DOCSLIB.ORG

Central Venous Minus Arterial Carbon Dioxide Pressure To

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Central Venous Minus Arterial Carbon Dioxide Pressure To ARTIGO DE REVISÃO Arnaldo Dubin1,2 , Mario Omar Pozo3, Javier Hurtado4,5 Proporção entre pressão venosa central menos arterial de dióxido de carbono e conteúdo arterial menos venoso central de oxigênio como indicador de oxigenação tissular: uma revisão narrativa Central venous minus arterial carbon dioxide pressure to arterial minus central venous oxygen content ratio as an indicator of tissue oxygenation: a narrative review 1. Cátedra de Farmacología Aplicada, Facultad de Ciencias Médicas, Universidad Nacional de La Plata - La Plata, Argentina. 2. Servicio de Terapia Intensiva, Sanatorio RESUMO provavelmente não demandaria maiores Otamendi - Buenos Aires, Argentina. monitoramentos. Visto que o início 3. Servicio de Terapia Intensiva, Hospital A proporção entre pressão venosa do metabolismo anaeróbico é indicado Británico - Buenos Aires, Argentina. central menos arterial de dióxido de 4. Servicio de Terapia Intensiva, Hospital pelo aumento súbito do quociente Español-ASSE - Montevidéu, Uruguai. carbono e conteúdo de oxigênio arterial respiratório e que a faixa normal do 5. Departamento de Fisiopatología, Facultad menos venoso central (Pcv-aCO2/Ca-cvO2) quociente respiratório é ampla, o uso de Medicina, Universidad de la República - foi proposta como marcador substituto do ponto de corte definido como 1,4 Montevidéu, Uruguai. para quociente respiratório e indicador para Pcv-aCO2/Ca-cvO2 não faz sentido. de oxigenação tissular. Alguns pequenos Estudos experimentais demonstraram estudos observacionais identificaram que que a Pcv-aCO2/Ca-cvO2 é mais dependente Pcv-aCO2/Ca-cvO2 acima de 1,4 se associa de fatores que modificam a dissociação com hiperlactatemia, dependência do dióxido de carbono da hemoglobina de suprimento de oxigênio e maior do que do quociente respiratório, e mortalidade. Mais ainda, a Pcv-aCO2/ o quociente respiratório e Pcv-aCO2/ Ca-cvO2 foi incorporada a algoritmos Ca-cvO2 podem ter comportamentos para avaliação da oxigenação tissular distintos. Estudos conduzidos em e ressuscitação. Contudo, a evidência pacientes críticos demonstraram para estas recomendações é bastante resultados controvertidos com relação limitada e de baixa qualidade. O objetivo à capacidade da Pcv-aCO2/Ca-cvO2 para desta revisão narrativa foi analisar as predizer o desfecho, hiperlactatemia, bases metodológicas, os fundamentos anomalias microvasculares e dependência fisiopatológicos e a evidência experimental de suprimento de oxigênio. Um estudo e clínica para dar suporte à utilização randomizado controlado também da Pcv-aCO2/Ca-cvO2 como marcador demonstrou que a Pcv-aCO2/Ca-cvO2 é Conflitos de interesse: Nenhum. substituto para quociente respiratório. inútil como alvo para ressuscitação. A Pcv- De um ponto de vista fisiopatológico, CO /C O deve ser interpretada com Submetido em 28 de abril de 2019 a 2 a-cv 2 o aumento do quociente respiratório cautela em pacientes críticos. Aceito em 9 de junho de 2019 secundariamente a reduções críticas Autor correspondente: no transporte de oxigênio é um evento Descritores: Anaerobiose; Respira- Arnaldo Dubin dramático e com risco à vida. Entretanto, ção; Oxigenação; Dióxido de carbono; Cátedra de Farmacologia Aplicada este evento é facilmente observável e Quociente respiratório; Estado terminal Facultad de Ciencias Médicas, Universidad Nacional de La Plata Calle 42 Nº 577 (1900) La Plata, Argentina E-mail: [email protected] INTRODUÇÃO Editor responsável: Luciano César Pontes de Azevedo Em pacientes críticos, a hipóxia tissular é um importante mecanismo DOI: 10.5935/0103-507X.20200017 de falência de múltiplos órgãos e morte. Assim, a detecção e a correção do metabolismo anaeróbico são tarefas cruciais. Infelizmente, faltam referências que sejam padrão-ouro para a avaliação da oxigenação tissular. Algumas Rev Bras Ter Intensiva. 2020;32(1):115-122 Este é um artigo de acesso aberto sob licença CC BY (https://creativecommons.org/licenses/by/4.0/). 116 Dubin A, Pozo MO, Hurtado J variáveis, comumente utilizadas no monitoramento de pacientes críticos, podem ser indicadores enganosos do metabolismo anaeróbico. O lactato é um excelente preditor de desfechos,(1,2) porém não é um marcador confiável para hipóxia tissular.(3) O monitoramento clínico da perfusão periférica é uma abordagem atraente e viável, porém também tem limitações.(4) Embora a saturação venosa central de oxigênio (ScvO2) e a diferença entre a pressão parcial de dióxido de carbono (PCO2) venosa central menos a arterial (Pcv-aCO2) possam rastrear modificações no débito cardíaco, seu papel na avaliação da adequação da oxigenação tissular é controvertido.(5,6) Lamentavelmente, a avaliação da PCO2 tissular não está mais disponível, e o monitoramento da microcirculação ainda é restrita ao campo da pesquisa.(7) Assim, é necessária a busca de novas abordagens. Na fisiologia do exercício, a análise dos gases expirados permite a identificação de metabolismo anaeróbico. O aumento da carga de trabalho se associa com elevações paralelas na produção de dióxido de carbono (VCO2) e consumo de oxigênio (VO2). A inclinação da curva deste relacionamento é o quociente respiratório (QR = VCO2/VO2). O QR permanece inicialmente constante em condições anaeróbicas. Em algum momento, Figura 1 – Consumo de oxigênio, produção de dióxido de carbono e quociente entretanto, os aumentos no VCO2 excedem os do VO2, e o QR aumenta. Este ponto de inflexão corresponde respiratório em função do transporte de oxigênio. (A) Relacionamento entre consumo de oxigênio e produção de dióxido de carbono com transporte de ao desenvolvimento de hiperlactatemia e é conhecido oxigênio. (B) Relacionamento do quociente respiratório com o transporte como limiar anaeróbico.(8) No contexto do outro extremo de oxigênio. Reduções críticas no transporte de oxigênio se associam com fisiológico, durante a dependência de suprimento de diminuições progressivas no consumo de oxigênio e na produção de dióxido de carbono. As reduções na produção de dióxido de carbono são menores do oxigênio, as reduções no VO2 são mais altas do que as no que as no consumo de oxigênio em razão do início da produção de dióxido de VCO2. Consequentemente, seguem-se bruscas elevações carbono anaeróbica secundária ao tamponamento com bicarbonato dos prótons no QR(9-11) (Figura 1). Em ambas as situações, exercício gerados anaerobicamente. Consequentemente seguem-se aumentos abruptos no quociente respiratório. O - oxigênio; CO - dióxido de carbono. anaeróbico e diminuições críticas no transporte de 2 2 oxigênio, o fenômeno de base é o surgimento de VCO2 anaeróbico secundário ao tamponamento por bicarbonato (13) desfavoráveis. Mais ainda, a Pcv-aCO2/Ca-cvO2 foi dos prótons gerados anaerobicamente. Assim, o aumento incorporada a algoritmos para avaliação da oxigenação do QR indica metabolismo anaeróbico em curso. tissular e ressuscitação.(16-18) Contudo, a evidência para estas Consequentemente, a mensuração do QR surge recomendações é bastante limitada e de baixa qualidade. como abordagem atraente para a identificação de hipóxia O objetivo desta revisão narrativa foi analisar as bases tissular global. Entretanto, nem sempre estão disponíveis metodológicas, os fundamentos fisiopatológicos, e a equipamentos de avaliação metabólica nas condições de evidência experimental e clínica que dão suporte ao uso uma unidade de terapia intensiva. Além disto, o uso de de Pcv-aCO2/Ca-cvO2 como marcador substituto do QR. uma elevada fração inspirada de oxigênio pode interferir Avaliamos, de forma abrangente, a evidência existente nas mensurações.(12) Para solucionar este problema, alguns para a associação entre Pcv-aCO2/Ca-cvO2 e desfechos em pesquisadores propuseram uma simplificação da equação pacientes críticos. Tivemos como alvo determinar se, de Fick, adaptada para o dióxido de carbono, a P CO cv-a 2 em pacientes críticos, a Pcv-aCO2/Ca-cvO2 se associa com para o conteúdo arterial menos venoso central de oxigênio mortalidade mais elevada e é um preditor melhor do (Pcv-aCO2/Ca-cvO2) como substituto para o QR. Alguns desfecho do que o lactato arterial. Revisamos também o pequenos estudos observacionais identificaram que P CO / cv-a 2 papel da Pcv-aCO2/Ca-cvO2 para predizer dependência de (13) Ca-cvO2 acima de 1,4 se associou com hiperlactatemia, suprimento de oxigênio, assim como seu uso como alvo dependência de suprimento de oxigênio,(14,15) e desfechos na ressuscitação. Rev Bras Ter Intensiva. 2020;32(1):115-122 Proporção entre pressão venosa central menos arterial de dióxido de carbono e conteúdo arterial 117 menos venoso central de oxigênio como indicador de oxigenação tissular QUESTÕES METODOLÓGICAS Uso da pressão em vez do conteúdo de dióxido de carbono para cálculo da proporção O uso da Pcv-aCO2/Ca-cvO2 como marcador substituto para o QR e oxigenação tissular se apoia em alguns O relacionamento entre conteúdo e pressão de pressupostos. Primeiramente, o QR é a proporção entre dióxido de carbono é complexo. Em termos gerais, é VCO2 e VO2: um relacionamento curvilíneo. Isto implica que, para a faixa mais elevada de conteúdo de dióxido de carbono, o QR = VCO2/VO2 (Equação 1) relacionamento se torna aplanado. Dessa forma, novos aumentos no conteúdo de dióxido de carbono induzem Segundo a equação de Fick, este cálculo pode ser maior aumento da PCO2. A curva de dissociação de dióxido reorganizado assim: de carbono pode ser modificada por alterações no excesso de base, níveis de hemoglobina e saturação de oxigênio QR = Q x Cmv-aCO2/Q x Ca-mvO2 (Equação 2) (efeito de Haldane) (Figura 2). Estes fatores modificam significantemente a Pcv-aCO2/Ca-cvO2,
Load more

Recommended publications
  • Measurement of the Respiratory Quotient of Peat
    Utah State University DigitalCommons@USU Hydroponics/Soilless Media Research 8-10-2012 Measurement of the Respiratory Quotient of Peat Jake Nelson Follow this and additional works at: https://digitalcommons.usu.edu/cpl_hydroponics Part of the Plant Sciences Commons Recommended Citation Nelson, Jake, "Measurement of the Respiratory Quotient of Peat" (2012). Hydroponics/Soilless Media. Paper 5. https://digitalcommons.usu.edu/cpl_hydroponics/5 This Article is brought to you for free and open access by the Research at DigitalCommons@USU. It has been accepted for inclusion in Hydroponics/Soilless Media by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. Measurement of the respiratory quotient of peat Jake Nelson 8/10/2012 BIOL 5800 Undergraduate Research Summer 2010 Introduction Respiratory quotient (RQ) is the ratio of CO produced to O consumed by an organism. Complete respiration 2 2 of glucose will give an RQ of 1 as described by the formula C H O +nO →nCO +nH O. The respiration of n 2n n 2 2 2 molecules with lower oxygen content, such as lipids, give RQ values of less than one, whereas in cases of anaerobic metabolism, an increase in biomass or the respiration of substances such as humic, oxalic and citric acids the respiratory quotient can be greater than one. In complex systems such as soil, Dilly (2003) found that the RQ varied dramatically, and changed within the same soil under varying conditions. Similarly, Hollender et al. (2003) found RQ was informative in determining the underlying metabolic mechanisms, such as nitrification processes. Dilly (2004), studied the effects of various organic compounds on RQ, and found that beech forest soils amended with cellulose or humic acid maintained RQ values greater than one for more than 20 days after application.
    [Show full text]
  • Respiratory Physiology for the Anesthesiologist
    REVIEW ARTICLE Deborah J. Culley, M.D., Editor ABSTRACT Respiratory function is fundamental in the practice of anesthesia. Knowledge of basic physiologic principles of respiration assists in the proper implemen- tation of daily actions of induction and maintenance of general anesthesia, Respiratory Physiology delivery of mechanical ventilation, discontinuation of mechanical and pharma- cologic support, and return to the preoperative state. The current work pro- Downloaded from http://pubs.asahq.org/anesthesiology/article-pdf/130/6/1064/455191/20190600_0-00035.pdf by guest on 24 September 2021 for the Anesthesiologist vides a review of classic physiology and emphasizes features important to the anesthesiologist. The material is divided in two main sections, gas exchange Luca Bigatello, M.D., Antonio Pesenti, M.D. and respiratory mechanics; each section presents the physiology as the basis ANESTHESIOLOGY 2019; 130:1064–77 of abnormal states. We review the path of oxygen from air to the artery and of carbon dioxide the opposite way, and we have the causes of hypoxemia and of hypercarbia based on these very footpaths. We present the actions nesthesiologists take control of the respiratory func- of pressure, flow, and volume as the normal determinants of ventilation, and Ation of millions of patients throughout the world each we review the resulting abnormalities in terms of changes of resistance and day. We learn to maintain gas exchange and use respiration compliance. to administer anesthetic gases through the completion of (ANESTHESIOLOGY 2019; 130:1064–77) surgery, when we return this vital function to its legitimate owners, ideally with a seamless transition to a healthy post- operative course.
    [Show full text]
  • Respiratory Support
    Intensive Care Nursery House Staff Manual Respiratory Support ABBREVIATIONS FIO2 Fractional concentration of O2 in inspired gas PaO2 Partial pressure of arterial oxygen PAO2 Partial pressure of alveolar oxygen PaCO2 Partial pressure of arterial carbon dioxide PACO2 Partial pressure of alveolar carbon dioxide tcPCO2 Transcutaneous PCO2 PBAR Barometric pressure PH2O Partial pressure of water RQ Respiratory quotient (CO2 production/oxygen consumption) SaO2 Arterial blood hemoglobin oxygen saturation SpO2 Arterial oxygen saturation measured by pulse oximetry PIP Peak inspiratory pressure PEEP Positive end-expiratory pressure CPAP Continuous positive airway pressure PAW Mean airway pressure FRC Functional residual capacity Ti Inspiratory time Te Expiratory time IMV Intermittent mandatory ventilation SIMV Synchronized intermittent mandatory ventilation HFV High frequency ventilation OXYGEN (Oxygen is a drug!): A. Most infants require only enough O2 to maintain SpO2 between 87% to 92%, usually achieved with PaO2 of 40 to 60 mmHg, if pH is normal. Patients with pulmonary hypertension may require a much higher PaO2. B. With tracheal suctioning, it may be necessary to raise the inspired O2 temporarily. This should not be ordered routinely but only when the infant needs it. These orders are good for only 24h. OXYGEN DELIVERY and MEASUREMENT: A. Oxygen blenders allow O2 concentration to be adjusted between 21% and 100%. B. Head Hoods permit non-intubated infants to breathe high concentrations of humidified oxygen. Without a silencer they can be very noisy. C. Nasal Cannulae allow non-intubated infants to breathe high O2 concentrations and to be less encumbered than with a head hood. O2 flows of 0.25-0.5 L/min are usually sufficient to meet oxygen needs.
    [Show full text]
  • Effect of Positive End-Expiratory Pressure on Intrapulmonary Shunt at Different Levels of Fractional Inspired Oxygen
    Thorax: first published as 10.1136/thx.35.3.181 on 1 March 1980. Downloaded from Thorax, 1980, 35, 181-186 Effect of positive end-expiratory pressure on intrapulmonary shunt at different levels of fractional inspired oxygen A OLIVEN, U TAITELMAN, F ZVEIBIL, AND S BURSZTEIN From the Intensive Care Department, Rambam Medical Centre, Haifa, Israel ABSTRACT In 10 patients undergoing ventilation, venous admixture was measured at different values of positive end-expiratory pressure (PEEP). The measurements were performed at the level of fractional inspired oxygen (FIO2) at which each patient was ventilated, and at FIo2=1. In patients ventilated at FIo2 between 0-21 and 0 3 venous admixture was not modified by PEEP, while in patients ventilated with FIO2 between 0'4 and 0-6, venous admixture decreased significantly (p<0 01). With FIO2=1, increased PEEP produced a reduction in venous admixture in all cases (p < 0 .05). These observations suggest that in patients similar to ours, PEEP does not reduce venous admixture at low levels of Fio2 (0-21-0.3), and the observed reduction with PEEP at FIO2= I may be misinterpreted. copyright. In patients with acute respiratory failure, and vital signs and minute volume were positive end-expiratory pressure (PEEP) has repeatedly checked, in order to confirm steady been said to reduce pulmonary venous admixture state condi-tions. Blood samples were drawn and improve arterial blood oxygenation.13 The simultaneously into heparinised glass syringes efficiency of PEEP can thus be -evaluated by its from an indwelling arterial line and from a http://thorax.bmj.com/ influence on venous admixture.
    [Show full text]
  • Respiratory Equations – Behind the Numbers
    Southern African Journal of Anaesthesia and Analgesia. 2020;26(6 Suppl 3):S90-93 https://doi.org/10.36303/SAJAA.2020.26.6.S3.2546 South Afr J Anaesth Analg Open Access article distributed under the terms of the ISSN 2220-1181 EISSN 2220-1173 Creative Commons License [CC BY-NC 3.0] © 2020 The Author(s) http://creativecommons.org/licenses/by-nc/3.0 FCA 1 REFRESHER COURSE Respiratory equations – behind the numbers T Leonard Department of Anaesthesia, School of Clinical Medicine, Faculty of Health Sciences, Chris Hani Baragwanath Academic Hospital, University of the Witwatersrand, South Africa Corresponding author, email: [email protected] Summary Candidates for the FCA 1 exam will come across dozens of equations that eventually all merge into something complicated and daunting. The purpose of this review is to highlight some of the respiratory equations that are important and that candidates find confusing and explain the mathematical and physiological principles behind them. Keywords: equations, respiratory physiology, ventilation, perfusion, dead space Introduction VD / VT = (PACO2 – PECO2) / PACO2 P CO partial pressure of CO in alveolar gas There are many equations that candidates will come across in A 2 2 their study of respiratory physiology. These equations describe PECO2 partial pressure of CO2 in the total mixed principles of ventilation, perfusion and diffusion within the res- exhaled breath piratory system. This review attempts to explain the origins and A further modification was made by Henrik Enghoff due to make sense
    [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]
  • The Oxylgen Coneenitration of the Air Was About 5 Per Cent.; It Roseto Higher
    EFFECT OF OXYGEN CONCENTRATION ON THE RESPIRATION OF SOME VEGETABLES' HANS PLATENIUS (WITH SEVEN FIGURES) Introduction Commiiiiercial methods of storing fruits and vegetables in modified atmos- phere are based on the fact that respiration, ripening, and other physiolog- ical processes can be retarded by maintaining an atmosphere in which the oxygen content is lower and the carbon dioxide concentration higher than in normal air. Many investigators assume that it is the presence of carbon dioxide rather than the limited oxygen supply which has a depressing effect on the physiological activity of the plant tissue. In fact, modified atmos- phere storage is frequently spoken of as "carbon dioxide storage." There is reason to believe, however, that the importance of a limited oxygen supply itself has been underestimated. Indirect evidence for this view is found in the results of THORNTON (8) which make it clear that the presence of carbon dioxide in the storage atmosphere does nlot always depress the respiration of plant material. On the contrary, he found that the respi- ration rate of potatoes and onions was markedly increased when held in an atmosphere of normiial oxygen content to which varying quantities of carbon dioxide had been added. On the other hand, the same treatment had a depressing effect on the respiratory activity of asparagus and strawberries. In the literature few experiments are reported which deal exclusively with the effect of low concentrations of oxygen on the respiration of plant tissue. Somiie of these experiments were conducted for a few hours only, and there is no assurance that the results would have been the same had the storage period been extended to several days.
    [Show full text]
  • High Respiratory Quotient Is Associated with Increases in Body Weight and Fat Mass in Young Adults
    European Journal of Clinical Nutrition (2016) 70, 1197–1202 © 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved 0954-3007/16 www.nature.com/ejcn ORIGINAL ARTICLE High respiratory quotient is associated with increases in body weight and fat mass in young adults RP Shook1, GA Hand2, AE Paluch3, X Wang3, R Moran4, JR Hébert4,5,6, JM Jakicic7 and SN Blair3,4 BACKGROUND/OBJECTIVES: Metabolic disturbances, such as reduced rates of fat oxidation (high respiratory quotient (RQ)) or low energy expenditure (low resting metabolic rate (RMR)), may contribute to obesity. The objective was to determine the association between a high RQ or a low RMR and changes in body weight and body composition over 1 year. SUBJECTS/METHODS: We measured RQ and RMR in 341 adults using indirect calorimetry, along with body weight/body composition using dual-energy X-ray absorptiometery, energy expenditure using an arm-based activity monitor and energy intake using dietary recalls. Participants were classified into low, moderate or high RQ and RMR (adjusted for age, sex, race and body composition) groups according to tertiles by sex. Follow-up measurements were completed every 3 months. RESULTS: Individuals with a high RQ had larger gains in body weight and fat mass compared with individuals with a low/moderate RQ at month 3, and increases in fat mass were more than double among individuals with a high RQ at 12 months (1.3 ± 3.0 vs 0.6 ± 3.7 kg, P = 0.03). Individuals with a low RMR did not gain more body weight nor fat mass compared with individuals with a moderate/high RMR.
    [Show full text]
  • A Carbon Monoxide Transport Model of the Human Respiratory System Applied to …
    A Carbon Monoxide Transport Model of The Human Respiratory System Applied to … A Carbon Monoxide Transport Model Cyro Albuquerque Neto of the Human Respiratory System [email protected] Applied to Urban Atmosphere Jurandir Itizo Yanagihara Senior Member, ABCM Exposure Analysis [email protected] The aim of this work is to analyze the carbon monoxide (CO) transport in the human body submitted to several physical activity levels. A complete mathematical model of the human respiratory system was developed, considering the exchanges of CO, oxygen (O2) and Fábio Turri carbon dioxide (CO2) in the lung, blood and tissues. The human body was divided in the [email protected] following compartments: alveolar, pulmonary capillaries, arterial, venous, tissue capillary University of Sao Paulo - USP and tissues. The gas transport in the blood and tissues is represented by empirical Escola Politécnica equations. The physiological parameters were described in function of physical activity. Department of Mechanical Engineering The model was validated by comparing its results with experimental data of controlled CO 055809-900 São Paulo, SP, Brazil exposition. The agreement was excellent. CO concentration curves for critical days of São Caetano do Sul city (SP, Brazil) atmosphere were used as model input. The simulation results for some physical activities show that the more intense the activity, the larger the blood carboxyhemoglobin (COHb) level variations. The COHb level was compared with a CO quality air criteria, which showed to be adequate for low and moderate physical activity levels. Keywords: compartment model, carbon monoxide, gas transport, respiratory system, air pollution The models of Selvakumar, Sharan and Singh (1992) and Introduction Sharan and Selvakumar (1999) divide the lung into compartments, one alveolar and several pulmonary capillaries.
    [Show full text]
  • 4. Pulmonary Function Tests and Alveolar Ventilation
    Introductory Human Physiology ©copyright Jennifer Carbrey & Emma Jakoi 4. Pulmonary function tests and alveolar ventilation 8 FORCED EXPIRATORY VITAL CAPACITY TEST 7 provides an indirect assessment of airway X resistance. In this pulmonary function test, the 6 subject inhales to total lung capacity and then 5 exhales into a spirometer as forcefully, rapidly, and VOLUME as completely as possible. The volume expired 4(LITERS) Y under these conditions is called the forced vital 3 capacity (FVC) (Fig 3). 2 Z The forced expiratory vital capacity test also 1 measures the volume exhaled in 1 second, called 0 2 4 6 8 10 the 1-second forced expiratory volume (FEV1). TIME (SECONDS) This value is often expressed as a % of FVC (i.e., FEV1/FVC %). Normally FEV1 is at least 80% of FVC (curve Y). Patients with restrictive lung disease Figure 3. Forced expiratory vital will have a normal value of 80% (curve Z). In patients capacity curves generated by such as asthmatics, who have obstructed airways, individuals X, Y and Z. this value will be reduced (<80%) (curve X). Exchange of Gases in Alveoli & Tissues Respiration involves two processes: (1) Delivery of O2 to and removal of CO2 from the cells of the body. (2) Use of O2 in oxidative metabolism to generate ATP, water, and CO2. In a steady state, the amount of O2 that is consumed by the cells per unit time is equal to the amount of O2 added to the blood in the lungs during the same time period. Likewise the rate at which CO2 is generated by the cells is equal to the rate at which CO2 leaves the blood in the lungs and is exhaled.
    [Show full text]
  • The Respiratory Quotient in Relation to Fat Deposition in Fattening-Growing
    Downloaded from British Journril of' Nutrition (1993), 69, 333-343 333 https://www.cambridge.org/core The respiratory quotient in relation to fat deposition in fattening-growing pigs BY KIRSTEN JAKOBSEN* AND GRETE THORBEKt Nationul Institute of Animal Science, Department of Animal Physiology and Biochemistry, Foulum, PO Box 39, DK-8830 Tjele, Denmark . IP address: (Received 21 February 1991 - Accepted 8 May 1992) 170.106.202.58 The relationship between non-protein respiratory quotient (RQ,,,) and total fat retention (RFAT) or fat retained from synthesized carbohydrates (RFAT(CH0)) was evaluated from experiments with fattening-growing pigs in the live weight (LW) range from 45 to 120 kg. A commercial feed compound , on (31 g fat/kg) was fed at low (LI) or high (HI) feed intake in Expt 1, while a semi-purified diet (9.5 g 29 Sep 2021 at 08:16:21 fat/kg) was given without (LO) or with (HO) supplement of 90 g soya-bean oil/kg in Expt 2. RQ,, was calculated from 24 h measurements of the gas exchange, RFAT from 7 d N and C balances and RFAT(CH0) from differences between RFAT and digested fat. The measurements showed that about 85 % of the total gas exchange was caused by oxidation of non-protein nutrients and the RQ,, varied from 1.00 to 1.34. In Expt 1 RFAT increased with LW from 46 to 141 and from 199 to 335 g/d on LI and HI respectively, whilst in Expt 2 RFAT increased from 191 to 377 and from 267 to 511 g/d on LO , subject to the Cambridge Core terms of use, available at and HO respectively.
    [Show full text]
  • Respiration Quotient Variability: Bacterial Evidence
    Vol. 519: 47–59, 2015 MARINE ECOLOGY PROGRESS SERIES Published January 20 doi: 10.3354/meps11062 Mar Ecol Prog Ser Respiration quotient variability: bacterial evidence V. Romero-Kutzner1,*, T. T. Packard1, E. Berdalet2, S. O. Roy3, J.-P. Gagné4, M. Gómez1 1EOMAR, Grupo de Ecofisiología de Organismos Marinos, Universidad de Las Palmas de Gran Canaria 35017, Spain 2Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain 310 Ryan Court, Embrun, Ontario K0A 1W0, Canada 4Université du Québec à Rimouski, Rimouski, Québec G5L 3A1, Canada ABSTRACT: Respiratory metabolism was compared between 2 different physiological states of acetate- and pyruvate-grown cultures of Pseudomonas nautica and Vibrio natriegens. Here, we analyze 35 h and 520 h experiments in which time-courses of protein, pyruvate, acetate, respira- tory CO2 production (RCO2), respiratory O2 consumption (RO2), isocitrate dehydrogenase (IDH) activity, and potential respiration (Φ) were measured. Respiratory quotients (RQs) were calculated as the ratio of the respiration rates (RCO2/RO2). Such RQs are widely used in ocean ecosystem mod- els, in calculations of carbon flux, and in evaluations of the ocean’s metabolic balance. In all the cultures, the RQ tended to increase. In the case of P. nautica on acetate, the RQ rose nearly an order of magnitude from values below 1 during carbon-substrate sufficiency to values close to 10 during carbon-substrate deficiency. In all the cultures, the respiration rates during the growth period paralleled the biomass increase, but after the substrates were exhausted, the respiration rates fell. In contrast, through this same transition period, the IDH activity and the Φ remained rel- atively high for the first 10 h of carbon-substrate deprivation, and then, these enzyme activities fell slowly, along with the biomass, as the carbon-substrate deprivation continued.
    [Show full text]