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auto-PEEP

A build-up of positive-end-expiratory pressure (PEEP) that may occur during mechanical ventilation. Etiology: 1) compromised exhalation (high airway resistance) a) obstructive lung disease 1] asthma 2] COPD b) small or obstructed endotracheal tube c) long ventilator tubing d) ARDS (increased flow resistance) 2) high demand for ventilation (> 12-15 L/min) 3) short expiratory time 4) inverse ratio ventilation (IRV) Pathology: 1) excessive tidal volume &/or minute ventilation can result in auto-PEEP & high alveolar pressures 2) occurs when the expiratory phase is truncated prior to completion of exhalation 3) airflow still occurs at end-exhalation, resulting in positive pressure in the alveoli at end exhalation 3) auto-PEEP reduces cardiac output Clinical manifestations: 1) wheezing 2) marked expiratory prolongation 3) drop in blood pressure (hypotension) 4) restlessness Special laboratory: - pulmonary function testing - flow-volume loop on ventilator reveals continuous expiratory flow until the start of inspiratory flow Management: 1) disconnect the endotracheal tube from the ventilator & reconnect after a few seconds [2,5] - this allows for release of pulmonary pressure due to auto-PEEP - change settings to allow for more expiration time 2) treat airway obstruction 3) decrease respiratory rate or tidal volume 4) decrease peak inspiratory flow rate 5) allow permissive hypercapnia (best option for ALI, ARDS) 6) sedate or paralyze patient [2]

General

positive end-expiratory pressure (PEEP)

References

  1. Jon D. Hirasuna, M.D. Clinical Professor of Medicine, UC Davis, Associate Clinical Professor of Medicine, UCSF, Sept 1997
  2. Medical Knowledge Self Assessment Program (MKSAP) 14, 17, 18. American College of Physicians, Philadelphia 2006, 2015, 2018.
  3. Marini JJ Dynamic hyperinflation and auto-positive end-expiratory pressure: lessons learned over 30 years. Am J Respir Crit Care Med. 2011 Oct 1;184(7):756-62 PMID: 21700908
  4. Brochard L Intrinsic (or auto-) positive end-expiratory pressure during spontaneous or assisted ventilation. Intensive Care Med. 2002 Nov;28(11):1552-4. PMID: 12583374
  5. NEJM Knowledge_ Question of the Week. Nov 12, 2019 https://knowledgeplus.nejm.org/question-of-week/239/ - Ward NS, Dushay KM. Clinical concise review: Mechanical ventilation of patients with chronic obstructive pulmonary disease. Crit Care Med 2008 Apr 25; 36:1614 PMID: 18434881 - Pham T, Brochard LJ, Slutsky AS. Mechanical ventilation: state of the art. Mayo Clin Proc 2017 Sep; 92:1382. PMID: 28870355