SVC expiratory comapared to SVC inspiratory : a retrospective study

Sammanfattning

Slow vital capacity (SVC) is an important parameter in pulmonary function testing and may provide a more accurate estimate of lung volumes than forced vital capacity (FVC), particularly in obstructive and restrictive lung disease. However, it remains unclear whether inspiratory and expiratory SVC maneuvers yield equivalent results. To investigate whether differences exist between inspiratory and expiratory SVC measurements in individuals with normal lung function, obstructive lung disease (OLD), and restrictive lung disease (RLD), this retrospective study included 123 adults who underwent pulmonary function testing between November 2024 and January 2026 at a single clinical center in Sweden. Participants were classified into normal (n=55), obstructive (n=38), and restrictive (n=30) groups according to ATS/ERS 2022 criteria. All subjects performed both expiratory and inspiratory SVC maneuvers. Agreement between methods was assessed using Bland–Altman analysis, and between-group differences were evaluated using one-way ANOVA. No significant differences were observed between inspiratory and expiratory SVC within any group. Mean SVC values were comparable across maneuvers in normal (4.02±0.92 vs 4.06±0.94 L), obstructive (2.81±1.18 vs 2.78±1.13 L), and restrictive groups (2.86±0.90 vs 2.94±1.03 L). Bland–Altman analysis demonstrated no systematic bias and good agreement between methods. Significant differences in SVC were observed between groups (p<0.001), with higher values in the normal group. Inspiratory and expiratory SVC maneuvers yield equivalent and clinically interchangeable results across different lung function patterns. These findings support flexibility in maneuver selection and highlight the importance of standardized spirometry techniques to ensure reliable pulmonary function assessment.