Some<unk>  patients accustomed to relative hypoxia, thus higher oxygen levels may--> loss of hypoxic vasoconstriction-->increased shunt + increased alveolar dead space + haldane effect --> suppression of respiratory drive cause  high levels of oxygen may cause loss of hypoxic vasoconstriction causing areas of increased shunt and increased alveolar dead space along with the Haldane effect and suppression of the respiratory drive.
Do not withhold O2 if SpO2 <88%
Maintain PaO2 above 60 mmHg or SpO2 88-92%
SpO2 >93% associated with higher inpatient mortality
If unable to correct hypoxemia with a low FiO2 consider alternative diagnosis
Adequate oxygenation is essential, even if it leads to hypercapnia
If hypercapnia leads to altered mental status, dysrhythmias, or acidemia consider Intubation
Do not withhold O2 if SpO2 <88%
SpO2 >93% associated with higher inpatient mortality
Improves airflow obstruction and treatment should involve rapid administration upon recognition of<unk> . 
Similar efficacy between oral and intravenous. Treatment options include:
Hydrocortisone 100-125mg Q6H x 5 days
Methylprednisolone 1-2mg/kg IV daily (usual adult dose 125mg)
Prednisone 60mg x 1, then 40mg PO daily x 5 days
For outpatients a 5 day dose appears equally effective as longer doses and a taper is not required.
For outpatients a 5 day dose appears equally effective as longer doses and a taper is not required.
Mechanism: bronchial smooth muscle relaxation
Studies have found that while helpful in asthma, results are mixed for<unk> 
Indicated for patients with purulent sputum, increased sputum production, or requiring Non Invasive Positive Pressure Ventilation (NNT = 3 to prevent treatment failure and 8 to prevent death)
Antibiotics for<unk> s have an NNT of:
3:1 to prevent conservative treatment failure
8:1 to prevent short-term mortality
20:1 to cause diarrhea
3:1 to prevent conservative treatment failure
8:1 to prevent short-term mortality
20:1 to cause diarrhea

Antibiotics should be a 3-5 day course and options include:
Azithromycin 500mg PO once a day
Doxycycline 100mg PO BID
Levofloxacin 500mg PO Daily
Azithromycin 500mg PO once a day
Doxycycline 100mg PO BID
Levofloxacin 500mg PO Daily
Age >65, cardiac disease, >3<unk> s/per year
Levofloxacin, Moxifloxacin, OR Amoxicillin/Clavulanate
If Pseudomonas risk factors then use:
Levofloxacin PO or IV OR Cefepime IV OR Ceftazidime IV OR Piperacillin/Tazobactam IV
No pseudomonas risk factors:
Levofloxacin or Moxifloxacin PO or IV OR Ceftriaxone IV OR Cefotaxime IV
Consider oseltamivir during influenza season
Levofloxacin PO or IV OR Cefepime IV OR Ceftazidime IV OR Piperacillin/Tazobactam IV
Levofloxacin or Moxifloxacin PO or IV OR Ceftriaxone IV OR Cefotaxime IV
Consider oseltamivir during influenza season
CPAP: start at low level and titrate up to max 15
BiPAP: Start IPAP 8 (max 20), EPAP 4 (max 15)
Improves acidosis and ease respiratory distress
Contraindications:
Uncooperative or obtunded patient
Inability to clear secretions, high aspiration risk
Hemodynamic instability
Upper airway obstruction, craniofacial trauma, recent craniofacial surgery
Indications:
Severe dyspnea with use of accessory muscles and paradoxical breathing
RR>35 bpm with anticipated clinical course for respiratory failure
Respiratory arrest
PaO2 <50 or PaO2/FiO2 <200
pH <7.25 and PaCO2 >60
Altered mental status
Cardiovascular complications (hypotension, shock, CHF)
Noninvasive ventilation failure
Consider ketamine for sedation for intubation (in combination with paralytic) as ketamine has bronchodilatory effect
General principles for ventilator settings
Consider pressure control to prevent markedly elevated peak pressures
Maximize expiratory time by modifying I:E ratio
If patient with worsening hypercarbia, may benefit from paradoxically decreasing respiratory rate to improve expiratory time and improve gas exchange
COPD exacerbation
Pulmonary
Acute asthma exacerbation
Airway obstruction
Acute asthma exacerbation 
Anaphylaxis
Aspiration pneumonia and pneumonitis
Angioedema