Tehran University Medical Journal

---

Background: Both hypoxia and hypocapnia can cause broncho-constriction in humans, and this could have a bearing on performance at high altitude. The objective of this study was to examine how pulmonary ventilatory function during high-altitude trekking.
Methods: This study was a before and after study on spirometric parameters at Base line (1150 m above sea level), and after ascending at 4150 m above sea level. This study was performed in summer 2004 at Cialan Mountain in Iran. Fifty six healthy male University student volunteers were enrolled in the study. Respiratory function was assessed in participants before ascending at baseline (1150 meter) and after ascending at 4150 meter in Cialan Mount with a Spirolab II. Spirometric parameters changes were compared using paired t-test statistical analysis computations were performed by spss 11.5 and p≤0.05 was considered significant.
Results: The mean age and body mass lindex of our subjects were 22.9±5.3 years and 21.5±2.5, respectively. Forced vital capacity (FVC) was significantly decreased with increasing altitude from baseline level (P<0.01). Forced expiratory volume in 1 second to forced vital capacity ratio (FEV1/FVC) and maximal midexpiratory flow rate (FEF 25-75%) were significantly increased with increasing altitude (P=0.001). There was no significant change in forced expiratory volume in 1 second and peak flow (P>0.05). FVC fell by the average of 7.1% at 4150m (2.4% per 1000m increased altitude) in comparison to 1150m.
Conclusion: The changes in some pulmonary ventilatory parameters were proportional to the magnitude of change in altitude during a high-altitude trek.

---

Background: Because bronchial hyper responsiveness (BHR) has been shown to be a risk factor for asthma and lung function decline, interest has focused on diagnosing BHR. The aim of our study was to measure the association between airway caliber relative to lung size expressed as the ratio between forced expiratory flow, mid expiratory phase, divided by forced vital capacity (FEF25-75/FVC) and BHR measured by methacholine challenge test (MCT) to obtain a cutoff for this ratio and positive MCT.
Methods: We carried out a cross- sectional study on general Iranian population in 376 subjects aged 7-73 years who were referred to Shariati hospital in Tehran, Iran in an outpatient setting. There were 190 male (50.5%) and 186 female (49.5%) subjects. They had chronic respiratory symptoms such as cough and dyspnea. The physical examination was normal. Baseline spirometry was normal or equivocal. MCT was done for all subjects over a two year period (2009- 2010). Positive MCT was defined by PC 20≤4mg/ml.
Results: The methacholine challenge test was positive in 191 (50.8%) and negative in 185 (49.2%) patients. The mean of FEF25-75/FVC in positive MCT was 0.86±0.27 Vs. 0.91±0.28 in the negative ones (p=0.070). The sensitivity and specificity of FEF25-75/FVC for prediction of MCT results were 57.1% and 60.2% based on cutoff point of 0.85 in all patients, and 87.5% and 70.7% based on cut off point of 1 in allergic patients, respectively.
Conclusion: The FEF25-75/FVC appears to be a useful predictive ratio in allergic patients but not in general population.

---

Background: Asthma is a life-threatening disease that can cause death due to bronchospasm. In addition to clinical symptoms such as wheezing, acute paroxysmal dyspnea, chronic cough after exposure to cold air or cough after exercise, spirometry is also necessary for the diagnosis of asthma. The association between respiratory symptoms and a positive methacholine challenge test (MCT) is still controversial. The aim of this study was to determine the association between methacholine test results and respiratory symptoms and allergy.

Methods: One hundred and forty-six patients with respiratory symptoms and normal baseline pulmonary function tests were enrolled in this cross-sectional study. The participants were divided into two groups according to their positive or negative response to MCT. The association between MCT and the clinical symptoms and allergy was later evaluated statistically.

Results: Out of 146 participants of the study 59 (40.4%) were female and 87 (59.6%) were male. The mean age of the participants was 33.8±13.8 years. Sixty-one patients (41.8%) had positive results for the test. There was an association between a history of allergy, wheezing and age with positive MCT results. The other clinical signs had no association with the test.

Conclusion: Methacholine challenge test is the best diagnostic test for ruling out asthma in patients with normal pulmonary function tests in whom we cannot definitely rule out asthma based solely on clinical symptoms. Nevertheless, in adults with a history of allergy, wheezing and also in patients below 30, the probability for a positive MCT is high.