ectomy

Description:

ectomy is an iPhone app developed by two physicians to simplify the risk assessment for resection surgery for lung cancer. The app uses preoperative FEV1 and DLCO values to compute predicted postoperative (PPO) values for FEV1 and DLCO and creates an editable report that can be printed or emailed directly from the iPhone.

Developers:

Peyman Pakzaban, MD

George Nassif, MD

Methodology:

The computations in this app are primarily based on the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (third edition) for evaluation of lung cancer patients before resectional surgery (Brunelli, Kim et al. 2013). These guidelines include consideration of both predicted postoperative FEV1 (PPO FEV1) and predicted postoperative DLCO (PPO DLCO) in assessing the risk for surgery and establish thresholds and diagnostic algorithms for risk stratification.

In this app, the user enters preoperative FEV1 (L, best post-bronchodilator value) and DLCO (ml/mmHg/min) as raw values and as percent predicted values. For calculation of PPO values after lobectomy, the guidelines recommend an anatomical method based on 19-segments lungs (RUL = 2, RML = 3, RLL = 5, LUL = 5, LLL = 4). The formulae for calculation of PPO FEV1 and PPO DLCO are:

PPO FEV1 = preoperative FEV1 x (1 – y/z)
PPO DLCO = preoperative DLCO x (1 – y/z)
where z = total number of unobstructed segments (default = 19) and y = number of segments to be resected.

For pneumonectomy, the guidelines recommend a quantitative radionucleotide perfusion scan to measure the fraction of total perfusion for the lung that is targeted for resection. The formulae for calculation of PPO FEV1 and PPO DLCO based on the quantitative perfusion method are:

PPO FEV1 = preoperative FEV1 x (1 – fraction of total perfusion for the resected lung)
PPO DLCO = preoperative DLCO x (1 – fraction of total perfusion for the resected lung).

Importantly, this app does not compute percent predicted values from raw values. The user should provide percent predicted values for FEV1 and DLCO from the preoperative pulmonary function tests in order for the app to calculate the PPO values as percent predicted values. Computation of percent predicted values from raw values requires consideration factors including age, sex, height and ethnicity and data models with reference values for various populations. The most commonly recommended data models are those derived from the third National Health and Nutrition Examination Survey (NHANES III) (Hankinson, et al. 1999), applicable to the US population, and the more recent European Respiratory Society Global Lung Function Initiative (ERS-GLFI or GLI) (Quanjer, Stanojevic et al. 2012, Quanjer, Stanojevic et al. 2013). Several online calculators have been developed based on these data models to convert raw values to percent predicted values and provide other useful metrics such as the lower limits of normal for spirometric indices. Links to these calculators are provided in the ‘Links’ Section of this app and below.

References:

Brunelli, A., et al. (2013). "Physiologic evaluation of the patient with lung cancer being considered for resectional surgery: Diagnosis and management of lung cancer, 3rd ed: American College of Chest Physicians evidence-based clinical practice guidelines." Chest 143(5 Suppl): e166S-e190S.

Hankinson, J. L., et al. (1999). "Spirometric reference values from a sample of the general U.S. population." Am J Respir Crit Care Med 159(1): 179-187.

Quanjer, P. H., et al. (2012). "Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations." Eur Respir J 40(6): 1324-1343.

Quanjer, P. H., et al. (2013). "Online Supplement - Multi-ethnic reference values for spirometry for the 3-95-yr age range: the global lung function 2012 equations." Eur Respir J 40(6): 1324-1343.

Links to online spirometry and DLCO calculators:

CDC-NIOSH Spirometry Calculator
https://www.cdc.gov/niosh/topics/spirometry/refcalculator.html

GLI Spirometry Calculator
http://gligastransfer.org.au/calcs/spiro.html

GLI DLCO Calculator
http://gligastransfer.org.au/calcs/tlco.html

Instructions for use of the app:

1. Enter preoperative FEV1 and/or DLCO obtained from recent pulmonary function
tests. You may enter them as raw values or percent predicted values or both.

2. Decide on the anatomical method, quantitative perfusion method, or both. Consider
using the former for lobectomy and the latter for pneumonectomy (see Methodology and
References).

3. Anatomical method: Select the lobes to be resected. Notice the changing count in the
'segments to resect' field. You can also edit the counts in the 'segments to resect' and
'total segments' fields directly. The default value for 'total segments' is set to 19.

4. Quantitative perfusion method: Enter a value for the percentage of the total lung
perfusion to be resected.

5. Tap the 'calculate' button.

6. Check the results in the gray output field. Notice that if you did not enter a particular
value in step 1, the corresponding value in the output field will appear as '--'. If satisfied
with the results, tap the 'add to report' button. If not, tap the reset button in the upper
right corner to start over.

7. Accept the disclaimer pop-up to get to the report field.

8. The report field is fully editable. You can type in patient information and comments
or delete portions of the report.

9. Print the report: Tap the printer icon on the report screen. You will be taken to the
'Printer Options' screen where you can use the iOS built-in functionality to AirPrint.

10. Email and share the report: Proceed as in step 9 to get to the 'Printer Options' screen.
Perform a two-finger spread (unpinch) gesture on the preview field. Then tap the share
icon on the upper right corner to access the iOS built-in functionality to email, text, or
save the report as a PDF file. Beware of the HIPAA implications of electronic
transmission of unencrypted patient identifying data and make sure to read the
Disclaimer.

Download instructions as PDF file

Screen shots:

pakzaban@icloud.com

gmnassif@yahoo.com