The Critical Care Workforce:  A Study of the Supply and Demand for Critical Care Physicians

Chapter 3: Demand

The Physician Demand Model uses current patterns of health care utilization and delivery of care to project future demand for intensivist services under a baseline scenario that assumes that such patterns will continue into the future.  The baseline projections are then adjusted to account for other trends—in particular, the trends towards greater use of intensivists—to estimate the total level of intensivist services that the Nation will likely be willing and able to purchase at prevailing prices in the absence of intensivist supply constraints.  This adjustment to the baseline projections is in response to the growing proportion of ICU patients that are cared for by physicians trained in critical care.

Projections of demand are based on current utilization patterns of physician services and expected trends in U.S. demographics, insurance coverage, and patterns of care delivery.  These utilization patterns are expressed as physician-to-population ratios for each specialty and population segment defined by age, sex, metropolitan/non-metropolitan location, and insurance type.  The baseline ratios are established using 2000 data.  Thus, the three major components of the model are:

• Population projections by age, ^[42] sex, and metropolitan/non-metropolitan location;
• Projected insurance distribution by insurance type, age, sex, metropolitan/non-metropolitan location; and
• Detailed physician-to-population ratios.

These methods are similar to those used by the COMPACCS investigators.  All of the calculations can be used to express demand as physician-per-population ratios that reflect current utilization patterns and current patterns of care.

In 2000, for the U.S. population as a whole, there were approximately 254 active physicians (MDs and DOs) engaged primarily in patient care per 100,000 population. ^[43]  The aggregate estimates ranged from a low of 151 for the population age 0 to 17, to a high of 785 for the population age 75 and above.  The ratios vary substantially by medical specialty and by geographic area.  If the current utilization patterns remain stable, the overall aging of the population will contribute to faster growth, in percentage terms, for specialist services relative to the growth in demand for primary care services.

The U.S. Census Bureau projects a rapid increase in the elderly population beginning in 2010 when the leading edge of the baby boom generation approaches age 65 (Exhibit 12).  Between 2000 and 2020, the population under age 65 is expected to grow by about 10 percent, while the population age 65 and older is projected to grow by approximately 50 percent.

Exhibit 12. U.S. Population Growth: 2000 to 2020

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Source: Analysis of Bureau of Census population projections

Current Utilization of Critical Care Services

Critical care is generally delivered in the inpatient setting in an ICU, although it is delivered in emergency situations throughout the hospital.  ICUs may be further separated based on the type of patients treated (e.g., medical, surgical, burn units, etc.) and hospitals may have more than one such unit depending upon size, location, staffing, and other factors.

On average, patients admitted to the ICU are sicker than other patients.  The overall mortality rate in ICUs (12 percent to 17 percent) ^[44] is much greater than the overall hospital average (about 1.5 percent).  According to data from the American Hospital Association (AHA) Annual Survey, there were a total of 59,400 ICU beds within approximately 3,200 hospitals in 2000.  The average number of ICU beds for all acute hospitals, given that the facility has an ICU, is about 18.5 beds.  Some hospitals, though, have large and numerous ICUs with over 300 beds.

Medical and surgical intensive care units, as defined by the AHA, are, “staffed with specially trained nursing personnel and contain monitoring and specialized support equipment for patients who, because of shock, trauma, or other life-threatening conditions, require intensified, comprehensive observation and care.” ICUs account for more than 10 percent of all hospital beds and over 4.4 million individual patient admissions. ^[45]

However, the exact number of patient days (for all payers) in intensive care units is difficult to calculate accurately because these numbers are not reported on any single, audited, mandatory database.  As extracted from Medicare’s 2002 Healthcare Cost Report Information System file, there are an estimated 18 million days of ICU care every year, with slightly under 15 million of these days provided in medical and surgical ICUs, approximately 3 million days provided in coronary care units, and another 300,000 days provided in burn ICUs.

Physician Demand Model Projections

Critical care ICD-9 diagnosis codes, collected from the AHRQ 2001 National Inpatient Sample (NIS) of the Hospital Cost and Utilization Project (HCUP), were used to study patient utilization of critical care services.  Based on this analysis we estimated the number of critical care doctors per capita by age group (Exhibit 13).  As the elderly constitute a larger proportion of the U.S. population, this trend will substantially increase the demand for critical care services.

Exhibit 13. Intensivist Utilization by Age Group, 2000

These ratios are based upon the organization and delivery of critical care services in 2000-2001. One major determinant affecting the demand for physicians trained in critical care is the way in which such care is delivered and who delivers this care.  Using the above ratios, the expected demand for intensivists given current (2000) utilization patterns is shown in Exhibit 14.  This projection suggests that if demand grows only as a result of the growth and aging of the population, demand for intensivists will increase from about 1,880 in 2000 to 2,600 in 2020 (an increase of about 38 percent).  This estimate of demand is based upon historical utilization patterns of intensivist services—that is, less than one-third of patients in ICUs actually receive care from a specialist in critical care—and does not account for the growth in intensivist-directed critical care.

A simple way to estimate the changes in demand associated with increased use of intensivists is to calculate how many full-time equivalent intensivists are required to deliver care to critically ill patients if every patient were cared for by specialists in critical care.  The COMPACCS study found that critically ill patients require, on average, 45 minutes of intensivist time, per patient day in the ICU.  Because patients use approximately 18 million ICU days annually, if only two-thirds of patients were treated directly by an intensivist, 3,100 FTE intensivists would have been required to treat the number of ICU patients hospitalized in the year 2000—65 percent more than were available in the U.S. at that time.  This estimate assumes that pulmonologists will continue to provide their current share of critical care services. ^[46]  Under this scenario of “optimal utilization,” approximately 4,300 FTE intensivists would be required by 2020, representing an additional 129 percent above the supply available in 2000.  If every patient were seen by an intensivist, the shortfall would be even greater.

Exhibit 14. Projected Demand for Intensivists

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As is discussed in the following section, the current supply of intensivists is inadequate to care for critically ill patients and this shortage is likely to worsen given the growing demand for ICU care as well as the relatively slow growth in the supply of intensivists.