Qualitative Assessment of Intranasal Pressures during Incentive Spirometry

Introduction: Incentive spirometry is routinely prescribed after surgery as a component of pulmonary rehabilitation, aimed to decrease the rate of lung atelectasis postoperatively. It has been suggested that incentive spirometry may negatively affect the pressure within the nasal cavity, and for this reason, it is discouraged in patients who have undergone reconstruction of the skull base. In this study, we seek to measure the intranasal pressures of healthy subjects when using incentive spirometry.

Methods: A previously validated cadaveric model using intracranial sensor catheters has proved to be a reliable technique for measuring sinonasal pressures. These sensors were placed halfway down the nasal cavity floor of 20 healthy individuals without a history of sleep apnea or nasal surgery. Subjects were asked to forcibly inhale, forcibly exhale, and perform 10 consecutive breaths with an incentive spirometer. The subjects were then asked to repeat these tasks while pinching their noses to simulate nasal obstruction. Additionally, each subject was asked to blow their nose. Each set of measurements were performed in triplicate. The average, maximum, and minimum pressures were recorded in mm Hg. The values recorded were corrected for the zero value, and then a Student's t-test was used to compare nopinching (NP) versus pinching (P).

Results: The mean pressure in NP for inhalation was -0.5 ± 1.0 compared with −0.8 ± 1.1 for exhalation and −0.5 ± 1.2 for breathing. The mean pressure in P for inhalation was −1.3 ± 1.3 compared with 1.1 ± 1.4 for exhalation and 1.1 ± 2.6 for breathing. Within (VSN11) NP, mean (−0.5 ± 1.0 vs. −0.8 ± 1.1, p = 0.407), maximum (0.1 ± 1.1 vs. −0.1 ± 1.1, p = 0.638), and minimum (−1.6 ± 1.3 vs. −2.2 ± 2.4, p = 0.345) pressures for inhalation and exhalation were not significantly different. The minimum pressure on forceful inhalation was significantly lower in P (−1.6 ± 1.3 vs. −6.1 ± 2.6, p < 0.001). The maximum pressure on forceful exhalation was significantly greater in p (−0.1 ± 1.1 vs. 6.6 ± 3.5, p < 0.001). The mean (−0.5 ± 1.2 vs. 1.1 ± 2.6, p = 0.017), maximum (−0.1 ± 1.6 vs. 5.1 ± 5.3, p < 0.001), and minimum (−1.1 ± 1.2 vs. −4.1 ± 3.5, p < 0.001) pressures were all significantly different when subjects performed 10 consecutive breaths between NP and P. Analysis of intranasal pressures with nose-blowing revealed maximum pressures of 24.6, significantly greater than those experienced with maximal exhalation in the NP (p < 0.001) or P (p < .001) groups.

Conclusions: Compared with no obstruction (NP), simulation of nasal obstruction (P) significantly increases the absolute pressure experienced in the nasal cavity with maximal inhalation and exhalation during incentive spirometry. As maximum intranasal pressures are much lower than those found with nose-blowing in both NP and P groups, it may be safe to restart patients on incentive spirometry postoperatively, but further investigation is warranted.