Penetration of an aerosol, produced by film atomization, through the carinal bifurcation

A Proof-of-Principle Setup for Delivery of Relenza® (Zanamivir) Inhalation Powder to Intubated Patients

BACKGROUND

A fatal incident was reported when a mechanical ventilated patient received nebulization of a reconstituted Relenza^® formulation. We propose a delivery system to introduce Relenza and other inhalation dry powders to intubated patients to avoid accidental fatalities in the future.

METHODS

This is a bench study demonstrating the feasibility of a delivery system to introduce dry powder of Relenza to intubated patients. A dry powder inhaler placed within a delivery chamber was actuated by compressing a ventilation bag to disperse powder into a tracheal tube. The performance of two inhalers, a Diskhaler^® and an Osmohaler^™, were compared. The effects of the length and size of the tracheal tube on the powder output and sizing of emitted powder were investigated using the more efficient Osmohaler^™.

RESULTS

The efficiency of Osmohaler in delivering Relenza to the distal end [delivered dose=30.2±0.2% and fine particle fraction (FPF)=14.5±1.7%] was significantly higher than the Diskhaler (delivered dose=18.1±4.7% and FPF=3.4±2.1%). While no differences in the delivered dose and FPF were observed between the tracheostomy and endotracheal tubes of the same internal diameter, a larger endotracheal tube (9.0 mm internal diameter) gave a 6% higher FPF compared with the smaller counterpart (7.0 mm internal diameter).

CONCLUSION

The dry powder delivery system has been demonstrated to be capable of delivering Relenza formulation to the distal end of tracheal tubes with a reasonable delivered dose and FPF. It would be necessary for further investigation into incorporating the proposed powder delivery system within a mechanical ventilator, as well as animal and clinical studies to prove its applicability to deliver zanamivir dry powder to ventilated influenza patients in the intensive care setting.

Biofilm Formation on Tracheostomy Tubes

An increased awareness of biofilms and their mechanisms has led to a better understanding of bacterial infections that occur following the placement of tracheostomy tubes and other implanted devices and prostheses. One aspect of biofilm formation that is still subject to debate is whether the specific material that is used to manufacture a tube has any bearing in the incidence of infection. We conducted a test of four different tube materials—polyvinyl chloride, silicone, stainless steel, and sterling silver—to ascertain how bacterial biofilms form on tracheostomy tubes and to determine if there is a material-dependent difference in biofilm formation. Scanning electron microscopy demonstrated that Pseudomonas aeruginosa and Staphylococcus epidermidis both formed bacterial biofilms on tracheostomy tubes in vitro. We also found that there was no difference in susceptibility to biofilm formation among the four tube materials tested.

A randomized clinical trial of intermittent subglottic secretion drainage in patients receiving mechanical ventilation

OBJECTIVE

To study the effect of subglottic secretions drainage on the incidence of ventilator-associated pneumonia (VAP) in patients receiving mechanical ventilation.

DESIGN

A randomized clinical trial.

SETTING

A 12-bed general ICU.

PATIENTS

One hundred fifty patients with an expected duration of mechanical ventilation > 72 h were enrolled in the study.

INTERVENTION

Patients were randomly assigned to receive either an endotracheal tube for intermittent subglottic secretions drainage or a standard endotracheal tube.

OUTCOME MEASUREMENTS

Incidence of VAP, duration of mechanical ventilation, length of ICU stay, length of hospital stay, and mortality.

RESULTS

Seventy-five patients were randomized to subglottic secretion drainage, and 75 patients were randomized to the control group. The two groups were similar at the time of randomization with respect to demographic characteristics and severity of illness. VAP was seen in 3 patients (4%) receiving suction secretion drainage and in 12 patients (16%) in the control group (relative risk, 0.22; 95% confidence interval, 0.06 to 0.81; p = 0.014). The other outcome measures were not significantly different between the two groups.

CONCLUSION

Intermittent subglottic secretion drainage reduces the incidence of VAP in patients receiving mechanical ventilation.

Contribution of endotracheal tubes to the pathogenesis of ventilator-associated pneumonia

The contribution of ventilatory equipment to the pathogenesis of ventilator-associated pneumonia (VAP) is well-established but the design of endotracheal tubes has been improved only to reduce tracheal traumatization. However many factors, including the surface properties of the endotracheal tube, humidity of the ventilatory gases, ventilatory mode and nursing management result in the formation of an infective, highly viscous and adhesive layer inside of the endotracheal tube. Endotracheal tubes may contribute to the pathogenesis of VAP when infective particles of this adhesive layer are dislodged into the lower airways by shear forces imparted by the respiratory gasflow. The current state of research is reviewed and potential solutions to this problem are discussed.

New insights into the pathogenesis of ventilator-associated pneumonia

Colonization of the lower respiratory tract of critically ill patients with Gram-negative bacilli is an early stage in the pathogenesis of ventilator-associated pneumonia. Recent studies have emphasized the endogenous source of these bacteria and have pointed to the upper gastrointestinal tract as a major source. Gastric bacterial overgrowth is known to be promoted by raised intragastric pH. Further evidence suggests that duodenal reflux is just as important in gastric bacterial overgrowth and subsequent colonization of the mechanically ventilated lung. Work on the biomaterials lining the inside of the tracheal tube in critically ill patients has shown that this biofilm can be scattered many centimetres as a result of ventilator gasflow. In vitro and in vivo evidence has been found to support a fluid dynamic process that results in dissemination of tracheal tube biofilm, which also contains neutrophils and their contents. The dissemination of combined bacteria, effete neutrophils and their breakdown products into already compromised lungs may explain the complexity of the clinical condition known as ventilator-associated pneumonia. It may thus be more correct to refer to the condition as 'ventilator-induced pneumonitis'.