Bronchoscopic Diagnosis of Severe Respiratory Infections

Abstract

The diagnosis of severe respiratory infections in intensive care remains an area of uncertainty and involves a complex balancing of risks and benefits. Due to the frequent colonisation of the lower respiratory tract in mechanically ventilated patients, there is an ever-present possibility of microbiological samples being contaminated by bystander organisms. This, coupled with the frequency of alveolar infiltrates arising from sterile insults, risks over-treatment and antimicrobial-associated harm. The use of bronchoscopic sampling to obtain protected lower respiratory samples has long been advocated to overcome this problem. The use of bronchoscopy further enables accurate cytological assessment of the alveolar space and direct inspection of the proximal airways for signs of fungal infection or alternative pathologies. With a growing range of molecular techniques, including those based on nucleic acid amplification and even alveolar visualisation and direct bacterial detection, the potential for bronchoscopy is increasing concomitantly. Despite this, there remain concerns regarding the safety of the technique and its benefits versus less invasive sampling techniques. These discussions are reflected in the lack of consensus among international guidelines on the topic. This review will consider the benefits and challenges of diagnostic bronchoscopy in the context of severe respiratory infection.

Keywords: bronchoscopy; intensive care; pneumonia; respiratory infections.

Figure 1

Anatomy of the human lung. The surface anatomy of the human lung divided into bronchopulmonary segments is shown here, viewed from the front. Numbered segments correspond to the airway shown in the bronchial tree (i.e., the right upper lobe apical segment 1 corresponds to its segmental bronchus, RB1). The right upper lobe bronchus is divided into three segmental bronchi (RB1–3), the right middle lobe bronchus into two segmental bronchi (RB4–5), and the right lower lobe bronchus into five segmental bronchi (RB6–10). The left upper lobe bronchus gives rise to a fused apicoposterior segment (LB1+2) and an anterior segment (LB3). The lingula bronchus is divided into two segmental bronchi (LB4–5), and the left lower lobe bronchus into five segmental bronchi (LB6–10). In the surface anatomy diagram, the apical (6) and medial (7) segments of the lower lobes are not seen as they are posterior. Solid lines indicate major fissures, while dotted lines indicate non-fissural borders between segments. Green segments show the upper lobes, red segments show the middle/lingula lobes and blue segments show the lower lobes. C, cricoid cartilage; T, trachea; RMB, right main bronchus; LMB, left main bronchus; BI, bronchus intermedius.

Figure 2

Major carinae of the human bronchial tree. Representative pictures of carinae from the human bronchial tree as seen during selective endobronchial intubation. (A) The main carina with the right (RL) and left (LL) main bronchi seen during left main stem intubation. (B) Canonical right upper lobe anatomy, with segments RB1-3 shown. (C) View from the right bronchus intermedius showing the common right lower lobe (RLL) and right middle lobe (RML) bronchi. Arrows show segmental carinae for segments RB4-10. (D) View from the left main bronchus, showing the left upper lobe (LUL) and left lower lobe (LLL) bronchi. Above is the view from the LUL bronchus, leading to the upper lobe proper (LB1+2 and LB3) and lingula (LB4–5). Below this are the LLL basal segments (LB8–10). LB6 is seen at the left main carina, and LB7 is not shown. This figure was adapted from Liang et al. [20] under a creative commons CC BY-NC-ND 4.0 licence (https://creativecommons.org/licenses/by-nc-nd/4.0/).

Figure 3

Common complications of ICU bronchoscopy. Categories of complications of bronchoscopy include cardiovascular (bleeding, bradycardia, hypotension); respiratory (hypercapnia, hypoxia, bronchospasm, pneumothorax); and symptomatic (pain, breathlessness, cough). These can be mitigated by measures frequently used in the ICU, such as sedation. Importantly for ICU bronchoscopy, meticulous attention must be given to endotracheal tube security to prevent displacement.