Response to symptom-limited exercise in patients with the hepatopulmonary syndrome.

OBJECTIVE: To study the response to symptom-limited exercise in patients with the hepatopulmonary syndrome (HPS). DESIGN: The response to maximal cardiopulmonary exercise (CPX) was studied in 5 patients with HPS and compared with 10 case control (normoxemic, NC) cirrhotics (matched for age, gender, etiology and severity of liver disease, tobacco use, and beta-blocker therapy) and 9 hypoxemic control cirrhotics (HC) without clinical evidence of HPS. SETTING: Cardiopulmonary exercise physiology laboratory in a tertiary care referral center. PATIENTS: Cirrhotics referred for CPX as part of their preliver transplantation evaluation. MEASUREMENTS: Standard pulmonary function tests and echocardiography were performed to assess resting pulmonary and cardiac function. Peak oxygen consumption (VO2), minute ventilation, arterial blood gases, and dead space (VD/VT) were determined during symptom-limited maximal CPX. RESULTS: Resting spirometry and lung volumes were similar between HPS and NC subjects, while HC subjects had restrictive physiology. Differences existed in diffusing capacity corrected for hemoglobin and alveolar volume percent predicted (HPS, 45+/-2 vs NC, 68+/-3, p<0.05; vs HC, 70+/-4, p<0.05), PaO2 (HPS, 70+/-5 mm Hg; HC, 79+/-3 mm Hg, vs NC, 102+/-3 mm Hg, p<0.05) and alveolar-arterial (A-a) O2 gradient (HPS, 42+/-8 mm Hg vs HC, 27+/-2 mm Hg, p<0.05; vs NC, 6+/-2 mm Hg, p<0.05). During CPX, HPS patients achieved a lower peak VO2 percent predicted (HPS, 55+/-6 vs NC, 73+/-3, p<0.05; vs HC, 71+/-5, p<0.05) and VO2 at the ventilatory threshold as percent predicted peak VO2 (HPS, 36+/-2 vs NC, 55+/-4, p<0.05; vs HC 55+/-5, p<0.05). While no differences existed in heart rate and breathing reserve, HPS patients had significantly lower PaO2 (HPS, 50+/-5 mm Hg vs NC, 97+/-4 mm Hg, p<0.05; vs HC, 87+/-6 mm Hg, p<0.05), wider A-a O2 gradient (HPS, 73+/-5 mm Hg vs NC, 13+/-3 mm Hg, p<0.05; vs HC, 31+/-5 mm Hg, p<0.05) and higher VD/VT (HPS, 0.36+/-.03 vs NC, 0.18+/-.02, p<0.05; vs HC, 0.28+/-.02, p<0.05) at peak exercise. For HPS patients, VO2 was negatively correlated with VD/VT (r2=0.9) and positively correlated with PaO2 (r2=0.41) at peak exercise. CONCLUSIONS: Patients with HPS demonstrate a severe reduction in aerobic capacity, beyond that found in cirrhotics without syndrome. The significant hypoxemia and elevated VD/VT at peak exercise suggest that an abnormal pulmonary circulation contributes to further exercise limitation in patients with HPS.

Analysis of impaired exercise capacity in patients with cirrhosis.

Exercise limitation in cirrhosis is typically attributed to a cirrhotic myopathy (without impaired oxygen utilization) and/or a cardiac chronotropic dysfunction. We performed symptom-limited cardiopulmonary exercise testing in 19 cirrhotics without confounding variables (cardiopulmonary disease, beta blockade, anemia, smoking). Twelve concurrently exercised patients without cirrhosis and with normal resting pulmonary function were controls. Oxygen consumption (VO2) at peak exercise, at anaerobic threshold (VO2-AT), work rate (WR), and heart rate (HR) were measured. Cirrhotics had significantly lower peak WR (73+/-4 vs 107+/-7% predicted, p < 0.001), VO2 (72+/-4 vs 98+/-5% predicted, P < 0.001), VO2-AT (53+/-4 vs 71+/-5% predicted peak VO2, P < 0.01), HR (83+/-2 vs 91+/-2% predicted, P < 0.01) and were more likely to have chronotropic dysfunction (peak HR < 85% predicted). Six cirrhotics had normal aerobic capacity (peak VO2 > 80% predicted), while 13 were abnormal. The abnormals had an earlier AT (46+/-2 vs 67+/-3% predicted peak VO2, P < 0.05) but no difference in peak HR percent predicted was found. In conclusion, two thirds of cirrhotics, without confounding factors, have significantly reduced aerobic capacity. Cirrhotic myopathy (without impaired O2 utilization) and cardiac chronotropic dysfunction do not adequately account for the observed decrease in aerobic capacity.

Independent effects of etiology of failure and time to reintubation on outcome for patients failing extubation.

Patients requiring reintubation after failed extubation have a poor prognosis, with hospital mortality exceeding 30 to 40%, though the reason remains unclear. To examine the impact of etiology of extubation failure and time to reintubation on hospital outcome, we performed a post hoc analysis of prospectively gathered data on 74 MICU patients (47 men, 27 women), 64 +/- 2 yr of age who required reintubation within 72 h of extubation. Cause for reintubation was classified as airway (upper airway obstruction, 11; aspiration/excess pulmonary secretions, 12) or nonairway (respiratory failure, 21; congestive heart failure, 17; encephalopathy, 7; other, 6). The duration of mechanical ventilation prior to extubation was 139 +/- 19 h, and the median time to reintubation was 21 h. Thirty-one of 74 patients (42%) died, with mortality highest for patients failing from nonairway etiologies (27/51, 53% versus 4/23, 17%; p < 0.01). Patients failing from an airway cause tended to be reintubated earlier (21 +/- 4 versus 31 +/- 3 h, p = 0.07). Mortality increased with longer duration of time from extubation to reintubation (<= 12 h, 6/25 versus > 12 h, 25/49; p < 0.05). With multiple logistic regression, both cause for extubation failure and time to reintubation were independently associated with hospital mortality. In conclusion, etiology of extubation failure and time to reintubation are independent predictors of outcome in reintubated MICU patients. The high mortality for those reintubated for nonairway problems indicate that efforts should be preferentially focused on identifying these patients. The effect of time to reintubation suggests that identification of patients early after extubation and timely reinstitution of ventilatory support has the potential to reduce the increased mortality associated with extubation failure.

Effect of failed extubation on the outcome of mechanical ventilation.

OBJECTIVE: To examine medical outcomes associated with reintubation for extubation failure after discontinuation of mechanical ventilation. DESIGN: Prospective cohort study of consecutive intubated medical ICU patients who underwent a trial of extubation at a tertiary-care teaching hospital. The failed extubation group consisted of all patients reintubated within 72 h or within 7 days (if continuous ICU care had been required) of extubation. All others were considered to be successfully extubated. Study end points included hospital death vs survival, the number of days spent in the ICU and in the hospital after the onset of mechanical ventilation, the likelihood of requiring > or = 7 or > or = 14 days of ICU care after extubation, and the need for transfer to either a long-term care or rehabilitation facility among the survivors. RESULTS: Of 289 intubated patients, 247 (85%) were successfully extubated, and 42 (15%) required reintubation for failed extubation (time to reintubation 1.5+/-0.2 days). Reintubation for extubation failure resulted in 12 additional days of mechanical ventilation. When compared with successfully extubated patients, reintubated patients were more likely to die in the hospital (43% vs 12%; p<0.0001), spend more time in the ICU (21.2+/-2.8 days vs 4.5+/-0.6 days; p<0.001) and in the hospital (30.5+/-3.3 days vs 16.3+/-1.2 days; p<0.001) after extubation, and require transfer to a long-term care or rehabilitation facility (38% vs 21%; p<0.05). Using multiple logistic regression, extubation failure was an independent predictor for death and the need for transfer to a long-term care facility. Compared with those successfully extubated, patients who failed extubation were seven times (p<0.0001) more likely to die, 31 times (p<0.0001) more likely to spend > or = 14 days in the ICU after extubation, and six times (p<0.001) more likely to need transfer to a long-term care or rehabilitation facility if they survived. CONCLUSION: After adjusting for severity of illness and comorbid conditions, extubation failure had a significant independent association with increased risk for death, prolonged ICU stay, and transfer to a long-term care or rehabilitation facility. Extubation failure may serve as an additional independent marker of severity of illness. Alternatively, poor outcomes may be etiologically related to extubation failure. If the latter proves to be the case, identifying patients at risk for poor outcomes from extubation failure and instituting alternative care practices may reduce mortality, duration of ICU stay, and need for transfer to a long-term care facility.

Influence of gender and endotracheal tube size on preextubation breathing pattern.

An imbalance between work of breathing and respiratory muscle capacity often results in rapid, shallow breathing (increased respiratory rate/tidal volume [f/VT]). Because this imbalance commonly causes unsuccessful weaning from mechanical ventilation, it is not surprising that an elevated f/VT accurately predicts weaning failure. However, while studying extubation outcome, we observed that women and patients with narrow endotracheal tubes are often successfully extubated with an elevated f/VT. We studied 218 medical patients in the intensive care unit who had a f/VT measured through an oral endotracheal tube (off of ventilatory support) during 1 min of spontaneous respiration at the onset of a weaning trial that culminated in extubation. Men and women were comparable at the onset of mechanical ventilation and weaning trials in severity of illness, etiology of respiratory failure, ventilator settings, and gas exchange data. Women were found to have a higher f/VT (79 +/- 5 versus 56 +/- 3 breaths/L, p < 0.001), lower tidal volumes (381 +/- 14 versus 494 +/- 13 ml, p < 0.001), and higher respiratory rate 26 +/- 1 versus 24 +/- 1, p < 0.05). The differences persisted after controlling for extubation outcome. Smaller endotracheal tubes were associated with a higher f/VT, especially for women (< or = 7 mm, 86 +/- 6 versus > 7 mm, 68 +/- 6, p < 0.05). Women were more likely to have a f/VT > or = 100 (19/82 [women] versus 10/136 [men], p < 0.001). Although the overall incidence of extubation failure was similar (11/82 [women] versus 23/136 [men], p = NS), among patients with f/VT > or = 100, men were more likely to require reintubation (3/19 [women] versus 5/10 [men], p = 0.08). We conclude that women, especially when breathing through small endotracheal tubes, have a higher f/VT (including likelihood of f/VT > or = 100) than men, independent of extubation outcome. Consideration of factors that elevate the f/VT, unrelated to physiologic work of breathing and respiratory muscle capacity, should improve application of this index to extubation decision making.