DOCSLIB.ORG

Long Chain Versus Medium Chain Lipids in Patients with ARDS: Effects

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Long Chain Versus Medium Chain Lipids in Patients with ARDS: Effects Intensive Care Med (1998) 24: 1029±1033 Ó Springer-Verlag 1998 ORIGINAL V.Smirniotis Long chain versus medium chain G.Kostopanagiotou J.Vassiliou lipids in patients with ARDS: N.Arkadopoulos P.Vassiliou effects on pulmonary haemodynamics A.Datsis E.Kourias and gas exchange Abstract Objective: To compare tion was only associated with an ele- Received: 23 July 1997 Accepted: 15 May 1998 pulmonary haemodynamic and gas vation of oxygen consumption exchange alterations in septic pa- (VO2) from 329 ± 14 to 396 ± 12 ml/ tients with ARDS receiving long- min. During lipid infusion group 1 chain triglycerides (LCT) versus patients presented higher Qva/Qt medium-chain triglycerides (MCT). (37% ± 6% vs 25 % ± 4%), MPAP Design: Prospective, randomised, (33 ± 4vs27±3 mmHg) and VO2 clinical study. (359 ± 11 vs 396 ± 12 ml/min) and Setting: Surgical ICU patients in a lower PaO2/FIO2 (180 ± 35 vs University Hospital. 235 ± 30) values compared to Patients: Twenty-one septic patients group 2. with ARDS were randomly assigned Conclusion: In conclusion, we have to receive 50 % of their non-protein shown that, in septic patients with caloric requirements as either 20 % respiratory failure, LCT administra- LCT (group 1, n = 10) or 20% 1 : 1 tion was associated with more sig- mixture of LCT/MCT (group 2, nificant changes of Qva/Qt, MPAP n = 11). and PaO2/FIO2 compared to infu- Intervention: Intravenous infusion of sion of an LCT/MCT 1 : 1 emulsion. V.Smirniotis ()) × G.Kostopanagiotou × LCT and LCT/MCT combinations at Clinically, these transient alterations J.Vassiliou × N.Arkadopoulos × a rate of 12 g × h1. might cause serious problems in pa- P.Vassiliou × A.Datsis × E.Kourias 2nd Department of Surgery, Measurements and results: The LCT tients with marginal arterial oxyge- University of Athens Medical School, infusion was associated with an in- nation and cardio-respiratory im- ªAreteionº Hospital, crease of pulmonary venous admix- pairment. Athens, Greece ture (Qva/Qt) from 24% ± 5%to 37% ± 6%, an increase of mean Key words Fat emulsion × Medium Mailing address: pulmonary artery pressure (MPAP) chain triglycerides Long chain 22 Hanioti St. GR-15452, Athens, Greece × Tel.: + 30-1-728-6000 from 25 ± 5to33±4 mmHg and de- triglycerides × Pulmonary Fax: +30-1-721-1007 crease of PaO2/FIO2 from 240 ± 30 haemodynamics × Gas exchange × email: [email protected] to 180 ± 35. LCT/MCT administra- ARDS Introduction cleared from the serum and do not contribute to the adi- pose stores [13]. They are independent of carnitine acyl- Many studies have been carried out to examine the me- transferase and are easily transferred into mitochondria tabolic properties of long chain triglyceride (LCT) for beta-oxidation [15]. MCTs may also have a greater emulsion [1±6]. Recently, medium chain triglyceride nitrogen-sparing effect than LCTs [12]. In addition, (MCT) emulsion have emerged as an alternative energy LCTs have been shown to decrease arterial oxygen ten- source which may have significant advantages over stan- sion (PaO2) and increase pulmonary venous admixture dard LCT formulas [3±4, 6±15]. MCTs are rapidly (Qva/Qt) and mean pulmonary artery pressure (MPAP) 1030 Table 1 Clinical characteristics of the patients Group 1 (LCT) Group 2 (LCT/MCT) Sex/ Weight (kg)/ Cause Sex/ Weight (kg)/ Cause Age (year) Height (cm) Age (year) Weight (cm) M/65 70/175 Oesophagectomy M/75 70/180 Oesophagectomy M/45 54/170 Necrotising pancreatitis M/40 68/170 Necrotising pancreatitis F/68 65/170 Small bowel necrosis M/56 72/175 Colon resection M/42 70/175 Colon resection F/60 60/160 Colon resection F/62 60/155 Colon resection F/70 71/165 Rupture of aortic aneurysm M/72 58/165 Necrotising pancreatitis M/40 63/170 Colon resection F/38 68/170 Pancreatic resection M/48 73/165 Pancreatic resection F/65 71/165 Necrotising pancreatitis M/62 70/180 Multiple trauma M/45 52/180 Pancreatic resection F/72 56/180 Splenectomy M/48 68/181 Necrotising pancreatitis M/68 55/160 Necrotising pancreatitis F/42 60/170 Necrotising pancreatitis [1, 5, 7, 13, 16]. These side effects appear to be aggravat- 2. Mean pulmonary artery pressure (MPAP), pulmonary artery oc- ed by the co-existence of sepsis [1, 8, 15]. LCT/MCT clusion pressure (PAOP), and mean systemic arterial pressure emulsions contain less linoleic, linolenic and arachido- (MAP) were measured using a Swan-Ganz catheter (Opticath P7110, Abbott Critical Care Systems, North Chicago, Ill.) and a nic acid compared to pure LCTs [17±18]. These differen- radial artery catheter (20G, Arrow, Reading, Pa.). ces may be important because the aforementioned acids 3. Thermodilution cardiac output was calculated from three elec- are precursors of prostaglandins and other eicosanoids, tronically integrated temperature decay curves, generated after which have been shown to affect pulmonary haemody- indicator injection (monitor: Horizon 2000, Mennen Medical namics, gas exchange and intrapulmonary shunt quo- Ltd, Rehovot, Israel). tient [17, 19±21]. 4. Qva/Qt and oxygen consumption (VO2) were calculated via standard formulas. We hypothesised that, in patients suffering from in- tra-abdominal sepsis complicated by ARDS, LCT/ MCT mixtures may be associated with less prominent Study design changes of pulmonary haemodynamic and gas exchange parameters compared to pure LCT emulsion. Twenty-one consecutive post-operative ICU admissions with sep- sis-related ARDS were randomly assigned to one of two groups: group 1 (n = 10) or group 2 (n = 11) (Table 1). In group 1, 50% of non-protein caloric requirements was infused as a 20% LCT emul- Material and methods sion (Intralipid, Pharmacia). In group 2, the corresponding energy needs were administered as a 20% mixture of LCTs/MCTs (Lipo- All procedures were conducted in full compliance with the stan- fundin MCT/LCT, B.Braun Melsungen AG, Melsungen, Ger- dards of the Institutional Committee for the Protection of Human many). Fat emulsion was intravenously infused over an 8-h period Subjects, in accordance with the Helsinki Declaration of 1975. using a pump (Life Care Pump, model 4, Abbott Laboratories, Our survey included patients with respiratory failure due to in- North Chicago, Ill.) at a rate of 12 g × h1. The remaining 50% of tra-abdominal sepsis (Table 1). All patients met the standard cri- the non-protein energy requirements were covered with glucose, teria for diagnosis of ARDS, presenting lung injury scores of infused continuously i.v. over a 24-h period. more than 2.5 [22]. Sepsis was confirmed by clinical and laboratory Measurements were obtained on the third post-operative day findings as well as positive blood cultures [23]. Patients with pre- at three time points: existing cardiovascular, respiratory, renal or metabolic diseases were excluded from the study. Mechanical ventilation was insti- 1. 30 min before the 8-h lipid infusion was started (before), tuted via an endotracheal tube using a volume-cycled ventilator 2. 30 min before the infusion was completed (during) and (Puritan 7200 Series, Bennett Corporation, Carlsbad, Calif.) and 3. 4 h following suspension of lipid infusion (after). was titrated to maintain arterial PCO2 within the normal range. Pulmonary end-expiratory pressure (PEEP) levels were kept at Each sample was the average of three measurements. No further 8±15 cm H2O (12 ± 2; mean ± SD). All patients received low mole- therapeutic interventions were undertaken during the study peri- cular weight heparin for the prevention of deep vein thrombosis od. and low-dose (2 mg × kg1×min1 i.v.) dopamine. All patients re- ceived total parenteral nutrition and antibiotics. Sedation was maintained with fentanyl (100±200 mg × h1 i.v.) and midazolam Statistical analysis (1±2 mg × h1i.v.). The following measurements were obtained: The comparison of measurements in each cohort was performed 1. Arterial PO2, PCO2, haemoglobin concentration and haemoglo- using a non-parametric Wilcoxon signed rank test for paired data. bin oxygen saturation were measured using a blood gas analyser Mann-Whitney-U test was used to compare group 1 versus (ABL 300, Radiometer Medical A/S, Copenhagen, Denmark). group 2. Statistical significance was accepted if p was less than 0.05. 1031 Table 2 Pulmonary haemodynamic parameters during lipid infu- occlusion pressure, CO cardiac output, Before 30 min before the sion (HR heart rate, MPAP mean pulmonary artery pressure, infusion was started, During 30 min before the infusion was com- MAP mean systemic arterial pressure, PAOP pulmonary artery pleted, After 4 h following suspension of infusion) Group 1 (LCT) Group 2 (LCT/MCT) Before During After Before During After HR (/min) 125 ± 12 110 ± 10 115 ± 8 115 ± 10 126 ± 10 118 ± 8 MPAP (mmHg) 25 ± 533±4a,b 26 ± 626±627±325±5 MAP (mmHg) 90 ± 20 85 ± 15 90 ± 15 90 ± 20 95 ± 15 80 ± 15 PAOP (mmHg) 11 ± 213±210±211±29±310±3 CO (L/min) 8.6 ± 2.5 9 ± 2 9.5 ± 2.5 9.6 ± 2.1 10.5 ± 1.5 8.9 ± 2 Values are presented as mean ± SD a p K 0.05 vs before and after lipid infusion for the same cohort (Wilcoxon signed rank test) b p K 0.05 vs group 2 during lipid infusion (Mann-Whitney U-test) Table 3 Gas exchange parameters during lipid infusion (PaO2 arterial PO2, Qva/Qt pulmonary venous admixture, FIO2 fractional in- spired oxygen, VO2 oxygen consumption) Group 1 (LCT) Group 2 (LCT/MCT) Before During After Before During After pH 7.36 ± 0.7 7.35 ± 0.9 7.36 ± 0.8 7.38 ± 0.2 7.35 ± 0.8 7.35 ± 0.9 a,b Qva/Qt (%) 24 ± 537±625 ± 423±525±424±4 a,b PaO2/FIO2 240 ± 30 180 ± 35 235 ± 35 240 ± 30 235 ± 30 235 ± 25 b a VO2 (ml/min) 333 ± 12 359 ± 11 338 ± 10 329 ± 14 396 ± 12 336 ± 13 Values are presented as mean ± SD a p < 0.05 vs before and after infusion in the same cohort b p < 0.05 vs the other cohort during infusion time Results During lipid infusion, group 1 patients presented higher Qva/Qt and MPAP as well as lower PaO2/FIO2 The data are expressed as means ± SD.
Load more

Recommended publications
  • Gas Exchange
    Gas exchange Gas exchange occurs as a result of respiration, when carbon dioxide is excreted and oxygen taken up, and photosynthesis, when oxygen is excreted and carbon dioxide is taken up. The rate of gas exchange is affected by: • the area available for diffusion • the distance over which diffusion occurs • the concentration gradient across the gas exchange surface • the speed with which molecules diffuse through membranes. Efficient gas exchange systems must: • have a large surface area to volume ratio • be thin • have mechanisms for maintaining steep concentration gradients across themselves • be permeable to gases. Single-celled organisms are aquatic and their cell surface membrane has a sufficiently large surface area to volume ratio to act as an efficient gas exchange surface. In larger organisms, permeable, thin, flat structures have all the properties of efficient gas exchange surfaces but need water to prevent their dehydration and give them mechanical support. Since the solubility of oxygen in water is low, organisms that obtain their oxygen from water can maintain only a low metabolic rate. In small and thin organisms, the distance from gas exchange surface to the inside of the organism is short enough for diffusion of gases to be efficient. Diffusion gradients are maintained because gases are continually used up or produced. In larger organisms, simple diffusion is not an efficient way of transporting gases between cells in the body and the gas exchange surface. In many animals a blood circulatory system carries gases to and from the gas exchange surface. The gas-carrying capacity of the blood is increased by respiratory pigments, such as haemoglobin.
    [Show full text]
  • Mechanisms of Pulmonary Gas Exchange Abnormalities During Experimental Group B Streptococcal Infusion
    003 I -3998/85/1909-0922$02.00/0 PEDIATRIC RESEARCH Vol. 19, No. 9, I985 Copyright 0 1985 International Pediatric Research Foundation, Inc. Printed in (I.S. A. Mechanisms of Pulmonary Gas Exchange Abnormalities during Experimental Group B Streptococcal Infusion GREGORY K. SORENSEN, GREGORY J. REDDING, AND WILLIAM E. TRUOG ABSTRACT. Group B streptococcal sepsis in newborns obtained from GBS (5, 6). Arterial Poz fell by 9 torr in association produces pulmonary arterial hypertension and hypoxemia. with the increase in pulmonary arterial pressure (4). In contrast, The purpose of this study was to investigate the mecha- the neonatal piglet infused with GBS demonstrated both pul- nisms by which hypoxemia occurs. Ten anesthetized, ven- monary arterial hypertension and profound arterial hypoxemia tilated piglets were infused with 2 x lo9 colony forming (7). These results suggest that the neonatal pulmonary vascula- unitstkg of Group B streptococci over a 30-min period. ture may respond to bacteremia differently from that of adults. Pulmonary arterial pressure rose from 14 ? 2.8 to 38 ? The relationship between Ppa and the matching of alveolar 6.7 torr after 20 min of the bacterial infusion (p< 0.01). ventilation and pulmonary perfusion, a major determinant of During the same period, cardiac output fell from 295 to arterial oxygenation during room air breathing (8), has not been 184 ml/kg/min (p< 0.02). Arterial Po2 declined from 97 studied in newborns. The predictable rise in Ppa with an infusion 2 7 to 56 2 11 torr (p< 0.02) and mixed venous Po2 fell of group B streptococcus offers an opportunity to delineate the from 39.6 2 5 to 28 2 8 torr (p< 0.05).
    [Show full text]
  • Gas-Liquid Hollow Fiber Membrane Contactors for Different Applications
    Review Gas-Liquid Hollow Fiber Membrane Contactors for Different Applications Stepan D. Bazhenov 1,*, Alexandr V. Bildyukevich 2 and Alexey V. Volkov 1 1 A.V. Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow 119991, Russia; [email protected] 2 Institute of Physical Organic Chemistry, National Academy of Sciences of Belarus, Minsk 220072, Belarus; [email protected] * Correspondence: [email protected]; Tel.: +7-495-647-5927 (ext. 202) Received: 14 September 2018; Accepted: 2 October 2018; Published: 10 October 2018 Abstract: Gas-liquid membrane contactors that were based on hollow fiber membranes are the example of highly effective hybrid separation processes in the field of membrane technology. Membranes provide a fixed and well-determined interface for gas/liquid mass transfer without dispensing one phase into another while their structure (hollow fiber) offers very large surface area per apparatus volume resulted in the compactness and modularity of separation equipment. In many cases, stated benefits are complemented with high separation selectivity typical for absorption technology. Since hollow fiber membrane contactors are agreed to be one of the most perspective methods for CO2 capture technologies, the major reviews are devoted to research activities within this field. This review is focused on the research works carried out so far on the applications of membrane contactors for other gas-liquid separation tasks, such as water deoxygenation/ozonation, air humidity control, ethylene/ethane separation, etc. A wide range of materials, membranes, and liquid solvents for membrane contactor processes are considered. Special attention is given to current studies on the capture of acid gases (H2S, SO2) from different mixtures.
    [Show full text]
  • Gas Exchange in the Prone Posture
    RESPIRATORY CARE Paper in Press. Published on May 30, 2017 as DOI: 10.4187/respcare.05512 Gas Exchange in the Prone Posture Nicholas J Johnson MD, Andrew M Luks MD, and Robb W Glenny MD Introduction Overview of Gas Exchange Lung Structure Normal Exchange of Oxygen and Carbon Dioxide Abnormal Exchange of Oxygen and Carbon Dioxide Gas Exchange in the Prone Posture Under Normal Conditions Spatial Distribution of Ventilation Spatial Distribution of Perfusion Ventilation and Perfusion Matching Mechanisms by Which the Prone Posture Improves Gas Exchange in Animal Models of ARDS Additional Physiologic Effects of the Prone Posture Clinical Trials Summary The prone posture is known to have numerous effects on gas exchange, both under normal condi- tions and in patients with ARDS. Clinical studies have consistently demonstrated improvements in oxygenation, and a multi-center randomized trial found that, when implemented within 48 h of moderate-to-severe ARDS, placing subjects in the prone posture decreased mortality. Improve- ments in gas exchange occur via several mechanisms: alterations in the distribution of alveolar ventilation, redistribution of blood flow, improved matching of local ventilation and perfusion, and reduction in regions of low ventilation/perfusion ratios. Ventilation heterogeneity is reduced in the prone posture due to more uniform alveolar size secondary to a more uniform vertical pleural pressure gradient. The prone posture results in more uniform pulmonary blood flow when com- pared with the supine posture, due to an anatomical bias for greater blood flow to dorsal lung regions. Because both ventilation and perfusion heterogeneity decrease in the prone posture, gas exchange improves.
    [Show full text]
  • Gas Exchange and Gas Transfer
    Gas exchange and gas transfer •Red: important •Black: in male / female slides •Pink: in female slides only Editing file •Blue: in male slides only •Yellow: notes •Gray: extra information Twitter account •Textbook: Guyton + Linda Objectives 1. Define partial pressure of a gas 2. Understand that the pressure exerted by each gas in a mixture of gases is independent of the pressure exerted by the other gases (Dalton's Law) 3. Understand that gases in a liquid diffuse from higher partial pressure to lower partial pressure (Henry’s Law) 4. Describe the factors that determine the concentration of a gas in a liquid. 5. Describe the components of the alveolar-capillary membrane (i.e., what does a molecule of gas pass through). 6. Knew the various factors determining gas transfer: - Surface area, thickness, partial pressure difference, and diffusion coefficient of gas 7. State the partial pressures of oxygen and carbon dioxide in the atmosphere, alveolar gas, at the end of the pulmonary capillary, in systemic capillaries, and at the beginning of a pulmonary capillary. Gas exchange through the respiratory membrane After the alveoli are ventilated with fresh air, the next step in the respiratory process is diffusion of oxygen from the alveoli into the pulmonary blood and diffusion of carbon dioxide in the opposite direction, out of the blood. Female’s slides only Composition of alveolar air and its relation to atmospheric air: The dry atmospheric air Alveolar air is partially O2 is constantly CO2 constantly diffuses enters the respiratory replaced by atmospheric absorbed from the from the pulmonary passage is humidified air with each breath.
    [Show full text]
  • Lipid–Protein and Protein–Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis
    International Journal of Molecular Sciences Review Lipid–Protein and Protein–Protein Interactions in the Pulmonary Surfactant System and Their Role in Lung Homeostasis Olga Cañadas 1,2,Bárbara Olmeda 1,2, Alejandro Alonso 1,2 and Jesús Pérez-Gil 1,2,* 1 Departament of Biochemistry and Molecular Biology, Faculty of Biology, Complutense University, 28040 Madrid, Spain; [email protected] (O.C.); [email protected] (B.O.); [email protected] (A.A.) 2 Research Institut “Hospital Doce de Octubre (imasdoce)”, 28040 Madrid, Spain * Correspondence: [email protected]; Tel.: +34-913944994 Received: 9 May 2020; Accepted: 22 May 2020; Published: 25 May 2020 Abstract: Pulmonary surfactant is a lipid/protein complex synthesized by the alveolar epithelium and secreted into the airspaces, where it coats and protects the large respiratory air–liquid interface. Surfactant, assembled as a complex network of membranous structures, integrates elements in charge of reducing surface tension to a minimum along the breathing cycle, thus maintaining a large surface open to gas exchange and also protecting the lung and the body from the entrance of a myriad of potentially pathogenic entities. Different molecules in the surfactant establish a multivalent crosstalk with the epithelium, the immune system and the lung microbiota, constituting a crucial platform to sustain homeostasis, under health and disease. This review summarizes some of the most important molecules and interactions within lung surfactant and how multiple lipid–protein and protein–protein interactions contribute to the proper maintenance of an operative respiratory surface. Keywords: pulmonary surfactant film; surfactant metabolism; surface tension; respiratory air–liquid interface; inflammation; antimicrobial activity; apoptosis; efferocytosis; tissue repair 1.
    [Show full text]
  • Gas Exchange and Respiratory Function
    LWBK330-4183G-c21_p484-516.qxd 23/07/2009 02:09 PM Page 484 Aptara Gas Exchange and 5 Respiratory Function Applying Concepts From NANDA, NIC, • Case Study and NOC A Patient With Impaired Cough Reflex Mrs. Lewis, age 77 years, is admitted to the hospital for left lower lobe pneumonia. Her vital signs are: Temp 100.6°F; HR 90 and regular; B/P: 142/74; Resp. 28. She has a weak cough, diminished breath sounds over the lower left lung field, and coarse rhonchi over the midtracheal area. She can expectorate some sputum, which is thick and grayish green. She has a history of stroke. Secondary to the stroke she has impaired gag and cough reflexes and mild weakness of her left side. She is allowed food and fluids because she can swallow safely if she uses the chin-tuck maneuver. Visit thePoint to view a concept map that illustrates the relationships that exist between the nursing diagnoses, interventions, and outcomes for the patient’s clinical problems. LWBK330-4183G-c21_p484-516.qxd 23/07/2009 02:09 PM Page 485 Aptara Nursing Classifications and Languages NANDA NIC NOC NURSING DIAGNOSES NURSING INTERVENTIONS NURSING OUTCOMES INEFFECTIVE AIRWAY CLEARANCE— RESPIRATORY MONITORING— Return to functional baseline sta- Inability to clear secretions or ob- Collection and analysis of patient tus, stabilization of, or structions from the respiratory data to ensure airway patency improvement in: tract to maintain a clear airway and adequate gas exchange RESPIRATORY STATUS: AIRWAY PATENCY—Extent to which the tracheobronchial passages remain open IMPAIRED GAS
    [Show full text]
  • The Respiratory System
    The Respiratory System Dr. Ali Ebneshahidi © 2009 Ebneshahidi Functions of The Respiratory System . To allow gases from the environment to enter the bronchial tree through inspiration by expanding the thoracic volume. To allow gas exchange to occur at the respiratory membrane, so that oxygen diffuses into the blood while carbon dioxide diffuses into the bronchial tree. To permit gases in the lungs to be eliminated through expiration by decreasing the thoracic volume. © 2009 Ebneshahidi General anatomy of The respiratory System . Consists of a tube that divides into small branching tubes in the lungs: External nares → nasal cavity → nasaopharynx → laryngopharynx → larynx → trachea → primary bronchi → lungs (secondary bronchi → tertiary bronchi → bronchioles → alveolar sacs → alveoli). © 2009 Ebneshahidi Lungs . Cone – shaped organs located in the thoracic cavity. Thoracic cavity is lined with a body membrane called parietal pleura, while the surface of lungs is covered with visceral pleura. The thin space between the two pleural membranes is called pleural cavity which is filled with a clear fluid called plural fluid to minimize friction between the tissues and to provide surface tension in the pleural cavity. [water molecules in the pleural fluid allow the two pleural membranes to adhere to one another, to prevent collapsing of the lungs]. A chemical substance called surfactant secreted by the lungs also facilitate the surface tension. © 2009 Ebneshahidi The respiratory Tract – Bronchial Tree © 2009 Ebneshahidi The Respiratory Tract © 2009 Ebneshahidi . The histology along the respiratory tract changes – from the trachea to the tertiary bronchi, the tract is lined with ciliated pseudostratified columnar epithelium, smooth muscle and cartilage rings; the bronchioles are lined with cuboidal epithelium; and from the alveolar ducts to the alveoli, the tract is lined with simple squamous epithelium.
    [Show full text]
  • Principles of Oxygenator Function: Gas Exchange, Heat Transfer, and Operation
    Thoracic Key Fastest Thoracic Insight Engine Home Log In Register Categories » More References » About Gold Membership Contact Search... Principles of Oxygenator Function: Gas Exchange, Heat Transfer, and Operation Principles of Oxygenator Function: Gas Exchange, Heat Transfer, and Operation Michael H. Hines INTRODUCTION Since the early 1950s when the development of a heart-lung machine first began, there has been a tremendous evolution of devices and machinery for cardiac support (1,2). However, despite the diversity in designs through the years, they all contain three essential components: a mechanism to circulate the blood, a method of gas exchange for oxygen and carbon dioxide, and some mechanism for temperature control. Chapter 2 has covered the first important component, and we will now focus on the two subsequent elements: gas exchange and heat transfer. And while it is referred to as the “oxygenator,” we must recognize that it is responsible for the movement of both oxygen in, as well as carbon dioxide out. The discussion will start with a basic review of the principles of physics, and then we will apply those principles to the devices used specifically in extracorporeal support, including cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO). You may notice as you go through this chapter that there is a scarcity of trade and manufacturer names. The author has intentionally avoided using these. The intent was primarily to focus on the physiology, physics, and chemistry of the oxygenator and heat exchanger, but also to emphasize the fact that there are a large number of manufacturers producing many products that have all been shown to function extremely well.
    [Show full text]
  • How Am I Supposed to Breathe with No Air? Nikki Lewis, CVT, VTS (ECC) 2016 ISVMA Conference Proceedings
    How am I supposed to breathe with no air? Nikki Lewis, CVT, VTS (ECC) 2016 ISVMA Conference Proceedings When the respiratory center begins to fail, functions such as oxygenation and elimination of carbon dioxide are compromised. This results in hypercapnia and hypoxemia. The major components of gas exchange are the lungs and the respiratory muscles which provide a force or pump to the lungs. If either one of these primary functions are compromised it can result in respiratory failure. Assessment of oxygenation and ventilation To accurately define respiratory failure, you must evaluate arterial blood gasses. A partial pressure of oxygen (PaO2) that’s less than 60mmHg and a partial pressure of carbon dioxide (PaCO2) of greater than 50mmHg define respiratory failure. The term partial pressure refers to the total pressure exerted by a single molecule of this gas. There are several molecules all combined in a cell; however, the partial pressure is the single gas’ pressure. Pulse oximetry is another method of quantifying oxygenation, although not as precise as arterial blood gasses. This is an indirect measurement of PaO2. A pulse oximetry measurement of 91-100% typically reflects a PaO2 of 80-100mmHg, which is a normal value. If the pulse oximetry falls below 91% this results in a rapid drop of the PaO2. Several factors can make the pulse oximetry reading false. These include pigmented tissues, motion and methemoglobinemia. Lastly, the measurement of end-tidal CO2 (ETCO2) will evaluate proper gas exchange. This is done by intubating the patient and using capnography. Capnography measures the expired CO2. Normal ETCO2 range is 35-45mmHg.
    [Show full text]
  • Introduction to the Respiratory System
    C h a p t e r 15 The Respiratory System PowerPoint® Lecture Slides prepared by Jason LaPres Lone Star College - North Harris Copyright © 2010 Pearson Education, Inc. Copyright © 2010 Pearson Education, Inc. Introduction to the Respiratory System • The Respiratory System – Cells produce energy: • For maintenance, growth, defense, and division • Through mechanisms that use oxygen and produce carbon dioxide Copyright © 2010 Pearson Education, Inc. Introduction to the Respiratory System • Oxygen – Is obtained from the air by diffusion across delicate exchange surfaces of the lungs – Is carried to cells by the cardiovascular system, which also returns carbon dioxide to the lungs Copyright © 2010 Pearson Education, Inc. 15-1 The respiratory system, composed of conducting and respiratory portions, has several basic functions Copyright © 2010 Pearson Education, Inc. Functions of the Respiratory System • Provides extensive gas exchange surface area between air and circulating blood • Moves air to and from exchange surfaces of lungs • Protects respiratory surfaces from outside environment • Produces sounds • Participates in olfactory sense Copyright © 2010 Pearson Education, Inc. Components of the Respiratory System • The Respiratory Tract – Consists of a conducting portion • From nasal cavity to terminal bronchioles – Consists of a respiratory portion • The respiratory bronchioles and alveoli The Respiratory Tract Copyright © 2010 Pearson Education, Inc. Components of the Respiratory System • Alveoli – Are air-filled pockets within the lungs:
    [Show full text]
  • Respiratory Gas Exchange in the Lungs
    RESPIRATORY GAS EXCHANGE Alveolar PO2 = 105 mmHg; Pulmonary artery PO2 = 40 mmHg PO2 gradient across respiratory membrane 65 mmHg (105 mmHg – 40 mmHg) Results in pulmonary vein PO2 ~100 mmHg Partial Pressures of Respiratory Gases • According to Dalton’s law, in a gas mixture, the pressure exerted by each individual gas is independent of the pressures of other gases in the mixture. • The partial pressure of a particular gas is equal to its fractional concentration times the total pressure of all the gases in the mixture. • Atmospheric air : Oxygen constitutes 20.93% of dry atmospheric air. At a standard barometric pressure of 760 mm Hg, PO2 = 0.2093 × 760 mm Hg = 159 mm Hg Similarly , PCO2= 0.3 mm Hg PN2= 600 mm Hg Inspired Air: PIO2= FIO2 (PB-PH2O)= 0.2093 (760-47)= 149 mm Hg PICO2= 0.3 mm Hg PIN2= 564 mm Hg Alveolar air at standard barometric pressure • 2.5 to 3 L of gas is already in the lungs at the FRC and the approximately 350 mL per breath enters the alveoli with every breath. • About 250 mL of oxygen continuously diffuses from the alveoli into the pulmonary capillary blood per minute at rest and 200 mL of carbon dioxide diffuses from the mixed venous blood in the pulmonary capillaries into the alveoli per minute. • The PO2 and PCO2 of mixed venous blood are about 40 mm Hg and 45 to 46 mm Hg, respectively • The PO2 and PCO2 in the alveolar air are determined by the alveolar ventilation, the pulmonary capillary perfusion, the oxygen consumption, and the carbon dioxide production.
    [Show full text]