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- Airflow obstruction is defined as a value of <0.7 when a ratio of the FEV1 (Forced expiratory volume in 1 second) / FVC (Forced vital capacity) is measured.
medical treatment
- Controlled oxygen therapy to maintain SaO2 88-92%
- Nebulised salbutamol 2.5-5 mg
- Nebulised Ipratropium 500 micrograms
- Prednisolone 30 mg
- Antibiotic agent (when indicated)
GOLD Indications for NIV include:
- pH <7.35 and a PaCO2 >6kPa or 45mmHg
- Severe dyspnea with clinical signs suggestive of muscle fatigue, increases work of breathing, such as use of respiratory muscles, paradoxical motion of the abdomen, or retraction of the intercostal spaces.
- Persistent hypoxaemia, despite supplemental oxygen therapy
Setting
- An initial Inspiratory Positive Airway Pressure (IPAP) of 10 cm H20 and Expiratory Positive Airway Pressure (EPAP) of 4-5 cm of water should be used. This should be increased rapidly at a rate of approximately 5 cm of water every 10 minutes to a target of 20 cm H2O (IPAP), or patient unable to tolerate further, or therapeutic response achieved
- Arterial blood gas (ABG) analysis should be performed at baseline, 1 hour after commencing NIV, 4 hours after commencing NIV, and 1 hour after changing any settings
Indications for invasive mechanical ventilation:
- A decision to intubate and proceed with mechanical ventilation should normally be made within 4 hours of starting NIV, as improvements should usually be apparent during this time
- Patients with COPD should be considered for ITU treatment when necessary , especially if they are more unwell i.e. pH < 7.26
Prognosis
- One cohort study has shown that predictors of increased mortality in COPD include:
- Increasing age
- Significant co-morbidity
- Decreasing post bronchodilator FEV1
- Those patients already on long term oxygen therapy
- Increased number of COPD exacerbations, particularly those with 3 or more episodes
- Increased number of hospital admissions
- A further UK audit has shown death in 14% of patients admitted to hospital within 3 months of admission. The most important prognosticators for death in this group were:
- Poor performance status*
- Low arterial pH on admission*
- Presence of bilateral leg oedema*
- Age >70
- Home circumstances, particularly if the patient is in a nursing home
- Unrecordable peak flow on admission
- Pulse oximetry showing oxygen saturation under 86%
- Intervention with assisted ventilation
- The 3 marked with * were the 3 major independent predictors of mortality.
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