Feasibility of neurally synchronized and proportional negative pressure ventilation in a small animal model

Abstract

Abstract Rationale Synchronized positive pressure ventilation is possible using diaphragm electrical activity (EAdi) to control the ventilator. It is unknown whether EAdi can be used to control negative pressure ventilation. Aim To evaluate the feasibility of using EAdi to control negative pressure ventilation. Methods Fourteen anesthetized rats were studied (380–590 g) during control, resistive breathing, acute lung injury or CO2 rebreathing. Positive pressure continuous neurally adjusted ventilatory assist (cNAVAP+) was applied via intubation. Negative pressure cNAVA (cNAVAP−) was applied with the animal placed in a sealed box. In part 1, automatic stepwise increments in cNAVA level by 0.2 cmH2O/µV every 30 s was applied for cNAVAP+, cNAVAP−, and a 50/50 combination of the two (cNAVAP±). In part 2: During 5‐min ventilation with cNAVAP+ or cNAVAP− we measured circuit, box, and esophageal (Pes) pressure, EAdi, blood pressure, and arterial blood gases. Results Part 1: During cNAVAP+, pressure in the circuit increased with increasing cNAVA levels, reaching a plateau, and similarly for cNAVAP−, albeit reversed in sign. This was associated with downregulation of the EAdi. Pes swings became less negative with cNAVAP+ but, in contrast, Pes swings were more negative during increasing cNAVAP− levels. Increasing the cNAVA level during cNAVAP± resulted in an intermediate response. Part 2: no significant differences were observed for box/circuit pressures, EAdi, blood pressure, or arterial blood gases. Pes swings during cNAVAP− were significantly more negative than during cNAVAP+. Conclusion Negative pressure ventilation synchronized and proportional to the diaphragm activity is feasible in small animals.

Keywords

• diaphragm electrical activity
• neural control of breathing
• patient‐ventilator interaction