Polysomnography in the diagnosis of the obstructive sleep apnea-hypopnea syndrome: where do we draw the line?

response to exercise are the determination of the early normalized oxygen deficit during square wave exercise testing. Due to the inappropriate (suboptimal) increase of the cardiac output at the early onset of exercise, the organism has to rely on anaerobic energy sources with an excess lactic acid accumulation. Therefore, at the onset of exercise, V ˙ o 2 is subtracted from the steady-state value, all breaths are cumulated, and the total oxygen deficit is expressed as a percentage of the total oxygen cost of the exercise level, above the resting value. Previous studies on this topic, in patients with chronic heart failure 8 and in patients with congenital heart disease , 13 have shown that the normalized oxygen deficit is increased in these patients groups, which suggest an inadequate oxygen delivery to the exercising tissue or a metabolic inertia of the muscular tissue, 14 which can be due to deconditioning. Finally, the measurement of V ˙ o 2 kinetics at low intensity (subanaerobic threshold) exercise may provide useful information about the efficiency of the oxygen delivery to the exercising tissue and may give some insight about the mechanisms of exercise limitation in patients with cardiovascular disease. References 1 Wasserman K. Diagnosing cardiovascular and lung patho-physiology from exercise gas exchange. Oxygen uptake kinetics during low level exercise in patients with heart failure: relation to neurohormones, peak oxygen consumption, and clinical findings. Oxygen uptake transient kinetics during constant-load exercise in children after operations of ventricular septal defect, tetralogy of Fallot, transposition of the great arteries, or tricuspid valve atresia. Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure. peak exercise capacity in patients with coronary artery disease. respiratory gas exchange during exercise after correction of congenital heart disease. dynamics of O 2 uptake and heart rate as affected by exercise work rate. oxygen uptake during exercise in adults with cyanotic congenital heart disease. Dynamics of oxygen uptake for submaximal exercise and recovery in patients with chronic heart failure. Where Do We Draw the Line? I n this issue of CHEST (see page 353), Le Bon et al report the largest series to date of consecutive polysomnograms (PSGs) in patients suspected of having the obstructive sleep apnea-hypopnea syndrome (OSAHS). The authors conclude that a single negative PSG does not exclude a diagnosis of OSAHS. The evidence provided plus a review of the literature strongly …