Nektaria Xirouchaki

Proportional assist ventilation with load-adjustable gain factors in critically ill patients: comparison with pressure support.

ObjectivesIt is not known if proportional assist ventilation with load-adjustable gain factors (PAV+) may be used as a mode of support in critically ill patients. The aim of this study was to examine the effectiveness of sustained use of PAV+ in critically ill patients and compare it with pressure support ventilation (PS).Design and settingRandomized study in the intensive care unit of a university hospital.MethodsA total of 208 critically ill patients mechanically ventilated on controlled modes for at least 36 h and meeting certain criteria were randomized to receive either PS (n = 100) or PAV+ (n = 108). Specific written algorithms were used to adjust the ventilator settings in each mode. PAV+ or PS was continued for 48 h unless the patients met pre-defined criteria either for switching to controlled modes (failure criteria) or for breathing without ventilator assistance.ResultsFailure rate was significantly lower in PAV+ than that in PS (11.1 vs. 22.0%, P = 0.040, OR 0.443, 95% CI 0.206–0.952). The proportion of patients exhibiting major patient–ventilator dyssynchronies at least during one occasion and after adjusting the initial ventilator settings, was significantly lower in PAV+ than in PS (5.6 vs. 29.0%, P < 0.001, OR 0.1, 95% CI 0.06–0.4). The proportion of patients meeting criteria for unassisted breathing did not differ between modes.ConclusionsPAV+ may be used as a useful mode of support in critically ill patients. Compared to PS, PAV+ increases the probability of remaining on spontaneous breathing, while it considerably reduces the incidence of patient–ventilator asynchronies.

Noninvasive Bilevel Positive Pressure Ventilation in Patients with Blunt Thoracic Trauma

Background: Noninvasive bilevel positive pressure ventilation (N-BiPAP) has an established role in providing respiratory support in patients with acute respiratory failure. The significant advantage of N-BiPAP is to avoid endotracheal intubation and its complications. Currently there are no data that support N-BiPAP as first-line treatment in patients with blunt thoracic trauma. Objective: To evaluate the safety and efficacy of N-BiPAP in patients with acute respiratory failure due to blunt thoracic trauma. Methods: Prospective observational study. Twenty-two patients with blunt chest trauma (mean injury severity score 26 ± 9) were studied. N-BiPAP was applied via a tight-fitting full or total-face mask, combined with regional anesthesia in all patients. Results:N-BiPAP resulted in significant changes in blood gasses, heart rate and breathing frequency at 1 h. Eighteen out of 22 patients avoided intubation and were discharged from the ICU (success group). Four patients met predefined criteria and required intubation (failure group) within 24 h after N-BiPAP. Three of the patients in the failure group survived while 1 developed septic shock and died. The acute response of oxygenation to N-BiPAP differed significantly between groups, being higher in the success group. Complications related to N-BiPAP were minor, consisting of nose bridge injury (1 patient) and gastric distention (1 patient). Conclusions: N-BiPAP administration could be a safe and effective method to improve the gas exchange in patients with acute respiratory failure due to blunt thoracic trauma.

Impact of lung ultrasound on clinical decision making in critically ill patients: response to O’Connor et al.

Dear Editor, We would like to thank Drs. O’Connor, Isitt and Vizcaychipi [1] for their interest in our paper [2] as well as for giving us the opportunity to better clarify our results. In our study 253 lung ultrasound (LU) examinations were performed in 189 patients. Thus some patients underwent more than one LU study. In these patients, the majority of whom had prolonged ICU stay, all LUs were performed for a new suspected diagnosis which was not related to the first examination. Therefore for net reclassification improvement (NRI) calculation, only LU examinations performed for new suspected diagnoses were used. Although in several cases repeated LUs were performed to follow up the condition of the patients, these results were not used (and not reported) in the study. Therefore we believe that NRI calculation is clear and not contaminated with repeated follow-up LU examinations. We certainly agree that our results are heavily influenced by the expertise of one of the authors (NX). Although LU can be performed by almost all attending physicians in our unit, we decided, for the purpose of a uniform interpretation of the findings, to involve a single experienced operator in our study. This should also minimize the influence of the variability of operator bias on the results, as the operator simply presented the findings to the primary physician and was not responsible for further patient management. However, since in our previous study the LU findings were comparable to those obtained by CT scans [3], it is likely that the impact of LU on decision making is influenced by the reliance of the attending physician on the LU examination. There is no question that this represents a major limitation of the study and may make it difficult to replicate in other ICUs. We believe that in order to use LU in the decisionmaking process a kind of validation procedure should be performed first. In particular, the LU diagnosis of pneumothorax represents a challenge and we thus believe that the operator should feel confident about his/her skills in interpretation of LU findings that support or exclude this condition. We agree that in our study [1] the suspicion of pneumothorax was high. This high index of suspicion was due to several reasons. Firstly, by study design all patients were on mechanical ventilation, a well-known risk factor for pneumothorax. Secondly, several of our patients suffered from multiple trauma and/or ARDS necessitating the application of high PEEP and recruitment manoeuvre, forcing the primary physician to order an LU to address the issue of pneumothorax. Thirdly, in several cases the primary physician easily ordered an LU to confirm/exclude the diagnosis of pneumothorax even without strong clinical evidence for this complication. This decision was driven by the excellent diagnostic accuracy of LU for pneumothorax shown in our previous study [2]. However it is of interest to note that in 35 out of 253 LU examinations (14 %) the diagnosis of pneumothorax was made [1]. These results highlight the value of LU in diagnosing this complication which in mechanically ventilated patients may be devastating.

Effect of Albuterol on Expiratory Resistance in Mechanically Ventilated Patients

BACKGROUND: In mechanically ventilated patients with COPD, the response of the expiratory resistance of the respiratory system (expiratory RRS) to bronchodilators is virtually unknown. OBJECTIVE: To examine the effect of inhaled albuterol on expiratory RRS, and the correlation of albuterol-induced changes in expiratory RRS with end-inspiratory resistance and the expiratory flow-volume relationship. METHODS: We studied 10 mechanically ventilated patients with COPD exacerbation, before and 30 min after administration of albuterol. We obtained flow-volume curves during passive expiration, divided the expired volume into 5 equal volume slices, and then calculated the time constant and dynamic effective deflation compliance of the respiratory system (effective deflation CRS) of each slice via regression analysis of the volume-flow and post-occlusion volume-tracheal pressure relationships, respectively. For each slice we calculated expiratory RRS as the time constant divided by the effective deflation CRS. RESULTS: Albuterol significantly decreased the expiratory RRS (mean expiratory RRS 42.68 ± 17.8 cm H2O/L/s vs 38.08 ± 16.1 cm H2O/L/s) and increased the rate of lung emptying toward the end of expiration (mean time constant 2.51 ± 1.2 s vs 2.21 ± 1.2 s). No correlation was found between the albuterol-induced changes in expiratory RRS and that of end-inspiratory resistance. Only at the end of expiration did albuterol-induced changes in the expiratory flow-volume relationship correlate with changes in expiratory RRS in all patients. CONCLUSIONS: In patients with COPD, albuterol significantly decreases expiratory resistance at the end of expiration. In mechanically ventilated patients, neither inspiratory resistance nor the whole expiratory flow-volume curve may be used to evaluate the bronchodilator response of expiratory resistance.

Acute respiratory distress and hemorrhagic shock in a patient 12 days after elective hepatic surgery.

A 69-year-old woman was admitted to the Surgical Department for elective cholecystectomy and enucleation of a large hepatic hemangioma. Her past medical history was unremarkable and her initial laboratory tests were normal. The patient received peri-operatively ceftriaxone and postoperatively low-molecular-weight heparin for venous thrombosis prophylaxis. Her post-operative course was uneventful. On the 12th postoperative day, the patient exhibited acutely, respiratory distress, tachycardia and abdominal pain while her blood pressure dropped significantly (systolic blood pressure < 90 mmHg) with a concomitant decrease in hemoglobin (Hb) from 10.5 g/dl to 7 g/dl. The clinical examination revealed considerable abdominal distension and tenderness and absence of bowel sounds. The blood pressure did not respond to rapid infusion of blood products and fluids, and the patient’s condition was rapidly deteriorating.

Tree-like colour Doppler in diagnosing pneumonia in critically ill: a picture is worth a thousand words

Pneumonia remains a difficult sonographic diagnosis in the critically ill. It is characterized by hypoechoic areas, irregular margins, heterogeneous echo texture, dynamic air bronchogram, pleural effusion and vascular flow within consolidated lung. Air bronchogram is an important sign in differentiating lung consolidation. When dynamic (strong echogenic structure with air moving through bronchi), linear or dendritic, it is a diagnostic sonographic sign of pneumonia (Fig. 1a, b). In contrast, the air bronchogram associated with obstructive

The Role of Lung Ultrasound on the Daily Assessment of the Critically Ill Patient

The first lung ultrasound (LU) pattern, obtained from a patient with pleural effusion, was described by Pell in 1964. Three years later, Joyner et al. [1] published the first study which described the accuracy and reliability of LU in the diagnosis of pleural fluid. Thereafter, for several years, the use of LU was limited only to the detection of pleural effusion. This has drastically changed in the last decade. Nowadays, LU has emerged as a powerful, non-invasive, easily repeatable bedside diagnostic tool, and is increasingly used in critically ill patients [2–4]. Studies have shown that in these patients, LU has a high diagnostic accuracy in identifying pneumothorax, consolidation/atelectasis, interstitial syndromes (i.e. pulmonary oedema of cardiogenic or non-cardiogenic origin), pleural effusion, and, on the appropriate clinical grounds, it may help in the diagnosis of pneumonia. Indeed, LU may be considered an alternative to thoracic computed tomography (CT) scan when identifying these pathological conditions which are commonly encountered in critically ill patients (Fig. 8.1) [2, 3].

Response to Katz et al.: Lung ultrasound in the intensive care unit: an idea that may be too good to be true

Dear Editor, We would like to thank Dr. Katz and colleagues [1] for their interest in our editorial [2] as well as for giving us the opportunity to better clarify our view regarding the value of lung ultrasound (LU) as a diagnostic and monitoring tool in critically ill patients. We never claimed that ‘‘ultrasound may be considered an alternative to thoracic CT’’. We clearly stated that first-line lung ultrasound may be an alternative to thoracic CT in most situations commonly encountered in these patients. Specifically, it has been shown that lung ultrasound has high diagnostic accuracy in identifying pneumothorax, consolidation/atelectasis, interstitial syndromes (i.e., pulmonary oedema of cardiogenic or noncardiogenic origin), and pleural effusion, and, on the appropriate clinical grounds, it may help in the diagnosis of pneumonia [2]. We and others have clearly shown the superiority of lung ultrasound over bedside chest radiography in identifying these specific pathological entities [3, 4]. In these studies thoracic CT was the gold standard imaging technique. We believe that regarding our previous study [5] in which the value of LU in clinical decision making was evaluated, Katz et al. misinterpreted both the purpose and data of the study. The aim of this study was to examine the impact of performing LU on clinical decision making in critically ill patients and not to compare LU with other imaging modalities. The latter has been performed previously (comparison of LU to thoracic CT) [3, 4]. The results of our previous study [3], showing that the diagnostic accuracy of LU in identifying specific pathologic entities is similar to thoracic CT, permitted us to examine the impact of LU on decision making [5]. The patients were enrolled in the study when LU was requested by the primary physician for unexplained deterioration of arterial blood gases and/or a suspected pathologic entity and when an experienced operator (NX) was available. The latter is certainly a limitation and we agree with Katz et al. on this point. Nevertheless, this limitation is not inherent to LU but concerns ultrasound imaging in general. In this study CT was not performed in every patient. Therefore, the statement of Katz et al. that ‘‘there was no correlation of ultrasound with CT findings in 246 of 253 patients’’ is inappropriate and totally misleading. Simple thoracic CT was only performed in 7 patients (not in 253 patients) and for reasons unrelated to the study. We agree that, from a radiological and possibly clinical point of view, consolidation is not synonymous with atelectasis. However, the clinical picture of the patients may, in most cases, help the physician/intensivist to differentiate between these two entities and in addition to use LU as a tool to monitor the impact of any intervention on the patient’s status. It is worthy of mention that both atelectasis and consolidation may affect the patient through common pathophysiological mechanisms, variables such as the shunt fraction, which are vital for patient status. It also seems that Katz and colleagues underestimated the strength and value of the clinical history/picture to differentiate pulmonary oedema from pneumonia and interstitial fibrosis from interstitial oedema. On appropriate clinical grounds, LU findings may be of great help to differentiate these conditions. Finally, we do not agree with Katz et al.’s suggestion of a randomised control trial to prove the value of echography in critically ill patients.