Availability of Advanced Practice Providers in Adult Intensive Care Units in the United States: A Survey Free

We conducted a descriptive analysis of existing interprofessional staffing survey data from a national cohort of US ICUs. Our aims were to describe the utilization of APPs (NPs and PAs) and physicians-in-training (interns, residents, and fellows) across the United States, evaluate state-level differences in deployment, and investigate whether state-level APP scope of practice regulations correlated with utilization in the ICUs. As is common in the literature,^8,12,13  we considered APPs together given the relative similarity of NPs’ and PAs’ roles in the ICU setting.

The survey has been described in detail elsewhere.¹⁴  In brief, ICU clinicians (targeting nurse managers and physician directors) were queried in spring 2022 through winter 2023 about the interprofessional staffing and unit characteristics of their ICUs before the COVID-19 pandemic (to obtain steady-state estimates not influenced by COVID-19–related surges). Responses were solicited by direct telephone outreach to all 3664 acute-care hospitals with at least one adult critical care bed in the 2020 American Hospital Association (AHA) survey, and through emails and website postings directed to the membership lists of 4 US critical care societies (the American Association of Critical-Care Nurses, the Society of Critical Care Anesthesiologists, the Society of Critical Care Medicine, and the Critical Care Network of the American College of Chest Physicians). Because of the second sampling strategy, the number of potential respondents is unknown. The ICU survey responses were matched to 2020 AHA annual survey data to characterize hospitals in which surveyed ICUs resided. A single investigator (HBG) performed the matching manually using hospital name, city, and state. For this study, we focused on survey questions pertaining to staffing of APPs (NPs and PAs) and physicians (intensivists and physicians-in-training [interns, residents, critical care fellows, and non–critical care fellows]) and restricted our cohort to ICUs caring for adult patients and for which data on APP and physician-in-training staffing was nonmissing.

We used information available on the websites from the American Association of Nurse Practitioners and the American Academy of Physician Associates on January 4, 2024, to assess state-by-state scope of APP practice authority (Supplemental Figure 1; available online only at ajcconline.org). Full practice for NPs is defined, in line with state licensure laws, as the ability to “evaluate patients; diagnose, order and interpret diagnostic tests; and initiate and manage treatments, including prescribing medications and controlled substances.”³  For PAs, optimal allowance is defined as “practice to the full extent of their medical education, training, and experience” without any “additional administrative requirements … mandated in state law and/or regulation.”⁴  We categorized scope of practice as: (1) full scope (as above, “full” for NPs and “optimal” for PAs) and (2) not full scope (any reduced or restricted practice authority for NPs or PAs).

We categorized ICUs by staffing model into 4 groups, those employing (1) both APPs and physicians-in-training, (2) APPs only, (3) physicians-in-training only, or (4) neither APPs nor physicians-in-training. We used standard summary statistics to describe the cohort, using χ² and Wilcoxon rank sum testing as appropriate to compare characteristics across staffing models. Post hoc, we compared unit characteristics (including staffing models) by hospital environment (metropolitan vs not) owing to differences observed in the initial descriptive analysis.

To evaluate the association of state-level regulations for APP scope of practice, we created a multi-variable logistic regression model (dependent variable: deployment of either NPs or PAs in the ICU; exposure independent variable: state-level APP scope of practice). Covariables included ICU type (single specialty, medical, surgical, mixed medical-surgical), intensivist presence (yes or no), availability of telemedicine in the ICU (not used, overnight only, 24 hours/d, other), ICU size (number of beds), hospital environment (metropolitan vs not), hospital geography by AHA region (1, 2, and 3; 4 and 7; 5 and 6; 8 and 9), hospital size (<100, 100-250, >250 beds), teaching hospital, and hospital type (not for profit, for profit, government).

All analyses were performed using STATA/MP 18 (StataCorp) and Microsoft Excel (Microsoft). P values less than .05 were considered significant; no adjustment was made for multiple comparisons in this descriptive analysis. The institutional review board at the University of Miami Miller School of Medicine approved the study (#20201473), which was carried out in accordance with the ethical standards set forth in the Helsinki Declaration.

We received survey data from 588 unique ICUs caring for adult patients for which information about APPs and physicians-in-training (fellows and residents /interns) was nonmissing (Supplemental Figure 2; available online only at ajcconline.org); we were able to match 571 ICUs (97.1%) to 2020 AHA annual survey data. Of the 588 ICUs, 460 (78.2%) reported having APPs; 314 (53.4%) fellows; 374 (63.6%) residents or interns; and 55 (9.4%) neither (Figure 1). Deployment of APPs, either alone or in conjunction with physicians-in-training, varied across the United States (Figure 2). Among the 460 ICUs with APPs, 154 (33.5%) had only NPs, 47 (10.2%) had only PAs, and 259 (56.3%) had both. Advanced practice providers, fellows, and residents/interns were all present in 228 of the total ICUs (38.8%).

Most ICUs that completed the survey had both APPs and physicians-in-training (n = 336, 57.1%); 124 (21.1%) had APPs only and 73 (12.4%) had physicians-in-training only (Table 1). Units with both APPs and physicians-in-training were more commonly surgical (17.6% vs ≤9.6% for other staffing groups), and units with physicians-in-training only were more commonly medical (20.5% vs ≤9.8%; P < .001). Units with neither APPs nor physicians-in-training were nearly universally mixed ICUs (98.2%), and only 80.0% had intensivists (versus ≥91.9% for all other staffing models, P = .001). These ICUs also tended to be smaller (median [IQR]: 14 [7-20] beds vs 18-20 [12-15 to 22-28] beds for other staffing types, P < .001) and were more commonly in smaller, non-teaching, for-profit hospitals in nonmetropolitan environments in the western United States. Metropolitan ICUs were more commonly staffed by both APPs and physicians-in-training (60.2% vs 25%) and less often had APPs alone (18.8% vs 43%; P < .001; Table 2).

Approximately one-third of ICUs (225 [38.3%]) were in states with full scope of practice regulations for APPs, most of which were in the northeast, mountain, and western United States (Supplemental Figure 1; available online only at ajcconline.org). Staffing of nonintensivist providers varied with APP scope of practice regulations: when full scope was allowed, deployment of APPs alone was less common (16.9% vs 23.7%) but deployment in combination with physicians-in-training was more common (63.6% vs 53.2%; P = .03). No other ICU or hospital characteristics differed significantly (Table 3). After adjustment for ICU and hospital characteristics, the odds of employing APPs were higher among ICUs in states with full scope of practice regulations, yet this result did not reach statistical significance (odds ratio [95% CI]: 1.59 [0.99-2.56], P = .06; Supplemental Table [available online only]).

We found variability in the deployment of APPs and physicians-in-training across US adult ICUs. Notably, while 1 in 5 cohort ICUs deployed APPs alone and 1 in 8 deployed only physicians-in-training, most employed both provider types. Less than 10% of ICUs functioned without APPs or physicians-in-training and, perhaps unsurprisingly, these tended to be smaller units in smaller, nonacademic, for-profit hospitals outside metropolitan environments, although a causal relation between these factors and APP deployment cannot be established. Interestingly, although our finding did not reach statistical significance, the data suggested that state-level allowance of full scope of practice for APPs may be independently associated with an increased odds of the availability of these providers in ICUs.

Epidemiologic data on modern APP staffing in US adult ICUs are sparse. Studies suggest that APPs have been an essential presence in US neonatal ICUs for decades (primarily in the form of NPs).¹⁵  Recent studies demonstrate that APPs are also commonly deployed in modern US pediatric critical care: 70% (28 of 40 surveyed ICUs) of general units across 9 states¹⁶  and the vast majority of pediatric cardiac ICUs nationally (88% [52 of 59 surveyed ICUs] employed NPs and 34% [20 of 59] employed PAs).¹⁷  In adult critical care, APPs have recently been noted to participate in US tele-ICU programs,¹⁸  yet other evidence suggests that integration of APPs into adult critical care has been minimal. For example, APPs make up less than 5% of broad US ICU clinician survey respondents^19,20  and participate in multidisciplinary rounds in 15% or less of military treatment facilities.²¹  Our findings of the presence of APPs in nearly 4 of 5 of our US adult ICUs suggest that the deployment of APPs in adult critical care may be more common than previously appreciated and demonstrate the important role of these providers across ICUs caring for patients of all ages.

Much evidence has accrued over the past decades about the relative safety and effectiveness of employing APPs in the adult ICU setting^8,22 ; yet much of this work has studied APPs as a replacement for physicians-in-training. Our data suggest that a more complex staffing approach may exist. Advanced practice providers may serve as replacements for physicians-in-training—either on certain shifts, to supplement lower numbers of house officers, or in the care of a subset of patients. It is also possible, however, that the 2 provider types are being employed together intentionally (perhaps on the same ICU teams) given their different and potentially complementary school- and experience-based educations, as well as the practiced procedural skills and unit-specific knowledge that full-time ICU APPs provide. Although not fully consistent, most existing literature suggests that physicians-in-training value the presence of APPs in the adult ICU setting—both as colleagues who assist in patient care and to improve their educational experience.^23–25  Exploring how ICUs are using APPs and physicians-in-training when both are available was outside the scope of this survey but such exploration will be important in future studies given the frequency of this staffing model.

After we adjusted the analysis for ICU and hospital characteristics, we found that state-level APP scope of practice regulations may be associated with APP availability in adult ICUs, suggesting that state regulations may impact ICU staffing choices. Currently, more than 50% of states have full practice authority for NPs or optimal practice authority for PAs. However, the remaining states have reduced or restricted scope of practice; this means that APPs are limited in their ability to diagnose, treat, and prescribe and must work with a collaborating or supervising physician in some capacity.⁵  Moreover, Gigli and colleagues²⁶  found that organizational restrictions on practice can exceed those imposed by the state for pediatric ICU NPs. They also demonstrated that patient care responsibilities did not differ in states with full or limited NP practice authority; however, pediatric ICU NPs were less likely to bill for care and more likely to report to advanced practice managers in states with more restricted NP authority.²⁷  In the adult context, APPs are more available in nonacute care settings in states with fuller scope of practice allowances.^28,29  Because APPs often work on ICU teams with an intensivist or other attending physician readily available, it is perhaps overlooked that differences in state-level practice authority regulations may impact APP presence in critical care settings. Whether such a difference based on scope of practice is driven by APPs’ desire to work where they are afforded more authority, as is known in the outpatient setting,³⁰  or by decisions made by the ICU or hospital is unknown. Regardless, this reality may limit the opportunity for all ICUs across the country to realize their optimal staffing model.

The strengths of our study stem from its relatively large sample inclusive of a geographically diverse set of ICUs and our tackling of a topic for which current data are sparse. Our study has important limitations, however. First, the parent survey was potentially limited by generalizability (as responses from respondents accessed through professional organizations skewed toward academic centers), recall bias (as respondents were asked about conditions before the COVID-19 pandemic), and our lack of knowledge of the total number of ICUs in the United States and per hospital (which limited our ability to understand whether we comprehensively sampled all ICUs within a given hospital, for example).¹⁴  We were also unable to assess the specific roles and responsibilities of APPs and physicians-in-training in individual ICUs. Last, the association we identified between state-level scope of practice regulations and APP availability may remain confounded by unmeasured differences in states with and without restrictions and may be impacted by misclassification bias if state-level restrictions present in 2024 differ from those present at the time of the staffing reported in the survey. Moreover, our study design precludes an assessment of causality regarding whether state-level practice allowances for APPs drive the differences in employment of APPs in ICUs or whether such regulations may differently impact PAs and NPs.

Advanced practice providers are common in US adult ICUs, both with and without the availability of physicians-in-training. Nonmodifiable factors such as ICU or hospital size and hospital location differ between ICUs using different provider staffing models. We found that state-level regulations pertaining to APP scope of practice, which are modifiable, may be associated with APP availability in US adult ICUs. Further work is needed to understand whether such laws cause APPs to be deployed less frequently. In the postpandemic era of ICU workforce shortages and rising burnout,^31,32  any barriers to ensuring access to qualified ICU providers should be eliminated.

Work was performed at the University of Miami Miller School of Medicine.