AGING, RESPIRATORY EFFORTS DURING SLEEP, AND PULSUS PARADOXUS

Forty patients with either obstructive sleep apnea syndrome or a clini cal complaint of daytime sleepiness with measured nocturnal increase i n upper airway resistance and snoring were investigated during sleep f or the presence of pulsus paradoxus, which is defined as a decrease in systolic blood pressure (SBP) of at least 10 mmHg during inspiration. Two thirds of the subjects presented pulsus paradoxus. Age, lowest ox ygen saturation (SaO2), and negative inspiratory esophageal pressure n adir (an index of inspiratory effort) were the only studied variables which could statistically dissociate patients presenting pulsus parado xus. We then divided the patient population into three different subgr oups of equal number based upon the degree of decrease in SBP (i.e., > 20 mmHg, <20 but >10 mmHg, and <10 mmHg). In this second analysis, age was the only significant variable that separated the three groups. Lo west SaO2 could not be used to statistically separate subjects with mi ld to moderate pulsus paradoxus from those without it; and negative in spiratory esophageal pressure measurements could only significantly id entify subjects with severe pulsus paradoxus (i.e., >20 mmHg) from tho se without any pulsus paradoxus. The variable which correlated best wi th age was negative inspiratory esophageal pressure nadir (R = 0.83). Our interpretation is that as age increased, negative inspiratory esop hagel pressure became less negative, due to the known impact of aging on muscles, and pulsus paradoxus was no longer observed.