In studies evaluating regional anesthesia techniques for breast surgery, pain intensity and opioid consumption have traditionally served as the primary endpoints [2]. However, with the increasing awareness of opioid-related adverse effects and postoperative pulmonary morbidity, investigators have begun to explore broader functional outcomes, including respiratory parameters, quality of recovery, and early mobilization [3]. Although conceptually appealing, the selection and interpretation of respiratory outcomes in this setting remain challenging, particularly after procedures such as MRM, which predominantly induces restrictive rather than obstructive ventilatory changes.

In this issue of the Korean Journal of Anesthesiology, Akgün et al. [4] report a randomized study evaluating the impact of combined ultrasound-guided rhomboid intercostal plane (RIP) and serratus anterior plane (SAP) blocks versus no blocks on postoperative respiratory function in patients who have undergone MRM. Notably, the primary outcome, i.e., forced expiratory volume in 1 second (FEV₁) measured at 2-hours postoperatively, did not show a significant difference between the block and control groups. In contrast, several secondary outcomes, including forced vital capacity (FVC), peak expiratory flow, and forced expiratory flow at 25%–75%, were significantly improved at later postoperative time points in patients who received the combined blocks. Consistent with previous studies, the postoperative pain scores and opioid requirements of these patients were reduced, particularly during the early postoperative period.

Failure to meet the primary endpoint might raise concerns regarding the clinical value of the intervention. However, such an interpretation poses the risk of overlooking important physiological and methodological considerations. FEV₁ primarily reflects expiratory flow and is affected by airway resistance and expiratory muscle effort [5]. In contrast, postoperative respiratory impairment after MRM is more typically characterized by a restrictive ventilatory pattern that results from pain-related chest wall splinting, reduced inspiratory effort, and decreased lung volume, rather than by airflow limitation. Within this framework, FVC may serve as a more sensitive marker, reflecting impaired inspiration and pain-limited lung expansion better than does FEV₁ alone.

The discordance between FEV₁ (which remained unchanged) and FVC (which improved) observed in this study underscores a critical interpretative caution: improved analgesia does not necessarily translate into uniform changes across all spirometric parameters. Rather than indicating inefficacy, the neutral finding for the primary outcome highlights the importance of aligning outcome selection with the physiological effects expected from the intervention. Similar inconsistencies have been reported in studies evaluating other fascial plane blocks, such as erector spinae plane and transversus abdominis plane blocks, in which reductions in pain and opioid consumption did not always result in FEV₁ improvements [6,7].

From a clinical perspective, the findings of Akgün et al. [4] suggested that combined RIP and SAP blocks should not be interpreted as a strategy primarily for improving early postoperative FEV₁. Instead, their potential value lies in facilitating better inspiratory effort, reducing pain-related chest wall restriction, and minimizing opioid exposure, which are factors that may collectively contribute to safer recovery in selected patients, particularly those at a higher risk of opioid-related adverse respiratory effects. The absence of block-related complications and the relative technical simplicity of ultrasound-guided administration of these blocks further support the feasibility of using these techniques as part of multimodal analgesia, particularly in patients at a higher risk of opioid-related adverse respiratory effects.

Nevertheless, caution should be exercised when extrapolating these findings to routine clinical practice. Although the secondary respiratory parameter improvements were statistically significant, the clinical magnitude of these improvements was modest, and the study was not powered to detect differences in clinically meaningful outcomes, such as atelectasis, pneumonia, or length of hospital stay. Moreover, numerous perioperative variables can influence postoperative respiratory function, including the anesthetic technique, patient positioning, chest wall dressings, and baseline pulmonary reserve; all of these can dilute the observable effects of a block.

Beyond the immediate findings, this study contributes to the broader discourse on outcome selection in regional anesthesia research. With the field moving beyond pain scores alone, future trials should prioritize endpoints that more closely reflect patient-centered as well as clinically meaningful benefits. Composite outcomes incorporating early mobilization, postoperative pulmonary complications, or validated recovery scores may better capture the multidimensional impact of regional anesthesia than do isolated spirometric measurements [2]. Additionally, further investigations into continuous block techniques, use of analgesia-prolonging adjuvants, and the optimal timing of block administration are warranted to clarify how regional anesthesia can most effectively support postoperative recovery [8,9].

In conclusion, Akgün et al. [4] have provided valuable insights into the complex relationship between regional anesthesia, pain control, and respiratory function after breast surgery. Although the primary endpoint results were neutral, improvements in secondary respiratory parameters and analgesic outcomes underscore the need for a nuanced interpretation rather than making a binary judgment of success or failure based solely on statistical significance.