Geriatric Rehabilitation 2013;3:13-17 Review Article 노화에따른호흡기능의변화 최원아 연세대학교의과대학재활의학교실및신경근육재활연구소 Changes of Pulmonary Function in the Elderly Won Ah Ch

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1 Review Article 노화에따른호흡기능의변화 최원아 연세대학교의과대학재활의학교실및신경근육재활연구소 Changes of Pulmonary Function in the Elderly Won Ah Choi, M.D. Department of Rehabilitation Medicine, Gangnam Severance Hospital, Rehabilitation Institute of Neuromuscular Disease, Yonsei University College of Medicine, Seoul , Korea Abstract Aging results in various changes in pulmonary function. The structural changes include reduced compliance of chest wall and lung parenchyma, which results in air-trapping, increased functional residual capacity and work of breathing. Respiratory muscle strength decreases with age and can impair effective cough, which is important for secretion clearance. Aging is associated with progressive decline in pulmonary function. Decreased sensitivity of hypoxia and hypercapnia with age leads to a diminished ventilator response, which can give rise to the ventilatory failure during high demand states (such as pneumonia, heart failure). Therefore understanding of these changes in an elderly patient is essential to the implementation of appropriate pulmonary rehabilitation. Key Words Elderly, Pulmonary function 접수일 : 2013년 6월 12일게재승인일 : 2013년 6월 14일교신저자 : 최원아주소 : 서울특별시강남구언주로 211 강남세브란스병원재활의학과 Tel : , 3698 Fax : reedlove37@yuhs.ac 서론 가스교환의변화등에대해논하고자한다. 폐는생애초기 20년동안성장및성숙하게되며이후서서히노화와함께그기능이감소하게되므로건강한노인도나이가들면서호흡기계의변화가나타날수있다. 1,2 노화로인한생리적변화중가장중요한것은폐의탄성반동 (elastic recoil) 의감소, 흉곽 (thorax) 의유순도 (compliance) 감소및호흡근의근력저하이다. 이로인해호흡기계의기능적변화가나타난다. 3 이에노화와연관된호흡기계의구조적인변화와이로인한역학적변화, 폐의방어기전의변화및 본론 1) 구조적인변화 (1) 흉곽의유순도감소 노화로인한늑골과늑골관절의석회화및척추추간판간의감소로흉곽의유순도는감소된다. 1,4 또한흉곽모양은골다공증으로인한척추압박골절로척추후만및흉곽전후경 13

2 (anteroposterior diameter) 증가를보이는종형흉곽 (barrel chest) 으로변화된다. 5 75세에서 93세사이노인 100명의흉부사진을분석한연구에서도 50도이상의심한후만을보인경우가 25%, 35도에서 50도정도의중증도후만을보인경우가 43% 였으며, 정상곡선을보인경우가 23% 로보고되었다. 6 이러한흉곽의변화는흉곽의유순도감소뿐아니라횡격막만곡의변형을가져오게되고이는횡격막의수축력 (force-generating capabilities) 감소를일으킨다. 3 24세부터 78세까지의 42명의건강한남성을대상으로한연구에서대상군간의폐의유순도는비슷하였으나젊은사람에비해노인에서흉곽유순도의감소가확인되었다. 또한흉곽유순도가낮은대상군에서잔기량 (residual volume, RV) 이높게측정되었다. 7 (2) 호흡근기능장애노화로인해주흡기근인횡격막의수축정도와근력의저하가발생하게된다. 척추후만증과흉곽의전후경증가는수축력장애의주요인자로작용한다. 또한, 흉곽의유순도감소및늑골의변형, 기능적잔기량 (functional residual capacity, FRC) 의증가는호흡근의기능장애를유발한다 (Fig. 1). 8 횡격막의근력은 transdiaphragmatic pressure (Pdi) 와최대흡기압 (maximum inspiratory pressure, MIP) 으로평가될수있는데, 건강한노인 (65세-75세) 과젊은성인 (19 세-28세 ) 의 Pdi의비교시노인에서 25% 적게측정되었으며, 65세부터 85세사이의남성에서최대흡기압은매년 0.8 에서 2.7 cmh 2 O 정도감소되었다. 9,10 이는노화로인한호흡근육의위축과선택적인속근섬유 (Type IIb) 감소에기인한다. 폐렴등호흡근에부담이증가할수있는호흡질환이노인에게발생시환기부전이나횡경막피로가생길수있게된다. 또한노인의호흡근근력은영양상태및말초근육의근력강도와도연관이있다. 11,12 노인에서의호흡근의기능장애는숨이찬증상부터저환기및운동지구력의감소로표출되며, 기침능력에영향을미치고심한경우호흡부전을야기할수있다. (3) 폐조직의탄력성소실폐의탄성반동압은정상적인노화에서매년 0.1에서 0.2 cmh 2 O로감소한다 (Fig. 2) 세경부터시작되는폐포관주변탄성섬유 (elastic fiber) 의균질한퇴행 (homogenous degeneration) 으로페포의크기는증가한다. 또한주변지지조직의감소로인해호기시작은기도 ( 2 mm) 의조기폐쇄가나타나충분한호기가이루어지지않게되어공기누적 (air Fig. 1. Evolution of lung volumes with aging. TLC: total lung capacity, VC: vital capacity, IRV: inspiratory reserve volume, ERV: expiratory reserve volume, FRC: functional residual capacity, RV: residual volume Fig. 2. Static elastic recoil as a function of age. Static elastic recoil was measured at 60% of total lung capacity (TLC). Shaded area shows ± 1 SD of plotted means. 14

3 최원아 : 노화에따른호흡기능의변화 trapping) 과과팽창 (hyperinflation) 을일으키고이는노인성폐기종 (senile emphysema) 으로귀결된다. 14 이는폐포벽의손상이동반되는진성폐기종과조직학적으로구분될수있다. 15 2) 폐기능변화폐는출생후 20년동안성장과성숙이일어나며, 그기능은 20대 ( 여성 : 20세, 남성 : 25세 ) 에최대치에이르고 20세에서 35세까지는거의변화없이꾸준하게유지된후감소하기시작한다 (Fig. 3). 1,2,16 노화로인하여흉곽의유순도가감소되며, 폐조직의탄성반동감소로인하여폐포크기가증가하며나타나는공기누적으로폐잔기량 (RV) 및기능적잔기량 (FRC) 이증가하게된다. 20대와 70대의비교에서잔기량과기능적잔기량은증가하고폐활량 (vital capacity, VC) 은감소하나총폐용량 (total lung capacity, TLC) 은변화없이유지된다 (Fig. 1). 8 이러한변화는호흡근에부담을가중시켜평상시호흡에사용되는에너지를증가시키게된다. 즉, 60세에서는 20세때보다호흡에필요한에너지가 20% 증가하게된다. 3 1초간노력성호기량 (forced expiratory volume in one second, FEV 1 ) 과노력성폐활량 (forced vital capacity, FVC) 은 20대 ( 여성 : 20세, 남성 : 27세 ) 까지증가하다가나이가들면서감소한다 (Fig. 4). 17 FEV 1 의매년감소되는정도는 25세에서 39세에는 20 ml, 65세이상에서는 38 ml씩감소한다. 18 1초간노력성호기량의노력성폐활량에대한비 (FEV 1 / FVC ) 는변화없이유지되다가여성의경우는 55세에서, 남성의경우는 60세이상에서 70% 에서 75% 정도로감소된다. 19 최대호기유량 (Peak flow rate) 은노화에따라감소한다. 호흡근의근력은최대정적압력의측정으로평가될수있으며, 기능적잔기량에최대한가깝게호기한후최대흡기압을, 총폐용적에최대한가깝게흡기한후최대호기압을측정한다. 4,443명의보행이가능한 65세이상의노인을대상으 : 로측정한최대흡기압및호기압결과에서노화에따른호흡근력의저하가관찰되었다. 12 또한, 노인에서는특히폐렴이나심부전등의호흡근에추가적인부담이생기는상황에서호흡근력의저하가관찰되었다. 4,20 3) 가스교환장애가스교환은폐포모세혈관막 (alveolar-capillary Fig. 3. Age-related decline in forced expiratory volume in one second (FEV 1 )% predicted plotted as % of maximal at age 20 years against age. Fig. 4. Evolution of forced expiratory volume in one second (FEV 1 : ); and forced vital capacity (FVC: ) as a function of age. Average of data from 746 subjects free of cardiorespiratory symptoms, who had never smoked. M: males, F: females 15

4 membrane) 을통한폐포환기 (alveolar ventilation), 폐포의관류 (perfusion) 와확산 (diffusion) 에의해이루어지며, 일산화탄소폐확산능 (diffusing capacity of carbon monoxide, DLCO) 으로평가될수있다. 이는노화에따라감소한다. 21 노화과정에서폐포의표면적이감소하고, 폐포의벽이얇아지며함유하는모세혈관의감소및폐순환의저하로환기 / 관류불균등은심해지게된다. 3,22 4) 방어기전의장애저산소증 (hypoxia) 이나고탄산혈증 (hypercapnia) 에대한환기반응이노인에서는현저히저하되어있다. 이는저산소증이나고탄산혈증시호흡근육으로전달되는원심성 (efferent) 신경반응의감소로설명된다. 23 노화로인해섬모의수와기능이감소하고, 흡인된입자들을제거하는대식세포의효율성도감소하게된다. 또한, 노인에서는기침반사가감소하고호흡근근력및흉곽의유순도감소로인한기침의효율성이감소하게된다. 이러한요소들로인해폐의감염에대한방어기전에장애가생긴다. 22 5) 운동능력의변화운동능력에대한노화의영향은매우다양해서개인의건강 (fitness) 과규칙적인신체활동에따라달라질수있다. 최대산소섭취량 (maximum oxygen consumption, VO 2 max) 은 20세에서 30세에최대로증가한후연간약 1% 씩감소하며, 신체활동정도에따라감소율이달라진다. 14 노인에서고탄산혈증에대한환기반응은휴식기에는감소되어있으나, 운동중에는젊은사람보다더증가하는것으로보고된다. 이는해부학적인사강이늘어난것에대한보상으로설명된다. 24 결론 노화에따른호흡기계의다양한변화로노인에서는호흡시일 (work) 의양이증가하며, 폐용적과유량의변화를가져온다. 또한, 방어기전의저하로폐렴등의호흡기계질환의유병률이증가하게된다. 따라서노인에서의호흡기계의변 화를정확히이해하고이를바탕으로적절한호흡재활에대한접근이필요하겠다. REFERENCES 1. Murray JF. Aging. In: Murray JF, editor. The Normal Lung. Philadelphia, PA: WB Saunders; 1986: Krumpe PE, Knudson RJ, Parsons G, Reiser K. The aging respiratory system. Clin Geriat Med 1985;1: Janssens JP, Pache JC, Nicod LP. Physiological changes in respiratory function associated with ageing. Eur Respir J 1999;13: Crapo RO. The aging lung. In: Mahler DA, editor. Pulmonary Disease in the Elderly Patient, Vol. 63. New York: Marcel Dekker; 1993; Gunby MC, Morley JE. Epidemiology of bone loss with aging. Clin Geriat Med 1994;10: Edge J, Millard F, Reid L. The radiographic appearance of the chest in persons of advanced age. Br J Radiol 1984;37: Mittman C, Edelman NH, Norris AH, Shock NW. Relationship between chest wall and pulmonary compliance with age. J Appl Physiol 1965;20: Crapo RO, Morris AH, Clayton PD, Nixon CR. Lung volumes in healthy nonsmoking adults. Bull Eur Physiopathol Respir 1982;18: Tolep K, Higgins N, Muza S, Criner G, Kelsen S. Comparison of diaphragm strength between healthy adult elderly and young men. Am J Respir Crit Care Med 1995;152: Enright, PL, Kronmal RA, Higgens M, Schenker M, Haponik EF. Spirometry reference values for women and men 65 to 85 years of age. Cardiovascular Health Study. Am Rev Respir Dis 1993;147: Arora NS, Rochester DF. Respiratory muscle strength and maximal voluntary ventilation in undernourished patients. Am Rev Respir Dis 1982;126: Enright PL, Kronmal RA, Manolio TA, Schenker 16

5 최원아 : 노화에따른호흡기능의변화 MB, Hyatt RE. Respiratory muscle strength in the elderly. Am J Respir Crit Care Med 1994;149: Turner J, Mead J, Wohl M. Elasticity of human lungs in relation to age. J Appl Physiol 1968;25: Sharma G, Goodwin J. Effect of aging on respiratory system physiology and immunology. Clin Interv Aging 2006;1: Verbeken E, Cauberghs M, Mertens I. The senile lung. Comparison with normal and emphysematous lungs. I: Structural aspects. Chest 1992;101: Ware JH, Dockery DW, Louis TA, Xu XP, Ferris BG Jr, Speizer FE. Longitudinal and cross-sectional estimates of pulmonary function decline in never-smoking adults. Am J Epidemiol 1990;132: Knudson RJ, Slatin RC, Lebowitz MD, Burrows B. The maximal expiratory flow - volume curve: normal standards, variability, effects of age. Am Rev Respir Dis 1976;113: Brandstetter RD, Kazemi H. Aging and the respiratory system. Med Clin N Am 1983;67: DuWayne Schmidt C, Dickman ML, Gardner RM, Brough FK. Spirometric standards for healthy elderly men and women: 532 subjects, ages 55 through 94 years. Am Rev Respir Dis 1973;108: Evans S, Watson L, Hawkins M, Cowley A, Johnston I, Kinnear W. Respiratory muscle strength in chronic heart failure. Thorax 1995;50: GueÂnard H, Marthan R. Pulmonary gas exchange in elderly subjects. Eur Respir J 1996;9: Kang SW. Pulmonary rehabilitation for patients with chronic obstructive pulmonary disease or elderly. The 11th Pulmonary Rehabilitation Workshop: 2013 Mar. 16; Seoul, Korea, Seoul: Sumondang, Peterson DD, Pack AI, Silage DA, Fishman APl. Effects of aging on ventilatory and occlusion pressure responses to hypoxia and hypercapnia. Am Rev Respir Dis 1981;124: Poulin MJ, Cunningham DA, Paterson DH, Rechnitzer PA, Ecclestone NA, Koval JJ. Ventilatory response to exercise in men and women 55 to 86 years of age. Am J Respir Crit Care Med 1994;149:

< Function of Respiration > 1) pulmonary ventilation 2) alveoli와 blood 사이에서산소와이산화탄소의 diffusion 3) blood와 body fluid에서산소와이산화탄소의운반 4) regulation of vent

< Function of Respiration > 1) pulmonary ventilation 2) alveoli와 blood 사이에서산소와이산화탄소의 diffusion 3) blood와 body fluid에서산소와이산화탄소의운반 4) regulation of vent 호흡생리 (Respiratory physiology) < 호흡 > 1) External respiration : lung에의해산소를흡수하고이산화탄소를배출시키는과정. 호흡생리에서다룸. 2) Internal respiration : 주위조직으로부터세포로산소의이동이일어나세포가산소를이용하고 이산화탄소를발생시키면세포로부터주위조직으로배출시키는과정. < Respiratory