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Acute Respiratory Failure: Causes and Mechanisms

by ICU Ventilator

Acute respiratory failure (ARF) is a critical condition characterized by the respiratory system’s inability to maintain adequate gas exchange, presenting an immediate threat to life. Its etiologies encompass a wide range of conditions, including acute respiratory distress syndrome (ARDS), pneumonia, exacerbations of chronic obstructive pulmonary disease (COPD), and neuromuscular disorders, all necessitating timely and effective intervention.

Acute respiratory failure (ARF) is a life-threatening condition defined by the respiratory system’s inability to maintain adequate gas exchange, resulting in critically low oxygen levels in the blood (hypoxemia), elevated carbon dioxide levels (hypercapnia), or a combination of both (1). ARF can result from diverse etiologies, including acute respiratory distress syndrome (ARDS), pneumonia, chronic obstructive pulmonary disease (COPD) exacerbations, pulmonary embolism, neuromuscular disorders, or trauma (2, 3). These conditions impair the lung’s capacity to oxygenate blood and eliminate carbon dioxide, leading to severe systemic consequences if not managed promptly and effectively.

What is Acute Respiratory Failure?

Acute respiratory failure (ARF) is a medical condition in which the respiratory system fails to perform its primary function of effective gas exchange. This failure leads to inadequate oxygenation of the blood (hypoxemia), impaired elimination of carbon dioxide from the body (hypercapnia), or both (1). ARF can develop rapidly as a result of various underlying pathologies affecting the lungs, airways, chest wall, or central nervous system (2, 3).

ARF is often a life-threatening emergency that necessitates immediate medical intervention to prevent severe complications or death.

Basic Physiology of the Respiratory System

The primary role of the respiratory system is to facilitate gas exchange, ensuring oxygen delivery to tissues and carbon dioxide removal. This process depends on the proper functioning of several components (5–7):

  1. Ventilation: The physical movement of air into and out of the lungs, determined by respiratory muscle effort and airway patency.
  2. Diffusion: The exchange of gases between the alveoli and pulmonary capillaries, driven by partial pressure gradients.
  3. Perfusion: The blood flow through pulmonary capillaries, enabling gas exchange.

In ARF, a disruption in one or more of these components impairs gas exchange:

  • Hypoxemic ARF: Defined as PaO₂ < 60 mmHg with normal or low PaCO₂, resulting from impaired oxygenation.
  • Hypercapnic ARF: Defined as PaCO₂ > 45 mmHg with acidemia, caused by inadequate ventilation.

Pathophysiological Mechanisms of ARF

MechanismDefinitionCausesEffect
Ventilation-Perfusion (V/Q) MismatchMismatch between ventilated and perfused lung areas.Pulmonary embolism, pneumonia, atelectasis.Hypoxemia.
Diffusion ImpairmentReduced oxygen transfer across the alveolar-capillary membrane.ARDS, pulmonary fibrosis, interstitial pneumonia.Hypoxemia despite adequate ventilation.
HypoventilationReduced air movement in and out of the lungs, leading to CO₂ retention.CNS depression, neuromuscular disorders, obesity.Hypercapnia and secondary hypoxemia.
ShuntingBlood bypasses ventilated alveoli, preventing oxygenation.ARDS, pneumonia, large atelectasis.Severe hypoxemia unresponsive to oxygen therapy.
Increased Work of BreathingRespiratory muscles overwork to overcome resistance or poor compliance.COPD exacerbations, asthma, ARDS.Respiratory fatigue and eventual failure.
Table 1: Pathophysiological Mechanisms of ARF

Ventilation-Perfusion (V/Q) Mismatch

  • Definition: A mismatch occurs when areas of the lungs are ventilated but not perfused, or perfused but not ventilated.
  • Causes: Pulmonary embolism (low perfusion), pneumonia, or atelectasis (low ventilation).
  • Effect: Impairs oxygen delivery and carbon dioxide removal, causing hypoxemia.

Diffusion Impairment

  • Definition: Thickening or damage to the alveolar-capillary membrane reduces oxygen transfer to the blood.
  • Causes: Pulmonary fibrosis, ARDS, or severe interstitial pneumonia.
  • Effect: Decreases arterial oxygenation despite adequate ventilation.

Hypoventilation

  • Definition: Reduced air movement in and out of the lungs leads to insufficient CO₂ elimination.
  • Causes: Central nervous system depression (e.g., drug overdose), neuromuscular disorders (e.g., Guillain-Barré syndrome), or severe obesity.
  • Effect: Causes hypercapnia and secondary hypoxemia.

Shunting

  • Definition: Blood flows through areas of the lungs without gas exchange, bypassing functional alveoli.
  • Causes: ARDS, pneumonia, or large atelectasis.
  • Effect: Results in severe hypoxemia unresponsive to oxygen therapy.

Increased Work of Breathing

  • Definition: Respiratory muscles work harder to overcome airway resistance or reduced lung compliance.
  • Causes: COPD exacerbations, asthma, or ARDS.
  • Effect: Leads to respiratory muscle fatigue and eventual failure.

What are the Main Causes of Acute Respiratory Failure?

CategoryCausesExamples
Pulmonary CausesConditions directly impairing lung function.ARDS, pneumonia, COPD exacerbations, asthma, pulmonary embolism.
Extrapulmonary CausesConditions indirectly affecting the respiratory system.Neuromuscular disorders, CNS depression, thoracic cage abnormalities.
Trauma and External FactorsPhysical trauma or external agents affecting ventilation.Chest trauma, sedative overdose, toxins, or neuromuscular blockers.
Table 2: Main Causes of ARF

Acute respiratory failure (ARF) arises from a wide range of conditions affecting the respiratory system or its control mechanisms. These causes are broadly categorized as pulmonary causes, such as ARDS and pneumonia, directly impair lung function, while extrapulmonary causes, including neuromuscular disorders and CNS depression, indirectly disrupt respiratory mechanics:

Pulmonary Causes

  • Acute Respiratory Distress Syndrome (ARDS): Severe lung inflammation and alveolar damage leading to profound hypoxemia.
  • Pneumonia: Infectious consolidation of lung tissue impairs ventilation and gas exchange.
  • Chronic Obstructive Pulmonary Disease (COPD) Exacerbations: Increased airway obstruction and gas trapping result in hypercapnia.
  • Asthma: Severe bronchoconstriction impairs airflow, causing hypoxemia and hypercapnia.
  • Pulmonary Embolism (PE): Blockage of pulmonary arteries disrupts perfusion.

Extrapulmonary Causes

  • Neuromuscular Disorders: Conditions like Guillain-Barré syndrome or myasthenia gravis weaken respiratory muscles, reducing ventilation.
  • Central Nervous System Depression: Stroke, trauma, or sedative overdose impairs respiratory drive.
  • Thoracic Cage Abnormalities: Structural conditions such as kyphoscoliosis limit lung expansion.
  • Obesity Hypoventilation Syndrome: Excess weight restricts chest wall movement, leading to hypoventilation.

Trauma and External Factors

  • Chest Trauma: Rib fractures or pneumothorax compromise ventilation mechanics.
  • Toxins and Medications: Sedatives, opioids, or neuromuscular blockers depress respiratory effort or muscle function.

ARF is a multifaceted condition with diverse etiologies that disrupt normal respiratory physiology (3). Hypoxemia and hypercapnia serve as key markers of dysfunction, emphasizing the importance of understanding the underlying pathology for timely and effective management. Accurate diagnosis and targeted interventions, including mechanical ventilation, are essential to restoring respiratory function and preventing severe complications.

References

  1. Rochwerg B, Brochard L, Elliott MW, et al. Official ERS/ATS clinical practice guidelines: noninvasive ventilation for acute respiratory failure. Eur Respir J. 2017;50(2):1602426. Published 2017 Aug 31. doi:10.1183/13993003.02426-2016
  2. Chen L, Rackley CR. Diagnosis and Epidemiology of Acute Respiratory Failure. Crit Care Clin. 2024;40(2):221-233. doi:10.1016/j.ccc.2023.12.001
  3. Bos LDJ, Ware LB. Acute respiratory distress syndrome: causes, pathophysiology, and phenotypes. Lancet. 2022;400(10358):1145-1156. doi:10.1016/S0140-6736(22)01485-4
  4. Villgran VD, Lyons C, Nasrullah A, Clarisse Abalos C, Bihler E, Alhajhusain A. Acute Respiratory Failure. Crit Care Nurs Q. 2022;45(3):233-247. doi:10.1097/CNQ.0000000000000408
  5. Haddad M, Sharma S. Physiology, Lung. In: StatPearls. Treasure Island (FL): StatPearls Publishing; July 20, 2023.
  6. Roussos C, Koutsoukou A. Respiratory failure. Eur Respir J Suppl. 2003;47:3s-14s. doi:10.1183/09031936.03.000385037.     Ware LB. Pathophysiology of acute lung injury and the acute respiratory distress syndrome. Semin Respir Crit Care Med. 2006;27(4):337-349. doi:10.1055/s-2006-948288
  7. Ware LB. Pathophysiology of acute lung injury and the acute respiratory distress syndrome. Semin Respir Crit Care Med. 2006;27(4):337-349. doi:10.1055/s-2006-948288
Modes of Mechanical Ventilation | mechanical ventilation modes

The Most Common Modes of Mechanical Ventilation

by with No Comment Uncategorized

Mechanical ventilation is the process of using an external device (machine) to aid gaseous movement in and out of the lung. It serves as a type of life-saving device that facilitates breathing. Also, it’s widely used as an artificial breathing support in surgical cases, extremely ill situations, or when an individual is incapable of breathing on their own.  Various modes of mechanical ventilation play a great role in respiratory support, patient stabilization, and provision of pressure to prevent the alveoli from collapsing. Continue reading, as this article provides you with diverse mechanical ventilation modes and some of the most common modes of air circulation.

Modes of Mechanical Ventilation

Pressure Controlled Ventilation (PCV)

Pressure-controlled ventilation is a special kind of assisted respiration whereby a patient’s inspiratory pressure is predetermined. This mechanical ventilation mode provides an amount of aeration that depends on the compliance of the lungs and the resistance of the alveoli. It is an airflow system where the maximum airway force is constant and the total ventilation fluctuates. 

PCV is one of the most convincing pressure-limited ventilation (PLV) that is used regularly in the initial stages of newborn care. It is a technique recommended by different centers for preventing lobar emphysema. Although PCV reduces the risk of barotrauma, it could be challenging to provide a sufficient tidal volume (VT) when used in patients with ARDS. Also, an improper setting of this ventilator can lead to hypoxia and respiratory depression. 

Modes of Mechanical Ventilation

Volume Controlled Ventilation (VCV)

The modes of mechanical ventilation that involves a preset tidal volume to be provided in a specific amount of time is volume-controlled ventilation. It is usually more simple and comprehensible for most medical practitioners new to assisted air circulation. In this case, total ventilation is always set, the volume of breath supplied is constant, but the inspiratory pressure is unstable. 

Most of the time, VCV is commonly used in anesthesia, either in the assisted control (AC) mode or continuous mandatory ventilation (CMV). Due to the increase in peak pressure (PIP) with steady and accurate breathing volume, it usually causes uneven gaseous distribution and volutrauma. 

Pressure Support Ventilation (PSV)

A special mode of positive-pressure mechanical ventilation that requires patient initiation of each breath is known as pressure support ventilation. This kind of aided respiration can be administered either through the use of intubation (invasive) or with a mask (non-invasive) ventilatory pattern. It’s known as the most pleasant aided airflow with a useful system that delivers the benefits of the two types of ventilator patterns. 

PSV involves setting maximum driving pressure which usually indicates the ventilator flow rate. Sometimes, the patient’s pulmonary compliance, airway resistance, PIP, and breathing efforts frequently affect this flow rate. There is no minimum minute ventilation and the tidal volume provided is influenced by the flow and rate of breathing. Due to a volatile VT, it may also make the lung distend excessively. 

Pressure-Limited Time-Cycled Ventilation

Another type of PLV (similar to a pressure-controlled ventilator) that was previously used in neonates is the time-cycled PLV. This mechanical ventilation mode makes use of a predetermined peak pressure and a specified volume of gas within an extended period. While breathing in, this triggered ventilator provides a steady flow of air to the patient. 

Previous reports about the use of pressure-limited time-cycled ventilation have shown that lungs are usually susceptible to atelectrauma and barotrauma conditions. In addition, it has been observed that one of the primary factors influencing ventilator-associated lung injury (VALI) is Total ventilation (VT).

mechanical ventilation modes

Synchronized Intermittent Mandatory Ventilation (SIMV)

This is a unique mode of mechanical ventilation that provides a fixed tidal volume at a predefined frequency. In most cases, synchronized intermittent mandatory air circulation always permits patients to voluntarily breathe on their own. SIMV produces a mandatory breath that is delivered at the same moment the patient starts initiating their breath (spontaneous breath). In addition, positive end-expository pressure (PEEP) can also be administered using this synchronized IMV method. 

SIMV is mostly required by people with COPD, neuromuscular disorder, or ARDS and is used alongside pressure support ventilation. In some instances where SIMV is improperly used, there may be an inability to initiate spontaneous breath, fluctuations in intrathoracic force, or severe respiratory failure. This technique of ventilation is risky for hyperventilation, consumes much time, and can cause infection, barotrauma, or cardiac arrhythmias.

Modes of Mechanical Ventilation

High Flow Nasal Cannula (HFNC)

A high-flow nasal cannula is an oxygen therapy commonly called a heated, humidified, high-flow nasal cannula (HHFNC). It entails the delivery of a flexible blend of warmed, humid, and oxygen-rich air at a variable pace that surpasses spontaneous pulmonary flow. Whenever this aeration is used to provide oxygen, the flow is significantly greater than that with conventional nasal cannulas. 

In addition, HFNC enhances the functional residual capacity, and accurate distribution of oxygen. This mechanical ventilation mode often has an outcome of improved breathing efficiency due to continuous high oxygen flow that often washes out the anatomical dead space. 

Self Adjustable Ventilation (SAV)

Self Adjustable Ventilation is a special ventilator that makes use of detectors to constantly alter the airflow in response to changes in air properties. With the help of this technique, indoor comfort, improved air exchange systems, and environmental sustainability are guaranteed. This often allows great flexibility in ventilator parameters and also blends soothingly with a wide range of conditions.

References

1.https://my.clevelandclinic.org/health/treatments/15368-mechanical-ventilation

2.https://www.sciencedirect.com/topics/medicine-and-dentistry/pressure-controlled-ventilation

3. https://ecampusontario.pressbooks.pub/mechanicalventilators/chapter/volume-control-ventilation/

4.https://ecampusontario.pressbooks.pub/mechanicalventilators/chapter/volume-control-ventilation/

5.https://pubmed.ncbi.nlm.nih.gov/31536312/#:~:text=

6.https://journals.lww.com/jcma/fulltext/2019/10000/volume_targeted_versus_pressure_limited.14.aspx#:~:text=

7. https://www.icliniq.com/articles/respiratory-health/synchronized-intermittent-mandatory-ventilation

8.https://www.uptodate.com/contents/high-flow-nasal-cannula-oxygen-therapy-in-children

mechanical-ventilation-and-ICU-ventilators

Mechanical Ventilation and ICU Ventilators: Learn All Details

by with No Comment Uncategorized

Mechanical ventilation and ICU ventilators are critical components in the management of patients with severe respiratory conditions. Understanding their functionality and application is essential for effective patient care. These technologies play an important role in supporting and stabilizing patients in critical conditions.

What is Ventilation? 

ICU Ventilation is the process of movement of air from the atmosphere through the airways to the terminal respiratory gas exchange units by the effort of the respiratory muscles or mechanical ICU ventilators if the patient is being ventilated. 

What is Respiration? 

Oxygen is essential for life. It is required by each human cell for its survival. It is abundantly present in the atmosphere and maintains a remarkably constant concentration of 20.9% in ambient air. Oxygen is taken up by the lungs through the act of inspiration and transported to the cells via the blood.

At the cellular level, oxygen is utilized for the production of energy. In this process, carbon dioxide is released and transported back via the blood to the lungs from where it is expired out into the atmosphere. The act of the exchange of oxygen and carbon dioxide is called respiration. 

What is the Difference Between ICU Ventilators and Respirator? 

A ventilator is a machine, a system using mechanical power and having several parts, each with a definite function and together performing a particular task. The task here is to provide all or part of the body’s work that is called breathing or ventilation. Respirator is an apparatus that people worn it over their mouth and nose or the entire face to prevent the inhalation of dangerous substances such as: dust, smoke, etc

Indications for Ventilation

Patients who require ventilatory support often develop a common pattern of physiological deterioration, including:

  • changes in respiratory rate
  • asynchronous respiratory pattern
  • changes in mental status and changes in level of consciousness
  • frequent oxygen desaturation despite increasing oxygen concentration
  • hypercapnia and respiratory acidosis
  • circulatory problems, including tachypnea, tachycardia, hypertension, or hypotension.(3)

What is Non-invasive Ventilation (NIV)?

NIV refers to the provision of respiratory support without direct tracheal intubation. As such, it aims to avoid some of the complications inherent with invasive ventilation, such as the need for sedation with risks of hemodynamic instability and subsequent risk of delirium, nosocomial infection, etc.(2)

Recommendations for the use of non-invasive ventilation(4):

  • COPD exacerbations
  • Facilitation of weaning/extubation in patients with COPD
  • Cardiogenic pulmonary edema
  • Immunosuppressed patients
  • Do-not-intubate status
  • End-stage patients as palliative measure
  • Extubation failure (COPD or congestive heart failure) (prevention)
  • Community-acquired pneumonia in COPD
  • Postoperative respiratory failure (prevention and treatment)
  • Prevention of acute respiratory failure in asthma

Goals of Mechanical Ventilation

One of the most important treads of life support in the emergency department is Mechanical ventilation (MV). It provides time for recovery until the patient’s physiological balance is restored. This is why MV alone is not a unique and specific treatment for a particular disease; however, it has two general and main purposes: to support the injured lung and to protect the healthy lung.

Specific Goals of Mechanical Ventilation

  • Reversal of Apnea
  • Reversal of Respiratory Distress
  • Reversal of Severe Hypoxemia
  • Reversal of Severe Hypercapnia
  • Goals of Mechanical Ventilation in Postoperative
  • Respiratory Failure and Trauma
  • Goals of Mechanical Ventilation in Shock

One of the specific goals of MV is to promote the optimization of arterial blood gas levels and acid-base balance by providing oxygen and eliminating carbon dioxide (ventilation).(1) For patients with chronic diseases MV can reduce the work of breathing by taking effort from respiratory muscles and maintaining long-term respiratory support.
The ventilator is not a magical therapy that makes patients better but simply a supportive therapy used until more definitive therapies have time to work.

Apnea

Patients with apnea, such as those who have suffered catastrophic central nervous system (CNS) damage, need the immediate institution of mechanical ventilation.(2)

Indications and Contraindications for Non-invasive Ventilation

Recognizing when and when not to use NIV is crucial for its effective application. Below, we have explained the indications and contraindications for non-invasive ventilation for you

Indications (3)

  • Moderate to severe dyspnoea
  • Tachypnoea (>25–30 breaths/minute)
  • Signs of increased work of breathing (abdominal paradox; accessory muscle use)
  • Fatigue
  • Acute-on-chronic respiratory failure: pH <7.35; pCO2 >6
  • Hypoxaemia (use with caution): paO2/FiO2 <27 Kpa

Contraindications (3)

  • Facial burns/trauma/recent facial upper airway surgery
  • Vomiting
  • Upper gastrointestinal surgery
  • Copious respiratory secretions
  • Severe hypoxemia
  • Hemodynamically instability
  • Severe co-morbidities
  • Confusion/agitation
  • Low Glasgow coma score
  • Unable to protect the airway
  • Bowel obstruction
  • Respiratory arrest

NIV today consists almost exclusively of the delivery of positive pressure ventilation via an external interface. There are six broad types of interfaces available;

  • total face masks (enclose mouth, nose, eyes)
  • full-face masks (enclose mouth and nose)
  • nasal mask (covers nose but not mouth)
  • mouthpieces (placed between lips and held in place by lip seal)
  • nasal pillows or plugs (inserted into nostrils)
  • helmet (covers the whole head/all or part of the neck – no contact with face).(3)

What is Invasive Ventilation?

Invasive mechanical ventilation requires access to the trachea, most commonly via an endotracheal tube, and represents the commonest reason for admission to the ICU.(5)ICU Ventilators.

Large multinational surveys confirm the common indications for invasive ventilation to be:

  • coma 16%
  • COPD 13%
  • ARDS 11%
  • heart failure 11%
  • pneumonia 11%
  • sepsis 11%
  • trauma 11%
  • postoperative complications 11%
  • neuromuscular disorders 5%.
  • NIV contraindications.(5)

Let’s Meet with Biyovent ICU Type Mechanical Ventilator

ICU Ventilators

Biyovent ICU Type Mechanical Ventilator

ICU Ventilator of Biyovent makes a difference in the ventilation process with its unique specifications. Biyovent has been carefully thought out with every detail of the ventilators and developed with a holistic approach. Prepared for mass production in cooperation with Arçelik, Baykar, and Aselsan. ICU Ventilators

What are some specific features of Biyovent?

⦁ Invasive and Non-invasive Ventilation
⦁ Integrated Nebulizer
⦁ High Flow Oxygen Therapy
⦁ Suitable for Pediatric, Adult and Newborn (Optional) Patients
⦁ Smart Ventilation Modes

Learn more details about Biyovent ICU Ventilator

Get in contact with the Biosys Sales Team

References


1- Frank Lodeserto MD, “Simplifying Mechanical Ventilation – Part I: Types of Breaths”, REBEL EM blog, March 8, 2018. Available at: https://rebelem.com/simplifying-mechanical-ventilation-part/.
2- Tobin M.J. 3rd edn. McGraw-Hill Education; 2012. Principles and practice of mechanical ventilation.
3- Popat B, Jones AT. Invasive and non-invasive mechanical ventilation. Medicine (Abingdon). 2012;40(6):298-304. doi:10.1016/j.mpmed.2012.03.010
4- Hess D.R. The evidence for noninvasive positive-pressure ventilation in the care of patients in acute respiratory failure: a systematic review of the literature. Respir Care. 2004;49:810–829.
5- Esteban A., Ferguson N.D., Meade M.O. Evolution of mechanical ventilation in response to clinical research. Am J Respir Crit Care Med. 2008;177:170–177