Non-invasive positive pressure ventilation (NPPV) in the emergency unit.
Acute respiratory failure. The presence of 2 of the following 4 criteria indicates acute respiratory failure: (i) acute dyspnoea; (ii) arterial oxygen partial pressure ([P.sub.a][O.sub.2]) of less than 50 mmHg at room air; (iii) arterial carbon dioxide partial pressure ([P.sub.a]C[O.sub.2]) of more than 50 mmHg; and (iv) significant respiratory acidaemia. (2)
CPAP. Continuous positive airway pressure.
BiPAP. Bi-level positive airway pressure. It allows positive air pressure at two different levels--an inspiratory positive airway pressure (pressure support) and an expiratory airway pressure (positive end-expiratory pressure). These pressures are controlled and adjusted separately.
NPPV in the emergency unit
* Acute severe asthma not responding to conventional treatment. (3-5)
* Acute exacerbation of chronic obstructive pulmonary disease (COPD). (6)
* Near drowning. (7)
* Acute pulmonary oedema. (8)
* Severe thoracic trauma. (9,10)
* Severe pneumonia. (3)
* Restrictive airway disease with respiratory failure (e.g. neuromuscular disease). (1)
* When intubation is not indicated (terminal illness). (3)
NPPV requires an awake, co-operative patient who is haemodynamically stable. It should not be used with the gasping near-death patient.
* Hypotension (systolic BP < 90 mmHg).
* Confused, unco-operative or comatose patient.
* Respiratory arrest, or gasping patient.
* [P.sub.a][O.sub.2] < 60 mmHg or saturation < 90% on a rebreather mask.
* Uncontrolled cardiac ischaemia or arrhythmias.
* Inability of the patient to protect his/her airway.
* Persistent vomiting.
* Facial trauma or anatomical abnormalities of the face, which would prevent the mask from fitting correctly.
* Recent orofacial, oesophageal or gastric surgery.
* Patient's dyspnoea is relieved.
* Patient can talk and eat once stable, and requires less sedation.
* Intubation and its complications such as trauma and nosocomial infections can be avoided.
How it works
NPPV eases the work of breathing. Respiratory muscles are unloaded and therefore muscle fatigue is avoided. Oxygenation is improved by improving ventilation-perfusion mismatching, recruitment of collapsed alveoli and dilating bronchioles, and by forcing fluid out of the alveoli. (3)
Non-invasive ventilation should not be seen as a modality that reduces the nursing and monitoring requirements of the seriously ill patient. Patients on NPPV require strict monitoring of their vital signs, cardiac rhythm, dyspnoea, accessory muscle use and blood gas values. If there is no improvement of these signs after 30 minutes--2 hours, the patient should be considered for endotracheal intubation and mechanical ventilation.
In the emergency unit, CPAP or BiPAP are most commonly delivered via a full-face mask (see Figs 1-4). Because most patients feel claustrophobic when the mask is applied, they require assistance and calming during the early stages of therapy. Initially the mask is held to the patient's face and is not strapped onto him/her, as this worsens the sensation of claustrophobia. After a few minutes, as the patient becomes accustomed to the mask and starts to relax, the mask is then strapped to him/her. See Table I for the requirements and procedure of setting up a patient for NPPV.
[FIGURES 1-4 OMITTED]
(1.) Paolo P, Severgnini P, Aspesi M, et al. Non-invasive ventilation delivered by conventional interfaces and helmet in the emergency department. Eur J Emerg Med 2003; 10(2): 79-85.
(2.) Bone RC, Eubanks DH. The basis and basics of mechanical ventilation. Dis Mon 1991; 37: 321.
(3.) Hore CT. Non-invasive positive pressure ventilation in patients with acute respiratory failure. Emerg Med 2002; 14: 281-295.
(4.) Meduri GU, Cook TR, Turner RE, Cohen M, Leeper KV. Noninvasive positive pressure ventilation in status asthmaticus. Chest 1996; 110: 767-774.
(5.) Rodrigo GJ, Rodrigo C, Hall JB. Acute asthma in adults. A review. Chest 2004; 125(3): 1081-1102.
(6.) COPD Guideline Working Group of South African Thoracic Society. Guideline for the management of chronic obstructive pulmonary disease (COPD): 2004 revision. S Afr Med J 2004; 94(7): 559-587.
(7.) Moon RE, Long RJ. Drowning and near drowning. Emerg Med 2002; 14: 377-386.
(8.) Peter JV, Morn JL, Phillips-Hughes J, Graham P, Bersten A. Effect of non-invasive positive pressure ventilation (NIPPV) on mortality in patients with acute cardiogenic pulmonary oedema: a meta-analysis. Lancet 2006; 367: 1155-1163.
(9.) Gunduz M, Unlungenic H, Ozalevil M, Inanoglu K, Akman H. A comparative study of continuous positive airway pressure (CPAP) and intermittent pressure ventilation (IPPV) in patients with flail chest. Emerg Med J 2005; 22: 325-329.
(10.) Garfield MJ, Howard-Griffi n RM. Noninvasive positive pressure ventilation for severe thoracic trauma. Br J Anaesth 2000; 85(5): 788-790.
(11.) Cummins RO, Field JM, Hazinski MF, et al. The Reference Textbook. ACLS for Experienced Providers. Dallas: American Heart Association, 2003: 111-125.
(12.) Marik PE, Varon J, Fromm R. The management of acute severe asthma. J Emerg Med 2002; 23(3): 257-268.
LOUISE ENGELBRECHT, MB ChB, MMed (Fam Med), Dip PEC
Senior Specialist and Senior Lecturer, Kalafong Hospital Emergency Unit, Department of Family Medicine, University of Pretoria
ANDREAS ENGELBRECHT, MB ChB, MMed (FamMed), Dip PEC, DA
Principal Specialist and Head, Emergency Unit, Pretoria Academic Hospital Department of Family Medicine, University of Pretoria
Table I. Setting up a patient for NPPV (5,11) Requirements * A ventilator that has non-invasive ventilation modes, or a dedicated CPAP or BiPAP ventilator * Cardiac monitor * Non-invasive blood pressure monitoring * Oximeter * One nurse per patient for serial vital signs measurement and continued observation * Patient lies at a > 45[degrees] angle. Procedure Pressure settings * Set expiratory positive pressure, CPAP or positive end-expiratory pressure (PEEP) at 3-5 cm * Set inspiratory pressure (or pressure support) at 8-10 cm * Inspiratory pressure should be set higher than expiratory pressure * If the patient has difficulty during inspiration, triggering breaths, increase the expiratory positive airway pressure * If tidal volumes are shallow (< 7 ml/kg), increase inspiratory pressures * In hypoxic patients, increase the expiratory pressure at increments of 2 cm [H.sub.2]O, keeping the inspiratory pressure constant * In patients with hypercapnia, increase the inspiratory pressure at increments of 2 cm [H.sub.2]O, increasing the expiratory pressure at 1 cm [H.sub.2]O for every 2.5 cm increase in the inspiratory pressure * Total pressures > 15-20 cm will rarely be tolerated * [F.sub.1][O.sub.2] is titrated to achieve [S.sub.a][O.sub.2] of more than 90% Connect oxygen Apply headgear Check for air leaks If required, continue nebulisations Continue monitoring of vital signs and clinical response Episodic removal of mask or reduction of pressures can be attempted when improvement is significant and has persisted for [+ or -] 4 hours
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|Title Annotation:||More about ... Emergency medicine|
|Author:||Engelbrecht, Louise; Engelbrecht, Andreas|
|Publication:||CME: Your SA Journal of CPD|
|Article Type:||Clinical report|
|Date:||Mar 1, 2007|
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