Physiology of aging related to outcome in the adult respiratory distress syndrome

Abstract

Thirty-nine patients with adult respiratory distress syndrome (ARDS) were enrolled in a study to identify potential age-related changes in organ system function that may help explain the apparent association between age and poor outcome in these patients. Criteria for enrollment included an arterial PO2-to-inspired O2 concentration ratio less than or equal to 200 in a clinical setting consistent with ARDS. Patients were excluded if they were less than 18 yr old, had clinical manifestations of congestive heart failure, were seropositive for the human immunodeficiency virus, or had stage II metastatic lung cancer. Patients were divided into two groups: those less than 60 yr old (mean 42 +/- 3 yr, n = 17) and those greater than or equal to 60 yr old (73 +/- 2 yr, n = 16). A group of six patients was analyzed as a separate subset based on a body temperature less than or equal to 97.5 degrees F at enrollment (hypothermic patients, 73 +/- 4 yr old). Sepsis was present in 67% of the nonhypothermic patients and in all the hypothermic patients. Mortality rates were 12% in the patients less than 60 yr and 69% in the nonhypothermic patients greater than or equal to 60 yr. All the hypothermic patients died. Sequential data obtained over 6 days were compared within and between groups. The following results were obtained. 1) The ratio of arterial PO2 to inspired O2 fraction was greater and the positive end-expiratory pressure used was significantly less in the patients greater than or equal to 60 yr old compared with the younger group.(ABSTRACT TRUNCATED AT 250 WORDS)

ARDS in Aged Patients: Respiratory System Mechanics and Outcome

“…Although difference in ICU mortality between the thee age groups did not reach statistical significance, probably due to the small size of our age-groups, our findings are consistent with previous reports in larger ARDS cohorts showing significantly higher mortality in aged ARDS patients [36,37]. Age related declines in cardiovascular function [10], increased incidence of sepsis [38] and presence of chronic underlying health problems, have been suggested, among others, as possible explanations.…”

“…As per our protocol however, we were obliged to maintain the ventilatory settings selected by patients' attending physicians, which at any event reflect common practice [35]. Previous studies identified the use of lower PEEP levels in elderly patients [10,36]. In the present cohort, the similarity of ventilator settings between the three age groups may be interpreted by the comparable physiologic measurements across the age spectrum.…”

“…To the contrary, there are studies showing better oxygenation indices in older ARDS patients. In fact, Gee et al in a small cohort of ARDS patients found that PaO 2 /FiO 2 ratio was greater in the patients >60 years old as compared with the younger group [10]. Similarly, Eachempati et al studied 343 ARDS patients in a surgical ICU and reported that the younger patients (<65 years) presented with lower initial PaO 2 /FiO 2 [8].…”

“…In this respect, possible alterations in respiratory system mechanics encountered in ARDS could be expressed differently between younger and older patients. In addition, a possible age-related bias in ventilator settings selection may explain the differences in ventilatory settings that have been detected between ARDS age groups [10]. The objectives of our study were to identify potential age-related differences in respiratory mechanics, gas exchange and ventilator settings in patients with early ARDS.…”

The APPS: an outcome score for the acute respiratory distress syndrome

“…Tertile categorization detected useful information about the overall population that was not as evident when evaluating mean values of those variables. In general, outcome is worse with increasing age (17), patients with more severe lung injury tend to have lower PaO 2 /FiO 2 (4), and there is a direct relationship between plateau pressure and mortality (18).…”