By Samuel Nadler, MD, PhD

Critical Care, Pulmonary Medicine, The Polyclinic Madison Center, Seattle; Clinical Instructor, University of Washington, Seattle

Dr. Nadler reports no financial relationships relevant to this field of study.

SYNOPSIS: After 12 hours of intubation, most patients showed laryngeal injury, including mucosal ulceration, that led to impaired breathing and voicing 10 weeks after extubation.

SOURCE: Shinn JR, Kimura KS, Campbell BR, et al. Incidence and outcomes of acute laryngeal injury after prolonged mechanical ventilation. Crit Care Med 2019;47:1699-1706.

Tracheal intubation is a common medical procedure, often for a limited time. However, many patients in the intensive care unit (ICU) are intubated for 12 hours or more. Intubation for this length of time is understood to cause tracheal injuries due to the deformation of the endotracheal tube by the posterior tongue placing pressure on the posterior glottis. The true incidence of these injuries has not been evaluated contemporaneously with extubation, but rather they have been studied once symptoms arise.

The current study prospectively evaluated patients with prolonged intubation for the presence of laryngeal injury. In a single center, patients 18 years of age or older who were intubated for more than 12 hours underwent endoscopic evaluation of the trachea within 36 hours of extubation. Patients who presented with tracheostomies, known laryngeal injuries, or previous radiation exposures were excluded. Acute laryngeal injury (ALgI) was defined by one or more features, such as glottic mucosal ulceration/granulation or subglottic granulation tissue/stenosis. For this study, researchers screened 833 patients to identify 487 who survived to extubation, 100 of whom underwent nasolaryngoscopy. ALgI was documented in 57 of these patients.

In a multivariate logistic regression, a larger endotracheal tube (ETT) size, the presence of diabetes, and elevated body mass index (BMI) were shown to predict ALgI. There was no significant difference between the groups regarding Acute Physiology and Chronic Health Evaluation (APACHE) scores, pressor needs, steroid use, delirium, or acute respiratory distress syndrome (ARDS). Ten weeks after extubation, patients were contacted by phone and validated questionnaires were administered to evaluate for voice and breathing changes. The Voice Handicap Index (VHI)-10 and Clinical Chronic Obstructive Pulmonary Disease Questionnaire (CCQ) were used. Of the 67 patients who completed the questionnaires, a higher proportion of patients with ALgI reported breathing and voice concerns compared to patients without ALgI.

COMMENTARY

This prospective study demonstrated a high incidence of laryngeal injury (57%) in patients intubated for more than 12 hours. Both modifiable and unmodifiable factors contributed to the injuries. Clearly, the patient’s weight, BMI, and the presence of diabetes cannot be controlled. However, the length of intubation and the size of the ETT can be prospectively changed. Although not statistically significant, for each three-day increase in duration of intubation, the odds ratio (OR) for ALgI increased by 1.49 (95% confidence interval (CI), 0.79-2.82; P = 0.22). Compared with 7.5 mm ETTs, 7.0 mm ETTs showed an OR for ALgI of 0.04 (95% CI, 0.004-0.43; P = 0.007). When compared with 8.0 mm ETTs, the use of 7.0 ETTs had an OR for ALgI of 0.03 (95% CI, 0.003-0.31; P = 0.003). The authors delineated those patients with “appropriately” or “inappropriately” sized ETTs based on previous morphometric studies.1 Although with a smaller group size, the difference was not statistically significant, patients with “inappropriately” sized ETTs had a higher incidence of ALgI (76.5% vs. 53%, P = 0.075). Interestingly, critical care and emergency medicine providers tended to place larger ETTs compared with anesthesiologists and other emergency medical personnel.

This study also examined difficulties patients experienced with vocalization and breathing 10 weeks after extubation. Patients with ALgI reported worse voice outcomes compared to those without ALgI (median VHI 2 vs. 0; P = 0.005), although the minimal clinically significant change for this metric is 4. The CCQ is used more commonly to evaluate populations with chronic obstructive pulmonary disease, but with this application, patients with ALgI reported worse breathing compared to those without ALgI (median CCQ 1.05 vs. 0.20; P < 0.001) with the minimal clinically significant change being 0.4. Thus, even 10 weeks after extubation, patients with ALgI experienced clinically significant changes in breathing.

Intubation for more the 12 hours is common in the ICU, and laryngeal injury is common in this group. Patients with ALgI had a higher incidence of persistent breathing difficulties compared with patients without ALgI, even 10 weeks after extubation. This risk of ALgI and long-term breathing difficulties may be reduced by using smaller ETTs and extubating patients as soon as is safe.

REFERENCE

  1. Coordes A, Rademacher G, Knopke S, et al. Selection and placement of oral ventilation tubes based on tracheal morphometry. Laryngoscope 2011;121:1225-1230.