Cough reflex in lung transplant recipients

A prospective examination of swallow and cough dysfunction after lung transplantation

OBJECTIVES

Swallow and cough dysfunction are possible surgical complications of lung transplantation (LT). We examined voluntary cough strength, sensorimotor reflexive cough integrity, and swallow-related respiratory rate (RR) across swallowing safety and aspiration response groups in recovering LT recipients.

METHODS

Forty-five LT recipients underwent flexible endoscopic evaluation of swallowing indexed by the validated Penetration Aspiration Scale. RR before and after a 3-ounce water drinking task was measured. Voluntary and reflexive cough screening were performed to index motor and sensory outcomes. T-tests, one-way ANOVAs, and chi-square (odds ratios) were used.

RESULTS

60% of patients exhibited laryngeal penetration (n = 27) and 40% demonstrated tracheal aspiration (n = 18); 72% (n = 13) demonstrated silent aspiration. Baseline RR was higher in aspirators versus non-aspirators (26.5 vs. 22.6, p = 0.04) and in silent aspirators compared to non-silent aspirators (27.9 vs. 20.7, p = 0.01). RR change post-swallowing did not differ between aspiration response groups; however, it was significantly higher in aspirators compared to non-aspirators (3 vs. -2, p = 0.02). Compared to non-silent aspirators, silent aspirators demonstrated reduced voluntary cough peak expiratory flow (PEF; 166 vs. 324 L/min, p = 0.01). PEF, motor and urge to cough reflex cough ratings did not differ between aspirators and non-aspirators. Silent aspirators demonstrated a 7.5 times higher odds of failing reflex cough screening compared to non-silent aspirators (p = 0.07).

CONCLUSIONS

During the acute recovery period, all LT participants demonstrated some degree of unsafe swallowing and reduced voluntary cough strength. Silent aspirators exhibited elevated RR, reduced voluntary cough physiologic capacity to defend the airway, and a clinically distinguishable blunted motor response to reflex cough screening.

Esophageal Dysfunction in Post-lung Transplant: An Enigma

The prevalence of lung transplants has increased over the years, albeit with a low survival rate amongst all solid organ transplants, including liver and heart transplantation. Microaspiration is one of the primary mechanisms that has been implicated in the pathogenesis of lung injury following lung transplants. Of late, esophageal dysfunction such as gastroesophageal reflux and esophageal hypercontractility is often noted post-lung transplant. However, reflux is associated with chronic allograft lung injury such as bronchiolitis obliterans syndrome, which is one of the predictors for long-term survival in this specialized population. Its role in acute lung injury post-lung transplant is still being explored. This review critically examines the salient points which provide the current understanding of the characteristics, pathophysiology, and implications of esophageal dysfunction following lung transplant.

Infectious Complications in Lung Transplant Recipients

Infection remains a common cause of death throughout the lifespan of a lung transplant recipient. The increased susceptibility of lung transplant recipients is multifactorial including exposure of the graft to the external environment, impaired mucociliary clearance, and high levels of immunosuppression. Long-term outcomes in lung transplant recipients remain poor compared with other solid organ transplants largely due to deaths from infections and chronic allograft dysfunction. Antibacterial, antifungal, and antiviral prophylaxis may be used after lung transplantation to target a number of different opportunistic infections for varying durations of time. The first-month posttransplant is most commonly characterized by nosocomial infections and donor-derived infections. Following the first month to the first 6 months after transplant-a period of intense immunosuppression-is associated with opportunistic infections. While immunosuppression is reduced after the first year posttransplant, infection remains a risk with community-acquired and rarer infectious agents. Clinicians should be vigilant for infection at all time points after transplant. The use of patient-tailored prophylaxis and treatments help ensure graft and patient survival.

A clinical and canine experimental study in small-airway response to bronchial thermoplasty: Role of the neuronal effect

BACKGROUND

The effects of bronchial thermoplasty (BT) on smooth muscle (SM) and nerves in small airways are unclear.

METHODS

We recruited 15 patients with severe refractory asthma, who received BT treatment. Endobronchial optical-coherence tomography (EB-OCT) was performed at baseline, 3 weeks' follow-up and 2 years' follow-up to evaluate the effect of BT on airway structure. In addition, we divided 12 healthy beagles into a sham group and a BT group, the latter receiving BT on large airways (inner diameter >3 mm) of the lower lobe. The dogs' lung lobes were resected to evaluate histological and neuronal changes of the treated large airways and untreated small airways 12 weeks after BT.

RESULTS

Patients receiving BT treatment had significant improvement in Asthma Control Questionnaire (ACQ) scores and significant reduction in asthma exacerbations. EB-OCT results demonstrated a notable increase in inner-airway area (Ai) and decrease in airway wall area percentage (Aw%) in both large (3rd-to 6th-generation) and small (7th-to 9th-generation) airways. Furthermore, the animal study showed a significant reduction in the amount of SM in BT-treated large airways but not in untreated small airways. Protein gene product 9.5 (PGP9.5)-positive nerves and muscarinic receptor 3 (M3 receptor) expression in large and small airways were both markedly decreased throughout the airway wall 12 weeks after BT treatment.

CONCLUSIONS

BT significantly reduced nerves, but not SM, in small airways, which might shed light on the mechanism of lung denervation by BT.

Influence of intrathoracic vagotomy on the cough reflex in the anesthetized cat

Recurrent laryngeal afferent fibers are primarily responsible for cough in response to mechanical or chemical stimulation of the upper trachea and larynx in the guinea pig. Lower airway slowly adapting receptors have been proposed to have a permissive effect on the cough reflex. We hypothesized that vagotomy below the recurrent laryngeal nerve branch would depress mechanically or chemically induced cough. In anesthetized, bilaterally thoracotomized, artificially ventilated cats, thoracic vagotomy nearly eliminated cough induced by mechanical stimulation of the intrathoracic airway, significantly depressed mechanically stimulated laryngeal cough, and eliminated capsaicin-induced cough. These results support an important role of lower airway sensory feedback in the production of tracheobronchial and laryngeal cough in the cat. Further, at least some of this feedback is due to excitation from pulmonary volume-sensitive sensory receptors.

Fundoplication after lung transplantation in patients with systemic sclerosis-related end-stage lung disease

INTRODUCTION

Gastroesophageal reflux and aspiration are risk factors for chronic lung allograft dysfunction in lung transplant recipients. Patients with systemic sclerosis are at an increased risk of aspiration due to esophageal dysmotility and an ineffective lower esophageal sphincter. The aim of this study is to understand the effect of fundoplication on outcomes in systemic sclerosis recipients.

METHODS

Between 2001 and 2019, 168 systemic sclerosis patients were referred for lung transplantation-51 (30.3%) were listed and 36 (21.4%) were transplanted. Recipients were stratified whether they underwent a fundoplication (n = 10, 27.8%) or not (n = 26, 72.2%). Freedom from chronic lung allograft dysfunction and survival were analyzed using log-rank test. Multivariable analysis for known risk factors was performed using a Cox-proportional hazards model.

RESULTS

Median time to fundoplication after transplantation was 16.4 months (interquartile range: 9.6-25.1) and all were laparoscopic (Dor 50%, Nissen 40%, Toupet 10%). There were no differences in acute rejection ⩾ A1 (26.9% vs 30%), or primary graft dysfunction grades 2-3 at 72 h (42.3% vs 40%) between groups. Recipients with fundoplication had an increased freedom from chronic lung allograft dysfunction (p = 0.035) and overall survival (p = 0.01). Fundoplication was associated with a reduced risk of mortality adjusting for other comorbidities (hazard ratio = 0.13; 95% confidence interval = 0.02-0.65; p = 0.014). Double and single lung transplant did not have different post-transplant survival.

CONCLUSION

Fundoplication in systemic sclerosis lung transplant recipients is associated with greater freedom from chronic lung allograft dysfunction and overall survival. Screening for reflux and aspiration followed by early fundoplication may delay graft deterioration in this population.

Community-Acquired Respiratory Viruses Post-Lung Transplant

Survival in lung transplant recipients (LTRs) lags behind heart, liver, and kidney transplant, in part due to the direct and indirect effects of infection. LTRs have increased susceptibility to infection due to the combination of a graft continually exposed to the outside world, multiple mechanisms for impaired mucus clearance, and immunosuppression. Community-acquired respiratory viral infections (CARVs) are common in LTRs. Picornaviruses have roughly 40% cumulative incidence followed by respiratory syncytial virus and coronaviruses. Although single-center retrospective and prospective series implicate CARV in rejection and mortality, conclusive evidence for and well-defined mechanistic links to long-term outcome are lacking. Treatment of viral infections can be challenging except for influenza. Future studies are needed to develop better treatments and clarify the links between CARV and long-term outcomes.

Preoperative risk factors for successful extubation or not after lung transplantation

Background

The purpose of this study was to uncover preoperative risk factors for extubation failure or re-intubation for patients undergoing lung transplant (LTx).

Methods

We performed a retrospective case-control study of LTx from our center between January 2017 and March 2019. Demographic and preoperative characteristics were collected for all included patients. Univariable analysis and multivariable logistic regression were used to analyze risk factors of postoperative unsuccessful extubation following LTx.

Results

Among 107 patients undergoing first LTx investigated, 74 (69.16%) patients who were successfully liberated from mechanical ventilation (MV), and 33 (30.84%) patients who were unsuccessful extubation, which 18 (16.82%) patients suffered from reintubation. associated preoperative factors for unsuccessful extubation following LTx included preoperative extracorporeal membrane oxygenation (ECMO) support [OR =4.631, 95% confidence interval (CI): 1.403–15.286, P=0.012], the preoperative ability of independent expectoration (OR =4.517, 95% CI: 1.498–13.625, P=0.007), the age older than 65-year-old (OR =4.039, 95% CI: 1.154–14.139, P=0.029), and receiving the double lung and heart-LTx (OR =3.390, 95% CI: 0.873–13.162, P=0.078; and OR =16.579, 95% CI: 2.586–106.287, P=0.012, respectively). Further, we investigated the preoperative predicted factors for reintubation. Only the preoperative ECMO remained a significant predictor of re-intubation (OR =4.69, 95% CI: 1.56–15.286, P=0.012).

Conclusions

Preoperative independent sputum clearance, preoperative ECMO, older than 65-year-old, and double lung or heart-LTx were four independent risk factors for unsuccessful extubation. Moreover, preoperative ECMO was the only independent risk factor for reintubation.

500 Million Alveoli from 30,000 Feet: A Brief Primer on Lung Anatomy

The lungs are a complex organ that fulfill multiple life-sustaining roles including transfer of oxygen and carbon dioxide between the ambient environment and the bloodstream, host defense, and immune homeostasis. As in any biological system, an understanding of the underlying anatomy is prerequisite for successful experimental design and appropriate interpretation of data, regardless of the precise experimental model or procedure in use. This chapter provides an overview of human lung anatomy focused on the airways, the ultrastructure or parenchyma of the lung, the pulmonary vasculature, the innervation of the lungs, and the pulmonary lymphatic system. We will also discuss notable anatomic differences between mouse and human lungs.

Principles of Urgent Management of Acute Airway Obstruction

Recognizing and acting early on airway compromise reduces morbidity and mortality in patients with airway obstruction. Causes include foreign bodies, toxic/hot fumes, difficult intubation, laryngeal spasm, and tumors. Before definitive control of the airway is possible, provide 100% oxygen with a tightly fitting mask to optimize body oxygen stores. Pulse oximetry is a poor indicator of airway compromise; a decreasing arterial hemoglobin oxygen saturation is a late sign of impending hypoxemia. Basic airway maneuvers improve the patency of an obstructed airway. Getting help from an anesthetist early is a priority.

Could reflex cough induced through nebulized capsaicin achieve airway clearance in patients with acute retention of lung secretions?

Nasotracheal suctioning (NTS) is a procedure commonly performed by respiratory physiotherapists and nurses to remove excess respiratory secretions from the tracheobronchial tree in a self-ventilating, non-intubated and non-tracheotomized patient. NTS is an important treatment modality for patients with acute secretion retention who are at high risk of progressive respiratory deterioration and arrest. However, NTS is a blind invasive procedure with risk of serious adverse events, and the patient experience of NTS is often extremely negative. Capsaicin, a substance extracted from cayenne pepper, elicits reflex coughs when inhaled. It is hypothesized that capsaicin-induced reflex cough may offer an alternative treatment option to NTS. It is suggested that repeated reflex cough bouts, elicited through inhalation of nebulized capsaicin via a facemask, could achieve clearance of retained secretions from the tracheobronchial tree to the oropharynx, thereby avoiding the need for NTS. This hypothesis is supported by preliminary cough flow data from a stroke trial. Stroke patients underwent assessments of peak cough flow (PCF, a measure of cough effectiveness) of both maximal volitional cough and capsaicin-induced reflex cough. In a sub-group of 20 stroke patients with weak volitional cough (mean PCF 220 L/min, SD 80), PCF of capsaicin-induced reflex cough was on average 184 L/min (SD 130) higher than PCF of subjects' maximal volitional cough effort. Cough flow traces indicate a pattern of cough augmentation during consecutive reflex cough bouts. It is suggested that the hypothesis may best be tested in a pragmatic applied clinical study, i.e. through the application of nebulized capsaicin in relevant clinical situations, as opposed to observational or experimental physiological studies.

Abdominal Complications After Lung Transplantation in a Brazilian Single Center

Surgical and nonsurgical abdominal complications have been described after lung transplantation. However, there is limited data on this event in this population. The objective of this study was to analyze the incidence of abdominal complications in patients undergoing lung transplantation at the Heart Institute of the Faculty of Medicine, University of São Paulo (InCor-HCFMUSP) between the years 2003 and 2016. The main causes of abdominal complications were inflammatory acute abdomen (7 patients; 14%), obstructive acute abdomen (9 patients; 18%), gastroparesis (4 patients; 8%), distal intestinal obstruction syndrome (4 patients; 8%), perforated acute abdomen (7 patients; 14%), cytomegalovirus (CMV; 6 patients; 12%), and other reasons (12 patients; 26%). Separating these patients according to Clavien-Dindo classification, we had 21 patients (43%) with complications grade II, 4 patients (8%) with complications grade IIIa, 7 patients (14%) with grade IIIb complications, 7 patients (14%) with grade IV complications, and 10 patients (21%) with grade complications V. In conclusion, abdominal disorders are seriously increased after lung transplantation and correlate with a high mortality. Early abdominal surgical complication has worse prognosis.

GORD symptoms in lung transplantation: how efficient is the reflux symptom index questionnaire compared to the esophageal impedance test?

OBJECTIVE

As Gastroesophageal reflux disease (GORD) affects long-term survival in lung transplant recipients, the aim of this observational prospective study was to analyze the efficacy of The Reflux Symptom Index Questionnaire (RSI) compared to the esophageal impedance test.

METHODS

Both esophageal impedance studies and RSI questionnaire were routinely performed in all patients who had completed rehabilitation following lung transplantation from June 2013 till March 2014. RSI generates a score of between zero and forty-five, taking into account any symptoms within four wk of the questionnaire. Our analysis considered RSI score cut-offs of 10 and 13 indicating significance of reflux.

RESULTS

Out of 84 patients, 50 (59.5%) had evidence of GORD detected by impedance studies, whereas only 33 (39.2%) and 22 (26.2%) had RSI >10 and 13, respectively. An elevated RSI was not found to be associated with positive impedance studies using a score of either 10 or 13 (p = 0.127 and p = 0.142, respectively); 32.1% (n = 27) and 40.5% (n = 34) were found to have negative RSI and positive impedance test using 10 or 13 as cut-off, respectively.

CONCLUSION

RSI Score is an unreliable predictor of GORD among lung transplant recipients. The authors therefore recommend the routine use of impedance testing in post-transplant patients.

The impact of abdominal complications on the outcome after thoracic transplantation--a single center experience

BACKGROUND

Abdominal complications after thoracic transplantation (Tx) are potentially associated with an increased risk of mortality. We recently reported about the severe outcome after bowel perforation in patients following lung transplantation (LuTx). The aim of the present study was to likewise identify the risk factors with an impact on patient survival following heart transplantation (HTx).

METHODS

A retrospective analysis for the frequency and outcome of abdominal interventions following HTx was performed in 342 patients, and these data thereafter compared to a re-evaluated pool of 1,074 patients following LuTx. All patients were transplanted at Hanover Medical School, Germany, between January 2000 and October 2011.

RESULTS

The incidence for abdominal surgery was comparable between patients following HTx (n = 33; 9.6 %) and LuTx (n = 90; 8.4 %). Elective operations were more frequently performed in patients after HTx (8.5 vs. 5.1 %). In contrast, the incidence of emergency interventions was higher after LuTx (5.3 %) than that following HTx (2.3 %). Herewith associated was the mortality observed in these transplant recipients (15.3 and 9.9 % for LuTx and HTx, respectively). Leading diagnosis for emergency surgery was bowel perforation (n = 18, regarding all cases). In 11 of these patients, perforation occurred within the first 6 months after Tx and eight of them died in the course of this complication (one patient after HTx and seven patients after LuTx).

CONCLUSIONS

Abdominal complications after HTx are less frequently than after LuTx but equally correlate with a high mortality rate. In finding or even reasonable suspicion of an acute abdomen after thoracic Tx, a broad practice for extended diagnostics and a low barrier for an early explorative laparotomy thus are recommended.

Targeting voltage gated sodium channels NaV1.7, Na V1.8, and Na V1.9 for treatment of pathological cough

Recent advances in our understanding of voltage-gated sodium channels (NaVs) lead to the rational hypothesis that drugs capable of selective blockade of NaV subtypes may be a safe and effective strategy for the treatment of unwanted cough. Among the nine NaV subtypes (NaV1.1-NaV1.9), the afferent nerves involved in initiating cough, in common with nociceptive neurons in the somatosensory system, express mainly NaV1.7, NaV1.8, and NaV1.9. Although knowledge about the effect of selectively blocking these channels on the cough reflex is limited, their biophysical properties indicate that each may contribute to the hypertussive and allotussive state that typifies subacute and chronic nonproductive cough.

Mechanisms of respiratory innervation during embryonic development

During embryogenesis, the development of the respiratory tract is closely associated with the formation of an extensive neuronal network. While the topic of respiratory innervation is not new, and similar articles were published previously, recent studies using animal models and genetic tools are breathing new life into the field. In this review, we focus on signaling mechanisms that underlie innervation of the embryonic respiratory tract.

Epidemiology, clinical characteristics and outcomes of extensively drug-resistant Acinetobacter baumannii infections among solid organ transplant recipients

BACKGROUND

Extensively drug-resistant Acinetobacter baumannii (XDR-Ab) has emerged as a major nosocomial pathogen, but optimal treatment regimens are unknown. Although solid organ transplant (SOT) recipients are particularly susceptible to XDR-Ab infections, studies in this population are limited. Our objectives were to determine the epidemiology, clinical characteristics and outcomes of XDR-Ab infections among SOT patients.

METHODS

A retrospective study of SOT recipients at our center who were colonized or infected with XDR-Ab between November 2006 and December 2011 was conducted. Among infected patients, the primary outcome was survival at 28 days. Secondary outcomes included survival at 90 days and clinical success at 28 days, and XDR-Ab infection recurrence.

RESULTS

XDR-Ab was isolated from 69 SOT patients, of whom 41% (28) and 59% (41) were colonized and infected, respectively. Infections were significantly more common among cardiothoracic than abdominal transplant recipients (p=0.0004). Ninety-eight percent (40/41) of patients had respiratory tract infections, most commonly ventilator-associated pneumonia (VAP; 88% [36/41]). Survival rates at 28 and 90 days were 54% (22/41) and 46% (19/41), respectively. Treatment with a colistin-carbapenem regimen was an independent predictor of 28-day survival (p=0.01; odds ratio=7.88 [95% CI: 1.60-38.76]). Clinical success at 28 days was achieved in 49% (18/37) of patients who received antimicrobial therapy, but 44% (8/18) of successes were associated with infection recurrence within 3 months. Colistin resistance emerged in 18% (2/11) and 100% (3/3) of patients treated with colistin-carbapenem and colistin-tigecycline, respectively (p=0.03).

CONCLUSIONS

XDR-Ab causes VAP and other respiratory infections following SOT that are associated with significant recurrence and mortality rates. Cardiothoracic transplant recipients are at greatest risk. Results from this retrospective study suggest that colistin-carbapenem combinations may result in improved clinical responses and survival compared to other regimens and may also limit the emergence of colistin resistance.

Staphylococcus aureus infections in the early period after lung transplantation: epidemiology, risk factors, and outcomes

BACKGROUND

Staphylococcus aureus infections among lung transplant recipients are poorly studied.

METHODS

We conducted a 5-year retrospective study of the epidemiology, clinical manifestations, risk factors, and outcomes of patients infected with S aureus within the first 90 days after lung transplantation.

RESULTS

An S aureus infection developed in 109 of 596 lung transplant (18%) recipients. Methicillin-susceptible S aureus (MSSA; 62%) was more common than methicillin-resistant S aureus (MRSA; 38%); however, the proportion of infections caused by MRSA increased over time. Pneumonia (48%) was the most common infection, followed by tracheobronchitis (26%), bacteremia (12%), intrathoracic infections (7%), and skin/soft tissue infections (7%). Risk factors included mechanical ventilation for > 5 days and isolation of S aureus from recipients' sterility cultures. Patients with MRSA cultured from the nares or respiratory tract at the time of transplant were at an increased risk for MRSA infection (p < 0.0001 and p = 0.02, respectively). Infected patients required longer hospital and intensive care unit stays (p < 0.0001 for both), but the 30- and 90-day mortality rates from the onset of infection were only 7% and 12%, respectively. However, infected patients had higher rates of acute and chronic rejection at 1 (p = 0.048) and 3 years (p = 0.002), and higher rates of mortality at 1 (p = 0.058) and 3 years (p = 0.009).

CONCLUSIONS

S aureus infections within the first 90 days of lung transplant were associated with low short-term mortality but increased long-term rates of mortality and acute and chronic rejection. Future studies are needed to explore the utility of S aureus eradication strategies in reducing disease burden and improving outcomes.