The use of helmets to deliver non-invasive continuous positive airway pressure in hypoxemic acute respiratory failure

Non-invasive continuous positive airway pressure (CPAP) is a useful tool for managing patients with acute respiratory failure. The head helmet is a relatively novel interface that is as effective as the traditionally employed face-mask in delivering CPAP and can possibly be characterized as better for the patient's tolerance and, consequently, a longer duration of treatment. This review focuses on the main properties of the helmet and the issues related to its use, as shown by the physiological and bench studies. Clinical experience, both personal and reported in the literature, for the treatment of both cardiogenic and non-cardiogenic pulmonary edema is reviewed as well.     

Measurement of end-expiratory lung volume by oxygen washin–washout in controlled and assisted mechanically ventilated patients

Objective  Assessing limits of agreement with helium dilution and repeatability of a new system (lung funcution, LUFU) that measures end-expiratory lung volume (EELV) in mechanically ventilated patients using the O₂ washin (EELV_Win) and washout (EELV_Wout) technique. LUFU consists of an Evita 4 ventilator, a side-stream oxygen analyzer, and a dedicated PC software. Design and setting  Prospective human study in a general ICU of a University hospital. Patients  Thirty-six mechanically ventilated patients. Interventions  We obtained 36 couples of both EELV_Win and EELV_Wout measurements in each patient (5 with healthy lungs, 9 with ALI, 22 with ARDS). Measurements were obtained with patients ventilated either by assisted (ASB, 16 measurements) or controlled (CMV, 20 measurements) ventilation. In 19 of 20 cases in CMV, we obtained helium dilution measurements (EELV_He). Measurements and results  Bias for agreement with EELV_He was −16 ± 156 and 8 ± 161 ml, respectively, for EELV_Win and EELV_Wout. Bias for agreement between EELV_Win and EELV_Wout was 28 ± 78 and 23 ± 168 ml, respectively, for CMV and ASB. During CMV bias for repeatability were 8 ± 92 and 23 ± 165 ml, respectively, for EELV_Win and EELV_Wout. During ASB bias for repeatability were 32 ± 160 and −15 ± 147 ml, respectively, for EELV_Win and EELV_Wout. Conclusions  The LUFU method showed good agreement with helium, and good repeatability during partial and controlled mechanical ventilation. The technique is simple and safe.     

Sigh Improves Gas Exchange and Lung Volume in Patients with Acute Respiratory Distress Syndrome Undergoing Pressure Support Ventilation

Background: The aim of our study was to assess the effect of periodic hyperinflations (sighs) during pressure support ventilation (PSV) on lung volume, gas exchange, and respiratory pattern in patients with early acute respiratory distress syndrome (ARDS).

Methods: Thirteen patients undergoing PSV were enrolled. The study comprised 3 steps: baseline 1, sigh, and baseline 2, of 1 h each. During baseline 1 and baseline 2, patients underwent PSV. Sighs were administered once per minute by adding to baseline PSV a 3- to 5-s continuous positive airway pressure (CPAP) period, set at a level 20% higher than the peak airway pressure of the PSV breaths or at least 35 cm H2O. Mean airway pressure was kept constant by reducing the positive end-expiratory pressure (PEEP) during the sigh period as required. At the end of each study period, arterial blood gas tensions, air flow and pressures traces, end-expiratory lung volume (EELV), compliance of respiratory system (Crs), and ventilatory parameters were recorded.

Results: Pao2 improved (P < 0.001) from baseline 1 (91.4 +/- 27.4 mmHg) to sigh (133 +/- 42.5 mmHg), without changes of Paco2. EELV increased (P < 0.01) from baseline 1 (1,242 +/- 507 ml) to sigh (1,377 +/- 484 ml). Crs improved (P < 0.01) from baseline 1 (40.2 +/- 12.5 ml/cm H2O) to sigh (45.1 +/- 15.3 ml/cm H2O). Tidal volume of pressure-supported breaths and the airway occlusion pressure (P0.1) decreased (P < 0.01) during the sigh period. There were no significant differences between baselines 1 and 2 for all parameters.     

Continuous flow biphasic positive airway pressure by helmet in patients with acute hypoxic respiratory failure: effect on oxygenation

Purpose  

We investigated the effects of periodical high pressure breaths (SIGH) or biphasic positive pressure ventilation (BIPAP) during helmet continuous positive airway pressure (CPAP) in patients with acute hypoxic respiratory failure.     

Patient–ventilator interaction in ARDS patients with extremely low compliance undergoing ECMO: a novel approach based on diaphragm electrical activity

Purpose

Patients with acute respiratory distress syndrome (ARDS) requiring extracorporeal membrane oxygenation (ECMO) usually present very low respiratory system compliance (Cst_rs) values (i.e., severe restrictive respiratory syndrome patients). As a consequence, they are at high risk of experiencing poor patient–ventilator interaction during assisted breathing. We hypothesized that monitoring of diaphragm electrical activity (EAdi) may enhance asynchrony assessment and that neurally adjusted ventilatory assist (NAVA) may reduce asynchrony, especially in more severely restricted patients.

Methods

We enrolled ten consecutive ARDS patients with very low Cst_rs values undergoing ECMO after switching from controlled to pressure support ventilation (PSV). We randomly tested (30 min) while recording EAdi: (1) PSV30 (PSV with an expiratory trigger at 30 % of flow peak value); (2) PSV1 (PSV with expiratory trigger at 1 %); (3) NAVA. During each step, we measured the EAdi-based asynchrony index (AI_EAdi) = flow-, pressure- and EAdi-based asynchrony events/EAdi-based respiratory rate × 100.

Results

AI_EAdi was high during all ventilation modes, and the most represented asynchrony pattern was specific for this population (i.e., premature cycling). NAVA was associated with significantly decreased, although suboptimal, AI_EAdi values in comparison to PSV30 and PSV1 (p < 0.01 for both). The PSV30–NAVA and PSV1–NAVA differences in AI_EAdi values were inversely correlated with patients’ Cst_rs (R ² = 0.545, p = 0.01 and R ² = 0.425, p < 0.05; respectively).

Conclusions

EAdi allows accurate analysis of asynchrony patterns and magnitude in ARDS patients with very low Cst_rs undergoing ECMO. In these patients, NAVA is associated with reduced asynchrony.     

Extracorporeal membrane oxygenation (ECMO) in patients with H1N1 influenza infection: a systematic review and meta-analysis including 8 studies and 266 patients receiving ECMO

Introduction

H1N1 influenza can cause severe acute lung injury (ALI). Extracorporeal membrane oxygenation (ECMO) can support gas exchange in patients failing conventional mechanical ventilation, but its role is still controversial. We conducted a systematic review and meta-analysis on ECMO for H1N1-associated ALI.

Methods

CENTRAL, Google Scholar, MEDLINE/PubMed and Scopus (updated 2 January 2012) were systematically searched. Studies reporting on 10 or more patients with H1N1 infection treated with ECMO were included. Baseline, procedural, outcome and validity data were systematically appraised and pooled, when appropriate, with random-effect methods.

Results

From 1,196 initial citations, 8 studies were selected, including 1,357 patients with confirmed/suspected H1N1 infection requiring intensive care unit admission, 266 (20%) of whom were treated with ECMO. Patients had a median Sequential Organ Failure Assessment (SOFA) score of 9, and had received mechanical ventilation before ECMO implementation for a median of two days. ECMO was implanted before inter-hospital patient transfer in 72% of cases and in most patients (94%) the veno-venous configuration was used. ECMO was maintained for a median of 10 days. Outcomes were highly variable among the included studies, with in-hospital or short-term mortality ranging between 8% and 65%, mainly depending on baseline patient features. Random-effect pooled estimates suggested an overall in-hospital mortality of 28% (95% confidence interval 18% to 37%; I² = 64%).

Conclusions

ECMO is feasible and effective in patients with ALI due to H1N1 infection. Despite this, prolonged support (more than one week) is required in most cases, and subjects with severe comorbidities or multiorgan failure remain at high risk of in-hospital death.     

Translaryngeal tracheostomy in acute respiratory distress syndrome patients

OBJECTIVE: To prevent gas exchange deterioration during translaryngeal tracheostomy (TLT) in patients with acute respiratory distress syndrome (ARDS) ventilation is maintained through a small diameter endotracheal tube (ETT; 4.0 mm i.d.) advanced beyond the tracheostoma. We report on the feasibility of uninterrupted ventilation delivered through a high-resistance ETT in ARDS patients, and relevant ventilatory adjustments and monitoring. DESIGN AND SETTING: Prospective, observational clinical study in an eight-bed intensive care unit of a university hospital. Patients: Eight consecutive ARDS patients scheduled for tracheostomy. INTERVENTIONS: During TLT volume control ventilation was maintained through the 4.0-mm i.d. ETT. Tidal volume, respiratory rate, and inspiratory to expiratory ratio were kept constant. Fractional inspiratory oxygen was 1. Positive end expiratory pressure (PEEP) set on the ventilator (PEEP(vent)) was reduced to maintain total PEEP (PEEP(tot)) at baseline level according to the measured intrinsic PEEP (auto-PEEP). MEASUREMENTS AND MAIN RESULTS: Data were collected before tracheostomy and while on mechanical ventilation with the 4.0-mm i.d. ETT. Neither PaCO(2) nor PaO(2) changed significantly (54.5+/-10.0 vs. 56.4+/-7.0 and 137+/-69 vs. 140+/-59 mmHg, respectively). Auto-PEEP increased from 0.6+/-1.1 to 9.8+/-6.5 cmH(2)O during ventilation with the 4.0-mm i.d. ETT. By decreasing PEEP(vent) we obtained a stable PEEP(tot) (11.4+/-4.3 vs. 11.8+/-4.3 cmH(2)O), and end-inspiratory occlusion pressure (26.7+/-7.4 vs. 28.0+/-6.6 cmH(2)O). Peak inspiratory pressure rose from 33.8+/-8.1 to 77.8+/-12.7 cmH(2)O. CONCLUSIONS: The high-resistance ETT allows ventilatory assistance during the whole TLT procedure. Assessment of stability in plateau pressure and PEEP(tot) by end-inspiratory and end-expiratory occlusions prevent hyperinflation and possibly barotrauma.     

Computerised tomography scan imaging in acute respiratory distress syndrome

Computerised tomography (CT) is being used with increasing frequency in acute respiratory distress syndrome (ARDS) patients. This brief review will discuss some of the clinical insights that a CT scan can offer. A large number of CT scan studies have provided new insights into the pathophysiology of ARDS and of mechanical ventilation, and are particularly focused on the recruitment-derecruitment phenomenon. To this end, newer fast CT scan technology promises a dynamic, rather than a static view of lung ventilation.