The Effect of Aging on the Ventilatory Response to Wearing a Chemical, Biological, Radiological, and Nuclear Hood Respirator at Rest and During Mild Exercise.

Background: Structural changes in the human body resulting from aging may affect the response to altered levels of O-2 and CO2. An abnormal ventilatory response to a buildup of CO2 in the inspired air due to rebreathing may result in adverse effects, which will impair the individual's ability to function under stress. The purpose of this study was to evaluate the effect of age on the respiratory response to wearing an escape hood at rest and during mild exercise. Methods: Subjects were seven healthy, young adult males (20-30 years) and seven healthy, middle-aged males (45-65 years). Inspired CO2 and O-2, breathing pattern (tidal volume [VT] and breathing frequency [F]), and mouth inspiratory and expiratory pressures, were measured at rest and during mild exercise (50 w) while wearing the CAPS 2000 escape hood (Shalon Chemical Industries and Supergum-Rubber and Plastic Technology, Tel Aviv, Israel). Findings: Resting inspired CO2 was higher in the middle-aged group compared with the young group (2.25% +/- 0.42% and 1.80% +/- 0.34%, respectively; p < 0.05). Breathing pattern in the middle-aged group tended to be shallower and faster compared with the young group (VT: 0.69 +/- 0.27 L and 0.79 +/- 0.32 L, respectively; F: 14.7 +/- 4.0 breaths/min and 12.4 +/- 2.8 breaths/min, respectively). During exercise, there was a trend toward a high inspired CO2 in the middle-aged group compared with the young group (2.18% +/- 0.40% CO2 and 1.94% +/- 0.70% CO2, respectively). A correlation was found between age and inspired CO2 when wearing the escape hood (r(2) = 0.375; p < 0.05). Discussion: The age-related decrease in pulmonary function, together with the finding in this study of a higher inspired CO2 in middle-aged subjects wearing the CAPS 2000, may represent a greater risk for persons of middle age wearing an escape hood. Recommendations: On the basis of this study, it would appear reasonable to recommend that new respirators be evaluated on subjects from different age groups, to ensure the safety of both young and old.