Establishment Of Experimental Methodology And Serial Clinical Studies On ATP Cough Provocation Test

Research Background:Cough is a complex reflex that begins when airway epithelial receptors(receptors)receive external stimuli.The cough receptors consist of the vagus nerve endings of the airway and the bronchial trees that mainly include myelinated Aδ and unmyelinated C fibers.Cough is induced when reaching to the threshold.Physiological cough is a crucial defensive reflex of the respiratory system,which prevents foreign bodies from being inhaled and facilitates the cleaning of airway secretions.However,impaired respiratory-related functions or increased cough-related neurosensitivity can cause harm to the body.Chronic cough is often manifested by an abnormally increased cough response caused by mechanical and physical and chemical factors.Common causes of chronic cough include gastroesophageal reflux cough,upper airway cough syndrome,allergic cough,cough variant asthma,and eosinophilic bronchitis.After treatment,cough symptoms may be relieved or even disappeared.Refractory cough is the subtype of cough that persists in some patients and cannot be alleviated after excluding known causes and after the initiation of standardized empirical treatment.The cough hypersensitivity syndrome(CHS)proposed in recent years has gradually received attention.The clinical characteristics of CHS are mainly chronic irritating dry cough,which is sensitive to one or more cough stimuli such as cold air,speech,and odor.CHS significantly affects the quality of life.However,the diagnosis lacks objective criteria.At present,there are advantages and disadvantages for different methods of evaluating the severity of cough.The detection of cough sensitivity has been widely used,and new therapeutic targets are available based on different stimulant receptors.Patients with chronic cough are divided into two categories based on the presence of imaging abnormalities.Chronic cough without imaging abnormalities is mostly not related to infection,and hypersensitivity is considered to be an important pathogenesis.Therefore,in addition to the common causes of chronic cough,treatment of refractory cough is relatively limited,and mainly relies on reducing the cough sensitivity.Bronchiectasis is a typical infectious chronic cough typical disease.The current treatment mainly facilitates airway mucus clearance and reduces airway inflammation.Research objective:To compare the difference in cough sensitivity to ATP and Cap in patients with refractory cough based on the methodology of ATP cough provocation test;to compare the sensitivity to ATP and Cap in patients with chronic cough and refractory cough.Section 1:Establishment of ATP cough challenge test methodology and comparison with cough sensitivity mediated by Cap.Background:ATP is an agonist for P2X3 receptors,but the reference value of ATP cough sensitivity has not been established.Whether the cough sensitivity of patients with refractory cough to ATP is different from healthy controls is not entirely clear.Objective:To analyze the distribution characteristics,reference values and safety of sensitivity to ATP cough provocation test in patients with refractory cough.Methods:59 patients with refractory cough and 20 healthy controls were included.ATP and Cap cough provocation test,which contains the inhalation of(0.1-316 mmol/L)ATP solution in semi-logarithmic concentration and double concentration increasing of Cap(1.95～1000umol/L),was performed.The ROC curve was used to assess the ability of the ATP cough provocation test to identify patients with refractory cough.We compared lung ventilation function before and after cough provocation test,and recorded adverse events.We recorded the ATP concentration causing five cough or more(C5),maximum number of coughs in 30 s(Emax),concentration of cough-causing substance that reached half of the maximum number of coughs(ED50)and Emax/ED50 ratio in the first 30 seconds.The threshold that defines cough hypersensitivity,and correlation of cough sensitivity mediated by ATP and Cap was evaluated.Results:The cough sensitivity of patients with refractory cough was significantly higher than that of healthy subjects.The lgC5 of patients with refractory cough(median 2.0,IQR 1.0)was significantly lower than that in healthy controls(median 3.0,IQR 1.0).Of all parameters,C5 index had the highest Youden index(0.543).After logarithmic conversion,the cut-off value of C5 is 100 mM,ED50 is 100mM,and the ATP high sensitivity was defined as C5≤100 mM.The positive rate was 59.3%in patients with refractory cough and 25%in the healthy controls after ATP inhalation.After Cap inhalation,the positive rate of patients and healthy controls was 71.9%and 25%respectivly The lgC5 of ATP correlated with that of Cap cough provocation test(r=0.549,P=0.000).The incidence of pharyngeal irritation(63.8%)in ATP cough provocation test was significantly lower than that of Cap(28.8%)(χ2=14.40,P<0.001).There were no serious adverse events.Conclusion:The ATP cough provocation test is safe and and feasible.The cough sensitivity mediated by ATP is related to Cap.Section 2:Relationship between clinical characteristics and cough sensitivity in patients with refractory coughBackground:Cough hypersensitivity is an important pathogenesis of chronic cough.The ATP cough provocation test and the Cap cough provocation test are evaluation methods of cough sensitivity,but the clinical characteristics of different subtypes of cough hypersensitivity are not yet clear.Objective:To compare the clinical characteristics of patients with different cough sensitivities of two cough provocation test in patients with refractory cough.Methods:Fifty-three patients with refractory cough and 20 healthy controls were included,and all subjects were cross-over with ATP and Cap cough provocation test in random order.We compared the distribution characteristics of C5,ED50,Emax,Emax/ED50 and the adverse events of the two tests.We also compared the differences between gender subgroups and cough character subgroups.Meanwhile,the differences in the VAS,LCQ,and day and night symptom scores of patients with dhypersensitivity and non-hypersensitivity were observed.Results:Cap cough hypersensitivity was defined as C5≤125umol/L,and ATP cough hypersensitivity as C5≤100mmol/L.The daytime cough score(median 4.0)of patients with refractory cough in the hypersensitivity group was higher than that in the Cap-hypersensitivity group(median 3.0)(P=0.045).The VAS(median 66.3)in the hypersensitivity patient group was higher than the non-hypersensitivity group(median 52.9)showed an increasing trend(P=0.065).Females(ATP lgC5 median 1.5,Cap lgC5 median 1.8)with refractory cough were significantly more sensitive to ATP(P=0.001)and Cap(P=0.024)than men(ATP lgC5 median 2.5,Cap lgC5 median 2.1).Conclusion:Females with refractory cough were significantly more sensitive to ATP and Cap than men.Section 3:Comparison of cough sensitivities mediated by ATP and Cap between people with bronchiectasis and refractory coughBackground:Some patients with bronchiectasis have high cough sensitivity,which can reduce the quality of daily life.The difference in cough hypersensitivity between the patients with bronchiectasis and patients with refractory cough is unclear.Objective:To compare the clinical characteristics of people with different cough sensitivities in patients with bronchiectasis and refractory chronic cough mediated by ATP and Cap.Methods:ATP and Cap cough provocation tests were crossed-over in 62 patients with chronic cough,73 patients with bronchiectasis and 20 healthy controls,respectively.We compared the ATP and Cap cough sensitivity based on C5,Emax,ED50,Emax/ED50.Patients with bronchiectasis were categorized as having less sputum production(<30ml/d)and more sputum production(≥30ml/d),and the difference in cough sensitivity mediated by ATP and Cap was compared.We also compared the differences in cough properties and quality of life scores among these subgroups.Results:In ATP cough provocation test,the lgC5 of patients with bronchiectasis was significantly higher than(P=0.017)than that in patients with refractory cough.However,in the Cap cough challenge test,the lgC5 of patients with bronchiectasis was not significantly different from that of patients with refractory cough(P>0.05)).For ATP cough provocation test,lgC5 was significantly lower in females than in males(P=0.014),and patients with sputum volume≥30ml/d had lower ED50(P=0.040)and higher Emax/ED50(P=0.027)among patients with bronchiectasis.For Cap cough provocation test,the lgC5 of female patients was also significantly lower than that in males(P=0.012);the lgC5 of patients with moderate(P=0.039)and severe(P=0.023)bronchiectasis was significantly lower than that of mild bronchiectasis.Cap cough sensitivity correlated with BHQ quality of life score(r=0.494,P<0.001),while ATP cough sensitivity was not significantly related to BHQ(P>0.05).There was no significant correlation of lgC5 between ATP and Cap cough provocation test in patients with bronchiectasis(P>0.05).Conclusion:The ATP and Cap cough sensitivity of female patients with refractory cough and bronchiectasis is higher than that of male patients.The increased cough sensitivity of Cap correlates with the quality of life in patients with bronchiectasis.