Assessment

Respiratory assessment

Which basic investigationsmay be used in assessing respiratory function?

Following basic clinical examination of the chest during a respiratory examination, investigationsmay include

Non-invasive

• Peak expiratory flow rate (PEFR): a bedside measure of the airway resistance and respiratory muscle function

• Pulse oximetry:measures arterial oxygen saturation (SaO2) and heart rate

• Capnography:measures end-tidal CO2 as a marker of ventilatory function

• Pulmonary function tests (PFTs)

▪ Spirometry, to measure lung volumes charted on a Vitalograph®, e.g. functional expiratory volume in 1 second (FEV1) and functional vital capacity (FVC). The FEV1/FVC is a measure of airflow limitation and is normally>80%. Other tests include total lung capacity (TLC) and residual volume (RV). These are useful in patients who have obstructive lung disease, e.g. asthma and COPD

▪ Gas transfer, a measure of the diffusing capacity across the lung, e.g. transfer factor (DLco), which measures the transfer of low carbon monoxide concentrations in inspired air to haemoglobin, and transfer coefficient (Kco), which is the DLco corrected for alveolar volume

• Microbiology analysis: of sputum and retained secretions, including culture and cytology

• V/Q scanning: if pulmonary emboli are suspected

• Echocardiography: to assess pulmonary artery pressure and right heart function in cases of pulmonary hypertension and cor pulmonale

• Radiology: plain chest radiography, high-resolution CT, MRI

Invasive

• Arterial blood gas (ABG) analysis: directly measures oxygenation (PaO2), ventilation (PaCO2) and acid–base balance

• Bronchoscopy:may be flexible or rigid

• Lung biopsy:may be performed through a CT-guided approach or video-assisted thoracoscopic surgery (VATS).

• Rare cases may dictate an open operation

• Mediastinoscopy: performed through an incision at the root of the neck, permitting biopsies of regional tracheobronchial lymph nodes for staging pulmonary or oesophageal malignancy

• Pulmonary positron emission tomography (PET): is a gold standard diagnostic procedure for evaluating the structure and function of pulmonary lesions, e.g. nodules or emboli

What are the applications of flexible (fibre optic) bronchoscopy?

• The applications may be both diagnostic and therapeutic

• Direct visualisation of the tracheobronchial tree in cases of obstruction, e.g. retained secretions during atelectasis and aspiration of gastric contents. It may be performed through the endotracheal tube in the mechanically ventilated patient

• Biopsy for cytology or histology, which may be obtained by direct sampling or by brushings and bronchoalveolar lavage (BAL), e.g. during suspected malignancy or infection