American journal of respiratory and critical care medicine
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Am. J. Respir. Crit. Care Med. · Sep 1995
Reference values of arterial oxygen tension in the middle-aged and elderly.
The lack of available reference values of arterial PO2, particularly for elderly persons, led us to study a sample of 194 normal nonsmoking subjects, equally distributed over all age ranges from 40 to 90 yr. The radial artery was punctured and blood samples were taken and analyzed on an automated, computerized gas-analyzer. The trend of the mean values of PaO2 in the 5-yr class intervals of age showed a clear decline up to the 70- to 74-yr class, and then an inversion. ⋯ PaCO2); R2 = 0.28; SEE = 7.48; p < 0.0001. For subjects > or = 75 yr old, for whom there was no correlation with age, BMI, or PaCO2, only the mean +/- SD and 5th percentile of PaO2 were reported (83.4 +/- 9.15 mm Hg and 68.4 mm Hg, respectively). PaCO2 values were not correlated with either age or BMI; the mean +/- SD was 35.79 +/- 3.87 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)
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Am. J. Respir. Crit. Care Med. · Sep 1995
Case ReportsEvolution of rifampin resistance in human immunodeficiency virus-associated tuberculosis.
Acquired rifampin resistance without preexisting isoniazid resistance is highly unusual in patients with tuberculosis. The purpose of this report is to describe and characterize that unusual pattern of acquired drug resistance in three patients with human immunodeficiency virus (HIV) infection. The patients originally had Mycobacterium tuberculosis strains that were susceptible to isoniazid and rifampin. ⋯ One patient subsequently developed isoniazid resistance also. Studies on patients' M. tuberculosis isolates using IS6110 restriction fragment length polymorphism typing and rpoB gene sequencing indicated that rifampin resistance in each patient arose during therapy by an rpoB gene mutation in the original M. tuberculosis isolate. Detection of this unusual drug-resistance phenotype in three patients with HIV infection suggests that acquired rifampin resistance is somehow associated with co-infection due to HIV and tuberculosis.
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Am. J. Respir. Crit. Care Med. · Sep 1995
Randomized Controlled Trial Clinical TrialPostoperative physical therapy after coronary artery bypass surgery.
Coronary artery bypass surgery is frequently complicated by postoperative atelectasis. Although routinely prescribed, the efficacy of any specific chest physical therapy is not well established. We studied patients at a university center undergoing elective coronary artery bypass surgery. ⋯ We conclude that postoperative respiratory dysfunction is common but does not commonly cause significant morbidity or prolong hospital stay. Adding SMI to patients with minimal atelectasis at extubation does not improve clinical outcomes. Similarly, adding SSP to patients with marked atelectasis does not improve outcomes over those obtained with SMI and early ambulation.
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Am. J. Respir. Crit. Care Med. · Sep 1995
Tidal volume maintenance during weaning with pressure support.
Ventilation was measured in 31 difficult-to-wean patients while pressure support (PS) was reduced by 5 cm H2O every 20 min. Weaning had to be aborted in 14 of 31 patients (Group F) because they met predefined distress criteria. The remaining 17 patients who were able to complete the "weaning test" (Group S) had larger static respiratory compliances (Cstat = 0.08 +/- 0.02 versus 0.05 +/- 0.01 L/cm H2O, p < or = 0.05) and a lower dead space to tidal volume ratio (0.55 +/- 0.05 versus 0.64 +/- 0.06, p < or = 0.05). ⋯ In contrast, Group F patients defended VT at higher PS settings but were unable to maintain VT during distress. Ventilatory response parameters such as the rapid shallow breathing index were of limited value in predicting weaning outcome and yielded receiver operator curve area values between 0.66 and 0.82 over the range of PS settings tested. We conclude that the gradual withdrawal of machine support does not facilitate the recognition of impending respiratory failure.
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Am. J. Respir. Crit. Care Med. · Aug 1995
Efficacy of expiratory tracheal gas insufflation in a canine model of lung injury.
Tracheal gas insufflation (TGI) improves the efficiency of CO2 elimination by reducing the CO2-laden dead space of the airways. The effect of TGI on PaCO2 diminishes in the setting of acute lung injury (ALI) because an increased alveolar component dominates the total physiologic dead space. Nevertheless, adopting a strategy of permissive hypercapnia should partially offset the decreased efficacy of TGI by increasing CO2 concentration in the proximal airways. ⋯ The corresponding decrements in PaCO2 produced by TGI at a flow rate of 10 L/min were 16 +/- 3, 24 +/- 10, and 10 +/- 2 mm Hg, respectively. TGI decreased total physiologic dead space per breath (VD) by 56, 31, and 28 ml during the pre-OAI, post-OAI, and post-OA/VT stages, respectively. Despite a smaller reduction in VD during the post-OAI stage, the effect of TGI on PaCO2 was preserved because of the relatively high PaCO2 prior to its initiation.(ABSTRACT TRUNCATED AT 250 WORDS)