Document 0Ow6DkaJd175zkdozr32wZ8m

146 FRANK A. PATTY and toluidine, which form methemoglobin; nitrobenzene, which has the nitrite effect, forms methemoglobin, lowers blood pressure, disturbs and finally halts breathing; and hydrogen sulfide, which causes respiratory paralysis. (See also lung irritants.) S. Anesthetics and Narcotics This group exerts its principal action as simple anesthesia without serious systemic effects, and the members have a depressant action on the central nervous system governed by their partial pressure in the blood supply to the brain. The following examples are arranged in the order of their decreasing anesthetic action compared with other actions: (a) acetylene hydrocarbons (acetylene, allylene, crotonylene); (b) olefin hydrocarbons (ethylene to heptylene); (c) ethyl ether and isopropyl ether; (d) paraffin hydrocarbons (propane to decane); (e) aliphatic ketones (acetone to octanone); (/) aliphatic alcohols (ethyl, propyl, butyl, and amyl); (0) esters (not particularly anesthetic, but placed here for want of a better classification)--they hydrolyze in the body to organic acids and alcohols. 4- Systemic Poisons () Materials that cause organic injury to one or more of the visceral or gans: the majority of the halogenated hydrocarbons. () Materials damaging the hematopoietic system;- benzene, phenols, and, tosom'e`'d`eiree7'tolueircrxylene7'and-naphtha'lener (c) Nerve poisons: carbon disulfide, methyl alcohol, thiophene. (d) Toxic metals: lead, mercury, cadmium, antimony, manganese, beryllium, etc. (e) Tojhc nonmetal inorganics: compounds of arsenic, phosphorus, selenium, and sulfur; fluorides. 5. Particulate Matter Other Than Systemic Poisons () Fibrosis-producing dusts: silica, asbestos. () Inert dusts: carborundum, carbon, emery. (c) Dusts causing allergic-reactions:--pollen,-wood, resins, and organic-dusts. ^W/****1* '"Aft .nattiriiqgc* v.** \ (d) "iir'itantsi-acids/alkalies; fluoride'sjichr'onihtes';-' - ; (e) Bacteria and other-microorganisms. ....*IL ReSpiratlon A. MECHANICS OF RESPIRATION During inspiration', air forced by atmospheric pressure enters the nasal \ openings, passes through the pharynx, larynx, trachea, bronchi and bronchioles,^ m. ENTRY AND ACTION OF TOXIC MATERIALS 147 l^r^rllrbugh the terminal bronchioles, the respiratory bronchioles and alveolar ducts, Sjj&SiiftScth'e air sacs or alveoli, filling the void created by involuntary muscular ****-?ffiSawlfflifeof the thoracic cavity. Expiration may be either by muscular effort or JiV\-qIa|tjc contraction of lung tissue, but in quiet breathing contraction is thought ^^^t*^je/entir.ely passive. The normal function of respiration is to supply atmospheric *TBH&^5KP^ugh the alveolar walls to the blood for distribution to the tissues and **-* V- :v$ carbon dioxide resulting from oxidation within the cells. The oxygen ^^imJ^carbpn dioxide exchange in the tissues is sometimes referred to as tissue or ^Ai^^Sgespiration, as distinguished from the aeration of the lungs or external _^^^f^r LUNG STRUCTURE, VITAL CAPACITY, AND THE DEAD SPACE H|3^prhc. tracheobronchial tree as described by Miller2 is supported by cartilage, gpea being a series of open cartilaginous rings or crescents connected on ^\^-?tcrior s'^e ^ bundles of muscle. The rings are joined to each other by 81^^lenie layer of connective tissue. The result is a rather rigid ribbed tube capable fen^^^^^ustment in diameter. This tube divides into the right and left main - l^%f^^^grtending downward at approximately 20 degrees for the right, and 40 m or, the left branch. The bronchi are further divided and subdivided into gggmd smaller bronchial passages. There is a muscular network essentially e ,to these passages, and as the passages decrease in diameter the car|s|rings become less complete, finally losing their cresent shape to be- m. Wflnaus gply small plates of cartilage. As the cartilage decreases there is an inShe "proportion df~muscular--tissue. Cartilaginous support finally dis||)'ward the outer end of the bronchioles, where the- diameter is about "liese terminal bronchioles connect with respiratory bronchioles which a alveolar ducts, terminating in the alveoli,, These bronchioles range 0.2 mm. in length and are about 0.2 to 0.4 mm. in diameter. J|||aally the lungs fill about 80 per cent of thp. total chest cavity. An can inhale about 3l/a liters of air by forced effort after an ordinary |||jjLikewiae) he can forcibly,;-.exhale about jJ*, liter after an ordinary "Oh;- The sum of these, about 4x/ liters, is called the vital capacity. There 1 about 1 to lVa liters residual air which cannot be expelled by *)ut r?18*118 m lungs toaaerate .the.fblood during ,exhalation, 'jgsissa',total volume'in excess of"5V2 per cent ghormal breathing. The approximately 500 ml. of air inhaled and ifeng normal respiration is called tidal air, and of this. 500 ml. about 150 eguirgd to fill the tracheobronchial tree hr anatomical dead space---that We-Tespiratory-tract consisting of thick-walled passages -through which hange of gases between blood and air can occur. During an ordinary 500 ^hen, 150 ml. practically unaltered atmospheric.air fills the dead v'ce ^ m^' en*'ers alveoli and respiratory exchange area of the lungs. S.Mi Her, The Lung. Thomas, Springfield, 111., 1937. \_