Normocapnia following noninvasive ventilation in acute exacerbations and chronic state of obstructive pulmonary disease.

We attempted to decrease PCO2 during noninvasive ventilation (NIV) and studied he effects of this therapy both in acute exacerbations of chronic obstructive pulmonary disease (COPD) and in its chronic state. Ninety six patients (63% male) with COPD and hypercapnia above 6.7 kPa were investigated. The mode and setting of the ventilator had to be chosen to achieve normocapnia. The subgroup of acute exacerbated COPD was separated by pH (<7.35=acute), by HCO3- (<26 mmol/l=acute), and by history (acute=history of recent deterioration). Ventilator settings were the following: tidal volume-972+/-137 ml and frequency-20+/-2.2 (volume preset). Inspiratory pressure was 33.6+/-14.2 mbar and frequency-19.7+/-5.1 (pressure preset). The preference of volume preset ventilators resulted from insufficient maximal pressures of the pressure preset devices. Eighty three percent of the patients became normocapnic while on NIV after 6.8+/-5.7 days. The mean PCO2 decreased from 64+/-13 mmHg to 41+/-6 mmHg (P<0.001). After 4 weeks, 72% of the patients were normocapnic while breathing spontaneously (P<0.001). The subgroups of acute exacerbation were the following: pH 28%, HCO3- 3.1%, and history 68%. All three indicators together were present in 2% of patients. Normocapnia under ventilation and during spontaneous breathing was independent from the subgroup. In conclusion, the study showed that normocapnia can be achieved in COPD under the ventilator and while breathing spontaneously in chronic and acute disease.

Noninvasive ventilation during weaning.

Patients suffering from advanced chronic thoracic disorders are at higher risk to develop respiratory failure, requiring mechanical ventilation. Forty seven patients acutely decompensated were investigated. Twenty nine of them were primarily ventilated noninvasively, 7 were intubated and 11 had been intubated and tracheotomized prior to arriving at the weaning center. All intubated patients were transferred to noninvasive ventilation within 24 h after arrival. Ten of the 11 tracheotomizd patients were transferred to noninvasive ventilation before discharge. One remained tracheotomized because of severe tracheal stenosis, despite being able to breathe spontaneously for several hours. Mortality was 14.2% in the intubated, 9% in the tracheotomized, and 10.2% in the primarily nasally ventilated. One patient refused to go on with mechanical ventilation and died. Hospital stay ranged between 4 and 24 days in the nasally ventilated. The intubated were ventilated invasively between 3 and 16 days and thereafter 4 to 17 days noninvasively on a regular ward. Tracheotomized patients were treated in intensive care for 7 to 32 days and in the weaning unit for 7 to 39 days. We conclude that patients either ventilated nasally or intubated or tracheotomized can be prepared for home mechanical ventilation in a weaning unit with similar outcome. Noninvasive ventilation is highly important in such patients as only one remained on invasive ventilation. This may implicate that transfer to noninvasive ventilation prior to tracheotomy might be appropriate.