Abstract
BACKGROUND: Incentive spirometers were developed to facilitate sustained maximum inspiration. In addition to a slow-rising float that indicates volume displacement, the incentive spirometers includes a sensitive, rapid-fluttering flow indicator. Achieving the target inspiratory volume is believed to be the most important factor in successful incentive spirometers use. This investigation hypothesized that patients focus on the rapid fluttering of the flow indicator rather than volume float during incentive spirometers use. The effects of adjusting hand positioning to cover the flow indicator on inspiratory volumes were evaluated.
METHODS: A randomized, prospective, counter-balanced crossover analysis of postoperative subjects was completed. In alternating assignment, the subjects were randomized to 1 of 2 study groups: (A) with the flow indicator covered first followed by the flow indicator standard exposed, and (B) with the flow indicator standard exposed first, followed by the flow indicator covered. The subjects were asked to perform 2 inhalations on their incentive spirometers in the first flow indicator condition: covered or the standard exposed. After a 2-min delay, the subjects were then asked to perform an additional 2 inhalations with the alternate flow indicator condition. The difference between mean inspiratory volumes under covered and standard exposed conditions was evaluated for all subjects, within and between groups.
RESULTS: A total of 42 subjects were evaluated. For all the subjects, there was a mean increase of 255.4 mL of inspired volume when the flow indicator was covered (1,869.0 vs 1,613.7 mL, P < .001). For the subjects in group B who had their flow indicators covered after standard exposure, mean inspiratory volumes increased by 285.7 mL (1,613.1 vs 1,898.8 mL, P = .009). For subjects in group A who had their flow indicator covered before standard exposure, their mean inspiratory volumes increased by 225.0 mL (1,614.3 vs 1839.3 mL, P = .007) when covered. There was no significant difference between the mean increases across patients in groups A and B (225.0 vs 285.7 mL, P = .63).
CONCLUSIONS: Covering the flow indicator during incentive spirometers significantly increased achieved inspiratory volumes. Increased volumes were generated, irrespective of flow indicator covering order, which strongly suggested that the covering effect was greater than any learning or condition order carry-over effects. Because achieving target inspiratory volumes is considered the most important factor in successful incentive spirometers use, these findings may have immediate applications for improving incentive spirometers protocols, patient education, and device design implications.
- incentive spirometry
- quality improvement
- flow
- inspiratory volume
- respiratory care
- hand positioning
- patient education
- human factors
Introduction
Ubiquitously prescribed1 to reduce postoperative pulmonary complications, incentive spirometers were originally developed to facilitate sustained maximum inspiration.2 Achieving target inspiratory volume is believed to be the most important factor in successful incentive spirometers use.3 Furthermore, as an objective marker of deep-breathing effort, inspiratory volume is a commonly used outcome measure,4–9 which has been correlated with various clinical outcomes.10–12 Unfortunately, many patients may not know how to optimally use incentive spirometers and maximize inspiratory volume in the postoperative setting.13
Difficulties with incentive spirometers use may stem, in part, from the device design. In addition to a slow-rising float that indicates volume displacement (Fig. 1C), the incentive spirometers includes a sensitive, rapid-fluttering flow indicator (Fig. 1A). The flow indicator includes symbols with instructional suggestions for patients about maintaining adequate flow (Fig. 1A). Further, the motion onset of the rapid-fluttering flow indicator occurs before that of the volume float. It is well-established that attention is drawn to moving objects in the visual field.14–18 In particular, motion onset (the state of no motion changing to some motion)16 has been demonstrated to draw attention, which is needed to effectively perform tasks.19–21 With the incentive spirometers flow indicator, such cues may draw the patients' attention toward the flow indicator rather than toward the volume. In so doing, patients may fail to focus on maximizing inspiratory volume. Hence, the objective of the present investigation was to evaluate the effects of covering the flow indicator with hand positioning to determine the corresponding effects on inspiratory volumes. It was hypothesized that covering the flow indicator during patient use would increase inspiratory volume.
A: Flow indicator close up. B: Incentive spirometry unit. C: Volume chamber close up.
QUICK LOOK
Current knowledge
Incentive spirometry is commonly used by patients in the postoperative period to help promote maximal inspiration and prevent pulmonary complications.
What this paper contributes to our knowledge
Patients perform larger inhalations using IS when the flow meter is visually obstructed. These findings suggest a redesign of IS may be useful.
Methods
Study Design
This investigation was a single-center, randomized experiment. Postoperative patients on the orthopedic surgery service at a large academic medical center were evaluated; all the patients were prescribed an incentive spirometers as standard of care and were thus eligible for inclusion. This study was approved by our medical center's institutional review board (45 CFR § 46. 110(5)). Over 2 d in November and December 2017, data were collected from consenting subjects. To create a counter-balanced crossover design, a simple alternating assignment was used to randomize subjects to 1 of 2 study groups based on successive patient room numbers.
Study Groups
Subjects randomized to study group A attempted IS by initially having their flow indicator covered (Fig. 2A). This was then followed by repeating the attempt with the flow indicator standard exposed (Fig. 2B). The subjects randomized to group B had this order reversed to attempt incentive spirometers with their flow indicator standard initially exposed, which was then followed by a repeated attempt with the flow indicator covered. The subjects were asked to perform 2 inhalations with their incentive spirometers in the first flow indicator condition. After a 2-min delay, the subjects were then asked to perform 2 addition inhalations with the alternate flow indicator condition (Table 1). Inspiratory volume was measured by the peak height of the volume displacement float (Fig. 3). The higher of the 2 inspiratory volumes from each condition was recorded.
Flow indicator conditions. A: Covered. B: Standard exposed.
Inspiratory volume measurement (red arrow).
Diagram of Intervention by Group
Statistical Analysis
The mean inspiratory volumes were calculated for all subjects during the covered (ISVC) and standard exposed (ISVS) conditions, and individual differences were evaluated (ΔISV = ISVC − ISVS). Paired t tests were used to test differences in individual performance (ISVC vs ISVS) among all the subjects and among those in each subgroup. To assess the presence of the confounding effects between the subgroups, the mean volumes and ΔISV of subjects in groups A and B were assessed for equality by using t tests.
Results
A total of 42 postoperative subjects were included, each of whom had IS prescribed after different orthopedic procedures and consented to the investigation. A total of 21 subjects were randomized to study group A and 21 to study group B. By using a counter-balanced study design, the subjects served as their own controls, which avoided the need for data collection of subject demographics or characteristics.
All Subjects
Overall, the subjects performed IS with a mean (SD) inspiratory volume of 1,613.7 (695.9) mL and 1,869.0 (755.5) mL with the flow indicator exposed and covered, respectively. Pairwise analysis demonstrated a significant difference in inspiratory volumes when the flow indicator was covered by hand positioning (P < .001), with a mean increase of 255.4 mL (Table 2).
Impact of Covering Flow Indicator on Inspiratory Volumes
Subgroup Analysis
There were no significant differences between subject performance in groups A versus B under the standard exposed (1,614.3 vs 1,613.1 mL, P > .99) and covered conditions (1,839.3 vs 1,898.8 mL, P = .80). In each group, there were significant increases between inspiratory volumes during the covered condition: group A ISVS of 1,614.3 mL versus group A ISVC of 1839.3 mL (P = 0.0068); and group B ISVS of 1,613.1 mL versus group B ISVC of 1,898.8 mL (P = .009). The subjects in groups A and B had mean increases of 225.0 and 285.7 mL, respectively, under the covered condition. However, there was no statistically significant difference in performance improvement between the groups (225.0 vs 285.7 mL, P = .63). Of note, subjects in group A performed IS under the covered condition first; thus, the ΔISV in this subgroup represented a 225.0 mL decrease in inspiratory volume when incentive spirometers was repeated with standard exposure. Although the subjects in both groups showed improved inspiratory volume when the flow indicator was covered, there was no statistically significant difference in mean ΔISV of group A versus group B (225.0 vs 285.7 mL, P = .63).
Discussion
A prospective, counter-balanced crossover analysis of postoperative subjects who served as their own controls was completed to evaluate the effects of covering the flow indicator on inspiratory volumes in incentive spirometers. As was hypothesized, covering the flow indicator during use by the subject increased inspiratory volumes. Increased volumes were generated irrespective of flow indicator covering order, which strongly indicated that the covering effect was greater than any learning or condition order carry-over effects. A recent national survey demonstrated that most nurses and respiratory therapists consider achieving target inspiratory volume to be the most important factor in successful incentive spirometers.3 In addition, inspiratory volume during incentive spirometers has repeatedly been identified as a surrogate for inspiratory capacity4–9 and is correlated with clinical outcomes.10–12
To our knowledge, this was the first investigation to evaluate covering the flow indicator in incentive spirometers. The increase in inspiratory volumes during the covered versus standard exposed condition indicated that previous incentive spirometers studies may not have captured accurate maximum inspiratory volumes. Moreover, this was the first investigation to evaluate how incentive spirometers was administered and to highlight its importance.
The study was potentially limited by the relatively small sample of subjects included in this analysis. Future studies may benefit from larger samples and evaluation of subjects with a variety of conditions, such as those with rib fractures, those who require intensive care, or those who have undergone cardiothoracic or upper abdominal surgery. Because this study was at a single center, a multi-center investigation could strengthen the findings and make the results more generalizable. By design, subject demographics and baseline characteristics were not collected because the subjects served as their own control. Therefore, there was no need to perform cohort matching. Further, there were no significant differences between baseline inspiratory performances in each subgroup. Data collection was completed on randomly selected dates and times. Interesting further investigations may include the following: various subject samples, a control for postoperative day, subject eye gaze patterns, subject distraction during incentive spirometers, impact of greater inspiratory volumes on clinical outcomes, comparison of different incentive spirometers devices, and the interaction of anesthesia type on cognition and incentive spirometers compliance.
Conclusions
Human factors, for example, hand placement during incentive spirometers performance, may affect successful utilization and overall clinical effectiveness of incentive spirometers use. Because achieving target inspiratory volumes is considered the most important factor in successful incentive spirometers use, these findings may have immediately applicable implications for optimizing incentive spirometers protocols, device design, and patient education.
Footnotes
- Correspondence: Adam EM Eltorai PhD, Warren Alpert Medical School of Brown University, 222 Richmond Street, Providence, RI 02906. E-mail: adam_eltorai{at}brown.edu.
Dr AEM Eltorai and Mr Martin are co-first authors.
Disclosures: No funding was received for this work.
Dr AEM Eltorai discloses a relationship with Springer and Lippincott Williams & Wilkins. Dr Daniels discloses relationships with SpineArt, Globus, Orthofix, Springer, and Stryker. The remaining authors have disclosed no conflicts of interest.
- Copyright © 2019 by Daedalus Enterprises
