Noninvasive mechanical ventilation in acute respiratory failure.
Mechanical ventilation (MV) has been indicated in the treatment of acute respiratory failure (ARF) if conservative treatment fails. Invasive MV is associated to a variety of complications. The recent innovations of noninvasive methods of MV (NMV) avoid the complications of invasive MV, whilst ensuring a similar degree of efficacy. A review of the literature from 1989 to 1995 shows that use of NMV in ARF has been reported in several studies involving more than 400 patients most of them COPD. NMV was successful from 51 to 91%, the severity of ARF being widely different among the different studies. Most of the studies compared effectiveness of NMV with historical groups of patients treated with "conventional" medical therapy whilst controlled studies of NMV versus ET intubation are lacking. Type of mask, mode of ventilation, compliance to treatment, type of patient and severity of disease may influence the success rate. Success with NMV was associated with less severely abnormal baseline clinical and functional parameters and to less severe levels of acidosis assessed during an initial trial of NMV. Therefore, NMV may be useful in selected patients with ARF. Patients should have clinical and physiological evidence of ARF and should be sufficiently cooperative. It is commonly said that NMV should be avoided, and endotracheal (ET) intubation performed in patients with haemodynamic instability, uncontrolled arrhythmias, gastrointestinal bleeding, high risk for aspiration. With these limitations NMV in selected patients with ARF is well tolerated and may be useful in avoiding ET intubation in most cases of COPD and with a wide range of success rates in other disease. This in turn has several advantages in terms of avoiding complications of invasive MV, reducing the length of stay in ICU and probably the number of ICU readmissions. Side effects of NMV seem less severe than those induced by invasive MV. In conclusion in selected patients a trial of noninvasive mechanical ventilation, as an adjunct to medical therapy, should be instituted at an early stage of ARF episodes before severe acidosis ensures, to avoid ET intubation.