PURPOSE: The mechanical in-exsufflator (MIE) has been used to augment airway clearance in patients with weak or ineffective cough. Data to support the efficacy and safety in both adult and pediatric patients (Bach et. al, Miske et.al) exists. MIE is occasionally witheld in patients after upper abdominal surgery because of concerns for excessive intra-abdominal pressure or gastric distension. We questioned if gastric pressure and abdominal compartment size changed during MIE treatment.
METHODS: We enrolled subjects who had (1) been utilizing MIE via mouthpiece or mask for at least 30 days, and (2) had a gastrostomy tube in place for at least 30 days. During clinical stability, a pressure transducer was connected via tubing to the gastrostomy tube feeding adaptor. Pressure was sampled at 200 Hz with a digital signal processing system. Inductance bands were placed around the chest and abdomen for respiratory inductive plethysmography. Chest and abomen excursions were sampled during quiet breathing for QDC calibration. Subjects then received an MIE treatment at usual pressures, during which peak gastric pressures were recorded, both during insufflation and exsufflation. A subset of subjects were able to have pressures measured during spontaneous cough.
RESULTS: Four subjects (20 months to 18.5 years, 4 males) were enrolled after obtaining informed consent. All had neuromuscular disease. Insufflation pressures during MIE were +30 cm H2O. During tidal breathing, gastric pressure changed minimally (0.1-6.4 cmH2O). During insufflation, peak gastric pressures ranged -3 to +19 cmH2O. Changes in rib cage volume (22% - 228%) and abdominal compartment volume (-67% to 68%) were highly variable. One subject, during spontaneous cough, generated peak gastric pressure of 25 cmH2O, 67% higher than during MIE, with no change in abdominal volume.
CONCLUSION: Neither gastric pressure nor abdominal volume changed excessively during MIE use. Insufflation pressure did not correlate with pressure changes in the stomach.
CLINICAL IMPLICATIONS: Gastric pressure with MIE is less than spontaneous cough pressures and therefore preliminary data suggest MIE can safely be used for airway clearance in post-operative patients with pain.
DISCLOSURE: Laura Miske, None.