C-PAP: differenze tra le versioni

Versione delle 19:47, 7 dic 2008

Versione delle 23:41, 10 dic 2008

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{{T|lingua=inglese|argomento=medicina|data=dicembre 2006}}

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La '''ventilazione meccanica a pressione positiva delle vie aeree''' (in [[lingua inglese|inglese]] '''PAP''', [[acronimo]] di '''Positive airway pressure''') è un metodo di [[ventilazione meccanica|ventilazione respiratoria]] utilizzato principalmente nel trattamento delle [[apnee nel sonno]], sistema per il quale in principio venne sviluppato.

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La maggior parte dei produttori raccomandano che il consumatore finale esegua la manutenzione settimanale. Le unità devono essere controllate regolarmente per il deterioramento materiale e devono essere tenute pulite. Collegamenti elettrici consumati o logorati possono presentare il rischio di scosse elettrice o di incendio; tubi e maschere consumate possono ridurre l'efficacia dell'unità. La maggior parte di queste si servono di alcuni modelli di filtraggio, e i filtri quindi devono essere puliti o sostituiti secondo un regolare programma. Nei tubi e nelle maschere inoltre si accumulano pelle squamata, polveri sottili, e può anche svilupparsi della muffa. Le unità di umidificazione devono essere tenute prive di muffa ed alghe. Poiché le unità usano l'energia elettrica di base, le abitazioni devono essere pulite senza immersione.

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==Travelling==

Poiché una costante conformità è un importante fattore nel successo di una cura, è necessario che i pazienti che viaggiano abbiano pieno accesso ad attrezzature portatili. Progressivamente, le unità PAP stanno diventando sempre più chiare e compatte, e spesso si trovano anche con custodie per il trasporto.

==Care and maintenance==

As with all durable medical equipment, proper maintenance is essential for proper functioning, long unit life and patient comfort. The level of care and maintenance required for PAP machines varies with the type and conditions of use, and are typically spelled in a detailed instruction manual specific to the make and model.

Most manufacturers recommend that the end user perform weekly maintenance. Units must be checked regularly for wear and tear and kept clean. Worn or frayed electrical connections may present a shock or fire hazard; worn hoses and masks may reduce the effectiveness of the unit. Most units employ some type of filtration, and the filters must be cleaned or replaced on a regular schedule. Hoses and masks accumulate exfoliated skin, particulate matter, and can even develop mold. Humidification units must be kept free of mold and algae. Because units use substantial electrical power, housings must be cleaned without immersion.

==Travelling==

Since continuous compliance is an important factor in the success of treatment, it is of importance that patients who travel have access to portable equipment. Progressively, nPAP units are becoming lighter and more compact, and often come with carrying cases. Dual-voltage power supplies permit many units to be used internationally.

Air travel presents special considerations. Most airport security inspectors have seen the portable machines, so screening rarely presents a special problem. Increasingly, machines are capable of being powered by the 400 Hz power supply used on most commercial aircraft and include manual or automatic altitude adjustment.

Some nPAP patients also use supplementary [[oxygen]]. When provided in the form of bottled gas, this can present an increased risk of [[fire]] and is subject to restrictions. As of November, 2006, most airlines permit the use of [[oxygen concentrator]]s.

==Availability==

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In many countries, PAP machines are only available by prescription. A sleep study at an accredited sleep lab is usually necessary before treatment can start. This is because the pressure settings on the PAP machine must be tailored to a patient's treatment needs. A doctor, who may be a [[Pulmonology|Respiratory Medicine]], [[Otolaryngology|Ear Nose and Throat (ENT)]] or [[Neurology]] specialist, will interpret the results from the initial sleep study and estimate the correct pressure from experience. This is later confirmed with a follow up sleep study during which the patient wears the CPAP mask and pressure is adjusted up and down from the prescribed setting to find the optimal setting.

* In the [[United States]], PAP machines are often available at large discounts online, but a patient purchasing a PAP personally must handle the responsibility of securing reimbursement from his or her insurance provider. There are a few online providers that specialize in working with insurance providers, such as Medicare or Medicaid. Many of the internet providers that deal with insurance such as Medicare will provide upgraded equipment to a patient even if he or she only qualifies for a basic PAP. In some locations a government program, separate from Medicare, can be used to claim a reimbursement for all or part of the cost of the PAP device.

* In the [[United Kingdom]], PAP machines are available on [[National Health Service]] prescription after a diagnosis of sleep apnea or privately from the internet provided a prescription is supplied.

* In [[Australia]], PAP machines can be bought from internet or physical stores on the provision of a prescription from a doctor. Low-income earners who hold a Commonwealth Health Care Card should enquire with their state's health department about programs that provide free or low-cost PAP machines. Those who have private health insurance are usually eligible for a partial rebate on the cost of a CPAP machine. [[Superannuation]] may be released for the purchase of essential medical equipment such as PAP machines, on the provision of letters from two doctors, one of whom must be your specialist, and an application to the [http://www.apra.gov.au/ Australian Prudential Regulation Authority] (APRA).

==In Hospital==

PAP ventilation is often used for patients who have acute type 1 or 2 [[respiratory failure]]. Usually PAP ventilation will be reserved for the subset of patients for whom oxygen delivered via a face mask is deemed to be insufficient or deleterious to health (see [[CO₂ retention]]). Usually patients on PAP ventilation will be closely monitored in an [[intensive care]], high dependency, [[coronary care unit]] or specialist respiratory unit.

The most common conditions for which PAP ventilation is used in hospital are [[congestive cardiac failure]] and acute exacerbation of [[airway obstruction|obstructive airways disease]], most notably exacerbations of [[COPD]] and [[asthma]]. It is not used in cases where the [[airway]] may be compromised, or consciousness is impaired.

The mask required to deliver CPAP must have a tight seal, and be held on very firmly. Most people find wearing the mask uncomfortable. Breathing out against the positive pressure resistance (the expiratory positive airway pressure component, or EPAP) is also unpleasant. These factors lead to inability to continue treatment due to patient intolerance in about 20% of cases where it is initiated. Obviously those who suffer an [[anxiety disorder]] or [[claustrophobia]] are more likely to be unable to tolerate PAP treatment. Sometimes medication will be given to assist with the anxiety caused by PAP ventilation.

Unlike PAP used at home to splint the [[tongue]] and [[pharynx]], PAP is used in hospital to improve the ability of the lung to exchange [[oxygen]] and [[carbon dioxide]], and to decrease the work of breathing (the energy expended moving air into and out of the alveoli). This is because:

* During inspiration, the inspiratory positive airway pressure, or IPAP, forces air into the lungs - thus less work is required from the respiratory muscles.

* The [[bronchioles]] and [[alveoli]] are prevented from collapsing at the end of expiration. If these small airways and alveoli are allowed to collapse, significant pressures are be required to re-expand them. This is because of [[the law of LaPlace]] (which explains why the hardest part of blowing up a balloon is the first breath).

* Entire regions of the lung that would otherwise be collapsed are forced and held open. This process is called recruitment. Usually these collapsed regions of lung will have some blood flow (although reduced). Because these areas of lung are not being ventilated the blood passing through these areas is not able to efficiently exchange oxygen and carbon dioxide. This is called ventilation/perfusion (or V/Q) mismatch. The recruitment reduces ventilation perfusion mismatch.

* The amount of air remaining in the lungs at the end of a breath is greater (this is called the [[Functional residual capacity]]). The chest and lungs are therefore more expanded. From this more expanded resting position, less work is required to [[inspire]]. This is due to the non-linear compliance-volume curve of the lung.

==The Neonate==

CPAP is commonly used in the term and preterm neonate with respiratory disease or with recurrent [[apnea]]. Often this form of PAP is referred to as bubble cpap, because bubbles are used to generate a high frequency [[oscillation]] in the expiratory phase (EPAP). These bubbles dramatically aid ventilation by establishing bidirectional flow of air in the smaller airways. Other differences to CPAP in the adult include lower pressures (usually around 5cm of water), and the use of snug fitting nasal prongs (a mouth component is not required as neonates are obligate nasal breathers).

Respiratory diseases for which CPAP is commonly used include [[infant respiratory distress syndrome]], [[meconium aspiration syndrome]] and [[Transient tachypnea of the newborn]]. Sometimes it is used for the treatment of [[bronchiolitis]] in the older neonate or younger infant. It is not known how CPAP prevents recurrent neonatal apneas.

PAP is used to prevent premature infants from going into respiratory failure thereby preventing the need for intubation. <ref>Chung CM. (1978) ''CPAP in infants with idiopathic respiratory distress syndrome.'' Mod Med Asia. 1978 May;14(5):26-30. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=351370&dopt=Abstract/]</ref>

When compared to ventilation via an endotracheal tube, CPAP seems to result in less [[barotrauma]] (although it by no means eliminates the risk of barotrauma) and in the extreme preterm, CPAP reduces the risk of developing [[Bronchopulmonary dysplasia]] when compared to mechanical ventilation via an endotrachea tube.

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== Voci correlate ==

* [[Sindrome delle apnee ostruttive nel sonno]]