How Effective Are Skull Base Repair Techniques Against CPAP? Lessons Learnt through a Novel Cadaver Model

Introduction: Comorbid obstructive sleep apnea (OSA) in patients undergoing skull base surgery represents a challenging cohort of patients to treat postoperatively. Continuous positive airway pressure (CPAP) is considered the gold standard for the treatment of OSA. Recent guidelines recommend early initiation of postoperative positive pressure ventilation. However, the appropriate time to initiate CPAP postoperatively is controversial as the effectiveness of skull base repair techniques to withstand positive pressure is unknown. This study uses a novel cadaver model to objectively analyze the proportion of delivered positive pressure reaching the skull base and the effectiveness of various repair techniques to withstand this pressure.

Materials and Methods: Skull base defects were surgically created in three fresh human cadaver heads and repaired using three commonly used repair techniques—Surgicel onlay, Durepair inlay (with Duraseal onlay) and a Durepair inlay (with Nasoseptal flap [NSF] onlay). Pressure micro-sensors were placed in sella and sphenoid sinus and CPAP were initiated. The effectiveness of each repair technique against various CPAP levels (5–20 cm of water) was analyzed.

Results: On analyzing the proportion of CPAP reaching anterior skull base, it was found that 5 to 21% of the total CPAP delivered at the external nares dissipated before reaching the sphenoid sinus. These pressure levels did not alter with change in repair techniques. Sellar pressure readings on the other hand, were found to be significantly different across the three repair techniques. In fact, across all CPAP levels (5–20 cm of water) the NSF repair transmitted a lower proportion of pressure to sella as compared with the other two techniques.

On comparing the effectiveness of Durepair inlay (with Duraseal onlay) and Durepair inlay (with NSF onlay) to withstand CPAP, it was noted that across most pressure levels (5–17 cm of water), both these techniques behaved almost identical to each other in terms of their capacity to withstand a breach. Additionally, the intrasellar pressures were identical between these two repair techniques in 2 out of 3 heads for all CPAP levels (5–20 cm of water). On analyzing the breach points (level of CPAP where skull base repair gave way), it was noted that Surgicel had the lowest and NSF had the highest breach point.

Conclusion: This novel experiment represents the first consistent and effective cadaveric model to objectively study the effect on positive pressure ventilation on anterior skull base repair techniques. Different skull base repair techniques have different levels of effectiveness against positive pressure ventilation. Durepair inlay (with Duraseal onlay) and Durepair inlay (with NSF onlay) were comparable in their capacity to withstand positive pressure ventilation, with NSF onlay withstanding pressures better between 17 and 20 cm of water.

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