Comparing the Inspiratory Capacity Measurements Obtained by Incentive Spirometry and Ultrasonic Spirography in the Early Postoperative Period in Cardiac Surgery Patients

Abstract

Incentive spirometry is one of the most common methods used for respiratory rehabilitation in the early period after cardiac surgery. Inspiratory capacity values, obtained by a patient using spirometer, are not reliably trusted.Objectives. To compare volumetric parameters measured with incentive spirometer and results obtained with bedside ultrasound-based spirometer to assure the feasibility of the use of incentive spirometry to assess the inspiratory capacity and effectiveness of postoperative respiratory rehabilitation.Materials and methods. The study included 50 patients after elective cardiac surgery. Pulmonary rehabilitation involved the use of various respiratory therapy methods. Spirography was performed before and after each session. Both approaches were used simultaneously to obtain the spirometry maximum inspiratory capacity (SMIC) with a bedside ultrasonic spirography and maximum inspiratory capacity (MIC) index using an incentive spirometer. Patient’s discomfort and adverse events during the procedures were recorded.Results. The absolute values of the MIC measured before and after each session by the two methods were dissimilar, however, the average increment values (6) did not show statistically significant differences. The correlation analysis revealed a strong positive statistically significant relationship between 6 SMIC and 6 MIC (R = 0.74 before the session, R = 0.79 after the session, R = 0.77 across the whole data set, P < 0.01), also consistent with the Bland–Altman analysis, evidencing that more than 95% of all values fell within ± 1.96 SD of the mean difference. The inspiratory spirometry method showed good diagnostic accuracy (sensitivity 87%, specificity 85%, area under the curve (AUC) 0.8 (95% CI: [0.76; 0.83]), P < 0.001). Refusals of procedure were more often documented with ultrasonic spirography.Conclusion. The increment in the inspiratory capacity index measured with incentive spirometer shows good agreement with ultrasonic spirography measurements. Therefore, incentive spirometry can be reliably used to assess the effectiveness of respiratory rehabilitation interventions in cardiac surgery patients during early postoperative period.