High altitude respiratory physiology.pptx

As the altitude increases above the sea level, the corresponding atmospheric pressure decreases.
The partial pressure of Oxygen also decreases.
The arterial Oxygen saturation levels also decrease with increase in the altitude.

1. High Altitude Health Effects Dr.Demet Demircioğlu

2. High Altitude International Society for Mountain Medicine: High altitude = 1,500–3,500 m Very high altitude = 3,500–5,500 m Extreme altitude = above 5,500 m

3. High Altitude Environment Air density – key factor for health related issues Air pressure (barometric) lessens as altitude increases As altitudes increases, less air above pressing down

4. Air Pressure - Altitude Less air pressure less dense air – “ thin air ” Air holds less molecules per area Individual gas’ pressure is less 3 important consequences : Lower number of oxygen molecules / area (less ppO2) Lower number of water molecules / area (lower humidity) Less and thinner air above to shield from harmful sun rays

5. High Altitude Environment Health Oxygen Lower air pressure – lower oxygen content in air Major effect for health Humidity Lower air pressure – lower water content in air Dehydration risk Sun less atmospheric protection from More UV ray exposure

6. UV Increases at Altitude

7. Water Vapor Decreases at Altitude

8. Oxygen and Health The Quick Tour Oxygen needed for production of ATP Key energy molecule of the body Made in every cell of the body - mitochondria Needed for function and even survival of cells/body Hypoxia – tissues don’t have enough O2 Can’t produce normal quantities of energy Body can produce ATP without O2 anaerobic metabolism or cellular anaerobic respiration 13 times less efficient

9. O2 - Air to Mitochondria – ATP The Quick Tour Lungs’ function – air (O2) to blood Red blood cell (RBC) – carries bulk of O2 in blood Circulatory system - carries O2 rich blood to tissues Mitochondria – uses O2 to manufacture ATP, the energy molecule

10. Oxygen from Air to Blood

11. O2 into blood, then into RBC, on to hemaglobin – normally > 97 % sat RBCs in vessel Hemaglobin molecule

12. O2 - Lung to Circulation to Tissue

13. O2 into Tissues, Cells, Mitochondria

14. O2 Facts rest O2 consumption – 250 ml / minute rest amount of O2 from blood – 25 % Healthy adult minute ventilation 5 – 8 l/min Vt 500 ml, 7 ml/ kg, RR 12 – 20 bpm VO2 max 45 ml/kg/minute VO2 max 3.5 l / minute

15. Problem with Altitude – Low 02

16. Hypoxemia and Altitude

17. Hypoxemia Hinge Points Oxygen Carrying Normal O2 sat > 97 94 % ppO2 blood - 70 Humans work to keep O2 at or above 90 % Below O2 content drops dramatically Hypoxia can occur – low energy production 80 % Cognitive dysfunction Other organ dysfunction Altitude O2 Sat 2000 m sat less than 94% 3500 m sat less than 90 % 5500 m sat less than 80 %

18. Oxygen Content – ppO2

19. Acclimatization Adjusting to Thin Air, Low Oxygen Begins 1500 m (5000 ft) to 2000 m (6500 ft) Intensity depends upon how high, how fast “hypoxic stress” Three phases Immed i a t e Intermediate (days) Long term (weeks to 2 mos)

20. Acclim a ti z a tion Immediate Lung increased respiratory rate increased tidal volume Pulmonary artery vasoconstriction - V/Q increase O2 in alveoli - blood Cardiovascular increased heart rate / contraction increased BP (10mm Hg)/ venous tone increase DO2 DO2 = CO x O2 content blood (hgb x %sat) CO = HR x stroke volume Cerebral Increase flow (up to 24 % at 4000 m) More O2 to highly O2 dependant brain Digestive Decreased appetite, digestion decreased energy demand for taxed body

21. Acclimatization I ntermediate - Days Kidney bicarbonate diuresis for acid base balance Hyperventilation causes blood alkalosis Kidney compensates Pulmonary Ventilation increase and V/Q matching continue for up to one week PHTN continues (mean 25 mmHg – mild) 2,3 DPG Molecule in RBC that allows Hgb to unload O2 easier into the tissues

22. Acclimatization L ong Term, Weeks – 2 mos Polycythemia Kidney puts out erythropoietin – stimulates bone marrow to make more RBCs Increased RBC mass More Hgb Increased muscle capillaries More DO2 to exercising muscles Increased myoglobin Muscle protein holds, stores O2 Mitochondria - aerobic Decrease number More efficient O2 use Increased anaerobic metabolism Outside mitochondia Increased efficiency Heart HR stays higher BP comes down

23. Adaptation G enerations Genetic selection of advantageous traits for altitude Three populations studied Andeans Above 4000 m (13,000 ft) Increased HGB Tibetans and Nepalese Above 4000 m (13,00 ft) Increased ventilation (breathing) Increased blood vessels, and circulatory performance Cellular energy – anaerobic and efficient Amhara people Ethiopia Above 3500 m (11,500 ft) Normal ventilation Normal blood vessels Cellular energy – anaerobic and efficient

24. Adaptation G enerations Adapted populations have a different set of genes (natural selection) that essentially, augment acclimatization U College London U of Colorado Mayo Different level of expression of hypoxia beneficial genes 2010 – Science and PNAS - multinational team, led by U College London, Hugh Montgomery Tibetans at 15,000 ft have a variant of EPAS1 gene (controls HIF-1) HIF = Hypoxia-Inducible Factor (discovered 1995)

25. Very Exciting HIF – Hypoxia Inducible Factor Discovered 1992 Hopkins team investigating erythropoeitin “transcription factor” Turns on hundreds of genes helpful to acclimatization All three populations of high altitude people have upregulated HIF pathway Genes turned on by altitude can help understand hypoxia tolerance and develop therapies Important in cardiac and pulmonary disease

26. What to Expect at Altitude N ormal Acclimatization Response Fatigue Common Lasts up to 48 hours Due to energy availability Mild S hortness of B reath Due to increased need for ventilation 2 – 4 days Mildly increased HR, BP Due to increased DO2 BP Up to a week (10 mmHg) HR stays up Increased diuresis Up to 4 days Poor performance Mental but especially physical Up to a week Weight loss Diuresis Decreased appetite Disturbed sleep Periodic breathing Due to need to hyperventilate, and subsequent alkalosis

27. USArmy Institute for Environmental Medicine 4,000 ft (1200 m) – physical performance 8,000 ft (2440 m) – cognitive performance 10,000 ft (3,050 m) - judgement

28. Physical performance After acclimatization (2 weeks) level of fitness performance depends upon altitude – 1% loss for every 100m above 1500 m 90 % at 2500 m (8,200 ft) 75 % AT 4000 m (13, 100 ft) 65 % AT 8000 m (26, 240 ft)

29. Altitude Sickness F ailure of Acclimatization Acute mountain Illness Sleep disordered breathing HAPE – high altitude pulmonary edema HACE – high altitude cerebral edema HARH – high altitude retinal hemaorrhage Chronic Mountain illness

30. AMI – Risk Above 2500 m (8200 ft) Cause: lung, cardiovacular, renal, energy stress Increased cerebral flow Symptoms Fatigue HA Light headedness Anorexia, nausea, vomiting Disturbed sleep No lab / Xray tests Timing / treatment 4 – 6 hours after arrival Worse after first night Resolves two days Treatment NSAIDs/tylenol Acetizolamide (48 – 72 hrs) Dexamethasone (48 – 72 hrs) If does not resolve descend If severe – oxygen 2 – 4 l/min

31. Nasal O2

32. Sleep Disordered Breathing Above 3500 m (11,500 ft) Periodic breathing Periods of rapid breathing during sleep Cycle between normal shallow ventilation of sleep, hyperventilation to maintain O2 sat Can disrupt deep sleep Frequent arousals Less time in REM – deep sleep Oxygen can help Resolves 2 – 3 days

33. HACE / HARH Above 4500 m (14,760 ft) HACE Cause Leak from cerebral blood vessels – brain swelling microhemorrhage Sxs Start 6 – 12 hrs Confusion Impaired motor fxn /gait Stupor to coma Tests MRI Treatment Descend ASAP Oxygen Hyperbaric oxygen dexamethasone HARH Similar to HACE Retinopathy microhemorrhage

34. Picture Brain Edema

35. Portable Hyperbaric Chamber

36. HAPE Above 4500 m (14,760 ft) Severe pulmonary Hypertension Some areas pulmonary vascular bed overperfused Blood vessel injury Fluid leak into lung Lung edema – water – Worsens gas exchange P a t h op h y siolo g y Cli n i c al 2 – 4 days after arrival SOB Cough Hemoptysis Dx Crackles Xray

37. PHTN

38. HAPE Treatment Oxygen Descent Hyperbaric chamber Positive Pressure Ventilation B – agonist inhalers Pulmonary vasodilators Nifedipine sildenafil

39. Chronic Mountain Illness Monge’s Disease A bove 3000 m (9,840 ft) Polycythemia Hgb > 20 Chronic PHTN SXs Poor mental function Poor organ function Total body edema T r e a tme n t descend

40. Risk of Altitude Sickness Risk by altitude – AMI - above 2500 m 20 %, above 4500 m 50 % Sleep disordered breathing 3500 m HAPE – above 4500 m 5 - 10 % slow ascent from 2000 m only 1 – 2 % HACE – above 4500 m 1 – 2 % HARH – above 4500 m 1 - 2 % Death zone – above 8000 m – acclimatization not possible, survival – hours, days max Adaptation – not above 6000 m , 19,700 ft – Everest- 8850 m, 29000 ft Base camp 5100 m (16, 728 ft) – 5400 m (17, 712 ft)

41. Risk of Altitude Sickness Risk by speed – Above 3000 m (9800 ft) No more than 500 m /day if low risk AMI No more than 350 m / day if high risk AMI Every two days rest for a day If ascend high quickly, acetazolamide and decadron Risk by time at altitude – length of hypoxic stress Pikes peak (4,270 m, 14,000 ft) – low rate Up to 4000m (13, 100 ft) hours Risk by sleeping altitude – Above 2750 m, 9,000 ft Associated with hypoxic episodes Hike high sleep low Pre acclimatization prior stay at altitude - lowers risk 4 days Within months Risk by history of AS – at risk if go above 2500 m (8200 ft)

42. Risk by Medical Illness C an’t Compensate for Low ppO2 Lung disease Cadiovascular disease CAD CHF Anemia – Hct < 30, Hgb < 10 Hemaglobinopathy Sickle cell, etc.; 2,3 GDP deficiency Sleep apnea

43. Recommendations G oing to Altitude – Above 2000 m People are highly variable in acclimatization Genetically determined (low PDP2 gene expression – intolerant of altitude) Not a function of fitness Older age (> 50) may be mildly protective against Altitude Sickness Women slightly higher risk Underlying diseases: Lung disease Heart disease

44. Risk Can’t asses with current technology Hypoxic exercise – not predictive Future gene array or hypoxic HIF levels For now: Altitude History of AS Underlying medical conditions

45. Recommendations If history of AMS / travel above 2500 m (8200 ft) ft – acetazolamide 24 hrs before, and for 48 hrs into stay 250 mg bid First night sleep at less than 9000 feet (2750 m) (ARC – UC) Rest for 2 – 4 days Vigorous exercise may prompt AMI Creating tissue hypoxia Gradual activity increase over week Signs of AMI – 500 - 1000 m descent

46. Recommendations Alcohol, sleeping pills, other respiratory depressants – avoid 2 days to one week Caffeine – do not cold turkey – a respiratory stimulant Avoid salty – increases BP No tobacco – CO impairs O2 transport Carbohydrates – best fuel for high altitude – Helps aerobic / anaerobic metabolism

47. Above 3500 m If rapid significant risk AS Acetazolamide Decadron prophylaxis O2

48. Altitude tolerance - common cardiovascular and pulmonary diseases Travel to altitudes above 2000 m inadvisable: Cardiovascular diseases Within 3 months of myocardial infarction, stroke, ICD implantation, thromboembolic event – within 3 weeks Unstable angina pectoris Before planned coronary interventions Heart failure, NYHA class >II Congenital cyanotic or severe acyanotic heart defect Pulmonary diseases Pulmonary arterial hypertension Severe or exacerbated COPD (GOLD stage III–IV) FEV1 <1 liter CO 2 retention Poorly controlled asthma

49. Travel to altitudes of 2000-3000 m permissible : Cardiac diseases asymptomatic or stable CAD (CCS I–II) Stress ECG normal up to 6 METs Normal performance capacity for age Blood pressure under good control No high-grade cardiac arrhythmia No concomitant illnesses affecting gas exchange Pulmonary diseases Stable COPD or asthma under medical treatment, with adequate reserve function for the planned activity For travel to altitudes above 3000 m: Evaluation by a specialist in altitude medicine and physiology ICD, implantable cardiac defribrillator; NYHA, New York Heart Association; COPD, chronic Obstructive pulmonary disease; GOLD, Global Initiative for Chronic Obstructive Lung Disease; FEV1, forced expiratory volume in 1 second; CHD, coronary heart disease; CCS, Canadian Cardiovascular Society; MET, metabolic equivalent of task

50. O2 requirement 2000 m (6500 ft) – 3000 m(9840 ft) O2 Sat greater than 95 % - OK O2 Sat less than 92 % - need O2 Between 92 – 95 % assesment If concurrent lung / heart disease – O2 Rule is 2 liters if no O2 2 liters / min If O2 2 liters / min above base - chronic lung disease

51. S AS 2000 m (6500 ft) Worse at altitude 1500 m – diamox 2500 m - O2 with CPAP

52. P r egn a ncy High altitude communities Lower birth weights, though developmentally OK Higher incidence of PIH, preeclampsia, eclampsia Physiology Between 2500 and 3000 m, in utero Hgb increases Recs – Up to between 2500 (8,200 ft) and 3000 (10,000 ft) safe

53. P edi a trics Younger children (less than 8 y.o.) progressively more at risk (up to 4 x) for hypoxia and altitude sickness Limited ability to compensate Teens twice the risk Recs Absolutely no child above 3500 m (11,500 ft) Young children not above 3000 m (10,000 ft) Teens acclimatization and great care above 3500 m (10,000 ft)

54. W a t er Dehydration At 6000 m or feet – loose twice as much water Water through skin and breathe Hypohydration – increases risk of AMS 1999 – Basnyat – AMS risk increases by 60 % Less than 3 Liters per day Hyperhydration – increases risk for AMS/HAPE/HACE 2009 – Richardson – increased risk Above 4500 m S ym p t o m s Lack of perspiration Overheating Headache Light headed Fatigue Dark (concentrated urine)

55. Temperature Drops 3.5 degree F for every 1000 ft Drops 6.5 degree C for every 1000 m Contributes to decreased humidity at altitude

56. Water Hydration Recs Usual daily fluid intake 8, 8 oz glasses water /day ½ body weight (lbs) in ozs Twice usual intake 3 – 5 Liters / day Key to start day, exercise hydrated O/N lose hydration Data is that most altitude hikers start hypohydrated 16 ozs to start Altitude exercise 8 ozs every 20 minutes

57. Sun UVB &UVA Altitude For every 1000 ft altitude 4 – 8 % more UVB exposure So at 8000 ft – more than 30 % more exposure Other effectors 85% increase from snow reflection 25% increase from white-water reflection 50 % increase from water reflection 80% of UV rays pass through cloud 20% from sand and grass reflection - and 40% when wet 15% reflection from concrete buildings 50% can be reflected into shaded areas 50% UVB and 80% UVA passes through the upper 50cm of water

58. UV Exposure Skin Adverse Effects Burn Aging Skin cancer R e c s Micro zinc oxide 5 % - only ingredient that blocks all of UVA and UVB SPF – 30 at least – Sun Protection Factor amount of UV radiation required to cause sunburn on skin with the sunscreen on, as a multiple of the amount required without the sunscreen how long one can stay in the sun If in water or sweating – water resistant If in sun more than 30 minutes Fresh screen

59. UV Exposure Eye Complications Acute Photokeratitis - corneal burn – snow blindness Photoconjunctivitis – conjunctival burn Chronic Pterygium – conjunctival growth Cataracts retinopathy Guidelines – eye wear 99-100% UV absorption Polycarbonate or CR-39 lens (lighter, more comfortable than glass) 5-10% visible light transmittance “glacier glasses” Large lenses that fit close to the face Wraparound or side shielded to prevent incidental light exposure If out more than 30 minutes

60. High Altitude Living – Healthy Colorado – Highest State J of Epi and Community Health - 2011 Colo – lowest death rate from cardiovascular disease Lower rate of HTN Colo – lowest death rate lung and colon CA J of Epi and Community Health – 2004 Greece - Lower rate of total and cardiovascular deaths at altitude Robert Wood Johnson foundation Lowest rate of obesity USA – Colorado – 19.8 % 7 / 10 counties in US with greatest longevity In Colorado – average altitude

61. High Altitude Living - Unhealthy J of Epi and Community Health - 2011 High rate of skin cancer Colo Colorado – always in top 10 states suicide rate Similar data from around the world Perry Menshaw U of Utah, Brain Institute – Altitude above 6000 ft is associated with suicide rates

62. Mechanisms CV health altitude good for blood vessels and circulation Vessel growth and plasticity Vit D (from sunlight) may protect against colon and other cancers COPDers (smokers) do not tolerate Colo Hypoxemia may promote anxiety / depression