Chronic and acute effects of "crack" cocaine on diffusing capacity, membrane diffusion, and pulmonary capillary blood volume in the lung.

STUDY OBJECTIVES: To evaluate possible alterations in the diffusing capacity of the lung for carbon monoxide (DLCO) or its components, membrane diffusing capacity of the lung for carbon monoxide (DMCO) and pulmonary capillary blood volume (Vc), in habitual smokers of "crack" cocaine (with or without tobacco) and following the short-term administration of inhaled cocaine base or IV cocaine HCl. DESIGN: Cross-sectional and longitudinal evaluation of DLCO and its components in smokers of cocaine alone, tobacco alone, and cocaine plus tobacco, and in nonsmokers and ex-smokers. Measurement of possible acute effects on DLCO and its components after experimental short-term administration of IV and smoked cocaine. SETTING: University and Veterans Affairs hospital research laboratories. PARTICIPANTS: Convenience sample of habitual smokers of crack cocaine with or without tobacco and matched control nonsmokers and ex-smokers, and smokers of tobacco only. MEASUREMENTS: DLCO, DMCO, and Vc. CONCLUSIONS: Neither habitual cocaine smoking in cross-sectional or longitudinal analysis nor the short-term administration of inhaled alkaloidal cocaine significantly affected DLCO or its component parts. In contrast, a clear cross-sectional effect of regular tobacco smoking was demonstrated.

Effect of Jaw and Head Position on Airway Resistance in Obstructive Sleep Apnea.

This study evaluated whether changes in jaw and neck position caused substantial airway resistance (Raw) changes in normal controls and obstructive sleep apnea (OSA) subjects. Subject groups included 12 male nocturnal polysomnographically diagnosed OSA patients and 16 healthy male control subjects. Raw was assessed plethysmographically and measured under the following conditions: neutral head posture with 0/3, 1/3, 2/3, or 3/3 of the subjects maximum forward jaw position; normal jaw (0/3 forward) with fully flexed, extended, right or left rotated head position. Both groups showed a similar significant decrease in Raw upon jaw protrusion. OSA patients showed a significantly higher baseline (normal jaw, neutral head posture). Raw and both subject groups also had a clear increase in their airway resistance with flexion and to a lesser extent with neck rotation and extension. These data document that airway resistance can be significantly influenced by head and jaw positioning with protrusion of the jaw reducing Raw and flexing the neck increasing Raw.