This document discusses respiratory failure and the use of high flow nasal cannula (HFNC) and bilevel positive airway pressure (BiPAP). It describes the three types of respiratory failure - inability to oxygenate, inability to ventilate, and inability to protect airway. HFNC provides high flow oxygen but no positive pressure, while BiPAP provides adjustable inspiratory and expiratory pressures for both oxygenation and ventilatory support. The document reviews indications, advantages, disadvantages, settings and monitoring for BiPAP use in treating respiratory failure.

1. Respiratory Failure-When to Use
HFNC and/or BiPAP
Steven Podnos MD

2. Three Types of Respiratory Failure
• Definition: Inadequate Gas Exchange
• Three types:
• Inability to Oxygenate
• Inability to Ventilate
• Inability to Protect Airway-never candidates
for noninvasive ventilation!

3. Inability to Oxygenate
• Implies that alveoli are not exchanging gases-usually
hypoxemia. Can be V/Q mismatch or true shunt
• Alveoli are filled with fluid-CHF, Non Cardiogenic Pulm
Edema (ARDS), infected fluid (pneumonia)
• Rx O2 to keep sat 90% or better
• If unable to maintain sats with face mask/Nasal cannula-
need HFNC, positive pressure like BiPAP or intubation
• Usually increased work of breathing-patients may tire and
develop hypercapnia (high pCO2)
• Rx underlying condition: diurese CHF, supportive for
ARDS, antibiotics for infection

4. Inability to Ventilate
• Abnormalities in lung (or external) mechanics. Hallmark is hypercapnia. Elevated pCO2 displaces O2, but
hypoxemia easy to treat. May be intrinsic to lung (COPD), or extrinsic (OD, neuromuscular disease)
• Alveoli are “OK” in general
• Common causes of type II (hypercapnic) respiratory failure
• Chronic bronchitis and emphysema (COPD)
• Severe asthma
• Drug overdose
• Poisonings
• Myasthenia gravis
• Polyneuropathy
• Poliomyelitis
• Primary muscle disorders
• Porphyria
• Cervical cordotomy
• Head and cervical cord injury
• Primary alveolar hypoventilation
• Obesity hypoventilation syndrome
• Pulmonary edema
• Adult respiratory distress syndrome
• Myxedema
• Tetanus
• (note overlap with failure to oxygenate)

5. Treatment of Respiratory Failure:
• Airway
• Oxygenation
• Aerosol bronchodilators
• Diuretics
• Antibiotics
• Supportive Rx for Hypercapnia is Positive Pressure
Ventilation (external or with ETT)
• Steroids for bronchospasm
• DVT, GI bleed prophylaxis
• O2 toxicity-including risk of worsening hypercapnia

6. Monitoring of Treatment
• RR, HR
• O2 sat
• ABG mostly useful for pCO2, acid-base status
• Mental Status

7. HFNC

8. High Flow Nasal Cannula
• In infants, high flow Nasal Cannula appears to have
some positive pressure benefit and may be equivalent
to Nasal CPAP in efficacy
• In Adults, allows higher concentration of inspired
oxygen than a traditional nasal cannula. Flows at
35L/min appear to provide low levels of positive
pressure (CPAP), especially with a closed mouth.

9. HFNC or BiPAP in Adults
• If the patient requires positive pressure
ventilation, choose BiPAP.
• If they patient primarily requires a high level
of inspired oxygen (CHF, ARDS without
fatigue), then HFNC may be adequate

11. Non Invasive Ventilation
• Using positive pressure ventilation without an
endotracheal tube
• Used for Obstructive Sleep Apnea, Respiratory
Support of various illnesses to prevent
intubation

12. CPAP
• Continuous Positive Airway Pressure-usually a
set level pressure-same with inspiration and
expiration. Note that Expiratory Pressure is
the same thing as PEEP (Positive End
Expiratory Pressure). Normal PEEP is zero!

13. BiPAP vs. CPAP
• Individually set Inspiratory and Expiratory
Pressures. Can also adjust timing of I/E
• Indicated for difficulty with Oxygenation
(EPAP/PEEP) and/or Respiratory muscle
support (IPAP)
• Contraindications: Risk of
Aspiration, Agitation, Poor cough, lack of
cooperation

14. Indications
• Suitable clinical conditions for noninvasive ventilation (most patients)
Chronic obstructive pulmonary disease
• Cardiogenic pulmonary edema
• Suitable clinical conditions for noninvasive ventilation (selected patients)
After discontinuation of mechanical ventilation (COPD)
• Community-acquired pneumonia (and COPD)
• Asthma
• Immunocompromised state
• Postoperative respiratory distress and respiratory failure
• Do-not-intubate status
• Neuromuscular respiratory failure
• Decompensated obstructive sleep apnea/cor pulmonale
• Cystic fibrosis
• Acute respiratory distress syndrome

15. Advantages of BiPAP
• May reverse impending respiratory failure and
avoid intubation
• Reduced risk of nosocomial pneumonia
• Buys time while reversing hypercapnia and
cardiogenic pulmonary edeama

16. Disadvantages of BiPAP
• Complications of noninvasive ventilation
• Facial and nasal pressure injury and sores
– Result of tight mask seals used to attain adequate inspiratory volumes
– Minimize pressure by intermittent application of noninvasive ventilation
– Schedule breaks (30-90 min) to minimize effects of mask pressure
– Balance strap tension to minimize mask leaks without excessive mask pressures
– Cover vulnerable areas (erythematous points of contact) with protective dressings
• Gastric distension
– Rarely a problem
– Avoid by limiting peak inspiratory pressures to less than 25 cm water
– Nasogastric tubes can be placed but can worsen leaks from the mask
– Nasogastric tube also bypasses the lower esophageal sphincter and permits reflux
• Dry mucous membranes and thick secretions
– Seen in patients with extended use of noninvasive ventilation
– Provide humidification for noninvasive ventilation devices
– Provide daily oral care
• Aspiration of gastric contents
– Especially if emesis during noninvasive ventilation
– Avoid noninvasive ventilation in patient with ongoing emesis or hematemesis
• Complications of both noninvasive and invasive ventilation
Barotrauma (significantly less risk with noninvasive ventilation)
• Hypotension related to positive intrathoracic pressure (support with fluids)

17. BiPAP Settings
• Typically begin with 10cm Inspiratory and 5cm
Expiratory Pressures. Adjust as needed for
support and hypoxemia.
• Remember, EPAP = PEEP
• PEEP paradoxically can help with both Shunt
and Obstructive Disease

18. Use in COPD

19. Monitoring BiPAP
• Look at Patient-HR, RR, BP
• Increasing pCO2 a bad sign
• Worsening Hypoxemia a bad sign

20. Weaning BiPAP
• May slowly reduce both inspiratory and
expiratory pressures
• May alternatively just switch to simple
supplemental Oxygen

21. Conclusions
• Three types of Respiratory Failure
• Non-invasive ventilatory support is usually
worth considering
• HFNC is oxygenation support only
• BiPAP is both ventilatory and oxygenation
support