ISO TS 16976-3-2011 Respiratory protective devices - Human factors - Part 3 Physiological responses and limitations of oxygen and limitations of carbon dioxide .pdf

1、 Reference number ISO/TS 16976-3:2011(E) ISO 2011TECHNICAL SPECIFICATION ISO/TS 16976-3 First edition 2011-08-15 Respiratory protective devices Human factors Part 3: Physiological responses and limitations of oxygen and limitations of carbon dioxide in the breathing environment Appareils de protecti

2、on respiratoire Facteurs humains Partie 3: Rponses physiologiques et limitations en oxygne et en gaz carbonique dans lenvironnement respiratoire ISO/TS 16976-3:2011(E) COPYRIGHT PROTECTED DOCUMENT ISO 2011 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced

3、 or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01

4、 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2011 All rights reservedISO/TS 16976-3:2011(E) ISO 2011 All rights reserved iiiContents Page Foreword iv Introduction . v 1 Scope 1 2 Terms and definitions, symbols and abbreviated terms . 1 2.1 Terms a

5、nd definitions . 1 2.2 Symbols and abbreviated terms 4 3 Oxygen and carbon dioxide in the breathing environment: physiological responses and limitations . 5 3.1 General . 5 3.2 Oxygen and carbon dioxide gas exchange in the human lung 5 3.3 Oxygen and carbon dioxide transport in the blood . 6 3.4 Oxy

6、gen and carbon dioxide and the control of respiration 8 3.5 Hyperoxia: physiological effects . 9 3.6 Hypoxia: physiological effects . 10 3.7 Hypercarbia: physiological effects 13 3.8 Relevance to the use of respiratory protective devices (RPD) . 16 3.9 Interpretation of results 19 3.10 Significance

7、of results 20 Bibliography 21 ISO/TS 16976-3:2011(E) iv ISO 2011 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out thro

8、ugh ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collabor

9、ates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standa

10、rds. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. In other circumstances, particularly when there is an urgent market

11、requirement for such documents, a technical committee may decide to publish other types of document: an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in an ISO working group and is accepted for publication if it is approved by more than 50 % of the

12、members of the parent committee casting a vote; an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting a vote. An ISO/PAS or ISO/TS is reviewed after

13、 three years in order to decide whether it will be confirmed for a further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed, it is reviewed again after a further three years, at which time it must either be transformed into an Internationa

14、l Standard or be withdrawn. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO/TS 16976-3 was prepared by Technical Committee ISO/TC 94, Personal sa

15、fety Protective clothing and equipment, Subcommittee SC 15, Respiratory protective devices. ISO/TS 16976 consists of the following parts, under the general title Respiratory protective devices Human factors: Part 1: Metabolic rates and respiratory flow rates Part 2: Anthropometrics Part 3: Physiolog

16、ical responses and limitations of oxygen and limitations of carbon dioxide in the breathing environment ISO/TS 16976-3:2011(E) ISO 2011 All rights reserved vIntroduction Due to the nature of their occupations, millions of workers worldwide are required to wear respiratory protective devices (RPD). R

17、PD vary considerably, from filtering devices, supplied breathable gas devices, and underwater breathing apparatus (UBA), to escape respirators used in emergency situations (self-contained self-rescuer or SCSR). Many of these devices protect against airborne contaminants without supplying air or othe

18、r breathing gas mixtures to the user. Therefore, the user might be protected from particulates or other airborne toxins but still be exposed to an ambient gas mixture that differs significantly from that which is normally found at sea level. RPD that supply breathing air to the user, such as an SCBA

19、 or UBA, can malfunction or not adequately remove carbon dioxide from the breathing space, thus exposing the user to an altered breathing gas environment. In special cases, RPD intentionally expose the wearer to breathing gas mixtures that significantly differ from the normal atmospheric gas mixture

20、 of approximately 79 % nitrogen and 21 % oxygen with additional trace gases. These special circumstances occur in aviation, commercial and military diving, and in clinical settings. Breathing gas mixtures that differ from normal atmospheric can have significant effects on most physiological systems.

21、 Many of the physiological responses to exposure to high or low levels of either oxygen or carbon dioxide can have a profound effect on the ability to work safely, to escape from a dangerous situation, and to make clear judgements about the environmental dangers. In addition, alteration of the breat

22、hing gas environment can, if severe enough, be dangerous or even fatal. Therefore, monitoring and controlling the breathing gas, and limiting user exposure to variations in the concentration or partial pressure of oxygen and carbon dioxide, is crucial to the safety and health of the worker. This Tec

23、hnical Specification discusses the gas composition of the Earths atmosphere; the basic physiology of metabolism as the origin of carbon dioxide in the body, respiratory physiology and the transport of oxygen to the cells and tissues of the body; and the subsequent transport of carbon dioxide from th

24、e tissues to the lungs for removal from the body. Following the basic physiology of respiration, this Technical Specification addresses the physiological responses to altered breathing environments (hyperoxia, hypoxia) and to the effects of excess carbon dioxide in the blood (hypercarbia). Examples

25、are given from the relevant biomedical literature. Finally, it deals with the impact of altered partial pressures/concentrations of oxygen and carbon dioxide on respirator use. The content of this Technical Specification is intended to serve as the basis for advancing research and development of RPD

26、 with the aim of minimizing the changes in the breathing environment, thus minimizing the physiological impact of RPD use on the wearer. If this can be accomplished, the health and safety of all workers required by their occupation to wear RPD will be enhanced. TECHNICAL SPECIFICATION ISO/TS 16976-3

27、2011(E) ISO 2011 All rights reserved 1Respiratory protective devices Human factors Part 3: Physiological responses and limitations of oxygen and limitations of carbon dioxide in the breathing environment 1 Scope This Technical Specification gives: a description of the composition of the Earths atmo

28、sphere; a description of the physiology of human respiration; a survey of the current biomedical literature on the effects of carbon dioxide and oxygen on human physiology; examples of environmental circumstances where the partial pressure of oxygen or carbon dioxide can vary from that found at sea

29、level. This Technical Specification identifies oxygen and carbon dioxide concentration limit values and the length of time within which they would not be expected to impose physiological distress. To adequately illustrate the effects on human physiology, this Technical Specification addresses both h

30、igh altitude exposures where low partial pressures are encountered and underwater diving, which involves conditions with high partial pressures. The use of respirators and various work rates during which RPD can be worn are also included. 2 Terms and definitions, symbols and abbreviated terms 2.1 Te

31、rms and definitions For the purposes of this document, the following terms and definitions apply. 2.1.1 alveoli s. alveolus terminal air sacs of the lungs in which respiratory gas exchange occurs between the alveolar air and the pulmonary capillary NOTE The alveoli are the anatomical and functional

32、unit of the lungs. 2.1.2 ambient temperature pressure saturated ATPS standard condition for the expression of ventilation parameters related to expired air NOTE Actual ambient temperature and atmospheric pressure; saturated water pressure. ISO/TS 16976-3:2011(E) 2 ISO 2011 All rights reserved2.1.3 b

33、ody temperature pressure saturated BTPS standard condition for the expression of ventilation parameters NOTE Body temperature (37C), atmospheric pressure 101,3 kPa (760 mmHg) and water vapour pressure (6,27 kPa) in saturated air. 2.1.4 carbaminohaemoglobin HbCO 2 haemoglobin that has bound carbon di

34、oxide at the tissue site for transport to the lungs 2.1.5 dead space anatomical conducting regions of the pulmonary airways that do not contain alveoli and, therefore, where no gas exchange occurs NOTE These areas include the nose, mouth, trachea, large bronchia, and the lower branching airways. Thi

35、s volume is typically 150 ml in a male of average size. 2.1.6 dead space physiological sum of all anatomical dead space as well as under-perfused (reduced blood flow) alveoli which are not participating in gas exchange NOTE The volume of the physiological dead space can vary with the degree of venti

36、lation. Thus, the physiological dead space is the fraction of the tidal volume that does not participate in gas exchange in the lungs. 2.1.7 dyspnoea sense of air hunger, difficult or laboured breathing, or a sense of breathlessness 2.1.8 end-tidal carbon dioxide ET CO 2volume fraction of carbon dio

37、xide in the breath at the mouth at the end of exhalation NOTE End-tidal carbon dioxide corresponds closely to alveolar carbon dioxide. 2.1.9 haemoglobin Hb specific molecules contained within all red blood cells that bind oxygen or carbon dioxide under normal physiological states and transport eithe

38、r oxygen or carbon dioxide to or from the tissues of the body 2.1.10 hypercarbia hypercapnia excess amount of carbon dioxide in the blood 2.1.11 hyperoxia volume fraction or partial pressure of oxygen in the breathing environment greater than that which is found in the Earths atmosphere at sea level

39、 which contributes to an excess of oxygen in the body NOTE This can occur when a person is under hyperbaric conditions (i.e. diving), subjected to breathing gas mixtures with an elevated oxygen fraction, or during certain medical procedures ISO/TS 16976-3:2011(E) ISO 2011 All rights reserved 32.1.1

40、2 hypoxia volume fraction or partial pressure of oxygen in the breathing environment below that which is found in the Earths atmosphere at sea level NOTE Anaemic hypoxia is due to a reduction of the oxygen carrying capacity of the blood as a result of a decrease in the total haemoglobin or an altera

41、tion in the haemoglobin constituents. 2.1.13 hypocapnia volume fraction or partial pressure of carbon dioxide in the breathing environment or in the body that is lower than that which is found in the Earths atmosphere at sea level NOTE This usually occurs under hyperventilation conditions (i.e. divi

42、ng) or in medical settings that contribute to a reduction of carbon dioxide in the body 2.1.14 inotropic affecting the force of muscle contraction NOTE A negative inotropic effect reduces and a positive inotropic effect increases the force of muscular contraction (e.g. both skeletal and heart muscle

43、). 2.1.15 medulla oblongata, pons areas of the brain where the respiratory control centre is located 2.1.16 oxyhaemoglobin HbO 2haemoglobin that has bound oxygen from the lungs for transport to the body tissues 2.1.17 partial pressure pressure exerted by each of the components of a gas mixture to fo

44、rm a total pressure EXAMPLE Air is a mixture of oxygen, nitrogen, carbon dioxide, inert gases (argon, neon), and water vapour. The volume fraction of oxygen in air is about 20,9 %. At sea level, total atmospheric pressure is 101,3 kPa (760 mmHg). Water vapour pressure is 6,26 kPa (47 mmHg) (fully sa

45、turated in the lungs at a body temperature of approximately 37 C). To find partial pressure of oxygen, subtract vapour pressure from total atmospheric pressure and then multiply the oxygen volume fraction by the dry atmospheric pressure. Thus, 101,3 6,3 = 95,1 kPa (760 mmHg 47 mmHg = 713 mmHg); 0,21

46、 95,1 kPa = 19,9 kPa (= 149 mmHg). If the ambient pressure increases (as in diving), the partial pressure of each component gas increases. Thus, at 2 atm absolute, the partial pressure of oxygen in dry gas is 101,3 2 = 202,6 kPa (760 mmHg 2 = 1 520 mmHg); 0,21 202,6 = 42,6 kPa (0,21 1520 mmHg = 319

47、mmHg) oxygen. NOTE 1 Partial pressure is dependent on the volume fraction of the component gas. NOTE 2 The partial pressure of a gas can increase or decrease while its relative volume fraction remains the same. Partial pressure drives the diffusion of gas across cell membranes and is, therefore, mor

48、e important than relative volume fraction of the gas. 2.1.18 respiratory quotient R Qratio of volume of carbon dioxide exhaled to the volume of oxygen consumed as follows 22 Q CO O VV R where ISO/TS 16976-3:2011(E) 4 ISO 2011 All rights reservedVCO 2is the volume of carbon dioxide exhaled; VO 2is th

49、e volume of oxygen consumed NOTE R Qgives an estimate of the content of substrate utilization during steady-state respiration and metabolism. At rest, R Q= 0,82 reflecting a substrate utilization of a combination of carbohydrates and fats as the primary energy source. 2.1.19 respiratory system tubular and cavernous organs (mouth, trachea, bronchi, lungs, alveoli, etc.) and structures which bring about pulmonary ventilation and gas exchange between ambient air and blood 2.1.20 standard temperat