Non-invasive pressure support ventilation in severe community-acquired pneumonia
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Objective: To explore three aspects of non-invasive pressure support ventilation (NIPSV) applied by face mask to patients with acute respiratory failure (ARF) due to severe community-acquired pneumonia (CAP): (1) the initial acute effects on respiratory rate, gas exchange and hemodynamics, (2) the clinical course and outcome during ICU and hospital stay, (3) the nursing workload as measured by the daily PRN 87 (Project Research in Nursing) score. Setting: Medical ICU, University Hospital. Design: Prospective, observational study. Patients: Patients without any prior history of chronic lung disease, consecutively admitted to the ICU to receive NIPSV for ARF due to severe CAP. Measurements and results (means ± SD): Twenty-four patients aged 49±17 years, admission APACHE II 13±5, were included. Admission PaO2/FIO2, alveolar-arterial oxygen difference (DA-aO2) and PaCO2 were 104±48, 447±120 and 40±10 mmHg, respectively. All patients were normotensive. During the initial NIPSV trial respiratory rate decreased from 34±8 to 28±10 breaths/min (p<0.001) and arterial oxygenation improved (PaO2/FIO2 104±48 vs 153±49, DA-aO2 447±120 vs 370±180 mmHg, p<0.001) while PaCO2 remained unchanged. There were no hemodynamic effects. Subsequently, a total of 133 NIPSV trials were performed (median duration 55 min, range 30–540 min) over 1–7 days. No complication occurred during NIPSV. Sixteen patients were intubated (66%) 1.3±1 days after inclusion. Upon inclusion, the patients who were subsequently intubated were older (55±15 vs 37±12 years) and more severely hypoxemic (63±11 vs 80±15 mmHg, p<0.05) than those not requiring intubation. Eight patients died (33%), all in the intubated group. Median lengths of stay in the ICU and hospital were longer in intubated patients (ICU 16 days, range 3–64 vs 6 days, range 3–7, p<0.05; hospital 23 days, range 9–77 vs 9.5 days, range 4–42, p<0.05). Mean daily total PRN points were stable throughout the NIPSV period and were not different between the groups. Only 14% of PRN points resulted from respiratory therapy interventions. PRN score was higher during the first 24 h following intubation than during the first 24 h of NIPSV (278±55 vs 228±24 points, p<0.05). Conclusion: Despite initial improvement in arterial oxygenation with NIPSV in patients with ARF due to severe CAP, the intubation rate is high. However, the more favorable outcome and shorter ICU and hospital stays when intubation is avoided, as well as the short delay required to assess the success or failure of NIPSV warrants a trial of NIPSV in this setting. The nursing workload remains stable during NIPSV and does not result predominantly from respiratory therapy interventions.
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