Lung function studies before and after a work shift

Transcription

1 British J6urnal ofindustrial Mediine 1983;40: Lung funtion studies before and after a work shift R G LOVE From the Institute of Oupational Mediine, Edinburgh EH8 9SU, UK ABSTRAT The lung funtion of 23 underground oal workers and eight surfae workers at a Sottish olliery was measured immediately before and after a work shift. hanges in lung funtion were assessed in relation to the measured respirable dust exposure and the time of day in whih the shift was worked. Large, and statistially signifiant, derements of lung funtion during the shift were found in night-shift workers ompared with workers on other shifts. Measurements derived from the fored expiratory manoeuvre, partiularly FEV1, Vmax50, and Vmax25, after three vital apaity breaths of an 80% He/20% 02 mixture, showed large redutions in night-shift men, smaller redutions in afternoon-shift men, and small inreases or dereases in morning-shift underground and surfae workers. Within-shift hanges for other tests, suh as losing volume, N index, and volume of isoflow, did not differ signifiantly between shifts. No signifiant relationship was found between dust exposure and funtional hanges during a shift for any test. Lung funtion hanges in a ontrol group of 25 female workers not exposed to dust (hospital nurses) did not show the same large variations between day and night shifts. Examination of a further ontrol group of 16 offie workers did not show any differene in diurnal hanges between smokers and non-smokers. It is onluded that these oal miners, even on permanent shift patterns, had widely different hanges in their lung funtion yle depending on whih shift they were working. These hanges did not appear to be related to dust exposure or igarette smoking and were not onsistent with other biologial adaptations known to result from regular night-shift working. The results of an investigation of oal miners' in the United States indiated that derements of lung funtion over a shift, partiularly maximum expiratory flow at low lung volumes, were orrelated with the estimated average dustiness of a oal miner's job underground. It was also observed that these findings applied to miners whatever time of day (shift) they worked. (These men had been employed on a partiular shift for at least two onseutive weeks before the study.) Sine the atual dust exposures of the miners in that study' were not measured, the present study was arried out to investigate further the relationship between dust exposure measured during a work shift and hanges in lung funtion. oal miners exposed to a range of airborne dust levels and working different shifts were examined before and after a normal shift, in order that the aute effets of breathing oal-mine dust on lung funtion ould be examined. Subjets who had not been Reeived 18 Marh 1982 Aepted 18 May exposed to dust were also examined, so that the additional effets of time of day and tobao smoking on hanges in lung funtion ould also be investigated. Material and methods Thirty-two underground oal workers from a olliery in Sotland who regularly arried airborne dust sampling instruments to their plae of work for researh purposes were seleted to at as subjets.of these men, 23 (aged 23-59) ould take part in the study. Ten men worked on the morning shift (7 am pm), seven the afternoon shift (2 15 pm-9 30 pm) and six the night shift (11 pm-6 15 am). In addition eight day-shift surfae workers, who had never worked underground and were not exposed to appreiable amounts of airborne dust during their work, had their lung funtion measured before and after a normal shift. Table 1 gives the harateristis of all these men. Six men worked the morning shift onstantly and another four on this shift alternated weekly with the afternoon shift. All but one urrent afternoon-shift

2 154 worker alternated weekly with the morning shift and all night-shift men worked this shift exlusively. Two men at a time attended at a mobile laboratory at the olliery immediately before their shift, and again as soon after their shift as possible. On both oasions smokers were asked not to smoke for at least an hour before the tests. Subsequently, 25 nursing and tehnial staff (all women) volunteered to be examined at a loal hospital to investigate the possible effet of shift work on workers not oupationally exposed to a dusty environment. This group onsisted of seven nurses and five laboratory tehniians on day shift and 13 nurses on night shift. The subjets attended at a laboratory at the hospital immediately before their shift at 8 15 am or 8 15 pm and again immediately after work at pm or 7 30 am respetively. Finally, 16 male offie and laboratory workers from this institute were examined three times, at the beginning (9 am), middle (12 pm) and end (5 pm) of a normal working day. Eight were smokers (aged 23-49) and eight were non-smokers (aged 24-40). The following measurements were made at eah visit for the oal miners. Lung volumes were measured by multiple breath helium dilution from whih vital apaity (V), funtional residual apaity (FR), residual volume (RV), and total lung apaity (TL) were derived. Fored expiratory manoeuvres using air and after three V breaths of an 80% helium/20% oxygen mixture were performed, and fored vital apaity (FV), fored expiratory volume in one seond (FEV),,maximum expiratory flow at 50% and 25% of FV (Vmax50 and Vmax25) breathing air and He/O29 and volume of isoflow (V isov) were measured from the best of at least three tehnially satisfatory flow/volume urves on air and two suh urves on He/O2. The urve with the largest FV was seleted for analysis and V isov was measured by aligning the best air Table 1 Personal details ofstudy population. (Standard deviations in parentheses) and He/02 urves at RV.2 Fored expiratory time (FET) was also reorded by a timer ativated by the expiration of the first 100 ml of air and stopped one the flow had fallen below 50 ml/s. The single breath nitrogen test was also arried out at eah visit, at least three times on eah subjet. The alveolar plateau in the form of the N onentration differenebetween750and 1250ml(AI2% 7120orthe N2 index) was measured and the losing volume and losing apaity (R + RV) were also derived from this manoeuvre. Only measurements derived from the fored expiratory manoeuvres were taken for the nurses and offie workers. A brief job desription was obtained for eah miner, and his age, height, weight, smoking habits, and any appreiable ardiorespiratory abnormalities were reorded at his first visit. Table 1 gives the mean ages and anthropometri data for eah group of miners, nurses, and offie workers. MRE Type 113A gravimetri respirable dust samplers were arried and positioned near to their plae of work by the oal miners who had worked underground. The respirable dust onentrations measured gave a time weighted shift mean onentration for eah man. In pratie the miners attended the laboratory at the time they normally went to their plae of work and as a result were ready for work about half an hour later than usual and were a similar amount early when leaving work. Underground workers often did not go underground until about an hour after their normal time and sometimes ame up an hour early. In addition some men were not deployed to their normal plae of work one they had arrived underground and onsequently were often exposed to less dusty onditions than usual. STATISTIAL METHODS The hange in eah lung funtion variable from its Grouplshift No Age FEV, Predited Smoking habit Dust exposure (years) (1) % Yes No Ex (mg/mr) oal workers, underground: Morning shift ) 3-67 (0.73) (1-35) Afternoon shift ) 3-71 (0-61) (2.10) Night shift (5-6) 3-16 (0-75) (1.10) oal workers, surfae: Morning shift (6-9) 2-40 (0-94) Nurses: Day shift (12-9) 2-96 (0.55) NA Night shift (9-1) 2-55 (0-72) NA Offie/lab workers (day shift): Smokers ( ) NA Non-smokers (6-1) NA NA = Not available. Love

3 Lungfuntion studies before and after a work shift value before (x,) to its value after (x2) the shift was expressed as follows: x2 -x Ax (% differene) = x (XI + X2) The largest value was seleted from those tehnially satisfatory readings of variables derived from the fored expiratory manoeuvres, while the average of three values was used for readings derived from the single-breath nitrogen test. Paired t tests were used for analysing differenes between start and end of the shift. Results OALWORKERS Table 1 gives the mean dust onentrations for underground workers on the three shifts. Only seven men were exposed to respirable dust onentrations greater than 2 mg/m3 and 13 readings were less than I mg/m3. When the subjets were examined aording to the shift they worked, the onsiderable differenes in the q,- m Ċ, -1 a L 1 0 * degree and diretion of hange of some of the lung funtion variables were unrelated to the atual dust exposure. Table 2 and fig 1 show that indies derived Table 2 hanges in lung funtion during a working shift for underground workers on day, bak, and night shifts andfor surfae workers on day-shift Lungfuntion Underground workers Surfae workers test DS BS NS DS FEVI +1*8-3-7t -5-9tt +0 5 FV t -0-9 (max 'maxr Vmax5y (He/02) t +11*6 Vmax (He/02) t V iso*s A N2% V RV t Figures are % differenes pre- to postshift. Post- preshift value Mean of pre- and postshift values Differenes between shifts were statistially signifiant (p < or 0-05) in the following ways: tsig diff from DS; tsig diff from surfae; diff from DS, BS, and surfae; Morning E Afternoon a N<ht 0 Surfae L -4_.0- I * 11sig Isig diff from all underground shifts. 1 IF I 0 ' * NS1 Jz$3 NS ~o * I FEV1 FV Vmax50 Vmox25 Vmax5 Vrnax25 v iso V N 2f. V RV He/02 He /02 Fig 1 Perentage hanges in lung funtion ofoal workers on morning, afternoon, and night shifts (underground workers) and morning * shift only (surfae workers). Signifiant differenes between shifts. NS = Not signifiant. NS 155

4 156 from the fored expiratory manoeuvre, notably hanges of FEVI and Vmax on air and He/O2, showed large and highly signifiant differenes between the three underground shift groups and between some of these groups and the surfae workers. FEV1 of night-shift workers, for example, fell 5-9%, whih was signifiantly different (p < 0-02) from that of surfae workers, whose FEV1 inreased by 0.5%. A FEV, of morning-shift underground workers (+ 1.8%) was also very different froma FEVI of other underground workers (p < 0.001). Vmax,, (He/O2) inreased by 20-6% for surfae workers but fell by 0-7%, 22-4%, and 3711% for morning, afternoon, and night-shift underground workers respetively. Most of these differenes were statistially signifiant. Volume of isoflow and measurements derived from the single breath nitrogen test-that is, N2 index and losing volume-showed no relationship with the shift worked but residual volume of night-shift workers inreased signifiantly ompared with the surfae shift (table 2). There appeared, however, to be little or no disernible relationship between hanges in lung funtion and dust exposure during a shift. The highest orrelation observed between the hange in p p<0-02 L a. z ~~~~*_ p-v-vl r<a.a Love any lung funtion variable and dust exposure for all underground workers ombined was with Vmax25 (r = 0-29, t = 1.30), although even this was well below the onventional level of statistial signifiane. NURSES The hanges in lung funtion during a shift were generally small on average (table 3 and fig 2). FEVI fell slightly in daytime workers and Vmax25 and FEV (He/02) both fell during their shift for night workers. Although all but one of the tests had hanged more adversely for night than for day staff, no test was Table 3 hanges in lung funtion during a working shift forfemale hospital nursing and tehnial staffon day and night shifts Lung funtion Day shift Night shift test Air He/O2 Air He/O2 FEVI -1*2* *7-4-6* FV Vmax Vmax * FET *hange is signifiantly different from zero p <0-05. No differene between day and night shifts was statistially signifiant for any test. p<o05 ~N~ht shift Air He/02 Air He/l2 Air He /02 Air HelO2 Air He /02 FEV1 VF ax50 Fmax25FET Fig 2 Perentage hanges in lungfuntion for nurses on day and night shifts-fored expiratory manoeuvres breathing air and 80% He/20% * 02. hange is signifiantly different from zero. shift

5 Lung funtion studies before and after a work shift signifiantly different between these two groups. In general the hanges for eah variable were in the same diretion for both groups-that is, FEV,, FV, and Vmax25 delined, while Vmax 5 inreased slightly, exept on air for day workers. LABORATORY/OFFIE WORKERS Fored expirations were arried out as before at eah visit, and on average lung funtion improved for all tests between 9 am and 12 noon (fig 3). This improvement was always greater than the differene between the values measured at 9 am and 5 pm. At 5 pm Vmax., (He/02) had shown a small derease ompared with the 9 am value in both smokers and non-smokers, but Vmax2, (He/O ) dereased only in smokers. All other tests were stilt higher at 5 pm. The size of these hanges did not differ signifiantly between smokers and non-smokers in this study, although the former had slightly greater inreases in FEV1, FV, Vmax.,, and Vmax25 between 9 am and 12 noon. The overall hanges between 9 am and 5 pm were no greater than 3% but some quite large individual differenes ourredfor instane, a 10% inrease in FEVI in one subjet. Disussion The results of this study indiate that onsiderable differenes between workers may exist in the hanges that our in lung funtion during a working shift, depending on the time of day and possibly the type of work undertaken. Mine workers on night shift have u -0 P ED M been shown to have substantially greater redutions in lung funtion than workers on earlier shifts, hanges that are not aounted for by higher dust exposure. Workers unexposed to airborne dust, suh as hospital nurses, do not appear to exhibit the same differenes between night- and day-time shifts. These large inter-shift differenes found in oal miners, whih were muh greater for maximum expiratory air flow in the latter half of a fored expiratory manoeuvre, appear to be real and probably represent true iradian variations. Previous studies of industrial workers on day shifts suggest that lung funtion (FEV, or FV) exhibits a 3-4% rise during the morning hours after waking.4 Most of this hange has been shown to our in the first two hours or so,5 whih was onfirmed by our results on offie workers. Our finding of a differene not only in degree but also of diretion between miners on different shifts onflits with the laim that workers on different shifts an be grouped together if they have worked a partiular shift onstantly for at least two weeks.' In the present study there is a residual shift effet to the extent that miners on afternoon and night shifts experiene an inreasingly greater loss of lung funtion during their working hours. Most of the dayshift men and all the night-shift men had been on these shifts for at least several weeks. They would therefore be expeted to have adapted in suh a way that the iradian rhythms of the night workers would have been similar to those of day workers.6 The mineworkers on afternoon shift, Non- smolers however, Smokers [] FEV1 FV Vmax50 Vrmax25 Vmax5O ;/max25 (He/02) (He/02) Fig 3 Perentage hanges in lung funtion (fored expiratory manoeuvres breathing air and 80% He/20%02) of laboratory and offie workers on day shift: smokers and non-smokers. 157

6 158 while mostly on the first day of this shift (whih they alternated weekly with the morning shift), exhibited hanges intermediate to those on the other two shifts. In other words, their lung funtion showed a moderate derease during the afternoon and evening hours, whih is expeted for workers on a normal night/day sleep/work pattern.3 The night workers seemed to be behaving as if they had not adapted at all to their shift pattern. They exhibited the harateristis of men examined at the times of day of men on a normal diurnal yle-that is, an improvement during the morning, a slight fall in the afternoon, and a larger fall at night. The reasons for this unexpeted finding are not obvious. Although the night workers are onsiderably older than the morning and afternoon workers, by 13 and 16 years respetively, the surfae workers (on day shift) were even older than the night workers, yet their funtional hanges were similar to those of the underground workers on the morning shift. It is not known when during the day the night-shift workers slept, but almost ertainly it would have been immediately after work, aording to reognised habits of other permanent night workers.7 In that ase these men would be on the desending part of their urve of biologial rhythm, whih in regular day workers begins during the evening before retiring. The large and onsistent falls of FEV1, whih are muh greater in magnitude than the inreases in morning workers, annot, however, be related to the lak of adaptation to a rotating shift pattern, sine all these men were permanent night-workers. Although four men were examined on Monday night (their first night at work after the weekend), their lung funtion hanges were similar to the men examined later in the week. Therefore, one annot assume that workers, who may have been on a shift for several weeks, are biologially fully adapted to the new yle. The lak of any relationship between lung funtion hanges and respirable dust exposure onfirms the findings of previous workers (N L Lapp et al, personal ommuniation, 1978). The average exposure of the underground workers in the present study was apparently similar to that of the miners studies by Lapp and his olleagues-that is, about 1 6 mg/m3 averaged over the shift. There was, however, a slight but insignifiant trend for our miners with dust exposure >3 mg/m3 to have a greater redution of Vmax23 (-13%) when ompared with miners exposed to <3 mg/m3 (-6-5%) and surfae workers not exposed to dust ( +9%), who all worked the day shift. Surprisingly, a learer distintion between day and night staff was not shown for the ontrol group of hospital workers. Both groups tended to exhibit a deline in funtion during their shift whih, although greater in night staff, was not signifiantly different Love from the hanges found in day workers. Nevertheless, some of these hanges during the shift were signifiantly different from zero (table 3). The night staff might have been expeted to have shown a deline beause they only worked for one to three nights eah week and may not have been fully adapted. On the other hand, this group worked a longer shift (8 30 pm to 7 30 am) than the day staff (8 30 am to 4 30 pm) and the times of measurement before and after the shift ould have been on different parts of their urve of iradian rhythm. This lak of differene did not seem to be due to differenes in smoking habits, sine there were similar numbers of smokers and non-smokers in eah group. No differenes in lung funtion hanges were found between non-smokers and smokers in offie and laboratory workers examined before and after a day shift (table 4), onfirming the findings of a reent study of a group of offie workers.8 It is therefore not lear why night-shift miners should have exhibited suh large derements of lung funtion during their shift, partiularly for Vmax25 when breathing air or He/02. These results suggest, however, that are should be taken in interpreting data from longitudinal surveys of lung funtion in industrial or other working populations. The large shift or diurnal effets, in addition to the larger intraindividual variation of Vmax259 may make interpretation of hanges related to airborne pollutants more diffiult. Thanks are due to T D Wilson and P A Huthison for arrying out the lung funtion tests, W Fairman and R Watson for organising the olletion of dust sampling data, the management of Lady Vitoria olliery, and senior nursing offier Makenzie of ity Hospital, Edinburgh, for their o-operation, and, finally, to all the subjets who partiipated in this study. Table 4 hanges in lungfuntion ofoffiellaboratory workers during a normal working day (a) % differenes between 9 am and 12 noon, (b) % differenes between 9 am and 5 pm Smokers Non-smokers Total n = 8 n = 8 n = 16 A9-12 A9-5 A9-12 A9-5 A9-12 A9-5 FEVI FV Vmax Vmax Vmax50 (He/O) 'Vmax2 (He/02) No differene between smokers and non-smokers was statistially signifiant for any test.

7 Lung funtion studies before and after a work shift Referenes Lapp NL, Hankinson JL, Burgess DB, O'Brien R. hanges in ventilatory funtion in oal miners after a work shift. Arh Environ Health 1972;24: Hutheon M, Griffin P, Levison H, Zamel N. Volume of isoflow: a new test in detetion of mild abnormalities of lung mehanis. Am Rev Respir Dis 1974;110: Guberan E, Williams MK, Walford J, Smith MM. iradian variation of FEV in shift workers. Br JInd Med 1969;26: MKerrow B, MDermott M, Gilson J, Shilling RSF. Res.- piratory funtion during the day in otton workers. Br J Ind Med 1958;15: Lewinsohn H, apel L, Smart J. hanges in fored expiratory volumes throughout the day. Br Med J 1960;i: Winget M, Hughes L, Ladou J. Physiologial effets of rotational work shifting. A review. JOM 1978;20: Lortie M, Foret J, Teiger, Laville A. iradian rhythms and behaviour of permanent nightworkers. IntArh Oup Environ Health 1979;44: Hankinson JL, Boehleke B. Variability of spirometri pulmonary funtion studies. Am Rev Respir Dis 1981;123,suppl:148. Love RG, Attfield MD, Isles KD. Reproduibility of pulmonary funtion tests under laboratory and field onditions. Br J Ind Med 1980;37:63-9. Br J Ind Med: first published as /oem on 1 May Downloaded from on 7 November 2018 by guest. Proteted by opyright.