NONINVASIVE VENTILATION IMPROVES COPD EXACERBATION OUTCOMES

Patients with chronic obstructive pulmonary disease (COPD) exacerbations who are treated with noninvasive ventilation (NIV) may live longer than patients who receive standard forms of ventilation, results of a recent study have shown. Plant et al also demonstrated that it is possible to stratify patients in terms of their need for intubation by observing initial pH and arterial carbon dioxide tension (PaCO2).

Included in the multicenter, prospective, randomized, controlled study were 118 patients assigned to standard treatment and 118 patients given NIV. All subjects had experienced acute exacerbations of COPD. Arterial blood gas levels and respiratory rate were recorded in all patients at enrollment, after one hour, and after four hours. Patients were then observed for the primary end point (need for intubation), which occurred in 32 (27%) of the patients given standard treatment and in 18 (15%) of those receiving NIV. Such a need was assumed to exist if, within 14 days of admission, a patient had a pH below 7.20, a pH between 7.20 and 7.25 on two occasions one hour apart, hypercapnic coma, an arterial oxygen tension below 6 kPa despite a maximum tolerated fraction of inspired oxygen, or cardiorespiratory arrest.

Patients with the highest PaCO2 levels and worst acidosis were the most likely to meet criteria for intubation later on, although acidosis was the more significant indicator. NIV lowered not only the risk of needing intubation but also in-hospital mortality (10% vs 20% in those given standard treatment). Furthermore, median survival was longer in the NIV group than in those given standard treatment (16.8 vs 13.4 months, respectively).

Plant PK, Owen JL, Elliott MW. Non-invasive ventilation in acute exacerbations of chronic obstructive pulmonary disease: long term survival and predictors of in-hospital outcome. Thorax. 2001;56: 708-712.

EXCERCISE TESTING ASSESSES PRIMARY PULMONARY HYPERTENSION SEVERITY

Patients who have primary pulmonary hypertension (PPH) can safely undergo noninvasive cardiopulmonary exercise testing. This would allow physicians to understand the severity of each patient’s exercise limitations, quantify hypoperfusion of the lung and systemic circulation, and assess responses to therapy before right-ventricular failure and pulmonary hypertension become apparent while the patient is at rest.

Sun et al performed a retrospective analysis of 53 patients who underwent echocardiography, right-heart catheterization, and cardiopulmonary exercise testing. The researchers sought to relate abnormalities in aerobic function and ventilatory efficiency to traditional measurements of PPH, such as resting hemodynamics and New York Heart Association (NYHA) symptom class.

All patients had resting pulmonary hypertension; mean pulmonary artery pressure was 64 mm Hg. Most patients were in NYHA class 3. All patients completed the exercise testing without complications. Consistent findings included reductions in peak oxygen consumption (VO2), anaerobic threshold, peak oxygen pulse, rate of VO2 increase, and ventilatory efficiency. Measurements of aerobic function and gas exchange efficiency obtained during exercise testing correlated well with the patients’ NYHA symptom classes.

The authors stated that cardiopulmonary exercise testing can be used to evaluate patients with fatigue and dyspnea in a safe, reproducible, and noninvasive manner. They suggested that it might help in establishing a prognosis for patients with PPH; it could also be used to evaluate drug therapies or to prioritize patients for lung transplantation.

Sun X, Hansen J, Oudiz R, Wasserman K. Exercise pathophysiology in patients with primary pulmonary hypertension. Circulation. 2001;104:429-435.

BEDSIDE ASSESSMENT AND HEART FAILURE PROGNOSIS

Finding elevated jugular venous pressure and a third heart sound through physical examination of patients with heart failure may provide important prognostic information. These indicators are independently associated with such adverse outcomes as increased risk for and progression of heart failure, as well as risk for death from heart failure. This suggests that physicians should maintain the cardiac auscultatory skills that would enable them to detect these signs.

A retrospective analysis of data from the Studies of Left Ventricular Dysfunction (SOLVD) trial, which was originally designed to investigate the efficacy of enalapril for heart failure, shed new light on these two markers of cardiac morbidity. The SOLVD trial included 2,569 patients with symptomatic congestive heart failure and left ventricular dysfunction. The presence of elevated jugular venous pressure, a third heart sound, or both was noted at trial entry. Patients were randomized to receive either enalapril or placebo and were then followed for an average of 32 months.

Elevated jugular venous pressure could be detected in 280 patients, and a third heart sound could be heard in 597; both signs were present in 171 patients. Multivariate analysis adjusted for other markers of heart failure severity revealed that patients with one or both of these findings were at increased risk of death from all causes, hospitalization for heart failure, the composite outcome of death or hospitalization for heart failure, and death from pump failure. They were not at higher risk for death from arrhythmia. The strong connections between the aforementioned signs and these outcomes reinforced the investigators’ belief that bedside assessment is a clinically meaningful skill that needs to be maintained.

Drazner MH, Rame JE, Stevenson LW, et al. Prognostic importance of elevated jugular venous pressure and a third heart sound in patients with heart failure. N Engl J Med. 2001;345:574-581.

GUIDELINES DO NOT PREDICT PEDIATRIC PNEUMONIA

A set of guidelines established in Canada in 1997 suggested that pneumonia can be excluded in young children if respiratory distress, tachypnea, crackles, and decreased breath sounds are absent. An observational study conducted by Rothrock et al has disproved this conclusion.

In this four-month study, 329 children admitted to one urban emergency department were eligible for evaluation. All were five years or younger. Chest films were used to evaluate patients for pneumonia, with the final diagnosis being made when senior board-certified radiologists interpreted films and confirmed the presence of pneumonia or an infiltrate. Isolated atelectasis, pleural effusion, or elevated hemidiaphragm were not included in the diagnosis of pneumonia.

Researchers found that 67 of the 329 children (20%) had pneumonia. The 1997 guidelines demonstrated only 45% sensitivity and 66% specificity for the disease. Positive and negative predictive values were 25% and 82%, respectively.

One problem cited as a reason for the guidelines’ poor predictive value was variations in the definition of tachypnea used in previous studies, which could range from 40 to 59 breaths per minute. Rothrock and coworkers also suggested that high interobserver variability has clouded the definition of respiratory distress and rales, making unreliable any guidelines incorporating these as diagnostic criteria for pneumonia. Before guidelines are made available for clinical use, the authors concluded, they should be prospectively evaluated in clinical settings, must comprise reproducible criteria, and must minimize interobserver variability.

Rothrock S, Green S, Fanelli JM et al. Do published guidelines predict pneumonia in children presenting to an urban ED? Pediatr Emerg Care. 2001;17: 240-243.

WASTING PREDICTS CF OUTCOMES

Body wasting has been found to be a significant predictor of survival for patients with cystic fibrosis (CF). Independent of lung function and of arterial oxygen tension (Pao2) and carbon dioxide tension (Paco2), this measurement reliably predicted outcome for at least five years.

Sharma et al studied 584 CF patients with a mean age of 21 years. Forced expiratory volume in one second (FEV1) averaged 26% of predicted. Pao2 and Paco2 averaged 9.8 and 5.0 kPa, respectively, and average body weight was 92% of ideal. Neither patients’ age nor sex was predictive of outcome after five years. However, patients’ weight was predictive: 83% of subjects weighing more than 85% of ideal survived past five years, compared with 54.3% of those who weighed 85% of ideal or less. Additionally, patients with FEV1 greater than 30% of predicted had significantly better outcomes than did those whose FEV1 was 30% or less. Neither Pao2 nor Paco2 was found to accurately predict survival.

Probability of death increased most dramatically as body weight fell. The researchers stated that the development of cachexia in CF patients should be considered a serious warning sign. They recommend that cachexic patients be considered for lung or heart-lung transplantation earlier than patients with normal nutritional status. Delaying transplant surgery to improve nutritional status first would not have a positive result, they said; previous work has demonstrated that preoperative body mass does not influence survival after surgery.

Sharma R, Florea VG, Bolger AP, et al. Wasting as an independent predictor of mortality in patients with cystic fibrosis. Thorax. 2001;56:746-750.