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Z. Leon. Pittsburg State University.
Maximum breathing capacity (MBC) Maximum respiratory depth and rate +2 Normal +1 Abnormal 0 –1 10s Spirometer Paper feed C purchase vardenafil 20 mg on-line erectile dysfunction at age 21. Forced expired volume in first second (FEV1) Maximum expiratory rate +2 +1 Abnormal 0 Normal –1 1s Paper feed 1 Measurement 1 buy generic vardenafil 20mg online erectile dysfunction causes and remedies. Multiply- O2 diffuses about 1–2µm from alveolus to ing these volumes by the respiratory rate (f in bloodstream (diffusion distance). If,atagiventotalventi- long enough for the blood to equilibrate with lation (VE = VT! When f is doubled and VE T drops to one- blood enters the arterialized blood through. This extra-alveolar shunt as well as ventilation–per- Alveolar gas exchange can therefore decrease fusion inequality (! O2 consumption (VO2) is calculated as the The small pressure difference of about differencebetween. VO2 and VCO2 increase about tenfold cardiacoutput),thecontacttimefallstoathird during strenuous physical work (. Cases B2 and B3 lead to an increase in (100mmHg) and that of CO2 (PACO2) is about functional dead space (! The mean partial pres- B4 lead to inadequate arterialization of the sures in the “venous” blood of the pulmonary blood (alveolar shunt, i. Impairment of alveolar gas exchange Expiration CO2 Inspiration O2 1 Bronchial system Normal alveolar ventilation and perfusion Extra-alveolar shunt From pulmonary artery 4 Non-ventilated alveolus 2 Absent blood flow Alveolar shunt Functional dead space To 3 pulmonary veins Diffusion barrier 121 Despopoulos, Color Atlas of Physiology © 2003 Thieme All rights reserved. In this case, the PAO2 will fluctuate between Ventilation–Perfusion Ratio mixed venous PVO2 and PIO2 of (humidified). B, green line); PAO2 (PACO2) is flowtothelungs,isequaltothecardiacoutput therefore 17. These changes P decreases to about 12mmHg (Pprecap) in the are less pronounced during physical exercise. These values VA/Q imbalance decreases the efficiency of apply to the areas of the lung located at the the lungs for gas exchange. Due to the additive effect of hydrostatic pres- value, the relatively small Q fraction of zone 1. Near the olar–arterial O2 difference (AaDO2) exists (nor- apex of the lung, Pprecap decreases in vessels above mally about 1. Ppostcap), while the sharply, receptors in the alveoli emit local sig- area near the base of the lung (! A, zone 3) is con- nals that trigger constriction of the supplying tinuouslysuppliedwithblood(P. This throttles shunts in poorly Q per unit of lung volume therefore decreases from the apex of the lung to the base (! Life- decreases from the apex to the base of the lung threatening lung failure can quickly develop if (! The mean VA/Q for the entire fusion barrier, or surfactant disorder exists lung is 0. V /Q can A Despopoulos, Color Atlas of Physiology © 2003 Thieme All rights reserved. Regional blood flow in the lung (upright chest position) Alveolus Zone 1 PA> Pprecap> Ppostcap Pulmonary Pulmonary artery vein Zone 2 Pprecap> PA> Ppostcap Lung Zone 3 Pprecap> Ppostcap> PA Pprecap PA Ppostcap Perfusion Q · · B. Effect of ventilation-perfusion ratio (VA/Q) ventilation of lung on partial pressures in lung Pressures in kPa Ambient air: PO2= 20, PCO2= 0 VA/Q 0 3 Apex VA= 0 VA VA 2 VA Q PO2 = 5. Deoxygenated hemoglobin (Hb) can bycellsofthebodyundergoesphysicaldissolu- take up more H+ ions than oxygenated tion and diffuses into adjacent blood capillar- hemoglobin (Oxy-Hb) because Hb is a weaker ies. This promotes CO2 uptake in the dissolved,whiletherestischemicallyboundin peripheral circulation (Haldane effect) because form of HCO3– and carbamate residues of of the simultaneous liberation of O2 from ery- hemoglobin (! Since the PCO2 CO2 entering the pulmonary capillaries is re- in alveoli is lower than in venous blood, CO2 leased from the compounds (! HCO3– and Hb carbamate whereby H+ ions (re- The enzyme carbonic anhydrase (carbonate leased from Hb) are bound in both reactions dehydratase) catalyzes the reaction (! A7, A8), and the direction of HCO3–/Cl– ex- HCO3– + H+ CO2 + H O2 change reverses (! Because it acceler- toOxy-Hbinthelungpromotesthisprocessby ates the establishment of equilibrium, the increasing the supply of H+ ions (Haldane ef- short contact time (! CO2 distribution in blood (mmol/L blood, CO2 diffusing from the peripheral cells (!
A “cocktail” of therapies may need to be developed and tested to address these potential overlapping therapeutic windows discount vardenafil 20 mg amex xarelto erectile dysfunction. For example 20 mg vardenafil overnight delivery erectile dysfunction caused by anabolic steroids, the combination of a thrombolytic agent and a neuroprotectant may increase the chances of the latter drug reaching the site of injury within the required time window. For example, the admin- istration of insulin with the noncompetitive NMDA antagonist, dizocilpine, in dia- betic rats following ischemia resulted in additive neuroprotective effects. Hypoperfusion in the core and penumbra accounts for a greater proportion of the resulting injury than the subse- quent degradative processes that occur in the penumbral region. Other approaches include mechanical clot disruption and the use of suction devices, lasers, and ultrasound. In one study, the penumbral region accounted for 18% of the final infarct volume; the remaining 82% of the affected brain tissure was critically hypoperfused (70%) or sufficiently perfused (12%). MRI techniques such as diffusion–perfusion weighted imaging, MR spectroscopy, and CT perfusion may prove more useful in detecting salvageable brain as part of routine clinical practice. The combination of NMDA antagonists with AMPA or kainate receptor antagonists may confer protection to oligodendrocytes and GABAergic neurons with Ca2+-permeable AMPA receptors. For example, ifen- prodil acts on NR2B-containing NMDA receptors and they are expressed in greater proportions in the forebrain compared to the hindbrain. Calpains are also receiving attention because they are proteolytic enzymes acti- vated by calcium and may be potential targets for therapeutic agents. Calpain inhibitors including AK275, AK295, and MDL 28,170 are neuroprotective following ischemia in rats. The agents include superoxide dismutase, catalase, glutathione, iron chelators, vitamin E, alphaphenyl nitrogen (PBN), dimethylthiourea, oxypu- rinol, and tirilazad mesylate. They may act by reducing cytotoxic and vasogenic brain edema, aiding in Ca2+ homeostasis reestablishment, and antagonizing glutamate excitotoxicity. This leads to the activation of poly (ADP-ribose) polymerase (PARP), a repair enzyme that depletes cellular nicotinamide adenine dinucleotide (NAD+) and ATP. It has also been hypothesized that because PARP activation involves NAD+ that then depletes the metabolic pool of NADH, enhancing the pool of NAD+ may contribute to enhanced cell functioning. Several papers have suggested that direct nicotinamide treatment may be effective at replet- ing the pool of metabolic NADH and also facilitating the repair processes of PARP. FMK) that are not caspase selective and also block cathepsins reduce behav- ioral and cellular deficits as well as infarct volume following focal ischemia. For example, the combined administration of dextrorphan and cycloheximide reduced infarct volume following transient ischemia (MCAO) in rats by 87%, which was greater than the reduction resulting from the use of either agent alone (~65%). One consequence of zinc exposure is an increase in dihydroxy-acetone phosphate, a glycolytic intermediate, that in turn causes a decrease in neuronal ATP levels. It has been suggested that the administration of pyruvate, an energy substrate, can help ease the ATP loss. It has been postulated that the failure of calcium channel antag- onists may in part be due to perturbations in zinc levels following ischemic injury. The reduction of zinc release from nerve terminals may be accomplished by a dietary restriction of zinc. Astrocytes may be injured as a result of the release of inflammatory mediators following ischemic insult as well as zinc toxicity. For example, microvascular occlusion may be reduced by the inhibition of leukocyte adherence to blood vessels in the ischemic area. Other strategies include directing antibodies toward molecules such as intercel- lular adhesion molecule-1 (ICAM-1)99 and inhibiting the release of proinflam- matory cytokines from astrocytes and microglia such as interleukin-1β (IL-1β) or tumor necrosis factor-α (TNF-α). The use of statins and estrogens may also have the potential to reduce injury following ischemic insult through upregulation of endothelial nitric oxide synthase100 and antioxidant and trophic mechanisms,101 respectively. The use of growth factors may also be beneficial in treating ischemic injury and promoting functional recovery. Exogenous compounds such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophins 4/5 (NT-4/5), basic fibroblast growth factor, and insulin-like growth factor-1 (IGF-1) can all reduce injuries in rats subjected to cerebral ischemia. The inflammatory response is initiated and regulated by the complement system that consists of a number of cascades. The complement system causes injury in animal models of ischemia through the production of anaphylotoxins C3a and C5a and endothelial cell adhesion molecule upregulation. For example, soluble com- plement receptor-1 (sCR1), a strong inhibitor of complement activation, reduced neurological deficits and decreased platelet and polymorphonuclear leukocytes (PMN) accumulations following MCAO and reperfusion in mice. These include the c-Jun NH2-terminal kinases (JNKs), p38 kinases, and extracellular signal-regulated kinases (ERKs).
When the caecum is extraperitoneal it may be difficult to bring the appendix up into the incision; this is facilitated by first mobiliz- ing the caecum by incising the almost avascular peritoneum along its lateral and inferior borders buy discount vardenafil 10 mg on line erectile dysfunction medication with no side effects. The appendix mesentery discount vardenafil 20mg on line impotence due to diabetes, containing the appendicular vessels, is firmly tied and divided, the appendix base tied, the appendix removed and its stump invaginated into the caecum. It commences anterior to the third segment of the sacrum and ends at the level of the apex of the prostate or at the lower quarter of the vagina, where it leads into the anal canal. The rectum is straight in lower mammals (hence its name) but is curved in man to fit into the sacral hollow. Moreover, it presents a series of three lateral inflexions, capped by the valves of Houston, projecting left, right and left from above downwards. They must be visualized in carrying out a rectal examination, they provide the key to the local spread of rectal growths and they are important in operative removal of the rectum. Posteriorly lie sacrum and coccyx and the middle sacral artery, which are separated from it by extraperitoneal connective tissue containing the rectal vessels and lymphatics. The lower sacral nerves, emerging from the anterior sacral foramina, may be involved by growth spreading posteriorly from the rectum, resulting in severe sciatic pain. Anteriorly, the upper two-thirds of the rectum are covered by peri- toneum and relate to coils of small intestine which lie in the cul-de-sac of the pouch of Douglas between the rectum and the bladder or the uterus. In front of the lower one-third lie the prostate, bladder base and seminal 82 The abdomen and pelvis Sacral promontory Symphysis Seminal vesicle pubis Rectum Fascia of Prostate Denonvilliers Anal sphincter Fig. A layer of fascia (Denonvil- liers) separates the rectum from the anterior structures and forms the plane of dissection which must be sought after in excision of the rectum. The mid-anal canal repre- sents the junction between endoderm of the hind-gut and ectoderm of the The gastrointestinal tract 83 Fig. Acarcinoma of the upper anal canal is thus an adenocarci- noma, whereas that arising from the lower part is a squamous tumour. The two venous systems communicate and therefore form one of the anastomoses between the portal and systemic circulations. Acarcinoma of the rectum which invades the lower anal canal may thus metastasize to the groin nodes. This comprises: •the internal anal sphincter, of involuntary muscle, which continues above with the circular muscle coat of the rectum; •the external anal sphincter, of voluntary muscle, which surrounds the internal sphincter and which extends further downwards and curves medi- ally to occupy a position below and slightly lateral to the lower rounded edge of the internal sphincter, close to the skin of the anal orifice. The lower- 84 The abdomen and pelvis most, or subcutaneous, portion of the external sphincter is traversed by a fan-shaped expansion of the longitudinal muscle fibres of the anal canal which continue above with the longitudinal muscle of the rectal wall. In carrying out a digital rectal examination, the ring of muscle on which the flexed finger rests just over an inch from the anal margin is the anorectal ring. This represents the deep part of the external sphincter where this blends with the internal sphincter and levator ani, and demarcates the junc- tion between anal canal and rectum. The anal canal is related posteriorly to the fibrous tissue between it and the coccyx (anococcygeal body), laterally to the ischiorectal fossae con- taining fat, and anteriorly to the perineal body separating it from the bulb of the urethra in the male or the lower vagina in the female. Note that the ischiorectal fossa is now often referred to, more accurately, as the ischio- anal fossa—it relates to the anal canal rather than the rectum. Rectal examination The following structures can be palpated by the finger passed per rectum in the normal patient: 1both sexes — the anorectal ring (see above), coccyx and sacrum, ischiorectal fossae, ischial spines; 2male—prostate, rarely the healthy seminal vesicles; 3female—perineal body, cervix, occasionally the ovaries. Abnormalities which can be detected include: 1within the lumen—faecal impaction, foreign bodies; 2in the wall—rectal growths, strictures, granulomata, etc. During parturition, dilatation of the cervical os can be assessed by rectal examination since it can be felt quite easily through the rectal wall. Clinical features Haemorrhoids Haemorrhoids (piles) are dilatations of the superior rectal veins. Initially contained within the anal canal (1st degree), they gradually enlarge until they prolapse on defaecation (2nd degree) and finally remain prolapsed through the anal orifice (3rd degree). Anatomically, each pile comprises: a venous plexus draining into one of the superior rectal veins; terminal branches of the corresponding superior rectal artery; and a covering of anal canal mucosa and submucosa. Occasionally, abscesses lie in the pelvirectal space above levator ani, alongside the rectum and deep to the pelvic peritoneum. They are classified anatomically and may be: •submucous—confined to the tissues immediately below the anal mucosa; •subcutaneous—confined to the perianal skin; •low-level— passing through the lower part of the superficial sphincter (most common); •high-level—passing through the deeper part of the superficial sphincter; •anorectal—which has its track passing above the anorectal ring and which may or may not open into the rectum.
These are of smaller diameter (usually 8 French) and are more pliable and comfortable for the patient vardenafil 20mg with mastercard erectile dysfunction causes prostate. Weighted tips tend to travel into the duodenum purchase 20 mg vardenafil free shipping erectile dysfunction therapy treatment, which helps prevent regurgitation and aspiration. Most are supplied with stylets that facilitate positioning, especially if fluoroscopic guidance is needed. Always verify the position of the feeding tube with an x-ray prior to starting tube feeding. Commonly used tubes include the mercury-weighted varieties (Keogh tube, Duo-Tube, Dobbhoff, Entriflex), the tungsten-weighted (Vivonex tube), and the unweighted pediatric feeding tubes. Sengstaken–Blakemore tube:A triple-lumen tube used exclusively for the con- trol of bleeding esophageal varices by tamponade. One lumen is for gastric aspira- tion, one is for the gastric balloon, and the third is for the esophageal balloon. Other types of tubes used to control esophageal bleeding include the Linton and Minnesota tubes. Ewald tube:An orogastric tube used almost exclusively for gastric evacuation of blood or drug overdose. Dennis, Baker, Leonard tubes: These are used for intraoperative decompression of the bowel and are manually passed into the bowel at the time of laparotomy. Inform the patient of the nature of the procedure and encourage cooperation if the pa- tient is able. Maintain 13 gentle pressure that will allow the tube to pass into the nasopharynx. When the patient can feel the tube in the back of the throat, ask patient to swallow small amounts of water through a straw as you advance the tube 2–3 in. To be sure that the tube is in the stomach, aspirate gastric contents or blow air into the tube with a catheter-tipped syringe and listen over the stomach with your stethoscope for a “pop” or “gurgle. NG tubes are usually attached either to low wall suction (Salem-sump type tubes with a vent) or to intermittent suction (Levin type tubes). The latter allows the tube to fall away from the gastric wall between suction cycles. Feeding and pediatric feeding tubes in adults are more difficult to insert because they are more flexible. Feed- ing tubes are best placed into the duodenum or jejunum in order to decrease the risk of aspiration. Administering 10 mg of metoclopramide (Reglan) IV 10 min before inser- tion of the tube assists in placing the tube into the duodenum. As the tube is advanced, air can be injected to confirm progression of the tube to the right, toward the duodenum. If the sound of the air becomes fainter, the tube is probably curling in the stomach. Pass the tube until a slight resistance is felt, heralding the presence of the tip of the tube at the pylorus. Holding constant pressure and slowly injecting water through the tube is often rewarded with a “give,” which signifies passage through the pylorus. The duodenum usually provides constant resistance which will give with slow injection of water. Placing the patient in the right lateral decubitus position may help the tube enter the duodenum. Tape the tube securely in place but do not allow it to apply pressure to the ala of the nose. Patients have been disfigured because of ischemic necrosis of the nose caused by a poorly positioned NG tube. Complications • Inadvertent passage into the trachea may provoke coughing or gagging in the patient. HEELSTICK Indication • Frequently used to collect blood samples from infants 13 Materials • Alcohol swabs • Lancet • Capillary or caraway collection tubes • Clay tube sealer Technique 1. Although called a “heelstick,” any highly vascularized capillary bed can be used (fin- ger, ear lobe, or great toe). Auto- mated safety lancets (eg, BD Genie lancet for fingersticks and the BD Quick Heel Lancer for heelsticks) are also available.
