A classic monitoring ICU system was in use in all patients; an indwelling arterial catheter was inserted into the radial artery for continuous recording of arterial blood pressure and frequent blood gas analysis, the Sa02 was continuously monitored via pulse oximeter, and the ECG and respiratory rate were continuously recorded by classic means.
A specialized nurse trained to initiate nasal mechanical ventilation in patients with chronic conditions (kyphoscoliosis, myopathy, etc) was in charge of the first 10 h of NPPV for all six patients with acute disorders. She then closely supervised the work of other ICU nurses (“random nurses”) accustomed to NPPV. During the entire NPPV period, a system was devised to record the amount of time spent by the nurse with her patients when they were submitted to NPPV. Neither the specialized nurse nor the “random nurses” were aware of the protocol or of these measurements.
The decision to stop NPPV because of improvement or worsening (ie, intubation) was made by the research team in NPPV and the clinical team, according to the following criteria: (1) improvement: marked clinical improvement, with disappearance of dyspnea without NPPV normalization of arterial blood gas levels, particularly P&CO, (<5.5 kP& [41 mm Hg]), and correction of the initial event that caused the need to ventilate the patient; or (2) worsening of the clinical situation, with persistent symptoms of respiratory’ failure or inspiratory muscle fatigue (respiratory frequency >35/min; paradoxic abdominothoracic breathing; heavy recruitment of accessory respiratory muscles; tachycardia >120/min; arterial hypertension; impossibility to tolerate NPPV for any reason), or persistent severe respiratory acidosis (pH <7.28).