The difference in respiratory and blood gas values during recovery after exercise with spontaneous versus reduced breathing frequency

Extrapolation from post-exercise measurements has been used toestimate respiratory and blood gas parameters during exercise.this may not be accurate in exercise with reduced breathingfrequency (rbf), since spontaneous breathing usually followsexercise. this study was performed to ascertain whether measurementof oxygen saturation and blood gases immediately afterexercise accurately reflected their values during exercise withrbf. eight healthy male subjects performed an incrementalcycling test with rbf at 10 breaths per minute. a constant loadtest with rbf (b10) was then performed to exhaustion at thepeak power output obtained during the incremental test. finally,the subjects repeated the constant load test with spontaneousbreathing (sb) using the same protocol as b10. pulmonaryventilation (ve), end-tidal oxygen (peto2), and carbon dioxidepressures (petco2) and oxygen saturation (sao2) were measuredduring both constant load tests. the partial pressures ofoxygen (po2) and carbon dioxide (pco2) in capillary bloodwere measured during the last minute of exercise, immediatelyfollowing exercise and during the third minute of recovery. atthe end of exercise rbf resulted in lower peto2, sao2 and po2,and higher petco2 and pco2 when compared to spontaneousbreathing during exercise. lower sao2 and peto2 were detectedonly for the first 16s and 20s of recovery after b10 compared tothe corresponding period in sb. there were no significant differencesin po2 between sb and b10 measured immediatelyafter the exercise. during recovery from exercise, petco2 remainedelevated for the first 120s in the b10 trial. there werealso significant differences between sb and b10 in pco2 immediatelyafter exercise. we conclude that rbf during highintensity exercise results in hypoxia; however, due to postexercisehyperpnoea, measurements of blood gas parameterstaken 15s after cessation of exercise did not reflect the changesin po2 and sao2 seen during exercise.