Study On Influence And Mechanism Of Low Oxygen Pressure On Lung-related Thrombocytopenia

BackgroundIt is a well-known classic concept that the bone marrow is the main hemato-poietic organ and megakaryocytes produce platelets in the bone marrow.Interestingly,in 2017,Lefrancais et al identified the lung as a primary organ of platelet biogenesis,and about 50%of total platelet production is produced in the lungs.There have been reports of thrombocytopenia in patients with lung disease such as pneumonia,chronic obstructive pulmonary disease（COPD）,and respiratory failure,but the cause is not clear.Currently,there are no large-scale clinical observations and basic research reports on the relationship between the lungs and platelets.This study was designed to analyze the factors associated with thrombocytopenia in patients with common lung diseases,and to explore the pathophysiological factors and related mechanisms of thrombocytopenia caused by lung diseases.Section 1 Relationship between Pneumonia and ThrombocytopeniaObjective:To investigate the incidence and influencing factors of thrombocytopenia in patients with pneumonia,to evaluate the interaction between factors and explore the dose-response relationship between influencing factors and the risk of thrombocytopenia.Methods:According to the admission criteria,data of patients with pneumonia and appendicitis admitted to The Second Affiliated Hospital of Nanchang University from January 01,2014 to December 31,2018 were collected,including 3015 patients in the pneumonia group and 1056 patients in the appendicitis group.The clinical data of age,gender,medical record data,blood routine,blood biochemistry,C-reactive protein（CRP）,procalcitonin（PCT）,chest radiograph and color ultrasound were collected.The pneumonia group calculated the clinical pulmonary infection score（CPIS）to assess the severity of pneumonia.The platelet counts<100×10^9/L was defined as thrombocytopenia,in which platelets（99-50）×10^9/L was slightly reduced,and platelets（49-30）×10^9/L was moderate.reduced,platelets<30×10^9/L is a severe reduction.First,compare the incidence of thrombocytopenia and the incidence of moderate to severe thrombocytopenia in patients with pneumonia and appendicitis.Then,Logistic regression analysis was used to analyze the influencing factors of thrombocytopenia in patients with pneumonia.The interaction multiplicative model was used to evaluate the interaction between the influencing factors.Finally,the cubic spline curve model was used to investigate the dose-response relationship between the influencing factors and the risk of thrombocytopenia.Results:1.The incidence of thrombocytopenia in the pneumonia group was higher than that in the appendicitis group（5.9%vs 3.4%,P<0.05）,and the incidence of moderate to severe thrombocytopenia（platelet counts<50×10^9/L）was higher（3.2%vs 1.1%,P<0.05）,the platelet counts were lower in the pneumonia group than in the appendicitis group（202[162,245]vs 219[149,261],P<0.05）,and the mean platelet volume（MPV）was smaller（9.4[7.3,11.4]vs 14.3[12.3,16.2],P<0.05）,platelet distribution width（PDW）was smaller（10.9[8.5,13.6]vs 12.9[10.8,15.0],P<0.05）.There was no significant difference in age,gender,fever symptoms,white blood cells,red blood cells,red blood cell distribution width,CRP,and PCT（all P>0.05）.2.Univariate analysis showed that the risk of thrombocytopenia in patients with pneumonia increased with erythrocytes（OR 1.77,95%CI[1.26-2.47],P<0.05）,and the MPV increased（OR 1.21,95%CI[1.14-1.25],P<0.05）,PDW increased（OR1.13,95%CI[1.10-1.16],P<0.05）,and CPIS score increased（OR 1.08,95%CI[1.01-1.17],P<0.05）.Multivariate logistic regression analysis showed that the larger MPV（OR 1.19,95%CI[1.12-1.25],P<0.05）and the higher CPIS scores（OR1.08,95%C I[1.01-1.17],P<0.05）showed a higher risk of thrombocytopenia.There is no interaction between the above two factors based on the multiplicative model（OR1.01,95%CI[0.99-1.04],P>0.05）.3.The dose-response analysis of the influencing factors and the risk of thrombocytopenia showed that there was a positive linear dose-response relationship between the MPV and CPIS score and the risk of thrombocytopenia(P_overall<0.05,Pnon-linearity>0.05).Conclusions:1.Patients with pneumonia have a higher incidence of thrombocytopenia,lower platelet counts,smaller MPV,and smaller PDW than patients with appendicitis.2.The lager MPV and high CPIS are risk factors for thrombocytopenia in patients with pneumonia.3.There is a positive linear dose-response relationship between MPV and CPIS and the risk of thrombocytopenia.Section 2 Relationship between COPD and ThrombocytopeniaObjective:To observe the incidence of thrombocytopenia in patients with COPD,to analyze the factors associated with thrombocytopenia in patients with COPD,to evaluate the interaction between various factors,and to explore the dose-response relationship between influencing factors and the risk of thrombocytopenia.Methods:A total of 401 patients with COPD admitted to The Second Affiliated Hospital of Nanchang University from January 01,2014 to May 31,2018 were collected,according to the admission criteria.The baseline age,gender,respiration,baseline dyspnea index（BDI）,blood routine,blood biochemistry,blood gas analysis,lung function,comorbidities and other information of all patients were collected.Two consecutive platelet counts <100 × 10^9/L or platelets decreased by ≥50% from baseline,defined as thrombocytopenia（endpoint event）.Patients were followed up for thrombocytopenia within 6 months and they were signed out once thrombocytopenia appeared.The data of acute exacerbations of COPD was obtained in the follow-up period.According to a nested case-control study design,21 patients with thrombocytopenia during the follow-up period as a case group,42 cases of patients without thrombocytopenia as a control group.A frequency of 1:2 according to age and gender was matched between case group and control group.Logistic regression was used to analyze the factors related to the onset of thrombocytopenia in patients with COPD.Then the interaction multiplication model was used to evaluate the interaction between the influencing factors.Finally,the cubic spline curve model was used to explore the dose response relationship between the influencing factors and the risk of thrombocytopenia.Results:1.During follow-up,the proportion of thrombocytopenia in patients with COPD was 5.8%,and the proportion of moderate to severe thrombocytopenia was4.0%.2.Univariate logistic regression analysis showed MPV（OR 0.67,95%CI[0.52-0.86],P<0.05）,forced expiratory volume 1 as a percentage of predicted value（FEV1%）<50%（OR 5.46,95% CI [1.39-21.33],P<0.05）,and blood oxygen partial pressure（PaO₂）（OR 0.94,95%CI[0.92-0.98],P<0.05）are related factors for thrombocytopenia in patients with COPD.Multivariate logistic regression analysis showed that FEV1 accounted for <50% of the predicted value（OR 5.73,95% CI[1.12-29.41],P <0.05）is a risk factor for thrombocytopenia.Elevated PaO₂（OR 0.95,95% CI [0.91-0.98],P < 0.05）and increased MPV（OR 0.71,95% CI [0.54-0.95],P<0.05）reduced the risk of thrombocytopenia.There are no interactions between the two factors based on the above three factors（all P>0.05）.3.The dose-response analysis on the related factors and the risk of thrombocytopenia in COPD patients showed that there was a negative linear dose-response relationship between MPV and PaO₂ and the risk of thrombocytopenia（Poverall<0.05,Pnon-linearity>0.05）.Conclusions:1.Reduced PaO₂,decreased MPV and FEV1% of predicted value <50% are risk factors for thrombocytopenia in patients with COPD.2.There is a negative linear dose-response relationship between MPV and PaO₂ and the risk of thrombocytopenia.Section 3 Relationship between Respiratory Failure and ThrombocytopeniaObjective:To investigate the incidence of thrombocytopenia and influencing factors in patients with respiratory failure,to evaluate the interaction between factors and explore the dose-response relationship between influencing factors and the risk of thrombocytopenia.Methods:A total of 675 patients with respiratory failure admitted to The Second Affiliated Hospital of Nanchang University from January 01,2014 to December 31,2018 were collected according to the admission criteria.Collect all patients’ age,gender,medical records and vital signs,blood routine,blood biochemistry,CRP,PCT,imaging,blood gas analysis data,and calculate acute physiology and chronic health evaluation（APACHE II）to assess the severity of the disease.The platelet count <100×10^9/L was defined as thrombocytopenia,in which platelets <50×10^9 / L is a moderate to severe reduction.Logistic regression analysis was used to analyze the pathogenesis-related factors of thrombocytopenia in patients with respiratory failure.Then,the interaction between the influencing factors was evaluated by interaction multiplication model.Finally,the cubic spline curve model was used to explore the dose response relationship between the influencing factors and the risk of thrombocytopenia.According to PaO₂ value,the patients were divided into mild hypoxemia group（PaO₂≥50mm Hg）;moderate hypoxemia group（PaO₂ 49 ⁴0mm Hg）;severe hypoxemia group（PaO₂ <40 mm Hg）was compared between the three groups of platelet counts and incidence of thrombocytopenia.Results:1.The incidence of thrombocytopenia in patients with respiratory failure was15.0%,and the proportion of moderate to severe thrombocytopenia was 8.0%.2.Univariate logistic regression analysis showed that both moderate hypoxemia group（OR 2.74,95%CI[1.70-4.41],P<0.05）and severe hypoxemia group（OR14.50,95%CI [6.92-30.39],P<0.05）suffered a higher risk of thrombocytopenia than mild hypoxemia group.The APACHE II score（OR 1.09,95% CI [1.02-1.15],P<0.05）was positive associated with the risk of thrombocytopenia.Patients with COPD suffered a higher risk of thrombocytopenia than that without COPD（OR 2.35,95% CI[1.22-4.53],P<0.05）.Howerver,patients with hypertension suffered a lower risk of thrombocytopenia than that without hypertension（OR 0.64,95%CI [0.41-0.99],P<0.05）.3.Multivariate logistic regression analysis showed that low PaO₂ was still the most important risk factor for thrombocytopenia in patients with respiratory failure.Patients with moderate hypoxemia were 3.13 times more likely to suffer thrombocytopenia compared with mild hypoxemia group,while patients with severe hypoxemia were 11.6 times.In addition,this study found a high APACHE II score with a high risk of thrombocytopenia（OR 1.08,95% CI [1.006-1.15],P<0.05）.Patients with COPD had a higher risk of thrombocytopenia than patients without COPD（OR 2.60,95% CI [1.30-5.20],P < 0.05）.There are no interactions between the two factors based on the above three factors（all P<0.05）.4.Dose-response analysis of influencing factors and risk of thrombocytopenia showed a negative linear dose-response relationship between PaO₂ and thrombocytopenia（Poverall<0.05,Pnon-linearity>0.05）,There was a positive linear dose-response relationship between APACHE II score and the risk of thrombocytopenia（Poverall<0.05,Pnon-linearity>0.05）.5.Mild hypoxemia group（N=443）,moderate hypoxemia group（N=196）,severe hypoxemia group（N=36）.The platelet counts in the severe hypoxemia group was lower than in the mild and moderate hypoxemia group（63.5 [47.5-191.8] vs 170.5 [113.0-255.8] vs 178 [131.0-219.0],all P<0.05）.There was no significant difference between patients with mild hypoxemia group and moderate hypoxemia group（P>0.05）.The incidence of patients with thrombocytopenia in the severe hypoxemia group was higher than that in the other gourps.（58.3% vs 20.9% vs 8.8%,all P < 0.05）,and the incidence of patients with moderate to severe thrombocytopenia was also high（33.3% vs 2.5% vs 0.5%,P < 0.05）;the incidence of patients with thrombocytopenia in the moderate hypoxemia group was higher than in the mild hypoxemia group,and the incidence of patients with moderate to severe thrombocytopenia was also high.Conclusions:Reduced PaO₂ is the most important risk factor for thrombocytopenia in patients with respiratory failure.There is a negative linear dose response relationship between the PaO₂ and the risk of thrombocytopenia.Section 4 Experimental Study on the Effects of Chronic Hypoxia on Megakaryocytes and PlateletsObjective:The influence of low PaO₂ on megakaryocytes of the lung,bone marrow and spleen and platelets was explored in hypoxemia mouse models induced by chronic hypoxic.Methods:Sixteen mice were randomly divided into hypoxia group（N=8）and control group（n=8）.Mice in the hypoxia group were housed in a hypoxic environment for 28days（oxygen concentration of 8%）.The number of megakaryocytes in the lung,bone marrow and spleen was detected by flow cytometry and pathological immunofluorescence staining respectively.Platelet-related parameters in blood samples from the orbital vein（peripheral blood）,right ventricle（pre-lung）,and left ventricle（post-lung）were measured by a blood cell analyzer.Results:1.Compared with the control group,the PaO₂ in the hypoxia group was significantly decreased（57.14±6.39 vs 76.63±9.58,P<0.05）;the peripheral blood platelet counts were significantly decreased（518.38 ± 127.92 vs 840.75 ± 77.30,P<0.05）;MPV reduction（7.24 ± 0.11 vs 7.56 ± 0.23,P < 0.05）.2.Compared with the control group,the ratio of CD41+ cells in the lung,bone marrow and spleen of the hypoxic group was lower than that of the control group:lung tissue flow cytometry showed（6.09[5.66,6.71] vs 8.82[8.26,10.27],P<0.05）,immunofluorescence staining showed（39.0±5.35 vs 54.25±12.87,P<0.05）;bone marrow tissue flow cytometry showed（2.11 ± 1.12 vs 5.03 ± 1.72,P<0.05）,immunofluorescence staining（10.00 ± 2.78 vs 24.88 ± 3.68,P<0.05）;spleen flow cytometry showed（0.39[0.36,0.59] vs 0.74[0.66,1.03],P<0.05）,immunofluorescence staining（2.75±1.04 vs 8.75±5.29,P< 0.05）.3.The post-lung platelet counts of the control group was significantly higher than that of the pre-lung platelet counts（713.63±124.15 vs 543.75±121.17,P<0.05）,while the post-lung platelet counts of the hypoxic group was not significantly different from the pre-lung platelet counts（387.22 ± 110.35 vs 339.00 ± 89.32,P>0.05）.Compared with the control group,the difference between pre-lung and post-lung platelet counts（△ post-pre）was significantly decreased in the hypoxic group（F=25.47,P<0.05）.Conclusions:Low PaO₂ causes thrombocytopenia and a decrease in MPV,which may be related to hypoxemia inhibiting megakaryocyte proliferation and reducing the number of platelets produced in the lung.