Positive airway pressure ventilation

Treatments that have been proposed to prevent pulmonary edema in exposed-asymptomatic persons include steroids, ibuprofen, V-acetyl cysteine, and positive pressure airway ventilation. However, there is no known antidote for phosgene poisoning, and although animal studies suggest that these treatments may be effective, no clinical data are available to verify efficacy in humans (Borak and Diller,... 

Modern positive-pressure mechanical ventilators have been quite successful in treating patients with pulmonary disorders. Two major categories of breath dehvery modes for these ventilators are mandatory and spontaneous. The volume- and pressure-controlled mandatory breath delivery and the governing control equations for these modes are presented in this chapter. Similarly, CPAP and support pressure modes of spontaneous breath dehvery are described. Recent development of dual control modes that allow simultaneous monitoring and control of airway pressure and minute volume are also presented. 

Keller C, Sparr HJ, Brimacombe JR. Positive pressure ventilation with the laryngeal mask airway in non-paralysed patients comparison of sevoflurane and propofol maintenance techniques. Br J Anaesth 1998 80(3) 332-6. 

Positive pressure ventilation via a face mask, such as biphasic intermittent positive airway pressure violation or continuous positive airway pressure ventilation... 

Positive airway pressure ventilation some experts recommend using positive pressure ventilation during the early, asymptomatic phase following phosgene exposure to prevent pulmonary edema. While positive pressure ventilation may reduce fluid accumulation, stabilize the intra-alveolar surfactant film and suppress arteriovenous shunts, many asymptomatic patients will find the treatment unacceptable (34). In addition, resources for providing prophylactic positive pressure ventilation may not be available in a mass-casualty situation. 

When exposure to 1,1,1-trichloroethane ceases, regardless of route of exposure, the compound is rapidly cleared from the body, predominantly by exhalation of unchanged 1.1.1-trichloroethane in expired air (see Section 2.3.). Very little metabolism of the compound takes place, and despite a preferential distribution of absorbed 1,1,1 -trichloroethane to fatty tissues, significant retention does not occur without continued exposure. Thus, continued ventilation by the lungs will eliminate the compound from the body. Suggested methods to assist in lung ventilation include orotracheal and nasotracheal intubation for airway control and positive pressure ventilation techniques (Bronstein and Currance 1988 Ellenhorn and Barceloux 1988). 

Hypoxia improves as the bronchospasm improves, and long-term oxygen supplementation is rarely required. If long-term oxygen supplementation is needed, a search for other causes of hypoxia should be undertaken. Early institution of positive airway pressure (such as using a PEEP mask) may be useful. Positive pressure ventilation may be necessary if PEEP is insufficient to maintain Po2 greater than 60 mm Hg. Occasional reports of subcutaneous emphysema after chlorine exposure should not... 

If abnormal, these measurements mandate close observation and support at the intensive care level. If the measurements are normal, they all must be repeated 4 to 6 hours after the suspected exposure only then can an individual be released to a lower medical priority status. Abnormality of any one of those measures, in the absence of other explanation, should prompt institution of therapy for noncardiac pulmonary edema. At the early stages of treatment, therapy should include positive airway pressure with early application of the PEEP mask. Later application of positive pressure ventilation through intubation may be required if the PEEP mask fails to maintain adequate arterial Po2. 

Severe exposures (sufficient to give rise to the rapid onset of symptoms) may require therapeutic intervention similar to that for chlorine exposure. Individuals with highly reactive airways are particularly at risk. In the event of triggered broncho-spasm, these patients would benefit from aggressive bronchodilator use consideration should also be given to the early use of steroids as well as positive-pressure ventilation.4 29,34... 

In this mode, the ventilator maintains a positive pressure at the airway as the patient attempts to inspire. Figure 18.6 illustrates a typical airway pressure waveform during continuous positive airway pressure (CPAP) breath delivery. The therapist sets the sensitivity level lower than PEEP. The sensitivity is the pressure level that the patient has to attain by making an effort to breathe. This, in turn, triggers the ventilator to deliver a spontaneous breath by supplying air (or a mixture of air and oxygen) to raise the pressure back to the PEEP level. Typically, the PEEP and sensitivity levels are selected such that the patient will be impelled to exert effort to breathe independently. As in the case of the mandatory mode, when the patient exhales, the ventilator shuts off the flow of gas and opens the exhalation valve to allow the patient to exhale into the atmosphere. 

Continuous positive airway pressure (CPAP) A spontaneous ventilation mode in which the ventilator maintains a constant positive pressure, near or below PEEP level, in the patient s airway while the patient breathes at will. 

Pressure support A spontaneous breath dehvery mode during which the ventilator applies a positive pressure greater than PEEP to the patient s airway during inspiration. 

Sleep therapy and respiratory care represent an additional class of applications in healthcare. Respirators, ventilators, and positive-pressure devices to allow airways to function properly are specific examples and require biocompatibilty. Respiratory masks and valves require chemical resistance and impact performance. PC-based blends are commonly used in applications in this space. 

Susceptibility factors Preterm infants Of7629 preterm and term infants admitted to the Neonatal Unit of the Royal Women s Hospital between 2001 and 2008, the 411 infants who received their first immunizations in hospital were both very preterm and of extremely low birth weights (<1000g) [2 ]. There was post-immunization apnea in 22 infants of sufficient severity to warrant the introduction of either intermittent positive pressure ventilation (two cases) or continuous positive airway pressure (CPAP) (20 cases). Infants with respiratory deterioration after immunization had a higher incidence of previous septicemia. 

Ventilators are either negative-pressure or positive-pressure. Negative-pressure ventilation involves directing air directly into the lungs, and positive-pressure ventilation involves directing air into the trachea. Some ventilators require intubation, the placement of a tube into the trachea from the nose or mouth. Ventilation requiring intubation is typically used for patients who will require ventilation for a protracted period. Other ventilators work with a breathing mask that can be placed over the mouth and nose. With the increase in respiratory-related sleep disorders (such as obstructive sleep apnea), use of two positive airway pressure systems—continuous positive airway pressure (CPAP) and bilevel positive pressure ventilators (BiPAP)—has become very common. 

Regardless of whether a ventilator uses positive pressure or negative pressure, the trans-pulmonary pressure gradient determines the tidal volume. A ventilator that is a pressure controller delivers a preset pressure and this variable is unaffected by changes in limg compliance or resistance. A positive pressure ventilator applies pressure inside the chest to expand it using a noninvasive interface, or an artificial airway. 

The use of MI-E has been demonstrated to be very important in extubating NMD patients following general anesthesia, despite their lack of any breathing tolerance, and managing them with NIV (8,9,60). It is also permitted to avoid intubation or to quickly extubate NMD patients in acute ventilatory failure with no breathing tolerance and profuse airway secretions due to intercurrent chest infections (37,83,84). MI-E in a protocol with manually assisted coughing, oximetry feedback, and home use of noninvasive intermittent positive pressure ventilation was shown to effectively decrease hospitalizations and respiratory complications, and mortality for patients with NMD (7,85). 

Bi-level NIV may be used as a first-line treatment, with supplemental oxygen (27). Expiratory airway pressure is titrated to control h5q)opneas and apneas, and inspiratory airway pressure is added to control Paco2. If bi-level NIV fails, nasal volume ventilation may be used (29). In many patients with OHS and predominant OSA, once hypercapnia has improved (which may take several weeks) nCPAP may be used (29). Thirteen obese patients (n = 13) with a BMI > 35, aged 28-69 years with severe OSAS and hypercapnia (8.2 0.3 kPa) and failing to respond to initial CPAP therapy, were treated via a nasal nocturnal volume-cycled ventilator, which was tolerated by all patients. Significant improvements in daytime arterial blood gas levels were obtained after 7 to 18 days of nasal intermittent positive pressure ventilation (29) in 10 of the 13 patients three months later, 12 of the 13 patients could be converted to nCPAP therapy and one patient remained on NIV. In another study (37), the same results were observed after three months of home nocturnal bi-level NIV in seven patients, three of whom had severe obesity. 

Waldhom RE. Nocturnal nasal intermittent positive pressure ventilation with bi-level airway pressure (BIPAP) in respiratory failure. Chest 1992 101 516-521. 

Shivaram U, Cash ME, Beal A. Nasal continuous positive airway pressure in decompensated hypercapnic respiratory failure as a complication of sleep apnea. Chest 1993 104 770-774. Sturani C, Galavotti Y, Scarduelli C, et al. Acute respiratory failure due to severe obstructive sleep apnea syndrome, managed with nasal positive pressure ventilation. Monaldi Arch Chest Dis 1994 49 558-560. 

Abbreviations-. Sp02, saturation of oxygen in arterial blood NIPPV, noninvasive intermittent positive pressure ventilation MAC, mechanically assisted cough CO2, carbon dioxide IPAP, inspiratory positive airway pressure BiPAP, bi-level positive airway pressure. 

Abbreviations-. IPAP/EPAP, ratio of inspirat(xy positive airway pressure and expiratory positive airway pressure NP ABG, arterial blood gas 6-MWD, six-minute walking distance 6-MWT, six-minute walk test HRQL, health-related quaUty of Ufe RVEL, right ventricular ejection fraction LVEF, left ventricular ejection fraction NIPPV, noninvasive positive pressure ventilation O2, oxygen Til, tension time index. 

Obstruction of the upper or lower airways may cause an increase in respiratory load. Obstructive sleep apnea (OSA) is less common in children than in adults. In this age group, enlarged tonsils and adenoids play a predominant role (3). Noninvasive continuous positive airway pressure (CPAP) ventilation has proved its efficacy and is proposed as a first therapeutic option if tonsillectomy and adenoidectomy are not able to relieve upper airway obstruction (4,5). Congenital abnormalities of the upper airways, such as laryngomalacia, tracheomalacia, or Pierre Robin syndrome, may also cause severe upper airway obstruction (6). Even in young infants, noninvasive CPAP may correct the alveolar hypoventilation (7). 

Essouri S, Nicot F, Clement A, et al. Noninvasive positive pressure ventilation in infants with upper airway obstruction comparison of continuous and bilevel positive pressure. Intensive Care... 

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