Mechanical Insufflation-Exsufflation

FOR RELATED ARTICLE, SEE PAGE 929In patients with neuromuscular disease, respiratory muscle weakness is frequent and may be responsible for a reduced ability to cough, an important factor of respiratory morbidity and death. Among the multiple approaches to improve cough function and proximal airway secretions clearance, mechanical insufflation-exsufflation (MIE) therapy is certainly one of the most frequently used technique in these patients.1Chatwin M. Toussaint M. Goncalves M.R. et al.Airway clearance techniques in neuromuscular disorders: a state of the art review.Respir Med. 2018; 136: 98-110Abstract Full Text Full Text PDF PubMed Scopus (173) Google Scholar It was introduced in the 1950s after the poliomyelitis epidemic and currently is considered by several authors as an indisputable complement to noninvasive ventilation in this population.2Bach J.R. Choi W.A. Mechanical insufflation-exsufflation: the rest of the story.Respiration. 2023; 102: 327-330Crossref PubMed Scopus (0) Google Scholar There is a clear rationale to increase cough strength to improve clearance of pulmonary secretions, increase lung recruitment, and avoid complications associated with secretions accumulation.3Bach J.R. Mechanical insufflation-exsufflation. Comparison of peak expiratory flows with manually assisted and unassisted coughing techniques.Chest. 1993; 104: 1553-1562Abstract Full Text Full Text PDF PubMed Google Scholar,4Khan A. Frazer-Green L. Amin R. et al.Respiratory management of patients with neuromuscular weakness: an American College of Chest Physicians Clinical Practice Guideline and Expert Panel Report.Chest. 2023; 164: 394-413Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar However, although MIE (among other approaches such as glossopharyngeal breathing, manually assisted cough or lung volume recruitment by air stacking) increases cough peak flow compared with unassisted cough, recent reviews, meta-analyses, and guidelines show that this is supported only by a low level of evidence.4Khan A. Frazer-Green L. Amin R. et al.Respiratory management of patients with neuromuscular weakness: an American College of Chest Physicians Clinical Practice Guideline and Expert Panel Report.Chest. 2023; 164: 394-413Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar,5Morrow B. Argent A. Zampoli M. Human A. Corten L. Toussaint M. Cough augmentation techniques for people with chronic neuromuscular disorders.Cochrane Database Syst Rev. 2021; 4: CD013170Google Scholar Moreover, the optimal parameters to use during MIE are still unknown. Initial knowledge mainly derived from the works conducted by Bach et al2Bach J.R. Choi W.A. Mechanical insufflation-exsufflation: the rest of the story.Respiration. 2023; 102: 327-330Crossref PubMed Scopus (0) Google Scholar,3Bach J.R. Mechanical insufflation-exsufflation. Comparison of peak expiratory flows with manually assisted and unassisted coughing techniques.Chest. 1993; 104: 1553-1562Abstract Full Text Full Text PDF PubMed Google Scholar who brought a huge contribution to the field, but with retrospective studies mostly, provided little evidence on how these techniques should be applied. FOR RELATED ARTICLE, SEE PAGE 929 One of the most challenging questions about this issue is the relevance of the pressure level to be used for MIE therapy. There is no consensus today on the optimal level to be used. Of note, concerns may arise from the use of high exsufflation pressures in a population of patients with high risk of airway collapse development and from the use of high insufflation pressures in those patients with cardiac comorbidities. Conversely, with suboptimal pressures, MIE therapy may not be efficient. In this issue of CHEST, Shah et al6Shah N.M. Apps C. Kaltsakas G. et al.The effect of pressure changes during mechanical insufflation-exsufflation on respiratory and airway physiology.Chest. 2024; 165: 929-941Abstract Full Text Full Text PDF Google Scholar present a comparative study of the impact of high vs low pressures during MIE therapy on several physiologic parameters in three different populations of patients with chronic neuromuscular diseases and low cough peak flow (CPF) (Duchenne muscular dystrophy, spinal cord injury, and long-term tracheostomy ventilation). To provide a picture of usual clinical practice, the authors chose to test, in a random order, the effect of high (+60/-60 cm H2O during inspiration/expiration) vs low (+30/-30 cm H2O) pressures on CPF, but also on lung recruitment, neural respiratory drive, and patient comfort.6Shah N.M. Apps C. Kaltsakas G. et al.The effect of pressure changes during mechanical insufflation-exsufflation on respiratory and airway physiology.Chest. 2024; 165: 929-941Abstract Full Text Full Text PDF Google Scholar The main finding is that, despite a greater increase in CPF compared with low pressure, high insufflation pressures do not provide any benefit on lung recruitment or neural respiratory drive, and, on the contrary, high exsufflation pressures would increase the rate of upper airway closure and reduce patient comfort, hence leading to lesser therapy compliance. In this perspective, one would wonder about long-term effect of high-pressure therapies in patients with neuromuscular disease. In these patients, during episodes with secretion accumulation and presence of atelectasis, the aerated lung is likely to be reduced, as the so called "baby-lung," previously described in patients with ARDS.7Gattinoni L. Carlesso E. Caironi P. Stress and strain within the lung.Curr Opin Crit Care. 2012; 18: 42-47Crossref PubMed Scopus (103) Google Scholar In addition, lung overdistention caused by high pressure has been associated with biotrauma in ARDS8Lan C.C. Huang H.K. Wu C.P. et al.Recruitment maneuver leads to increased expression of pro-inflammatory cytokines in acute respiratory distress syndrome.Respir Physiol Neurobiol. 2020; 271103284Crossref Scopus (2) Google Scholar and may lead to local inflammation in patients with low thoraco-pulmonary compliance during recruitment maneuvers that last only a few seconds, not much longer than MIE.9Ranieri V.M. Suter P.M. Tortorella C. et al.Effect of mechanical ventilation on inflammatory mediators in patients with acute respiratory distress syndrome: a randomized controlled trial.JAMA. 1999; 282: 54-61Crossref PubMed Scopus (1612) Google Scholar Last, the association between high-pressure MIE and upper airway closure must be considered cautiously both when determining treatment pressures and when interpreting monitoring data. Indeed, as suggested by the recent bench study of Terzi et al10Terzi N. Vaugier I. Guerin C. et al.Comparison of four mechanical insufflation-exsufflation devices: effect of simulated airway collapse on cough peak flow.Respir Care. 2023; 68: 462-469Crossref Scopus (2) Google Scholar (and as pointed out by Shah et al6Shah N.M. Apps C. Kaltsakas G. et al.The effect of pressure changes during mechanical insufflation-exsufflation on respiratory and airway physiology.Chest. 2024; 165: 929-941Abstract Full Text Full Text PDF Google Scholar), analysis of CPF only can lead to an overestimation of the cough efficiency, especially in the situation of upper airway closure. These findings hence raise the question of the reliability of a single outcome evaluation (usually CPF) when a clinician searches for the optimal pressures to be used during MIE. One important contribution of Shah et al6Shah N.M. Apps C. Kaltsakas G. et al.The effect of pressure changes during mechanical insufflation-exsufflation on respiratory and airway physiology.Chest. 2024; 165: 929-941Abstract Full Text Full Text PDF Google Scholar is the evaluation of several physiologic measurements in the same study, although CPF constitutes the main outcome of most of the previous studies (n = 10) with no or few considerations for physiologic outcomes such as lung recruitment, respiratory drive, upper airway flow, or even dyspnea relief.4Khan A. Frazer-Green L. Amin R. et al.Respiratory management of patients with neuromuscular weakness: an American College of Chest Physicians Clinical Practice Guideline and Expert Panel Report.Chest. 2023; 164: 394-413Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar Different responses to MIE therapy may also be expected depending on patient population and even patient physiopathologic condition (bulbar vs nonbulbar; with or without scoliosis).4Khan A. Frazer-Green L. Amin R. et al.Respiratory management of patients with neuromuscular weakness: an American College of Chest Physicians Clinical Practice Guideline and Expert Panel Report.Chest. 2023; 164: 394-413Abstract Full Text Full Text PDF PubMed Scopus (8) Google Scholar Although mechanical insufflation is expected to rise inspiratory tidal volume over spontaneous vital capacity to increase expiratory peak flows (to the minimal value of 160 to 200 L/min),11Bach J.R. Saporito L.R. Criteria for extubation and tracheostomy tube removal for patients with ventilatory failure: a different approach to weaning.Chest. 1996; 110: 1566-1571Abstract Full Text Full Text PDF PubMed Google Scholar CPF logically constitutes a mandatory measurement to ensure mucus expectoration. Yet, concurrent assessments of lung volume recruitment and/or upper airway closure seem to be additional required measurements in future studies that aim at the optimization of MIE parameters. Last, the question of the cost-effectiveness cannot be ignored. The meta-analysis of Morrow et al5Morrow B. Argent A. Zampoli M. Human A. Corten L. Toussaint M. Cough augmentation techniques for people with chronic neuromuscular disorders.Cochrane Database Syst Rev. 2021; 4: CD013170Google Scholar did not find clear differences when MIE was compared with other augmented cough techniques. Moreover, in previous short-term outcomes studies, the cost-effectiveness has never been discussed, and MIE seems to appear as one of the most expensive techniques.12Toussaint M. Chatwin M. Gonzales J. Berlowitz D.J. Consortium E.R.T. 228th ENMC International Workshop: airway clearance techniques in neuromuscular disorders Naarden, The Netherlands, 3-5 March, 2017.Neuromuscul Disord. 2018; 28: 289-298Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar Inexpensive techniques such as breath-stacking with the use of volume-preset ventilation or a manual resuscitator bag should be considered in comparison with MIE for cost-effectiveness evaluations.12Toussaint M. Chatwin M. Gonzales J. Berlowitz D.J. Consortium E.R.T. 228th ENMC International Workshop: airway clearance techniques in neuromuscular disorders Naarden, The Netherlands, 3-5 March, 2017.Neuromuscul Disord. 2018; 28: 289-298Abstract Full Text Full Text PDF PubMed Scopus (0) Google Scholar As a whole, the study of Shah et al6Shah N.M. Apps C. Kaltsakas G. et al.The effect of pressure changes during mechanical insufflation-exsufflation on respiratory and airway physiology.Chest. 2024; 165: 929-941Abstract Full Text Full Text PDF Google Scholar is an important contribution to the understanding of the mechanisms of action of MIE therapy, highlighting benefits and drawbacks of high pressures on cough efficiency, regarding lung derecruitment/recruitment, upper airway instability, and patient therapy compliance. Further studies are needed to identify physiologic mechanisms of improvements with MIE, which would include assessment of multiple physiologic outcomes in short-term and long-term evaluation. Larger multicenter and randomized trials will be necessary to finetune recommendations of this treatment modality in patients with neuromuscular disease. To paraphrase Milic-Emili13Milic-Emili J. Is weaning an art or a science?.Am Rev Respir Dis. 1986; 134: 1107-1108Google Scholar in the field of mechanical ventilation weaning, "the art of coughing" should include more scientific data in addition to the excellent work being done in this area to become a "science" of coughing. The authors have reported to CHEST the following: M. D. reports personal fees and nonfinancial support from Air Liquide Medical Systems, Breas Medical AB, and ResMed SAS, personal fees from GSK, and nonfinancial support from L3 Medical, ISIS Medical, and SOS Oxygene, outside the submitted work. F. L. reports grants from Vincent Medical and Fisher & Paykel, consulting fees from Medtronic, and honoraria from AARC 2023. F. L. has patent planned, issued, or pending for closed loop oxygen therapy. F. L. is cofounder and participates in the board of directors for OXYNOV and reports stock or stock options for OXYNOV. None declared (I. V.). The Effect of Pressure Changes During Mechanical Insufflation-Exsufflation on Respiratory and Airway PhysiologyCHESTVol. 165Issue 4PreviewHP-MIE did not lead to lung derecruitment or breathlessness compared with LP-MIE. However, it was poorly tolerated in individuals with advanced respiratory muscle weakness. HP-MIE generates more upper airway closure than LP-MIE, which may be missed if cough peak expiratory flow is used as the sole titration target. Full-Text PDF