Tobacco Documents Online

172 ~ SMOKING BIiHAVIOtUtt, Quantitative measurements of the smoking profile which can be made are the nurnber, of cigarettes smoked„cigarctrte butt length, puff parameters (puff volume, puff duration, number of puffs and inter-puff interval) and'the inhalation: pattern. ' 'IVfutr is the smoke uptake and'retention?" Here we are trying,to quantify the smoke uptake and dose absorbed as a result of the smoking profnle. Most approaches to this question attempt to estimate the dose of'tobaccq smoke from an analiysis of certain smoke components or their markers~- commonly carbon monoxide or nicotine. It should be noted however that carbon monoxide is a~measure of t'h,e gas/vapour phase of the smoke whiQst' nicotine~ is a reflection of'particulate matter and it' is possible that these two phases of the tobacco smoke bchave differently in terms of their pulmonary d'istribution, and absorption. Carbon monoKide may be measured in the blood or in exhaled air whilst nicotine is usually measured in the bloodiorin, theurine: A somewhat different ~ approach is the estima2ion of nicotine intake from that retained in the cigarette butt. Measurement of'puff'parameters Method Puff parameters can be obtained from measurements of the pressure drop across aismall resistance inserted between the cigarette andithe smoker. In this situation, when there is air flow during puffing, the pressure drop created across the resistance will!be related to the gas flow. The relationship will depend upo'nwhether thee airflow is turbulent„whenithe flow rate will be proportional'to the square~root of the pressure drop; or lantinar, when the flow will be directly proportional to the pressure drop: In either case puflvolume canbed'erived'by integratianof the flow signal against time and puff and interpuff intervals can be measured directly. Specialised cigar.tte1olders have been designed incorporating devices to produce a pressure dbop with either turbulent flow (orifice plate) or, as used in the present' experiments, laminar tlbw (filter insert). Both types of device have their advantages and disadvantages but' it is not appropriate to discuss these in detail in this paper. Tt is necessary, however, to outline some of the problems associat:edi with the filter insert type of holder as emplbyed in the studies tbibe described. The holder is shown in, Fig. 14.1. It contains a replacea'ble 6mm cellulose acetate filter across which the pressure drop can be measured using a differential! pressure guage: The assumption is'that t'his pressure drop is linearly related to the flo!w of gas through it, i.e. that the flbw is laminar and Q=Kp -(1!) where Q is the Plow rate; p is the pressure dbop and K is a constant: Fig. 14.2 shows the pressure drop.versus flow rclationship of the holder for air over thee range of flows found during normal smoking. It can be seen that the relationship is curvilinear indicating that t'~hebasic assumptio'n!regarding flow derivation is not currect'. Nevertheless, the degree of curvature is relatively slight and the overall error introduced in computing puff volume from the flbw signallis accordingly small. This reWionsiiip between pressure and the flow has bcenobtiained by drawing air through the lilter holder at room temperatures. The exact relationship between 1005052990

---

. 1PdPdA1.A'T10TA'AMD ABSORPTION OF TOBACCO SMOKE 179 The relationship between puff'and inhalation profiles Derivationof'the puff flow profile and the inhala!tion profile have been described separately but useful infiormation maybe gained by combining,these techniques. In Fig. 14.7 are shown two examples. 5ecsI'I'11 I I I I I I I II'I ( I I I I I I II I 11 I I I I I I Il I I l l ll' I'I'UI I I I I I I Il ll l I I I I I I 1 I I q I I I 1 I I I I pneumogram Trace. Puff Profile ~ Fig. 14.7 ' The pneumogram, tracing andi the puff flow profile from two smokers during normal smoking to illustrate: i)~the relationship of the puff to the inhalation and ii) the:pattern of chesYwatl monemenidhrring,puffing and preceeding the inhalation of smoke. The time relationships of puffing from the cigarette and "uiltalation of't'he smoke can be studied1whenit is observed that'the puff is taken into the mouth from thrcigarettee before being inhaled into the lungs. This has important implications in terms of dose exposure for it means that the whole of'the smoke bolus is potentially available to be taken deeply into the lungs at, the beginning of inhalation rather than being distributed throughout the total inhaled volume of air. Recording both puff and inhalationprofiles.it is also possible to note:any gross movements of the chest walt'durirtg puffing. In the majority of subjects studied Q, the patternishowrrinthe first example of Fig. 114.7 is observed where virtuallyno, 01 movement of the chest wall takes~place. However, in a few subjects, most' notably UT smokers of high tar, prodi?cts, there is an apparent active exhalation following the: Q puff prior to the subsequent inhalation. This is sh6wn: in example 2' Fig. 14.7. ~ The implication of this pattern of'smoking,is that the bolus of tobacco smoke has ~ been blown from the mouth andi very litt'lt, if a!ny„is available at the subsequent inhalation (presumably this is also the pattern in cigar smokers)i ~ Measurement of carbon, monoxide Method Tobaccoismoke conta!ins carbon monoxide and'studies have shown that the venous carboxyhaemoglobin saturation (IHbCO`9o) of `inhaling'.' cigarette smokers is signif- icantlly higher than that of non-smokers. Measurement of venous carboxyhacmoglubin, with the necessity of obtaining,a blood sample by Einger prick,or venepuncture, was not considered satisfactoryfor, (large scale) studies ina'normai"populationn lt was therefore decided to measure carbon monoxide in mixed eapired'anr and tio deriive the partial pressure of carbon, monoxide in.alveolar air using the Bohr cquatian.