To determine the effect of body posture on the flow rates, flow-volume loop (FVL) configuration and upper airway obstruction (UAO) indices (FEV1/PEF, FEF50/FIF50) before and after thyroid surgery for goiter.
FVLs were measured in four different body postures (sit, supine, left and right recumbent posture) using a spirometer according to ATS standards in 21 consecutive patients before and after thyroid surgery. Flow rates were derived from the envelope FVL. Visual analysis of the FVL was performed to detect flattening of the FVL. UAO indices and flow rates were compared in the different body postures using repeated measures analysis and Bonferroni post-hoc testing when appropiate.
21 patients, 3 men and 18 woman, performed spirometry before and after surgery. Mean age was 49.5 years (range 24–82). Mean body mass index was 26.4 (±SD 4.7). All flow rates decreased significantly in the recumbent postures. Two patients had flattening of the sitting expiratory FVL preoperatively. One normalised, in the other it was postoperatively more ponounced (unilateral vocal cord paralysis). In 3 patients expiratory flattening in the recumbent postures disappeared postoperatively. In one, flattening in the supine and right lateral expiratory FVL persisted postoperatively only in the supine posture. In another, flattening in all four postures persisted only in the sitting and left supine posture. In one obese patient (BMI 28.5) the expiratory recumbent FVLs did not change at all. In 3 patients flattening of the inspiratory FVLs normalised after surgery. The UAO indices did not change significantly with posture, except for the FEF50/FIF50 which preoperatively was significantly lower on the left side compared to the supine posture (p= 0.012).CONCLUSIONS: Performing FVL testing in the supine body postures increases the likelehood of detecting a functional, variable UAO, nor revealed in the sitting posture.
Earlier detection of functional UAO due do tracheal compression by the thyroid gland may be achieved by assessing the FVL in different body postures.
M. Meysman, None.