CPAP

Question 1

what is CPAP

Answer 1

Continuous positive airway pressure (CPAP) is a type of positive airway pressure that is used to deliver a set pressure to the airways. The pressure is maintained throughout the respiratory cycle, during both inspiration and expiration.

Question 2

The application of CPAP maintains

Answer 2

positive end expiratory pressure (PEEP), can decrease atelectasis, increases the surface area of the alveoli, improves V/Q matching, and hence improves oxygenation.

Question 3

the positive pressure from CPAP causes

Answer 3

assists small and medium sized airways to remain open during expiration, reducing lung collapse. This also may aid expiration in patients with bronchospasm by reducing dynamic hyperinflation.

reduces the work of breathing, so less work is required during inspiration,

reduces the preload (filling) of the right ventricle by reducing venous return to the heart from the positive pressure in the thoracic cavity

increases the afterload of the right ventricle, reducing blood flow through lung vessels, and reducing the amount of fluid entering the lungs.

Question 4

the expiratory pressure from CPAP causes

Answer 4

increases the amount of air remaining in the lungs at the end of expiration, (the functional residual capacity) causing the lungs to be more expanded. From this more expanded resting position, less work is required for inspiration because of the non-linear compliance of the lungs, particularly when the lungs are wet.

Question 5

CPAP indications

Answer 5

Cardiogenic pulmonary oedema with moderate to severe respiratory distress.
Asthma, COPD, or undifferentiated respiratory problem with severe respiratory distress that is not improving with treatment.
An SpO2 of less than 92% due to a respiratory problem despite treatment (less than 88% if COPD or known chronic hypoxia).

Question 6

Cardiogenic pulmonary oedema (CPO) is characterized by

Answer 6

the presence of excess fluid within the pulmonary interstitium and, at its most severe, within the alveoli. CPO is pulmonary oedema due to a primary cardiac or circulatory cause rather than other forms of pulmonary oedema (e.g. neurogenic pulmonary oedema).

Question 7

how CPAP helps in CPO

Answer 7

CPAP augments the inspiratory and expiratory flow, and pressure thereby increasing tidal volume and unloading the inspiratory muscles. It also decreases dead space ventilation, improves alveolar ventilation, re-expands flooded alveoli, and counteracts intrinsic PEEP. CPAP prevents micro atelectasis (microscopic collapse of alveoli), and places the respiratory pressure volume characteristics in a more favourable position

Question 8

CPAP is contraindicated if the patient has:

Answer 8

Active vomiting

Ineffective breathing

Also assess the risk of using CPAP in the patient who has

Inability to protect airway with impaired cough or swallowing

Poor clearance of secretions

Gastrointestinal (GI) bleeding with intractable emesis and/or uncontrollable bleeding

Status epilepticus

Potential for upper airway obstruction

Anaphylaxis

Severe facial burns

Tracheal injuries

Maxillofacial or basilar skull fractures

Recent facial or throat surgery

Question 9

Use CPAP with caution if the patient has:

Answer 9

Altered level of consciousness

Signs of shock

Clinical suspicion of pneumothorax

Question 10

Application of CPAP

Answer 10

Commence at 5 cmH2O.

Increase to 10 cmH2O if it is being tolerated.

Consider increasing to 15 cmH2O if the patient is not improving.