Influence of Noninvasive Respiratory Support Techniques on Gas Exchange in Cardiac Surgical Patients Suffering from Post-Operative Respiratory Failure

Respiratory failure (RF) after tracheal extubation occurs in 5–25% of cardiac surgical patients. Various noninvasive respiratory support techniques are available for RF treatment. The purpose of the study is a comparative assessment of the effect on gas exchange of oxygen inhalation through a mask with noninvasive airway positive pressure mask ventilation, and high-flow lung ventilation during post-extubation respiratory failure in cardiac surgical patients. Materials and methods. 52 cardiac surgical patients with post-extubation respiratory failure (mean age 61 (55–67) years) were included in the study. Respiratory failure critera were as follows: PaO2/FiO2 _ 300 mm Hg or SpO2 _ 88% during room air breathing. Exclusion criteria included presentation of pleural effusion in patients, pneumothorax, diaphragm paresis. Every patient was subjected consecutively to arterial blood gases test during room air breathing, low-flow oxygen therapy using a mask with a pre-volume bag, high-flow ventilation (HFNC), and noninvasive positive pressure mask ventilation (NIPPV). Each method was applied during 1 hour prior to the test. Respiratory rate (RR) and capillary blood saturation (SpO2) were monitored throughout the whole study. Results. PaO2/FiO2 during low-flow oxygen therapy was equal to 171 (137–243) mm Hg. At the background of HFNC, this index increased to 235 (183–305) mm Hg ( P =0.00004), and upon transfer to NIPPV — to 228 (180–288) mm Hg ( P =0.000028). SpO2 during HFNC and NIPPV increased from 95 (93–98)% to 98 (96–99)% ( P =0.000006) and 97 (95–98)%, respectively ( P =0.000006 and P =0.000069). PaCO2 was higher during oxygen mask breathing compared to air breathing: 41 (37–44) mm Hg and 38 (34–42) mm Hg, correspondingly, P =0.0017. Upon transfer to HFNC, PaCO2 lowered on average by 10% (37 (33–39) mm Hg, P =0.0000001), to NIPPV — by 7% (38 (36–42) mm Hg, P =0,0015). Differences were also significant when compred RR during oxygen mask breathing (20 (16–24) respirations/minute) vs. HFNC (16 (12–20) respirations/minute, P =0.0) and vs. NIPPV (18 (16–20) respirations/minute, P =0.018). Comparison of HFNC vs. NIPPV revealed reliable difference in RR (16 (12–20) respirations/minute against 18 (16-20) respirations/minute, P =0.016), PaCO2 (37 (33–39) mm Hg against 38 (36–42) mm Hg, P =0.0034), and SpO2 (98 (96–99)% against 97 (95–98)%, P =0.022). Conclusion. HFNC and NIPPV exert a similar positive effect on the oxygenating function of lungs and gas exchange in cardiac surgical patients with post-extubation respiratory failure. Compared to NIPPV, high-flow ventilation renders most significant positive effect on elimination of CO2, RR and SpO2, and is better tolerated by patients.