Theoretical and Scientific Foundations of Nursing

332 Unit Ill Shored Theories Used by Nurses

Theories and Models of Disease Causation On J J,w-to-Jay, moment-to-moment bJsi~, nur,e, in pr,Ktice me ..1m· one of.1 num - ber of i.:oncepb, principlc.:s, .md thee ,rie~ from biology .rnd public hcalch . Thc~e theo- ries .uc often rcl.m.:d to di~e.1se Gllls.uion .md progre~~ion. Thi.~ include~ pathogene~i~ .rnd infrcrion .1~ well .1, multiple epidcmiologic concept~ .rnd principk~ ( e.g., ri~k fac- tor, cxpo~ure, pren:ntiun l. Thi~ ~<.:ction pnl\·ide~ .1 re\'iew of a kw of these principles, theorie~, and model~ .md show~ hm, they .u-e med in nursing practice .rnd nursing re~carch.

Evolution of Theories of Disease Causation Di~c.1s..: rdl'.r~ to ,111~· condition that disturb~ the norm.1I functioning of Jn organi~m, whether it Jtfrcb ,lne org.111 or ~cn:rJI systems. The term 11.1~ J.lso been defined JS the failure of an orgJni~m tu re~pond or .1dapt to ir~ environment. The concept ]1.1~ dunged dr.mutically m·cr tbt: course of timt:, hm,·ev.:r, .rnd idc,1s ,1bout the c.rn~c of di~c,1~e ha\'C been influenced by the pre,·,1iling cultun: JnJ scientific thought.

In ,111cicnt times, di~e.1se ,,·,1~ frc:quently ,·icwcd ,1s .1 di,·ine intcn·ention or pun- i~hmcnt. Early hum.m bt:ings ,lttributcd di~t..·J~c~ ro th.: influence of demons orspirib,

Chapter 15 Theories From the Biomedical Sciences 333

.md magic w.1s J l.irg:e p.1rt of treatment .md prcn:ntion. A~ time passed, other inta- ,·entions or treJtment~, \uch .1s the u,e of plJnt l'XtrJct~, bcc.m1e more cornrnon.

As humans formed inro ,ocietie~ .rnd distinct cultur.11 g:rm1p,, two trends, or ,1ppro.11:hes, to medicine en>l\"ed. Sorcerer~ .rnd priests embnKed .1 nugico-rcligious Jpproach, whereJ~ early ph)·siciam ,md ~..:ientists dcYclopcJ an cmpirko-rJtional Jpproach. Th..: empirico-ratin11,1l .1pproach \\",1', based on expericn1.:e .md obsen·,nion and wa~ prJcticeJ .n first by pricsts but \\",1s ad.ipred by nonderkal physici.in~. J\lod- ern medicirn: Jrmc prim.uil~- from the empirico-rational ,1ppro.1,h J~ thc human body .rnd it~ functions bec.1me bcttn kno\\ 11 .md .1~ ~1..-ience led mcdic.1I practice .i,n~· from ,;uperstition .md tii..:us nn the spiritu,11 rc.11111 to indudc ~cicntitic pro- ct·,sc, .mJ rc:isoning:.

In rhe 17th century, \\'illi.1111 HJrn:~-, .111 English physkiJn .rnd ,111.itomist, demon- ~tr,ned the dynami.:~ of blood circulation ( DonJhue, 2011 ). Dct.1ilcd studies of the org:am, di~e.ises, and procc,~cs, \Uch ,1, ph~·siology .rnd respirJtion, qui..:kly followed, l°or1ducted b~· o:mino:nt physici.m, .ind ~c:irnri,ts uf the time. j\lcdical dcbatc~ focuso:d on mi nut,: tcJtures of tho: bod,· .md ho\\" to tre.n p.irtieular di~cl1scs. Philosophic~ .rnd thl'nrie~ do:,·dopcd th,n w...-rc l.,rgcly redul'.tionistic .md dcduc:tin:, focusing on .amt· .111J ctkct; tho: mcdic.11 modd 4uickl~ cnih·ed.

In tho: I.ntcr p.1rt of th,: 19th century, ~cicntists bcg:,m to unr.1,·cl the b.,~ic ..:,lllSC!>

of infrctiou~ Ji~e.ise. Modern medicin,: began with the .idn·nt of Pasteur\ Germ Theory, which po~itcd that a spl·citic mi..:roorg.rnism w.1~ c:ap.ibk of ,:.msing .111 infi:..: - tiom di~rasc ( Hbc:k & H,1\\'h, 2009 i. The focu~ on !>ing;lc-.1.gcnr or ~ing:lc-organism c.1u~e for di~e.1~c pcr~isred for .1 numb,:r of de...-adt:!> and re~ulto:J in multiple ,uccrs~I.'.'!> in both tr1..·.1ting .rnd prc\'cnring ..:ommunic.iblc diso:.1ses. Toda\', howe\'er, the prl.'.'- domin.mt general model of disea~c (;1U!>,1tion is multic:Jus.11. in\'oh·ing in\".l~i\'e Jg:ent!>, immune respon~e!>, genctirs, c,wironmo:nt, .md bcl1;1,·ior.

A number of theorie~ .rnd models de~aibc disr.,~e ,:,1m.uion and the propcrtics th.\t relate tn dbr.i~e processes .md prc\'ention. Sumc of tho: mmt frl.'.'quenth· cncoun- tacd models in nursing pra.ctice .md rl.'.'~e.1rch arc di~cw,sed in the follo\\'ing. sections.

Germ Theory and Principles of Infection Loui~ P.1~tl.'.'ur tir~t proposed the Germ Theory in 1858. He theori,:cd that .1 speritic oq;.mism (i.e., a germ) \\',ls ..:,1pablc of c.wsing ,Ill int~ctiou, disc;1sc ( K.1lisch & Kalisch, 2004 I. TodJy, this seems like a simple theory, but it i!> one th.it \\·.1, critical to rhc Je- ,·dopment of modern medic,1I care. It~ imp.i..:t has been phc110men,1l .md 11.1~ helped to radically rl.'.'du..:c the numba ofdl.'.'.1th~ from intc..:tion.

Overview At the beginning of the 2 ht cenrun·, theorie~ of inkction Ml.'.' mmt often ,1pplil.'.'d to pre,·cnt infrction ( e.g., pr,1cti..:i11g ~trict h.mdwa~hing, ck.msing; J. scr.lpl' .mJ .1ppl~•- ing: antibiotic ointml.'.'nt, or prophyl.1ctil·,11ly trl',lting .1 ~urgl.'.'n· dient with antibiotics) or to dc~cribl.'.' the pro..:e~s th.it ~cl·k~ to identii}', undastJnd, ,mJ 111.urnge infc..:tious di~C.lSl'!,. Thi~ process i11iti.1te~ thl..' seJn:h f<>r the cam.1ti,·e .1gem of Jn infection .rnd method( s I of tr.insmis!,inn. Once this l1.1~ been ,i,:comp[i~hed, the focus can ~hiti: to thc den~lopment ofwJy\ to prncnt Jnd treat thl' di~l.'.'J~l'.

One of the most dram,uic cxampks of rhi~ prcKl.'.'!,s w.1s the outbrc.ik of ,-\IDS. The ~~·ndrmne w;1s first identiticd by th...- Centa, for Diseasc Control .md Pren".ntion ( enc J in Sl·prcmher of l 982, but month!> pa~~ed bo:forl..' it \\',lS determined thJt the c.ius.iti\'c .1go:nt w.i~ .1 retro,·irus, Luer termed HH' ( Shi & Singh, 2015). E.irly in thl· process, c,·en before the ,·irw, \\'.\~ i~ol.lted. methods of tr.lll!,l11is~ion (e.g., sext1JI,

334 Unit Ill Shored Theories Used by Nurses

tr.msplacent.11, Yi.1 blood product~) m.:rc.: rccog;nizc.:d .md intcn tntion~ for pn:vt:ntion propost:d. Rc.::st:;1rch on treatmt:nt !1.1~ produc.:t:d sonu:what ~uc..:essful rt:~ults in n:c..:nt ~·ears .111d i~ ongoing.

Another c.:x.m1pk invol\'t:s bm inc spongiform encephalopathy ( BSE), or mad cow disease, and its relationship with Crcutztcldt- Jakob disease (CJD). It has b1:c:11 hy- pothesized that the causati,·e agent of BSE is J prim1, \\·hicl1 is not truly a germ, but .1 protein that is transmim:d through ingestion of contaminated meat; the principles of inkction, however, .ire similar t Se..:ker, HerYe, & Kt:e,·il, 2011 ). i\foch .1dditional work will be necessary ro ~uppnrr rhis thc.:ory and ro c.:nhance preventin: dforts. Ulti- mately, it is hoped that ctl-cctin: treatments for CJD ,,·ill be found.

L1stly, a more.: recent example rdates to Zika ,·irus intt:ction and severe birth dctl.'Cts-particularly microcephal)·- In this example, .111 outbreak of Zika virus infec- tion was i11iti;1lly re..:ognized in North(·.1stern Brazil in e.1.rly 2015 ( Schulcr-Facc.:ini ct al., 2016). B~- September of tlut ye.u, 35 c.1se~ of microl.'.ephaly \\'cre reported in ,1n:a~ affeaed by thc outbreak. This lead public health officials to dt:termine a "possible association" bctwern Zik:l ,·int.~ and the birth dete..:ts. This designation "·as subscquently changl'd to a ''causal" relationship following more derailed, in-depth rcvicw of the cvidcm:e ( CDC, 2016 ).

Application to Nursing Rcse:irch ~rudies use the Germ Theory to id.enti~- tht' c1uses ur :igcnr~ of intcction. For an inkl.·tion to o..:cur, the host must be su~l.'.eptible to the invJ.sive organism. Thi~ susceptibility mav be tcrmed risk. For example, a pcrson "·ho has experienced scverc burns is .lt higher risk of infection bcc.rnse one of thc first lines of ddcnse, the skin, is damaged. J\fany nursing .trticlcs that present practice g.uid.1:.·lines ,111d nursing research studies h.wc fo..:used on prewntion and 11u11;1gcmcnt ofinfrction as \\'ell as idcnti~•ing fa1.:tors that pla1.:e an individual at risk for developing intcctions. These studies and guiddinc.:s use prin..:ipks from the Germ Theory, .1Jthuugh this is rarely J.cknowledged.

Examples from recent literature that detail a~pects of nursing practice rcl.ucd to pn:- vcmion ofinkction indlllk intervrntions to promote hand hygiene ( Foote & El-Masri, 2016; Hohenberger, 2015; Kukanich, K.J.ur, Freeman, & Powell, 2013 ), g;uidclines for preYcntion of inti:ctions rehm:.d to mi nary catheters ( P. Johnson, l;ilman, Lintner, & Buckner, 2016; L. \Villiarm, 2016b ), :ind strntegie~ to prevent ,·emilator-associatcd pnl.·umoni:i in intensiw l.'.arc unit (ICU) patients ( Klompa~, 201 S ). Upsh;nv-Owens and B.1iley (2012 ) ;md Chun, Kim, J.nd Park (2015) de~..:ribcd etforts nurses c.rn u~c to prc,·ent rncthicillin-resistam Surphylococcw n11rc11s ( MRS:\) infi:ction in hospitals and primary care settings, rcspecti\'dy. With respect to the prc\'ious discussion ofZikJ \'irus, strategics to prevent infection .111d. 111.mage complications were presented by Coyle (2016) and L. VVilliarns (2016a).

The Epidemiologic Triangle The classi1.: epidemiologic modd, parti.:ularly uscful in rhe depiction of eommuni- 1.'.able d.isca~c, i~ the Epidemiologic Triangle I figm-e 15-1 ). This model is oltcn used to illustrate the intcrre!J.tionships among; thl.' thn~e essential component~ of host, agent, .111d environment with reg.1rd ro disease camation. A cha.ngc in any of rhe three compo nl.'nts can n:sult in the disease process. for ex.1mple, exposure ;lt s..:hnol (en\'ironment) ofa child who has not been immunized (host) to the measles virus , agent) will probably n:sult in a case of mc.1slcs.

Within the Epidemiologic Triangle, preYention of disease lies in a\'erting; cxpo· sure to the agent. enhancing the physil.'.al .1.ttributl.'S of the host to resist thc dise.1se,

Chapter 15 Theories From the Biomedical Sciences 335

Figure 15-1 Epidemiologic Triangle.

Susceptible person or host

Causative ·------------· Environment agent

and minimizing .my ern·irunmental fac.:tor~ th.1t might contribute to dbc.be dcn:lop- mcnt. Host, .1gcnt, and em·ironmental factor~ th.n afti:ct health can also inAucnc.:c progression of the di~cJsc prnccs:,. Hosr facrurs indudc .1gc, gc111..kr, race/ethnicity, marit.11 st.um , economic starus, stare of immunity, and liti:stylc factor~ (e.g., dicr, exercise patterns, hygien.:, occupation, ~cxu.il h.:.ilth ). i\gcnr factors indudc prCSL·nce or absence of biologic organism~ ( e.g., bacteria, ti.111gi, ,·iruscs ). c:xpo~urc to physi- c1l fiKtors ( c .g., r.1diation, c.:xtn::ml·-~ of temperature, noise), .md exposure to chem- ic1l .1genrs ( e.g., poison:,, .11lcrgens, ga~cs ). Last, environmenr.11 foctors in dude \UCh thing~ .1~ physical dcmenrs or properties (e.g., dimatc, :,c,1:,om, geology), biologic entities (e.g., .mimab, insects, food, drugs), or soci.11/cconomic consider.uions (e.g., f.1mily, public polic~·, occupation, culture) ( .i\L McEwen & Pulli~, 2009 ).

The Web of Causation To cxpl.iin disc,1:,c .rnd di:,ability camed by multiple.: factor~, i\llac,\lahun Jnd Pugh ( 1970) den'.lopcd the concept of '' Ch.1in of Caus.uion," larcr termed rhc "Web of Causation." Prior rn th.it time, it lud been obsc.:rn:d th,H chronic disc.1se:, (i.e., coro- nary .1rtcry disease and most types of c111cer) .m: nor artribut:iblc ro one or two factor~ or cau,ari,·e ,1gcnts. Rarher, they result from rhe intcrncrion of multiple.: f.ictor~.

Overview An example of the ,1pplication of the \Vcb of Causation to the dc\'dopment of cnronary heart disease is presenred in Figure 15·2. The \Vcb of C.1us.1tion c,111 .ilso be .1pplied tO many health-related thrcJ.tS and conditiom. The problem of tcc:11Jge pregnancy, for cxampk, is attributable to a compkx intcr,Ktion .11110ng ,1 number of c,n1sativc .md contributing factors, induding 1.tck of knmdcdge .ibout se:u1ality ,md prcgn.mcy pren:nrion, lack of easily ac1.:c:ssiblc.: contra1.:eption, peer pressure, lo,,· sdt:esteem, social pattern~ in which teen mother~ arc mon.: likely to he children of tet:11 mother~, use nf alcohol or othc:r drugs, .rnd so on. F.imily ,·iolence, ccKaine use, and gang mt:mbership arc examples of other rhreJts to he.11th .rnd well-being th.it c.rn be more Jccuratcly explained through ,1 model of multiple: c.1usations.

Recognition th:it mJ.ny health problem~ Juve multiple c.m~cs kadi. to the recng· nition tlut there .lrc rarely simple solutions tu rhe~e health problem~. \Vhen trying to m.rnagc rccn pregnanc~·, fur exJmpk, the ~olution is not .1s simple .is .iddressing a knowledge deticit reg:irding ~exuality .rnd contraception. M.rny ( if not most) teens .ue well informed .1bour contr.1ception J.nd the mechanics of how one ger~ prcgnJnt. and they srill fail to take;: pre,·enrive measures. To pre,·cnr heart di~casc in ,\11 indi,·idLtal Jt ri!-k, intu,·entions include hcalrl, educ.1tion addressing ,l number of .1re.1s, includ- ing smoking cessation, weight loss, d10kstcrol reduction, .rnd exercise. Likewise, to

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Figure 15-2 Web of Causation. !Adopted with permission from Friedman, G. D [ 1994] Primer of epidemiology [4th ed.] New York1 NY· McGraw+-HII.I

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Chapter 15 Theories From the Biomedical Sciences 337

prevent teen pregnancy, interventions should include health teaching on improving self-esteem, participating in role-playing exercises on how to say "no~" encouraging orientation toward the future, enhancing parental supervision, and providing recre- ational alternatives ( sports and other after-school activities), as well .is giving infor- mation on sexuality, the mechanics of reproduction, and methods of contraception.

Application to Nursing Nurses have dcvdopc:d interventions and proposed strategies to address complex health problems with multifactorial etiologies. For example, from a large-scale, litera- ture synthesis, Garcia-Fernandez, Agreda, Verdu, and Pancorbo-Hidalgo (2014) or- ganized risk factors for development of pressure ulcers among hospitalized individuals into a middle range theory. The risk factors included mobility, exposure to moisture/ incontinence, mental state, nutrition, activity, predisposing disease, age, temperature and medications.

In another study, N. L. Johnson, Giarelli, Lewis, and Rice (2013) provided an overview of the correlational fuctors that are believed to contribute to development of autism spectrum disorder (ASD). These were broadly grouped into environmental factors (e.g., exposure to high levels of pollutants., viral infection during pregnam .. ")', use of assisted reproductive therapies), and genetic factors (i.e., 14genetic susceptibil- ity" and w.de novo mutationsn [new, spontaneous mutations]). The researchers also described nursing implications including promotion of knowledge and skills to assess genetic risk, advocacy for families, and encouragement to asses~ for possible ASD in encounters with children.

In other works, Matthews and Moore (2013) examined the risk factors associ• ated with sudden unexplained infunt death (SUID)/sudden infant death syndrome (SIDS), and Phillippi and Roman ( 2013) reported on the factors that facilitated or hindered patient access to prenatal care. In theory-specific examples, Katemdahl., Burge, Ferrer, Becho, and Wood (2014) used the Web of Causation to describe the complex dynamics in violent familial relationships, and Siegel (2007) used the Web of Causation as the theoretical framework in her examination of the predictors of over- weight in children in sixth, seventh, and eighth grades.

Natural History of Disease The natural history of a disease reters to the progress of a disease process in an indi- vidual over time.

Overview In their classic: model, Leavell and Clark ( 1965) described two periods in the natural history of disease., prepathogenesis and pathogenesis. In this model, the prepathogen- esis stage occurs prior to interaction of the disease agent and human host when the individual is susceptible. For example, an adult male smokes, a teenage girl considers becoming sexually active, or a preschooler attends a party also attended by a sick child. After exposure or interaction, the period of prepathogenesis proceeds to early patho- genesis (i.e., alterations in lung tissue, pregnancy, chicken pox) and on through the disease course to resolution--either death, disability, or recovery (i.e., lung cancer, teen motherhood, immunity to chicken pox).

In addition to the description of the natural history of disease progression, Leavell and Clark ( 1965) aJso outlined three levels of prevention-primary prevention, second- ary prevention, and tertiary prevention-that correlate with the stages of disease pro- gression (Box 15-1 ). Each of the three levels of prevention is applied at the appropriate

338 Unit Ill Shared Theories Used by Nurses

Box 15-1 Levels of Prevention

Primary prevention: Activities that are directed at preventing a problem before it oc- curs. This includes altering susceptibility or reducing exposure for susceptible individ- uals in the period of prepathogenesis. Primary prevention consists of two categories: general health promoffon (e.g., good nutrition, adequate shelter, rest, exercise) and :specific protection (e.g., immunization, water purification). Secondary prevention: Eorly detection of and prompt intervention for o disease or health threat during the period of early pathogenesis. Screening for disease and prompt referral and treatment are secondary prevention. Tertiary prevention: Consists of limitation of disability and rehabilitotion during the period of advanced disease and convalescence, where the disease has occurred and resulted in a degree of damage.

stage of pathogenesis in an attempt to halt progression ( Figure 15-3 ). Thus, at the pri- mary prevention stage, interventions fucus on general health promotion aL1::ivities ( e.g., encouraging a healthfi.11 diet and promoting regular exercise) and efforts to prevent specific health problems ( e.g., vaccination, encouraging use of seatbelts and car seats, promoting oral hygiene).

Secondary prevention is concerned with early detection and would include any screening activity (e.g., mammography, cholesterol screening) and subsequent efforts to limit disease progression for those identified with a health condition ( e.g., taking statin medications, lumpectomy ,vith radiation/chemotherapy). Last, tertiary prevention in- volves efforts to enham:e rehabilitation and convalescence following advanced disease.

Application to Nursing Mw.:h ot nw-sing pra.,ticc focuses on efforts to prevent the pro~on of disease at the ear- liest period or phase using the appropriate levels of prevention. There are many examples of applying primary prevention strategies in practice. These include efforts to prevent poly- pharmacy among community-dwelling older adults ( Harvath, Llndauer, & Sexson, 2016 ); maternal morbidity and mortality (Logsdon, 2016); multidrug-resistant, gram-negative infection in surgical patients (Murphy, 2012); skin cancer in adults (Roebuck, Moran, Mac Donald, Shwner, & McCune, 2015 ); falls among older adults ( Morgan et al., 2017); and cardiovascular disease through use of statins ( Sherrod, Sherrod, & Cheek, 2015 ).

Excellent examples of nursing interventions targeted to secondary prevention arc also common in the nursing literature. Examples include a program to promote screening for perinatal depression among Special Supplemental Nutrition Program for Women, Infants, and Children (WlC) recipients (Fritz, 2015 ), discussion of the importance of screening for human papillomavirus (HPV)-related oral cancer (Katz, 2017), guidelines for depression screening among adolescents with diabetes (Dever, 2016), elder abuse screening (Stark., 2012), and community-based screening promo- tion to detect colorectal ,ancer (Weyl et al.,, 2015 ).

Tertiary prevention efforts include information to help nurses work to promote follow-up with recommendations among colorectal cancer survivors (Hawkins et aL, 2015 ), prevent complications of hemodialysis through promotion of exercise ( Hannan~ 20 l 6 ), and prevent tumor lysis syndrome among cancer patients ( Kaplow & Iyere, 2016 ).

Finally, Jones-Parker ( 2012) presented a detailed overview examining all three levels of prevention intended to assist nurse praL-titioners in preventing cardiovascular disease in HIV-positive patients, and Klemp (2015) outlined multilevel preventive strat· egies for nurses to address breast cancer prevention across the cancer care continuum.

- - - - .... - ... ... .... ... - -- The natural history of any disease of humans

Interrelations of agent. host, and environmental - Reaction of the host to the stimulus -- - factors - ......... _.,_ Early Discernible Advanced Production of stimulus pathogenesis early lesions disease Convalescence

..._ Prepathogenesis P_!triod .... .... Period of pathogenesis -- ---t ... ..- -- ... - -- Health promotion t

Health education Specific protection t t Good standard of nutrition Early diagnosis and t adjusted to developmental Use of specific prompt treatment Rehabilitation phases of life immunizations

Attention to personality Attention to personal Case-finding measures, Disability limitation Provision of hospital and development hygiene individual and mass community facilities for

Provision of adequate Use of environmental Screening surveys Adequate treatment to retraining and education

housing, recreation, and sanitation arrest the disease for maximum use of agreeable working Protection against

Selective examinations process and to prevent remaining capacities conditions Objectives: further complications Education of the public occupational hazards and sequelae Marriage counseling and To cure and prevent and industry to utilize sex education Protection from accidents Provision of facilities to the rehabilitated disease processes

Genetics Use of specific nutrients To prevent the spread of

limit disability and to As full employment as Periodic selective Protection from communicable diseases

prevent death possible examinations carcinogens Selective placement To prevent complications Avoidance of allergens and sequelae Work therapy in hospitals

To shorten period of f Use of sMltered colony ' disability • I

• • • Prirnary prevention Secondary prevention Tertiary prevention - - - ::. ::--- - ... - -

Levels of application of preventive measures -

Fi ure 15-3 Natural history of disease. !Adapted with permis$ion from Leavell, H R., & Clark, E.G. ( 1965) Preventive medicine lo, lhe doctot ,n his communily: An epidemiologic approach [p 18] New York. NY: McGraw-HIii.)

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