Study objectives: The study evaluated the impact of the
additional imposed work of breathing (WBimp) generated by two
different spirometers on postoperative incentive spirometry performance
in patients at high risk and moderate risk for postoperative pulmonary
complications (PPCs). Additionally, we investigated whether maximal
inspiratory pressure (Pimax) is an easy estimate of
the WBimp imposed by incentive spirometers.
Prospective, randomized, single-blind clinical trial.
Setting: ICU of a university hospital.
Interventions and measurements: Thirty male patients were
assigned to a group at high risk for PPCs (group A; inspiratory
capacity [IC], < 1.6 L) or to a group at moderate risk for PPCs
(group B; IC, 1.6 to 2.5 L) after upper-abdominal, thoracic, or
two-cavity surgery. On the first or second postoperative day WBimp, IC,
and Pimax were recorded without spirometers (baseline) and
during incentive spirometry with the Mediflo spirometer (Medimex;
Hamburg, Germany) (high WBimp) and the Coach spirometer (Kendall;
Neustadt, Germany) (low WBimp) using a pneumotachograph. In group A,
the baseline and the ICs for both spirometers only differed slightly.
In group B, the IC was significantly reduced for the Mediflo
(p < 0.05), which imposed a WBimp twice as high as the Coach
(p < 0.01). Pimax was significantly increased for both
the Mediflo and the Coach (p < 0.01). Pimax was
positively correlated with WBimp (r = 0.8).
Conclusions: Incentive spirometers differ considerably in
their additional Wbimp with a potential impact on the efficacy of
postoperative incentive spirometry performance. Pimax might
be an easy clinical estimate for the WBimp during incentive spirometry.
Incentive spirometers with low WBimp permit increased maximal sustained
inspiration and, thus, enhanced incentive spirometry performance, and,
therefore, it might be more suitable for use in postoperative