The Royal Marsden Hospital Manual of Clinical Nursing Procedures - Lisa Dougherty [437]
Related theory
Excessive respiratory secretions may be due to increased mucus production in cases of infection, impaired mucociliary transport or a weak cough reflex (Hess 2002). Lower airway secretions that are not cleared provide an ideal medium for bacterial growth. Suitable microbiological analysis in diagnosing infection will depend upon (HPA 2008a):
the adequacy of lower respiratory tract specimens
avoidance of contamination by upper respiratory tract and oral flora
use of microscopic techniques and culture methods
current and recent antimicrobial therapy.
Evidence-based approaches
Rationale
The main aim of sputum/secretion collection is to provide reliable information on the causative agent of bacterial, viral or fungal infection within the respiratory tract and its susceptibility to antibiotics for guiding treatment (Ioanas et al. 2001).
Indications
A respiratory tract secretion specimen is indicated:
when there are clinical signs and symptoms of a chest infection, such as a productive cough, particularly with purulent secretions
if there are signs of systemic infection or in patients with a PUO.
Methods of non-invasive and semi-invasive sampling
Obtaining a sputum sample
Sputum is a combination of mucus, inflammatory and epithelial cells, and degradation products from the lower respiratory tract (Dulak 2005). It is never free from organisms since material originating from the lower respiratory tract has to pass through the pharynx and the mouth, which have commensal populations of bacteria (Thomson 2002). However, it is important to ensure that material sent to the microbiology laboratory is of sputum rather than a saliva sample, which will contain squamous epithelial cells and be unrepresentative of the underlying pulmonary pathology.
Sputum produced as a result of infection is usually purulent and a good sample can yield a high bacterial load (Weston 2008). For patients who are self-ventilating, co-operative, able to cough and expectorate, and able to follow commands, a sputum sample is a suitable collection method. A sufficient quality of sputum will yield a representative specimen and an early morning specimen is thought to be of the best quality (Weston 2008). In cases of suspected Mycobacterium tuberculosis, three sputum specimens need to be collected on consecutive days before the pathogenic organisms can be isolated and appropriate treatment initiated.
Legal and professional issues
Competencies
Practitioners must be competent and feel confident that they have the knowledge, skill and understanding to undertake respiratory tract secretion sampling for microbiological analysis (NMC 2008a). For more advanced skills of specimen collection such as suctioning, the practitioner should receive training and be assessed on their knowledge and understanding of the technique and potential adverse effects that may occur such as hypoxia, cardiovascular instability and mucosal trauma (Thomson 2000). Bronchoalvolar lavage is normally performed by a member of the medical team who has received specialist training and has been deemed competent in the skill.
Preprocedural considerations
Equipment
The use of vacuum-assisted and invasive suctioning techniques requires a comprehensive assessment of clinical indication and safety considerations. These include the following.
The use of an appropriately sized, single-use, multi-eyed suction catheter which causes less tracheal mucosal trauma (NHSQIS 2007). If suctioning through an ETT, the suction catheter diameter should be half the diameter or less which prevents occlusion of the airway and avoids generation of large negative intrathoracic pressures (Thomson 2000) (see Table 11.5).
The use of the lowest effective suction pressure that is high enough to clear secretions whilst avoiding trauma to the bronchial mucosa.
Ensuring suction duration time of <10 seconds to decrease the