Pulmonary function tests such as spirogram, lung volumes, DLco (S. B.), closing volume, V-V curve, He-O2 V-V curve and respiratory impedance were performed before and after hemodialysis in 14 patients receiving chronic hemodialysis. Blood gas analyses, measurements of VE (BTPS), Vo2 (STPD), Vco2 (STPD) and R (respiratory quotient), and blood cell counts were also studied in 15 patients undergoing hemodialysis.
The patients consisted of 7 males and 8 females, aged from 22 to 58 years. They were all well controlled and did not show respiratory or cardiovascular signs. Hemodialysis was maintained for 5 hours, 3 times per week with a coil dialyser using a cuprophane membrane. Acetate buffer was available for dialysate.
The results were as follows:
1) Before hemodialysis, restrictive impairment was observed in only one patient whereas abnormalities in airway function were shown in FEV1(2 patients), CV% (2), CC% (6), ΔN2 (2), V50 (3), V25 (3) and Visov, (6) respectively.
2) After hemodialysis, VC, TLC, RV and FRC were unchanged. On the other hand, FEV1, CC%, V25, V50/V25, Visov and FRC-CC improved significantly. It was thought to be due to removal of edema surrounding small airways by hemodialysis.
3) In 10 out of 14 patients, DLco and DLco/VA were decreased before hemodialysis. They showed low values even after hemodialysis. Low hemoglobin concentration may be one of the causes of decreased DLco, but other factors might be considered.
4) Pao2 decreased during hemodialysis. The changes in Pao2 and VE correlated significantly. This suggested that hypoventilation was one of the causes of the Pao2 drop during hemodialysis. However A-aDo2 decreased in the early stage of hemodialysis and worsened later. Furthermore, some patients showed low Pao2 after hemodialysis in spite of improvement in small airway function. Improvement in small airway function and disturbance in pulmonary blood flow, such as low cardiac output, pulmonary microembolism and/or leucostasis may cause worsening of VE/Q ratio unevenness. This factor was considered another cause of decreased Pao2 resulting from hemodialysis.
