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SUBJECT: Non-invasive Positive Pressure Ventilation (NPPV) using Bi-Level Positive Pressure Ventilation ("BiPAP"; Respironics, Inc.) for acute respiratory failure.

With acute respiratory failure, noninvasive positive pressure ventilation delivered by a facial or nasal mask may obviate the need for endotracheal intubation and thus preserve speech and the ability to eat, reduce trauma and infection, and possibly decrease the length of stay in the intensive care unit.6

A high continuous air flow pressure-limited ventilator such as the "Respironics" "BiPAP" may be better suited for NPPV than a volume limited ventilator because of its ability to compensate for mask leaks.6

PURPOSE:

Increased interest in NPPV for acute respiratory failure has been attributed to the successful adaptation of nasal continuous positive airway pressure (CPAP) masks used to treat obstructive sleep apnea for use in NPPV and studies using NPPV successfully in selected patients with chronic hypercapnic respiratory failure. CPAP differs from NPPV in that it provides a constant positive pressure, but not ventilatory assistance.
In acute respiratory failure due to exacerbations of chronic obstructive pulmonary disease (COPD) dynamic hyperinflation, intrinsic PEEP, and increased airway resistance result in a mechanical workload that exceeds inspiratory muscle capacity.8 NPPV has been hypothesized to decrease work of breathing by overcoming the effect of intrinsic PEEP on the inspiratory muscles, reduce inspiratory muscle effort, rest fatigued muscles, increase lung compliance, and prevent nocturnal hypoventilation, allowing resetting of respiratory sensitivity to CO2.10 NPPV provides augmentation of alveolar ventilation and respiratory muscle rest. It may be initiated during COPD exacerbations if arterial pH is less than 7.35 or if the patient is severely distressed.8
Noninvasive positive-pressure ventilation is a safe and effective means of ventilatory support for many patients with acute respiratory failure.14 Even those who for clinical or personal reasons are not candidates for intubation may still receive valuable help during a potentially reversible respiratory exacerbation.12 NPPV is generally well tolerated, and reduces complications.14
  1. Initiation of NPPV requires a physician’s order. The physician’s prescription may override some of the settings defined in the "PROCEDURE" section.

PROCEDURE:

  1. Assure that the patient has sufficient upper airway function and cough to protect their airways and does not have hemodynamic instability,6 significant arrhythmia, or anything that puts the patient at high risk of aspiration. If the patient does not meet these criteria contact the physician as the patient may need intubation. The candidate should also have an elevated PaCO213 and initially be intensively monitored.6
  2. Choose appropriate size mask. The mask should be as comfortable and as small as possible to minimize dead space. Position the mask so its upper portion rests at the low point where the nose meets the forehead.
  3. Assemble the circuit as per manufacturer’s instructions. In general, the circuit begins with the ventilator and continues through a low resistance bacteria filter, large bore tubing, known leak (with "Respironics" it is the "Whisper swivel"), oxygen bleed-in, and the mask with headgear. A passover humidifier, pressure tubing and alarm may also be included in the circuit.
  4. Initially set expiratory positive airway pressure (EPAP) at 5 cm H2O with IPAP of 10 to 20 cm H2O1,2,3,5 and titrate to achieve a respiratory rate less than 25 breaths/min1,5 and/or until the limit of patient tolerance for pressure is reached.7
  5. Observe the patient for excessive air leakage through the mouth. If this occurs, a chinstrap or a full-face mask may be tried.6
  6. Bleed in oxygen as necessary to achieve desired SaO2 (usually 91%). Oxygen should be bled into the circuit at the mask or as close to the mask as possible to minimize loss through the continuous leak (in the "Respironics" circuit the continuous leak is through the "Whisper swivel").
  7. Patient should be connected to continuous oximeter with the low SpO2 alarm set 1% or 2% below the desired patient SpO2. Assure the alarm volume is set high enough to alert the caregiver.
  8. If ventilator low-pressure alarms are used they should be set to within 5 cmH2O of the set pressure. Assure the alarm volume is set high enough to alert the caregiver.
  9. Stay with the patent and provide reassurance and possible mask/ventilator adjustments12 as the patient gets used to the system. Available trained caregiver time is necessary for successful use of noninvasive positive pressure ventilation.9,11
  10. Adjust settings to control symptoms while following arterial blood gases (ABG) results.1 Maintain a target arterial carbon dioxide tension in the range of 40 to 50+ mm Hg.6 In general, increasing the IPAP will increase the tidal volume and reduce the PaCO2; however, IPAP increases may be limited by patient intolerance. The EPAP assists in maintaining airway patency during expiration.6
  11. If the patient's condition fails to improve within 30 min, intubation and mechanical ventilation may be indicated.4

Sources/References:

  1. GU Meduri, RE Turner, N Abou-Shala, R Wunderink and E Tolley. Noninvasive positive pressure ventilation via face mask. First-line intervention in patients with acute hypercapnic and hypoxemic respiratory failure. 1996; Chest, Vol 109, 179-193
  2. T Celikel, M Sungur, B Ceyhan and S Karakurt. Comparison of noninvasive positive pressure ventilation with standard medical therapy in hypercapnic acute respiratory failure. Chest, Vol 114, 1636-1642.
  3. M Wysocki, L Tric, MA Wolff, H Millet and B Herman. Noninvasive pressure support ventilation in patients with acute respiratory failure. A randomized comparison with conventional therapy. 1995; Chest, Vol 107, 761-768.
  4. Janet M. Poponick, MD; Jeffrey P. Renston, MD, FCCP; Richard P. Bennett, BS, RRT and Charles L. Emerman, MD Use of a Ventilatory Support System (BiPAP) for Acute Respiratory Failure in the Emergency Department* Chest. 1999;116:166-171.
  5. Diaz O, Iglesia R, et al. Effects of Noninvasive Ventilation on Pulmonary Gas Exchange and Hemodynamics during Acute Hypercapnic Exacerbations of Chronic Obstructive Pulmonary Disease. Am. J. Respir. Crit. Care Med., Volume 156, Number 6, December 1997, 1840-1845.
  6. Meyer, Thomas J.; Hill, Nicholas S. Noninvasive Positive Pressure Ventilation to Treat Respiratory Failure [Review]; Annals of Internal Medicine; Volume 120(9) 1 May 1994 p.p.760-770.
  7. Mechanical Ventilation Beyond the Intensive Care Unit; Chest, 113(5), May 1998 Supplement, p.p.303S.
  8. Clark HE, Wilcox PG. Noninvasive positive pressure ventilation in acute respiratory failure of chronic obstructive pulmonary disease.[Review][59
    refs]; Lung. 175(3):143-54, 1997.
  9. Drinkwine J, Kacmarek RM. Noninvasive positive pressure ventilation. Equipment and techniques. [Review] [20 refs]. Respiratory Care Clinics of North America. 2(2):183-94, 1996 Jun.
  10. Jasmer, Robert M. MD; Luce, John M. MD, FCCP; Matthay, Michael A. MD, FCCP. Noninvasive Positive Pressure Ventilation for Acute Respiratory Failure*: Underutilized or Overrated? Chest; Volume 111(6) June 1997 pp 1672-1678.
  11. Hess DR Noninvasive positive pressure ventilation for acute respiratory failure. [Review] [50 refs]. International Anesthesiology Clinics. 37(3):85-102, 1999 Summer
  12. Rosenberg, Joseph I. MD; Goldstein, Roger S. MB, ChB, FCCP Noninvasive Positive Pressure Ventilation: A Positive View in Need of Supportive Evidence [Editorial] Chest; Volume 111(6) June 1997 pp 1479-1482
  13. Clinical Indications for Noninvasive Positive Pressure Ventilation in Chronic Respiratory Failure Due to Restrictive Lung Disease, COPD, and Nocturnal Hypoventilation - A Consensus Conference Report*. Chest ; Volume 116(2) August 1999 pp 521-534
  14. Hillberg, Robert E.; Johnson, Douglas C. Current Concepts: Noninvasive Ventilation [Review Articles] The New England Journal of Medicine; Volume 337(24) 11 December 1997 pp 1746-1752