Abstract
To compare lung function in wheezing and non-wheezing infants with pneumonia through tidal breathing analysis and explore the correlation between tidal breathing lung function and clinical characteristics. This retrospective observational study included infants with pneumonia hospitalized in the Affiliated Hospital of Guizhou Medical University between January 2018 and December 2018. Medical records were used to obtain the demographic characteristics, clinical characteristics, tidal breathing lung function results before and after a bronchodilator test, and positive remission rates after the bronchodilator test for each patient. Eighty-six wheezing infants (64 males, aged 6.5 [4.8, 9] months) and 27 non-wheezing infants (18 males, aged 7 [5, 12] months) were included. Non-wheezing infants were more likely to have normal airway function compared to wheezing infants (44.4% vs 23.3%, P = .033). Peak tidal expiration flow/tidal expiratory flow (TEF)25 in wheezing infants was significantly higher than that in non-wheezing infants (162.4 [141.2, 200.7] vs 143.3 [131, 178.8], P = .037). The positive remission rate of tidal inspiratory flow (TIF50)/TEF50 (53.5% vs 29.6%, P = .03) and TEF50 (58.1% vs 33.3%, P = .024) were significantly higher in the wheezing infants compared to non-wheezing infants (P = .03 and P = .024, respectively). Furthermore, respiratory rate, tidal volume, peak expiration flow, TEF25, TEF50, and TEF75 were significantly correlated to the age, height, weight, and platelet counts of infants in both the wheezing and non-wheezing infants (all P < .05). Wheezing infants with pneumonia were more likely to have worse tidal breathing lung function compared to non-wheezing infants with pneumonia. The tidal breathing lung function parameter (respiratory rate, tidal volume, peak expiration flow, TEF25, TEF50, and TEF75) were correlated to the age, height, weight, and platelet counts of both wheezing and non-wheezing infants.
Keywords: infants, non-wheezing pneumonia, observational study, tidal breathing lung function, wheezing pneumonia
1. Introduction
Pneumonia is a common acute lower respiratory tract infection and is the leading infectious cause of infant mortality worldwide.[1] In developed countries with abundant resources, the rate of pneumonia is <1% in full-term infants and about 30% in preterm infants.[2] In developing countries with limited resources, pneumonia is a leading cause of mortality in children under 5 years of age. The World Health Organization estimates that pneumonia is responsible for 14% of deaths in children under 5 and killed approximately 750,000 young children in 2019.[3] Even though pneumonia is caused by an underlying infection, an inappropriate host response leading to excessive inflammation is believed to be responsible for the pathogenesis of the disease.[4]
Approximately 30% of infants experience at least 1 wheezing attack in the first year of life.[5,6] A previous study suggested that wheezing infants with pneumonia should be treated with a unique management algorithm since antibiotic failure occurs more commonly in this group.[7] Wheezing occurs more commonly prior to, during, and after an episode of pneumonia.[8] Moreover, there is a strong relationship between infant pneumonia with wheezing and recurrent wheezing in children after 1-year-old.[9] Early childhood pneumonia with wheezing has also been shown to be related to the development of childhood asthma.[10] It is likely there is a close association between wheezing and pneumonia, whereby wheezing predisposes infants to pneumonia and pneumonia also exacerbates wheezing.
Spirometry testing is the most common method used to dynamically evaluate the condition and obstruction of the airway in older children and adults.[11,12] Evaluating airway obstruction in infants is more complicated because they cannot cooperate with spirometry testing.[13,14] Tidal breathing analysis is the most common method used to evaluate lung function in infants because it is carried out passively during quiet breathing by either measuring flow from the airway opening by pneumotachograph or by measuring chest motions by respiratory inductance plethysmography.[15] Bronchodilator tests measure the variability and reversibility of airway obstruction by conducting breathing analysis before and after inhalation of a short-acting bronchodilator.[16] Both tests play important roles in the diagnosis, treatment, and prognostication of airway illness in infants.[17]
Despite the clear link between pneumonia and wheezing, there is a lack of studies that compare wheezing infants with pneumonia and non-wheezing infants with pneumonia regarding tidal breathing analysis and bronchodilator tests. Therefore, this study aims to compare the tidal breathing lung function of wheezing and non-wheezing infants with pneumonia before and after bronchodilator tests and explores the correlation between tidal breathing lung function and clinical characteristics.
2. Methods
2.1. Study design and population
This retrospective observational study included infants who were hospitalized in the pediatric respiratory ward of the hospital affiliated to Guizhou Medical University between January 2018 and December 2018. The inclusion criteria were infants who were diagnosed with infant pneumonia and infants who had completed both tidal breathing lung function and bronchodilator tests within 2 days of admission. Pneumonia was diagnosed according to Zhu Futang’s “Practical Paediatrics” (Eighth Edition).[18] Infants diagnosed with immunodeficiency, congenital heart disease, bronchopulmonary dysplasia, bronchial softening, or other heart or lung diseases were excluded. Patients with wheezing were assigned to the wheezing group and patients without wheezing were assigned to the non-wheezing group.
The present study was conducted in accordance with the principles of the Declaration of Helsinki. The study protocol was authorized by the Ethics Committee of the Affiliated Hospital of Guizhou Medical University (2021-019). Informed consent was waived for the retrospective nature of this study.
2.2. Data collection and definitions
Medical records were used to obtain the demographic characteristics (age, sex, height, weight, and premature delivery) and clinical characteristics (duration of hospital stay, condition, and the counts of hemoglobin, thrombocyte, and C-reactive protein of patients), as well as the results of tidal breathing lung function analysis before and after bronchodilator test and positive remission rates after the bronchodilator tests.
The 13 indicators of tidal breathing lung function are respiratory rate (RR), tidal volume (VT), VT/kg, time to peak tidal expiratory flow as a proportion of expiratory time (TPTEF/TE), volume to peak expiratory flow as a proportion of exhaled volume (VPEF/VE), peak tidal expiratory flow/tidal expiratory flow when 75% of tidal volume remains in the lung (PTEF/TEF25), peak tidal expiratory flow/tidal volume (PTEF/VT), tidal expiratory flow when 50% of tidal volume remains in the lung/tidal inspiratory flow when 50% of tidal volume remains in the lung (TEF50/TIF50), inspiratory time/expiratory time (TI/TE), peak expiration flow (PEF), tidal expiratory flow when 75% of tidal volume remains in the lung (TEF25), tidal expiratory flow when 50% of tidal volume remains in the lung (TEF50), and tidal expiratory flow when 25% of tidal volume remains in the lung (TEF75).
Airway obstruction was classified into normal tidal breathing lung function (both TPTEF/TE and VPEF/VE were more than 29), mild obstruction (both TPTEF/TE and VPEF/VE were between 23 and 28), moderate obstruction (TPTEF/TE or VPEF/VE was between 15 and 22), and severe obstruction (TPTEF/TE or VPEF/VE was <15).
Positive remission rates were calculated as the number of patients who achieved remission after the bronchodilator test/the total number of patients who received the bronchodilator test. And a tidal breathing lung function indicator was defined as remission when it changed positively after the test.
2.3. Statistical analysis
SPSS 21.0 (IBM, Armonk, NY) was used for statistical analysis. The distribution of continuous data was skewed, and these data are presented as median and interquartile range. The Mann–Whitney U rank-sum test was used for comparing wheezing and non-wheezing infants. Categorical data are presented as numbers and percentages, and chi-square or Fisher exact test were used for comparing wheezing and non-wheezing infants. The Pearson correlation method was used for exploring the correlation between tidal breathing lung function and demographic/clinical characteristics. A 2-sided P < .05 was considered statistically significant.
3. Results
Overall, 113 infants with pneumonia were eligible for this study, including 86 infants in wheezing infants (64 males, aged 6.5 [4.8, 9] months) and 27 infants in non-wheezing infants (18 males, aged 7 [5, 12] months). The wheezing and non-wheezing infants had comparable demographic and clinical characteristics at baseline (all P > .05) (Table 1).
Table 1.
Comparison of demographic and clinical data between the wheezing and non-wheezing infants.
| Characteristics | Wheezing infants (n = 86) | Non-wheezing infants (n = 27) | P |
|---|---|---|---|
| Demographic characteristics | |||
| Age (mo) | 6.5 (4.8, 9) | 7 (5, 12) | .166 |
| Male | 64 (74.4) | 18 (66.7) | .431 |
| Height | 68 (62.8, 72) | 68 (60, 80) | .231 |
| Weight | 8 (7, 9.5) | 8 (6, 10) | .927 |
| Premature delivery | 5 (5.8) | 3 (11.1) | .394 |
| Clinical characteristics | |||
| Hospital stay (d) | 11 (8, 13) | 10 (8, 16) | .847 |
| Serious condition | 11 (12.8) | 2 (7.4) | .730 |
| Hemamoeba | 10.9 (8.5, 12.9) | 10.3 (7.6, 14.9) | .948 |
| Thrombocyte | 450 (368, 541.3) | 416 (327, 553.3) | .395 |
| CRP | 0.8 (0.3, 2.6) | 0.4 (0.2, 2.25) | .311 |
| Tidal breathing lung function | |||
| RR (1/min) | 33.7 (28.2, 37.8) | 33.3 (29.4, 38.1) | .938 |
| VT (mL) | 65.1 (54.1, 78) | 66.2 (48.8, 90.1) | .563 |
| VT/kg (mL/kg) | 8.3 (6.9, 9.4) | 8.4 (7.7, 9.9) | .471 |
| TPTEF/TE (%) | 22.2 (17.2, 27.9) | 24.4 (17.2, 32.4) | .503 |
| VPEF/VE (%) | 25.1 (21.7, 29.1) | 25.4 (21.8, 31.5) | .480 |
| PTEF/TEF25 (%) | 162.4 (141.2, 200.7) | 143.3 (131, 178.8) | .037 |
| PTEF/VT (%) | 158.2 (126.7, 182.8) | 161.1 (133.9, 172.5) | .811 |
| TEF50/TIF50 (%) | 78.1 (65.4, 87.1) | 75.2 (68.6, 94.9) | .652 |
| TI/TE | 0.7 (0.6, 0.8) | 0.7 (0.6, 0.8) | .435 |
| PEF (mL/s) | 98 (83, 122.3) | 96 (75, 132) | 1.000 |
| TEF 25 (mL/s) | 95.5 (81.5, 119) | 94 (75, 130) | .997 |
| TEF 50 (mL/s) | 82.5 (66.8, 99.8) | 87 (71, 111) | .463 |
| TEF 75 (mL/s) | 58 (48.5, 69) | 65 (53, 78) | .115 |
| Airway obstruction | |||
| Normal | 20 (23.3) | 12 (44.4) | .033 |
| Mild | 21 (24.4) | 3 (11.1) | .140 |
| Moderate | 36 (41.9) | 10 (37) | .656 |
| Severe | 9 (10.5) | 2 (7.4) | 1.000 |
Data are expressed as median and interquartile or n (%).
CRP = C-reactive protein, PEF = peak expiration flow, PTEF/TEF25 = peak tidal expiratory flow/tidal expiratory flow when 75% of tidal volume remains in the lung, PTEF/VT = peak tidal expiratory flow/tidal volume, RR = respiratory rate, TEF50 = tidal expiratory flow when 50% of tidal volume remains in the lung, TIF50 = tidal inspiratory flow when 50% of tidal volume remains in the lung, TEF75 = tidal expiratory flow when 25% of tidal volume remains in the lung, TI/TE = inspiratory time/expiratory time, TPTEF/TE = time to peak tidal expiratory flow as a proportion of expiratory time, VPEF/VE = volume to peak expiratory flow as a proportion of exhaled volume, VT = tidal volume.
The indicators of tidal breathing lung function were comparable between infants at baseline (all P > .05), except peak tidal expiration flow (PTEF)/TEF25 was significantly higher in the wheezing infants than that in the non-wheezing infants (162.4 [141.2, 200.7] vs 143.3 [131, 178.8], P = .037). As shown in Table 1, there was a significantly lower proportion of wheezing infants without airway obstruction as compared to non-wheezing infants (23.3% vs 44.4%, P = .033). TPTEF/TE was positively correlated with VPEF/VE in the wheezing and non-wheezing infants (R = 0.964 and R = 0.929, respectively) (Fig. 1).
Figure 1.
Correlation analysis between TPTEF/TE and VPEF/VE. (A) Wheezing pneumonia. (B) Non-wheezing pneumonia. Correlations were analyzed between TPTEF/TE and VPEF/VE in both the wheezing and non-wheezing infants. Positive correlations were evident between TPTEF/TE and VPEF/VE in both the wheezing and non-wheezing infants (R = 0.964, P = .000, and R = 0.929, P = .000, respectively). TPTEF/TE = time to peak tidal expiratory flow as a proportion of expiratory time.
The 13 indicators of tidal breathing lung function were not significantly different before and after the bronchodilator tests in either wheezing or non-wheezing infants (all P > .05). There was also no difference in any indicator of tidal breathing lung function between the wheezing and non-wheezing infants after the bronchodilator tests (all P > .05) (Table 2). The positive remission rates of TIF50/TEF50 (53.5% vs 29.6%, P = .03) and TEF50 (58.1% vs 33.3%, P = .024) were significantly higher in the wheezing infants compared to non-wheezing infants (Table 3).
Table 2.
Comparison of tidal breathing lung function before and after bronchodilator test in the wheezing and non-wheezing infants.
| Characteristics | Wheezing infants (n = 86) | Non-wheezing infants (n = 27) | P * | ||||
|---|---|---|---|---|---|---|---|
| Before | After | P | Before | After | P | ||
| RR (1/min) | 33.7 (28.2, 37.8) | 33.8 (29.6, 39.5) | .511 | 33.3 (29.4, 38.1) | 32.1 (28, 41.5) | .887 | .708 |
| VT (mL) | 65.1 (54.1, 78) | 64.3 (51.7, 76.7) | .821 | 66.2 (48.8, 90.1) | 64.6 (52.2, 91.2) | .895 | .638 |
| VT/kg (mL/kg) | 8.3 (6.9, 9.4) | 8.4 (6.9, 9.3) | .790 | 8.4 (7.7, 9.9) | 8.9 (7, 10.1) | .763 | .250 |
| TPTEF/TE (%) | 22.2 (17.2, 27.9) | 22.1 (16.8, 26.2) | .620 | 24.4 (17.2, 32.4) | 27.2 (19.2, 32.1) | .630 | .042 |
| VPEF/VE (%) | 25.1 (21.7, 29.1) | 25.4 (21.5, 29.1) | .961 | 25.4 (21.8, 31.5) | 29.3 (22.9, 31) | .657 | .081 |
| PTEF/TEF25 (%) | 162.4 (141.2, 200.7) | 163.6 (135.8, 193.5) | .731 | 143.3 (131, 178.8) | 139.4 (129.8, 167.3) | .955 | .066 |
| PTEF/VT (%) | 158.2 (126.7, 182.8) | 157.1 (121.6, 189.4) | .795 | 161.1 (133.9, 172.5) | 141.8 (113.8, 182.7) | .515 | .275 |
| TEF50/TIF50 (%) | 78.1 (65.4, 87.1) | 77.3 (64.9, 87.4) | .901 | 75.2 (68.6, 94.9) | 77.8 (63.4, 86.1) | .473 | .720 |
| TI/TE | 0.7 (0.6, 0.8) | 0.7 (0.6, 0.8) | .760 | 0.7 (0.6, 0.8) | 0.7 (0.6, 0.8) | .977 | .495 |
| PEF (mL/s) | 98 (83, 122.3) | 97 (83.5, 122) | .928 | 96 (75, 132) | 98 (69.3, 131.5) | .843 | .896 |
| TEF 25 (mL/s) | 95.5 (81.5, 119) | 96 (82.3, 118.8) | .946 | 94 (75, 130) | 92.5 (67.5, 130) | .858 | .926 |
| TEF 50 (mL/s) | 82.5 (66.8, 99.8) | 84.5 (69, 101) | .650 | 87 (71, 111) | 88 (60.3, 108.3) | .671 | .969 |
| TEF 75 (mL/s) | 58 (48.5, 69) | 58.5 (50, 71.5) | .722 | 85 (53, 78) | 59.5 (47, 89) | .748 | .492 |
Data are presented as median and interquartile spacing.
PEF = peak expiration flow, PTEF/TEF25 = peak tidal expiratory flow/tidal expiratory flow when 75% of tidal volume remains in the lung, PTEF/VT = peak tidal expiratory flow/tidal volume, RR = respiratory rate, TEF25 = tidal expiratory flow when 75% of tidal volume remains in the lung, TEF50 = tidal expiratory flow when 50% of tidal volume remains in the lung, TEF50/TIF50 = tidal expiratory flow when 50% of tidal volume remains in the lung/tidal inspiratory flow when 50% of tidal volume remains in the lung, TEF75 = tidal expiratory flow when 25% of tidal volume remains in the lung, TI/TE = inspiratory time/expiratory time, TPTEF/TE = time to peak tidal expiratory flow as a proportion of expiratory time, VPEF/VE = volume to peak expiratory flow as a proportion of exhaled volume, VT = tidal volume.
Comparison of tidal breathing lung function value after bronchodilator test between wheezing infants and non-wheezing infants.
Table 3.
Comparison of tidal breathing lung function remission rates after a bronchodilator test in the wheezing and non-wheezing infants.
| Wheezing infants (n = 86) | Non-wheezing infants (n = 27) | P | |
|---|---|---|---|
| RR (1/min) | 47 (54.7) | 14 (51.9) | .799 |
| VT (mL) | 40 (46.5) | 13 (48.1) | .882 |
| VT/kg (mL/kg) | 40 (46.5) | 13 (48.1) | .882 |
| TPTEF/TE (%) | 44 (51.2) | 11 (40.7) | .345 |
| VPEF/VE (%) | 45 (52.3) | 11 (40.7) | .294 |
| PTEF/TEF25 (%) | 44 (51.2) | 12 (44.4) | .542 |
| PTEF/VT (%) | 45 (52.3) | 10 (37) | .166 |
| TEF50/TIF50 (%) | 46 (53.5) | 8 (29.6) | .030 |
| TI/TE | 43 (50) | 13 (48.1) | .867 |
| PEF (mL/s) | 45 (52.3) | 11 (40.7) | .294 |
| TEF 25 (mL/s) | 45 (52.3) | 10 (37) | .166 |
| TEF 50 (mL/s) | 50 (58.1) | 9 (33.3) | .024 |
| TEF 75 (mL/s) | 46 (53.5) | 11 (40.7) | .248 |
Data are presented as n (%).
PEF = peak expiration flow, PTEF/TEF25 = peak tidal expiratory flow/tidal expiratory flow when 75% of tidal volume remains in the lung, PTEF/VT = peak tidal expiratory flow/tidal volume, RR = respiratory rate, TEF25 = tidal expiratory flow when 75% of tidal volume remains in the lung, TEF50 = tidal expiratory flow when 50% of tidal volume remains in the lung, TEF50/TIF50 = tidal expiratory flow when 50% of tidal volume remains in the lung/tidal inspiratory flow when 50% of tidal volume remains in the lung, TEF75 = tidal expiratory flow when 25% of tidal volume remains in the lung, TI/TE = inspiratory time/expiratory time, TPTEF/TE = time to peak tidal expiratory flow as a proportion of expiratory time, VPEF/VE = volume to peak expiratory flow as a proportion of exhaled volume, VT = tidal volume.
The correlation analysis indicated that RR and PTEF/VT were negatively correlated with age, height, and weight, while the tidal volume, PEF, TEF25, TEF50, and TEF75 were positively correlated with age, height, and weight. In addition, VT, PEF, TEF25, TEF50, and TEF75 were negatively correlated with platelet counts in both wheezing and non-wheezing infants (Table 4).
Table 4.
Correlation between tidal breathing lung function and clinical data in the wheezing and non-wheezing infants.
| Wheezing infants (n = 86) | Non-wheezing infants (n = 27) | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Age | Height | Weight | Platelet | Age | Height | Weight | Platelet | |||||||||
| r | P | r | P | r | P | r | P | r | P | r | P | r | P | r | P | |
| RR (1/min) | −0.32 | .003 | −0.239 | .027 | −0.172 | .114 | −0.018 | .872 | −0.515 | .006 | −0.520 | .005 | −0.459 | .016 | 0.14 | .494 |
| VT (ml) | 0.741 | <.001 | 0.632 | <.001 | 0.615 | <.001 | −0.225 | .037 | 0.883 | <.001 | 0.861 | <.001 | 0.862 | <.001 | −0.47 | .015 |
| VT/kg (ml/kg) | 0.11 | .313 | −0.047 | .667 | −0.251 | .02 | −0.002 | .987 | 0.529 | .005 | 0.48 | .011 | 0.42 | .029 | −0.207 | .311 |
| TPTEF/TE (%) | −0.133 | .221 | −0.068 | .535 | −0.04 | .715 | −0.008 | .939 | −0.107 | .594 | −0.062 | .757 | −0.116 | .565 | 0.041 | .844 |
| VPEF/VE (%) | −0.133 | .222 | −0.099 | .367 | −0.067 | .541 | −0.012 | .914 | −0.092 | .647 | −0.036 | .86 | −0.099 | .623 | −0.046 | .822 |
| PTEF/TEF25 (%) | 0.001 | .995 | −0.111 | .307 | −0.172 | .113 | 0.003 | .975 | 0.059 | .768 | −0.023 | .91 | 0.012 | .952 | −0.053 | .798 |
| PTEF/VT (%) | −0.229 | .034 | −0.213 | .049 | −0.190 | .08 | −0.033 | .765 | −0.436 | .023 | −0.482 | .011 | −0.399 | .039 | 0.018 | .929 |
| TEF50/TIF50 (%) | 0.003 | .975 | 0.025 | .82 | −0.046 | .677 | −0.086 | .432 | −0.081 | .686 | −0.056 | .78 | −0.067 | .738 | −0.068 | .742 |
| TI/TE | −0.085 | .446 | −0.068 | .545 | −0.153 | .169 | 0.088 | .431 | −0.158 | .442 | −0.126 | .54 | −0.159 | .437 | 0.036 | .863 |
| PEF (ml/s) | 0.483 | <.001 | 0.394 | <.001 | 0.43 | <.001 | −0.254 | .018 | 0.734 | <.001 | 0.658 | <.001 | 0.745 | <.001 | −0.545 | .004 |
| TEF 25 (ml/s) | 0.482 | <.001 | 0.389 | <.001 | 0.422 | <.001 | −0.245 | .023 | 0.729 | <.001 | 0.647 | <.001 | 0.737 | <.001 | −0.527 | .006 |
| TEF 50 (ml/s) | 0.436 | <.001 | 0.406 | <.001 | 0.467 | <.001 | −0.288 | .007 | 0.770 | <.001 | 0.709 | <.001 | 0.800 | <.001 | −0.593 | .001 |
| TEF 75 (ml/s) | 0.4 | <.001 | 0.431 | <.001 | 0.518 | <.001 | −0.25 | .02 | 0.732 | <.001 | 0.707 | <.001 | 0.766 | <.001 | −0.537 | .005 |
PEF = peak expiration flow, PTEF/TEF25 = peak tidal expiratory flow/tidal expiratory flow when 75% of tidal volume remains in the lung, PTEF/VT = peak tidal expiratory flow/tidal volume, RR = respiratory rate, TEF25 = tidal expiratory flow when 75% of tidal volume remains in the lung, TEF50 = tidal expiratory flow when 50% of tidal volume remains in the lung, TEF50/TIF50 = tidal expiratory flow when 50% of tidal volume remains in the lung/tidal inspiratory flow when 50% of tidal volume remains in the lung, TEF75 = tidal expiratory flow when 25% of tidal volume remains in the lung.3, TI/TE = inspiratory time/expiratory time, TPTEF/TE = time to peak tidal expiratory flow as a proportion of expiratory time, VPEF/VE = volume to peak expiratory flow as a proportion of exhaled volume, VT = tidal volume.
4. Discussion
In this study, wheezing infants had significantly higher PTEF/TEF and were more likely to have airway obstruction compared to the non-wheezing infants, and RR, VT, PTEF/VT, PEF, TEF25, TEF 50, and TEF75 were correlated to age, height, weight, and platelet count in both wheezing and non-wheezing infants. The results may provide a theoretical basis for further study on wheezing and pneumonia.
PTEF/TEF25 may be elevated in wheezing patients because it is a sensitive indicator of airway obstruction, particularly small airway obstruction.[19] The relatively smaller lumen of bronchioles, mucosal congestion, and airway edema with large amounts of inflammatory exudate associated with pneumonia cause near obstruction of the airways in infants.[20] Airway muscle spasm was evident in wheezing pneumonia patients, which may be comparable to an acute exacerbation in asthma.[21]
According to TPTEF/TE and VPEF/VE, the severity of small airway obstruction can be classified as normal tidal breathing lung function and mild, moderate, and severe airway obstruction. The lower rates of normal airway condition in wheezing patients in the current study suggest that small airway obstruction was more common in the wheezing infants than that in the non-wheezing infants. Moreover, TPTEF/TE and VPEF/VE usually have a good correlation with each other. In this study, a strong positive correlation was also observed between TPTEF/TE and VPEF/VE in both wheezing and non-wheezing patients, which was consistent with previous investigations.[22]
In this study, the wheezing symptoms of infants with pneumonia improved clinically after nebulization with bronchodilators, while the indicators did not improve statistically significantly. This observation may be explained by several different factors. First, there are a reduced number of beta-adrenergic receptors on the membranes of airway smooth muscle in infants, and these receptors also have reduced activity.[23] Second, during wheezing, the airway is usually filled with mucus secretions, which can reduce the absorption of bronchodilators. Third, when performing the bronchodilator test, the bronchodilator was only administered once, whereas, during clinical nebulization, infants inhale the bronchodilator every few hours. In this study, remission rates of TEF50/TIF50 and TEF50 were higher in infants with wheezing after the bronchodilator test. This indicates that to some extent, inhalation of bronchodilators may decrease airway obstruction and improve tidal breathing lung function in pneumonia patients.
The current study indicates that RR, VT, PTEF/VT, PEF, TEF25, TEF 50, and TEF75 were closely related to age, height, weight, and platelet count. Consistent with other research results,[24,25] in this study, RR and PTEF/VT were negatively correlated with age, height, and weight, while VT, PEF, TEF25, TEF50, and TEF75 were positively correlated with these variables. In addition, recent studies have shown that thrombocytosis is related to increased severity of pneumonia in infants, especially in infancy.[26,27] In the present study, the indicators of tidal breathing lung function, such as VT, PEF, TEF25, TEF50, and TEF75, were also inversely correlated with platelet counts.
There are several limitations to this study. First, there was a limited sample size of non-wheezing patients, for tidal breathing lung function tests were more common in wheezing patients, and non-wheezing patients were less likely to undergo tidal breathing lung function tests. Second, this was a single-center retrospective study, and the sample size was limited. Therefore, there was only a trend of difference in tidal breathing lung function and bronchodilator test without statistical significance between wheezing and non-wheezing patients. Further studies with a larger sample size are needed to verify the result. Finally, healthy infants with normal lung function were not included in this study, and future studies should explore the difference between healthy and wheezing/non-wheezing pneumonia infants.
5. Conclusions
In conclusion, wheezing infants with pneumonia were more likely to have worse tidal breathing lung function compared to non-wheezing infants with pneumonia. Wheezing infants were also more likely to experience remission in response to bronchodilators. Additionally, tidal breathing lung function in infants was correlated with age, height, weight, and platelet counts.
Author contributions
Conceptualization: Yiyi Yu.
Data curation: Xiaoping Zhu, Bo Li, Jun Yang, Yali Zhang, Xuesong Wang, Jing Luo, Youyan Wang, Yingying Xuan.
Formal analysis: Yiyi Yu, Wenjuan Meng.
Writing – original draft: Yiyi Yu.
Writing – review & editing: Wenjuan Meng.
Abbreviations:
- PEF
- peak expiration flow
- PTEF
- peak tidal expiration flow
- PTEF/VT
- peak tidal expiratory flow/tidal volume
- RR
- respiratory rate
- TEF
- tidal expiratory flow
- TPTEF/TE
- time to peak tidal expiratory flow as a proportion of expiratory time
- VT
- tidal volume
This work was supported by the Science and Technology Fund of Guizhou Health Commission (gzwjkj2020-1-141).
All procedures were performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. The study protocol was approved by Ethics Committee of the Affiliated Hospital of GuiZhou Medical University (2021-019). The requirement for individual Informed consent was waived by the Ethics Committee of the Affiliated Hospital of GuiZhou Medical University. The study was carried out in accordance with the applicable guidelines and regulations.
The authors have no conflicts of interest to disclose.
All data generated or analyzed during this study are included in this published article [and its supplementary information files].
How to cite this article: Yu Y, Meng W, Zhu X, Li B, Yang J, Zhang Y, Wang X, Luo J, Wang Y, Xuan Y. Tidal breathing lung function analysis of wheezing and non-wheezing infants with pneumonia: A retrospective observational study. Medicine 2023;102:15(e33507).
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