The function of the lungs is to provide gas exchange via oxygenation and ventilation. This phenomenon of respiration involves the physiologic concepts of air flow, tidal volume, compliance, resistance, and dead space. Other relevant concepts include alveolar ventilation, arterial PaCO2, alveolar volume, and FiO2. Alveolar ventilation is the amount of gas per unit of time that reaches the alveoli and becomes involved in gas exchange. PaCO2 is the partial pressure of carbon dioxide of arterial blood, which determines how well carbon dioxide is able to move out of the body. Alveolar volume is the volume of air entering and leaving the alveoli per minute.<unk>  dead space is another important parameter in ventilator design and function, and is defined as the volume of gas breathed again as the result of use in a<unk>  device. Image of endotracheal tube placement required to connect a patient's physiologic airway to the ventilator. Due to the anatomy of the human pharynx, larynx, and esophagus and the circumstances for which ventilation is needed, additional measures are often required to secure the airway during positive-pressure ventilation in order to allow unimpeded passage of air into the trachea and avoid air passing into the esophagus and stomach. The common method is by insertion of a tube into the trachea: intubation, which provides a clear route for the air. This can be either an endotracheal tube, inserted through the natural openings of mouth or nose, or a tracheostomy inserted through an artificial opening in the neck. In other circumstances simple airway maneuvers, an oropharyngeal airway or laryngeal mask airway may be employed. If the patient is able to protect his/her own airway and non-invasive ventilation or negative-pressure ventilation is used, then an airway adjunct may not be needed. Pain medicine such as opioids are sometimes used in adults and infants who require<unk> . For preterm or full term infants who require<unk> , there is no strong evidence to prescribe opioids or sedation routinely for these procedures, however, some select infants requiring<unk>  may require pain medicine such as opioids. It is not clear if clonidine is safe or effective to be used as a sedative for preterm and full term infants who require<unk> . When 100% oxygen (1.00 Fi) is used initially for an adult, it is easy to calculate the next Fi to be used, and easy to estimate the shunt fraction. The estimated shunt fraction refers to the amount of oxygen not being absorbed into the circulation. In normal physiology, gas exchange of oxygen and carbon dioxide occurs at the level of the alveoli in the lungs. The existence of a shunt refers to any process that hinders this gas exchange, leading to wasted oxygen inspired and the flow of un-oxygenated blood back to the left heart, which ultimately supplies the rest of the body with de-oxygenated blood. When using 100% oxygen, the degree of shunting is estimated as 700 mmHg - measured Pa. For each difference of 100 mmHg, the shunt is 5%. A shunt of more than 25% should prompt a search for the cause of this hypoxemia, such as mainstem intubation or pneumothorax, and should be treated accordingly. If such complications are not present, other causes must be sought after, and positive end-expiratory pressure (PEEP) should be used to treat this intrapulmonary shunt. Other such causes of a shunt include: * alveolar collapse from major atelectasis * alveolar collection of material other than gas, such as pus from pneumonia, water and protein from acute respiratory distress syndrome, water from congestive heart failure, or blood from hemorrhage
Mechanical ventilation
Negative pressure ventilator
Artificial ventilation
Positive airway pressure
Non-invasive ventilation
High-frequency ventilation
Pressure support ventilation
Surfactant therapy