[Is ASV therapy a positive airway pressure or ventilation therapy? A comparison of acid-base balance per day and under ASV].

UNLABELLED: The aim of this work was to determine whether therapy with adaptive support ventilation (ASV) leads to impairment of acid-base balance, in particular to hypocapnia and alkalosis. For this purpose, we measured the acid-base status (SBH) with carbon dioxide and oxygen partial pressure in arterialized blood (pCO2 and pO2), standard bicarbonate (SBC) and pH under spontaneous breathing during the day and under ASV at night. The trigger for this work was, among other things, the result of the SERVE-HF study, which found an increased risk of mortality in patients with heart failure and left ventricular ejection fraction <45% under ASV. There was a presumption of a device algorithm-based effect. The question was whether the minimum pressure support (PSmin) of 3 cmH2O via respiratory alkalosis has a pro-arrhythmogenic effect (and causes higher mortality). A study of patients with treatment-emergent central sleep apnea (TECSA) and normal cardiac function comparing 4 ASV devices showed significantly higher ventilation with the device used in the study. So, this excessive ventilation could be generated by the device and not by class.

METHODS: A total of 226 patients who came to the follow-up of the ASV from 10/2018 to 03/2020; age 65.2±11.3 years, BMI 35.7±7.5 kg/m2, service life 5530±5400 h, 5.6±2.5 h/d, PSmin 4.9±1.8 cmH2O. None of the patients had heart failure (EF>45%). The majority underwent ASV because of TECSA, rarely a cardiac or other genesis.

RESULTS: In 29 patients (12.8%) hypocapnia with pCO2 <36 mmHg was found in the morning.

CONCLUSION: Under ASV we could not determine any class effect of hypocapnia. 12.8% had hypocapnia, and in half of the cases it was severe necessitating modification of therapy. This can have different causes but there are no clear criteria. As there is a risk of hyperventilation, acid-base balance under ASV should be checked.