Cardiorespiratory effects of manually compressing the rib cage during tidal expiration in mechanically ventilated patients recovering from acute severe asthma.

OBJECTIVES

To determine the cardiorespiratory effects of manual expiratory rib cage compression in mechanically ventilated patients recovering from acute severe asthma; and to extrapolate these findings to emergency asthma management where ventilation cannot be achieved by positive-pressure ventilation.

DESIGN

A prospective, clinical study.

SETTING

Intensive care unit.

PATIENTS

Four intubated, mechanically ventilated (volume-controlled), adult patients recovering from acute severe asthma.

INTERVENTIONS

Patients were studied before, during, and after a 2- to 3-min period of manual compressions applied bilaterally over the lower rib cage (ribs 8 to 10) during consecutive tidal expirations.

MEASUREMENTS AND MAIN RESULTS

Air flow (pneumotachograph), airway pressure, radial or brachial arterial pressure, and the hand pressure applied to the patient's rib cage were monitored and recorded on magnetic tape. Playback of the recorded data enabled measurement of changes in lung volume (air flow integration). Changes during rib cage compression consisted chiefly of small decreases in lung volume and peak inspiratory airway pressure that were only observed in the least obstructed patient and were fully reversed after the cessation of compressions. Air flow-time and air flow-volume plots demonstrated expiratory air flow limitation during essentially the entire tidal expiration in each patient, except the least obstructed patient.

CONCLUSION

The results suggest that manual compression of the rib cage during consecutive tidal expirations would be ineffective in reducing pulmonary hyperinflation during the emergency management of asthma when air flow obstruction is so severe that ventilation cannot be achieved by positive-pressure ventilation.