<p>The use of improvised positive expiratory pressure (PEP) device made from latex glove and syringe is common in low-resource settings in Nigeria; however, their effectiveness in improving lung function is not known. This study determined the effect of PEP Therapy (PEPT) using Improvised Latex Glove Device (ILgD) and Acapella Device (ACaD) on some lung function parameters.</p><p>This quasi-experimental study involved forty-six participants from a Nigerian tertiary hospital. Participants were allocated into either ACaD or ILgD group. Treatments were administered with dosage of ten blows per session thrice daily for ten days. Lung function parameters were assessed before surgery, six hours after recovery from anesthesia, 4, 8 and 10&#xa0;day post-surgery. Repeated measure ANOVA and independent t-test were applied.</p><p>The result of this study showed that in both ACaD and ILgD groups, there were significant improvement in FVC, FEV1, and PEFR across baseline, 4th, 8th, and 10th day (<i>p</i> = 0.001). In comparing the ACaD and ILgD group, the results showed significant differences in FVC at 4th (t = 4.110; <i>p</i> &lt; 0.001) and 8th (t = 2.230; <i>p</i> = 0.031) day. There were also significant differences in FEV_1% at 4th (t = 2.801; <i>p</i> = 0.008) and 10th (t = 2.573; <i>p</i> = 0.014) day. Furthermore, significant difference was observed in PEFR at day 4 (t = 3.409; <i>p</i> = 0.001). However, no significant mean changes were observed for FEV₁ at 4th, 8th, and 10th day (<i>p</i> &gt; 0.05).</p><p>Positive expiratory pressure therapy using Acapella device is not superior to improvised latex glove device for lung function rehabilitation of patients that underwent upper abdominal surgery.</p><p><b>Trial registration</b></p><p>PACTR, PACTR202210515878180. Registered 3rd of October 2022 Retrospectively registered, pactr.samrc.ac.za/TrialDisplay.aspx? TrialID = 24,035.</p>