Ll. Blanch

Pressure support ventilation via face mask in acute respiratory failure in hypercapnic COPD patients.

ObjectiveTo test whether non-invasive ventilation via facial mask could reduce the need for tracheal intubation via when mechanical ventilation must be initiated in COPD patients.DesignOpen prospective interventional study.SettingGeneral Intensive Care Service of a County Hospital.PatientsWe have studied 12 COPD patients during 14 episodes of acute exacerbation of chronic respiratory failure who failed to improve with intensive medical therapy and showed impairements in severe respiratory acidosis and/or hypercapnic encephalopathy leading their attending physicians to order mechanical ventilationInterventionsIn these circumstances, a trial of pressuresupport (PS) ventilation (Servo Ventilator 900Cℜ) via facial mask Vital Signs Inc.ℜ) was performed. The level of pressure support was adjusted to obtain a tidal volume>400 ml. If the patient deteriorated, tracheal intubation and standard mechanical ventilation were performed.Measurements and resultsMeasurements are presented as means±SEM. A pressure-support level of 14±3 cmH2O was used during a period of 8±4 h. Low levels of external PEEP were used in 4 patients, while it generated excessive leaks in the others. Significant differences (p<0.05 ANOVA for repeated measures) in data obtained on admission, when patients deteriorated and after pressure support was administered were only observed in PaCO2 (68±3 versus 92±3 versus 67±3 mmHg), arterial pH (7.27±0.03 versus 7.19±0.02 versus 7.31±0.01). SaO2 (60±4 versus 86±3 versus 92±1%) and respiratory rate (35±2 versus 32±2 versus 23±1 breaths·min−1). Three patients needed intubation and one of them died in the ICU.ConclusionNon-invasive ventilation (pressure-support) via face mask may reduce the need for tracheal intubation in the severe hypercapnic failure of COPD patients.

Role of bronchoalveolar lavage in mechanically ventilated patients with suspected pneumonia

To determine the usefulness of samples obtained by bronchoalveolar lavage (BAL) in establishing the diagnosis of ventilator-associated pneumonia, quantitative cultures of BAL and protected specimen brush (PSB) samples obtained via fiberoptic bronchoscope were compared in 42 patients with suspected ventilator-associated pneumonia. Direct examination of BAL fluid was also used to identify cells with intracellular organisms. Ventilator-associated pneumonia was diagnosed in 18 patients; a total of 39 microorganisms were recovered from BAL fluid and 29 from PSB specimens. Cultures of 21 BAL and 23 PSB specimens were sterile. Quantitative BAL and PSB cultures coincided in 76 % of cases. Sterile BAL and PSB cultures agreed in 87 % of cases. Cultures were completely discordant in only three cases. The sensitivity of BAL for diagnosis of ventilator-associated pneumonia using bacterial counts of ≥104 cfu/ml was 89 %, and specificity was 100 %. In 14 of the 18 patients with ventilator-associated pneumonia, the percentage of cells containing intracellular organisms in specimens recovered by BAL was 11.6 % versus 0.45 % in patients without pneumonia (p<0.05). In the remaining four patients, all of whom hadPseudomonas aeruginosa pneumonia, no intracellular organisms could be detected. Using a cut-off point of ≥ 5 % of cells with intracellular organisms, the sensitivity and specificity for the early diagnosis of ventilator-associated pneumonia was 67 % and 96 %, respectively. The results confirm the usefulness of the quantitative BAL culture (with a cut-off at 104 cfu/ml) for the diagnosis of ventilator-associated pneumonia. The identification of intracellular organisms in BAL fluid is a good early indicator of pneumonia, but the sensitivity of this technique may be lower forPseudomonas aeruginosa infections.

Intrinsic PEEP: a cause of inspiratory muscle ineffectivity.

Intrinsic PEEP has been described as an inspiratory threshold load to the inspiratory muscles that could increase the work of breathing. We report a patient who presented ineffective inspiratory efforts to trigger the ventilator; when we applied PEEP in similar amounts of measured intrinsic PEEP, his inspiratory efforts became able to trigger the ventilator, suggesting that the inspiratory load was alleviated.

Intrinsic PEEP' on static pressure-volume curves

The static pressure volume (PV) curve of the total respiratory system is a well established method to assess pulmonary mechanics during respiratory failure. We have tested the impact of auto-PEEP on the PV curve determination in 16 COPD patients. An isovolumic pressure increment (IPI) was found at the beginning of the curve and a close correlation between IPI and auto-PEEP level (r=0.962)p<0.001) was observed. The regression equation was not significantly different from the identity line. We conclude that the appearance of IPI in PV curves is largely determined by auto-PEEP and it is a good estimate of the existing auto PEEP level.