I was wondering if anyone had any good resources to studies comparing MDI to HHN in mechanically ventilated patients. I have a pulmonologist that insists on using Nebs for all her patients with COPD or Pneumonia. Her reasoning is that because the Neb is delivered over 15 minutes using the Aerogen Neb that as the upper airways dialate the meds can then reach the lower airways. I have some studies but nothing done in regards to pneumonia or COPD. I would really appreciate any help on this.

Lester Cash, RRT
Clinical Coordinator for Respiratory Care Services
St. Anthony Hospital
Oklahoma City, Oklahoma

Here is an article that includes COPD patients on mechanical ventilation.

http://ajrccm.atsjournals.org/cgi/content/full/156/1/3


Few investigators have examined the dose response to bronchodilators in mechanically ventilated patients (2, 4, 6, 41). In seven patients with COPD receiving intravenous aminophylline, Bernasconi and colleagues found significant decreases in airway resistance with cumulative doses of 0.4, 0.8, and 1.6 mg of fenoterol administered with a nebulizer; however, the response to the higher doses was no greater than that observed with the initial dose (41). Manthous and co-workers (2) administered incremental doses of 2.5, 5.0, and 7.5 mg of albuterol by a nebulizer in 10 patients with airway obstruction. They found a significant decrease in airway resistance with the 2.5 mg dose, a tendency toward a greater effect with a cumulative dose of 7.5 mg, but no further improvement with the cumulative dose of 15 mg (2). In the same study, up to 100 puffs (10 mg) of albuterol administered with an MDI and elbow adapter did not produce any bronchodilator effect (2). Subsequently, these investigators studied the administration of 5, 10, and 15 puffs of albuterol using an MDI and cylindrical spacer (4). Cumulative doses of 15 and 30 puffs of albuterol produced a significant bronchodilator effect, and the effect was similar with either dose; the fall in airway resistance with 5 puffs was not significantly different from baseline values. In mechanically ventilated patients with COPD, we administered 4, 8, and 16 puffs of albuterol with an MDI and cylindrical spacer (6). A significant decrease in airway resistance was observed after administration of 4 puffs, with no additional effect after cumulative doses of 12 and 28 puffs (Figure 5). In a separate group of patients with COPD, the bronchodilator effect of a single dose of 4 puffs of albuterol was sustained for at least 60 min (6). In summary, when the technique of administration was carefully executed, most stable mechanically ventilated patients with COPD achieved near-maximal bronchodilation after receiving 4 puffs of albuterol. Patients with acute exacerbations of asthma or COPD may require higher doses of inhaled bronchodilators, but further studies are needed to establish a dosing schedule in such patients.


Comparison of Metered-Dose Inhalers and Nebulizers

For ambulatory patients, nebulizers and MDIs are equally effective in treating airway obstruction. In a model of mechanical ventilation, nebulizers and MDIs delivered an equivalent mass of aerosol beyond the endotracheal tube (13), and in mechanically ventilated patients similar therapeutic effects were achieved with each device (55). However, several problems exist with the use of nebulizers. Contamination of nebulizers can lead to aerosolization of bacteria (56), and grossly negligent practices by respiratory therapy staff have led to epidemics of nosocomial pneumonia (57). Moreover, use of nebulizers requires adjustment of tidal volume and inspiratory flow to compensate for the nebulizer flow. While this is inconsequential in most adults, instances of hypoventilation have resulted in patients who are unable to trigger the ventilator during assisted modes of mechanical ventilation (58). Another shortcoming of nebulizers is the considerable variation in the efficiency of different commercial brands as well as among various batches of the same brand (59). In contrast, MDIs are easy to administer, involve less personnel time, and provide a reliable dose of the drug. Moreover, when MDIs are used with a collapsible cylindrical spacer it is not necessary to disconnect the ventilator circuit for each treatment, thereby reducing the risk of ventilator-associated pneumonia. Using MDIs instead of nebulizers results in substantial cost savings (60). Bowton and co-workers reported that more than two thirds of the respiratory treatments in their 700-bed hospital were administered to patients admitted to the intensive care units (61). They found that substituting MDIs for nebulizers could decrease potential patient costs of aerosol therapy in their hospital by $300,000 annually (61).

mjRT

It is also very important to locate your NEB or MDI back on the inspiratory limb of the ventilator circuit. We use the circuvent to route the drug around the HME.