Consensus Statement on SARS Guideline

Practice Standards of Respiratory Procedures: Post SARS Era
Noninvasive Positive Pressure Ventilation

Introduction

Noninvasive positive pressure ventilation (NIPPV) is being increasingly used in treating respiratory failure because of its proven effectiveness in acute and chronic respiratory failure from many causes, and because of the associated reduction of endotracheal intubation and invasive mechanical ventilation, and therefore the potential complications attributable to the latter procedures. Considerations regarding the potential generation of aerosols during NIPPV usage in infectious lung disease have, however, resulted in concerns for the safety of health care workers during its application. Special precautions which may be useful to reduce infection risks for health care workers should thus be taken in case NIPPV is applied to such patients.

Indications

Acute respiratory failure

There is good evidence for the use of NIPPV in the treatment of acute respiratory failure secondary to COPD, decreasing mortality, need of endotracheal intubation and length of hospital stay. In non-COPD patients, NIPPV can also decrease the need for endotracheal intubation.

Strong evidence (multiple controlled trials)

  • COPD
  • Acute cardiogenic pulmonary oedema
  • Immunocompromised patients

Less strong evidence (single controlled trial or multiple case series)

  • Pneumonia
  • Asthma
  • Postoperative respiratory failure
  • Avoidance of extubation failure
  • “Do not intubate” patients

Weak evidence (few case series or case reports)

  • Upper airway obstruction
  • Acute respiratory distress syndrome
  • Trauma
  • Obstructive sleep apnoea, obesity hypoventilation

Controversy

The use of NIPPV in SARS is controversial as its potential risk of aerosol generation which may endanger the health care workers. A Canadian study reported a non-significant association for SARS transmission and NIV (1/6 exposed HCW against 2/28 non-exposed, risk ratio 2.33, p=0.5) but a much higher and statistically significant risk ratio (13.29 in 6/14 exposed HCW against 2/62 non-exposed, p=0.003) for intubation. Despite this, NIV is till being recommended to be avoided in SARS. However, from the Chinese literature, there was no reported increase in staff infection following the application of NIPPV in SARS patients. From the experience of NIPPV usage in more than 20 SARS patients in a Hong Kong hospital, 102 out of over 105 health care workers who had taken care of these SARS patients and who consented to have their blood checked were negative for coronavirus serology.

Chronic respiratory failure

NIPPV is also indicated as a long-term ventilatory support for patients suffering from chronic respiratory failure secondary to restrictive lung disease due to neuromuscular or chest wall disease, sleep-related breathing disorders and COPD.

Contraindications

NIPPV is contraindicated in the following conditions:

  • Cardiorespiratory arrest/patients unable to sustain spontaneous breathing
  • Cardiorespiratory instability (e.g. hypotension with impaired perfusion, serious dysrrhythmia)
  • Uncooperative patients
  • Recent facial, oesophageal, or gastric surgery
  • Craniofacial trauma or burns
  • High aspiration risk (inability to manage secretion)
  • Inability to protect airway
  • Fixed anatomic abnormalities of the nasopharynx (e.g. choanal atresia, severe laryngomalacia)

Environmental requirement

No potentially infectious disease

  • Adequate air change of at least 6 shifts per hour (6 ACH).

Potentially infectious disease including SARS

  • Required: Air change of at least 12 shifts per hour (12 ACH) achieved by negative pressure ventilation, with HEPA filters for incoming and outgoing air (to protect the environment and to allow recirculation), and
  • Preferred: Uni-directional airflow from clean areas to the patient and finally out to the atmosphere through the exhaust.

Personal protective equipment

No potentially infectious disease

  • N-95/surgical mask
  • Protective eyewear, full-face shield, surgical gloves, cap and gown for potentially aerosol generating procedures.

Potentially infectious disease including SARS

  • N-95/surgical mask, protective eyewear, full-face shield, cap, gown and surgical gloves.

NIPPV application for SARS and with due regard to reducing environmental spread of infective droplets

  1. Ventilator Settings
    1. Machine with differential inspiratory positive pressure (iPAP) and expiratory positive pressure (ePAP)
      • Spontaneous/timed ( ST ) mode preferred with back-up rate 12 breaths/min
      • iPAP to be set to achieve respiratory rate less than 25 breaths/min and tidal volume at 6-7ml/kg
      • O2 and ePAP to be set to achieve minimal CO2 re-breathing and target oxygenation
      • Facial mask preferred to decrease aerosol generation
      • Exhalation port with round - the - tube outflow preferred
      • As far as possible and provided the patient can tolerate, v iral-bacterial filter to be placed between the mask and the exhalation port to decrease viral and bacterial load excretion to the environment
    2. Mechanical ventilator
      • Pressure support mode is to be used, preferably with capability for leak compensation.
      • Pressure support level to be set to achieve respiratory rate less than 25 breaths/min and tidal volume 6-7ml/kg.
      • CPAP level and FiO2 to be set to achieve target oxygenation.
      • Facial mask preferred to decrease aerosol generation.
      • Viral-bacterial filter to be added at the entry of the expiratory tubing to the ventilator to decrease discharge of viral and bacterial loads to the environment.
      • Heat and moisture exchanger s (HME) are likely to be contaminated and must be handled with care.

    Special notes for NIPPV setting in SARS

    • In general, settings for SARS patients are the same as for the usual non-SARS induced Type I acute respiratory failure (ARF). However, pneumomediastinum and pneumothorax are common, and ARF due to SARS frequently responds to low positive pressures. The following ranges are thus appropriate as initial settings:
      • CPAP      4-6cm
      • IPAP      6-10cm
      • EPAP      4-6cm
    • All volume & rate requirements and use of viral/bacterial filters for potentially infectious diseases apply.
  2. Indications for initiation of NIPPV

    NIPPV should be started early in patients presented with respiratory failure, defined as SaO2 < 95% on nasal O2 5L/min and respiratory rate more than 30/min

  3. Monitoring
    • All patients should be maintained continuously on NIPPV for at least 6 hours after commencement.
    • NIPPV can be stopped for not more than 30 minutes at a time thereafter for meals and sputum clearance.
    • Close monitoring of respiratory rate (RR), signs of respiratory distress, supplemental oxygen requirement, oxygen saturation and actual blood gas (ABG) is mandatory.
    • Patients should be intubated if there is increase in respiratory distress and/or SaO2 < 95% with increasing oxygen requirement e.g. more than 10-12L/min or FiO2 > 0.4-0.5.
    • If patients show improvement in terms of respiratory rate and supplemental oxygen requirement, gradual weaning from NIPPV can be tried, starting with day time weaning.

Cleaning and disinfection

No potentially infectious disease

  • Tubings and mask should be cleaned at least weekly or prn for the same patient
  • Used tubings and mask should be soaked in 1000 ppm pre-sept for at least 30 minutes

Potentially infectious disease including SARS

  • Disposable tubings should be utilized for single patient application.
  • Used masks should be soaked in 1000 ppm pre-sept for at least 30 minutes

References

  1. American Respiratory Care Foundation ‘Consensus conference: Noninvasive positive pressure ventilation.' Resp Care 1997; 42: 364-8.
  2. British Thoracic Society Standards of Care Committee ‘Non-invasive ventilation in acute respiratory failure.' Thorax 2002; 57: 192-211.
  3. Consensus Conference ‘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 1999; 116: 521-34.
  4. Peter JV, Moran JL, Philips-Hughes J et al. ‘Noninvasive ventilation in acute respiratory failure – A meta-analysis update.' Crit Care Med 2002; 30: 555-62.
  5. Liesching T, Kwok H, Hill NS. ‘Acute application of noninvasive positive pressure ventilation.' Chest 2003; 124: 699-713.
  6. Fowler RA, Guest CB, Lapinsky SE, Sibbald W, Louie M, Tang P et al. Transmission of severe acute respiratory syndrome during intubation and mechanical ventilation. Am J Respir Med Crit Care 2004; 169: 1198-1202.
  7. Manocha S, Walley KR, Russell JA, Severe acute respiratory syndrome (SARS): a critical care perspective. Crit Care Med 2003; 31: 2684-2692.
  8. Lapinsky SE, Hawryluck L. ICU Management of severe acute respiratory syndrome. Intensive Care Med 2003; 29:870-875.
  9. Lim WS, Anderson SR, Read RC on behalf of the SARS guidelines committees of the British Thoracic Society, the British Infection Society and the Health Protection Agency. Hospital management of adults with severe acute respiratory syndrome (SARS) if SARS re-emerges – Updated 10 Feb 2004. Accessed at http://www.brit.thoracic.org.uk/docs/sars0304.pdf
  10. Peiris JSM, Chu CM, Cheng VCC et al. ‘Clinical progression and viral load in a community outbreak of coronavirus-associated SARS pneumonia: a prospective study.' Lancet 2003; 361: 1767-72.
  11. Xiao ZL, Li YM, Chen RC, Li SY, Zhong SQ, Zhong NS. ‘A retrospective study of 78 patients with severe acute respiratory syndrome.' Chin Med J 2003; 116: 805-810.
  12. Centers for Disease Control and Prevention. ‘Interim domestic infection control precautions for aerosol-generating procedures on patients with severe acute respiratory syndrome (SARS). Access ed at http://www.cdc.gov/ncidod/sars/index.htm

The information and opinions expressed in these guidelines are provided to the best of our knowledge and understanding at the time of updating (First draft January 2004. Updated Feb 2005), and must be cross-referred to the most updated literature upon application.

 
 
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