Posts in category: BioBites

Respiratory support in intensive care has undergone a significant transformation over time, evolving from simple manual techniques to sophisticated, intelligent devices. The initial use of negative pressure ventilation devices such as the “iron lung” in the early 20th century marked the beginning of this journey. A major turning point occurred during the poliomyelitis outbreak in Copenhagen in 1952, when positive pressure ventilation was successfully employed, laying the foundation for modern intensive care practices.

From the 1960s onward, volume- and pressure-controlled mechanical ventilators were developed, offering greater control over respiratory support. The introduction of microprocessor-based ventilators in the 1980s enhanced the precision and safety of mechanical ventilation. By the 2000s, lung-protective strategies—such as the use of low tidal volumes and appropriate levels of PEEP—had become widely adopted.

Over time, non-invasive ventilation techniques (such as BiPAP and CPAP) and high-flow nasal oxygen therapy have also become increasingly prevalent. The COVID-19 pandemic further underscored the critical role of ventilators in the management of acute respiratory failure. Today, respiratory support is delivered via advanced technologies that incorporate artificial intelligence, allow for individualized settings, and prioritize lung-protective strategies.

Respiratory Support in Intensive Care

Respiratory support in intensive care refers to the set of invasive and non-invasive methods employed to ensure adequate oxygenation and carbon dioxide elimination in patients experiencing respiratory failure. It is indicated in cases where the patient is unable to maintain sufficient spontaneous breathing or when it is necessary to reduce the work of breathing. The primary objectives of respiratory support are to optimize gas exchange, protect the lungs, and sustain life until the underlying condition improves.

Types of Respiratory Support

Respiratory support is broadly classified into two main categories:

1. Non-invasive respiratory support:
This form of support is delivered through a face mask or nasal cannula without the need for endotracheal intubation. Common methods include high-flow nasal cannula (HFNC) therapy and non-invasive mechanical ventilation (e.g., BiPAP or CPAP).

2. Invasive respiratory support:
This approach requires the placement of an endotracheal tube into the trachea. It involves mechanical ventilation or, in more advanced cases, extracorporeal membrane oxygenation (ECMO), particularly in severe or refractory respiratory failure.

Indications for Respiratory Support

Respiratory support is indicated in the following conditions:

• Hypoxemic respiratory failure (PaO₂ < 60 mmHg): such as acute respiratory distress syndrome (ARDS), pneumonia, and COVID-19.
• Hypercapnic respiratory failure (PaCO₂ > 45 mmHg): including exacerbations of chronic obstructive pulmonary disease (COPD) and neuromuscular diseases.
• Cardiogenic pulmonary edema
• Postoperative respiratory depression
• Trauma, sepsis, and metabolic disorders

What Is a Mechanical Ventilator?

A mechanical ventilator is a medical device that delivers air to the lungs using positive pressure to support or completely take over the breathing process in patients with respiratory failure. It is used in intensive care units, operating rooms, and emergency departments to temporarily maintain respiratory function in critically ill patients. Mechanical ventilation mimics natural breathing by meeting the body’s oxygen demands, regulating carbon dioxide removal, and allowing the respiratory muscles to rest.

Primary Objectives of Mechanical Ventilation

• To correct hypoxemia (increase oxygen levels)
• To reduce hypercapnia (eliminate excess carbon dioxide)
• To decrease the work of breathing
• To prevent complications through lung-protective ventilation strategies
• To support spontaneous breathing and prepare the patient for weaning from the ventilator

How Is Mechanical Ventilation Used?

1) Preparation and Patient Selection

Mechanical ventilation is typically initiated in the following conditions:

• Acute respiratory failure
• Acute respiratory distress syndrome (ARDS)
• Exacerbation of chronic obstructive pulmonary disease (COPD)
• Systemic conditions such as sepsis, trauma, or brain injury
• Postoperative respiratory depression

The patient is intubated by inserting an endotracheal tube into the trachea, which is then connected to the mechanical ventilator.

2) Mode Selection

The mechanical ventilator can be set to operate in various modes:

• Controlled Mode (AC – Assist/Control): The device initiates and controls every breath; the patient does not contribute to ventilation.
• Supported Mode (SIMV – Synchronized Intermittent Mandatory Ventilation): The patient can breathe spontaneously between mandatory breaths; the ventilator provides support as needed.
• Pressure Support Ventilation (PSV): The ventilator delivers pressure support with each spontaneous breath initiated by the patient.
• Continuous Positive Airway Pressure (CPAP): Provides continuous positive pressure to spontaneously breathing patients.

3) Monitoring

During mechanical ventilation, the following parameters are closely observed:

• SpO₂ (oxygen saturation)
• End-tidal CO₂ (etCO₂)
• Tidal volume and minute ventilation
• Respiratory mechanics (compliance, resistance)
• Alarm systems (e.g., high pressure, low volume, disconnection)

4) Complications and Precautions

• Ventilator-Induced Lung Injury (VILI): To prevent volutrauma, barotrauma, and atelectasis, low tidal volumes and appropriate positive end-expiratory pressure (PEEP) settings should be employed.
• Ventilator-Associated Pneumonia (VAP): Preventive measures such as meticulous oral care and maintaining the head of the bed at a 30–45° elevation are essential.
• Hemodynamic Effects: High levels of positive pressure can reduce venous return and consequently affect cardiac output.
• Diaphragm Atrophy: Prolonged use of full-support ventilation modes may lead to respiratory muscle weakness due to disuse atrophy.

Frequently Asked Questions

1. Is mechanical ventilation the same as oxygen therapy?
   No. Oxygen therapy is typically administered via simple face masks or nasal cannulas. Mechanical ventilation, on the other hand, provides assisted breathing using positive pressure in patients with impaired lung function; it represents a more advanced form of respiratory support.
   
2. Does mechanical ventilation always require intubation?
   No. Non-invasive mechanical ventilation (e.g., BiPAP, CPAP) can be delivered through masks without the need for intubation. However, invasive mechanical ventilation usually requires endotracheal intubation.
   
3. Is dependence on a mechanical ventilator permanent?
   No. Mechanical ventilation is intended as a temporary support. Once the patient’s respiratory muscles regain strength and gas exchange normalizes, a weaning process is initiated to gradually discontinue ventilator support.
   
4. Is mechanical ventilation painful?
   No, the process of mechanical ventilation itself is not painful. However, the presence of an endotracheal tube and the experience of being on the device can cause discomfort. Therefore, patients are often administered sedation and, when necessary, muscle relaxants.

References

• https://www.wsj.com/articles/after-tragedy-an-entrepreneurs-triumph-1b26bd56?utm_
• https://ject.edpsciences.org/articles/ject/pdf/forth/ject250018.pdf?utm_
• https://www.atsjournals.org/doi/full/10.1164/rccm.202211-2174CP?utm_
• https://www.ncbi.nlm.nih.gov/books/NBK578188/?utm_
• https://jamanetwork.com/journals/jama/fullarticle/2769872?utm_

Home mechanical ventilation refers to the support or complete replacement of spontaneous breathing using mechanical ventilator devices in patients with respiratory failure, provided within a home setting. These systems are typically initiated in a hospital environment and transferred to the home once the patient has achieved a stable condition.

Indications for Use

• Chronic respiratory failure (e.g., COPD, ALS, neuromuscular diseases)
• Impaired respiratory control following brain injury or trauma
• Certain conditions such as sleep apnea
• Ongoing care needs following prolonged intensive care treatment

Types of Mechanical Ventilation

1. Invasive Mechanical Ventilation
   • Administered via tracheostomy (a surgically created opening in the neck).
   • Preferred in more severe cases of respiratory insufficiency.
   • Requires continuous medical supervision.
2. Non-Invasive Mechanical Ventilation (NIV)
   • Delivered through a mask (nasal or full-face).
   • Used in cases of sleep apnea or mild to moderate respiratory failure.
   • CPAP and BiPAP devices are the most commonly used types.

Requirements for Home Mechanical Ventilation Care

• Appropriate equipment: Ventilator, oxygen source, suction device, humidifier, pulse oximeter, backup battery
• Protection against power outages: Generator or uninterruptible power supply (UPS)
• Trained caregiver: A family member or professional nurse with appropriate training
• Medical follow-up: Regular monitoring by a pulmonologist, respiratory therapist, and a home healthcare team
• Hygiene: Particularly important for patients with tracheostomies, due to the high risk of infection

Family and Patient Education for HMV

Relatives of patients receiving home mechanical ventilation must be educated on:

• Proper use of the ventilator and related equipment
• Emergency response procedures
• Cleaning and maintenance of the devices
• Breathing exercises and airway clearance techniques

Risks and Considerations

• Risk of infection, especially in tracheostomized patients
• Device malfunction or failure
• Airway obstruction due to secretions or improper positioning
• Ventilator inoperability during power outages, if no backup system is available

Advantages of Home Mechanical Ventilation

• Reduced length of hospital stay
• A more comfortable and familiar living environment
• Positive impact on the patient’s psychological well-being
• Emotional support from being close to family members

Benefits for Patients and Caregivers

There are several essential considerations for patients receiving home mechanical ventilation and the individuals who care for them. The primary goals are to ensure the patient’s safety and to facilitate the caregiver’s responsibilities.

Proper use of respiratory devices is critical for patients to maintain a safe and comfortable life at home. Both the patient and caregiver must receive training on how the ventilator functions, the meanings of alarm signals, and when to seek medical assistance. In addition, spare parts, batteries, and cleaning supplies for the equipment should always be readily available.

Maintaining the patient’s emotional well-being is equally as important as providing physical care. Establishing a consistent daily routine, promoting social interaction, and avoiding prolonged periods in the same position help support both psychological and physical health. Skin care and oral hygiene must not be neglected, especially since infection risk is significantly higher in these patients.

Caregivers must adhere strictly to hygiene protocols, wash their hands frequently, and apply sterile techniques—especially when caring for patients with tracheostomies. Regular cleaning of the equipment, correct usage, and consistent monitoring are essential. At least one person in the household should be trained in basic first aid to respond to emergencies, and precautions must be taken to address potential power outages.

Importantly, the emotional dimension of this process should not be overlooked. Long-term caregivers are at risk of burnout and should seek support and allow time for rest. Regular medical check-ups and professional home care support are vital to maintaining the long-term sustainability of home mechanical ventilation.

FAQs

1. Is home mechanical ventilation safe?
Yes, it is generally safe when proper equipment is used, caregivers are trained, and there is regular medical supervision.

2. What happens in the event of a power outage?
If the ventilator has a battery, it will continue to operate for a limited time. However, a generator or uninterruptible power supply (UPS) should always be available as a backup.

3. Can a patient on mechanical ventilation be fed?
Yes. Depending on the clinical situation, feeding can be done orally or via a feeding tube, under the guidance of a physician or dietitian.

References

• www.thoracic.org

• https://publications.ersnet.org

Intraoperative nerve monitoring is a neurophysiological technique that enables real-time monitoring of nerve function during surgical procedures. This method is employed to preserve the anatomical and functional integrity of nerves. IONM serves as a critical tool, particularly in surgeries where there is a risk of nerve injury, by helping to localize nerves and prevent potential damage.

How Is It Used?

IONM is implemented through the use of devices and electrodes that monitor the electrical activity of nerves. The basic steps are as follows:

1. Surface or needle electrodes are placed either directly on the target nerve or on muscles innervated by that nerve. The muscular responses to stimulation are then recorded.
2. Low-voltage electrical stimuli are delivered to areas near the nerve within the surgical field.
3. The signals generated by these stimuli are continuously monitored on the device screen in real time. Any indication of nerve injury or functional impairment is immediately communicated to the surgeon.

Applications of IONM

IONM is utilized across various surgical fields to enhance patient safety. Its primary applications include:

• Brain and Spinal Surgery: Used in procedures involving areas close to the spinal cord, brainstem, and cranial nerves.
• Head and Neck Surgery: Particularly important in thyroid and parathyroid surgeries for the preservation of the recurrent laryngeal nerve.
• Cardiac and Thoracic Surgery: Crucial for protecting nerve structures surrounding major blood vessels.
• Orthopedic Surgery: Employed in scoliosis and spinal correction surgeries to prevent spinal cord injury.
• Peripheral Nerve Surgery: Essential for preserving nerve function during procedures such as tumor removal or nerve grafting.

Advantages of IONM

• Prevents nerve injury.
• Enhances surgical safety.
• May reduce the duration of postoperative rehabilitation.
• Provides real-time feedback to assist and guide the surgeon during the procedure.

Recent Advances in Intraoperative Nerve Monitoring

In recent years, one of the most notable developments in the field of IONM has been the integration of artificial intelligence-based analysis systems. These systems are capable of interpreting signal changes in real time and can alert surgeons in advance of a potential risk of nerve injury. Monitoring systems integrated with robotic surgery platforms allow surgeons to perform complex procedures with increased precision and safety. Additionally, telemonitoring technologies enable experts to provide remote support to surgical teams, making the use of IONM feasible even in centers with limited access to advanced technology. These advancements not only enhance patient safety but also contribute positively to surgical outcomes.

Frequently Asked Questions

1) Is the use of neuromonitoring mandatory in all surgeries?
No, the use of neuromonitoring is not required for every surgical procedure. However, in operations where there is a risk of nerve injury nerve preservation is of critical importance. In such cases, neuromonitoring facilitates safer surgical intervention by helping the surgeon avoid nerve damage.

2) Is a neuromonitor available in every hospital?
No, not all hospitals are equipped with neuromonitoring systems. University hospitals, training and research hospitals, and some private medical centers—especially those performing advanced surgical procedures—are more likely to have access to this technology.

3) Are neuromonitors operated by doctors?
Neuromonitoring is typically conducted by a neurophysiology technician, clinical neurophysiologist, anesthesiologist, or a healthcare professional trained in this field.

References

• Chansakul C, Nair DR: Evoked potential monitoring. In:Farag E (ed), Anestesia for Spine Surgery. Cambridge, 2012:89-105
• James ML: Anesthetic consideratşons. In: Husain AM, (ed), A Practical Approach to Neurophysiological Intraoperative Monitoring. Demos Medical Publishing, 2008:55-56
• Kothbauer KF, Novak K: Intraoperative monitoring for tethered cord surgery: An update. Neurosurg Focus 16: E8, 2004

SpO₂ stands for peripheral oxygen saturation and indicates the oxygen saturation level in the blood. This value represents the ratio of oxygen-bound hemoglobin to the total hemoglobin. The body requires a certain amount of oxygen to function properly and stay healthy, as low SpO₂ levels can lead to serious complications.

SpO₂ is typically measured non-invasively using a pulse oximeter device placed on the fingertip, earlobe, or toe. This device uses red and infrared light wavelengths to determine the oxygen saturation level of hemoglobin. Normal SpO₂ values are generally considered to range between 95% and 100%. Values below 90% are referred to as hypoxemia, a condition that can negatively impact organ function.

SpO₂ measurement is essential for assessing the efficiency of the respiratory and circulatory systems. It is particularly used for monitoring patients with chronic respiratory diseases, cardiovascular conditions, or those under anesthesia. Low SpO₂ levels may indicate the need for oxygen therapy or other medical interventions.

How is SpO₂ Measured?

SpO₂ is typically measured using non-invasive methods. This measurement is performed through medical devices called pulse oximeters.

Pulse oximeters operate with sensors placed on areas of the body where the skin is thin and blood flow is abundant, such as the fingertip, earlobe, or toe. The device uses two different wavelengths of light to determine the oxygen saturation level of hemoglobin. Oxygenated and deoxygenated hemoglobin absorb these lights at different rates; the device analyzes this difference to calculate the SpO₂ value.

Considerations

1. Movement and Light Interference: Patient movement or ambient light can affect the accuracy of the measurement. Therefore, it is recommended that the patient remains still during the measurement and that ambient lighting conditions are controlled.
2. Circulatory Conditions: Cold extremities or low peripheral perfusion may impede the sensor’s ability to collect accurate data. In such cases, relocating the sensor to a different area or addressing the patient’s body temperature may be necessary.
3. Nail Polish and Artificial Nails: Nail polish or artificial nails can interfere with light absorption, particularly when the sensor is placed on the fingertip, potentially leading to inaccurate results. It is therefore essential to ensure that nails are clean prior to measurement.

Oxygenation Efficiency and SpO₂ Monitoring

Oxygenation efficiency reflects how effectively the body utilizes oxygen. SpO₂ monitoring aids in evaluating this efficiency in the following ways:

• Early Warning System: Decreases in SpO₂ levels can be early indicators of issues in the respiratory or circulatory systems. This allows potential problems to be detected and addressed promptly.
• Assessment of Treatment Effectiveness: In patients receiving oxygen therapy or ventilatory support, SpO₂ monitoring demonstrates the effectiveness of the treatment and facilitates necessary adjustments.
• Management of Chronic Diseases: In conditions such as COPD or asthma, regular SpO₂ monitoring helps track disease progression and prevent exacerbations.

Limitations of SpO₂ Monitoring

While SpO₂ monitoring provides valuable insights into oxygenation efficiency, it has certain limitations:

• Anemic Conditions: In cases of low hemoglobin levels, SpO₂ may appear normal despite insufficient oxygen delivery to tissues.
• Carbon Monoxide Poisoning: Carbon monoxide binds to hemoglobin with greater affinity than oxygen, leading to falsely elevated SpO₂ readings.
• Methemoglobinemia: In this condition, SpO₂ measurements typically stabilize around 85%, providing misleading information about the actual oxygenation status.

Frequently Asked Questions

• What is anormal SpO₂?
  A normal SpO₂ value in a healthy individual typically ranges between 95% and 100%.
• What does low SpO₂ mean?
  Low SpO₂ indicates that the oxygen level in the blood is below normal, suggesting insufficient oxygen delivery to tissues. This condition, known as hypoxemia, can be a sign of serious health issues.

References

• Dcosta, Jostin Vinroy, Daniel Ochoa, and Sébastien Sanaur. “Recent Progress in Flexible and Wearable All Organic Photoplethysmography Sensors for SpO2 Monitoring.” Advanced Science 10.31 (2023): 2302752.
• Mc Namara, Helen M., and Gary A. Dildy III. “Continuous intrapartum pH, pO2, pCO2, and SpO2 monitoring.” Obstetrics and gynecology clinics of North America 26.4 (1999): 671-693.
• Eriş, Ömer, et al. “İnternet Üzerinden Hasta Takibi Amaçlı PIC Mikrodenetleyici Tabanlı Kablosuz Pals-Oksimetre Ölçme Sistemi Tasarımı ve LabVIEW Uygulaması.” VII. Ulusal Tıp Bilişimi Kongresi Bildirileri 16 (2010): 16-25.

EtCO₂ (End-Tidal Carbon Dioxide) refers to the measurement of the carbon dioxide concentration in exhaled air at the end of expiration. It is typically expressed in millimeters of mercury (mmHg) and measured using a capnography device. It provides critical insights into the respiratory system, cardiac circulation, and metabolism.

At the end of the respiratory cycle, during exhalation, EtCO₂ represents the peak concentration of carbon dioxide (CO₂) in the exhaled gas. This value forms the basis of EtCO₂ monitoring. By reflecting the interaction between the respiratory system, circulation, and metabolism, it plays a crucial role in assessing the patient’s overall condition.

• Low EtCO₂: May indicate conditions such as hyperventilation, low cardiac output, or pulmonary embolism.
• High EtCO₂: May suggest hypoventilation, excessive metabolic activity, or inadequate ventilator settings.

Monitoring EtCO₂ levels with mechanical ventilators plays a critical role in evaluating a patient’s respiratory status and the effectiveness of ventilation. This monitoring is performed using capnography devices, which are often integrated into the ventilator system.

EtCO₂ Monitoring Methods

1. Mainstream Capnography
   • How It Works: The sensor is placed between the endotracheal or tracheostomy tube and the breathing circuit. The patient’s exhaled air passes directly through the sensor, and CO₂ concentration is measured in real-time.
   • Advantages: Provides instantaneous and accurate measurements with minimal delay during exhalation.
   • Disadvantages: The sensor’s weight and heat may cause discomfort, particularly for small children or frail patients.
2. Sidestream Capnography
   • How It Works: A small gas sample is drawn from the breathing circuit and delivered to the analyzer within the device. This method can also be used for non-intubated patients.
   • Advantages: Compatible with various breathing circuits and suitable for patients who do not require intubation.
   • Disadvantages: Condensation may accumulate in the sampling line, potentially affecting measurement accuracy.

Ventilation Efficiency Through EtCO₂ Monitoring

EtCO₂ monitoring is a direct method to evaluate ventilation efficiency. It demonstrates how effectively the respiratory system eliminates carbon dioxide (CO₂) and assesses the efficiency of CO₂ removal produced through metabolic processes via ventilation. Ventilation efficiency is evaluated in various clinical conditions using EtCO₂ levels and capnogram analyses.

1. Hypoventilation (Decreased Ventilation):
   • EtCO₂ Level: Increased (typically > 45 mmHg).
   • Cause: Inadequate elimination of CO₂ by the lungs.
   • Clinical Conditions: Respiratory depression, sedation, neuromuscular blockade, obesity hypoventilation syndrome.
   • Effect: Elevated EtCO₂ levels indicate the need to enhance ventilation.
2. Hyperventilation (Increased Ventilation):
   • EtCO₂ Level: Decreased (typically < 35 mmHg).
   • Cause: Excessive elimination of CO₂.
   • Clinical Conditions: Anxiety, pain, response to hypoxia, compensatory mechanisms.
   • Effect: A reduction in ventilation rate or tidal volume may be necessary.
3. Increased Alveolar Dead Space:
   • EtCO₂ Level: Decreased, but arterial CO₂ (PaCO₂) remains elevated.
   • Cause: Reduced pulmonary perfusion or ventilation-perfusion (V/Q) mismatch.
   • Clinical Conditions: Pulmonary embolism, low cardiac output, shock.
   • Effect: The difference between EtCO₂ and PaCO₂ increases (EtCO₂-PaCO₂ gradient).
4. Circulatory Failure:
   • EtCO₂ Level: Decreased.
   • Cause: Reduced cardiac output decreases the amount of CO₂ delivered to the alveoli.
   • Clinical Conditions: Cardiac arrest, low-perfusion shock.
   • Effect: Used to monitor the effectiveness of CPR; an increase in EtCO₂ indicates the restoration of circulation.

FAQs

1. What is the normal EtCO₂ value?
   The normal range is between 35-45 mmHg.
2. What does low EtCO₂ mean?
   Low EtCO₂ refers to a condition where the carbon dioxide level in exhaled air is below normal. This may indicate issues related to ventilation, perfusion, or metabolism. EtCO₂ levels below 35 mmHg are typically referred to as hypocapnia.
3. What are the causes of low EtCO₂ on a ventilator?
   Low EtCO₂ is commonly caused by factors such as hyperventilation, hypoperfusion, airway issues, or decreased metabolic activity.

References

• Aminiahidashti, Hamed, et al. “Applications of end-tidal carbon dioxide (ETCO2) monitoring in emergency department; a narrative review.” Emergency 6.1 (2018).
• Trilĺo, Giulio, Martin von Planta, and Fulvio Kette. “ETCO2 monitoring during low flow states: clinical aims and limits.” Resuscitation 27.1 (1994): 1-8.
• Miner, James R., William Heegaard, and David Plummer. “End‐tidal carbon dioxide monitoring during procedural sedation.” Academic Emergency Medicine 9.4 (2002): 275-280.
• Paiva, Edison F., James H. Paxton, and Brian J. O’Neil. “The use of end-tidal carbon dioxide (ETCO2) measurement to guide management of cardiac arrest: a systematic review.” Resuscitation 123 (2018): 1-7.