Ain-Shams Journal of Anaesthesiology

REVIEW ARTICLE
Year
: 2014  |  Volume : 7  |  Issue : 3  |  Page : 259--262

Perioperative pulmonary function assessment


Bahaa El-Din Ewees Hassan, Mai M Abdel-Aziz 
 Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of Medicine, Ain Shams University, Cairo, Egypt

Correspondence Address:
Mai M Abdel-Aziz
Department of Anesthesiology, Intensive Care, and Pain Management, Faculty of Medicine, Ain Shams University, Abbassiya Sq., Cairo 11566
Egypt

Abstract

The purpose of perioperative pulmonary assessment is to predict which patients are at increased risk for pulmonary complications. The postoperative pulmonary complications contribute significantly to overall morbidity and mortality rates. Atelectasis, hypoxemia, pneumonia, and respiratory failure are pulmonary complications that can follow surgical procedures.



How to cite this article:
Hassan BDE, Abdel-Aziz MM. Perioperative pulmonary function assessment.Ain-Shams J Anaesthesiol 2014;7:259-262


How to cite this URL:
Hassan BDE, Abdel-Aziz MM. Perioperative pulmonary function assessment. Ain-Shams J Anaesthesiol [serial online] 2014 [cited 2019 Jun 20 ];7:259-262
Available from: http://www.asja.eg.net/text.asp?2014/7/3/259/139536


Full Text

 Introduction



Preoperative pulmonary evaluation

The purpose of perioperative pulmonary assessment is to predict which patients are at increased risk for pulmonary complications. The postoperative pulmonary complications (PPCs) contribute significantly to overall morbidity and mortality rates. Atelectasis, hypoxemia, pneumonia, and respiratory failure are pulmonary complications that can follow surgical procedures. Such complications account for about 25% of deaths occurring within 6 days of surgery [1]. Other complications such as unexplained fever, excessive bronchial secretions, productive cough, abnormal breath sounds, atelectasis, and hypoxemia may be also included in the PPC. Therefore, the incidence of PPC varies markedly among the literature, ranging from 2 to 40% [2]. The most commonly utilized tools are chest radiography, arterial blood gas analysis, and pulmonary function tests (PFTs) [3].

Patients undergoing lung-resecting surgery

Patients undergoing lung-resecting surgery will invariably need to have pulmonary function testing preoperatively. There is a battery of tests that is necessary to perform to determine the anatomic resectability of the disease. These tests are, however, of more significant importance to the surgeon than to the anesthetist. The main goal of performing PFT is to decide whether the patient can withstand the planned procedure and survive the loss of the resected lung [4].

Stage I assessment of pulmonary function

Spirometry : It is dependent on patient effort. Forced expiratory volume in 1 s (FEV 1 ) is regarded as being the best for predicting complications of lung resection in the initial assessment, and it is the one most commonly used for decision making.

Diffusing capacity: Diffusing capacity of the lung for carbon monoxide (DL CO ) reflects alveolar membrane integrity and pulmonary capillary blood flow in the patient's lungs. However, later studies have not found it to be a significant predictor of postoperative complications [5,6].

Pulmonary function testing as a predictor of postoperative pulmonary complication: Previous studies on PFT in the preoperative evaluation for lung resection surgery indicate that the following criteria are predictive of increased PPC and mortality: for pneumonectomy, FEV 1 less than 2 l or less than 60% of predicted; maximum ventilatory volume (MVV) less than 55% of predicted; DL CO less than 50% of predicted; and FEF 25-75% less than 1.6 l/s; for lobectomy, FEV 1 less than 1 l; MVV less than 40% of predicted; FEF25-75% less than 0.6 l/s; and DL CO less than 50% of predicted; and for wedge resection, FEV 1 less than 0.6 l and DL CO less than 50% of predicted. If spirometry, lung volume, and DL CO values are within accepted limits, no further evaluation is needed. If FEV 1 values of more than 2 l or more than 60% of predicted, MVV values of more than 55% of predicted, and DL CO values of more than 60% of predicted are obtained, the patient is at low risk and can undergo pulmonary resection, including pneumonectomy, without further testing [4].

Stage II assessment of pulmonary function

If the above requirements are not met, the patient needs further evaluation. This extended assessment aims at determining individual lung function using quantitative ventilation-perfusion scan or differential lung scan. Using inhaled radioactive xenon ( 133 Xe) and intravenously injected radioactive technetium macroaggregates ( 99 Tc) taken up by the pulmonary circulation, each lung is measured for its contribution to the function of the total respiratory system, expressed as a percentage. From this measurement, the clinician can predict postoperative FEV 1 of the residual lung following surgery using the following formula: Predicted postoperative FEV 1 = Preoperative FEV 1 × % of radioactivity contributed by the nonoperated lung.

Stage III assessment of pulmonary function

Exercise testing stresses the entire cardiopulmonary and oxygen delivery system, assesses the adequacy of oxygen transport, and provides a good estimate of cardiopulmonary reserve. Cycle ergometry with incremental workloads measures VO 2 , VO 2 max , minute ventilation, and carbon dioxide output with concomitant monitoring of ECG, blood pressure, and oximetry while the patient exercises testing [7].

A schematic representation of a stepwise approach to preoperative evaluation before lung resection surgery is shown in [Figure 1] [8].{Figure 1}

Patients undergoing nonlung-resecting surgery

Preoperative pulmonary function testing is indicated in the selected groups of patients not undergoing lung volume-reducing surgery. In general, those undergoing major, but not lengthy, abdominal, orthopedic, head and neck, and neurological surgeries do not have to perform preoperative PFTs unless there is an added patient-related factor that may further put the patient at higher risk. [Table 1] provides the summary strength of the evidence for the association of patient, procedure, and laboratory factors with PPC [9] . If the patient complains of unexplained dyspnea, preoperative PFT provides a view about the impact of that symptom on the patient's respiratory capacity [10].{Table 1}

Spirometry

Spirometry is the accepted standard for diagnosing airway obstruction; spirometry shows a moderate to severe obstruction, and surgery can be delayed and a prophylactic program of pulmonary toilet, including smoking cessation, inhaled bronchodilators or steroid, and antibiotics for bronchitis may be indicated [11].

Spirometry is mandatory in patients who are heavy smokers. Spirometry, associated with blood gas analysis, is usually requested in patients with a history of chronic pulmonary diseases or complaining of inexplicable dyspnea or cough. If either the slow vital capacity or forced vital capacity is normal, it has been reported that patients with an FEV 1 value less than 1 l undergoing nonthoracic surgery are more likely to need postoperative ventilation; if with dyspnea at rest, their arterial partial pressure of oxygen PaO 2 is less than 70 mmHg; and if not dyspneic at rest, their P 1 O 2 is less than 45 mmHg [12].

Spirometry after bronchodilator

When combined with a bronchodilator trial, spirometry can differentiate between reversible and irreversible airway obstruction. The lack of an acute bronchodilator response does not prohibit a therapeutic trial of 6-8 weeks with bronchodilators and/or inhaled glucocorticoids with reassessment of clinical status and FEV 1 after that time [11].

Flow-volume loops

Flow-volume loops can identify upper airway obstruction. A limitation of flow (plateau) during forced inhalation suggests a variable extrathoracic obstruction, whereas limitation of flow during forced exhalation suggests variable intrathoracic obstruction. Fixed upper airway obstruction causes flow limitation during both forced inhalation and forced exhalation.

Static lung volumes

Body plethysmography is considered the gold standard for measurement of total lung capacity, particularly in the setting of airway obstruction, because it is minimally affected by misdistribution of ventilation as compared with gas dilution techniques.

Gas diffusion tests

The diffusion capacity is helpful in distinguishing between intrinsic lung disease in which DL CO is reduced and other causes of restriction, such as musculoskeletal deformities in which DL CO is normal. DL CO can also be used as a predictor of PPCs. Patients with a predicted DL CO less than 60% were found to have significant respiratory complications, hospitalizations, and increased mortality as compared with patients who had a higher DL CO (>60%) (12). Arterial blood gas analysis may be considered as a test for gas diffusion, and it can be used as an adjunct to pulmonary function testing in the preoperative evaluation.

Cardiopulmonary exercise testing

The American College of Chest Physicians recommends cardiopulmonary exercise testing in patients with FEV 1 or DL CO less than 40% of predicted to further determine their functional status and perioperative risk. The gold standard is exercise testing with progressive, incremental testing using a treadmill or cycle ergometry with cardiopulmonary monitoring. Nevertheless, the 6-min walk test also demonstrates an integrated exercise response involving the pulmonary and cardiovascular systems, systemic and pulmonary circulation, and neuromuscular function [13]. There are limitations of cardiopulmonary exercise testing. Its relevance as a stand-alone measure of efficacy is questionable; however, combining it with other tests increases its utility. Exercise testing in conjunction with ventilator-expired gas analysis has been shown to be a valuable diagnostic tool in patients with interstitial lung disease and pulmonary arterial hypertension. [Figure 2] shows an algorithm for preoperative evaluation of patients with unexplained chronic dyspnea [14].{Figure 2}

 Acknowledgements

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