Effect of acetazolamide on post-NIV metabolic alkalosis in acute exacerbated COPD patients.

OBJECTIVE: Non-invasive ventilation (NIV) is an effective treatment in patients with acute exacerbation of COPD (AECOPD). However, it may induce post-hypercapnic metabolic alkalosis (MA). This study aims to evaluate the effect of acetazolamide (ACET) in AECOPD patients treated with NIV. PATIENTS AND METHODS: Eleven AECOPD patients, with hypercapnic respiratory failure and MA following NIV, were treated with ACET 500 mg for two consecutive days and compared to a matched control group. Patients and controls were non invasively ventilated in a bilevel positive airway pressure (BiPAP) mode to a standard maximal pressure target of 15-20 cmH2O. RESULTS: ACET intra-group analysis showed a significant improvement for PaCO2 (63.9 ± 9.8 vs. 54.9 ± 8.3 mmHg), HCO3- (43.5 ± 5.9 vs. 36.1 ± 5.4 mmol/L) and both arterial pH (7.46 ± 0.06 vs. 7.41 ± 0.06) and urinary pH (6.94 ± 0.77 vs 5.80 ± 0.82), already at day 1. No significant changes in endpoints considered were observed in the control group at any time-point. Inter-group analysis showed significant differences between changes in PaCO2 and HCO3- (delta), both at day 1 and 2. Furthermore, the length of NIV treatment was significantly reduced in the ACET group compared to controls (6 ± 8 vs. 19 ± 19 days). No adverse events were recorded in the ACET and control groups. CONCLUSIONS: ACET appears to be effective and safe in AECOPD patients with post-NIV MA.

Exercise intolerance at high altitude (5050 m): critical power and W'.

The relationship between work rate (WR) and its tolerable duration (t(LIM)) has not been investigated at high altitude (HA). At HA (5050 m) and at sea level (SL), six subjects therefore performed symptom-limited cycle-ergometry: an incremental test (IET) and three constant-WR tests (% of IET WR(max), HA and SL respectively: WR(1) 70±8%, 74±7%; WR(2) 86±14%, 88±10%; WR(3) 105±13%, 104±9%). The power asymptote (CP) and curvature constant (W') of the hyperbolic WR-t(LIM) relationship were reduced at HA compared to SL (CP: 81±21 vs. 123±38 W; W': 7.2±2.9 vs. 13.1±4.3 kJ). HA breathing reserve (estimated maximum voluntary ventilation minus end-exercise ventilation) was also compromised (WR(1): 25±25 vs. 50±18 l min(-1); WR(2): 4±23 vs. 38±23 l min(-1); WR(3): -3±18 vs. 32±24 l min(-1)) with near-maximal dyspnea levels (Borg) (WR(1): 7.2±1.2 vs. 4.8±1.3; WR(2): 8.8±0.8 vs. 5.3±1.2; WR(3): 9.3±1.0 vs. 5.3±1.5). The CP reduction is consistent with a reduced O(2) availability; that of W' with reduced muscle-venous O(2) storage, exacerbated by ventilatory limitation and dyspnea.

Cardiopulmonary exercise testing in the functional and prognostic evaluation of patients with pulmonary diseases.

Exercise testing is increasingly utilized to evaluate the level of exercise intolerance in patients with lung and heart diseases. Cardiopulmonary exercise testing (CPET) is considered the gold standard to study a patient's level of exercise limitation and its causes. The 2 CPET protocols most frequently used in the clinical setting are the maximal incremental and the constant work rate tests. The aim of this review is to focus on the main respiratory diseases for which exercise tolerance is indicated; for example, chronic obstructive pulmonary disease, interstitial lung disease, primary pulmonary hypertension and cystic fibrosis. This review also focuses on the variables/indices that are utilized in the functional and prognostic evaluation. The recognition of abnormal response patterns of ventilatory, cardiac and metabolic limitation to exercise may help in the diagnostic evaluation. In addition, CPET indexes can provide important functional and prognostic information regarding patients with pulmonary disease. Exercise indices, such as peak oxygen uptake (V'O(2 peak)), ventilatory equivalents for carbon dioxide production (V'(E)-/V'CO(2)) and arterial oxygen saturation (S(p)O(2)), have in fact proven to be better predictors of prognosis than lung function measurements obtained at rest. Moreover, useful information on the effects of therapeutic interventions may be obtained by CPET by studying the changes in endurance capacity during high-intensity constant work rate protocols.