Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Subscribe Contacts Login 
  • Users Online:3030
  • Home
  • Print this page
  • Email this page


 
 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 17  |  Issue : 1  |  Page : 47-53

Work-Related respiratory symptoms and cardiopulmonary function impairment of factory workers in a cement company in South-West Nigeria


Department of Physiotherapy, University of Lagos, Lagos, Nigeria

Date of Web Publication2-Jul-2018

Correspondence Address:
Happiness Anulika Aweto
Department of Physiotherapy, Faculty of Clinical Sciences, College of Medicine, University of Lagos, PMB 12003, Idi-Araba, Lagos
Nigeria
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ajmhs.ajmhs_41_18

Rights and Permissions
  Abstract 


Background: Cement factory workers are exposed to dangerous cement dust while at workplace especially in the developing countries where little or no safety standards are followed. This study investigated the work-related respiratory symptoms and cardiopulmonary functions' impairment in cement factory workers in South-West, Nigeria. Materials and Methods: Seventy cement exposed workers and 70 age-matched unexposed individuals participated in this cross-sectional study. A self-administered questionnaire was used to assess their sociodemographic characteristics, clinical details, and respiratory symptoms. Selected cardiopulmonary parameters of participants were measured. Data were analyzed using the Statistical Package for Social Sciences version 20.0. Independent t-test was used to compare the selected cardiopulmonary parameters of the two groups. Results: The mean age of cement-exposed group was 31.57 ± 8.32 years, and the unexposed group was 31.50 ± 8.57 years. The prevalence of respiratory symptoms among the cement-exposed group were as follows: 71.4% for cough, 45.7% for phlegm, 67.1% for wheeze, 38.6% for breathlessness, and 48.6% for chest tightness while those for the unexposed group were as follows: 50% for cough, 15.7% for phlegm, 5.7% for wheeze, 2.9% for breathlessness, and 7.1% for chest tightness. There were significant differences between the mean values of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1)/FVC ratio, peak expiratory flow rate, systolic blood pressure, and diastolic blood pressure (P < 0.05) of the cement-exposed group and those of the unexposed group. Conclusion: Respiratory symptoms were higher among cement factory workers than the age-matched unexposed individuals. FVC, FEV1, FEV1/FVC ratio, and peak expiratory flow rate were reduced while blood pressure was increased in cement factory workers.

Keywords: Cardiopulmonary functions, cement factory workers, respiratory symptoms, work-related


How to cite this article:
Aweto HA, Tella BA, Lateef AI. Work-Related respiratory symptoms and cardiopulmonary function impairment of factory workers in a cement company in South-West Nigeria. Afr J Med Health Sci 2018;17:47-53

How to cite this URL:
Aweto HA, Tella BA, Lateef AI. Work-Related respiratory symptoms and cardiopulmonary function impairment of factory workers in a cement company in South-West Nigeria. Afr J Med Health Sci [serial online] 2018 [cited 2018 Dec 17];17:47-53. Available from: http://www.ajmhs.org/text.asp?2018/17/1/47/235737




  Introduction Top


Work-related disorders are the major cause of complaints and disability in the working population.[1] Respiratory conditions impose burden on the society and are among the leading causes of death.[2] Multiple determinants serve to increase the burden of chronic respiratory disease some of which include occupational exposures, tobacco smoke, and lung infection.[2] The worldwide communities, especially the people in developing countries, are facing increasing risk of developing respiratory diseases due to the production of smoke and dust in different occupational and industrial sectors.[3] Environmental- and work-related respiratory diseases account for a significant portion of preventable illnesses and they are the leading work-related illnesses in the United States based on the frequency, severity, and preventability of diseases.[4] Exposure to various dusts, chemicals, vapor, and fumes in the workplace is a contributory factor to the development of chronic obstructive pulmonary disease (COPD) of which 19.2% of COPD cases in the USA are attributable to work exposure.[5] Exposure to quarry dust has a detrimental effect on lung function, as shown in prerevolution Libyan quarry workers.[6]

Cement is manufactured through a series of processes that include mining, crushing, and grinding of raw materials, blending, and kiln burning to form clinker, cement milling and packaging. Dust emitted during these processes, exposes workers to the hazard of work-related respiratory diseases.[7] Several studies have been done to investigate the prevalence of work-related respiratory problems associated with exposure to dust in cement factories among workers and have yielded different results.[8],[9],[10],[11] Most of the studies reported a high prevalence of respiratory symptoms and signs such as coughing, sputum, wheezing, and dyspnea as well as alteration of the pulmonary indices of cement workers.[8],[9],[12],[13],[14] However, few researchers have reported no significant difference in most respiratory symptoms between exposed and unexposed workers.[10],[11],[15] Previous studies have also reported reduction in lung function in workers exposed to high concentrations of asbestos dust.[16],[17],[18],[19],[20] There is higher prevalence of work-related respiratory problems in developing countries than in developed countries mainly because workers work without proper personal protective equipment or ventilation.[12],[21]

In Nigeria, various studies have shown the role of work-related exposure to environmental pollutants (wood and stone dust) in the incidence of respiratory diseases and symptoms such as upper respiratory tract infection, breathlessness, chronic obstructive airway disease, and asthma.[22],[23],[24],[25],[26],[27],[28] This high prevalence of work-related respiratory problems in Nigeria may be due to little or no implementation of occupational health and safety standards at workplace. This study investigated the work-related respiratory symptoms and cardiopulmonary functions deficits of factory workers in a cement factory in South-West, Nigeria.


  Materials and Methods Top


Subject selection

A total of 140 participants whose ages ranged from 18 to 60 years were recruited for this cross-sectional analytical survey. The sample size calculation was done using the formula:[29]



After calculation, the minimum sample size arrived it was 101.2. Seventy of them (58 males and 12 females) were cement workers (cement-exposed group) who were consecutively recruited from Lafarge cement factory in Ewekoro, Ogun state, Nigeria while the remaining 70 (37 males and 33 females) were civil servants (control group) who were purposively recruited from Federal Medical Centre, Idi-Aba, Ogun state. The two groups were similarly matched in age. Included into the study were individuals who had worked for at least 1 year in either of the two establishments. Individuals that were excluded from the study were those who have had recent major surgeries and those who declined participation. Ethical approval was obtained from the Health Research and Ethics Committee of Lagos University Teaching Hospital, Idi-Araba, Lagos State, Nigeria (REF NO: ADM/DCST/HREC/APP/230). Approvals were also obtained from the cement factory and the management of Federal Medical Centre, Idi-Aba. Written informed consent was obtained from the participants.

Procedure for data collection

After appropriate approvals were obtained and before the commencement of the study, a preliminary lecture was given to the prospective participants on the aims and procedure for the study. Height and weight of each participant were measured with height meter and weighing scale, respectively. Body mass index was calculated using the formula; body mass index (BMI) = weight (kg) divided by height 2 (m 2). Pulmonary function parameters forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and peak expiratory flow rate (PEFR) were assessed in sitting position using a portable spirometer (SP10 CONTEC: Hamburg, Germany) at a fixed time of the day (8 a. m.) to minimize the diurnal variation.[30] The participants in sitting position were asked to take the deepest breath they could and then exhale into the sensor as hard as possible, for as long as possible. A nose clip was used just before each participant exhaled into the mouthpiece. That guaranteed that breath flowed only through the mouth. Each participant performed this procedure three times and the mean value taken and recorded. It was necessary to coach the participants to achieve their maximal expiratory efforts before taking the actual measurements because FEV1 is highly dependent on the amount of force used by the participant in early expiration. Percentage ratio of the two volumes (FEV1/FVC) was calculated for each participant. Safety measures were adapted using a new disposable mouthpiece for each participant, cleaning the surface of the spirometer with a towel soaked in a disinfectant solution after use by each participant and allowing a delay of at least 10 min before the next participants took his/her measurement. Forced vital capacity is the largest volume of gas that can be forcefully exhaled from the lungs after a maximal inspiratory effort. FEV1 is the volume gas expired in the 1st s of maximal expiration after a maximal inspiration. PEFR is the maximal expiratory flow rate achieved, and this occurs very early in the forced expiratory maneuver.

The blood pressure of each of the participants was measured with mercury sphygmomanometer and stethoscope in sitting position. These measurements were taken two times and the mean values calculated and recorded.

The questionnaire was self-administered after the cardiopulmonary function tests were done.

Questionnaire design and administration

The British Medical Research Council questionnaire [31] – a standardized questionnaire on respiratory symptoms was adapted for this study. It has five sections (Sections A-E). Section A (7 Questions): collected information on the demographic/physical characteristics of the participants. These were age, gender, department/unit, duration of present employment, weight, height, systolic and diastolic blood pressure (DBP). Section B (13 Questions): collected information on past medical history. Section C (26 Questions): collected information on the occurrence of respiratory symptoms. Section D (8 Questions): collected information on participants' smoking habit and Section E (3 Questions): collected information on the participants' use of respiratory protective equipment.

The participants were assured that their responses would be kept confidential before the copies of the questionnaire were distributed to them by the researchers. The completed questionnaires were also immediately collected by the researchers.

Data analysis

Data were analyzed using the Statistical Package for Social Sciences version 20. Descriptive statistics of mean and standard deviation were used to summarize data. Inferential statistics of independent t-test was used to compare data between the two groups. Statistically significant level was set at P < 0.05.


  Results Top


The mean ages of the cement-exposed and cement-unexposed (control) groups were 31.57 ± 8.32 years and 31.50 ± 8.57 years, respectively. The mean years of work experience for the cement-exposed and unexposed groups were 7.10 ± 5.38 years and 6.41 ± 5.02 years, respectively. The mean BMI of the cement-exposed and the control groups were 24.65 ± 2.9 kg/m 2 and 24.24 ± 4.26 kg/m 2, respectively [Table 1].
Table 1: Sociodemographic and physical characteristics of participants

Click here to view


Sixteen (22.9%) and one (1.4%) of the cement-exposed group reported seasonal allergies and heart problem respectively as their past cardiopulmonary conditions while only one (1.4%) and none of the cement-unexposed group reported seasonal allergies and heart problem respectively as their past cardiopulmonary conditions [Table 2].
Table 2: History of cardiopulmonary conditions in participants

Click here to view


The prevalence of respiratory symptoms among the cement-exposed group was as follows: 67.1% for wheeze, 38.6% for breathlessness, and 48.6% for chest tightness while those for the unexposed group were as follows: 5.7% for wheeze, 2.9% for breathlessness, and 7.1% for chest tightness [Table 3].
Table 3: Prevalence of respiratory symptoms in the participants

Click here to view


[Table 4] shows the severity of the respiratory symptoms in the participants. Forty-three (61.4%) of the cement-exposed and 13 (18.6%) of the cement-unexposed participants reported that they usually become short of breath when hurrying on level ground. Thirty-two (45.7%) of the cement-exposed and 9 (12.9%) of the cement-unexposed participants reported that they wheeze when they run/climb stairs fast.
Table 4: Severity of the respiratory symptoms in participants

Click here to view


[Table 5] shows the history of respiratory symptoms in the past 3 years and the use of appropriate protective respiratory gadget (PRG) by participants. Fourteen (14%) of the cement-exposed group and only one (1.4%) of the control group reported that in the past 3 years, they had periods of increased cough and phlegm lasting for 3 weeks or more. Forty-two (60%) of the cement-exposed group and 3 (4.3%) of the cement-unexposed group wear PRGs at work.
Table 5: History of respiratory symptoms in the past 3 years and use of appropriate protective respiratory gadget

Click here to view


Comparison the mean values of the cardiopulmonary parameters of the cement-exposed group with those of the unexposed group showed significant differences in FVC (P = 0.001), FEV1(P = 0.001), FEV1/FVC ratio (P = 0.012), PEFR (P = 0.003), systolic blood pressure (SBP) (P = 0.0001), and DBP (P = 0.0001) [Table 6].
Table 6: Comparison of the cardiopulmonary parameters of participants

Click here to view



  Discussion Top


The aim of this study was to investigate the work-related respiratory symptoms and cardiopulmonary function impairment of factory workers in a cement company in South-West, Nigeria, and compare them with those of the aged-matched cement-unexposed apparently healthy individuals. The point to 3 years prevalence and severity of respiratory symptoms among the cement-exposed group were much higher than the unexposed group. Unfortunately, just 60% of the cement-exposed group wore PRGs at work, and only 50% of them had their PRGs test fitted for them. There were significant differences between the mean values of selected cardiopulmonary parameters (FVC, FEV1, FEV1/FVC ratio, PEFR, SBP, and DBP) of the cement-exposed group and the cement-unexposed group. While FVC, FEV1, FEV1/FVC ratio, and PEFR were significantly reduced, SBP and DBP were significantly increased in the cement-exposed group.

The finding that the prevalence and severity of respiratory symptoms among the cement-exposed group were much higher than the unexposed group could be attributed to cement dust exposure at the workplace as 40% of the cement-exposed group work without wearing PRGs, and some of them that wore the PRGs might have been using wrongly fitted sizes. This could be asserted because the demographic and physical characteristics of the participants of both groups were similar. The production of dust and smoke in various occupational and industrial sectors has been implicated in increasing the risk of development of respiratory diseases especially in developing countries where workers in these sectors are not adequately protected.[32] There is higher prevalence of work-related respiratory problems in developing countries than in developed countries mainly because workers work without proper personal protective equipment or ventilation.[12],[21] This finding corroborates previous studies.[8],[9],[12],[13],[14] They reported high prevalence of respiratory symptoms and signs such as coughing, sputum, wheezing, dyspnea, and alteration of the pulmonary indices of cement workers. However, few others reported that there was no significant difference in most respiratory symptoms between exposed and unexposed workers.[10],[11],[15]

The finding that FVC, FEV1, FEV1/FVC ratio, and PEFR were significantly reduced in the cement-exposed group compared to the unexposed group implies that the pulmonary capacities and functions of the cement factory workers were more compromised than that of the unexposed workers. The higher rates of wheeze (67.1%), chest tightness (48.6%), and breathlessness (38.6%) reported by the cement exposed workers buttress the decreased lung capacities and functions of these cement factory workers. Neghab and Choobineh [8] observed that the PEFR of cement exposed laborers in Iran was 19% lower than normal. The prevalence rates of cough, wheezing, phlegm, and breathlessness among these laborers were 31.8%, 28.4%, 26.1%, 17.0%, and 15.9%, respectively. There was no significant difference in FVC and FEV1 of the two groups. A number of studies have found that there are decreased lung functions of cement workers and other occupations with heavy dust exposure.[6],[33],[34] In a cross-sectional study, Mwaiselage et al.[14] found an annual decline of 49.1ml in FEV1 and of 23.1ml in FVC for an average worker exposed to total cumulative dust levels of 28.9 mg/year. Among none smoking healthy adults, the expected age-related rate of decline in FEV1 is 20–30 ml/year.[35]

The SBP and DBP were significantly increased in the cement-exposed group compared to the cement unexposed group. This could also be due to high exposure to cement dust. This means that exposure to cement dust does not only affect the respiratory system but also the cardiovascular system.


  Conclusion/Recommendation Top


Respiratory symptoms were higher among cement factory workers than the age-matched unexposed individuals. Forced vital capacity, FEV1, FEV1/FVC ratio, and PEFR were significantly reduced while blood pressure was increased in cement factory workers.

Based on the findings of the study, the following recommendations are suggested.

The full cardiopulmonary medical examination should be carried out on individuals who are to be offered employment in cement factories to identify those whose cardiopulmonary systems are already compromised so that they would be advised to seek other types of employments.

The employers of labor in cement factories should put in place accepted engineering control measures such an enclosure or confinement of the cement operation in order to localize cement dust from getting into the general ventilation.[36]

The employers should provide adequate PRGs and respirators which are applicable and suitable for the purpose intended for employees of cement factories to protect their health.[36]

The employers should be responsible for the establishment and maintenance of a written respiratory protection program with required worksite-specific procedures and elements for required respirator use which must be administered by a suitably trained program administrator.[36]

The employers should provide a medical evaluation to determine the employee's ability to use a respirator before the employee is fit tested or required to use the respirator in the cement factory.[36]

The employers should ensure that periodic follow-up medical examination is provided for an employee of a cement factory.[36]

The employer should provide PRGs, respirators, training, and medical evaluations at no cost to the employee.[36]

Limitation of study

The main limitation of this study is that the participants in the two groups (cement exposed and cement unexposed) were not gender matched. This is important because spirometric values are gender dependent. It was largely because cement factories in Nigeria have more male dominant workforce than female while the civil service set up where the controls were recruited from, had no particular gender dominance in its workforce.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Mariammal T, Jaisheeba AA, Sornaraj R. Work related respiratory symptoms and pulmonary function tests observed among construction and sanitary workers of Thoothukudi. Int J Pharm Tech Res2012;4:1266-73.  Back to cited text no. 1
    
2.
World Health Organization. Hazard Prevention and Control in the Work Environment: Airborne Dust; 2010. Available from: http://www.who.int/occupational_health/publications/en/oehairbornedust.pdf. [Last accessed on 2015 Mar 16].  Back to cited text no. 2
    
3.
Meo SA. Lung function in Pakistani wood workers. Int J Environ Health Res 2006;16:193-203.  Back to cited text no. 3
[PUBMED]    
4.
American Lung Association. Occupational Lung Disease Fact Sheet; 2005. Available from: http://www.lungusa.org/site/pp.asp. [Last accessed on 2015 Mar 16].  Back to cited text no. 4
    
5.
American Lung Association Lung Disease Data; 2008. Available from: http://www.lungusa.org/chronicbronchitis. [Last accessed on 2017 Mar 03].  Back to cited text no. 5
    
6.
Draid MM, Ben-Elhaj KM, Ali AM, Schmid KK, Gibbs SG. Lung function impact from working in the pre-revolution Libyan quarry industry. Int J Environ Res Public Health 2015;12:5006-12.  Back to cited text no. 6
[PUBMED]    
7.
7. Ahmed HO, Abdullah AA. Dust exposure and respiratory symptoms among cement factory workers in the United Arab Emirates. Ind Health 2012;50:214-22.  Back to cited text no. 7
    
8.
Neghab M, Choobineh A. Work-related respiratory symptoms and ventilatory disorders among employees of a cement industry in Shiraz, Iran. J Occup Health 2007;49:273-8.  Back to cited text no. 8
[PUBMED]    
9.
Zeleke ZK, Moen BE, Bråtveit M. Cement dust exposure and acute lung function: A cross shift study. BMC Pulm Med 2010;10:19.  Back to cited text no. 9
    
10.
Yang CY, Huang CC, Chang IC, Lee CH, Tsai JT, Ko YC. Pulmonary function and respiratory symptoms of Portland cement workers in Southern Taiwan. Kao Hsing I Hsueh Ko Hsueh Tsa Chih 2003;9:186-92.  Back to cited text no. 10
    
11.
Fell AK, Thomassen TR, Kristensen P, Egeland T, Kongerud J. Respiratory symptoms and ventilatory function in workers exposed to Portland cement dust. J Occup Environ Med 2003;45:1008-14.  Back to cited text no. 11
[PUBMED]    
12.
Al-Neaimi YI, Gomes J, Lloyd OL. Respiratory illnesses and ventilatory function among workers at a cement factory in a rapidly developing country. Occup Med (Lond) 2001;51:367-73.  Back to cited text no. 12
[PUBMED]    
13.
Ballal SG, Ahmed HO, Ali BA, Albar AA, Alhasan AY. Pulmonary effects of occupational exposure to Portland cement: A study from eastern Saudi Arabia. Int J Occup Environ Health 2004;10:272-7.  Back to cited text no. 13
[PUBMED]    
14.
Mwaiselage J, Bråtveit M, Moen B, Yost M. Variability in dust exposure in a cement factory in Tanzania. Ann Occup Hyg 2005;49:511-9.  Back to cited text no. 14
    
15.
Rasmussen FV, Borchsenius L, Holstein B, Sølvsteen P. Lung function and long-term exposure to cement dust. Scand J Respir Dis 1977;58:252-64.  Back to cited text no. 15
    
16.
Edelman P. Asbestos and air flow limitation. J Occup Med 1987;29:264-5.  Back to cited text no. 16
[PUBMED]    
17.
Enright P. Comment on spirometry. J Occup Med 1987;29:842.  Back to cited text no. 17
    
18.
Kilburn KH, Warshaw RH. Airways obstruction from asbestos exposure. Effects of asbestosis and smoking. Chest 1994;106:1061-70.  Back to cited text no. 18
[PUBMED]    
19.
LaDou J. The asbestos cancer epidemic. Environ Health Perspect 2004;112:285-90.  Back to cited text no. 19
[PUBMED]    
20.
Ohar J, Sterling DA, Bleecker E, Donohue J. Changing patterns in asbestos-induced lung disease. Chest 2004;125:744-53.  Back to cited text no. 20
[PUBMED]    
21.
Gomes J, Lloyd OL, Revitt DM. The influence of personal protection, environmental hygiene and exposure to pesticides on the health of immigrant farm workers in a desert country. Int Arch Occup Environ Health 1999;72:40-5.  Back to cited text no. 21
[PUBMED]    
22.
Jinadu MK, Malomo MO. Investigation into occupational health problems of bakery workers in Ile-Ife, Nigerian. Niger Med Pract 1986;12:39-41.  Back to cited text no. 22
    
23.
Alakija W, Iyawe VI, Jarikre LN, Chiwuzie JC. Ventilatory function of workers at Okpella cement factory in Nigeria. West Afr J Med 1990;9:187-92.  Back to cited text no. 23
[PUBMED]    
24.
Ige OM, Onadeko OB. Respiratory symptoms and ventilatory function of the sawmillers in Ibadan, Nigeria. Afr J Med Med Sci 2000;29:101-4.  Back to cited text no. 24
[PUBMED]    
25.
Okojie OH, Egbagbe E, Kadiri I. An epidemiological study of the health status of sawmill workers in Benin city, Edo state. Niger J Med Biomed Res2003;2:76-81.  Back to cited text no. 25
    
26.
Ijadunola KT, Erhabor GE, Onayade AA, Ijadunola MY, Fatusi AO, Asuzu MC, et al. Prevalence of respiratory symptoms among wheat flour mill workers in Ibadan, Nigeria. Am J Ind Med 2004;45:251-9.  Back to cited text no. 26
    
27.
Okwari OO, Antai AB, Owu DU, Peters EJ, Osim EE. Lung function status of workers exposed to wood dust in timber markets in Calabar, Nigeria. Afr J Med Med Sci 2005;34:141-5.  Back to cited text no. 27
[PUBMED]    
28.
Nagoda M, Okpapi JU, Babashani M. Assessment of respiratory symptoms and lung function among textile workers at Kano textile mills, Kano, Nigeria. Niger J Clin Pract 2012;15:373-9.  Back to cited text no. 28
  [Full text]  
29.
Eng J. Sample size estimation: How many individuals should be studied? Radiology 2003;227:309-13.  Back to cited text no. 29
[PUBMED]    
30.
Medarov BI, Pavlov VA, Rossoff L. Diurnal variations in human pulmonary function. Int J Clin Exp Med 2008;1:267-73.  Back to cited text no. 30
[PUBMED]    
31.
British Medical Research Council. Standardized questionnaire on respiratory symptoms. Br Med J 1960;2:1665.  Back to cited text no. 31
    
32.
Meo SA. Health hazards of cement dust. Saudi Med J 2004;25:1153-9.  Back to cited text no. 32
[PUBMED]    
33.
Johncy SS, Ajay KT, Dhanyakumar G, Raj NP, Samuel TV. Dust exposure and lung function impairment in construction workers. J Physiol Biomed Sci 2011;24:9-13.  Back to cited text no. 33
    
34.
Brüske I, Thiering E, Heinrich J, Huster KM, Nowak D. Respirable quartz dust exposure and airway obstruction: A systematic review and meta-analysis. Occup Environ Med 2014;71:583-9.  Back to cited text no. 34
    
35.
Hnizdo E, Glindmeyer HW, Petsonk EL. Workplace spirometry monitoring for respiratory disease prevention: A methods review. Int J Tuberc Lung Dis 2010;14:796-805.  Back to cited text no. 35
[PUBMED]    
36.
United States Department of Labour: Occupational Safety and Health Administration (OSHA) Respiratory Protection Standards (Standard Number 1910.134).  Back to cited text no. 36
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

Top
 
 
  Search
 
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)

 
  In this article
   Abstract
  Introduction
   Materials and Me...
  Results
  Discussion
   Conclusion/Recom...
   References
   Article Tables
 Article Access Statistics
    Viewed319    
    Printed0    
    Emailed0    
    PDF Downloaded45    
    Comments [Add]    

Recommend this journal

[TAG2] [TAG3] [TAG4]