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Martins ARC, Ambrósio AM, Fantoni DT, Pinto ACBCF, Villamizar-Martinez LA, Soares JHN, Otsuki DA, Malbouisson LMS. Computed Tomography Assessment of Tidal Lung Overinflation in Domestic Cats Undergoing Pressure-Controlled Mechanical Ventilation During General Anesthesia. Front Vet Sci 2022; 9:842528. [PMID: 35433898 PMCID: PMC9011143 DOI: 10.3389/fvets.2022.842528] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Accepted: 03/04/2022] [Indexed: 11/22/2022] Open
Abstract
Objective This study aimed to evaluate lung overinflation at different airway inspiratory pressure levels using computed tomography in cats undergoing general anesthesia. Study Design Prospective laboratory study. Animals A group of 17 healthy male cats, aged 1.9–4.5 years and weighing 3.5 ± 0.5 kg. Methods Seventeen adult male cats were ventilated in pressure-controlled mode with airway pressure stepwise increased from 5 to 15 cmH2O in 2 cmH2O steps every 5 min and then stepwise decreased. The respiratory rate was set at 15 movements per min and end-expiratory pressure at zero (ZEEP). After 5 min in each inspiratory pressure step, a 4 s inspiratory pause was performed to obtain a thoracic juxta-diaphragmatic single slice helical CT image and to collect respiratory mechanics data and an arterial blood sample. Lung parenchyma aeration was defined as overinflated, normally-aerated, poorly-aerated, and non-aerated according to the CT attenuation number (−1,000 to −900 HU, −900 to −500 HU, −500 to −100 HU, and −100 to +100 HU, respectively). Result At 5 cmH2O airway pressure, tidal volume was 6.7± 2.2 ml kg−1, 2.1% (0.3–6.3%) of the pulmonary parenchyma was overinflated and 84.9% (77.6%−87.6%) was normally inflated. Increases in airway pressure were associated with progressive distention of the lung parenchyma. At 15 cmH2O airway pressure, tidal volume increased to 31.5± 9.9 ml kg−1 (p < 0.001), overinflated pulmonary parenchyma increased to 28.4% (21.2–30.6%) (p < 0.001), while normally inflated parenchyma decreased 57.9% (53.4–62.8%) (p < 0.001). Tidal volume and overinflated lung fraction returned to baseline when airway pressure was decreased. A progressive decrease was observed in arterial carbon dioxide partial pressure (PaCO2) and end-tidal carbon dioxide (ETCO2) when the airway pressures were increased above 9 cmH2O (p < 0.001). The increase in airway pressure promoted an elevation in pH (p < 0.001). Conclusions and Clinical Relevance Ventilation with 5 and 7 cmH2O of airway pressure prevents overinflation in healthy cats with highly compliant chest walls, despite presenting acidemia by respiratory acidosis. This fact can be controlled by increasing or decreasing respiratory rate and inspiratory time.
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Affiliation(s)
| | - Aline M. Ambrósio
- Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Denise T. Fantoni
- Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | - Ana Carolina B. C. F. Pinto
- Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo, Brazil
| | | | - João H. N. Soares
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, Davis, CA, United States
| | - Denise A. Otsuki
- Discipline of Anesthesiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil
- *Correspondence: Denise A. Otsuki
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Radiological pattern in ARDS patients: partitioned respiratory mechanics, gas exchange and lung recruitability. Ann Intensive Care 2021; 11:78. [PMID: 33999274 PMCID: PMC8128955 DOI: 10.1186/s13613-021-00870-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 05/05/2021] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The ARDS is characterized by different degrees of impairment in oxygenation and distribution of the lung disease. Two radiological patterns have been described: a focal and a diffuse one. These two patterns could present significant differences both in gas exchange and in the response to a recruitment maneuver. At the present time, it is not known if the focal and the diffuse pattern could be characterized by a difference in the lung and chest wall mechanical characteristics. Our aims were to investigate, at two levels of PEEP, if focal vs. diffuse ARDS patterns could be characterized by different lung CT characteristics, partitioned respiratory mechanics and lung recruitability. METHODS CT patterns were analyzed by two radiologists and were classified as focal or diffuse. The changes from 5 to 15 cmH2O in blood gas analysis and partitioned respiratory mechanics were analyzed. Lung CT scan was performed at 5 and 45 cmH2O of PEEP to evaluate lung recruitability. RESULTS One-hundred and ten patients showed a diffuse pattern, while 58 showed a focal pattern. At 5 cmH2O of PEEP, the driving pressure and the elastance, both the respiratory system and of the lung, were significantly higher in the diffuse pattern compared to the focal (14 [11-16] vs 11 [9-15 cmH2O; 28 [23-34] vs 21 [17-27] cmH2O/L; 22 [17-28] vs 14 [12-19] cmH2O/L). By increasing PEEP, the driving pressure and the respiratory system elastance significantly decreased in diffuse pattern, while they increased or did not change in the focal pattern (Δ15-5: - 1 [- 2 to 1] vs 0 [- 1 to 2]; - 1 [- 4 to 2] vs 1 [- 2 to 5]). At 5 cmH2O of PEEP, the diffuse pattern had a lower lung gas (743 [537-984] vs 1222 [918-1974] mL) and higher lung weight (1618 [1388-2001] vs 1222 [1059-1394] g) compared to focal pattern. The lung recruitability was significantly higher in diffuse compared to focal pattern 21% [13-29] vs 11% [6-16]. Considering the median of lung recruitability of the whole population (16.1%), the recruiters were 65% and 22% in the diffuse and focal pattern, respectively. CONCLUSIONS An early identification of lung morphology can be useful to choose the ventilatory setting. A diffuse pattern has a better response to the increase of PEEP and to the recruitment maneuver.
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Radiographic Manifestations of Diffuse Pulmonary Alveolar Derecruitment. J Thorac Imaging 2020; 34:362-366. [PMID: 30994518 DOI: 10.1097/rti.0000000000000414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Pulmonary alveolar derecruitment is a process of alveolar collapse that occurs in critically ill patients. While the entity and its physiological manifestations are described in the anesthesiology and critical care literature, the radiographic manifestations of alveolar derecruitment have not yet been thoroughly described. This phenomenon can have a similar appearance to pulmonary edema; however, patients often have severe intravascular volume depletion. As the treatment for these 2 entities is essentially contradictory, it is important to be familiar with alveolar derecruitment and consider it as a differential diagnosis when clinically appropriate.
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Cronin JN, Borges JB, Crockett DC, Farmery AD, Hedenstierna G, Larsson A, Tran MC, Camporota L, Formenti F. Dynamic single-slice CT estimates whole-lung dual-energy CT variables in pigs with and without experimental lung injury. Intensive Care Med Exp 2019; 7:59. [PMID: 31676929 PMCID: PMC6825104 DOI: 10.1186/s40635-019-0273-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/01/2019] [Indexed: 11/23/2022] Open
Abstract
Background Dynamic single-slice CT (dCT) is increasingly used to examine the intra-tidal, physiological variation in aeration and lung density in experimental lung injury. The ability of dCT to predict whole-lung values is unclear, especially for dual-energy CT (DECT) variables. Additionally, the effect of inspiration-related lung movement on CT variables has not yet been quantified. Methods Eight domestic pigs were studied under general anaesthesia, including four following saline-lavage surfactant depletion (lung injury model). DECT, dCT and whole-lung images were collected at 12 ventilatory settings. Whole-lung single energy scans images were collected during expiratory and inspiratory apnoeas at positive end-expiratory pressures from 0 to 20 cmH2O. Means and distributions of CT variables were calculated for both dCT and whole-lung images. The cranio-caudal displacement of the anatomical slice was measured from whole-lung images. Results Mean CT density and volume fractions of soft tissue, gas, iodinated blood, atelectasis, poor aeration, normal aeration and overdistension correlated between dCT and the whole lung (r2 0.75–0.94) with agreement between CT density distributions (r 0.89–0.97). Inspiration increased the matching between dCT and whole-lung values and was associated with a movement of 32% (SD 15%) of the imaged slice out of the scanner field-of-view. This effect introduced an artefactual increase in dCT mean CT density during inspiration, opposite to that caused by the underlying physiology. Conclusions Overall, dCT closely approximates whole-lung aeration and density. This approximation is improved by inspiration where a decrease in CT density and atelectasis can be interpreted as physiological rather than artefactual.
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Affiliation(s)
- John N Cronin
- Centre for Human and Applied Physiological Sciences, King's College London, London, UK
| | - João Batista Borges
- Centre for Human and Applied Physiological Sciences, King's College London, London, UK
| | | | - Andrew D Farmery
- Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK
| | - Göran Hedenstierna
- Hedenstierna Laboratory, Department of Medical Sciences, Uppsala University, Uppsala, Sweden
| | - Anders Larsson
- Hedenstierna Laboratory, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden
| | - Minh C Tran
- Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK
| | - Luigi Camporota
- Centre for Human and Applied Physiological Sciences, King's College London, London, UK.,Department of Adult Critical Care, St. Thomas' Hospital, Guy's and St. Thomas' NHS Foundation Trust, King's Health Partners, London, UK
| | - Federico Formenti
- Centre for Human and Applied Physiological Sciences, King's College London, London, UK. .,Nuffield Division of Anaesthetics, University of Oxford, Oxford, UK.
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Chiumello D, Sferrazza Papa GF, Artigas A, Bouhemad B, Grgic A, Heunks L, Markstaller K, Pellegrino GM, Pisani L, Rigau D, Schultz MJ, Sotgiu G, Spieth P, Zompatori M, Navalesi P. ERS statement on chest imaging in acute respiratory failure. Eur Respir J 2019; 54:13993003.00435-2019. [PMID: 31248958 DOI: 10.1183/13993003.00435-2019] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 05/16/2019] [Indexed: 12/17/2022]
Abstract
Chest imaging in patients with acute respiratory failure plays an important role in diagnosing, monitoring and assessing the underlying disease. The available modalities range from plain chest X-ray to computed tomography, lung ultrasound, electrical impedance tomography and positron emission tomography. Surprisingly, there are presently no clear-cut recommendations for critical care physicians regarding indications for and limitations of these different techniques.The purpose of the present European Respiratory Society (ERS) statement is to provide physicians with a comprehensive clinical review of chest imaging techniques for the assessment of patients with acute respiratory failure, based on the scientific evidence as identified by systematic searches. For each of these imaging techniques, the panel evaluated the following items: possible indications, technical aspects, qualitative and quantitative analysis of lung morphology and the potential interplay with mechanical ventilation. A systematic search of the literature was performed from inception to September 2018. A first search provided 1833 references. After evaluating the full text and discussion among the committee, 135 references were used to prepare the current statement.These chest imaging techniques allow a better assessment and understanding of the pathogenesis and pathophysiology of patients with acute respiratory failure, but have different indications and can provide additional information to each other.
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Affiliation(s)
- Davide Chiumello
- SC Anestesia e Rianimazione, Ospedale San Paolo - Polo Universitario, ASST Santi Paolo e Carlo, Milan, Italy.,Dipartimento di Scienze della Salute, Centro Ricerca Coordinata di Insufficienza Respiratoria, Università degli Studi di Milano, Milan, Italy
| | | | - Antonio Artigas
- Corporacion Sanitaria, Universitaria Parc Tauli, CIBER de Enfermedades Respiratorias Autonomous University of Barcelona, Sabadell, Spain.,Intensive Care Dept, University Hospitals Sagrado Corazon - General de Cataluna, Quiron Salud, Barcelona-Sant Cugat del Valles, Spain
| | - Belaid Bouhemad
- Service d'Anesthésie - Réanimation, Université Bourgogne - Franche Comtè, lncumr 866L, Dijon, France
| | - Aleksandar Grgic
- Dept of Nuclear Medicine, Saarland University Medical Center, Homburg, Germany
| | - Leo Heunks
- Dept of Intensive Care Medicine, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Klaus Markstaller
- Dept of Anesthesia, General Intensive Care Medicine and Pain Therapy, Medical University of Vienna, Vienna, Austria
| | - Giulia M Pellegrino
- Dipartimento di Scienze della Salute, Centro Ricerca Coordinata di Insufficienza Respiratoria, Università degli Studi di Milano, Milan, Italy.,Casa di Cura del Policlinico, Dipartimento di Scienze Neuroriabilitative, Milan, Italy
| | - Lara Pisani
- Respiratory and Critical Care Unit, Alma Mater Studiorum, University of Bologna, Sant'Orsola Malpighi Hospital, Bologna, Italy
| | | | - Marcus J Schultz
- Mahidol-Oxford Tropical Medicine Research Unit, Mahidol University, Bangkok, Thailand
| | - Giovanni Sotgiu
- Clinical Epidemiology and Medical Statistics Unit, Dept of Clinical and Experimental Medicine, University of Sassari, Sassari, Italy
| | - Peter Spieth
- Dept of Anesthesiology and Critical Care Medicine, University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.,Center for Clinical Research and Management Education, Division of Health Care Sciences, Dresden International University, Dresden, Germany
| | | | - Paolo Navalesi
- Anaesthesia and Intensive Care, Department of Medical and Surgical Sciences, University of Magna Graecia, Catanzaro, Italy
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Continuous negative abdominal distension augments recruitment of atelectatic lung*. Crit Care Med 2012; 40:1864-72. [DOI: 10.1097/ccm.0b013e318246bd6a] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Optimisation of positive end-expiratory pressure by forced oscillation technique in a lavage model of acute lung injury. Intensive Care Med 2011; 37:1021-30. [DOI: 10.1007/s00134-011-2211-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 02/10/2011] [Indexed: 10/18/2022]
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8
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Scanographic comparison of high frequency oscillation with versus without tracheal gas insufflation in acute respiratory distress syndrome. Intensive Care Med 2011; 37:990-9. [DOI: 10.1007/s00134-011-2162-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2010] [Accepted: 12/14/2010] [Indexed: 10/18/2022]
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Extrapolation from ten sections can make CT-based quantification of lung aeration more practicable. Intensive Care Med 2010; 36:1836-44. [PMID: 20689909 DOI: 10.1007/s00134-010-2014-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2010] [Accepted: 04/26/2010] [Indexed: 10/19/2022]
Abstract
PURPOSE Clinical applications of quantitative computed tomography (qCT) in patients with pulmonary opacifications are hindered by the radiation exposure and by the arduous manual image processing. We hypothesized that extrapolation from only ten thoracic CT sections will provide reliable information on the aeration of the entire lung. METHODS CTs of 72 patients with normal and 85 patients with opacified lungs were studied retrospectively. Volumes and masses of the lung and its differently aerated compartments were obtained from all CT sections. Then only the most cranial and caudal sections and a further eight evenly spaced sections between them were selected. The results from these ten sections were extrapolated to the entire lung. The agreement between both methods was assessed with Bland-Altman plots. RESULTS Median (range) total lung volume and mass were 3,738 (1,311-6,768) ml and 957 (545-3,019) g, the corresponding bias (limits of agreement) were 26 (-42 to 95) ml and 8 (-21 to 38) g, respectively. The median volumes (range) of differently aerated compartments (percentage of total lung volume) were 1 (0-54)% for the nonaerated, 5 (1-44)% for the poorly aerated, 85 (28-98)% for the normally aerated, and 4 (0-48)% for the hyperaerated subvolume. The agreement between the extrapolated results and those from all CT sections was excellent. All bias values were below 1% of the total lung volume or mass, the limits of agreement never exceeded ± 2%. CONCLUSION The extrapolation method can reduce radiation exposure and shorten the time required for qCT analysis of lung aeration.
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Holanda MA, Fortaleza SC, Alves-de-Almeida M, Winkeler GF, Reis RC, Felix JH, Lima JW, Pereira ED. Continuous Positive Airway Pressure Effects on Regional Lung Aeration in Patients With COPD. Chest 2010; 138:305-14. [DOI: 10.1378/chest.09-2850] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Pássaro CP, Silva PL, Rzezinski AF, Abrantes S, Santiago VR, Nardelli L, Santos RS, Barbosa CML, Morales MM, Zin WA, Amato MBP, Capelozzi VL, Pelosi P, Rocco PRM. Pulmonary lesion induced by low and high positive end-expiratory pressure levels during protective ventilation in experimental acute lung injury. Crit Care Med 2009; 37:1011-7. [DOI: 10.1097/ccm.0b013e3181962d85] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Helm E, Talakoub O, Grasso F, Engelberts D, Alirezaie J, Kavanagh BP, Babyn P. Use of dynamic CT in acute respiratory distress syndrome (ARDS) with comparison of positive and negative pressure ventilation. Eur Radiol 2008; 19:50-7. [DOI: 10.1007/s00330-008-1105-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Revised: 05/30/2008] [Accepted: 06/07/2008] [Indexed: 11/29/2022]
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13
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Image reconstruction affects computer tomographic assessment of lung hyperinflation. Intensive Care Med 2008; 34:2044-53. [DOI: 10.1007/s00134-008-1175-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 05/17/2008] [Indexed: 10/22/2022]
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Zambon M, Vincent JL. Mortality rates for patients with acute lung injury/ARDS have decreased over time. Chest 2008; 133:1120-7. [PMID: 18263687 DOI: 10.1378/chest.07-2134] [Citation(s) in RCA: 372] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Over the last decade, several studies have suggested that survival rates for patients with acute lung injury (ALI) or ARDS may have improved. We performed a systematic analysis of the ALI/ARDS literature to document possible trends in mortality between 1994 and 2006. METHODS We used the Medline database to select studies with the key words "acute lung injury," "ARDS," "acute respiratory failure," and "mechanical ventilation." All studies that reported mortality rates for patients with ALI/ARDS defined according to the criteria of the American European Consensus Conference were selected. We excluded studies with < 30 patients and studies limited to specific subgroups of ARDS patients such as sepsis, trauma, burns, or transfusion-related ARDS. RESULTS Seventy-two studies were included in the analysis. There was a wide variation in mortality rates among the studies (15 to 72%). The overall pooled mortality rate for all studies was 43% (95% confidence interval, 40 to 46%). Metaregression analysis suggested a significant decrease in overall mortality rates of approximately 1.1%/yr over the period analyzed (1994 to 2006). The mortality reduction was also observed for hospital but not for ICU or 28-day mortality rates. CONCLUSIONS In this literature review, the data are consistent with a reduction in mortality rates in general populations of patients with ALI/ARDS over the last 10 years.
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Affiliation(s)
- Massimo Zambon
- Department of Intensive Care, Erasme Hospital, Route de Lennik, 808, 1070 Brussels, Belgium
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Bellardine Black CL, Hoffman AM, Tsai LW, Ingenito EP, Suki B, Kaczka DW, Simon BA, Lutchen KR. Relationship between dynamic respiratory mechanics and disease heterogeneity in sheep lavage injury*. Crit Care Med 2007; 35:870-8. [PMID: 17255854 DOI: 10.1097/01.ccm.0000257331.42485.94] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Acute respiratory distress syndrome and acute lung injury are characterized by heterogeneous flooding/collapse of lung tissue. An emerging concept for managing these diseases is to set mechanical ventilation so as to minimize the impact of disease heterogeneity on lung mechanical stress and ventilation distribution. The goal of this study was to determine whether changes in lung mechanical heterogeneity with increasing positive end-expiratory pressure in an animal model of acute lung injury could be detected from the frequency responses of resistance and elastance. DESIGN Prospective, experimental study. SETTING Research laboratory at a veterinary hospital. SUBJECTS Female sheep weighing 48 +/- 2 kg. INTERVENTIONS In five saline-lavaged sheep, we acquired whole-lung computed tomography scans, oxygenation, static elastance, and dynamic respiratory resistance and elastance at end-expiratory pressure levels of 7.5-20 cm H2O. MEASUREMENTS AND MAIN RESULTS As end-expiratory pressure increased, computed tomography-determined alveolar recruitment significantly increased but was accompanied by significant alveolar overdistension at 20 cm H2O. An optimal range of end-expiratory pressures (15-17.5 cm H2O) was identified where alveolar recruitment was significantly increased without significant overdistension. This range corresponded to the end-expiratory pressure levels that maximized oxygenation, minimized peak-to-peak ventilation pressures, and minimized indexes reflective of the mechanical heterogeneity (e.g., frequency dependence of respiratory resistance and low-frequency elastance). Static elastance did not demonstrate any significant pressure dependence or reveal an optimal end-expiratory pressure level. CONCLUSIONS We conclude that dynamic mechanics are more sensitive than static mechanics in the assessment of the functional trade-off of recruitment relative to overdistension in a sheep model of lung injury. We anticipate that monitoring of dynamic respiratory resistance and elastance ventilator settings can be used to optimize ventilator management in acute lung injury.
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Carvalho ARS, Jandre FC, Pino AV, Bozza FA, Salluh JI, Rodrigues RS, Soares JHN, Giannella-Neto A. Effects of descending positive end-expiratory pressure on lung mechanics and aeration in healthy anaesthetized piglets. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2006; 10:R122. [PMID: 16925814 PMCID: PMC1750982 DOI: 10.1186/cc5030] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2006] [Accepted: 08/22/2006] [Indexed: 12/03/2022]
Abstract
Introduction Atelectasis and distal airway closure are common clinical entities of general anaesthesia. These two phenomena are expected to reduce the ventilation of dependent lung regions and represent major causes of arterial oxygenation impairment in anaesthetic conditions. The behaviour of the elastance of the respiratory system (Ers), as well as the lung aeration assessed by computed tomography (CT) scan, was evaluated during a descendent positive end-expiratory pressure (PEEP) titration. This work sought to evaluate the potential usefulness of Ers monitoring to set the PEEP in order to prevent tidal recruitment and hyperinflation of healthy lungs under general anaesthesia. Methods PEEP titration (from 16 to 0 cmH2O, tidal volume of 8 ml/kg) was performed, and at each PEEP, CT scans were obtained during end-expiratory and end-inspiratory pauses in six healthy, anaesthetized and paralyzed piglets. The distribution of lung aeration was determined and the tidal re-aeration was calculated as the difference between end-expiratory and end-inspiratory poorly aerated and normally aerated areas. Similarly, tidal hyperinflation was obtained as the difference between end-inspiratory and end-expiratory hyperinflated areas. Ers was estimated from the equation of motion of the respiratory system during all PEEP titration with the least-squares method. Results Hyperinflated areas decreased from PEEP 16 to 0 cmH2O (ranges decreased from 24–62% to 1–7% at end-expiratory pauses and from 44–73% to 4–17% at end-inspiratory pauses) whereas normally aerated areas increased (from 30–66% to 72–83% at end-expiratory pauses and from 19–48% to 73–77% at end-inspiratory pauses). From 16 to 8 cmH2O, Ers decreased with a corresponding reduction in tidal hyperinflation. A flat minimum of Ers was observed from 8 to 4 cmH2O. For PEEP below 4 cmH2O, Ers increased in association with a rise in tidal re-aeration and a flat maximum of the normally aerated areas. Conclusion In healthy piglets under a descending PEEP protocol, the PEEP at minimum Ers presented a compromise between maximizing normally aerated areas and minimizing tidal re-aeration and hyperinflation. High levels of PEEP, greater than 8 cmH2O, reduced tidal re-aeration but increased hyperinflation with a concomitant decrease in normally aerated areas.
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Affiliation(s)
- Alysson Roncally S Carvalho
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, P.O. Box 68510, 21945-970, Rio de Janeiro, RJ, Brazil
| | - Frederico C Jandre
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, P.O. Box 68510, 21945-970, Rio de Janeiro, RJ, Brazil
| | - Alexandre V Pino
- Electronic Engineering Department, Catholic University of Pelotas, Rua Félix da Cunha 412, 96010-000, Pelotas, RS, Brazil
| | - Fernando A Bozza
- Clementino Fraga Filho Hospital, ICU, Federal University of Rio de Janeiro, Av. Brigadeiro Trompowsky, s/n°, 21950-900, Rio de Janeiro, RJ, Brazil
| | - Jorge I Salluh
- National Institute of Cancer – 1, ICU, Praça Cruz Vermelha 23, 20230-130, Rio de Janeiro, RJ, Brazil
| | - Rosana S Rodrigues
- Clementino Fraga Filho Hospital, Radiodiagnostic Service, Federal University of Rio de Janeiro, Av. Brigadeiro Trompowsky, s/n°, 21950-900, Rio de Janeiro, RJ, Brazil
| | - João HN Soares
- UNIGRANRIO, School of Veterinary Medicine, Rua Professor José de Sousa Herdy 1160, 25071-200, Duque de Caxias, RJ, Brazil
| | - Antonio Giannella-Neto
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, P.O. Box 68510, 21945-970, Rio de Janeiro, RJ, Brazil
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Terragni PP, Rosboch G, Tealdi A, Corno E, Menaldo E, Davini O, Gandini G, Herrmann P, Mascia L, Quintel M, Slutsky AS, Gattinoni L, Ranieri VM. Tidal hyperinflation during low tidal volume ventilation in acute respiratory distress syndrome. Am J Respir Crit Care Med 2006; 175:160-6. [PMID: 17038660 DOI: 10.1164/rccm.200607-915oc] [Citation(s) in RCA: 504] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
RATIONALE Tidal volume and plateau pressure limitation decreases mortality in acute respiratory distress syndrome. Computed tomography demonstrated a small, normally aerated compartment on the top of poorly aerated and nonaerated compartments that may be hyperinflated by tidal inflation. OBJECTIVES We hypothesized that despite tidal volume and plateau pressure limitation, patients with a larger nonaerated compartment are exposed to tidal hyperinflation of the normally aerated compartment. MEASUREMENTS AND MAIN RESULTS Pulmonary computed tomography at end-expiration and end-inspiration was obtained in 30 patients ventilated with a low tidal volume (6 ml/kg predicted body weight). Cluster analysis identified 20 patients in whom tidal inflation occurred largely in the normally aerated compartment (69.9 +/- 6.9%; "more protected"), and 10 patients in whom tidal inflation occurred largely within the hyperinflated compartments (63.0 +/- 12.7%; "less protected"). The nonaerated compartment was smaller and the normally aerated compartment was larger in the more protected patients than in the less protected patients (p = 0.01). Pulmonary cytokines were lower in the more protected patients than in the less protected patients (p < 0.05). Ventilator-free days were 7 +/- 8 and 1 +/- 2 d in the more protected and less protected patients, respectively (p = 0.01). Plateau pressure ranged between 25 and 26 cm H(2)O in the more protected patients and between 28 and 30 cm H(2)O in the less protected patients (p = 0.006). CONCLUSIONS Limiting tidal volume to 6 ml/kg predicted body weight and plateau pressure to 30 cm H(2)O may not be sufficient in patients characterized by a larger nonaerated compartment.
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Affiliation(s)
- Pier Paolo Terragni
- Università di Torino, Dipartimento di Anestesiologia e Rianimazione, Ospedale S. Giovanni Battista-Molinette, Corso Dogliotti 14, 10126 Turin, Italy
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Lu Q, Constantin JM, Nieszkowska A, Elman M, Vieira S, Rouby JJ. Measurement of alveolar derecruitment in patients with acute lung injury: computerized tomography versus pressure-volume curve. Crit Care 2006; 10:R95. [PMID: 16792793 PMCID: PMC1550939 DOI: 10.1186/cc4956] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 05/16/2006] [Accepted: 05/23/2006] [Indexed: 11/10/2022] Open
Abstract
INTRODUCTION Positive end-expiratory pressure (PEEP)-induced lung derecruitment can be assessed by a pressure-volume (P-V) curve method or by lung computed tomography (CT). However, only the first method can be used at the bedside. The aim of the study was to compare both methods for assessing alveolar derecruitment after the removal of PEEP in patients with acute lung injury or acute respiratory distress syndrome. METHODS P-V curves (constant-flow method) and spiral CT scans of the whole lung were performed at PEEPs of 15 and 0 cmH2O in 19 patients with acute lung injury or acute respiratory distress syndrome. Alveolar derecruitment was defined as the difference in lung volume measured at an airway pressure of 15 cmH2O on P-V curves performed at PEEPs of 15 and 0 cmH2O, and as the difference in the CT volume of gas present in poorly aerated and nonaerated lung regions at PEEPs of 15 and 0 cmH2O. RESULTS Alveolar derecruitments measured by the CT and P-V curve methods were 373 +/- 250 and 345 +/- 208 ml (p = 0.14), respectively. Measurements by both methods were tightly correlated (R = 0.82, p < 0.0001). The derecruited volume measured by the P-V curve method had a bias of -14 ml and limits of agreement of between -158 and +130 ml in comparison with the average derecruited volume of the CT and P-V curve methods. CONCLUSION Alveolar derecruitment measured by the CT and P-V curve methods are tightly correlated. However, the large limits of agreement indicate that the P-V curve and the CT method are not interchangeable.
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Affiliation(s)
- Qin Lu
- Surgical Intensive Care Unit Pierre Viars, Department of Anesthesiology, Assistance Publique-Hôpitaux de Paris, La Pitié-Salpêtrière Hospital, 47-83 boulevard de l'Hôpital 75013 Paris, France
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Galiatsou E, Kostanti E, Svarna E, Kitsakos A, Koulouras V, Efremidis SC, Nakos G. Prone position augments recruitment and prevents alveolar overinflation in acute lung injury. Am J Respir Crit Care Med 2006; 174:187-97. [PMID: 16645177 DOI: 10.1164/rccm.200506-899oc] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
RATIONALE Mechanical ventilation in the prone position may be an effective means of recruiting nonaerated alveolar units and minimizing ventilation-induced lung injury. OBJECTIVES To evaluate and quantify regional lung volume alterations when patients with lobar or diffuse acute lung injury (ALI) were turned prone after a recruitment maneuver. METHODS In 21 patients with ALI, a recruitment maneuver was applied in the supine position followed by a multislice spiral computed tomography (CT) scan; then, patients were turned prone and a second CT scan was performed. MAIN RESULTS Both the recruitment maneuver and prone position resulted in improved oxygenation in patients with lobar ALI. Prone position also resulted in increased respiratory system compliance and decreased Pa(CO(2)) in lobar ALI. In lobar ALI, the proportion of overinflated and nonaerated areas declined, whereas the proportion of well-aerated areas increased in the prone position. The decrease in overinflated areas was observed mainly in the ventral areas. The dorsal regions showed a decrease in nonaerated areas and an increase in well-aerated areas. Recruitment maneuver and prone position improved oxygenation but had no effect either on Pa(CO(2)) or on the respiratory system compliance of patients with diffuse ALI. These patients responded to prone position with a decrease in nonaerated areas. CONCLUSIONS Prone position recruited the edematous lung further than recruitment maneuvers and reversed overinflation, resulting in a more homogeneous distribution of aeration. The effects of the prone position were more pronounced in patients with lobar ALI.
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Affiliation(s)
- Eftichia Galiatsou
- Intensive Care Unit, University Hospital of Ioannina, University Street, 45500 Ioannina, Greece
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Simon BA, Christensen GE, Low DA, Reinhardt JM. Computed tomography studies of lung mechanics. Ann Am Thorac Soc 2006; 2:517-21, 506-7. [PMID: 16352757 PMCID: PMC2713339 DOI: 10.1513/pats.200507-076ds] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The study of lung mechanics has progressed from global descriptions of lung pressure and volume relationships to the high-resolution, three-dimensional, quantitative measurement of dynamic regional mechanical properties and displacements. X-ray computed tomography (CT) imaging is ideally suited to the study of regional lung mechanics in intact subjects because of its high spatial and temporal resolution, correlation of functional data with anatomic detail, increasing volumetric data acquisition, and the unique relationship between CT density and lung air content. This review presents an overview of CT measurement principles and limitations for the study of regional mechanics, reviews some of the early work that set the stage for modern imaging approaches and impacted the understanding and management of patients with acute lung injury, and presents evolving novel approaches for the analysis and application of dynamic volumetric lung image data.
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Affiliation(s)
- Brett A Simon
- Department of Anesthesiology, Tower 711, Johns Hopkins Hospital, 600 North Wolfe Street, Baltimore, MD 21287-8711, USA.
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Albaiceta GM, Luyando LH, Parra D, Menendez R, Calvo J, Pedreira PR, Taboada F. Inspiratory vs. expiratory pressure-volume curves to set end-expiratory pressure in acute lung injury. Intensive Care Med 2005; 31:1370-8. [PMID: 16091965 DOI: 10.1007/s00134-005-2746-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2005] [Accepted: 07/03/2005] [Indexed: 10/25/2022]
Abstract
OBJECTIVE To study the effects of two levels of positive end-expiratory pressure (PEEP), 2 cm H(2)O above the lower inflection point of the inspiratory limb and equal to the point of maximum curvature on the expiratory limb of the pressure-volume curve, in gas exchange, respiratory mechanics, and lung aeration. DESIGN AND SETTING Prospective clinical study in the intensive care unit and computed tomography ward of a university hospital. PATIENTS Eight patients with early acute lung injury. INTERVENTIONS Both limbs of the static pressure-volume curve were traced and inflection points calculated using a sigmoid model. During ventilation with a tidal volume of 6 ml/kg we sequentially applied a PEEP 2 cm H(2)O above the inspiratory lower inflection point (15.5+/-3.1 cm H(2)O) and a PEEP equal to the expiratory point of maximum curvature (23.5+/-4.1 cmH(2)O). MEASUREMENTS AND RESULTS Arterial blood gases, respiratory system compliance and resistance and changes in lung aeration (measured on three computed tomography slices during end-expiratory and end-inspiratory pauses) were measured at each PEEP level. PEEP according to the expiratory point of maximum curvature was related to an improvement in oxygenation, increase in normally aerated, decrease in nonaerated lung volumes, and greater alveolar stability. There was also an increase in PaCO(2), airway pressures, and hyperaerated lung volume. CONCLUSIONS High PEEP levels according to the point of maximum curvature of the deflation limb of the pressure-volume curve have both benefits and drawbacks.
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Affiliation(s)
- Guillermo M Albaiceta
- Department of Intensive Medicine, Hospital Universitario Central de Asturias, Celestino Villamil s/n, 33006 Oviedo, Spain.
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