Impacts Of Pulmonary Artery Pressure On Acute Mountain Sickness And Cardio-respiratory Fitness After High Altitude Exposure

Background and Objectives:According to statistics, more than140million people worldwide live at highaltitude（above2500m） and about40million tourists visit plateau every year.Our countryhave the largest plateau area in the world, and more than60million residents are living atthe plateau above3000m.There are countless others sojourn to the mountains for work,travel, and security task.High altitude exposure with pulmonary artery pressure increased,acute mountain sickness（AMS） and exercise capacity impaired are well known, but therelationships among them are unclear.For the present, studies on high altitude pulmonary hypertension （HAPH） have shownthat pulmonary artery pressure increased caused by hypoxic pulmonaryvasoconstriction（HPV） and pulmonary vascular remodeling after high attitude exposure.Pulmonary hypertension（PH） increased the afterload of right heart,impaired rightventricular function and reduced exercise capacity by the decline of maximal cardiac output（CO） during exercise. In addition,it also impaired gas exchange capacity which lead tohypoxemia. Pasiewicz G found that pulmonary artery pressure elevated with mild tomoderate （mPAP25.4±8mmHg） in normal people after high attitude exposure, and thecrowd of borderline PH is an important part of the population.In other types of PH, some studies have shown that borderline PH also can lead toright ventricular dysfunction and decline of exercise capacity. Borderline PH indicated ahigher risk and poor prognosis. However, the research on the borderline PH secondary tohigh altitude exposure is lacking, strengthen the management and intervention of borderlinePH might be a better way to improve the exercise capacity and cardio-respiratoryfitness（CRF）For the above reasons,we studied the influences of pulmonary artery pressure on AMSand CRF after acute and chronic high altitude exposure. Especially,we assessed the incidence of borderline PH and the impacts on CRF for the first time.Study design:1. From september2011to september2013, a total of299healthy chinese young malevolunteers were recruited who come from the plain group（450m）, acute high altitudeexposure group（3700m₂4h） and chronic high altitude exposure group（3700m_≥1y）.Theheart rate（HR）,blood pressure（BP）, saturation of oxygen（SaO2） of all subjects weremeasured by the appointed doctors.2. Echocardiographic recordings were obtained in all subjects by ultrasounddoctors.Mean PAP was estimated by using pulmonary acceleration time（AT）,when AT≥120ms, mPAP=79－（0.45×AT）;when AT＜120ms, mPAP=90－（0.62×AT）.3. Cardio-respiratory fitness was assessed by a modified physical working capacitytest that predicted the workload at a heart rate of170beats per minute （PWC170）.4. Structured questionnaires made up of the lake louise acute mountain sicknessscoring system（AMS-LLS） were answered by all subjects of acute high altitude exposuregroup.5. Subjects were further divided by mPAP into three subgroups consisting of normal（<20mmHg）, borderline （20to25mmHg） and confirmed PH （≥25mmHg） within eachexposure group.6. Compare the differences of AMS incidence,AMS symptoms and AMS score amongsubgroups in acute high altitude exposure group.7. Compare the differences of CRF among subgroups in acute and chronic highaltitude exposure group,find out the relationship between mPAP and CRF,especially clarifythe influence of borderline PH on the CRF.Results:1. Acute and chronic high altitude exposure groups have higher mPAP （23.08±6.97mmHg and20.03±4.78mmHg） than plain group （14.29±3.46mmHg），p＜0.01. Thereare28.57%of the Acute and37.23%of the chronic high altitude exposure people’s mPAPat the level of borderline PH.2. AMS incidence, AMS score among subgroups in acute altitude exposure groupshowed no significant difference, p>0.05. And the incidence of AMS symptoms as"Headache, Dizziness, Gastrointestinal, Difficulty sleeping" also showed no significant difference （p>0.05）, but the incidence of "fatigue/weakness" in PAP normal subgroup is38.89%, lower than the borderline PH（65.38%） and confirmed PH（72.41%） subgroup, havesignificant difference（p=0.02）.3. CRF which assessed by PWC170was impaired both in acute （807.10±127.08kg.m.min-1） and chronic （871.73±97.00kg.m.min-1） high altitude exposures groups,in comparing to plain group （1003.96±158.16kg.m.min-1）. PWC170of the acute groupwas significantly lower than the chronic group （p＜0.001）.Among the subgroups of normalPAP, borderline PH, and confirmed PH in each of the exposure groups the PWC170wassignificantly different. The PWC170in the borderline PH subgroup （acuteexposure:803.92±99.42kg.m.min-1; chronic exposure:858.06±77.26kg.m.min-1） was higherthan the confirmed PH subgroup （acute exposure:731.83±103.49kg.m.min-1; chronicexposure:770.80±62.44kg.m.min-1）, but lower than the normal PAP subgroup （acuteexposure:870.03±130.86kg.m.min-1; chronic exposure:902.10±100.35kg.m.min-1）.Among subjects exposed to high altitude, PWC170was negatively correlated with mPAP（acute exposure: r=-0.407, p﹤0.001; chronic exposure: r=-0.384, p﹤0.001）Conclusions:1. mPAP increased after acute and chronic exposure to high altitude,about1/3of thesubjects at the level of borderline PH.2. The increase of mPAP was not related to the incidence and scoring of AMS.3. The elevated of PAP impaired CRF in healthy young men,and the CRF ofborderline PH subgroup was higher than the confirmed PH subgroup,but lower than thenormal PAP subgroup after acute and chronic high altitude exposure.