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Zhang B, Ratano D, Brochard LJ, Georgopoulos D, Duffin J, Long M, Schepens T, Telias I, Slutsky AS, Goligher EC, Chan TCY. A physiology-based mathematical model for the selection of appropriate ventilator controls for lung and diaphragm protection. J Clin Monit Comput 2020; 35:363-378. [PMID: 32008149 PMCID: PMC7224026 DOI: 10.1007/s10877-020-00479-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Accepted: 01/29/2020] [Indexed: 12/27/2022]
Abstract
Mechanical ventilation is used to sustain respiratory function in patients with acute respiratory failure. To aid clinicians in consistently selecting lung- and diaphragm-protective ventilation settings, a physiology-based decision support system is needed. To form the foundation of such a system, a comprehensive physiological model which captures the dynamics of ventilation has been developed. The Lung and Diaphragm Protective Ventilation (LDPV) model centers around respiratory drive and incorporates respiratory system mechanics, ventilator mechanics, and blood acid–base balance. The model uses patient-specific parameters as inputs and outputs predictions of a patient’s transpulmonary and esophageal driving pressures (outputs most clinically relevant to lung and diaphragm safety), as well as their blood pH, under various ventilator and sedation conditions. Model simulations and global optimization techniques were used to evaluate and characterize the model. The LDPV model is demonstrated to describe a CO2 respiratory response that is comparable to what is found in literature. Sensitivity analysis of the model indicate that the ventilator and sedation settings incorporated in the model have a significant impact on the target output parameters. Finally, the model is seen to be able to provide robust predictions of esophageal pressure, transpulmonary pressure and blood pH for patient parameters with realistic variability. The LDPV model is a robust physiological model which produces outputs which directly target and reflect the risk of ventilator-induced lung and diaphragm injury. Ventilation and sedation parameters are seen to modulate the model outputs in accordance with what is currently known in literature.
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Affiliation(s)
- Binghao Zhang
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Rd, Toronto, ON, M5S 3G8, Canada.
| | - Damian Ratano
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada
| | - Laurent J Brochard
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.,Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
| | - Dimitrios Georgopoulos
- Department of Intensive Care Medicine, University Hospital of Heraklion, University of Crete, Heraklion, Greece
| | - James Duffin
- Department of Physiology, University of Toronto, Toronto, Canada
| | - Michael Long
- Division of Respirology, Department of Medicine, University Health Network, Toronto, Canada
| | - Tom Schepens
- Department of Critical Care Medicine, Antwerp University Hospital, University of Antwerp, Edegem, Belgium
| | - Irene Telias
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.,Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
| | - Arthur S Slutsky
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.,Keenan Centre for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada
| | - Ewan C Goligher
- Interdepartmental Division of Critical Care Medicine, University of Toronto, Toronto, Canada.,Department of Physiology, University of Toronto, Toronto, Canada.,Division of Respirology, Department of Medicine, University Health Network, Toronto, Canada
| | - Timothy C Y Chan
- Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Rd, Toronto, ON, M5S 3G8, Canada
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Late intravascular migration of a previously well functioning labour epidural catheter. Eur J Anaesthesiol 2010; 27:634-6. [PMID: 20299987 DOI: 10.1097/eja.0b013e32833665aa] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Intravascular epidural catheters may result in insufficient labour analgesia or can produce potentially lethal complications following an epidural top-up. We report a case of a previously well functioning epidural catheter positioned epidurally using a combined spinal epidural anaesthesia technique, which subsequently was found to be intravascular. The literature is reviewed.
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Igarashi T, Hirabayashi Y, Shimizu R, Saitoh K, Fukuda H. The epidural structure changes during deep breathing. Can J Anaesth 1999; 46:850-5. [PMID: 10490153 DOI: 10.1007/bf03012974] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE Previous experience has suggested that the insertion of an epidural catheter becomes easier when the patient takes a deep breath. The purpose of this study is to investigate the effects of respiration on the epidural space. METHODS We examined the epidural space using a flexible epiduroscope in 20 patients undergoing thoracic epidural anesthesia. A 17-gauge Tuohy needle was inserted using the paramedian technique and the loss-of-resistance method with 5 ml air. The epiduroscope was introduced into the epidural space via the Tuohy needle. Each patient was requested to take a deep breath when the epiduroscope was positioned at the needle tip and at approximately 10 cm cephalad from the needle tip within the epidural space. The changes in the epidural structure during deep breathing at each site were then measured. RESULTS In 80% of the patients, fatty tissue occupied the needle tip. Through the patients' maximal inspiration, the fatty tissue moved and a visible cavity expanded at the needle tip. Cross section area of the visible cavity at the needle tip was greater at the maximal inspiratory level than at the resting expiratory level: 12.1 +/- 6.7% vs 2.8 +/- 2.1% (mean +/- SD, P < 0.0001). In all patients, the visible cavity within the epidural space, which had already been expanded by injected air, became more expanded after maximal inspiration. Cross section area of the visible cavity at the 10 cm cephalad position was greater at the maximal inspiratory level than at the resting expiratory level: 20.6 +/- 10.0% vs 7.0 +/- 5.3% (P < 0.0001). CONCLUSION Epiduroscopy showed that deep breathing expanded the potential cavity of the epidural space. We suggest that the changes in the epidural structure during deep breathing may assist in the insertion of an epidural catheter.
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Affiliation(s)
- T Igarashi
- Department of Anesthesiology, Jichi Medical School, Kawachi-gun, Tochigi-ken, Japan
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Abstract
Detection of the intravascular placement of epidural catheters is an important but difficult task. In this study, we evaluated maternal and fetal hemodynamic responses to intravenous (i.v.) and epidural injection of isoproterenol (ISO), a proposed chronotropic test dose, in gravid ewes. Near-term, chronically instrumented, gravid ewes with single fetuses were studied at least 48 h after surgery. We continuously recorded maternal heart rate (MHR), systemic and pulmonary blood pressures, uterine blood flow (UBF), and fetal blood pressure and heart rate. Maternal cardiac output was measured by thermodilution. In random sequence, each ewe (n = 11) received i.v. injections of saline, epinephrine (EPI) 15 microg; ISO 4, 16, and 80 microg; or epidural (n = 9 ewes) injections of saline, ISO 4 microg and ISO 40 microg. All variables returned to baseline between experiments. Sections of lumber spinal cord were harvested from five animals for later histopathological study. I.v. ISO caused a dose-related increase in MHR. Cardiac output also increased transiently after all doses of ISO but not after EPI. Maternal diastolic blood pressure decreased after ISO 16 and 80 microg. UBF decreased significantly for 120 s after EPI 15 microg. Epidural ISO did not significantly change maternal systemic or pulmonary blood pressure, cardiac output, or UBF. The 40-microg dose increased MHR significantly. No histopathological changes were seen in three ISO-exposed and two control spinal cords. I.v. ISO reliably induces maternal tachycardia in nonstressed gravid ewes. Unlike EPI, I.v. ISO lacks a statistically significant effect on UBF. However, ISO seems to be rapidly absorbed from the epidural space. Identifying the source of maternal tachycardia after epidural injection of a large dose of ISO could be difficult. If the absence of histopathological change is confirmed, ISO represents an alternative to EPI as a chronotropic test dose.
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Affiliation(s)
- M C Norris
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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Norris MC, Arkoosh VA, Knobler R. Maternal and Fetal Effects of Isoproterenol in the Gravid Ewe. Anesth Analg 1997. [DOI: 10.1213/00000539-199708000-00026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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