C Hoelz

Ventilator associated pneumonia: comparison between quantitative and qualitative cultures of tracheal aspirates

IntroductionDeferred or inappropriate antibiotic treatment in ventilator-associated pneumonia (VAP) is associated with increased mortality, and clinical and radiological criteria are frequently employed to establish an early diagnosis. Culture results are used to confirm the clinical diagnosis and to adjust or sometimes withdraw antibiotic treatment. Tracheal aspirates have been shown to be useful for these purposes. Nonetheless, little is known about the usefulness of quantitative findings in tracheal secretions for diagnosing VAP.MethodsTo determine the value of quantification of bacterial colonies in tracheal aspirates for diagnosing VAP, we conducted a prospective follow-up study of 106 intensive care unit patients who were under ventilatory support. In total, the findings from 219 sequential weekly evaluations for VAP were examined. Clinical and radiological parameters were recorded and evaluated by three independent experts; a diagnosis of VAP required the agreement of at least two of the three experts. At the same time, cultures of tracheal aspirates were analyzed qualitatively and quantitatively (105 colony-forming units [cfu]/ml and 106 cfu/ml)ResultsQuantitative cultures of tracheal aspirates (105 cfu/ml and 106 cfu/ml) exhibited increased specificity (48% and 78%, respectively) over qualitative cultures (23%), but decreased sensitivity (26% and 65%, respectively) as compared with the qualitative findings (81%). Quantification did not improve the ability to predict a diagnosis of VAP.ConclusionQuantitative cultures of tracheal aspirates in selected critically ill patients have decreased sensitivity when compared with qualitative results, and they should not replace the latter to confirm a clinical diagnosis of VAP or to adjust antimicrobial therapy.

Impacto de biópsia pulmonar a céu aberto na insuficiência respiratória aguda refratária

OBJECTIVE: To determine the impact that open lung biopsy findings have on decisions regarding changes in the treatment strategies employed for critically ill patients presenting diffuse pulmonary infiltrates and suffering from refractory acute respiratory failure, as well as on their clinical improvement. METHODS: This study involved 12 mechanically ventilated patients with acute respiratory failure who were subjected to open lung biopsy (by thoracotomy) after not presenting a clinical response to standard treatment. RESULTS: The single most common cause of the acute respiratory failure was viral infection, which was identified in 5 patients (40%). The pre-operative evaluation of the cause of respiratory failure was modified in 11 patients (91.6%), and a specific diagnosis was made in 100% of the cases. Regardless of changes in treatment regimen, the mortality rate was 50%. Six patients (50%) survived to be discharged from the hospital. All of the discharged patients survived for at least one year after the open lung biopsy, for an overall one-year survival rate of 50% among the 12 patients studied. For the patients who died in the hospital, the time of survival after open lung biopsy was 14 + 10.8 days. CONCLUSION: We conclude that open lung biopsy is a useful tool in the management of acute respiratory failure when there is no clinical improvement after standard treatment, since it can lead to a specific diagnosis that requires distinct treatment, which probably lowers the mortality rate among such patients.

Respiratory system mechanics in guinea pigs after acute hemorrhage: role of adrenergic stimulation.

We evaluated the effects of acute blood loss on the respiratory mechanics of guinea pigs. We measured respiratory system elastance (Ers) and resistance (Rrsmax) using the end-inflation occlusion method. Rrsmax was partitioned into its homogeneous component (Rrsmin) and that due to the unevenness within the respiratory system (Rrsu). Respiratory mechanics were studied both before and immediately after bleeding in eight animals. Another eight guinea pigs had received propranolol previously and were also submitted to hemorrhage. Propranolol-treated animals showed higher control values of Rrsmax (p less than .02) and Rrsmin (p less than .0001). Animals not treated with propranolol exhibited a decrease (p less than 0.001) in Rrsmax after hemorrhagic hypovolemia (from 0.375 +/- 0.051 to 0.323 +/- 0.042 cm H2O/ml.sec), due to a decrease (p less than 0.005) in Rrsmin (from 0.140 +/- 0.031 to 0.094 +/- 0.032 cm H2O/ml.sec), whereas Ers and Rrsu did not change. Propranolol-treated animals showed an increase (p less than .001) in Rrsmax (from 0.512 +/- 0.133 to 0.664 +/- 0.144 cm H2O/ml.sec), Rrsu (p less than 0.01) from 0.252 +/- 0.09 to 0.345 +/- 0.139 cm H2O/ml.sec, and Ers (p less than 0.001) (from 4.565 +/- 0.933 to 5.402 +/- 1.24 cm H2O/ml) after bleeding. The results indicate that the immediate effects of acute bleeding on respiratory mechanics are significantly influenced by catecholamines.

Flow or pressure triggering during pressure support ventilation

Pressure and flow triggering have improved greatly in the new generation of ventilators. The routine use of one or the other in adult patients in the ICU setting is not yet well established.

CO2 dynamics in ARDS patients: effects of PEEP above the Pflex

Titrating PEEP above the Pflex can improve oxygenation and survival when compared to the conventional ventilation in ARDS patients. In order to study the dynamics of CO2 in ARDS patients as well as the effects of setting PEEP above the Pflex on the CO2 dynamics we studied seven patients with ARDS criteria (less than 5 days of installation), with mean age of 63 ± 0.11 years and mean APACHE score of 21.4. After performing the PxV curve (random volumes) we ventilated the patients with 8 ml/kg TV and RR of 15 and PEEP of 5 cmH2O. Then we kept the same MV and set PEEP 2 cmH2O above Pflex for 30 min. Then we decreased PEEP to 5 for more 30 min. All the patients have a Swan-Ganz catheter and a continuous tonometer.

Maximal recruitment strategy guided by thoracic computed tomography scan in acute respiratory distress syndrome patients: preliminary results of a clinical study.

There is great controversy concerning protective ventilatory strategy in ARDS. Recruitment maneuvers and PEEP titration sufficient to avoid collapse and tidal recruitment in the lung are the major goals of the maximal recruitment strategy (MRS) guided by computed tomography (CT).

Influence of the pressure support slope on the respiratory parameters of intensive care unit patients

The possibility of changing the pressure slope during pressure support ventilation is a characteristic of the new generation of ICU ventilators. However, the influence of the slope changes on the respiratory parameters in ICU patients is still under investigation.

Does the cycling-off criteria of pressure support change the respiratory parameters in intensive care unit patients?

In modern mechanical ventilators it is possible to modify the flow cycling-off criteria of pressure support ventilation. The changes in the flow cycling-off criteria of pressure support ventilation can modify the synchrony between the mechanical and neural inspiration termination.

Automatic pressure support reduction is effective in weaning postoperative patients in the intensive care unit

Automatic pressure support reduction based on a targeted respiratory frequency or MRV is disposable in the TAENA ventilator for an automatic reduction of pressure support during weaning of patients in the intensive care unit (ICU). We studied 23 patients (63.52 years) in the postoperative period (14 cardiac, two thoracic and seven abdominal surgeries) in a prospective, randomized protocol comparing automatic pressure support weaning with the traditional manual reduction of pressure support to 5–7 cmH2O in our ICU. After arriving in the ICU after cardiac, thoracic or abdominal surgery, the patients were randomly assigned to traditional weaning consisting of manual reduction of pressure support (the pressure support was decreased every 30 min, keeping the RR/TV(L) < 80 until 5–7 cmH2O pressure support ventilation) or to the automatic pressure support reduction (MRV) with a respiratory frequency target of 20/min (the TAENA ventilator automatically decreased the pressure support ventilation level by 1 cmH2O every four respiratory cycles if the patients RR was less than 16/min). Twelve patients were assigned to manual weaning whereas 11 patients were assigned to the automatic pressure support reduction weaning. The weaning mean time for the manual group was 3.18 hours while the weaning mean time for the automatic pressure support reduction group was 2.24 hours. There was no reintubation in both groups.

Staphylococcia and severe acute respiratory distress syndrome

A 17-year-old boy with type I diabetes mellitus, was admitted to the intensive care unit with a 7-day history of right ankle contusion that progressed to erysipela, fasciitis and acute respiratory failure (septic embolic pneumonia – blood cultures positive to Staphylococcus aureus). Chest X-ray revealed bilateral infiltrates, the PaO2/FiO2 ratio was 150 and there was no evidence of pulmonary congestion. Vancomycin and surgical intervention were initiated and a thoracic computed tomography (CT) scan was performed right after the patient was intubated. The CT revealed gravity-dependent opacities and peribronchiolar patchy infiltrates. A stepwise recruitment maneuver (SRM) with high positive end expiratory pressure (PEEP) levels (25, 30, 35, 40 and 45 cmH2O) and a fixed pressure control level of 15 cmH2O was carried out at the Radiology suite, and the PEEP was titrated in order to keep the lung open and to minimize VILI. The CT scan showed that the lung opened with 45 cmH2O PEEP+15 cmH2O PCV (60 cmH2O total), and was kept open with 25 cmH2O PEEP; the PaO2/FiO2 ratio was >350. After 24 hours the PaO2/FiO2 ratio worsened and another SRM was performed; the PEEP increased to 29 cmH2O and the PaO2/FiO2 ratio increased to >350. The FiO2 was decreased to 30%, and after 96 hours the PEEP levels were progressively decreased and pressure support ventilation was initiated. After 10 days of intubation, the patient was weaned from mechanical ventilation and started on hyperbaric oxygen. After 3 days of extubation, the patient was breathing room air with SpO2 >95%. The CT scan showed that the SRM is important before increasing PEEP levels. PEEP levels must be set in order to prevent alveolar collapse according to the CT scan or PaO2/FiO2 ratio > 350, and it is important to initiate pressure support ventilation as soon as possible in order to prevent critical illness polyneuropathy. In this case we did not observe barotrauma, circulatory failure, ventilator-associated pneumonia, and the intensive care unit length of stay was 12 days. In this severe case of acute respiratory distress syndrome, the SRM with high PEEP levels and PEEP titration according to the CT scan and according to PaO2/FiO2 ratio > 350 was effective, and related to a better prognosis.