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Mowery NT. Ventilator Strategies for Chronic Obstructive Pulmonary Disease and Acute Respiratory Distress Syndrome. Surg Clin North Am 2017; 97:1381-1397. [DOI: 10.1016/j.suc.2017.07.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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Ahmed SM, Athar M. Mechanical ventilation in patients with chronic obstructive pulmonary disease and bronchial asthma. Indian J Anaesth 2015; 59:589-98. [PMID: 26556918 PMCID: PMC4613406 DOI: 10.4103/0019-5049.165856] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Chronic obstructive pulmonary disease (COPD) and bronchial asthma often complicate the surgical patients, leading to post-operative morbidity and mortality. Many authors have tried to predict post-operative pulmonary complications but not specifically in COPD. The aim of this review is to provide recent evidence-based guidelines regarding predictors and ventilatory strategies for mechanical ventilation in COPD and bronchial asthma patients. Using Google search for indexing databases, a search for articles published was performed using various combinations of the following search terms: ‘Predictors’; ‘mechanical ventilation’; COPD’; ‘COPD’; ‘bronchial asthma’; ‘recent strategies’. Additional sources were also identified by exploring the primary reference list.
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Affiliation(s)
- Syed Moied Ahmed
- Department of Anaesthesiology and Critical Care, Jawaharlal Nehru Medical College and Hospital, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
| | - Manazir Athar
- Department of Anaesthesiology and Critical Care, Jawaharlal Nehru Medical College and Hospital, Aligarh Muslim University, Aligarh, Uttar Pradesh, India
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Beurskens CJP, Wösten-van Asperen RM, Preckel B, Juffermans NP. The potential of heliox as a therapy for acute respiratory distress syndrome in adults and children: a descriptive review. Respiration 2015; 89:166-74. [PMID: 25662070 DOI: 10.1159/000369472] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Accepted: 10/28/2014] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND In neonatal respiratory distress syndrome (RDS) and acute RDS (ARDS) mechanical ventilation is often necessary to manage hypoxia, whilst protecting the lungs through lower volume ventilation and permissive hypercapnia. Mechanical ventilation can, however, induce or aggravate the lung injury caused by the respiratory distress. Helium, in a gas mixture with oxygen (heliox), has a low density and can reduce the flow in narrow airways and allow for lower driving pressures. OBJECTIVES The aim of this study was to review preclinical and clinical studies of the use of heliox ventilation in acute lung injury associated with respiratory failure. METHODS A systematic search was executed in the PubMed and EMBASE databases, with search terms referring to ARDS or an acute lung injury condition associated with respiratory failure and the corresponding intervention. RESULTS A total of 576 papers were retrieved. After the majority had been excluded 20 papers remained, of which 6 articles described animal models (3 paediatric; 3 adult animal models) and 14 were clinical studies, of which 12 described paediatric patient populations and 2 adult patient populations. In both paediatric and adult animal models, heliox improved gas exchange while allowing for less invasive ventilation in a wide variety of models using different ventilation modes. Clinical studies show a reduction in the work of breathing during heliox ventilation, with a concomitant increase in pH and decrease in PaCO2 levels compared to oxygen ventilation. CONCLUSIONS Although evidence so far is limited, there may be a rationale for heliox ventilation in ARDS as an intervention to improve ventilation and reduce the work of breathing.
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Affiliation(s)
- Charlotte J P Beurskens
- Laboratory of Experimental Intensive Care and Anaesthesiology, University of Amsterdam, Amsterdam, The Netherlands
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Wang W, Das A, Ali T, Cole O, Chikhani M, Haque M, Hardman JG, Bates DG. Can computer simulators accurately represent the pathophysiology of individual COPD patients? Intensive Care Med Exp 2014; 2:23. [PMID: 26266920 PMCID: PMC4513041 DOI: 10.1186/s40635-014-0023-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 07/21/2014] [Indexed: 11/21/2022] Open
Abstract
BACKGROUND Computer simulation models could play a key role in developing novel therapeutic strategies for patients with chronic obstructive pulmonary disease (COPD) if they can be shown to accurately represent the pathophysiological characteristics of individual patients. METHODS We evaluated the capability of a computational simulator to reproduce the heterogeneous effects of COPD on alveolar mechanics as captured in a number of different patient datasets. RESULTS Our results show that accurately representing the pathophysiology of individual COPD patients necessitates the use of simulation models with large numbers (up to 200) of compartments for gas exchange. The tuning of such complex simulation models 'by hand' to match patient data is not feasible, and thus we present an automated approach based on the use of global optimization algorithms and high-performance computing. Using this approach, we are able to achieve extremely close matches between the simulator and a range of patient data including PaO2, PaCO2, pulmonary deadspace fraction, pulmonary shunt fraction, and ventilation/perfusion (/Q) curves. Using the simulator, we computed combinations of ventilator settings that optimally manage the trade-off between ensuring adequate gas exchange and minimizing the risk of ventilator-associated lung injury for an individual COPD patient. CONCLUSIONS Our results significantly strengthen the credibility of computer simulation models as research tools for the development of novel management protocols in COPD and other pulmonary disease states.
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Affiliation(s)
- Wenfei Wang
- />School of Engineering, University of Warwick, Coventry, CV4 7AL UK
| | - Anup Das
- />School of Engineering, University of Warwick, Coventry, CV4 7AL UK
| | - Tayyba Ali
- />Anaesthesia & Critical Care Research Group, School of Medicine, University of Nottingham, Nottingham, NG7 2UH UK
| | - Oanna Cole
- />Anaesthesia & Critical Care Research Group, School of Medicine, University of Nottingham, Nottingham, NG7 2UH UK
| | - Marc Chikhani
- />Anaesthesia & Critical Care Research Group, School of Medicine, University of Nottingham, Nottingham, NG7 2UH UK
| | - Mainul Haque
- />Anaesthesia & Critical Care Research Group, School of Medicine, University of Nottingham, Nottingham, NG7 2UH UK
| | - Jonathan G Hardman
- />Anaesthesia & Critical Care Research Group, School of Medicine, University of Nottingham, Nottingham, NG7 2UH UK
| | - Declan G Bates
- />School of Engineering, University of Warwick, Coventry, CV4 7AL UK
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Prospective randomized crossover study of a new closed-loop control system versus pressure support during weaning from mechanical ventilation. Anesthesiology 2013; 119:631-41. [PMID: 23619172 DOI: 10.1097/aln.0b013e3182952608] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
BACKGROUND Intellivent is a new full closed-loop controlled ventilation that automatically adjusts both ventilation and oxygenation parameters. The authors compared gas exchange and breathing pattern variability of Intellivent and pressure support ventilation (PSV). METHODS In a prospective, randomized, single-blind design crossover study, 14 patients were ventilated during the weaning phase, with Intellivent or PSV, for two periods of 24 h in a randomized order. Arterial blood gases were obtained after 1, 8, 16, and 24 h with each mode. Ventilatory parameters were recorded continuously in a breath-by-breath basis during the two study periods. The primary endpoint was oxygenation, estimated by the calculation of the difference between the PaO2/FIO2 ratio obtained after 24 h of ventilation and the PaO2/FIO2 ratio obtained at baseline in each mode. The variability in the ventilatory parameters was also evaluated by the coefficient of variation (SD to mean ratio). RESULTS There were no adverse events or safety issues requiring premature interruption of both modes. The PaO2/FIO2 (mean ± SD) ratio improved significantly from 245 ± 75 at baseline to 294 ± 123 (P = 0.03) after 24 h of Intellivent. The coefficient of variation of inspiratory pressure and positive end-expiratory pressure (median [interquartile range]) were significantly higher with Intellivent, 16 [11-21] and 15 [7-23]%, compared with 6 [5-7] and 7 [5-10]% in PSV. Inspiratory pressure, positive end-expiratory pressure, and FIO2 changes were adjusted significantly more often with Intellivent compared with PSV. CONCLUSIONS Compared with PSV, Intellivent during a 24-h period improved the PaO2/FIO2 ratio in parallel with more variability in the ventilatory support and more changes in ventilation settings.
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Spontaneous Breathing of Heliox Using a Semi-Closed Circuit: A Bench Study. Int J Artif Organs 2012; 35:466-70. [PMID: 22466996 DOI: 10.5301/ijao.5000088] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/23/2012] [Indexed: 11/20/2022]
Abstract
Introduction: The use of helium-oxygen mixture (heliox) for ventilation has an advantage in patients with obstruction of the airways. The physical properties of helium enable an easier gas flow through the airways; this enables easier breathing for the patient when compared to standard ventilation of air. A high cost of heliox falls within the factors that limit the use of heliox in clinical practice. At present, heliox is administered by use of an open circuit. The aim of this study is to propose a way of heliox administration that reduces heliox consumption but does not affect the positive heliox effects upon the airway resistance. Methods: To minimize consumption of heliox, a semi-closed circuit has been designed. The circuit is a modification of an anesthetic circuit composed of parts with the lowest possible resistances. As any circuit has its own resistance, the evaluation of its possible negative effect upon the work of breathing of patients with exacerbation of chronic obstructive pulmonary disease (COPD) has been conducted. Results: A semi-closed circuit for heliox administration has been constructed and evaluated. The intrinsic resistance of both the inspiratory and expiratory limbs of the circuit is less than 140 Pa·s/l. This resistance does not represent a significant workload for a patient with COPD exacerbation whose airway resistance is 10 to 20 fold higher. Conclusions: The designed semi-closed circuit offers a potential benefit of heliox in patients with COPD exacerbation.
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A multicenter, randomized trial of noninvasive ventilation with helium-oxygen mixture in exacerbations of chronic obstructive lung disease. Crit Care Med 2010; 38:145-51. [PMID: 19730250 DOI: 10.1097/ccm.0b013e3181b78abe] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To assess the effect of a helium-oxygen mixture on intubation rate and clinical outcomes during noninvasive ventilation in acute exacerbation of chronic obstructive pulmonary disease. DESIGN Multicenter, prospective, randomized, controlled trial. SETTING Seven intensive care units. PATIENTS A total of 204 patients with known or suspected chronic obstructive pulmonary disease and acute dyspnea, Paco2> 45 mm Hg and two among the following factors: pH <7.35, Paco2 <50 mm Hg, respiratory rate >25/min. INTERVENTIONS Noninvasive ventilation randomly applied with or without helium (inspired oxygen fraction 0.35) via a face mask. MEASUREMENTS AND MAIN RESULTS Duration and complications of NIV and mechanical ventilation, endotracheal intubation, discharge from intensive care unit and hospital, mortality at day 28, adverse and serious adverse events were recorded. Follow-up lasted until 28 days since enrollment. Intubation rate did not significantly differ between groups (24.5% vs. 30.4% with or without helium, p = .35). No difference was observed in terms of improvement of arterial blood gases, dyspnea, and respiratory rate between groups. Duration of noninvasive ventilation, length of stay, 28-day mortality, complications and adverse events were similar, although serious adverse events tended to be lower with helium (10.8% vs. 19.6%, p = .08). CONCLUSIONS Despite small trends favoring helium, this study did not show a statistical superiority of using helium during NIV to decrease the intubation rate in acute exacerbation of chronic obstructive pulmonary disease.
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Molloy EJ, McCallion N, O'Donnell CPF, Davis PG. Heliox for prevention of morbidity and mortality in ventilated newborn infants. Hippokratia 2008. [DOI: 10.1002/14651858.cd007304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Eleanor J Molloy
- National Maternity Hospital; Neonatal Unit; Holles Street Dublin 2 Ireland
| | - Naomi McCallion
- National Maternity Hospital; Neonatal Unit; Holles Street Dublin 2 Ireland
| | - Colm PF O'Donnell
- National Maternity Hospital; Neonatal Unit; Holles Street Dublin 2 Ireland
| | - Peter G Davis
- Royal Women's Hospital; Department of Obstetrics and Gynaecology; 132 Grattan Street Carlton Victoria Australia 3053
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Rogers CS, Abraham WM, Brogden KA, Engelhardt JF, Fisher JT, McCray PB, McLennan G, Meyerholz DK, Namati E, Ostedgaard LS, Prather RS, Sabater JR, Stoltz DA, Zabner J, Welsh MJ. The porcine lung as a potential model for cystic fibrosis. Am J Physiol Lung Cell Mol Physiol 2008; 295:L240-63. [PMID: 18487356 DOI: 10.1152/ajplung.90203.2008] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Airway disease currently causes most of the morbidity and mortality in patients with cystic fibrosis (CF). However, understanding the pathogenesis of CF lung disease and developing novel therapeutic strategies have been hampered by the limitations of current models. Although the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) has been targeted in mice, CF mice fail to develop lung or pancreatic disease like that in humans. In many respects, the anatomy, biochemistry, physiology, size, and genetics of pigs resemble those of humans. Thus pigs with a targeted CFTR gene might provide a good model for CF. Here, we review aspects of porcine airways and lung that are relevant to CF.
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Affiliation(s)
- Christopher S Rogers
- Department of Internal Medicine, Roy J. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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Clinical concise review: Mechanical ventilation of patients with chronic obstructive pulmonary disease. Crit Care Med 2008; 36:1614-9. [DOI: 10.1097/ccm.0b013e318170f0f3] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Eves ND, Ford GT. Helium–oxygen: A versatile therapy to “lighten the load” of chronic obstructive pulmonary disease (COPD). ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.rmedu.2007.04.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Brighenti C, Barbini P, Gnudi G, Cevenini G, Pecchiari M, D'Angelo E. Helium–oxygen ventilation in the presence of expiratory flow-limitation: A model study. Respir Physiol Neurobiol 2007; 157:326-34. [PMID: 17293172 DOI: 10.1016/j.resp.2006.12.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 12/18/2006] [Accepted: 12/20/2006] [Indexed: 10/23/2022]
Abstract
A comparison between air and heliox (80% helium-20% oxygen) ventilation was performed using a mathematical, non-linear dynamic, morphometric model of the respiratory system. Different obstructive conditions, all causing expiratory flow limitation (EFL), were simulated during mechanical ventilation to evaluate and interpret the effects of heliox on tidal EFL and dynamic hyperinflation. Relative to air ventilation, intrinsic positive end-expiratory pressure did not change with heliox if the obstruction was limited to the peripheral airways, i.e. beyond the seventh generation. When central airways were also involved, heliox reduced dynamic hyperinflation (DH) if the flow-limiting segment remained in the fourth to seventh airway generation during the whole expiration, but produced only minor effects if, depending on the contribution of peripheral to total apparent airway resistance, the flow-limiting segment moved eventually to the peripheral airways. In no case did heliox abolish EFL occurring with air ventilation, indicating that any increase in driving pressure would be without effect on DH. Hence, to the extent that chronic obstructive pulmonary disease (COPD) affects primarily the peripheral airways, and causes EFL through the same mechanisms operating in the model, heliox administration should not be expected to appreciably reduce DH in the majority of COPD patients who are flow-limited at rest.
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Affiliation(s)
- Chiara Brighenti
- Dipartimento di Elettronica, Informatica e Sistemistica, Università di Bologna, 47023 Cesena, Italy
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Acosta P, Santisbon E, Varon J. “The Use of Positive End-Expiratory Pressure in Mechanical Ventilation”. Crit Care Clin 2007; 23:251-61, x. [PMID: 17368169 DOI: 10.1016/j.ccc.2006.12.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
An improvement in oxygenation for patients who have acute respiratory failure using PEEP was described close to 40 years ago. Since then, a considerable amount of research has allowed clinicians to use this therapeutic modality in various ways. In patients receiving mechanical ventilation, the term positive end-expiratory pressure (PEEP) refers to pressure in the airway at the end of passive expiration that exceeds atmospheric pressure. The use of PEEP mainly has been reserved to recruit or stabilize lung units and improve oxygenation in patients who have hypoxemic respiratory failure. It has been shown that this helps the respiratory muscles to decrease the work of breathing and the amount of infiltrated-atelectatic tissues. The beneficial effects of the use of PEEP include: the improvement of oxygenation, recruitment of lung units, and improvement of compliance. Other effects can be adverse, like decreasing cardiac output, increased risk of barotrauma, and the interference with assessment of hemodynamic pressures.
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Affiliation(s)
- Pilar Acosta
- Dorrington Medical Associates, 2219 Dorrington Street, Houston, TX 77030, USA
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Brighenti C, Gnudi G, Barbini P, Avanzolini G. Estimation of expiratory resistance: a simulation study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2007; 2007:4247-4250. [PMID: 18002940 DOI: 10.1109/iembs.2007.4353274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
It is of particular importance to detect and quantify obstructive pathological conditions in mechanically ventilated patients, especially in the presence of expiratory flow limitation (EFL), in order to help the clinicians in the choice of the most appropriate ventilation and pharmacological strategies. Aim of this work is to test by simulation a non invasive procedure for estimating the total apparent expiratory resistance of the respiratory system (Rtae). The proposed procedure is based on a time-varying two-element viscoelastic model characterized by the variable resistance Rtae and by a constant compliance estimated by the end-inspiratory occlusion technique. A non linear, dynamic, morphometric model of respiratory mechanics, based on Weibel's representation of the tracheobronchial tree, was used to simulate normal and obstructive respiratory conditions, leading to EFL, during artificial ventilation. The proposed resistance was computed in all simulated cases when the 50% and the 75% of tidal volume has been exhaled during a normal expiration. Rtae appeared to be dependent on the degree of airway obstruction and could provide useful information on how the airway compression varies during expiration.
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Affiliation(s)
- Chiara Brighenti
- Department of Electronics, Computer Science and Systems, University of Bologna, 40136 Bologna, Italy.
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Tzoufi M, Mentzelopoulos SD, Roussos C, Armaganidis A. The effects of nebulized salbutamol, external positive end-expiratory pressure, and their combination on respiratory mechanics, hemodynamics, and gas exchange in mechanically ventilated chronic obstructive pulmonary disease patients. Anesth Analg 2005; 101:843-850. [PMID: 16116002 DOI: 10.1213/01.ane.0000167276.92462.ba] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We hypothesized that combined salbutamol and external positive end-expiratory pressure (PEEPe) may present additive benefits in chronic obstructive pulmonary disease (COPD) exacerbation. In 10 anesthetized, mechanically ventilated, and bronchodilator-responsive COPD patients exhibiting moderate intrinsic PEEP (PEEPi), we assessed respiratory system (rs) mechanics, hemodynamics, and gas exchange at (a) baseline (zero PEEPe [ZEEPe]), (b) 30 min after 5 mg of nebulized salbutamol administration (ZEEPe-S), (c) 30 min after setting PEEPe at baseline PEEPi level (PEEPe), and (d) 30 min after 5 mg of nebulized salbutamol administration with PEEPe maintained unchanged (PEEPe-S). Return of determined variable values to baseline values was confirmed before PEEPe application. Relative to ZEEPe, (a) at ZEEP-S, PEEPi (4.8 +/- 0.7 versus 7.0 +/- 1.1 cm H(2)O), functional residual capacity change (115.6 +/- 23.1 versus 202.1 +/- 46.0 mL), minimal rs (airway) resistance (9.3 +/- 1.4 versus 11.8 +/- 2.2 cm H(2)O.L(-1).s(-1)), and additional rs resistance (5.2 +/- 1.4 versus 7.2 +/- 1.3 cm H(2)O.L(-1).s(-1)) were reduced (P < 0.01), and hemodynamics were improved; (b) at PEEPe, PEEPi (3.7 +/- 1.3 cm H(2)O) was reduced (P < 0.01), and gas exchange was improved; and (c) at PEEPe-S, PEEPi (2.0 +/- 1.2 cm H(2)O) was minimized, and rs mechanics (static rs elastance included), hemodynamics, and gas exchange were improved. Conclusively, in carefully preselected COPD patients, bronchodilation/PEEPe exhibits additive benefits.
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Affiliation(s)
- Maria Tzoufi
- *Department of Intensive Care Medicine, Attikon University Hospital; and †Department of Intensive Care Medicine, Evaggelismos General Hospital, Athens, Greece
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Tassaux D, Gainnier M, Battisti A, Jolliet P. Helium-oxygen decreases inspiratory effort and work of breathing during pressure support in intubated patients with chronic obstructive pulmonary disease. Intensive Care Med 2005; 31:1501-7. [PMID: 16172846 DOI: 10.1007/s00134-005-2796-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2005] [Accepted: 08/09/2005] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To evaluate the impact of helium-oxygen (He/O2) on inspiratory effort and work of breathing (WOB) in intubated COPD patients ventilated with pressure support. DESIGN AND SETTING Prospective crossover interventional study in the medical ICU of a university hospital. PATIENTS AND PARTICIPANTS Ten patients. INTERVENTIONS Sequential inhalation (30 min each) of three gas mixtures: (a) air/O2, (b) He/O2 (c) air/O2, at constant FIO2 and level of pressure support. MEASUREMENTS AND RESULTS Inspiratory effort and WOB were determined by esophageal and gastric pressure. Throughout the study pressure support and FIO2 were 14+/-3 cmH2O and 0.33+/-0.07 respectively. Compared to Air/O2, He/O2 reduced the number of ineffective breaths (4+/-5 vs. 9+/-5 breaths/min), intrinsic PEEP (3.1+/-2 vs. 4.8+/-2 cmH2O), the magnitude of negative esophageal pressure swings (6.7+/-2 vs. 9.1+/-4.9 cmH2O), pressure-time product (42+/-37 vs. 67+/-65 cmH2O s(-1) min(-1)), and total WOB (11+/-3 vs. 18+/-10 J/min). Elastic (6+/-1 vs. 10+/-6 J/min) and resistive (5+/-1 vs. 9+/-4 J/min) components of the WOB were decreased by He/O2. CONCLUSIONS In intubated COPD patients ventilated with pressure support He/O2 reduces intrinsic PEEP, the number of ineffective breaths, and the magnitude of inspiratory effort and WOB. He/O2 could prove useful in patients with high levels of PEEPi and WOB ventilated in pressure support, for example, during weaning.
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Affiliation(s)
- Didier Tassaux
- Medical Intensive Care, University Hospital, 1211, Geneva 14, Switzerland
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Felici M, Filoche M, Straus C, Similowski T, Sapoval B. Diffusional screening in real 3D human acini--a theoretical study. Respir Physiol Neurobiol 2005; 145:279-93. [PMID: 15705542 DOI: 10.1016/j.resp.2004.10.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 09/30/2004] [Accepted: 10/20/2004] [Indexed: 11/22/2022]
Abstract
Gas exchange at the acinar level involves several physico-chemical phenomena within a complex geometry. A gas transport model, which takes into account both the diffusion into the acinus and the diffusion across the alveolar membrane, is used to understand gas mixing in realistic systems. It is first shown that the behaviour of the system, computed on model geometries in 3D, only depends on the topological structure of the acinus. Taking advantage of this property, a new efficient method based on random walks on a lattice is used to compute gas diffusion in structures taken from real morphological data. This approach shows that, at rest, the human acinus efficiency is only 30-40%. These results provide a new evidence of the existence of diffusional screening at the acinar level. This implies permanent spatial inhomogeneity of oxygen and carbon dioxide partial pressure. The notion of an "alveolar gas" is reinterpreted as a spatial average of the gas distribution. This model casts new light on the respiratory properties of other gas mixtures, such as helium-oxygen.
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Affiliation(s)
- M Felici
- CNRS/PMC, Laboratoire de Physique de la Matière Condensée, Ecole Polytechnique, 91128 Palaiseau, France
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Lee DL, Lee H, Chang HW, Chang AYW, Lin SL, Huang YCT. Heliox improves hemodynamics in mechanically ventilated patients with chronic obstructive pulmonary disease with systolic pressure variations. Crit Care Med 2005; 33:968-73. [PMID: 15891322 DOI: 10.1097/01.ccm.0000163403.42842.fe] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To test the hypothesis that, compared with air-oxygen, heliox would improve cardiac performance in mechanically ventilated patients with severe chronic obstructive pulmonary disease and systolic pressure variations >15 mm Hg and to determine clinical variables associated with favorable hemodynamic responses to heliox. DESIGN A prospective interventional study. SETTING Medical and respiratory intensive care units at a university-affiliated tertiary medical center. PATIENTS Twenty-five consecutive mechanically ventilated patients with severe chronic obstructive pulmonary disease and acute respiratory failure who had systolic pressure variations >15 mm Hg. INTERVENTIONS Respiratory and hemodynamic measurements were taken at the following time with the same ventilator setting: a) baseline; b) after 30 mins with heliox; and c) 30 mins after return to air-oxygen. MEASUREMENTS AND MAIN RESULTS Heliox ventilation decreased intrinsic positive end-expiratory pressure (air-oxygen vs. heliox [mean +/- sd] 13 +/- 4 cm H2O vs. 5 +/- 2 cm H2O, p < .05), trapped lung volume (air-oxygen vs. heliox 362 +/- 67 mL vs. 174 +/- 86 mL, p < .05), and respiratory changes in systolic pressure variations (DeltaPP) (air-oxygen vs. heliox 29 +/- 5% vs. 13 +/- 7%, p < .05). In the ten patients with pulmonary arterial catheters, heliox decreased mean pulmonary arterial pressure, right atrial pressure, and pulmonary arterial occlusion pressure and increased cardiac index. Preheliox DeltaPP correlated with the magnitude of reduction in intrinsic positive end-expiratory pressure during heliox ventilation. Age, preheliox Paco2, and ratio of forced expiratory volume at first second to forced vital capacity correlated inversely, whereas preheliox DeltaPP correlated positively with increases in cardiac index. CONCLUSIONS Heliox may be a useful adjunct therapy in patients with severe chronic obstructive pulmonary disease during acute respiratory failure who have persistent intrinsic positive end-expiratory pressure-induced hemodynamic changes despite ventilator management.
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Affiliation(s)
- David Lin Lee
- Department of Medicine, Kaohsiung Veterans General Hospital and School of Medicine, National Yang-Ming Medical University, Taiwan, ROC
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Abstract
Advances in anesthesia involve refinements in understanding, technique, and technology. These refinements have led to better control of the anesthetic state, effective anesthesia for a wider variety of situations, and the ability to bring sicker patients to the operating room. Although the molecular mechanisms underlying the general anesthetic state are unknown, evidence suggests a specific, receptor-based effect. This concept has allowed anesthesiologists to treat anesthetic end points of immobility, lack of awareness, and autonomic control separately. It is likely that anesthesia and naturally occurring sleep interact physiologically. New, processed EEG monitors may allow anesthesiologists to titrate more finely anesthetic dose, with possible benefits in terms of speed of recovery and detection of intraoperative awareness. Since the 1990s, new anesthetic drugs (propofol, desflurane/sevoflurane, cisatracurium) have enhanced greatly control of the anesthetic state. The new intravenous anesthetic agent dexmedetomidine offers sedation with preserved respiration and cognitive function. Although its role has yet to be defined fully, it currently plays a role in ICU sedation and monitored anesthesia care. New anesthesia ventilators have better monitoring and better flow delivery at high airway pressures. These improvements significantly narrow the performance gap between anesthesia and ICU ventilators. In patients with COPD, pulmonary hypertension, or severe hypoxemia, heliox may improve gas flow, and NO may reduce pulmonary vascular resistance and improve oxygenation.
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Affiliation(s)
- Avery Tung
- Department of Anesthesia, Burn Unit, University of Chicago, 5841 S. Maryland Avenue, MC4028, Chicago, IL 60637, USA.
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21
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Abraham E, Andrews P, Antonelli M, Brochard L, Brun-Buisson C, Dobb G, Fagon JY, Groeneveld J, Mancebo J, Metnitz P, Nava S, Pinsky M, Radermacher P, Ranieri M, Richard C, Tasker R, Vallet B. Year in review in Intensive Care Medicine-2003. Part 1: Respiratory failure, infection and sepsis. Intensive Care Med 2004; 30:1017-31. [PMID: 15170528 DOI: 10.1007/s00134-004-2321-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/28/2004] [Indexed: 11/25/2022]
Affiliation(s)
- Edward Abraham
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, University of Colorado Health Sciences Center, Denver, CO, USA
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