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Introduction
The research article by Brito et al. (2007) for High Altitude Medicine and Biology explored the topic of chronic intermittent hypoxia at high altitude exposure for over twelve years. The scholars assessed the renal, cardiovascular and haematological effects. The study was of quantitative design and involved healthy army personnel exposed to intermittent hypoxia for twelve or more years. The cross-sectional design of the study implied measuring the changes occurring among study participants as a result of being at high altitudes. Geographically, the research was conducted in Chile and involved the town of Putre, which is on the edge of Lauca National Park. The aim of the critical appraisal describes the evidence of the study, investigate the exposure, outcome, study population, study design and result summary. It will also explore the non-causal explanation such as confounding variable, chance and observation bias. The appraisal will highlight the positive features of main Bradford hill criteria, the eligibility and generalizability of the study for occupational worker working in high altitude area.
Summary
Chronic intermittent hypoxia (CIH), which is a focus of the study, refers to the prolonged exposure of individuals to high altitudes. CIH is an occupational, biologic, and epidemiological condition that can exasperate to a chronic status and lead to adverse health complications. The condition is common among individuals that work in high altitudes in contexts such as mining, frontier works or observatories. The research is especially relevant to Chile, where a large part of the population is involved in the extraction of minerals and is therefore exposed to long shifts. The scholars aimed to explore the impact of CIH because previous findings showed increased blood pressure, sleep disorders, moderately high haematocrit, as well as a slight enlargement of the right ventricle.
The study offers a comprehensive overview of the effects of CIH on the health outcomes of individuals operating at high altitudes and includes a broad range of measures. They included cardiovascular, echocardiographic, haematological and biochemical variables, altitude symptoms, renal function, as well as participants medical measures. Through quantitative analysis conducted with the help of SPSS, the researchers were able to identify the changes in health status. The key finding of the analysis pertained to the occurrence of a persistent acute reaction to exposure. CIH was shown to pose a significant challenge to the acclimatisation of study participants, either in chronic or acute phases to achieve the desired degree of acclimatisation to the condition. These results suggest that long-term CIH has undesirable effects on pulmonary circulation, which means that the subjects cannot become acclimated during their shifts the same way as the residents living at high altitudes do.
Critique
The disadvantage of the study is that its results are preliminary. Also, there is a degree of observation bias because the scholars did not include a control group, which could have increased the reliability of the findings for comparison. It is expected that the study was already pre-determined to find correlations between CIH and adverse health conditions. The researchers mentioned the setting of the study, the mechanisms associated with CIH and the prolonged exposure to the lack of oxygen were not explained. No confounding variables were included in the study, which is another significant limitation. It refers to a variable that influences both the independent and dependent variables, leading to the emergence of a spurious association between them. The issue of chance was not accounted for by the researcher. However, it was acknowledged that an error could have appeared during making connections between an outcome and an exposure due to the lack of a control group. The chance of a measurement error has increased due to the use of physical measurements of the sample as well as the inclusion of information from medical records. Moreover, the researcher didnt address the instrument reliability if it is up to standards or calibrated according to manufacture requirement. The scholars revealed that the target population had been adversely influenced by hypoxia on the first day at a high altitude, with the effect being compensated on the second day but the researcher didnt address the effects in the finding. The researcher didnt come across the inclusion and exclusion criteria of the subjects. The study cannot be generalized to other occupational setting as the subject is army participant who have high body fitness and done in one geographical area and under certain weather condition. Moreover, each industry have it is hazards with could exacerbate which do not only have to deal with the risk of CIH development but also with other dangerous activities
There are many strengths in this study such as the study title is eye catch as the reader can clearly identify the study topic and objective. The abstract present the main compound of the study including the aim, methodology, finding and brief conclusion of the study. The studys advantage is associated with the researchers implementing the first epidemiologic research of a population with the occupation implying the work on high altitudes for over twelve years. At the time of the articles publishing date, there had been few studies that had assessed CIH as an occupational issue in the same manner that Brito et al. (2007) did and these is well addressed in the introduction as a literature review. The epidemiologic study attempted to assess the biological and health statuses in a CIH population by considering the range of factors that contribute to the declining health status. For example, when measuring the acute acclimatisation response exhibited by the study participants, it was revealed that the adjustment occurred faster in the study population from the second day onward compared to the chronically intermittent group.
The Bradford Hill criteria included in the study included the strength, which suggested that there were other studies pointing out the connections between CIH and adverse cardiovascular factors. Consistency was present because of the similarity in findings over several studies that supported in the literature review. Specificity is important to note because there were no other studies published involving longer periods of exposure beyond twelve years of experience. In this research, temporal sequence plays an important role as there were extended times spent in high altitudes as compared to other research. Dose response does not apply to the current study as no medical interventions were carried out. Experimental evidence in the current study refers to the consistency in studies conducted on the topic of CIH, all of which supported the findings of the present study. Biological plausibility applies in this case as there is a possibility to reproduce the evidence further. Analogy is seen in the association of critical outcomes to enhancing the quality of the study. By having a control group, analogous research can be implemented in the future.
Conclusion
The study by Brito et al. (2007) is valuable as the researchers offered a comprehensive overview of the effects of CIH on the health outcomes of individuals operating at high altitudes and includes a broad range of measures. They found an increase in blood pressure, sleep disorders, moderately high haematocrit, as well as a slight enlargement of the right ventricle. These results suggest that long-term CIH has undesirable effects on pulmonary circulation, which means that the subjects cannot become acclimated during their shifts the same way as the residents living at high altitudes do. The studys advantage is that the researchers implemented the first epidemiologic research of a population with the occupation implying the work on high altitudes for over twelve years.
Reference List
Brito, J., Siqués, P., León-Velarde, F., De La Cruz, J., López, V. and Herruzo, R. (2007) Chronic intermittent hypoxia at high altitude exposure for over 12 years: assessment of haematological, cardiovascular and renal effects, High Altitude Medicine & Biology, 8(3), pp. 236-244.
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