The effect of heliox in acute severe asthma: a randomized controlled trial.

STUDY OBJECTIVES: To evaluate the effect of heliox on airflow obstruction and dyspnea in patients with acute severe asthma. DESIGN: A prospective, randomized, controlled study. SETTING: A university hospital. PATIENTS: Twenty-three patients presenting to the emergency department with acute severe asthma were randomized to receive 70%/30% heliox or 30% oxygen. MEASUREMENTS: Peak expiratory flow (PEF), dyspnea score, heart rate, respiratory rate (RR), and BP were measured at baseline and 20, 120, 240, 360, and 480 min after starting the test gas. After baseline, the PEF was measured by using the gas that was randomized to the treatment program. RESULTS: In the first 20 min, there was a 58.4% increase in percent predicted PEF (%PEF) in the heliox group (p<0.001), whereas there was only a 10.1% increase in %PEF for the oxygen group (p>0.1). Eighty-two percent of the heliox group had >25% improvement in %PEF at 20 min, whereas only 17% of the oxygen group did (p<0.01). The next significant improvement in %PEF in the heliox group occurred at 480 min. At the end of the study in the heliox group, the PEF did not significantly (p>0.1) change immediately after the heliox was discontinued (270.6 to 264.2 L/min). In the heliox group in the first 20 min, there was a significant decrease in dyspnea score and RR (p<0.05), but there were no further significant improvements for the rest of the study. In the oxygen group, no variables significantly improved until 360 min. CONCLUSION: Heliox rapidly improves airflow obstruction and dyspnea in patients with acute severe asthma and may be useful as a therapeutic bridge until the corticosteroid effect occurs.

Rapid-eye-movement-specific sleep-disordered breathing: a possible cause of excessive daytime sleepiness.

Some patients referred for polysomnography with complaints of excessive daytime sleepiness (EDS) and clinically suspected obstructive sleep apnea (OSA) have a respiratory disturbance index (RDI) < 10. Many would consider these patients not to have OSA. We reviewed 34 such patients to determine whether respiratory disturbances confined primarily to rapid eye movement (REM) sleep correlated with an objective criterion for EDS: a mean sleep latency (MSL) < 10 min. REM-specific events were quantified with indices calculated for REM sleep alone. Univariate linear regression showed that a REM-specific respiratory disturbance index (REM-RDI) and the transient arousal index (TAI) computed for REM sleep (REM-TAI) were associated with a low MSL (R2 = -0.35, p = 0.001; and R2 = -0.27, p = 0.01, respectively). In our subjectively sleepy patients with an overall RDI < 10, a REM-RDI > or = 15 had the highest predictive accuracy (82%) for an MSL < 10 min. Seventeen of the 34 study patients had a REM-RDI > or = 15. Their mean MSL was 8.3 +/- 0.8 min. We conclude that within a group of patients with daytime sleepiness, suspected OSA, and a normal RDI, there may be a subset who have clinically significant REM-specific sleep-disordered breathing.

Heliox therapy in acute severe asthma.

STUDY OBJECTIVE: To assess how patients with respiratory acidosis from acute severe asthma respond to helium-oxygen (heliox) mixtures. DESIGN: Consecutive case series. SETTING: Urban community teaching hospital. PATIENTS: Over a 2-year period, 12 asthmatics (mean age, 33.8 +/- 11.3 years) presented to the emergency department with acute respiratory acidosis (pH < 7.35 and PaCO2 > or = 45 mm Hg). All 12 patients were treated with heliox (60 to 70% helium/30 to 40% oxygen). Five patients received heliox through a ventilator and seven received heliox via face mask. RESULTS: Arterial blood gases (ABGs) were drawn immediately before and at a mean of 49.2 +/- 25.2 min after beginning heliox therapy. No therapeutic interventions were made between ABGs. For the entire group, the mean PaCO2 decreased from 57.9 to 47.5 mm Hg (p < 0.005) and the arterial pH increased from 7.23 to 7.32 (p < 0.001). In an attempt to find characteristics that might predict the response to heliox, a clinically significant response to heliox was defined as a drop in PaCO2 (to normal or by > or = 15%) coupled with a rise in pH by > or = 0.05. Using this definition, there were eight responders (67%) and four nonresponders (33%). The responders had a shorter duration of symptoms (17.8 vs 78.0 h, p < 0.05) and a lower preheliox pH (7.20 vs 7.30, p < 0.05). All of the responders presented within 24 h of symptom onset. Three of the four nonresponders reported prolonged (> or = 96 h) duration of symptoms, and two eventually required intubation. CONCLUSION: Heliox can rapidly improve ventilation in patients presenting to an emergency department with acute severe asthma with respiratory acidosis and a short duration of symptoms.

Intensive care unit outcome in the very elderly.

OBJECTIVES: To determine if age, previous functional status, or acute severity of illness affect the acute and long-term mortality rates and functional status of the very elderly (> or = 85 yrs) after an ICU admission. DESIGN: Cohort study (retrospective entry for the first year of the study and prospective entry thereafter with prospective follow-up throughout). SETTING: An ICU in a community teaching hospital with follow-up at home or at a skilled nursing facility. PATIENTS: All (n = 105) patients > or = 85 yrs admitted to the ICU over a 2-yr period. MAIN OUTCOME MEASURES: ICU, 30-day posthospital discharge, and 1-yr mortality rates, activities of daily living scores, organ system failure score at the time of ICU admission. RESULTS: The ICU, 30-day posthospital discharge, and the 1-yr mortality rates were 30%, 43%, and 64%, respectively. Mortality rates significantly increased between the ICU stay or 30 days posthospital discharge and 1-yr follow-up periods. Of those patients who lived up to 6 months after hospital discharge, 86% survived to 1 yr with little change in functional status from baseline. In the patients with > or = 2 organ system failures, there were 88% 30-day posthospital discharge and 100% 1-yr mortality rates. Severity of illness, as measured by the number of organ system failures, was associated with increased ICU (odds ratio 3.38; 95% confidence interval, 1.51 to 7.60; p < .005) and 1 yr (odds ratio 5.76; 95% confidence interval, 2.49 to 13.29; p < .0001) mortality rates, while age within this group and preadmission functional status were not. CONCLUSIONS: Within the very elderly population, acute severity of illness is the most significant predictor of mortality after an ICU admission. For most very elderly patients, surviving 1 yr after an ICU admission, there is little change in functional status.

Adjustment of DLCO for varying COHb, and alveolar PO2 using a theoretical adjustment equation.

The diffusing capacity of the lung for carbon monoxide (DL) is affected by changes in alveolar partial pressure of oxygen (PAO2), hemoglobin concentration (Hb), and carboxyhemoglobin concentration (COHb). A number of investigators have derived empiric adjustment equations to account for changes in these variables. We evaluated an adjustment of DL for changes in COHb and PAO2 using a single equation derived from Roughton and Forster's original definitions (J. Appl. Physiol., 1957). Unadjusted DL values declined significantly with rising COHb (-0.938%/percent COHb increase, P less than 0.0001) and rising PAO2 (-0.343%/mm Hg PAO2 increase, P less than 0.0001). Adjusted measured DL using the derived equation showed no significant change with changing COHb and PAO2 levels and provides an acceptable method for adjustment of DL for the effects of varying COHb and PAO2 levels from the standard conditions of COHb% = 0, and PAO2 = 110 mm Hg. Since a similar equation has previously been used to adjust for changes in DL due to anemia, we propose to use a single equation which is theoretically derived and empirically verified to adjust DL measurements for changes in COHb, PAO2 and hemoglobin.