chumillas 1995

Prevention of Postoperative Pulmonary Complications Through Respiratory Rehabilitation: A Controlled Study Soledad Chumillas, MD, Jos~ L. Ponce, AID, Fernando Delgado, MD, Vicente Viciano, AID, Miguel Mateu, PT

ABSTRACT. Chumillas S, Ponce JL, Delgado F, Viciano V, Mateu M. Prevention of postoperative pulmonary complications through respiratory rehabilitation; a controlled clinical study. Arch Phys Med Rehabil 1998;79:5-9.

Objective: To investigate the efficacy of respiratory rehabilitation in preventing postoperative pulmonary complications (PPC) and to define which patients can benefit.

Design: A randomized clinical trial. Setting: A public hospital. Patients: Eighty-one patients who had upper abdominal sur-

gery were distributed into two homogeneous groups: control (n = 41) and rehabilitation (n = 40).

Intervention: Breathing exercises in the rehabilitation group. Main Outcome Measures: Preoperative and postoperative

clinical evaluation, spirometry, arterial gasometry, and simple chest X-rays.

Results: The incidence of PPC was 7.5% in the rehabilitation group and 19.5% in the control group; the control group also had more radiologic alterations (p = .01). Stratified PPC analysis did not reveal significant differences between groups. However, high- and moderate-risk patients in the rehabilitation group had fewer PPC. Multivariate analysis showed a greater PPC risk associated with pulmonary history (p = .02) and duration of surgery longer than 120rain (p = .03), while rehabilitation ex- erted a protective effect (p = .06). Significant postoperative decreases in pulmonary volumes and arterial gas values were recorded in both groups, without significant differences.

Conclusions: Respiratory rehabilitation protects against PPC and is more effective in moderate- and high-risk patients, but does not affect surgery-induced functional alterations.

© 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabili- tation

p ULMONARY FUNCTION is commonly altered after surgery, 1 particularly in patients who have had chest or upper

abdominal surgery. The physiological changes observed are di- rectly related to anesthesia (general or regional) and to the type of incision and surgical technique employed, and are reflected by decreases in total pulmonary capacity and pulmonary volumes and by a parallel decrease in Pa02.2-4

From the Departments of Rehabilitation (Dr. Chumillas) and Surgery (Dr. Viciano), Lluls Alcanyfs Hospital, Xhtiva, Valencia; Departments of Surgery (Dr. Delgado) and Rehabilitation (Mr. Mateu), Dr. Peset Hospital, Valencia; and De- partment of Surgery (Dr. Ponce), Valencia University Medical School, Spain.

Submitted for publication October I0, 1996. Accepted in revised from February 13, 1997.

No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated.

Reprint requests to Dr. Maria Soledad Chumillas Luj~in, Servicio de Rehabilita- cidn, Hospital Lluls Alcanyis, Carretera Xb.tiva-Silla, Kin. 2, 46800-Xativa, Spain.

© 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

0003 9993/98/7901-423053.00/0

Clinical

These functional alterations are in turn implicated in the development of postoperative pulmonary complications (PPC), which are among the foremost causes of morbidity and mortality among surgical patients. 4'5 The reported frequency of PPC is highly variable, 6-9 ranging from 6% to 76% according to how complications and the methods used to evaluate them have been defined, and how the studies were controlled.

Breathing exercises have commonly been used to increase pulmonary volume and improve gas exchange and ventilation distributionJ ° Diaphragmatic, segmental, and costal respiratory exercises, as well as sustained maximal inspiration, may allevi- ate surgically induced alterations such as diminished diaphragmatic mobility and restrictive pulmonary changes.m'l~

Most studies on the effects of respiratory rehabilitation have had methodological defects that weaken their conclusions. Re- sults from studies done after the Conferences of the National Heart and Lung Institute in 1974 and 1979, however, suggest that respiratory rehabilitation, physical therapy, and mechanical devices may exert a beneficial effect on the postoperative course of patients who have had chest and abdominal surgery by restor- ing the normal ventilation pattern. ~ Nevertheless, controversy remains over the efficacy of respiratory rehabilitation in dimin- ishing the incidence of PPC and over the identification of those patients who might truly benefit from respiratory rehabilitation, ie, all patients or only high-risk cases.

This study investigated whether preoperative and postoperative respiratory rehabilitation improves lung function and dimin- ishes the incidence of PPC after supraumbilical laparotomy, and whether such benefit is experienced by all patients or only by high-risk patients.

MATERIALS AND METHODS

A randomized clinical trial considered 115 consecutive patients older than 15 years of age who had elective supraumbilical laparotomy in a department of general and digestive surgery. Supraumbilical laparotomy had been performed in all cases, regardless of the type of incision employed. All patients gave informed verbal consent to take part in the study.

Thirty-four patients were excluded from the study, 64.5% because of surgery-related reasons (need for emergency operation, extrapulmonary postoperative complications, infraumbili- cal extension of the laparotomy) and 35.5% as a result of incom- plete protocols atta-ibutable to patient-related causes (lack of cooperation).

The 81 patients who could be evaluated (46 women and 35 men with a mean age of 64.1 years [range, 18-84]) were distributed into two homogeneous groups, a control group (n = 41) and a respiratory rehabilitation group (n = 40).

Standard balanced anesthesia was used in all cases, consisting of sodium thiopental, atracurium, fentanyl, and isoflurane. The doses were varied only according to patient weight and duration of surgery.

To minimize negative effects on pulmonary function caused

Arch Phys Med RehabU Vol 79, January 1998

6 POSTOPERATIVE RESPIRATORY REHABILITATION, Chumillas

Table 1: Pulmonary Risk Score

Parameters Score

Spirometry* FVC <50% 1 FEV1/FVC

65% to 75% 1 50% to 65% 2 <50% 3

Age ->65 yrs 1 BMI >25% 1 Abdominal surgery, supraumbilical 2 Pulmonary history*

Antecedents 1 Cough and expectoration I Smoker 1

* Cumulative score: Spirometry, 0-4; pulmonary history, 0-3.

by postoperative pain from the surgical wound, all patients received the same postoperative analgesic regimen, chosen for its negligible repercussion on respiration: 2g magnesium methami- zole diluted in 100mL physiological saline administered intrave- nously every 8 hours. Oral dosing was substituted in the following days, or on restoration of bowel transit.

Patient Classification Since up to 80% of all patients who will subsequently have

complications can be identified using clinical history, physical examination, and spirometry, 7 the parameters considered for evaluating pulmonary risk were age, supraumbilical surgery, pulmonary antecedents, the presence of pulmonary symptoms, tobacco smoking, body mass index (BMI) as an objective crite- rion of obesity ~2 and calculated as body weight (kg) divided by size (m2), and spirometry. As a function of a score 7J3 (table 1), the patients were distributed into risk groups (low, 0-3; moderate, 4-6; high, ->7) and randomly assigned either to the study group, which received preoperative and postoperative respiratory rehabilitation, or to the control group, which did not receive respiratory rehabilitation. Nevertheless, most of the patients (91.4%) belonged to moderate- or low-risk subgroups.

The patients had physical examination, spirometry, arterial gasometry, and simple chest X-rays using the habitual antero- posterior and lateral projections. These evaluations were made preoperatively and after surgery on days 2, 4, and 6, with the exception of gasometry, which was performed only on post- surgery days 2 and 4.

The spirometric results were obtained using a portable auto- matic spirometer," with the patient seated and following the norms of the Spanish Society for Pathology of the Respiratory Apparatus. I6 The best of at least three valid spirometric maneuvers was selected. Forced vital capacity (FVC) and forced expi- ratory volume in 1 second (FEV~, measured in milliliters and as a percentage of the reference value) were calculated, as well as the ratio FEVI/FVC.

Arterial gases were analyzed after extracting an arterial blood sample by radial artery puncture. The specimen was immedi- ately processed in the central laboratory of the hospital with an IL 1306 gas autoanalyzer, b Arterial oxygen partial pressure (Pao2), arterial oxygen saturation (Sao2), and arterial carbon dioxide partial pressure (Paco2) were recorded.

The simple chest X-rays were taken in the Department of Radiodiagnostics, where a report was issued of the results obtained, with no further clinical data. The radiological alterations were defined as segmental or subsegmental atelectasis, with infiltration or consolidation, according to the criteria of the radiologist.

The postoperative clinical pulmonary complications were defined according to clinical (symptoms and physical examination) plus radiological criteria as bronchitis, atelectasis, and

pneumonia (table 2). When there were only radiological alterations without clinical symptoms or alterations in auscultation, the complications were considered as subclinical.

Other study variables of interest were patient age, sex, and duration of surgery (shorter or longer than 120min).

Respiratory Rehabilitation Protocol The 40 patients assigned to the study group were subjected

to a previously designed respiratory rehabilitation protocol comprising patient awareness, adequate instruction about the forced expiration technique ~° and cough mechanism, chest expansion exercises and diaphragmatic mobilization, maximal inspiration sustained for 3 to 5sec, and early ambulation after surgery. From 2 to 3 days before the operation until discharge (by day 7 after surgery, on average), the exercises were performed for 10 to 15rain, four times daily. During the first 2 postoperative days the exercise sessions were more frequent: 10rain every 2 hours. A physiatrist and a physical therapist instructed the patients on the different exercises and monitored correct exercise performance on a daily basis.

Statistical Analysis The analysis of the incidence of PPC according to whether

or not respiratory rehabilitation had been provided was carried out by the X 2 test, with a stratified analysis by risk factors. The possible association between the degrees of risk and PPC, as well as the effect of respiratory rehabilitation in the different risk subgroups, was investigated by stratified analysis and the X 2 test. A multivariate analysis was also performed based on the nonconditional logistic regression method, comprising those variables regarded as most relevantJ 5

The effect of respiratory rehabilitation on the decrease in postoperative lung function was analyzed in terms of the differences in spirometric and gasometric mean _+ 95% confidence intervals (95%CI) between the preoperative and postoperative values recorded in each group, using the Student t test for paired samples. The Student t test for nonpaired samples was in turn employed for comparisons between groups. 15

RESULTS

No significant differences were observed in the sample char- acteristics or in the risk factors of both groups, with the exception of sex distribution. Likewise, no differences were recorded in the average duration of surgery, in the types of incision performed in each group, or in the chest X-ray alterations observed preoperatively.

Postoperative Pulmonary Complications The global incidence of complications (table 3) in the series

was 13.6%. The three complications recorded in the respiratory

Table 2: Definition of PPC

Bronchitis Chest X-ray negative Temperature of <37.5°C Auscultation: rales Sputum abundant and clear

Atelectasis Chest X-ray: collapse, diaphragmatic elevation Temperature of <38°C Auscultation: diminished or abolished vesicular murmur

Pneumonia Chest X-ray: consolidation, pleuresy Temperature of >38°C (->4 days) Auscultation: rales Sputum abundant and purulent

Arch Phys Med Rehabil Vol 79, January 1998

POSTOPERATIVE RESPIRATORY REHABILITATION, Chumillas 7

Table 3: Clinical PPC and Radiological Alterations by Groups

Control Rehabilitation Odds (n - 41) (n = 40) Total Ratio P

Pulmonary clinical complications 8 (19.5%) 3 (7.6%) 11 (13.6%) .33 .11

Radiological alterations 16 (39%) 6 (15%) 22 (27.5%) .28 .017

rehabilitation group (7.5%) corresponded to two cases of bronchitis, and atelectasis in one patient. In turn, the 8 PPC (19.5%) observed in the control group corresponded to bronchitis (1 case), atelectasis (6 cases), and pneumonia (1 case). Although the incidence of complications was greater in the controls, there were no statistically significant intergroup differences (p = . 11 ).

The postoperative X-rays (table 3) revealed alterations in 27.5% of cases, with a higher incidence in the control group (p = .017). More than 50% of the pathological images, however, were of no clinical significance. The control group showed subsegmental atelectasis in 13 cases and segmental atelectasis in 3 cases (one with consolidation). The rehabilitation group showed subsegmental atelectasis in 5 cases and segmental atelectasis in 1 patient.

The univariate analysis of several risk factors, in the 81 patients, found no increased incidence of complications, except when the duration of surgery exceeded 120min; the incidence of PPC was 21.4%, versus only 5.1% for surgical times of less than 120min. Thus, only surgery lasting longer than 120min was found to be a determinant factor for increased complications (p = .03). On analyzing PPC by stratifying the control and rehabilitation groups according to the different risk factors investigated, however, no significant differences were observed between the two groups of subjects. The risk of PPC implied by the duration of surgery was not influenced by having or not having received respiratory rehabilitation.

The analysis of the risk subgroups found that increased risk was significantly (p = .044) linked to a greater number of PPC. On studying the complications in the control group versus the rehabilitation group stratified by risk degree (table 4), however, although decreases in PPC of 17% and 15% were observed, respectively, in the high-risk and moderate-risk rehabilitation subgroups, the summarizing X 2 test showed no significant differences between the groups.

In the case of the multivariate analysis, we employed a retro- grade approach based on a saturated model comprising six variables. PPC was taken as dependent variable, while the indepen- dent variables were sex, tobacco consumption, pulmonary antecedents, duration of surgery, and respiratory rehabilitation. The best explanatory model contained the variables of pulmonary antecedents, duration of surgery, and respiratory rehabilitation. The rest of the variables lacked explanatory value. Thus, the risk of PPC in patients with antecedent pulmonary pathology (p = .025) or whose surgery lasted longer than 120min (p = .036) was significantly greater than the risk in relation to the remaining variables. On the other hand, preoperative and postoperative respiratory rehabilitation diminished the risk of developing PPC; the corresponding odds ratio (OR) was close to statistical significance (p = .061, 95%CI = .04 to 1.09).

Postoperative Spirometric Alterations Both groups showed a sudden decrease in FVC and FEV~

from values recorded before surgery, the lowest values being recorded 48 hours after surgery. This was followed by a gradual recovery over the next few days, although preoperative values still had not been reached 6 days after surgery. A large significant difference (p = .0000) was established between the preoperative and three postoperative FVC and FEV~ determinations,

both in the controls and in the respiratory rehabilitation group, but not in the different determinations between groups. The FEV1/FVC ratio underwent no significant postoperative variations.

To quantify the importance of the postoperative decrease in FVC and FEVj values, the percentages of the decreases with respect to their corresponding preoperative values (regarded as basal) were analyzed. Thus, 48 hours after surgery FVC had decreased to 55% of its preoperative value, and FEV~ had decreased to 51%. These parameters gradually recovered to 76% and 72%, respectively, by day 6. This postoperative variation was similar in both groups, with no significant differences.

Postoperative Gasometric Alterations Diminished Sao2 values (although within the normal range)

and hypoxemia were recorded postoperatively. These decreases were maximal by day 2, and a gradual increase was observed over the following days. There were no significant variations in PacQ. In both the control and respiratory rehabilitation groups, a statistically significant difference was observed between the preoperative and two postoperative determinations of Pao2 and Sao2 (p < .05), although no significant differences were recorded between the two groups.

Taking the preoperative mean as basal value, we found that surgery caused a decrease in Pao2 after 48 hours to 87.8% of the presurgical values. This parameter recovered over the subsequent days. The decreases observed were similar in both groups, with no significant differences.

DISCUSSION

Studies on the efficacy of the different forms of pulmonary physical therapy in preventing PPC are not conclusive, because variability exists in the rehabilitation techniques employed, the definitions used, and in the incidence of PPC. 9'f ~.~62f

Studies have reported a high incidence of PPC, based on the interpretation of chest X-rays and regarding as complications those radiological alterations lacking clinical significance. In agreement with Schwieger, t7 we have observed a greater incidence of radiological alterations, half of which tend to improve spontaneously. ~'-18'22 This cannot be attributed to bias on the part of the radiologist, who in no case was informed of patient condition.

We consider that the low incidence of PPC in our series (13.6%) (ie, in the lower range reported in the literature) 6-9 may be due to several reasons: (1) general prophylactic measures (eg, early ambulation and postoperative analgesia) were routine in the management of surgical patients; (2) there have been important technical developments in anesthesia in recent years23; and (3) most patients (91.4%) were moderate- or low- risk cases.

The risk factors frequently related to PPC were smoking, the presence of preoperative or coexistent pulmonary pathology, obesity, and the duration of surgery. 4'24 In our series, multivariate analysis suggests that both surgical times longer than 120min and antecedent puhnonary pathology significantly increase the risk of PPC. Because of sample size limitations, however, univariate analysis only demonstrated a significant

Table 4: PPC by Risk and Group

Control Rehabilitation Degree of Risk (PPC/n) (PPC/n) Total (PPC/n) p

High (>7) 2/4 (50%) 1/3 (33.3%) 3/7 (42.9%) 1.0 Moderate (4-6) 5/25 (20%) 1/20 (5%) 6/45 (13.3%) 0.20 Low (0-3) 1/12 (8.3%) 1/17 (5.9%) 2/29 (6,9%) 1.0


8 POSTOPERATIVE RESPIRATORY REHABILITATION, Chumillas

increase in risk in relation to surgical times longer than 120min. This coincides with the observations of Hall and colleagues, 25 and supports the idea that the development of complications is to a large degree dependent on the type of surgery performed, since longer and more complex operations entail greater visceral manipulation, which in turn causes a greater inhibition of the diaphragmY

Nevertheless, when PPC were analyzed on patients classified into risk subgroups, risk was effectively found to be in direct proportion to the appearance of postoperative complications.

Respiratory Rehabilitation

Although there have been few controlled studies, Celli and colleagues 16 and Roukema and associates 26 found a statistically significant, 50% decrease in complications among patients per- forming breathing exercises or with mechanical aids, ie, incentive spirometer or intermittent positive pressure breathing, and Morran and associates 2° recorded a significant decrease in the incidence of postoperative pneumonia in patients who performed breathing exercises. Schwieger et al, ~7 using incentive spirometer, obtained a 10% decrease in the number of complications, though without reaching statistical significance. We used breathing exercises that have been reported to increase diaphragm mobility 23~27-29 and decrease basal atelectasis. The results failed to yield significant differences in PPC reduction between groups. However, the 12% decrease observed in the incidence of PPC in the rehabilitation group versus the control group, and the odds ratio close to statistical significance (revealed by the multivariate analysis), suggest the existence of a protective and beneficial effect on the part of respiratory rehabilitation in relation to the appearance of PPC.

As has also been reported by other authors, ~6't7 respiratory rehabilitation was found to significantly diminish postoperative radiological alterations.

A deduction common to all of the above-mentioned studies is that some form of rehabilitation seems better than none, even though the complete elimination of PPC may not prove possible. According to Celli, 23 all of the respiratory rehabilitation methods appear to be effective, although no general agreement exists over which is best or what the optimal treatment schedule may be. The method of choice is therefore dependent on the available resources.

On investigating the effect of respiratory rehabilitation in the different risk subgroups, however, a nonsignificant 15% to 17% decrease was observed in the incidence of complications among the high- and moderate-risk subgroups. The PPC percentages were similar in the low-risk subgroups. These observations agree those of Zibrak and colleagues, 8 who recommended avoiding the indiscriminate use of respiratory therapy, reserving it for the high- and moderate-risk groups, who stand to derive most benefit. As a result, related and unwarranted costs could be curbed.

Functional Alterations Altered pulmonary volumes and arterial gases caused by up-

per abdominal surgery have been confirmed by several authors) -63° Parfrey et al 3° and Latimer and colleagues 6 reported that FVC decreased, respectively, to 27% and 35% of preoperative values in the first 24 hours. According to other authors, 3'3~ postoperative hypoxemia is maximal on the day of the operation. In our study, the first postoperative recording was made after 48 hours; consequently, the decreases in pulmonary volumes and PaQ in our series were less.

Most studies ~7'19'~1'32 that have evaluated the ability of respiratory rehabilitation to minimize postoperative changes in pulmonary volumes, including our own, have reported no relevant

differences between controls and treated patients, or between groups subjected to different therapeutic regimens.

As regards the effect of respiratory rehabilitation on postoperative arterial gas alterations, several studies 17'19'2°'21'32 failed to find differences in arterial gas variations between treated and nontreated groups. These observations agree with our own results. Only isolated studies such as that by Bartlett et al, 33 based on incentive spirometer, have reported slight improvement in oxygenation among treated patients.

We are of the opinion that the lack of significant intergroup differences may be explained by the difficulty involved in re- cruiting high-risk patients 7 while preserving sample homogene- ity, the possibility that pulmonary function testing may not be sufficiently sensitive to identify the functional changes induced by rehabilitation, 5'3~ and the low incidence of PPC in our series.

C O N C L U S I O N S

Surgical times in excess of 120rain, a history of pulmonary pathology, and belonging to moderate- or high-risk subgroups are all factors that increase the possibility of developing PPC. Surgery induces significant decreases in pulmonary volumes and arterial gas levels that are not minimized by respiratory rehabilitation. Nevertheless, respiratory rehabilitation allows a decrease in the postoperative radiological alterations and exerts a protective effect against PPC. Finally, respiratory rehabilitation is more effective in moderate- and high-risk cases and should thus be recommended in such patients.

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Suppliers a. Autospiro AS-300; Minato Medical Science Co. Ltd., Osaka, Japan. b. Instrumentation Laboratory, Milan, Italy.


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