| Background and objectivesIn recent years, with the development of traffic and the western China, more and morepeople travel rapidly to high altitudes for work or entertainment. After rapidly ascending tohigh altitude, some plain residents suffer a clinical syndrome composed of a series ofsymptoms, known as acute mountain sickness (AMS). High altitude pulmonary edema andcerebral edema are severe forms of altitude illnesses. Low-barometric hypoxia at altitude isthe fundamental cause of AMS. Improving the oxygen supply is the main method to preventAMS, high altitude pulmonary edema and cerebral edema. Normal respiratory function is aguarantee in the maintenance of adequate oxygen supply. Normal pulmonary function aswell is important to maintain the respiratory function. Pulmonary dysfunction leads tohypoxia and carbon dioxide retention, as well as decreased right heart function throughincreasing pulmonary vascular resistance. So far, some researchers have studied the effectof acute high-altitude exposure on lung function and its relationship with AMS, but therewere some defects in study design and controversies in results. It has not been reportedwhether decreased right ventricular function at altitude relates to changes in pulmonaryfunction.This study was designed to investigate the changes of right ventricular function andpulmonary function after acute high-altitude exposure; the relationship between pulmonaryfunction, right ventricular function and AMS; and the correlation between pulmonaryfunction and right ventricular function.Materials and methodsInclusion criteria: healthy lowland residents; volunteered to participate in this studyand signed the informed consent forms; over18years of age; never smoke. Exclusioncriteria: Tibetan; long-term high-altitude living history (>2500m for six months or more); high-altitude exposure history (>2500m) during the past six months; recently (during thepast week) took any drugs that may influence cardiopulmonary function. We randomlyselected73eligible participants from some soldiers who would ascend to high altitude forwork. Demographic, lung function and right ventricular function data were collected at400m before going to plateau. Then the subjects ascended to3450m by car, and had theirpulmonary function and right ventricular function collected after exposure to high altitudefor20hours. Later they ascended to3900m. There Lake Louise score, lung function andright heart function were measured at120hours after exposure to high altitude. In order toobtain reliable data of reaction velocity index of pulmonary function, we corrected the flowindex by calibration pressure.Results1.1Effect of high-altitude exposure on right heart function and pulmonary function1.1.1Pulmonary function changes in three places were analyzed using one-wayanalysis of variance (ANOVA). The results showed that FVC, V50, V25and MMF weredecreased at altitude (3450m and3900m) compared with sea level (p <0.05). FVC, V50,V25and MMF was further decreased at3900m compared with3450m (p <0.05). FEV1,PEF and V75did not have significant difference among the three places.1.1.2Tei index was increased while E/A ratio decreased at high altitude (3450mand3900m) compared with sea level (p<0.05). Tei index and E/A ratio did not differbetween3450m and3900m (p>0.05).1.2Correlation between pulmonary function and right heart function1.2.1The correlation between pulmonary function and right heart function at sea levelThe correlation between pulmonary function and right heart function at sea level wasevaluated using Pearson test. The results showed no significant correlation among all theindexes of pulmonary function and all parameters of right heart function.1.2.2The correlation between pulmonary function and right heart function at3450mThe correlation between pulmonary function and right heart function in Xinduqiao wasevaluated using Pearson test. The results indicated that there was no significant correlationamong all the indexes of pulmonary function and all parameters of right heart function at3450m. 1.2.3The correlation between pulmonary function and right heart function at3900mThere was no significant correlation among all the indexes of pulmonary function andall parameters of right heart function at3900m.1.2.4The correlation between the variation amplitudes of pulmonary function andright heart function at3450mPulmonary function measured at3450m divided by that at sea level represents thevariation amplitude of lung function after arrival at3450m. Right heart function measuredat3450m divided by that at sea level represents the variation amplitude of right heartfunction after arrival at3450m. There was no significant correlation among the variationamplitudes of FVC, MMF,V50，V25of pulmonary function and all parameters of right heartfunction at3450m.1.2.5The correlation between the variation amplitudes of pulmonary function andright heart function at3900mThere was no significant correlation among the variation amplitudes ofFVC,MMF,V50，V25of pulmonary function and all parameters of right heart function at3900m.2. Relationship between right heart function, pulmonary function and AMS2.1The occurrence of AMSThe incidence of AMS was49.31%while the incidence of severe AMS was13.69%at3900m. The incidences of the five symptoms were as follows: headache (63.01%),gastrointestinal symptoms (14.34%), dizziness/lightheadedness (58.9%), difficulty insleeping (27.39%) and fatigue/weakness (67.12%).2.2The relationship between pulmonary function and AMS2.2.1The relationship between pulmonary function at sea level and AMSAccording to Lake Louise scores at3900m, the subjects were divided into AMS groupand non-AMS group. The differences of pulmonary function at sea level between the twogroups were evaluated using t tests. The results showed no significant difference.2.2.2The relationship between pulmonary function at3450m and AMSThe differences of pulmonary function at3450m between the two groups were alsoevaluated using t tests. The results showed that FVC in AMS group were lower than thosein non-AMS group, but there is no significant difference in FEV1, PEF, MMF, V50, V25, V75.2.2.3The relationship between pulmonary function at3900m and AMSThe differences of pulmonary function at3900m between the two groups were alsoevaluated using t tests. The results showed that FVC, MMF, V50and V25in AMS groupwere lower than those in non-AMS group.2.2.4Difference of pulmonary function at3450m divided by that at sea levelbetween the two groupsPulmonary function can be affected by lots of factors, such as height, weight and age.Pulmonary function measured at3450m divided by that at sea level represents the variationamplitude of lung function after arrival at Xinduqiao. The differences of the variationamplitude of pulmonary function at3450m between the two groups were analyzed using ttests. The results showed that the variation amplitude of FVC, MMF, and V25in AMSgroup is larger than those in non-AMS group.2.2.5Difference of pulmonary function at3900m divided by that at sea levelbetween the two groupsThe differences of the variation amplitude of pulmonary function at3900m betweenthe two groups were analyzed using the same method. The results showed that thevariation amplitude of FVC, MMF, V50and V25in AMS group is larger than those innon-AMS group.2.3The relationship between right heart function and AMS2.3.1The relationship between right heart function at sea level and AMSRight heartfunction did not differ between AMS and non-AMS groups at sea level.2.3.2The relationship between right heart function in3450m and AMSAt3450m, Tei index of AMS group was higher than that of non-AMS group, whileE/A ratio in AMS group was lower than that in non-AMS group.2.3.3The relationship between right heart function at3900m and AMSAt3900m, Tei index in AMS group was higher than that in non-AMS group, while E/Aratio of AMS group was lower than that of non-AMS group.2.3.4Difference of right heart function at3450m divided by that at sea levelbetween the two groupsRight heart function measured at3450m divided by that at sea level represents the variation amplitude of right heart function after arrival at3450m. The differences ofvariation amplitude of right heart function at3450m between the two groups were evaluatedusing t tests. The results showed that the variation amplitude of Tei index and ratio of E/A ofAMS group were higher than those of non-AMS group.2.3.5Difference of right heart function at3900m divided by that at sea levelbetween the two groupsThe variation amplitude of Tei index and ratio of E/A of AMS group were higher thanthose of non-AMS group.Conclusion1. Pulmonary function showed restrictive decline, accompanied by a decrease in thefunction of small airways after acute high-altitude exposure.2. Right heart function was decreased after acute high-altitude exposure.3. For healthy subjects, there was no correlation between right heart function andpulmonary function after high-altitude exposure, which suggests that the deterioration ofpulmonary function will not affect right heart function for those healthy people whosepulmonary function is not heavily damaged.4. For healthy subjects, there was no relationship between pulmonary function andright ventricular function at sea level and AMS. However, right heart function andpulmonary function at altitude and their variation amplitudes were related to AMS. |
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