Efficacy of noninvasive nasal mechanical ventilation in acute respiratory failure: monitored by breathing patterns

Till a decade back, the mainstay delivery of mechanical ventilation to patients with acute respiratory failure was through the endotracheal tube. To obviate the various complications of endotracheal intubation, noninvasive mechanical ventilation (NIMV) techniques were devised which could be used outside the confines of an ICU setting, and have been employed by several workers to achieve a high success rate.

Twenty patients of acute respiratory failure (ARF) were treated with NIMV. The latter was delivered by assist control mode of ventilator and nasal CPAP mask. Improvement of the illness was monitored by serial ABG analysis and breathing pattern parameters over one week.

The application of NIMV was successful in reversing the illness in 17 patients (85%) and the other three patients had to be intubated. The pH rose from 7.267 +/- 0.087 at presentation to 7.411 +/- 0.032 (p < 0.00005), the PaCO2 dropped from 85.17 +/- 13.48 mmHg to 46.27 +/- 3.79 mmHg (p < 0.00005). The PaO2 improved from 52.36 +/- 11.14 mmHg to 63.60 +/- 7.55 mmHg (p < 0.005) on the seventh day. The respiratory rate (RR) decreased from 30.07 +/- 6.10 breaths/min to 22.05 +/- 4.05 breaths/min (p < 0.00005), the %RC (percent rib cage) also showed a significant reduction in rib cage contraction from 61.7 +/- 10.17 to 42.76 +/- 10.66 (p < 0.00005). A marked improvement during the initial four hours of application of NIMV was observed in all the 17 patients.

It was concluded that NIMV resulted in marked improvement in both the breathing pattern and blood gas parameters in patients of ARF; and PaCO2, pH, RR, %RC served as the best indicators of improvement. NIMV was observed to be most useful in those patients who had CO2 retention.