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Ventilação Mecânica III: Ventilação Não Invasiva
A ventilação não invasiva com pressão positiva (VNIPP), a pressão positiva contínua nas vias aéreas (CPAP) e a pressão positiva bilevel nas vias aérea…
A ventilação não invasiva, ou VNI, fornece suporte ventilatório sem inserir uma via aérea artificial.
Esse tipo de ventilação é usado em pacientes com insuficiência respiratória que estão conscientes e podem respirar de forma independente, mas precisam de assistência para melhorar as trocas gasosas.
Os dois tipos de VNI são ventiladores de pressão negativa e ventilação não invasiva com pressão positiva, ou VNIPP.
Um ventilador de pressão negativa, que se assemelha a uma couraça, cria um vácuo ao redor do peito ou do corpo para puxar o ar para os pulmões, simulando a respiração.
Reduz intermitentemente a pressão intratorácica, lançando ar para as vias aéreas superiores, seguida de expiração passiva quando a máquina desliga.
Em seguida está a VNIPP, que usa máscaras faciais ou dispositivos nasais para manter a pressão prescrita.
Dois tipos de VNIPP são a pressão positiva contínua nas vias aéreas, ou CPAP, e a pressão positiva de dois níveis nas vias aéreas, ou BiPAP.
O CPAP fornece pressão positiva contínua nas vias aéreas, mantendo os alvéolos abertos e prevenindo a insuficiência respiratória.
Por outro lado, o BiPAP controla as pressões inspiratória e expiratória, fornecendo ventilação de suporte de pressão.
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Q1: What is noninvasive ventilation and how does it differ from invasive ventilation?
Noninvasive ventilation (NIV) provides ventilatory support without inserting an artificial airway, making it suitable for conscious patients with respiratory failure who can breathe independently. Unlike mechanical ventilation invasive ventilation, NIV uses facemasks or nasal devices to deliver pressure support, reducing infection risk and allowing patients to maintain natural airway protection while receiving respiratory assistance.
Q2: What are the two main types of noninvasive ventilation?
The two main types of noninvasive ventilation are negative-pressure ventilators and noninvasive positive-pressure ventilation (NIPPV). Negative-pressure ventilators create a vacuum around the chest to draw air into the lungs, simulating natural breathing. NIPPV uses facemasks or nasal devices to maintain prescribed pressure and is further divided into continuous positive airway pressure (CPAP) and bilevel positive airway pressure (BiPAP).
Q3: How does continuous positive airway pressure (CPAP) work?
CPAP delivers continuous positive airway pressure throughout the breathing cycle, keeping alveoli open and preventing respiratory failure. This constant pressure maintains airways in an open state, making CPAP especially beneficial for treating obstructive sleep apnea and other conditions where airway collapse occurs during breathing.
Q4: What is the key difference between CPAP and BiPAP?
CPAP maintains constant positive pressure throughout the entire breathing cycle, while bilevel positive airway pressure (BiPAP) independently controls inspiratory and expiratory pressures. BiPAP provides two distinct pressure levels via a nasal or oral mask, offering greater comfort and flexibility for patients requiring ventilatory assistance, particularly at night.
Q5: What patient conditions benefit from noninvasive positive-pressure ventilation?
Noninvasive positive-pressure ventilation (NIPPV) is suitable for patients with acute or chronic respiratory failure, acute pulmonary edema, chronic obstructive pulmonary disease (COPD), chronic heart failure, and sleep-related breathing disorders. NIPPV reduces nosocomial infection risk compared to invasive methods while providing adequate respiratory support without requiring intubation.
Q6: How does a negative-pressure ventilator function?
A negative-pressure ventilator, resembling a cuirass, creates a vacuum around the chest or body to draw air into the lungs. It intermittently reduces intrathoracic pressure, rushing air into the upper airway, followed by passive expiration when the machine cycles off, thereby simulating natural breathing mechanics.
Q7: What factors determine the choice between different noninvasive ventilation methods?
The choice between noninvasive ventilation methods depends on the patient's clinical condition, comfort level, and healthcare provider expertise. Each type has distinct advantages and disadvantages; CPAP suits constant pressure needs, BiPAP offers dual-pressure flexibility, and negative-pressure ventilators provide an alternative for specific patient populations requiring different support mechanisms.