This section of our NREMT Study Guide will prepare you for the ventilation portion of the exam. We will cover normal ventilation, ventilation/perfusion ratio and mismatch, factors that affect pulmonary ventilation, and ventilation techniques when providing rescue breathing for patients who are apneic and have a pulse or for patients who are breathing inadequately. Ventilating while performing cardiopulmonary resuscitation (CPR) will be covered in the following study guide, Cardiology & Resuscitation.
At the end of this section, there are five practice questions to assess your understanding and retention of the material covered.
Normal Ventilation
The physical act of the chest wall expanding and retracting during breathing helps the circulatory system return blood to the heart. During normal ventilation, the chest wall movement works similarly to a pump. The pressure changes in the thoracic cavity help draw venous blood back to the heart.
However, when positive-pressure ventilation is initiated, more air is needed to achieve the same oxygenation and ventilatory effects of normal breathing. This increase in airway wall pressure causes the walls of the chest cavity to push out of their normal anatomic shape. As a result, there is an increase in the overall intrathoracic pressure. This pressure increase affects the return of venous blood to the heart.
Considering that the left side of the heart receives only what the right side gives it, reduced venous return would result in reduced cardiac output. Therefore, it is imperative that you regulate the rate and volume of artificial ventilation to help prevent this drop in cardiac output.
Ventilation/Perfusion Ratio and Mismatch
The lungs place ambient air in proximity to circulating blood, which allows gas exchange by diffusion. For this to happen, ventilation (air flow) and perfusion (blood flow) must be directed to the same location at exactly the same time. When ventilation and perfusion are not adequately matched, there can be an abnormal exchange between oxygen and carbon dioxide. When they are not matched, gas exchange cannot be satisfactorily accomplished, leading to hypoxia and severe hypoxemia if the condition is left untreated.
Factors That Affect Pulmonary Ventilation
Without a patent airway, oxygen cannot be delivered to the body’s tissues. Many factors can cause airway obstructions and affect pulmonary ventilation. These factors are called intrinsic and extrinsic factors.
Intrinsic factors act from within the body, such as allergic reactions, unresponsiveness (causing obstruction from the tongue), and infections with swelling of the airways. These intrinsic factors can cause significant problems with maintaining a patent airway if not aggressively treated with airway adjuncts and certain medications.
Extrinsic factors are influenced outside the body, including foreign body airway obstruction and trauma. Any trauma to the chest, airway, or structures supporting the airway requires immediate assessment and intervention. Consider that fractures to the mandible, structural damage to the thorax from chest wall trauma, burns, and blunt or penetrating trauma can disrupt airflow, resulting in oxygen deficiencies and difficulties with pulmonary ventilation.
Patients who are not breathing or are breathing inadequately need 100% oxygen and artificial or assisted ventilation. Assisting a patient by providing ventilation is one of the most important skills you must master as an EMT, as the patient will die if ventilation is not provided.
EMTs have two treatment options: continuous positive airway pressure (CPAP) and assisted ventilation with a bag-valve-mask (BVM), the latter of which is most commonly used in the field, as not all jurisdictions carry or allow EMTs to use CPAP.
Patients in severe respiratory distress or respiratory failure are not breathing adequately and need quick medical intervention. Assisted ventilation increases oxygenation and the ventilatory status in patients who are not breathing adequately.
Ventilation Techniques
After assessing a patient’s ABCs and opening their airway when needed, artificial ventilation may be required if the patient does not spontaneously breathe on their own or is breathing inadequately. The bag-valve-mask (BVM), also known as a bag-mask device, is an oxygen-delivery device used to ventilate patients while providing 100% oxygen. BVMs come in infant, pediatric, and adult sizes and consist of a self-inflating bag, a one-way valve, a face mask, and an oxygen reservoir.
A bag-mask device should be used when you need to deliver high concentrations of oxygen to patients who are not ventilating adequately. The bag-mask device may be used with or without oxygen. However, to ensure the highest concentration of delivered oxygen, you must attach supplemental oxygen and a reservoir. Use an oral or nasal airway adjunct in conjunction with the BVM.
Ventilating an Apneic Patient With a Pulse
Ventilating infants and children is performed slightly faster than adults, as they do not have the oxygen reservoirs that adults have. When providing ventilation on an apneic patient with a pulse, the ventilation rates for each age group are as follows:
- Infant: 1 breath every 2 to 3 seconds
- Child: 1 breath every 2 to 3 seconds
- Adult: 1 breath every 6 seconds
Ventilating a Patient With Inadequate Ventilation
When a patient is breathing poorly, their body cannot maintain adequate oxygen levels and they become hypoxic. Inadequate breathing (respiratory distress) presents as very slow breathing or fast, shallow breathing.
Signs and symptoms of a patient who is not ventilating adequately include:
- Altered mental status
- Inadequate minute volume
- Accessory muscle use
- Fatigue from labored breathing
Patients exhibiting these signs need immediate treatment. Follow these steps to assist a spontaneously breathing patient’s ventilations using a bag-valve-mask:
- Explain the procedure to the patient, as they may feel as if you are trying to suffocate them.
- Place the mask over the patient’s nose and mouth, providing a good seal.
- Squeeze the bag each time the patient takes a breath, maintaining the same respiratory rate as the patient.
- After the initial 5 to 10 breaths, slowly adjust the rate and deliver an appropriate tidal volume.
- Adjust the rate and tidal volume to maintain an adequate minute volume.
Indications of Adequate Ventilation
Sometimes, you will encounter difficulty ventilating certain patients. If a patient has a complete or partial airway obstruction, it will be challenging to squeeze the bag on the BVM. In that case, attempt to clear the airway obstruction by performing abdominal thrusts in adults and chest thrusts/back slaps in pediatric patients and suction as needed. Without a patent airway, the patient is not benefitting from your ventilation.
When you are performing adequate ventilatory assistance, there are several indications that ventilation is adequate:
- An equal rise and fall of the chest with each ventilation
- The heart rate returns to normal
- The patient’s skin color improves and turns pink
- The patient’s respiratory status improves
Assisting Ventilation Using CPAP
Another non-invasive way to provide ventilatory assistance to patients in respiratory distress is by continuous positive airway pressure (CPAP). CPAP is an excellent tool to treat patients in respiratory distress due to obstructive pulmonary disease and acute pulmonary edema. Follow local protocols, as not all EMTs are trained in using CPAP.
The following are requirements for using CPAP:
- The patient is alert, oriented, and able to follow commands
- The patient is displaying signs and symptoms of moderate to severe respiratory distress from an underlying condition, such as COPD or pulmonary edema
- The patient is breathing greater than 26 breaths per minute
- The pulse oximetry reading is less than 90%
Contraindications to using CPAP:
- Patients in respiratory arrest
- Patients with a stoma
- Chest trauma or signs and symptoms of a pneumothorax
- Active vomiting or gastrointestinal bleed
- Patients who cannot follow verbal commands
To use CPAP on patients who meet the guidelines, follow these steps:
- Check your equipment, then connect the circuit to the CPAP generator. Ensure the generator is connected to oxygen and a power source if required.
- Connect the face mask to the circuit tubing and set the device to “on” if there is an on/off button.
- Connect the tubing to the oxygen tank and confirm the device is working.
- Explain the procedure to the patient. Place the mask over the patient’s nose and mouth, creating an airtight seal. Allow the patient to hold the mask to their face first if they are anxious about having the mask strapped to their face.
- Once the mask is firmly in place, use the strapping mechanism to secure it to the patient’s head, following the manufacturer’s recommendations.
- Adjust the pressure valve and the FiO2 to maintain adequate ventilation and oxygenation.
Observe the patient to see if their oxygenation improves and their work of breathing decreases. If the patient deteriorates or their condition does not improve, discontinue CPAP use.