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Introduction: The intermittent intrapulmonary deflation (IID) technique is a recent airway clearance technique that intends to delay the onset of expiratory flow limitation (EFL) during exhalation. We showed in a previous study that IID increased the expiratory volume of COPD patients compared to quiet breathing and positive expiratory pressure (PEP) therapy. We hypothesized that it was due to the attenuation of the EFL. Objectives: To verify the physiologic effects of IID and PEP techniques on EFL with a mechanical lung model. Methods: A mechanical lung model was created to assess the effects of IID and PEP techniques. The thorax was simulated by a plexiglas box in which an adult test lung was connected. A calibration syringe simulated the inspiratory phase. Later, with activation of the IID, the expiratory phase was driven by the deflation generated by the device. With PEP, the expiration occurred maintaining an expiratory pressure between 5-10 cmH2O. A pneumotachograph and a pressure transducer were placed in series for flow, volumes and pressure measurements. Results: The model reproduced physiological characteristics of EFL. However, the deflation of the model was slowed by IID and PEP, and flow remained almost constant, so flow limitation was reduced. Conclusion: The IID and PEP attenuate EFL and increase exhaled volume in the in vitro model.

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Introduction: Patients receiving cardiac surgeries present high risk of developing postoperative complications. Incentive spirometry (IS) is used for the prevention and treatment of postoperative pulmonary complications in patients undergoing cardiac surgeries. Publications have suggested that IS is ineffective. In contrast, some studies have shown that when IS is adequately used, it may lead to beneficial outcomes. Objectives: To assess the effect of IS in patients undergoing cardiac surgeries. Methods/design: Systematic Reviews with randomised and quasi-randomised trials with adult patients undergoing cardiac surgeries, evaluating the effect of flow or volume-oriented IS. Outcome measures: postoperative pulmonary complications; adverse events; mortality; length of hospital stay; length of intensive care unit stay; reintubation rate; pulmonary function; antibiotic use; oxygenation; and respiratory muscle strength. Search: MEDLINE, EMBASE, CENTRAL, PEDro, CINAHL, LILACS, SCIELO, Allied, AMED, Scopus, Open Grey database, the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP), ClinicalTrials.gov, clinicaltrialsregister.eu, and ReBec. Two authors will independently extract data. PEDro scale will be used to evaluate the methodological quality of the studies. Meta-analysis will be performed using the inverse variance method and the random effects model in RevMan 5.3. We will use the I2 statistic to estimate the amount of heterogeneity across studies in each meta-analysis. Ethics and dissemination: The approval of an ethical committee is not required. Only clinical trials that have complied with ethical guidelines and followed the Declaration of Helsinki, will be included in this systematic review. The findings of this study will help clarify uncertainties about the effects of incentive spirometry in the postoperative period of cardiac surgery and may be disseminated to clinicians, assisting in decision making and including the best evidence in the treatment of their patients. Discussion: This review will clarify the uncertainty over whether IS is a useful technique for patients undergoing cardiac surgeries. While good quality studies have shown IS is an effective prophylactic technique, other studies have suggested that there is no evidence to support IS utilization.Keywords: incentive spirometry, cardiac surgery, postoperative.