hfEYNDIlQWJekV0~6XkRm1CkbodLH~AXc6wDs94M44OdIqaZTj48nh1gOkY0jwAeXSCsKRBFc8Iw9Bi5nNk0JV1J~Ys5Y9pUrUxOvvq5NzyGGR9OjwaaBQKuaFpzwjIguNzQIMJmerV~WU9wHQmtF9Xl0z-m~quRtMb1nbN4Z8f~pf9u~1eDuQyHzznlD3sZdvRxx08ewgeJqHzxGbuTQyaFmT2YxpxY1dObXphb5ymCMGi-Oix910RXiTXv9vBmrnN1f9zoAL0w__ |
| PubMed reference number | 12821569v1 |
| Volume Number | 91 |
| Issue Number | 1 |
| Journal | British journal of anaesthesia |
| Language | English |
| Access Restriction | Open |
| Subject Keyword | Acute Lung Injury Alveolus Bronchoalveolar Lavage Cessation of life Expiration, function Gases Inspiration function Irrigation Lung diseases Mandibular right second molar tooth Mercury Morbidity - disease rate Multiple Organ Failure Patients Respiration Respiratory Distress Syndrome, Adult Respiratory Mechanics Structure of parenchyma of lung Ventilator - respiratory equipment |
| Content Type | Text |
| Resource Type | Article |
