Positive airway pressure

A mode of respiratory ventilation used primarily in the treatment of sleep apnea.

CPAP is an acronym for continuous positive airway pressure.

Commonly used for those who are critically ill in hospital with respiratory failure, and in newborn infants.

Can prevent the need for tracheal intubation, or allow earlier extubation.

Can be used in patients with neuromuscular diseases.

CPAP machine houses the air pump in a case lined with sound-absorbing material for quieter operation. A hose carries the pressurized air to a face mask or nasal pillow.

Indications for positive airway pressure include congestive heart failure and chronic obstructive pulmonary disease.

Can be used in patients with hypoxia and community acquired pneumonia.

Often used for patients who have acute type 1 or 2 respiratory failure.

Usually this type of ventilation reserved for patients for whom oxygen delivered via a face mask is insufficient or deleterious to health.

Utilization requires close monitoring.

Used to assist premature babies with breathing.

Not used when the airway may be compromised, or consciousness is impaired.

The mask utilized requires an effective seal.

Patient intolerance occurs in about 20% of cases.

Used to improve the ability of the lungs to exchange oxygen and carbon dioxide, and to decrease the work of breathing with inspiratory positive airway pressure that forces air into the lungs decreasing work load, and prevents airways from collapsing at the end of expiration recruitment.

When small airways and alveoli collapse, significant pressures are required to re-expand them: Young–Laplace equation.

Collapsed regions of lung will have some blood flow, but are not being ventilated, and the blood passing through these areas is not able to efficiently exchange oxygen and carbon dioxide resulting in a ventilation–perfusion mismatch (or V/Q).

Recruitment by PAP reduces ventilation–perfusion mismatch by increasing the functioning residual capacity, the amount of air remaining in the lungs at the end of a breath.

From this more expanded resting position, less work is required to inspire and is due to the non-linear compliance–volume curve of the lung.

Disadvaqntages include: noncompliance, nasal congestion, rhinitis, sinus infection, ear pain, eustachion tube infection, obstruction, temporal-mandibular dysfunction, and rhinorrhea.

Beards, mustaches, or facial irregularities may prevent an air-tight seal,and the skin must be free from dirt and chemicals such as skin oils to insure a good mas fit.

CPAP machine improves sleep apnea by delivering a stream of compressed air so that unobstructed breathing becomes possible, and reduces and prevents apnea and hypopnea.

CPAP and PEEP stent the lungs’ alveoli open and thus recruit more of the lung’s surface area for ventilation, but, while PEEP refers to devices that impose positive pressure only at the end of the exhalation, CPAP devices apply continuous positive airway pressure throughout the breathing cycle. 

Positive end-expiratory pressure (PEEP) is used in mechanically-ventilated patients to improve oxygenation.

The recruitable aveoli are those that can can be recruited with minimal PEEP, and others which can only be recruited with high levels.

High PEEP increases mean airway pressure and alveolar pressure and can damage normal alveoli by overdistension.

Air pressure, and not the movement of the air, prevents the apneas and reduces or eliminates loud snoring that sometimes accompanies sleep apnea.

The CPAP machine blows titrated pressure and it is usually measured in centimetres of water.

The pressure required by most patients with sleep apnea ranges between 6 and 14 cmH2O.

An automatic positive airway pressure device titrates the amount of pressure delivered to the patient to the minimum required to maintain an unobstructed airway on a breath-by-breath basis by measuring the resistance in the patient’s breathing.

BPAP stands for bilevel positive airway pressure and is a breathing apparatus developed from the CPAP.

Variable/bilevel positive airway pressure provides two levels of pressure: inspiratory positive airway pressure (IPAP) and a lower expiratory positive airway pressure (EPAP) for easier exhalation.

BPAP is incorrectly referred to as “BiPAP”, the name of a portable ventilator.

When in the spontaneous mode the device triggers IPAP when flow sensors detect spontaneous inspiratory effort and then cycles back to EPAP.

When In timed mode the IPAP/EPAP cycling is triggered, at a set rate, expressed in breaths per minute.

In a Spontaneous/Timed mode, the device triggers to IPAP on patient inspiratory effort, a backup rate is also set to ensure that patients still receive a minimum number of breaths per minute if they fail to breathe spontaneously.

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