Chan Tb

Airway responsiveness of firefighters after smoke exposure

Ventilatory function and airway reactivity of 20 firefighters were studied one hour before and one hour after exposure in a smoke chamber. None showed an increase in airway reactivity to inhaled histamine before exposure. Eight (80%) of the regular firefighters, however, had an increase in airway reactivity after exposure in the smoke chamber. After six hours, three of the firefighters still had increased airway reactivity. All were non-reactive after 24 hours but the ventilatory function of the three firefighters who were reactive after six hours did not return to baseline values. The duration of service as a firefighter is the major contributing factor to the change in airway reactivity. This increase in airway responsiveness among regular firefighters suggests that some form of chronic epithelial injury is needed before an increase in airway responsiveness is seen.

Rapid Shallow Breathing (Frequency-Tidal Volume Ratio) Did Not Predict Extubation Outcome

This was a prospective study of 52 patients that were extubated in our medical intensive care unit. Rapid shallow breathing, represented by a ratio of frequency to tidal volume (f/VT) of more than 105, was evaluated either on continuous positive airway pressure or pressure support prior to extubation as a marker of extubation outcome. Twelve out of 13 patients (92 percent) with rapid shallow breathing (f/VT ratio > 105) were successfully extubated. Out of 9 extubation failures only 1 patient had a f/VT ratio more than 105 (11 percent). A measured f/VT ratio of less than 105 had a sensitivity and specificity of 72 and 11 percent, respectively, for extubation success. Patients who had unsuccessful outcomes were ventilated for a significantly more prolonged period (9.6 +/- 6.8 d vs 4.6 +/- 3.9 d, unpaired t test, p = 0.004). We conclude that the presence of rapid shallow breathing during a weaning trial with the patient on partial ventilatory support does not necessarily preclude successful extubation.