Non-invasive Mechanical Ventilation in Status Asthmaticus

Objective: To evaluate our clinical experience with the use of non-invasive mechanical ventilation (NIMV) in patients with an acute asthmatic attack.

Design: Seven-year period retrospective observational study.

Setting: General intensive care department (ICU) of a county hospital.

Patients: From 1992 to 1998, we documented clinical data, gas exchange and outcome of every asthmatic patient admitted to our ICU because of status asthmaticus (SA) refractory to initial medical therapy.

Interventions: Clinical charts were reviewed and patients were allocated to two groups according to their suitability as participants in an NIMV trial. Patients who arrived in respiratory arrest and those who ultimately improved with medical management alone were not considered candidates for NIMV. For the present analysis, the rest of the patients were considered candidates for NIMV, while the decision to start a NIMV trial or to perform endotracheal intubation (ETI) remained at the discretion of the attending physician. When patients failed to improve with NIMV, standard mechanical ventilation (MV) with ETI was initiated.

Measurements And Results: Fifty-eight patients were included in the study. Twenty-five patients (43%) were not eligible for NIMV: 11 patients (19%) because of respiratory arrest on their arrival at the Emergency Room and 14 patients (24%) because of improvement with medical management (bronchodilators, corticoids and oxygen). The remaining 33 patients were eligible for NIMV (57%): 11 patients (33%) received invasive MV and 22 patients (67%) were treated with NIMV. Three NIMV patients (14%) needed ETI. We compared data at baseline, 30 min, 2-6 h and 6-12 h after the onset of ventilatory support. Significant differences were observed in arterial blood gases on admission to the Emergency Room between MV and NIMV: PaCO2 (89 +/- 29 mmHg vs 53 +/- 13 mmHg, p < 0.05), pH (7.05 +/- 0.21 vs 7.28 +/- 0.008, p < 0.05) and HCO3- level (22 +/- 5 mmol/l vs 26 +/- 6 mmol/l, p < 0.05). No differences were found in the median length of ICU stay (4.5 vs 3 days), median hospital stay (15 vs 12 days) and mortality (0 vs 4%).

Conclusion: Face mask NIMV appears to be a suitable method for improving alveolar ventilation and can reduce the need for intubation in a selected group of patients with SA.