|Year : 2021 | Volume
| Issue : 1 | Page : 31-35
A study to evaluate ventilatory derangements of 1st year medical students on exposure to formaldehyde by assessing forced expiratory volume in 1 s/forced vital capacity ratio
Dipak Kumar Dhar1, Sudeepa Chaudhuri2
1 Department of Physiology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Jolly Grant, Dehradun, Uttarakhand, India
2 Department of Physiology, Rohilkhand Medical College and Hospital, Bareilly, Uttar Pradesh, India
|Date of Submission||29-Apr-2020|
|Date of Decision||07-Aug-2020|
|Date of Acceptance||10-Sep-2020|
|Date of Web Publication||2-Feb-2021|
Dipak Kumar Dhar
Department of Physiology, Himalayan Institute of Medical Sciences, Swami Rama Himalayan University, Jolly Grant, Dehradun, Uttarakhand
Source of Support: None, Conflict of Interest: None
BACKGROUND: A doctor experiences various occupational hazards. One of them is exposure to formaldehyde during gross anatomy dissection classes. Since it vaporizes at room temperature, the respiratory system is easily affected. The present study was undertaken to assess the ventilatory derangements that occur on this exposure.
METHODS: The spirometric parameter, forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio, was recorded in 80 medical students using spirometer RMS Helios 401. Percent-predicated values were used for analysis. The baseline values were recorded at the beginning of the academic calendar and followed up at the end of the 1st, 6th, and 10th months.
RESULTS: The overall mean FEV1/FVC ratio declined over the study period though not markedly but was statistically significant (P = 0.004). Restrictive and mixed patterns were predominantly seen, but the number decreased with time.
CONCLUSIONS: Formaldehyde causes detrimental effects on the ventilatory dynamics.
Keywords: Forced expiratory volume in 1 s/forced vital capacity ratio, formaldehyde, medical students, ventilatory derangement
|How to cite this article:|
Dhar DK, Chaudhuri S. A study to evaluate ventilatory derangements of 1st year medical students on exposure to formaldehyde by assessing forced expiratory volume in 1 s/forced vital capacity ratio. Int J Health Allied Sci 2021;10:31-5
|How to cite this URL:|
Dhar DK, Chaudhuri S. A study to evaluate ventilatory derangements of 1st year medical students on exposure to formaldehyde by assessing forced expiratory volume in 1 s/forced vital capacity ratio. Int J Health Allied Sci [serial online] 2021 [cited 2022 Aug 12];10:31-5. Available from: https://www.ijhas.in/text.asp?2021/10/1/31/308589
| Introduction|| |
A sound and optimal working environment is a key element for inculcating proficiency in profession and ensuring the good health of the employee. In other words, occupation should not act as an impediment to the health of the person. This forms the fundamental premise of occupational health and safety. The medical community is one of the most highly occupationally exposed communities of the world with a wide spectrum of exposures and risks ranging from chemical to biological hazards. For a doctor, occupational exposure starts early in life in the phase of medical education and training. One of the first in this sequence is the exposure to formaldehyde, which is commercially available in the form of 37% aqueous solution known as formalin. It is extensively used as a component of embalming fluids in anatomy. Embalming fluid is a composite mixture of chemicals that act as fixatives, preservatives, germicides, buffers, wetting agents, anticoagulants, dyes, perfuming agents, etc. which are used to preserve a cadaver in as much good state as possible. Two types of fluids are normally used in the process of embalming: arterial fluid (for the vascular system of the body) and cavity fluid (for the body cavities, i.e., thorax, abdomen, and pelvis). Both these fluids use formalin as the preservative. The formalin concentrations in arterial fluid and cavity fluid are 10% and 60%, respectively. While keeping a provision for spillage, approximately 10 l of arterial fluid is needed for an adult body weighing 65–75 kg. In addition, formalin is also the main preservative used in the tank (immersion) fluids where the cadaver and their parts are stored after the dissection class. Chemically, formaldehyde (HCHO) is an aldehyde which is produced by the oxidation of methyl alcohol. At room temperature, it exists as a gas which has noxious properties and a strong pungent odor.
The study of the human cadaver has been one of the cornerstones of the teaching and learning anatomy. A scrupulous dissection of cadavers provides medical students the portal for reinforcing their theoretical knowledge by visual, auditory, and tactile pathways. In the present day too, even with the best of modern teaching equipment at disposal, the classical method of cadaver-based learning cannot be replaced or paralleled. It is in this context that exposure to formaldehyde becomes unavoidable, and instructors and students routinely handle the cadaver during gross anatomy dissection hours. There is, thus, a consistent exposure to the students for the entire 1st year and often, the rates are high.,
The most appalling concern of formaldehyde is its safety. Today, there is a substantial corpus of evidence in the medical research literature which shows that formaldehyde can be toxic, allergenic, and even carcinogenic on prolonged exposure., Apart from the irritant effects on exposed mucosal surfaces of the body, the respiratory tract is its critical target of toxicity because formalin vaporizes at room temperature to produce air-borne formaldehyde.,,, It has been found that its levels >0.5 ppm in the ambient atmosphere cause altered pulmonary functions and a concentration of around 50 ppm has been associated with chemical pneumonitis.
Formaldehyde has been found to affect both the upper and lower respiratory tracts. Studies suggest that it affects ventilatory dynamics in both the central and peripheral airways.,, Bronchoconstriction is a very plausible mechanism by which the mechanics of ventilation can be altered as formaldehyde has both allergic and irritant effects on the mucosa. Chemical mediators such as serotonin and histamine which are liberated in these processes are known to cause contraction of smooth muscles. Some reports also suggest that there is a IgE-mediated allergic process in the nasal mucosa in susceptible individuals which is also accompanied by a variable degree of contraction of the bronchial smooth muscle. Formaldehyde is also known to polymerize and form paraformaldehyde which has a unique property of adsorbing formaldehyde vapors on their surface. On adsorption, the particles which attain an average size of 1–2 μ become respirable. These particles can easily get carried to the peripheral airways. On deposition, formaldehyde being a toxic and irritant substance would naturally incite an inflammatory reaction which would impair the ease of airflow in these airways. These mechanisms illustrate how the dynamics of ventilation is deranged at multiple levels by formaldehyde. One of the best methods to assess the adequacy of ventilation is by measuring the FEV1/FVC ratio. It is the ratio of FEV1 to FVC. FEV1 is the maximal volume of air exhaled in the 1st s of a forced expiration from a position of full inspiration and FVC is the maximal volume of air exhaled with the maximal forceful effort from the same position after deep inspiration. An altered FEV1/FVC ratio indicates ventilatory impairment, which can be of three types: obstructive, restrictive, or mixed.
Studies conducted on occupational exposure of formaldehyde suggest that small but significant changes occur in lung functions of exposed subjects following prolonged exposure. However, the number of studies assessing ventilatory derangement by the longitudinal measurement of this parameter is limited. With the available data, varying trends and patterns have been observed. This forms the fundamental premise of carrying out the present study. It was intended to evaluate the cumulative effect of the exposure to formaldehyde on the ventilatory mechanics of 1st year medical students by recording their FEV1/FVC ratio.
| Materials and Methods|| |
A longitudinal, descriptive study was conducted in the department of physiology among 1st year MBBS students in the academic year 2015–2016. Approval was obtained from the institutional ethics committee. Students having no history of previous exposure to formaldehyde were considered as subjects. The exclusion criteria comprised of the presence of any prior chronic respiratory diseases such as bronchial asthma, allergic diseases, known allergy to any substance, any acute or chronic inflammatory state, altered baseline pulmonary function test, deformities of the thoracic cage or spine, extremes of height and weight, and those who were not willing to participate in the study. Eighty medical students (40 male and 40 female students) out of the total 150 students were selected employing simple random sampling technique. Taking an equal number of male and female participants ensured better comparability. Before recording the parameter, the nature of the study was explained to every participant and informed consent was obtained. FEV1/FVC ratio was recorded using computerized spirometer RMS Helios 401 (ISO 9001:2008) available in the research laboratory of the department of physiology. The FVC maneuver of the software was used, and all measurements were done in the sitting posture. The best of three such values was recorded as per the guidelines of the American Thoracic Society., The baseline values were recorded at the beginning of the academic calendar and follow-up values at the end of the 1st, 6th, and 10th months. The present guidelines do not advocate the use of absolute values. Instead, they recommend expressing the recorded lung functions as a percentage of the predicted normal values for a subject's age, height, weight, and ethnicity, in the form of percent-predicted values. Therefore, in the present study, percent-predicted values have been used for analysis to eliminate the confounding effect of various anthropometric and other factors. With this method, the normal range of pulmonary function parameters is considered to be within a range of 80%–120% of the predicted values and percent-predicted values <80% represent the suboptimal function., An ventilatory derangement is classified as obstructive on spirometry when the FEV1/FVC ratio below 0.7 or percent-predicted value below 80%. When the FEV1/FVC ratio is normal with a FVC lesser than 80% of predicted value, the derangement is classified as restrictive. When both the components are below 80% of predicted value, it is described as a mixed ventilatory defect.,,, The data were analyzed using SPSS (manufactured by SPSS Inc., Chicago, USA) software. Descriptive statistics and tests like repeated measures ANOVA were used for the analysis of the data. P < 0.05 was considered statistically significant.
| Results|| |
The pattern of changes observed in the FEV1/FVC ratio is shown in [Table 1]. It can be observed from [Table 2] that the cumulative change over the whole study period was statistically significant, and the effect was similar in both males and females.
|Table 1: Percent-predicted forced expiratory volume in 1 s/forced vital capacity ratio of students over the study period|
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|Table 2: Significance of change in forced expiratory volume in 1 s/forced vital capacity ratio on exposure over different spans of time and difference in the effect on male and female students|
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The proportion of participants with different patterns of ventilatory derangements, i.e., restrictive, obstructive, and mixed, at various intervals of time is depicted in [Figure 1]. It can be observed that for most of the participants, the ventilatory dynamics (classified as per criteria mentioned previously) was normal. Moreover, among those with abnormal patterns, restrictive and mixed types of defects were found to be more prevalent. However, with time, their proportion decreased and those with normal pattern increased. This implied that in most of them, the changes reverted back toward normalcy.
|Figure 1: Pattern of ventilation of the participants at different intervals of time|
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| Discussion|| |
The adverse effects on ventilatory mechanics of the participants as observed in the present study are consistent with the fundamental biological behavior of formaldehyde and resonate with similar research works carried out elsewhere by other authors. Mathur and Rastogi in a meta-analysis also concluded that there was a decrease in the FEV1/FVC ratio. Mankar and Ranade and Suhas et al. also documented a significant decrease in both males and females after acute exposure. On the other hand, Akbar-Khanzadeh et al. and Khaliq and Tripathi had reported an increase in the FEV1/FVC ratio after exposure. Binawara et al. observed no significant change in the parameter.
The physiological basis of these effects lies in the high reactivity of formaldehyde. The oxygen atom of the aldehyde group of formaldehyde is highly electronegative. This can react easily with nucleophilic sites on cell membranes and in body tissues such as the amino groups in proteins. In fact, formaldehyde can exert its effect on the body's physiology by multiple mechanisms. Once absorbed from the respiratory tract after inhalation of formaldehyde vapors from the ambient atmosphere, the binding of formaldehyde to endogenous proteins creates “haptens” that can elicit an immune response. Chronic exposure to formaldehyde has been associated with immunological hypersensitivity as shown by elevated circulating IgE levels. This elucidates the plausibility of an allergic mechanism. Chemical inflammation due to the irritant effect of formaldehyde could also exist concomitantly. The string of events that follow once formaldehyde vapor comes in contact with lung parenchyma has been studied in animal models by many investigators, and they show that there is a dose- and duration-dependent alteration in the cytoarchitecture of the epithelium of the lungs. The spectrum ranged from acute interstitial inflammation (pneumonitis), pulmonary fibrosis, and acute purulent bronchitis to acute and chronic lung injury. It was also further observed that Type II pneumocytes also bore the brunt of the injury along with the other cells. It can be logically surmised that this would lead to diminished surfactant synthesis, thereby reducing the ease of airflow and exchange, resulting in impaired ventilation. Chronic inflammation and epithelial injury followed by repair herald a process of fibrosis, which would restrict the expansion of the lungs, thereby altering the physics of ventilation in the airways.
Restoration of homeostasis or steady state is one of the fundamental axioms of physiology. The body tries its best to correct any changes within its internal environment by employing various mechanisms. The same was also observed in the present study [Figure 1]. With time, the body adapts to the cumulative effect to a certain extent. The exact mechanisms, however, remain to be unveiled.
| Conclusions|| |
The study highlights the adverse effects of formaldehyde on the mechanics of breathing with restrictive and mixed patterns of ventilatory derangement being observed predominantly. If future caregivers are themselves exposed to health-related impediments, the sole purpose of occupational health would be defeated with regard to this. We must, therefore, institute steps to reduce exposure of the medical students because they are subjected to formaldehyde on a daily basis during the 1st year. Simple methods such as use of masks, goggles, engineering better ventilation facilities across the dissection hall, and avoiding unnecessary spillage of formalin within the dissection hall premises can markedly cut down on the exposure. Other options that have been used in some places include specially devised dissection beds, modifying the conventional process of embalming by use of accessory chemicals, or alternative embalming fluids.
The authors gratefully acknowledge the students and authorities of Rohilkhand Medical College and Hospital, Bareilly, for their whole-hearted cooperation and unremitting support during the work.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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