OBJECTIVES:

To explore and define contemporary trends in the use of invasive mechanical ventilation (IMV) and noninvasive ventilation (NIV) in the treatment of children with asthma.

METHODS:

We performed a serial cross-sectional analysis using data from the Pediatric Health Information System. We examined 2014–2018 admission abstracts from patients aged 2 to 17 years who were admitted to member hospitals with a primary diagnosis of asthma. We report temporal trends in IMV use, NIV use, ICU admission, length of stay, and mortality.

RESULTS:

Over the study period, 48 hospitals reported 95 204 admissions with a primary diagnosis of asthma. Overall, IMV use remained stable at 0.6% between 2014 and 2018 (interquartile range [IQR]: 0.3%–1.1% and 0.2%–1.3%, respectively), whereas NIV use increased from 1.5% (IQR: 0.3%–3.2%) to 2.1% (IQR: 0.3%–5.6%). There was considerable practice variation among centers, with NIV rates more than doubling within the highest quartile of users (from 4.8% [IQR: 2.8%–7.5%] to 13.2% [IQR: 7.4%–15.2%]; P < .02). ICU admission was more common among centers with high NIV use, but centers with high NIV use did not differ from lower-use centers in mortality, IMV use, or overall average length of stay.

CONCLUSIONS:

The use of IMV is at historic lows, and NIV has replaced it as the primary mechanical support mode for asthma. However, there is considerable variability in NIV use. Increased NIV use was not associated with a change in IMV rates, which remained stable. Higher NIV use was associated with increased ICU admissions. NIV’s precise contribution to the cost and quality of care remains to be determined.

What’s Known on This Subject:

Although asthma remains a common chronic disease, there is variation in the management of children admitted with asthma exacerbations. Noninvasive ventilation (NIV) and invasive mechanical ventilation can be used to support these patients, but recent trends in their use are unknown.

What This Study Adds:

There was significant interhospital variability in the use of NIV over the study period. At centers with high NIV use, we saw no impact on intubation rates or mortality, but we did see markedly increased ICU use.

Asthma remains one of the most common chronic diseases of childhood and is a leading cause of pediatric hospitalization.13  The proportion of admitted patients with critical asthma, defined as status asthmaticus or admission to the ICU, may be increasing.4,5  There is considerable variation in the management of critical asthma,69  with reported intubation and invasive mechanical ventilation (IMV) rates ranging from 6% to >20% for patients admitted to the ICU5,6,810  and ∼1% for all admitted patients with asthma.11  Although endotracheal intubation carries high morbidity in patients with asthma,12,13  there is some suggestion that rates of IMV may be increasing.11 

Noninvasive ventilation (NIV) offers an alternative to IMV for the management of acute respiratory failure. There are multiple small studies, including 2 randomized controlled trials, which support the safety and efficacy of NIV for patients with asthma.6,1418  However, in the absence of large randomized trials, the most recent Cochrane review concludes that there is insufficient evidence to determine the impact of NIV on patients with critical asthma.19  Even in the absence of a consensus opinion on the utility of NIV, one review of a nationwide database in the United States described an increase in the use of NIV for asthma from 2000 to 2009.11 

Despite recent research into and description of NIV use in critical asthma, information on national trends and outcomes is lacking. We hypothesized that NIV has moved from novel therapy to wide adoption, that it has decreased the need for IMV, and that this practice shift has been associated with an overall decrease in mortality. To test this hypothesis, we used a large multicenter administrative data set to examine NIV use within American children’s hospitals from 2014 to 2018.

We examined inpatient hospitalizations for asthma within the Pediatric Health Information System (PHIS) data set. This is a multi-institutional database that draws from 52 children’s hospitals and is maintained by the Children’s Hospital Association. The PHIS data set contains a wide range of encounter-specific data, including clinical and financial elements. Data quality is ensured via partnerships between the Children’s Hospital Association and participating members.

We queried discharge data from January 2014 to December 2018 for children ages 2 to 17 admitted with a primary diagnosis of asthma. Encounters were identified on the basis of International Classification of Diseases, Ninth Revision (ICD-9) and International Classification of Diseases, 10th Revision (ICD-10) codes (ICD-9 codes: 493.0x, 493.1x, 493.2x, 493.8x, and 493.9x; ICD-10 codes: J45.2x, J45.3x, J45.4x, J45.5x, and J45.9xx). Four hospitals were excluded from our analysis: 2 because they lacked data for some study years and 2 because of reporting errors arising in the transition from ICD-9 to ICD-10.

We examined patient demographic data for each admission, including age, sex, race, and insurer. Collected outcome measures included the use of IMV and NIV, admission to the ICU, hospital length of stay (LOS), and mortality. The use of IMV was identified by using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), International Classification of Diseases, 10th Revision, Procedure Coding System (ICD-10-PCS), and Current Procedural Terminology (CPT) procedure codes (ICD-9-CM: 96.04, 96.05, and 96.7x; ICD-10-PCS: 5A1935Z, 5A1955Z, 5A1955Z, 0BH17EZ, and 0BH18EZ; CPT: 31500). We defined NIV as the use of continuous positive airway pressure or bilevel positive airway pressure, identified by their respective procedure codes (ICD-9-CM: 93.90; ICD-10-PCS: 5A0935x, 5A0945x, 5A0955x, and 5A19054; CPT: 94660 and 94662). We used the PHIS ICU flag to identify hospitalizations that included ICU stays. Rates of NIV and IMV use were calculated as the percentage of admissions wherein those treatment modalities were used. For some analyses, hospitals were divided into quartiles according to the frequency of NIV use in 2018.

We report descriptive and summary statistics for the data measures described above. Associations between continuous variables were evaluated by using Pearson correlation, and changes over the study period were evaluated with weighted least squares. Comparisons between IMV and NIV rates were performed by using the Wilcoxon rank test, and differences in LOS among groups of patients and hospitals were assessed by using the Mann–Whitney U test. All statistical analyses were conducted within the Jupyter Notebook environment by using Python 3.7.20 

We identified 95 204 discharges with a primary diagnosis of asthma at 48 hospitals from 2014 to 2018. During the study period, annual admissions for asthma per hospital ranged from 55 to 1358 (median of 355; interquartile range [IQR]: 207–527). Demographic data for patients, including age, sex, race, and insurer, are presented in Table 1. Across all years, ICU care was provided within 18 449 admissions (19%). Among all patients, 90 407 received no assisted ventilation, 4104 received NIV, 587 received IMV, and 106 received both. Initiation of IMV or NIV could have occurred in the referring emergency department, during medical transport, or in the ICU after admission.6  During the study period, there was a 29% reduction in the number of asthma admissions per hospital, with a median of 434 in 2014 (IQR: 308–640) and 306 in 2018 (IQR: 185–495; P < .01). Concomitantly, there was also a 43% reduction in the number of ICU asthma admissions per hospital (median of 97 in 2014 [IQR: 62–157] vs 55 in 2018 [IQR: 34–83]; P = .02).

TABLE 1

Patient Characteristics

Characteristics and SubgroupsAll Patients (N = 95 204)No Assisted Ventilation (n = 90 407)NIV (n = 4104)IMV (n = 693)No Assisted Ventilation Versus NIV, P
Age, y, median (IQR) 6 (3–9) 6 (3–9) 7 (4–11) 9 (5–13) <.001 
Female sex, % (n39.4 (37 471) 39.3 (35 599) 41.8 (1716) 39.3 (256) .001 
Race,a % (n    <.001 
 Asian American 2.8 (2275) 2.9 (2626) 2.1 (88) 1.6 (11) — 
 Black 42.4 (40 986) 41.9 (38 508) 51.4 (2130) 49.7 (348) — 
 White 36.4 (35 180) 36.7 (33 683) 30.1 (1246) 35.9 (251) — 
 Other or unknown 18.4 (17 802) 18.8 (17 033) 16.5 (679) 13.0 (90)  
Insurance, % (n    <.001 
 Private 29.1 (27 667) 29.0 (26 251) 30.3 (1242) 25.1 (174) — 
 Public 66.2 (63 017) 66.2 (59 821) 66.0 (2706) 70.7 (490) — 
 Self-pay 2.2 (2137) 2.3 (2034) 2.3 (95) ∼2b — 
 Other or unknown 2.5 (2383) 2.5 (2301) 1.5 (61) ∼2b — 
Characteristics and SubgroupsAll Patients (N = 95 204)No Assisted Ventilation (n = 90 407)NIV (n = 4104)IMV (n = 693)No Assisted Ventilation Versus NIV, P
Age, y, median (IQR) 6 (3–9) 6 (3–9) 7 (4–11) 9 (5–13) <.001 
Female sex, % (n39.4 (37 471) 39.3 (35 599) 41.8 (1716) 39.3 (256) .001 
Race,a % (n    <.001 
 Asian American 2.8 (2275) 2.9 (2626) 2.1 (88) 1.6 (11) — 
 Black 42.4 (40 986) 41.9 (38 508) 51.4 (2130) 49.7 (348) — 
 White 36.4 (35 180) 36.7 (33 683) 30.1 (1246) 35.9 (251) — 
 Other or unknown 18.4 (17 802) 18.8 (17 033) 16.5 (679) 13.0 (90)  
Insurance, % (n    <.001 
 Private 29.1 (27 667) 29.0 (26 251) 30.3 (1242) 25.1 (174) — 
 Public 66.2 (63 017) 66.2 (59 821) 66.0 (2706) 70.7 (490) — 
 Self-pay 2.2 (2137) 2.3 (2034) 2.3 (95) ∼2b — 
 Other or unknown 2.5 (2383) 2.5 (2301) 1.5 (61) ∼2b — 

—, not applicable.

a

Encounters can have >1 race reported per patient.

b

Numbers are below the threshold that can be reported per the data use agreement.

From 2014 to 2018, patients admitted for asthma were more likely to receive NIV than IMV, with a median NIV use rate of 1.87% (IQR: 0.44%–4.10%) and an IMV use rate of 0.62% (IQR: 0.48%–1.04%; P < .01). In 2018, the median rate of IMV use for patients admitted to the ICU was 3.6% (IQR: 2.2%–5.5%), whereas the median rate of NIV use was 10.4% (IQR: 1.7%–18.7%). From 2014 to 2018, there was no significant change in the hospital-specific frequency of IMV use (median of 0.6% [IQR: 0.3%–1.1%] in 2014 vs 0.6% [IQR: 0.2%–1.3%] in 2018; P = .43; Fig 1), but NIV use increased in many centers. Across all hospitals, the fraction of patients with asthma receiving NIV increased from a median of 1.5% (IQR: 0.3%–3.2%) in 2014 to 2.1% in 2018 (IQR: 0.3%–5.6%; Fig 1). However, this modest aggregate increase was not statistically significant (P = .15) and belied considerable variability among centers. Stratification of hospitals into NIV use frequency quartiles revealed that some centers seldom employed the modality, whereas others used it often and with increasing frequency (Fig 2A). Across the entire study period, centers in the bottom 3 NIV use quartiles had stable (or even decreasing) rates, whereas those in the top quartile more than doubled their NIV use from 4.8% (IQR: 2.8%–7.5%) in 2014 to 13.2% (IQR: 7.4%–15.2%) in 2018 (P = .02). In Fig 2B, we present these differences more explicitly. Hospitals in this high-use quartile were drawn from all regions of the country and included 4 of the 10 centers with the highest volume of asthma admissions. Overall, but with notable exceptions, hospitals with more asthma admissions tended to use NIV more frequently (P < .01).

FIGURE 1

NIV and IMV use between 2014 and 2018.

FIGURE 1

NIV and IMV use between 2014 and 2018.

Close modal
FIGURE 2

A, Fraction of admissions receiving NIV on the basis of 2018 NIV use quartiles (first: lowest; fourth: highest). B, NIV use by individual hospitals in 2014 and 2018. Hospitals are ordered on the y-axis by increasing 2018 NIV use and are labeled with corresponding quartiles. N is the total number of instances that NIV occurred for admitted patients with asthma in 2018.

FIGURE 2

A, Fraction of admissions receiving NIV on the basis of 2018 NIV use quartiles (first: lowest; fourth: highest). B, NIV use by individual hospitals in 2014 and 2018. Hospitals are ordered on the y-axis by increasing 2018 NIV use and are labeled with corresponding quartiles. N is the total number of instances that NIV occurred for admitted patients with asthma in 2018.

Close modal

Regarding intubation and invasive ventilation, the IMV rate among top-quartile NIV users was slightly higher than that of bottom-quartile users (0.72% [IQR: 0.59%–1.16%] vs 0.55% [IQR: 0.39%–0.67%]), but the difference was not statistically significant (P = .21). Although the NIV rate more than doubled for this top quartile of NIV users over the study period, their IMV rate remained stable (2014 median = 0.76% [IQR: 0.42%–1.14%] vs 2018 median = 0.78% [IQR: 0.55%–1.39%]; P = .36). Across all 5 years and 48 institutions, the percentage of patients who received both NIV and IMV was low, seen within only 106 admissions (0.11% of all admissions). One of the limitations of PHIS is that we are unable to identify the order in which these interventions were administered. These few cases could represent failure of NIV, with progression to IMV, but could also represent postextubation support with NIV. We identified only 71 inpatient deaths due to asthma and no change in mortality across the study period (overall rate of 0.07% in 2014 and 0.05% in 2018; P = .89). The number of patients receiving NIV, IMV, and ultimately dying was small and beneath the reporting threshold permitted by our data use agreements.

Patients receiving NIV exhibited an LOS distribution that was intermediate between those who received no mechanical assistance and those who received IMV (Fig 3). However, because LOS distributions are skewed and short stays dominate average LOS calculations, this had little impact on aggregate LOS measures. Overall average LOS was therefore similar among centers with high and low NIV use (∼2 days; IQR: 1–2 days).

FIGURE 3

Differences in LOS among patients with asthma with differing support requirements.

FIGURE 3

Differences in LOS among patients with asthma with differing support requirements.

Close modal

Although overall ICU use declined nationally, ICU admission rates were much greater in institutions with high NIV use. In 2018, the median ICU admission rate for hospitals in the highest quartile of NIV use was 30.0%, compared with 15.9% for all other hospitals (P < .01). Even so, more than one-quarter (26.6%) of patients with asthma receiving NIV were not admitted to the ICU. Among patients who received NIV, those who received it in the ICU had longer admissions than those who received it outside of the ICU (3 days [IQR: 2–5 days] versus 2 days [IQR: 1–3 days]; P < .01).

In this national sample of children’s hospitals, we found that NIV has replaced IMV as the most common mode of mechanical ventilation in children admitted for asthma. However, we observed considerable practice variation, with NIV used primarily in a subset of hospitals that included centers with the highest asthma admission volumes in the country. Mortality, IMV use, and overall average LOS were similar among centers with high NIV use and low NIV use, but ICU admission rates were much higher in centers with high NIV use.

These trends in NIV and IMV use occurred in the context of significant overall declines in both general and ICU admissions for asthma. Advances in outpatient care may be responsible for these declines, and, if so, illness severity among remaining admissions could be increasing. Although this might bring need for more inpatient ventilatory support, and NIV may be filling some of this need, it does not explain the dramatic practice variability we observed, the similar IMV rates across centers, and the absence of an association between NIV and IMV use.

Preferential use of NIV over IMV departs from previous practice descriptions5,6,8,11  but is consistent with a more recent single-center report.9  Given the risks and morbidity attendant to IMV in patients with asthma, NIV has been proposed as a safer, intermediate alternative that potentially reduces the need for endotracheal intubation.12,13  Indeed, the overall median IMV rate of 0.52% suggests that intubation for asthma has become uncommon. It is now lower than the 1% overall intubation rate that has been previously reported,11  and the 3.7% IMV rate among ICU patients is far below previous reports of 6% to >20%.5,6,810 

We were not able to discern a statistical association between NIV use and IMV use. Even in centers with high NIV use, where the NIV rate more than doubled over the study period, we did not observe an impact on IMV rates. It is possible that the absence of a statistical association simply reflects site practice variation and the relatively low frequency of this target outcome. However, the clinical effectiveness of NIV in asthma remains uncertain,19  and it is equally possible that the increased uptake of NIV has had no impact on intubation rates.

ICU admission is a primary driver of hospitalization costs,9  and ICU crowding is a problem in many institutions.21,22  In the sample here, ∼75% of patients receiving NIV were admitted to an ICU, and, in many institutions, NIV therapy occurs only in the ICU. Although we did observe that high-NIV users had higher ICU admission rates than low-NIV users, ICU admission is driven by many factors rooted in the need for continuous monitoring, treatment, and reassessment. Because we could not control for severity of illness, it is not possible to directly attribute higher ICU use to higher NIV use. We also observed that patients with asthma receiving NIV had significantly longer LOS than those who did not. Given the limitations of retrospective analyses, we believe that the impact of NIV use on patient outcomes, overall costs, and hospital crowding are best determined prospectively.

Our findings should also be considered in the light of several other limitations. First are all limitations inherent in retrospective studies using administrative data sets.23,24  These range from inaccuracies within single-patient records to systematic errors in coding or data handling. Here, we sought to reduce such errors by examining large numbers of patients, changes over time, and multiple institutions. Second, we used primary codes to identify mechanical ventilation use and ICU flags to identify ICU admission. When both were present, we assumed that mechanical ventilation was provided within the ICU, but some patients may have begun NIV outside of an ICU and been transferred later. Third, because we relied on primary diagnoses and did not exclude patients with comorbidities, some patients may have received NIV or IMV for treatment of conditions other than asthma (eg, patients with obstructive sleep apnea, bilevel positive airway pressure dependence, or complex neuromuscular or congenital heart disease). To the extent that such patients were present in our sample, numbers here may overestimate NIV and/or IMV use in uncomplicated asthma. Finally, because the PHIS data set only contains information from participating children’s hospitals, our findings may not reflect care trends in non-PHIS institutions.

NIV is now the predominate mode of ventilatory support in the care of children with asthma, with considerable practice variation. High NIV use was not associated with decreased IMV rates or with decreased mortality. Researchers should use future studies to clarify the impact of NIV on the quality, costs, and outcomes of asthma care.

All authors participated in the conceptualization and design of the study, drafted the manuscript, conducted the analyses, reviewed and revised the manuscript, approved the final manuscript as submitted and agree to be accountable for all aspects of the work, and had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

FUNDING: Supported by the Anesthesia Research Distinguished Trailblazer Award (Boston Children’s Hospital Department of Anesthesiology, Critical Care and Pain Medicine) and by the Boston Children’s Chair for Critical Care Anesthesia.

     
  • CPT

    Current Procedural Terminology

  •  
  • ICD-9

    International Classification of Diseases, Ninth Revision

  •  
  • ICD-9-CM

    International Classification of Diseases, Ninth Revision, Clinical Modification

  •  
  • ICD-10

    International Classification of Diseases, 10th Revision

  •  
  • ICD-10-PCS

    International Classification of Diseases, 10th Revision, Procedure Coding System

  •  
  • IMV

    invasive mechanical ventilation

  •  
  • IQR

    interquartile range

  •  
  • LOS

    length of stay

  •  
  • NIV

    noninvasive ventilation

  •  
  • PHIS

    Pediatric Health Information System

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Competing Interests

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.

FINANCIAL DISCLOSURE: The authors have indicated they have no financial relationships relevant to this article to disclose.