LMR spectroscopy: a new sensitive method for on-line recording of nitric oxide in breath

Laser magnetic resonance spectroscopy (LMRS) is a sensitive and isotope-sel ective technique for determining law concentrations of gaseous free radical s with high time resolution. We used this technique to analyze the nitric o xide (NO) concentration profile while simultaneously measuring the flow and expired volume during several single breathing cycles. Eight healthy, nona llergic volunteers were investigated. An initial NO peak was found in all b reathing cycles before the NO concentration dropped to a relatively stable plateau in the late phase of expiration. The nasal NO peak was significantl y higher than the oral NO peak. The nasal NO plateau was always higher than the oral NO plateau. The height of the initial nasal and oral NO peak rose with increasing duration of breath hold, whereas the late expiratory NO pl ateau changed only little for either the nasal or the oral breathing cycles . Our findings demonstrate, in line with other reports using other techniqu es, that the nose is the primary source for NO within the airways.