Effects Of Inhaled Carbon Dioxide On Cheyne-stokes Respiration In Patients With Heart Failure

Background:Central sleep apnea is frequently associated with congestive heart failure in the formof Cheyne-Stokes Respiration (CSR-CSA). Central sleep apnea would lead to nocturnalrepetitive oxygen desaturations、arousals and sleep fraction,increase of sympatheticactivity with the consequence of higher mortality risk. Central sleep apnea is recognizedas the independent risk factor correlating with poor prognosis of patients with heart failure.Continuous Positive Airway Pressure (CPAP) and oxygen inhalation are two conventionalmethods used by former researchers.However, these treatments could only lower theApnea Hypopnea Index (AHI) by about50%without entire relief of CSR-CSAand onlyapply to certain people. While it is reported that inhalation of carbon dioxide(CO2) therapycould totally eliminate the CSR-CSA, currently it is still arguable whether inhalation ofCO2therapy would decrease arousals, improve sleeping structure and improve cardiacfunction. The previous studies were short of accuracy to employ the conventionalrespiratory inductance plethysmography to judge the nature of apnea event. As recentstudies have found that diaphragm electromyogram (EMGdi) can effectively reflectneural respiratory drive and determine the accurate nature of sleep apnea event, it is onthis premise of CSR-CSA is judged with accuracy, the research aims at evaluating thetreatment effect of inhalation of CO2therapy to CSR-CSA and providing treatments forheart failure patients with CSR-CSA.Objective:This study is undertaken to precisely identify CSR-CSA event by observing neuralrespiratory drive with the employment of esophageal or surface diaphragm EMG, andevaluate the therapeutic effect of inhalation of CO2therapy to CSR-CSA patients so as tofurther provide suggestions for clinical practice. Methods:Polysomnography (PSG) has been performed on the heart failure patients with severeCSR-CSA symptom for two nights, resting state monitoring without intervention for thefirst night and with CO2therapy for the second night. The specific approach is: Providepatients with air inhalation at the speed of10L/min through medical oxygen mask, thenwait patients to fall asleep until the onset of CSR-CSA, Open the valve of CO2meter(range:0.3-10L/min) after the status stabilizes for5minutes. Taking0.5L/min asthe initiation speed, provide patients with CO2inhalation at low speed in the first place.Observe the signal graph related with sleep status in computer while gradually increasingCO2flow speed. At intervals of5minutes regulate the speed up by0.5L/min, until theCSR-CSA event has disappeared with decreased arousals. Then maintain the speed of CO2inhalation overnight. If the CSR-CSA event reappears at the previously titrated speed andit lasts for more than10minutes, increase CO2flow speed until the CSR-CSA disappears.While adjusting the inhalation speed of CO2, end tidal CO2(ETCO2) of the patient shouldbe controlled below6%in the meantime. If the ETCO2has reached6%, but the CSR-CSAhas not eliminated, stop increasing the CO2flow speed. The inhalation of CO2therapyshould be immediately stopped if the patient wakes up or shows the symptom of abruptpalpitations, dyspnea and nausea. Compare associated parameters of the two nights afterthe experiment.Results:The inhalation of CO2therapy greatly decreases AHI (41.55±8.44events/h vs3.79±1.68events/h, P<0.05) and arousal index (30.01±8.35events/h vs9.80±4.07events/h,P<0.05). Comparison on the ETCO2of patients before and after the inhalation of CO2therapy （4.14±0.59%vs4.45±0.55%，P<0.05），shows that ETCO2with a stable breathincreases1.2±0.9mmHg after CO2therapy. The N3/TST ratio increases after theinhalation of CO2therapy,（4.77±7.03%vs12.22±14.04%，P<0.05）.while the differencebetween the total sleep time of two nights before and after the inhalation of CO2therapy isnot statistically significant (295.83±72.8min vs293.03±71.08min, P>0.05). Fluctuatingwith different body position, AHI increasing from supine to the lateral position(36.01±17.24events/h vs12.49±7.90events/h, P<0.05). Conclusions:1. The CSR-CSA event could be eliminated satisfactorily while heart failure patientsreceive the inhalation of CO2therapy through medical oxygen mask overnight, meanwhilethe inhalation of CO2therapy could decrease arousals and increace deep Morpheus periodratio and improve the quality of patients’ sleep structure.2. Patients with heart failure have a higher risk of occurring CSR-CSA event in supineposition than in lateral position, which may be linked to the changes of oxygen storagecontent in different body positions (higher in lateral position).