Inverse ratio ventilation

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Inverse ratio ventilation (IRV) is not necessarily a mode of mechanical ventilation though it may be referred to as such. IRV is a strategy (method or style) of ventilating the lungs in such a way that the amount of time the lungs are in inhalation is greater than the amount of time they are in exhalation, allowing for a constant inflation of the lungs, ensuring they remain "recruited" (meaning they participate in gas exchange and are not allowed to deflate to get stuck together or tighten up). The primary goal for IRV is improved oxygenation by forcing inspiratory time to be greater than expiratory time (example: inhale is 3 seconds and exhalation is 1 second, a 3:1 I:E ratio) increasing the mean airway pressure and potentially improving oxygenation. Normal I:E ratio is 5:6, so forcing the I:E to be 2:1, 3:1, 4:1, (or even as high as 20:1) is the source of the term for the strategy.

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IRV has not often been shown to improve important clinical outcomes, such as mortality, duration of mechanical ventilation, or duration of ICU stay. This may be due to the fact that IRV is not considered as a mode early enough once ARDS is diagnosed. The preponderance of evidence suggests that IRV improves oxygenation, although the evidence is weak and characterized by low quality, conflicting studies. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

Types

IRV can be performed during pressure-controlled ventilation (PC-IRV) or volume-controlled ventilation(VC-IRV). Neither is clearly superior to the other. In a multicenter, randomized trial that compared PC-IRV to VC-IRV in patients with acute respiratory distress syndrome, the type of IRV did not affect mortality. [13]

Associated risk

The shorter expiratory time during IRV increases the risk of auto-PEEP and its associated development of problems (e.g. pulmonary barotrauma, hypotension). [10] IRV also appears to increase the risk of pulmonary barotrauma independent of auto-PEEP. In a study of 14 patients undergoing mechanical ventilation with PC-IRV, the incidence of pneumothorax was 29 percent despite the lack of measurable auto-PEEP. [14]

Modes that utilize IRV

The most popular mode that utilizes IRV is the airway pressure release ventilation mode, also known by the brand name "BiVent". This employs an extremely high inverse ratio in a continuous pressure system similar to biphasic positive airway pressure but with several additional variables.

Related Research Articles

<span class="mw-page-title-main">Respiratory failure</span> Inadequate gas exchange by the respiratory system

Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise in arterial carbon dioxide levels is called hypercapnia. Respiratory failure is classified as either Type 1 or Type 2, based on whether there is a high carbon dioxide level, and can be acute or chronic. In clinical trials, the definition of respiratory failure usually includes increased respiratory rate, abnormal blood gases, and evidence of increased work of breathing. Respiratory failure causes an altered mental status due to ischemia in the brain.

<span class="mw-page-title-main">Mechanical ventilation</span> Method to mechanically assist or replace spontaneous breathing

Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV) is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move air into and out of the lungs, with the main goal of helping the delivery of oxygen and removal of carbon dioxide. Mechanical ventilation is used for many reasons, including to protect the airway due to mechanical or neurologic cause, to ensure adequate oxygenation, or to remove excess carbon dioxide from the lungs. Various healthcare providers are involved with the use of mechanical ventilation and people who require ventilators are typically monitored in an intensive care unit.

<span class="mw-page-title-main">Pulmonary edema</span> Fluid accumulation in the tissue and air spaces of the lungs

Pulmonary edema, also known as pulmonary congestion, is excessive liquid accumulation in the tissue and air spaces of the lungs. It leads to impaired gas exchange and may cause hypoxemia and respiratory failure. It is due to either failure of the left ventricle of the heart to remove oxygenated blood adequately from the pulmonary circulation, or an injury to the lung tissue directly or blood vessels of the lung.

<span class="mw-page-title-main">Acute respiratory distress syndrome</span> Human disease

Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin coloration (cyanosis). For those who survive, a decreased quality of life is common.

Optoelectronic plethysmography is a method to evaluate ventilation through an external measurement of the chest wall surface motion.

Positive end-expiratory pressure (PEEP) is the pressure in the lungs above atmospheric pressure that exists at the end of expiration. The two types of PEEP are extrinsic PEEP and intrinsic PEEP. Pressure that is applied or increased during an inspiration is termed pressure support.PEEP is a therapeutic parameter set in the ventilator, or a complication of mechanical ventilation with air trapping (auto-PEEP).

High-frequency ventilation is a type of mechanical ventilation which utilizes a respiratory rate greater than four times the normal value. and very small tidal volumes. High frequency ventilation is thought to reduce ventilator-associated lung injury (VALI), especially in the context of ARDS and acute lung injury. This is commonly referred to as lung protective ventilation. There are different types of high-frequency ventilation. Each type has its own unique advantages and disadvantages. The types of HFV are characterized by the delivery system and the type of exhalation phase.

<span class="mw-page-title-main">Idiopathic interstitial pneumonia</span> Medical condition

Idiopathic interstitial pneumonia (IIP), or noninfectious pneumonia are a class of diffuse lung diseases. These diseases typically affect the pulmonary interstitium, although some also have a component affecting the airways. There are seven recognized distinct subtypes of IIP.

Ventilator-associated lung injury (VALI) is an acute lung injury that develops during mechanical ventilation and is termed ventilator-induced lung injury (VILI) if it can be proven that the mechanical ventilation caused the acute lung injury. In contrast, ventilator-associated lung injury (VALI) exists if the cause cannot be proven. VALI is the appropriate term in most situations because it is virtually impossible to prove what actually caused the lung injury in the hospital.

Pulmonary hygiene, formerly referred to as pulmonary toilet, is a set of methods used to clear mucus and secretions from the airways. The word pulmonary refers to the lungs. The word toilet, related to the French toilette, refers to body care and hygiene; this root is used in words such as toiletry that also relate to cleansing.

Pulmonary rehabilitation, also known as respiratory rehabilitation, is an important part of the management and health maintenance of people with chronic respiratory disease who remain symptomatic or continue to have decreased function despite standard medical treatment. It is a broad therapeutic concept. It is defined by the American Thoracic Society and the European Respiratory Society as an evidence-based, multidisciplinary, and comprehensive intervention for patients with chronic respiratory diseases who are symptomatic and often have decreased daily life activities. In general, pulmonary rehabilitation refers to a series of services that are administered to patients of respiratory disease and their families, typically to attempt to improve the quality of life for the patient. Pulmonary rehabilitation may be carried out in a variety of settings, depending on the patient's needs, and may or may not include pharmacologic intervention.

<span class="mw-page-title-main">Airway pressure release ventilation</span> Pressure control mode of mechanical ventilation

Airway pressure release ventilation (APRV) is a pressure control mode of mechanical ventilation that utilizes an inverse ratio ventilation strategy. APRV is an applied continuous positive airway pressure (CPAP) that at a set timed interval releases the applied pressure. Depending on the ventilator manufacturer, it may be referred to as BiVent. This is just as appropriate to use, since the only difference is that the term APRV is copyrighted.

<span class="mw-page-title-main">Liquid ventilator</span> Medical device

A liquid ventilator is similar to a medical ventilator except that it should be able to ensure reliable total liquid ventilation with a breatheable liquid ·. Liquid ventilators are prototypes that may have been used for animal experimentations but experts recommend continued development of a liquid ventilator toward clinical applications.

Modes of mechanical ventilation are one of the most important aspects of the usage of mechanical ventilation. The mode refers to the method of inspiratory support. In general, mode selection is based on clinician familiarity and institutional preferences, since there is a paucity of evidence indicating that the mode affects clinical outcome. The most frequently used forms of volume-limited mechanical ventilation are intermittent mandatory ventilation (IMV) and continuous mandatory ventilation (CMV). There have been substantial changes in the nomenclature of mechanical ventilation over the years, but more recently it has become standardized by many respirology and pulmonology groups. Writing a mode is most proper in all capital letters with a dash between the control variable and the strategy.

Continuous mandatory ventilation (CMV) is a mode of mechanical ventilation in which breaths are delivered based on set variables. Still used in the operating room, in previous nomenclature, CMV referred to "controlled mechanical ventilation", a mode of ventilation characterized by a ventilator that makes no effort to sense patient breathing effort. In continuous mandatory ventilation, the ventilator can be triggered either by the patient or mechanically by the ventilator. The ventilator is set to deliver a breath according to parameters selected by the operator. "Controlled mechanical ventilation" is an outdated expansion for "CMV"; "continuous mandatory ventilation" is now accepted standard nomenclature for mechanical ventilation. CMV today can assist or control itself dynamically, depending on the transient presence or absence of spontaneous breathing effort. Thus, today's CMV would have been called ACV in older nomenclature, and the original form of CMV is a thing of the past. But despite continual technological improvement over the past half century, CMV may still be uncomfortable for the patient.

Intermittent Mandatory Ventilation (IMV) refers to any mode of mechanical ventilation where a regular series of breaths are scheduled but the ventilator senses patient effort and reschedules mandatory breaths based on the calculated need of the patient. Similar to continuous mandatory ventilation in parameters set for the patients pressures and volumes but distinct in its ability to support a patient by either supporting their own effort or providing support when patient effort is not sensed. IMV is frequently paired with additional strategies to improve weaning from ventilator support or to improve cardiovascular stability in patients who may need full life support.

Within the medical field of respiratory therapy, Open lung ventilation is a strategy that is utilized by several modes of mechanical ventilation to combine low tidal volume and applied PEEP to maximize recruitment of alveoli. The low tidal volume aims to minimize alveolar overdistention and the PEEP minimizes cyclic atelectasis. Working in tandem the effects from both decrease the risk of ventilator-associated lung injury.

Dynamic hyperinflation is a phenomenon that occurs when a new breath begins before the lung has reached the static equilibrium volume. In simpler terms, this means that a new breath starts before the usual amount of air has been breathed out, leading to a build-up of air in the lungs, and causing breathing in and out to take place when the lung is nearly full.

Prone ventilation, sometimes called prone positioning or proning, refers to mechanical ventilation with the patient lying face-down (prone). It improves oxygenation in most patients with acute respiratory distress syndrome (ARDS) and reduces mortality. The earliest trial investigating the benefits of prone ventilation occurred in 1976. Since that time, many meta-analyses and one randomized control trial, the PROSEVA trial, have shown an increase in patients' survival with the more severe versions of ARDS. There are many proposed mechanisms, but they are not fully delineated. The proposed utility of prone ventilation is that this position will improve lung mechanics, improve oxygenation, and increase survival. Although improved oxygenation has been shown in multiple studies, this position change's survival benefit is not as clear. Similar to the slow adoption of low tidal volume ventilation utilized in ARDS, many believe that the investigation into the benefits of prone ventilation will likely be ongoing in the future.

<span class="mw-page-title-main">Pathophysiology of acute respiratory distress syndrome</span>

The pathophysiology of acute respiratory distress syndrome involves fluid accumulation in the lungs not explained by heart failure. It is typically provoked by an acute injury to the lungs that results in flooding of the lungs' microscopic air sacs responsible for the exchange of gases such as oxygen and carbon dioxide with capillaries in the lungs. Additional common findings in ARDS include partial collapse of the lungs (atelectasis) and low levels of oxygen in the blood (hypoxemia). The clinical syndrome is associated with pathological findings including pneumonia, eosinophilic pneumonia, cryptogenic organizing pneumonia, acute fibrinous organizing pneumonia, and diffuse alveolar damage (DAD). Of these, the pathology most commonly associated with ARDS is DAD, which is characterized by a diffuse inflammation of lung tissue. The triggering insult to the tissue usually results in an initial release of chemical signals and other inflammatory mediators secreted by local epithelial and endothelial cells.

References

  1. ↑ Mercat A, Graïni L, Teboul JL, Lenique F, Richard C (1993). "Cardiorespiratory effects of pressure-controlled ventilation with and without inverse ratio in the adult respiratory distress syndrome". Chest. 104 (3): 871–5. doi:10.1378/chest.104.3.871. PMID   8365303.
  2. ↑ Mercat A, Diehl JL, Michard F, Anguel N, Teboul JL, Labrousse J, et al. (2001). "Extending inspiratory time in acute respiratory distress syndrome". Crit Care Med. 29 (1): 40–4. doi:10.1097/00003246-200101000-00011. PMID   11176158.
  3. ↑ Shanholtz C, Brower R (1994). "Should inverse ratio ventilation be used in adult respiratory distress syndrome?". Am J Respir Crit Care Med. 149 (5): 1354–8. doi:10.1164/ajrccm.149.5.8173778. PMID   8173778.
  4. ↑ Mercat A, Titiriga M, Anguel N, Richard C, Teboul JL (1997). "Inverse ratio ventilation (I/E = 2/1) in acute respiratory distress syndrome: a six-hour controlled study". Am J Respir Crit Care Med. 155 (5): 1637–42. doi:10.1164/ajrccm.155.5.9154869. PMID   9154869.
  5. ↑ Wang SH, Wei TS (2002). "The outcome of early pressure-controlled inverse ratio ventilation on patients with severe acute respiratory distress syndrome in surgical intensive care unit". Am J Surg. 183 (2): 151–5. doi:10.1016/s0002-9610(01)00870-4. PMID   11918879.
  6. ↑ Sydow M, Burchardi H, Ephraim E, Zielmann S, Crozier TA (1994). "Long-term effects of two different ventilatory modes on oxygenation in acute lung injury. Comparison of airway pressure release ventilation and volume-controlled inverse ratio ventilation". Am J Respir Crit Care Med. 149 (6): 1550–6. doi:10.1164/ajrccm.149.6.8004312. PMID   8004312.
  7. ↑ Abraham E, Yoshihara G (1989). "Cardiorespiratory effects of pressure controlled inverse ratio ventilation in severe respiratory failure". Chest. 96 (6): 1356–9. doi:10.1378/chest.96.6.1356. PMID   2582844.
  8. ↑ Amato MB, Barbas CS, Medeiros DM, Schettino Gde P, Lorenzi Filho G, Kairalla RA, et al. (1995). "Beneficial effects of the "open lung approach" with low distending pressures in acute respiratory distress syndrome. A prospective randomized study on mechanical ventilation". Am J Respir Crit Care Med. 152 (6 Pt 1): 1835–46. doi:10.1164/ajrccm.152.6.8520744. PMID   8520744.
  9. ↑ Gurevitch MJ, Van Dyke J, Young ES, Jackson K (1986). "Improved oxygenation and lower peak airway pressure in severe adult respiratory distress syndrome. Treatment with inverse ratio ventilation". Chest. 89 (2): 211–3. doi:10.1378/chest.89.2.211. PMID   3943380. S2CID   41234021.
  10. 1 2 Tharratt RS, Allen RP, Albertson TE (1988). "Pressure controlled inverse ratio ventilation in severe adult respiratory failure". Chest. 94 (4): 755–62. doi:10.1378/chest.94.4.755. PMID   3168572. S2CID   20053045.
  11. ↑ Papadakos PJ, Halloran W, Hessney JI, Lund N, Feliciano DV (1991). "The use of pressure-controlled inverse ratio ventilation in the surgical intensive care unit". J Trauma. 31 (9): 1211–4, discussion 1214–5. doi:10.1097/00005373-199109000-00003. PMID   1920550.
  12. ↑ Lain DC, DiBenedetto R, Morris SL, Van Nguyen A, Saulters R, Causey D (1989). "Pressure control inverse ratio ventilation as a method to reduce peak inspiratory pressure and provide adequate ventilation and oxygenation". Chest. 95 (5): 1081–8. doi:10.1378/chest.95.5.1081. PMID   2495904.
  13. ↑ Esteban A, Alía I, Gordo F, de Pablo R, Suarez J, González G, et al. (2000). "Prospective randomized trial comparing pressure-controlled ventilation and volume-controlled ventilation in ARDS. For the Spanish Lung Failure Collaborative Group". Chest. 117 (6): 1690–6. doi:10.1378/chest.117.6.1690. PMID   10858404. S2CID   42343728.
  14. ↑ Armstrong BW, MacIntyre NR (1995). "Pressure-controlled, inverse ratio ventilation that avoids air trapping in the adult respiratory distress syndrome". Crit Care Med. 23 (2): 279–85. doi:10.1097/00003246-199502000-00013. PMID   7867353.
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