Goals in Mechanical Ventilation: Concepts for the Students

Goals in Mechanical Ventilation: Concepts for the Students
Authors: Dr. Job Heriberto Rodríguez Guillén (@job_rdz), Dr. Sergio Edgar Zamora Gómez (@ezg_galeno)

Introduction

Mechanical ventilation (MV) is one of the cornerstones of life support in the emergency department. It provides time for establishing therapeutic management aimed at the triggering cause of injury until the patient improves physiologic balance (1). Therefore, MV can not be a unique and specific treatment for any disease by itself; but it has two general and fundamental goals: to support the injured lung and protect the healthy lung.

Set your goals: Support and Protect

Support

MV supports the respiratory system; meanwhile, the primary disease becomes under control.

Example: A patient with acute respiratory distress syndrome (ARDS) due to pneumonia, where MV provides support to improve gas exchange and reduce work of breathing (WOB) meanwhile antibiotic treatment induces remission of the infectious disease.

Protect

MV is aimed to avoid complications not related to the primary disease. The patient-ventilator relationship becomes of benefit for the patient as his respiratory function is in the risk of injury because the primary disease does not allow him to breathe properly or because therapeutic interventions can reduce protective airway reflexes and lead to respiratory complications.

Example: Patients presenting neuromuscular diseases (Guillain-Barre syndrome), diseases affecting bulbar muscles (myasthenic crisis), decreased consciousness (stroke, poisoning) or severe traumatic brain injury, all these without lung injury at first but in high risk of pneumonitis and pneumonia due to aspiration of gastric content.

Goals of Mechanical Ventilation
Mechanical ventilation has two general and fundamental goals: to support the injured lung and protect the healthy lung.

Specific goals of mechanical ventilation

One of the specific objectives of MV is to promote the optimization of arterial blood gases levels and acid-base balance by providing oxygen and eliminating carbon dioxide (ventilation). MV can reduce the work of breathing by taking effort from respiratory muscles and maintaining the long-term respiratory support for patients with chronic diseases.

MV´s circle (2) begins by recognizing the patient´s need for mechanical ventilatory support. Intubation and ventilation decision making is an essential skill for emergency physicians. Consideration of the patient´s needs is the basis of this decision making. The main indications for intubation and mechanical ventilation are (3):

  1. Refractory hypoxemia
  2. Increased respiratory effort
  3. Apnea/hypopnea leading to inadequate ventilation (Hypercapnia)
  4. The inability for airway protection

The goals should be individualized and established according to the clinical situation that led the patient to required ventilatory support. Although standard criteria traditionally have been specified for the onset of MV (3), we must remember that indication for intubation and ventilation is an essential skill for every physician treating critical care patients and the key is just thinking about what the patient needs.

Standard criteria for starting mechanical ventilation
Acute Ventilatory Failure
pCO2 > 50 mmHg + pH < 7.30
Impending Ventilatory Failure
Maintains normal gasometric levels by increasing respiratory effort.
Severe Hypoxemia
pO2 < 60 mmHg + FiO2 > 50%

pCO2 and pO2 values at sea level

In general, we can encompass the specific objectives of MV in three fundamental principles that must be fulfilled in every patient by setting the goals according to the primary disease:

  1. Improve oxygenation (O2) and ventilation (CO2)
  2. Reduce respiratory effort
  3. Minimize ventilator-induced lung injury (VILI)

Conclusions

The goals of MV are established based on the primary disease that led the patient to need MV support, under the concept of protecting and supporting the lungs. Primum non nocere; lung-protective ventilation should be initiated in all patients who need it.

References and Further Reading

  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. Frank Lodeserto MD, “Simplifying Mechanical Ventilation – Part 2: Goals of Mechanical Ventilation & Factors Controlling Oxygenation and Ventilation”, REBEL EM blog, May 18, 2018. Available at: https://rebelem.com/simplifying-mechanical-ventilation-part-2-goals-of-mechanical-ventilation-factors-controlling-oxygenation-and-ventilation/.
  3. Scott Weingart. EMCrit Lecture – Dominating the Vent: Part I. EMCrit Blog. Published on May 24, 2010. Accessed on August 30th 2019. Available at [https://emcrit.org/emcrit/vent-part-1/ ].
Cite this article as: Job Guillen, "Goals in Mechanical Ventilation: Concepts for the Students," in International Emergency Medicine Education Project, September 2, 2019, https://iem-student.org/2019/09/02/goals-in-mechanical-ventilation-concepts-for-the-students/, date accessed: September 16, 2019

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