Airway pressure release ventilation (APRV) is inverse ratio, pressure controlled, intermittent mandatory ventilation with unrestricted spontaneous breathing. It is based on the principle of open lung approach. It has many purported advantages over conventional ventilation, including alveolar recruitment, improved oxygenation, preservation of spontaneous breathing, improved hemodynamics, and potential lung-protective effects. It has many claimed disadvantages related to risks of volutrauma, increased work of breathing, and increased energy expenditure related to spontaneous breathing. APRV is used mainly as a rescue therapy for the difficult to oxygenate patients with acute respiratory distress syndrome (ARDS). There is confusion regarding this mode of ventilation, due to the different terminology used in the literature. APRV settings include the "P high," "T high," "P low," and "T low". Physicians and respiratory therapists should be aware of the different ways and the rationales for setting these variables on the ventilators. Also, they should be familiar with the differences between APRV, biphasic positive airway pressure (BIPAP), and other conventional and nonconventional modes of ventilation. There is no solid proof that APRV improves mortality; however, there are ongoing studies that may reveal further information about this mode of ventilation. This paper reviews the different methods proposed for APRV settings, and summarizes the different studies comparing APRV and BIPAP, and the potential benefits and pitfalls for APRV.

The American Association for Respiratory Care has declared a benchmark for competency in mechanical ventilation that includes the ability to "apply to practice all ventilation modes currently available on all invasive and noninvasive mechanical ventilators." This level of competency presupposes the ability to identify, classify, compare, and contrast all modes of ventilation. Unfortunately, current educational paradigms do not supply the tools to achieve such goals. To fill this gap, we expand and refine a previously described taxonomy for classifying modes of ventilation and explain how it can be understood in terms of 10 fundamental constructs of ventilator technology: (1) defining a breath, (2) defining an assisted breath, (3) specifying the means of assisting breaths based on control variables specified by the equation of motion, (4) classifying breaths in terms of how inspiration is started and stopped, (5) identifying ventilator-initiated versus patient-initiated start and stop events, (6) defining spontaneous and mandatory breaths, (7) defining breath sequences (8), combining control variables and breath sequences into ventilatory patterns, (9) describing targeting schemes, and (10) constructing a formal taxonomy for modes of ventilation composed of control variable, breath sequence, and targeting schemes. Having established the theoretical basis of the taxonomy, we demonstrate a step-by-step procedure to classify any mode on any mechanical ventilator.

Objective: To determine accuracy of the 7-8-9 Rule in a cohort of neonates.Study Design: This study was cross-sectional in design. Seventy-five consecutive neonates who required oral intubation from June 2004 to November 2004 for cardiopulmonary failure, respiratory distress, or surfactant administration were the subjects of this study. The initial endotracheal tube (ETT) depth of insertion was determined using either an estimated birth weight or actual weight in the 7-8-9 Rule calculation followed by auscultation and subsequent adjustment if necessary. Midtracheal position was identified as the point halfway between the inferior clavicle and carina on a chest radiograph. The initial depth was compared to the midtracheal depth to determine clinical accuracy of the 7-8-9 Rule. The depth predicted by the 7-8-9 Rule was also calculated using only actual weights. This predicted depth was compared to the midtracheal depth to determine true accuracy of the 7-8-9 Rule. Accuracy was determined using mean paired differences with 95% confidence intervals (CI) between initial or predicted depth and ideal, midtracheal ETT depth. Linear regression was used to adjust for confounding variables.Results: Mean (range) gestational age was 32 weeks (23 to 44 weeks) and weight was 2001 g (490 to 4400 g). Eighteen (24%) infants weighed 1000 g or less, 20 (27%) weighed between 1001 and 2000 g, 21 (28%) weighed between 2001 and 3000 g, 15 (20%) weighed between 3001 and 4000 g, and one (1%) weighed more than 4000 g. Thirteen of the 18 extremely low birth weight infants weighed <750 g. The initial depth of insertion was 0.004 cm above midtracheal position (95% CI À0.13 to 0.14, P ¼ 0.96). After controlling for head position, the initial depth did not significantly differ from the midtracheal position among weight groups. Predicted depth using the 7-8-9 Rule placed the ETT 0.12 cm above midtracheal position (95% CI À0.30 to 0.06, P ¼ 0.20). However, after controlling for head position, the 7-8-9 Rule positioned the ETT significantly below midtracheal position in infants weighing <750 g (mean 0.62 cm; 95% CI 0.30 to 0.93, P ¼ 0.002). Conclusions:The 7-8-9 Rule appears to be an accurate clinical method for endotracheal tube placement in neonates weighing more than 750 g. When the 7-8-9 Rule is applied to infants weighing <750 g, caution is warranted. The current rule may lead to an overestimated depth of insertion and potentially result in clinically significant consequences.

Acute respiratory distress syndrome (ARDS) results in collapse of alveoli and therefore poor oxygenation. In this article, we review airway pressure release ventilation (APRV), a mode of mechanical ventilation that may be useful when, owing to ARDS, areas of the lungs are collapsed and need to be reinflated ("recruited"), avoiding cyclic alveolar collapse and reopening.

There has been a dramatic increase in the number and complexity of new ventilation modes over the last 30 years. The impetus for this has been the desire to improve the safety, efficiency, and synchrony of ventilator-patient interaction. Unfortunately, the proliferation of names for ventilation modes has made understanding mode capabilities problematic. New modes are generally based on increasingly sophisticated closed-loop control systems or targeting schemes. We describe the 6 basic targeting schemes used in commercially available ventilators today: set-point, dual, servo, adaptive, optimal, and intelligent. These control systems are designed to serve the 3 primary goals of mechanical ventilation: safety, comfort, and liberation. The basic operations of these schemes may be understood by clinicians without any engineering background, and they provide the basis for understanding the wide variety of ventilation modes and their relative advantages for improving patient-ventilator synchrony. Conversely, their descriptions may provide engineers with a means to better communicate to end users.

BACKGROUND: The overwhelming demand for mechanical ventilators due to COVID-19 has stimulated interest in using one ventilator for multiple patients (ie, multiplex ventilation). Despite a plethora of information on the internet, there is little supporting evidence and no human studies. The risk of multiplex ventilation is that ventilation and PEEP effects are largely uncontrollable and depend on the difference between patients' resistance and compliance. It is not clear whether volume control ventilation or pressure control ventilation is safer or more effective. We designed a simulation-based study to allow complete control over the relevant variables to determine the effects of various degrees of resistance-compliance imbalance on tidal volume (V T), end-expiratory lung volume (EELV), and imputed pH. METHODS: Two separate breathing simulators were ventilated with a ventilator using pressure control and volume control ventilation modes. Evidence-based lung models simulated a range of differences in resistance and compliance (6 pairs of simulated patients). Differences in V T , EELV, and imputed pH were recorded. RESULTS: Depending on differences in resistance and compliance, differences in V T ranged from 1% (with equal resistance and compliance) to 79%. Differences in EELV ranged from 2% to 109%, whereas differences in pH ranged from 0% to 5%. Failure due to excessive V T (ie, > 8 mL/kg) did not occur, but failure due to excessive EELV difference (ie, > 10%) was evident in 50% of patient pairs. There was no difference in failure rate between volume control and pressure control ventilation modes. CONCLUSIONS: These experiments confirmed the potential for markedly different ventilation and oxygenation for patients with uneven respiratory system impedances during multiplex ventilation. Three critical problems must be solved to minimize risk: (1) partitioning of inspiratory flow from the ventilator individually between the 2 patients, (2) measurement of V T delivered to each patient, and (3) provision for individual PEEP. We provide suggestions for solving these problems.

This study provides educators, researchers, and manufacturers with a standard set of practical parameters for simulating the respiratory system's mechanical properties in passive conditions.

To test the ability of an assessment-driven algorithm for treatment of pediatric status asthmaticus to reduce length and cost of hospitalization.