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Stockpile of personal protective equipment in hospital settings: Preparedness for influenza pandemics

Background Personal protective equipment (PPE) is known to be a crucial means of preventing influenza pandemics; however, the amount of PPE that should be stored in hospital settings has been unclear. Objectives The purpose of this paper is to propose a PPE calculation system to help hospitals to decide their PPE stockpile. Methods We searched influenza guidelines from a number of countries and research papers on protective devices and infectious diseases. The PPE calculation system included factors such as the influenza pandemic period, risk classification by health care workers (HCW) type, and the type and number of PPE for a HCW per day. Results We concluded that 4 sets of PPE (N95 respirators, double gloves, gowns, and goggles) per day should be prepared for HCWs in a high-risk group. Similarly, 2 sets of appropriate PPE, depending on the risk level, are required for medium- and low-risk groups. In addition, 2 surgical masks are required for every worker and inpatient and 1 for each outpatient. The PPE stockpile should be prepared to cover at least an 8-week pandemic. Conclusion Purchasing a PPE stockpile requires a sizable budget. The PPE calculation system in this paper will hopefully support hospitals in deciding their PPE stockpile.

Human life has often been threatened by influenza pandemics, such as the ''Spanish flu'' in 1918, ''Asian flu'' in 1957, and ''Hong Kong flu'' in 1968. Above all, the Spanish flu, which suddenly broke out in Western Europe during World War I, caused the worst damage: 40 million deaths and 600 million infected people all over the world and 380 thousand deaths and 23 million infected people in Japan. 1 No major influenza pandemic has occurred since the beginning of the 21st Century; however, a pandemic might be imminent because it is known that influenza pandemics usually repeat within 10 to 40 years, and 40 years have already passed since the last pandemic: ''Hong Kong flu.'' In addition, development of transportation such as commercial flights in recent years makes it easy for infections to spread over seas. Severe acute respiratory syndrome (SARS) in 2003 was a good example of this.
During the SARS period, another key factor occurred: many health care workers (HCWs) who cared for SARS patients in hospital settings became infected. For instance, the rate of infected HCWs of all patients was 19% in China, 22% in Hong Kong, 20% in Taiwan, 43% in Canada, and 41% in Singapore, respectively. 2 On the other hand, there were rare cases, such as a hospital in Vietnam, which succeeded in treating patients without infecting HCWs, even though Vietnam's national rate of infected HCWs was extremely high (58%). 3 According to a study of this hospital, one of the factors that contributed to protecting HCWs from secondary infection was the use of personal protective equipment (PPE), such as N95 respirators, surgical masks, and gloves.
Given the lessons from SARS, PPE is considered essential as an infection control measure. It should also be noted that a large number of PPE will be required in the short-term because it is estimated that the rate of infected people would be 25% of the total population during an influenza pandemic. 4 The key question is how many PPE each hospital setting actually needs to purchase. The purpose of this paper is to establish a calculation system to decide the appropriate PPE stockpile in each hospital setting based on factors such as the influenza pandemic period, risk classification by the HCW type, and the type and number of PPE required for HCWs per day. In addition, we investigated the average number for each HCW in hospital settings in Japan classified by the location and scale of hospitals so that PPE can be calculated from only the location and scale of hospitals. Finally, as an example, the stockpile of PPE needed for a sample hospital with 300 beds in Tokyo is shown using this system.

Data extraction
Based on the above data, we extracted various factors, such as the influenza pandemic period, the risk classification by the HCW type, and the type and number of PPE required for HCWs per day to calculate the stockpile of PPE in hospital settings.

PPE calculation system
We first obtained the average number of HCWs in hospital settings from the database of the Ministry of Health, Labor, and Welfare of Japan. We then developed a PPE calculation system, which can calculate the number of PPE from only the location and scale of the hospital. In this system, the stockpile of PPE is calculated by multiplying (1) the average number of HCWs determined automatically by the location and scale of the hospital, (2) the number of PPE sets required for HCWs per day, and (3) the length of the pandemic period.
As an example, the stockpile of PPE required for a sample hospital with 300 beds in Tokyo is shown using this PPE calculation system. The expenditure for PPE was calculated by multiplying the total stockpile of PPE by the average cost of PPE.

Influenza pandemic period
Based on the data obtained during the SARS epidemic in 2003, we calculated the pandemic period, assuming that it started from the day that the first patient was detected to the last day when a SARS-free declaration was issued by the country. As a result, the average duration was 122 days. The average was taken from the countries shown in Table 1, which included more than 100 patients. China was excluded because of the unhelpful actions of the government, such as concealment at the beginning of the SARS pandemic.  6-8 The Netherlands 10 3 mo (90 days) New Zealand 11 8 Norway 12 6 mo Republic of Korea 13 8 South Africa 14 8-12 Sweden 15 6-8 United States 16 6-8 However, the pandemic periods in each region may be shorter than 122 days, which is the national average. According to the US Department of Labor, 5 the pandemic period in each region is considered to be 12 weeks at maximum. In addition, the majority of guidelines of the countries that are introduced on WHO Web site 6 assume that the pandemic lasts 6 to 8 weeks ( Table 2). The Ministry of Health, Labor, and Welfare of Japan also supposes that a pandemic will last 8 weeks 4 ; therefore, a stockpile of PPE should be prepared to cover at least 8 weeks, although influenza pandemics could last longer with 2 or more waves.

Risk Classification of HCWs
The type of appropriate PPE for each HCW differs depending on the risk level. In this research, HCWs are classified into 3 groups: high risk, medium risk, and low risk (Table 3).     Type and number of PPE required for each HCW per day The type of PPE needed for each risk group is shown in Table 4. According to the US Department of Labor, 5 the number of PPE required for HCWs in a high-risk group is 4 sets per day. It is also considered that 2 sets of PPE are required for HCWs in medium-and low-risk groups because HCWs work around 12 hours a day and are required to change PPE every 6 hours during pandemics. 20 The number of gloves depends on how many patients HCWs can treat because gloves should be changed for each patient. We suppose that 20 pairs of gloves/doctor (high risk)/day will be required because 1 SARS report showed that 1 doctor can treat 5 to 10 patients per day from the view of infection control. 21 Furthermore, the use of masks by patients is also important to block virus transmission. The US Department of Labor indicates that 1 surgical mask per day is necessary for outpatients and 2 for inpatients. 5 All medical and nonmedical workers in the hospital, such as doctors, nurses, medical technologists, pharmacists, caregivers who provide critical care or spiritual care, respiratory therapists, reprocessors of reusable medical devices, and cafeteria workers, in addition to the family members and visitors, also require at least 2 surgical masks per day. The type and number of PPE required for each HCW per day are summarized in Table 5.

PPE calculation system
We developed a PPE calculation system based on the following factors: influenza pandemic period of 8 weeks, risk classification by the HCW type, and type and number of PPE required for HCW per day. This system made it possible to demonstrate (1) the average number for each HCW, (2) the required PPE stockpile, and (3) associated expenses from only the location and scale of each hospital. The allocation of doctors and nurses to each risk group is illustrated in Table 3. In this study, we allocated 1/16 of all doctors and nurses to the high-risk group, 3/16 to the medium-risk group, and remaining 3/4 to the low-risk group.
Finally, to give an example, we show the stockpile of PPE required for a sample hospital with 300 beds in Tokyo (Table 6). According to this system, the total number of PPE is 10,528 N95 respirators (with exhalation valve), 8848 N95 respirators, 122,192 surgical masks, 21,280 goggles and gowns, 34,832 aprons, and 172,480 pairs of gloves. The total expense for this hospital came to 55,342,000 yen (US $553, 420.00; $15100 yen).

CONCLUSION
In recent years, the government of Japan has appropriated an enormous budget for preventive measures against influenza pandemics, but the major part of this budget is used to stockpile Tamiflu and Relenza and to develop a vaccine. 22 Considering that $1 million worth of PPE was required in the first week alone at the beginning of the SARS outbreak in Toronto, 23 PPE is as important as infection control measures. It also should be noted that stockpiling a sufficient number of PPE could be a large financial burden on each hospital; however, this must occur before pandemics break out, which will result in a massive shortage of PPE.
Stockpiling PPE at each hospital is a matter of great urgency. The PPE calculation system in this paper will hopefully help to estimate the stockpile of PPE for each hospital. After all, appropriate use of PPE is an essential factor to prevent the transmission of virus. Therefore, the education to HCW should be properly conducted in addition to stockpiling PPE before the pandemic occurs.