Does the incremental shuttle walk test predict the development of a hospital acquired pneumonia in patients undergoing elective oesophagectomy: A service evaluation

Introduction

Oesophageal cancer is the 14th most common cancer in the U.K., accounting for 3% of all new cancer cases (Cancer Research U.K., 2020). Surgical resection via oesophagectomy remains the main stay of curative treatment, often in conjunction with neoadjuvant chemo/radiotherapy (Sjoquist et al., 2011; van Hagen et al., 2012). Despite advancements in surgical techniques and the implementation of enhanced recovery pathways, morbidity and mortality remains high in this cohort in comparison to other surgical populations (Takeuchi et al., 2014; Low et al., 2019). The national surgical quality improvement analysis identified patients undergoing an oesophagectomy having greater than five times the risk for developing pulmonary complications compared to those undergoing major abdominal surgery (Yang et al., 2015). Pulmonary complications, including hospital acquired pneumonia, are associated with longer hospital stays, increased cost of care, and substantial operative mortality (Shirinzadeh et al., 2011; Saeki et al., 2017).

The addition of preoperative neoadjuvant chemotherapy (NAC) has shown a 13% improvement in survival compared to surgery alone but side effects related to toxicity mean patients experience a reduction in cardiorespiratory reserve following treatment (Jack et al., 2014; Sinclair et al., 2016). As surgery places a significant metabolic demand on the body, those with a lower physiological reserve may be more susceptible to post-operative complications and higher rates of post-operative morbidity (Patel et al., 2019).

To improve clinical outcomes there is increasing focus on the assessment of patient’s fitness for surgery during the pre-operative pathway (Paul et al., 2014). Assessment of cardiopulmonary fitness can provide an individualised risk profile, helping to guide collaborative decision-making and inform the consent process but also dictate the level of post-operative care for example, high dependency unit/intensive care unit and provision of finite post-operative resources like physiotherapy. Whilst cardiopulmonary exercise testing is often seen as the gold standard for functional assessment, this is often time consuming and expensive, requiring specialist interpretation. Field tests to objectively measure functional capacity are therefore becoming of greater importance.

One such field test is the incremental shuttle walk test (ISWT) (Singh et al., 1992). An externally paced, maximal excursion test, the ISWT is a simple and easily reproducible test that is widely used within cardiac and pulmonary populations and shown to correlate well with VO2 max VO2 max on a cardiopulmonary exercise test (Pulz et al., 2008). Previous studies looking at the benefit of the ISWT in predicting post-operative outcomes within the oesophagastric population have demonstrated that walking less than 350 meters has been associated with significantly higher rates of mortality at 30 days (Murray et al., 2007) and 3 years (Whibley et al., 2018). The correlation between performance on ISWT and the development of hospital acquired pneumonia has not been previously investigated in this surgical population.

Objective

To assess whether walking <350 meters on an ISWT pre-operatively predicts the development of hospital acquired pneumonias following an elective oesophagectomy.

Method

Design

This was a single centre service evaluation conducted in a large tertiary level acute care hospital. This service evaluation was registered as an audit on the trusts clinical audit registration and management system (CARMS-14193).

Setting

The Queen Elizabeth Hospital Birmingham (QEHB) is part of the University Hospitals Birmingham NHS Foundation Trust (UHB) and a major tertiary upper gastrointestinal unit in Birmingham. Covering a population of 1.7 million, patients are referred both locally and from four district general hospitals (Walsall Manor Hospital, Sandwell and City Hospitals and Russells Hall Hospital Dudley). It performs approximately 80 oesophagectomys a year.

Participants

Consecutive patients with a diagnosis of oesophagogastric cancer listed for an elective oesophagectomy at a large U.K. tertiary hospital between December 2017 and February 2020 were included. Patients who were unable to complete an ISWT, deemed not fit for surgery or sustained a significant post-operative neurological event were excluded from the analysis.

Procedure

All patients were reviewed by a physiotherapist during their pre-assessment clinic one week prior to surgery to complete an incremental shuttle walk test (ISWT). The ISWT was completed according to a standardised protocol and involved patients walking around two cones set up 9 metres apart. Patients were asked to cover the distance between the cones in time to auditory cues. Oxygen levels and heart rate were recorded during the assessment with the use of a portable pulse oximeter. The test was stopped when patients could no longer keep pace with the auditory cues or were too breathless to continue. The total distance mobilised was recorded.

Post-operatively all patients received standard care as normally provided in our institution. This consists of an enhanced recovery program which includes daily reviews by a physiotherapist for the provision of respiratory care (for example, deep breathing exercises, secretion clearance techniques) and progression of mobility.

Outcomes

Primary outcome was the incidence of hospital acquired pneumonias as defined by U.S. centres for Disease Control (Jammer et al., 2015). The specific criterion used is presented in Figure 1. Secondary outcomes included re-intubation rates, ICU readmissions, ICU and hospital length of stay. We also recorded 30 and 90 day and 12 month mortality.

See Figure 1: U.S. Centres for Disease Control definition of pneumonia (Jammer et al., 2015).

Data collection

Data was collected prospectively throughout the evaluation period using patient noting and electronic databases. Baseline demographics included age, BMI, and charlson co-morbidity index (CCI). Patients were screened daily for the development of a HAP by the physiotherapist completing their daily treatment. ICU and hospital LOS and ICU re-admission data was obtained from electronic databases and mobility levels via patients notes.

Statistical analysis

Descriptive statistics were used to summarise the data; results are reported as medians and interquartile ranges or means and standard deviations, as appropriate. Categorical variables were summarised as counts and percentages. A non-parametric approach was employed, with data reported as medians and interquartile ranges (IQR), and comparisons between groups made using Mann–Whitney tests. For categorical variables, Fisher’s exact tests were used. Analysis was performed with IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp.

Results

138 patients were reviewed by the physiotherapist in pre assessment clinic during the observation period and completed a pre-operative ISWT. Of the 138 patients, 121 were included in the analysis. Patients were excluded because they were not deemed fit for surgery by the multidisciplinary team based on ISWT outcomes (n = 10), were inoperable (n = 6) or had a myocardial infarction during induction (n = 1) (See Figure 2 – flow diagram).

See Figure 2: Flow diagram.

Of the 121 patients included in the analysis, 96 (79%) mobilised ≥350 metres and 25 (21%) <350 metres. Those mobilising <350 metres were significantly older (70 v. 65 years, p 0.044) and had a trend towards higher CCI (see Table 1).

Table 1: Patient demographics.

*Data is reported as n (%), with p values from Fishers exact test or as median (interquartile range) with p values from Mann-Whitney tests. Bold p values are significant p <0.05. BMI = body mass index, MIO = minimally invasive oesophagectomy.

The incidence of hospital acquired pneumonias was significantly higher in individuals mobilising <350m (p 0.0003). Patients mobilising <350m also had a significantly longer ICU LOS (p 0.041). No significant difference in re-intubation rates, ICU re-admissions, hospital LOS and 30 and 90 day or 12 month mortality was observed between groups.

Table 2: Post-operative outcomes.

**Data is reported as n (%), with p values from Fishers exact test or as median (interquartile range) with p values from Mann-Whitney tests. Bold p values are significant p <0.05. HAP = hospital acquired pneumonia, ICU = intensive care unit, LOS = length of stay.

Discussion

This single centre service evaluation demonstrated the ISWT was an effective predictor for the development of HAP in patients undergoing oesophagectomy, with those patients walking <350 metres significantly more likely to develop a HAP and spend longer on ITU. There was also a trend towards patients walking <350 meters spending longer in hospital although this was not statistically significant. Patients mobilising less than 350 metres were significantly older, although no differences were observed with regards to comorbidities between groups. This is reflective of data published by other authors who also reported age as an independent risk factor for the development of post-operative pulmonary complications (PPCs) following oesophagectomy (Law et al., 2014) but would warrant further investigation to evaluate the impact of age and fragility on HAP. Age may therefore be utilised by clinicians as an indicator for triaging patients to pre-operative services for advanced medical investigations and assessments of functional capacity to determine fitness for surgery, as well guiding the level of post-operative care for example, HDU v. ICU.

Previous trials assessing the longer-term predictive value of the ISWT demonstrated significantly higher rates of mortality at both 30 days and 3 years post operatively in those walking <350 meters, with Murray et al. (2007) reporting a mortality rate of 63% at 30 days. Despite the significant difference in HAP rates in our study, we found no significant differences in mortality at either 30 or 90 days or at 12 months. Our mortality rate of 8% in the <350 meter cohort was considerably lower than that those in the study by Murray and colleagues (Murray et al., 2007). This may be reflective of the improvements in surgical screening and peri-operative care in the form of ERAS pathways over the past decade, resulting in more favourable outcomes for patients (Huang et al., 2020). Despite this, the 8% mortality in those walking <350 metres is still considerably higher than national 30 and 90 day mortality rates reported as 2.4% and 3.9% respectively (The Royal College of Surgeons of England et al., 2019) suggesting this still represents a higher risk population.

Our service evaluation has a number of notable limitations. Firstly, this is a single centre experience with small patient numbers and therefore may not be reflective of the entire oesophageal cancer population. Results were also open to bias as the physiotherapist assessing for HAPs was not blinded to ISWT outcomes. Additionally, time constraints in pre-assessment clinic meant patients only performed 1 ISWT. Previous studies have demonstrated a learning affect with this field test, recommending patients complete it twice to account for this. Therefore some of the patients who mobilised <350 meters may have improved their walking distance had the test been repeated.

Conclusion

This is a simple, low cost, easily reproducible risk stratification tool. Although no significant difference in mortality, patients walking less than 350 meters were more likely to get a HAP and spend longer on ITU. The ISWT may therefore help manage patient and clinician expectations, guide clinical decision making relating to post-operative care for example, HDU v. ICU and direct post-operative resources like physiotherapy to those most at risk of HAPs. If completed early enough in the patient pathway it may also highlight individuals who would benefit from prehabilitation in this high-risk cohort.

Key messages

• Patients undergoing oesophagectomy who walked <350 on the ISWT pre-operatively had significantly higher rates of post-operative hospital acquired pneumonia.

• Patients walking <350 meters also spent significantly longer on ICU.

• The ISWT may therefore help manage patient and clinician expectations, guide clinical decision making relating to post-operative care for example, intensive care v. high dependency unit and direct post-operative resources like physiotherapy to patients most at risk of HAPs.

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