Page 370 - ACCCN's Critical Care Nursing

Respiratory Assessment and Monitoring 347

Magnetic Resonance Imaging Fiberoptic bronchoscopy is a relatively safe procedure,
Magnetic resonance imaging (MRI) uses radiofrequency even in critically ill patients, when performed by an expe-
waves and a strong magnetic field rather than X-rays to rienced operator. In mechanically ventilated patients,
provide clear and detailed pictures of internal organs and insertion of the bronchoscope into the artificial airway
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soft tissues. These high-contrast images of soft tissue are can lead to decreases in tidal and minute volumes result-
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clearer than those generated by X-ray or CT scans. The ing in decreased PaO 2 and increased PaCO 2 . Serious
strong magnetic field around the scanner means that fer- complications such as bleeding, bronchospasm, arrhyth-
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romagnetic objects (metallic objects containing material mia, pneumothorax and pneumonia occur rarely.
that can be attracted by magnets, such as iron or steel) Patient preparation pre-procedure may include chest
can become potentially fatal projectiles. MRI scans may X-ray; haemoglobin and coagulation profile, particularly
therefore be unsuitable for patients with implanted pace- if a biopsy is to be performed; arterial blood gases as a
makers, defibrillators or neurostimulation devices; some baseline measurement; and fasting or have feeds ceased
types of intracranial aneurysm clips; and loose dental for 4–6 hours prior.
fillings. The magnetic force can either attract these items Diagnostic indications include further investigation of
and dislodge them from the body or interfere with their poor gas exchange; evaluation of haemoptysis; collection
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functioning. The strong magnetic fields also have the of specimens (e.g. bronchoalveolar lavage, bronchial
potential to interfere with ventilators, infusion pumps washings, bronchial brushings, lung biopsy) to assist
and monitoring equipment. Similar to CT scans, an MRI in diagnosis of infection, interstitial lung disease, rejec-
requires transport of the critically ill patient. The benefits tion post-lung transplantation and malignancy; and
of the diagnostic data obtained from the MRI is balanced diagnosis of airway injury due to burns, aspiration or
against any potential risk to the patient. 77 chest trauma. Therapeutic indications include removal
of mucous plugs; removal of foreign bodies; treatment
Ventilation/Perfusion Scan of atelectasis; assistance during tracheostomy; airway
The ventilation/perfusion (V/Q) scan is indicated when dilatation and stenting for tracheobronchomalacia and
a mismatch of lung ventilation and perfusion is sus- tracheobronchial stenosis; and lung volume reduction
pected; the most common indication is for pulmonary for emphysema. 79,83
embolism. The ventilation scan is performed with the
patient inhaling a radioisotopic gas to demonstrate ven- SUMMARY
tilation of the lung, while the perfusion scan is performed
using an intravenous radioisotope that reveals distribu- This chapter provided a comprehensive overview of
tion of blood flow in the blood vessels of the lungs. assessment and monitoring of a patient with respiratory
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These two scans are then compared, with mismatches in dysfunction, to produce relevant data for clinical decision
perfusion and ventilation identified. In larger centres, the making. Acute respiratory dysfunction is a major cause
V/Q scan has been superseded by the use of CT pulmo- for admission to a critical care unit. Whether a primary
nary angiogram (CTPA) for detection of pulmonary or a secondary condition, compromise of the respiratory
embolism. system can lead to a life-threatening situation for a
patient. This chapter outlines related respiratory physio-
logy, pathophysiology, assessment and respiratory moni-
BRONCHOSCOPY toring, bedside laboratory investigations and medical
Bronchoscopy is a bedside technique used for both diag- imaging points. Importantly:
nostic and therapeutic purposes. The bronchoscope can ● Critical care nurses are in a prime position at the
be either rigid or flexible; the most widely used type in beside to provide systematic and dynamic assess-
critical care is the flexible fibreoptic bronchoscope. A flex- ments of a patient’s respiratory status; this includes
ible fibreoptic bronchoscope allows direct visualisation history-taking of past and present respiratory prob-
of respiratory mucosa and thorough examination of the lems, and physical examination of the thorax and
upper airways and tracheobronchial tree. The scope is lungs using inspection, palpation and auscultation
passed into the trachea via the oropharynx or nares. In techniques.
mechanically-ventilated patients, the scope can be passed ● Monitoring a patient’s respiratory function includes
quickly and easily down the endotracheal (ETT) or tra- pulse oximetry, and capnography for a patient with
cheostomy tube (TT) allowing rapid access to the non-invasive or invasive mechanical ventilation; pulse
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airways. Supplemental oxygen can be administered oximetry provides non-invasive measurement of arte-
during the bronchoscopy in non-intubated patients and rial oxygen saturation of haemoglobin, and is regarded
FiO 2 can be increased in intubated patients. Accurate con- as standard practice in ICU.
tinuous monitoring during the procedure includes con- ● Bedside and laboratory investigations add to available
tinuous pulse oximetry, electrocardiography, respiratory information regarding a patient’s respiratory status
rate, heart rate and blood pressure. Equipment for and assists in the diagnosis and treatment of a criti-
advanced airway management, suctioning, cardiac defi- cally ill patient; this includes arterial blood gas analy-
brillation and advanced life support medications is sis; blood testing; and sputum and tracheal aspirates.
immediately available. In intubated patients, one person ABG is a commonly performed laboratory test, and
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is responsible for security of the airway as there is a risk ABG interpretation is an important clinical skill for
that it may become displaced during the procedure. critical care nurses.